U.S. patent application number 15/843936 was filed with the patent office on 2018-04-19 for fibrillated blend of lyocell low dp pulp.
This patent application is currently assigned to INTERNATIONAL PAPER COMPANY. The applicant listed for this patent is INTERNATIONAL PAPER COMPANY. Invention is credited to Andrew J. Dodd, Mengkui Luo, Noriko Suzuki, S. Ananda Weerawarna, John A. Westland.
Application Number | 20180105985 15/843936 |
Document ID | / |
Family ID | 43067565 |
Filed Date | 2018-04-19 |
United States Patent
Application |
20180105985 |
Kind Code |
A1 |
Westland; John A. ; et
al. |
April 19, 2018 |
FIBRILLATED BLEND OF LYOCELL LOW DP PULP
Abstract
A fibrillated blend of lyocell and cellulosic pulp having a
degree of polymerization of 200 to 1000 as measured by ASTM Test
1975-96, a method of making the blend and materials which
incorporate the blend.
Inventors: |
Westland; John A.; (Auburn,
WA) ; Dodd; Andrew J.; (Seattle, WA) ; Luo;
Mengkui; (Auburn, WA) ; Suzuki; Noriko;
(Seattle, WA) ; Weerawarna; S. Ananda; (Seattle,
WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL PAPER COMPANY |
Memphis |
TN |
US |
|
|
Assignee: |
INTERNATIONAL PAPER COMPANY
Memphis
TN
|
Family ID: |
43067565 |
Appl. No.: |
15/843936 |
Filed: |
December 15, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12466227 |
May 14, 2009 |
9845575 |
|
|
15843936 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H 17/25 20130101;
D21H 13/08 20130101; D21H 17/33 20130101; D21H 17/35 20130101; D21H
13/02 20130101; D21H 11/18 20130101 |
International
Class: |
D21H 17/33 20060101
D21H017/33; D21H 17/25 20060101 D21H017/25; D21H 17/35 20060101
D21H017/35 |
Claims
1. A fibrillated blend of lyocell and cellulosic pulp having a
degree of polymerization of 200 to 1000 as measured by ASTM Test
1975-96, wherein at least a portion of the lyocell fiber has a
length of 3 to 12 mm.
2. The blend of claim 1 wherein the lyocell is from 25 to 75 weight
percent of the blend.
3. The blend of claim 1 wherein at least one of the lyocell or the
cellulosic pulp contains lignin.
4. The blend of claim 1 wherein the blend is hydrophobic.
5. The blend of claim 1 wherein the blend has been treated with an
additive.
6. The blend of claim 5 wherein the additive is selected from
surfactants, dispersants, nanoclay, carbon black, silica and lignin
or lignin derivatives.
7. A material comprising a fibrillated blend of lyocell and
cellulosic pulp having a degree of polymerization of 200 to 1000 as
measured by ASTM Test 1975-96, wherein at least a portion of the
lyocell has a length of 3 to 12 mm.
8. The material of claim 7 wherein the lyocell is from 25 to 75
weight percent of the blend.
9. The material of claim 7 wherein at least one of the lyocell and
the cellulosic pulp contains lignin.
10. The material of claim 7 wherein the blend is hydrophobic.
11. The material of claim 7 wherein the blend has been treated with
an additive.
12. The material of claim 11 wherein the additive is selected from
surfactants, dispersants, nanoclay, carbon black, silica and lignin
or lignin derivatives.
13. The material of claim 7 further comprising polyvinyl alcohol,
cellulose ether, polyurethane, polylactic acid,
polystyrene-co-butyl acrylate, water soluble polymers, nonwoven,
adhesives, water borne coatings or a starch based materials
14. The material of claim 7 further comprising thermoplastic or
thermoset or gel materials.
15. The material of claim 7 further comprising elastomeric
materials or rubber.
16. A method of forming a fibrillated blend of lyocell and
cellulosic pulp having a degree of polymerization of 200 to 1000 as
measured by ASTM Test 1975-96, and wherein at least a portion of
the lyocell has a length of 3 to 12 mm comprising providing
cellulosic pulp having a degree of polymerization of 200 to 1000 as
measured by ASTM Test 1975-96, providing lyocell having a length of
3 to 12 mm, placing the lyocell and the cellulosic pulp in an
aqueous medium to provide an aqueous mixture, mixing the aqueous
mixture at an energy level of 0.5 to 500 kwh per ton of lyocell and
cellulosic pulp for 20 to 240 minutes.
17. The method of claim 16 wherein the mixing is at an energy level
0.5 to 100 kwh/ton of lyocell and cellulosic pulp.
18. The method of claim 16 wherein the mixing is at an energy level
0.5 to 10 kwh/ton of lyocell and cellulosic pulp.
19. The method of claim 16 wherein the lyocell and cellulosic pulp
are 0.5 to 5 weight percent of the aqueous mixture.
20. The method of claim 16 wherein the mixing is from 60 to 180
minutes.
Description
[0001] The field of this invention is a dispersible fibrillated
blend of lyocell and low DP cellulosic pulp, the method of making
the blend and uses of the blend.
[0002] It has been proposed to use fibrillated lyocell as a
reinforcing agent for various materials. Applicants have found,
however, that fibrillated lyocell by itself does not perform well
as a reinforcing agent. It does not disperse well and, therefore,
does not provide the required physical attributes such as
toughness. Fibrillated lyocell tends to agglomerate or bundle. This
makes it difficult to use as a reinforcement or as a filter medium
because it bundles together and does not disperse throughout the
material.
[0003] Applicants have found that a fibrillated blend of lyocell
and a cellulosic pulp having a low degree of polymerization (DP)
provides a material that does disperse, does filter well, and does
provide better modulus of elasticity and strength while maintaining
toughness. What physical attributes are provided and how much is
provided will depend on the material with which the fibrillated
blend of lyocell and low DP cellulosic pulp is combined.
[0004] In one embodiment the DP of the low DP pulp can be from 200
to 1000 as measured by ASTM Test 1975-96 which uses a Cuene
(cupriethylenediamine) solvent. In another embodiment the DP of the
low DP pulp can be from 300 to 850 as measured by ASTM Test
1975-96. In another embodiment the DP of the low DP pulp can be
from 400 to 750 as measured by ASTM Test 1975-96. Low DP pulp
includes pulp fines.
[0005] In one embodiment the blend can be from 25 to 75 percent by
weight lyocell with the remainder low DP pulp. In one embodiment
the lyocell can be 40 to 60 percent by weight lyocell with the
remainder low DP pulp. In one embodiment the lyocell can be 50
percent by weight with the remainder low DP pulp.
[0006] In one embodiment the lyocell has a length of 3 to 12 mm. In
one embodiment the lyocell has a length of 3 to 10 mm. In one
embodiment the lyocell has a length of 4 to 8 mm. In each of these
embodiments fibril of the fibrillated lyocell usually has a
diameter or width in the range of 30 to 800 nanometers to provide
an aspect ratio of greater than 100 to one million or more.
[0007] The low DP material breaks into fibrils, particles and fines
which are useful in dispersing the lyocell material.
[0008] The blend could be incorporated into various materials such
as rubber, polyvinyl alcohol, other elastomeric materials,
cellulose ethers, polyurethane, polylactic acid and latexes such as
polystyrene-co-butyl acrylate and in water soluble polymers. It
could be incorporated into materials in which biodegradability as
well as high maximum strength, modulus of elasticity and strength
to rupture are required. The blend could be incorporated into
adhesives to provide thermal creep. The blend could be used as a
rheological modifier in water borne coatings. The blend could also
be used in starch based materials.
[0009] The fact that this blend disperses is surprising because
applicants have found that a fibrillated blend of lyocell and a
pulp having a DP of 1100 or more as measured by ASTM Test 1975-96
does not perform well. It does not disperse well and does not
filter well. Applicants have also found that a low DP pulp, either
non-fibrillated or fibrillated, does not perform well. It does not
disperse well, does not filter well and does not provide the
required physical attributes.
[0010] Cellulose is normally fibrillated at high energy, increasing
the cost of production. It has been thought that high energy is
required for its production.
[0011] Applicants have found that in one embodiment the blend of
lyocell and low DP pulp can be fibrillated at an energy of less
than 500 kwh per ton of blend and perform well. Applicants have
found that in one embodiment the blend of lyocell and low DP pulp
can be fibrillated at an energy of less than 100 kwh per ton of
blend and perform well. Applicants have found that in one
embodiment the blend of lyocell and low DP pulp can be fibrillated
at an energy of less than 10 kwh per ton of blend and perform
well.
[0012] Starting Materials
[0013] Lyocell and low DP pulp have cellulose, and in some
instances hemicellulose and lignin as main constituents. The usual
starting materials for both lyocell and the low DP pulp include,
but are not limited to, trees, grass and recycled paper. The
starting materials, from whatever source, are initially converted
to a pulp. The pulp is a chemical wood pulp such as a kraft wood
pulp, which can be bleached, lightly bleached or unbleached. The
lightly bleached and unbleached pulp will contain lignin. The
pulping raw materials are sources of cellulose, hemicellulose and
lignin and the terms "wood" or "tree" will be used to generically
describe any source of cellulose, hemicellulose and lignin. In the
wood pulping industry, trees are conventionally classified as
either hardwood or softwood. Examples of softwood species from
which pulp useful as a starting material for both lyocell and low
DP pulp include, but are not limited to: fir such as Douglas fir
and Balsam fir, pine such as Eastern white pine and Loblolly pine,
spruce such as White spruce, larch such as Eastern larch, cedar,
and hemlock such as Eastern and Western hemlock. Examples of
hardwood species from which pulp useful as a starting material for
both lyocell and low DP pulp include, but are not limited to:
acacia, alder such as Red alder and European black alder, aspen
such as Quaking aspen, beech, birch, oak such as White oak, gum
trees such as eucalyptus and Sweetgum, poplar such as Balsam
poplar, Eastern cottonwood, Black cottonwood and Yellow poplar,
gmelina and maple such as Sugar maple, Red maple, Silver maple and
Bigleaf maple.
[0014] Wood from softwood or hardwood species generally includes
three major components: cellulose, hemicellulose and lignin.
Cellulose makes up about 50% of the woody structure of plants and
is an unbranched polymer of D-glucose monomers. Individual
cellulose polymer chains associate to form thicker microfibrils
which, in turn, associate to form fibrils which are arranged into
bundles. The bundles form fibers which are visible as components of
the plant cell wall when viewed at high magnification under a light
microscope or scanning electron microscope. Cellulose is highly
crystalline as a result of extensive intramolecular and
intermolecular hydrogen bonding.
[0015] The term hemicellulose refers to a heterogeneous group of
low molecular weight carbohydrate polymers that are associated with
cellulose in wood. Hemicelluloses are amorphous, branched polymers,
in contrast to cellulose which is a linear polymer. The principal,
simple sugars that combine to form hemicelluloses are: D-glucose,
D-xylose, D-mannose, L-arabinose, D-galactose, D-glucuronic acid
and D-galacturonic acid.
[0016] Lignin is a complex aromatic polymer and comprises about 20%
to 40% of wood where it occurs as an amorphous polymer. Lignins can
be grouped into three broad classes, including softwood or
coniferous (gymnosperm), hardwood (dicotyledonous angiosperm), and
grass or annual plant (monocotyledonous angiosperm) lignins.
Softwood lignins are often characterized as being derived from
coniferyl alcohol or guaiacylpropane
(4-hydroxy-3-methoxyphenylpropane) monomer. Hardwood lignins
contain polymers of 3,5-dimethoxy-4-hydroxyphenylpropane monomers
in addition to the guaiacylpropane monomers. The grass lignins
contain polymers of both of these monomers, plus
4-hydroxyphenylpropane monomers. Hardwood lignins are much more
heterogeneous in structure from species to species than the
softwood lignins when isolated by similar procedures.
[0017] Pulping Procedure
[0018] In the pulping industry, differences in the chemistry of the
principal components of wood are exploited in order to purify
cellulose. For example, heated water in the form of steam causes
the removal of acetyl groups from hemicellulose with a
corresponding decrease in pH due to the formation of acetic acid.
Acid hydrolysis of the carbohydrate components of wood then ensues,
with a lesser hydrolysis of lignin. Hemicelluloses are especially
susceptible to acid hydrolysis, and most can be degraded by an
initial steam, prehydrolysis step if one is used in the Kraft
pulping process, as will be described in the dissolving pulp
section, or in an acidic sulfite cooking process.
[0019] With respect to the reaction of wood with alkali solutions,
all components of wood are susceptible to degradation by strong
alkaline conditions. At the elevated temperature of 140.degree. C.
or greater that is typically utilized during Kraft wood pulping,
the hemicelluloses and lignin are preferentially degraded by dilute
alkaline solutions. Additionally, all components of wood can be
oxidized by bleaching agents such as chlorine, oxygen, ozone,
sodium hypochlorite and hydrogen peroxide.
[0020] Conventional pulping procedures, such as sulfite pulping or
alkaline pulping, can be used to provide a wood pulp useful both
for making lyocell fibers and for making a low DP pulp. An example
of a suitable alkaline pulping process is the kraft process,
without an acid prehydrolysis step. Normal kraft pulps are not
subject to acid prehydrolysis. By avoiding the acid pretreatment
step prior to alkaline pulping, the overall cost of producing the
pulped wood is reduced. A kraft pulping process with a
prehydrolysis step will be discussed under dissolving pulp.
[0021] A normal kraft wood pulp would have a hemicellulose content
of from 7% to about 30% by weight; and a lignin content of from 0%
to about 20% by weight. The lignin content will depend upon the
amount of bleaching. Percent by weight when applied to the
cellulose or hemiceliulose or lignin content of pulp means weight
percentage relative to the dry weight of the pulp.
[0022] The pulp may be subjected to bleaching by any conventional
bleaching process utilizing bleaching agents including, but not
limited to, chlorine, chlorine dioxide, oxygen, ozone, sodium
hypochlorite, peracids and hydrogen peroxide.
[0023] Lyocell
[0024] Regenerated cellulose fibers may be prepared using various
amine oxides or ionic liquids as solvents. In particular,
N-methylmorpholine-N-oxide (NMMO) with about 12% water present
proved to be a particularly useful solvent. The cellulose is
dissolved in the solvent under heated conditions, usually in the
range of 90.degree. C. to 130.degree. C., and extruded from a
multiplicity of fine apertured spinnerets into air. The filaments
of cellulose dope are continuously mechanically drawn in air by a
factor in the range of about three to ten times to cause molecular
orientation. They are then led into a nonsolvent, usually water, or
water/NMMO mixture to regenerate the cellulose. Other regeneration
solvents, such as lower aliphatic alcohols, have also been
suggested.
[0025] Other solvents that can be mixed with NMMO, or another
tertiary amine solvent, include dimethylsulfoxide (DMSO),
dimethylacetamide (DMAC), dimethylformamide (DMF) and caprolactan
derivatives. Ionic liquids or mixtures of ionic liquids and aprotic
or protic liquids are also suitable. Examples of the cation moiety
of ionic liquids are cations from the group consisting of cyclic
and acyclic cations. Cyclic cations include pyridinium,
imidazolium, and imidazole and acyclic cations include alkyl
quaternary ammonium and alkyl quaternary phosphorus cations.
Counter anions of the cation moiety are selected from the group
consisting of halogen, pseudohalogen and carboxylate. Carboxylates
include acetate, citrate, malate, maleate, formate, and oxylate and
halogens include chloride, bromide, zinc chloride/choline chloride,
3-methyl-N-butyl-pyridinium chloride and benzyldimethyl
(tetradecyl) ammonium chloride. Substituent groups, (i.e. R
groups), on the cations can be C.sub.1, C.sub.2, C.sub.3, and
C.sub.4; these can be saturated or unsaturated. Examples of
compounds which are ionic liquids include, but are not limited to,
1-ethyl-3-methyl imidazolium chloride, 1-ethyl-3-methyl imidazolium
acetate, 1-butyl-3-methyl imidazolium chloride, 1-allyl-3-methyl
imidazolium chloride. Pulps used for lyocell will usually fully
dissolve in NMMO or ionic liquid in 10 to 90 minutes. Shorter times
are preferred. The term "fully dissolve", when used in this
context, means that substantially no undissolved particles are seen
when a dope, formed by dissolving compositions of the present
invention in NMMO or ionic liquids, is viewed under a light
microscope at a magnification of 40.times. to 70.times..
[0026] Cellulose textile fibers spun from NMMO or ionic liquid
solution are referred to as lyocell fibers. Lyocell is an accepted
generic term for a fiber composed of cellulose precipitated from an
organic solution in which no substitution of hydroxyl groups takes
place and no chemical intermediates are formed. One lyocell product
produced by Lenzing AG is presently commercially available as
Tencel.RTM. fiber. These fibers are available in 0.9-5.7 denier
weights and heavier. Denier is the weight in grams of 9000 meters
of a fiber. Because of their fineness, yarns made from them produce
fabrics having extremely pleasing hands. The term "lyocell" in this
application includes polynosic fiber.
[0027] Two widely recognized problems of lyocell fabrics are caused
by fibrillation of the fibers under conditions of wet abrasion,
such as might result during laundering. Fibrillation tends to cause
"pilling"; i.e., entanglement of fibrils into small relatively
dense balls. It is also responsible for a "frosted" appearance in
dyed fabrics. Fibrillation is believed to be caused by the high
orientation and apparent poor lateral cohesion within the fibers.
There is an extensive technical and patent literature discussing
the problem and proposed solutions.
[0028] The lyocell can be made from a bleached or unbleached pulp
or a mixture of pulp and lignin. The pulp may be a traditional
dissolving pulp or a kraft pulp containing hemicellulose and having
a DP of 200 to 1100, and a hemicellulose content of 3 to 20% and
has been specially treated to be compatible with lyocell solvents
such as the amine oxides and ionic liquid and other solvents noted
above.
[0029] Pulps used for lyocell, including the specially treated
kraft pulp, have a number of attributes that allow then to be
compatible with the lyocell solvents, such as amine oxide and ionic
liquid and other solvents noted above. The lyocell pulps have a
copper number of less than about 2.0, and can have a copper number
less than about 0.7, as measured by Tappi T430 cm-99. The lyocell
pulps have a carbonyl content of less than about 120 .mu.mol/g and
a carboxyl content of less than about 120 .mu.mol/g. The carboxyl
and carbonyl group content are measured by TAPPI TM 237 or by means
of proprietary assays performed by Thuringisches Institut fur
Textil-und Kunstoff Forschunge, V., Breitscheidstr. 97, D-07407
Rudolstadt, Germany.
[0030] The lyocell pulps possess a low transition metal content.
Preferably, the total transition metal content is less than 20 ppm,
more preferably less than 5 ppm, as measured by Tappi 266 om-94.
The term "total transition metal content" refers to the combined
amounts, measured in units of parts per million (ppm), of nickel,
chromium, manganese, iron and copper. The lyocell pulps have an
iron content that is less than 4 ppm, more preferably less than 2
ppm, as measured by Tappi 266 om-94, and the copper content of pulp
used for lyocell is preferably less than 1.0 ppm, more preferably
less than 0.5 ppm, as measured by Tappi 266 om-94.
[0031] Additionally, lyocell fibers may have a natural crimp of
irregular amplitude and period that confers a natural appearance on
the fibers. The crimp amplitude may be greater than about one fiber
diameter and the crimp period is greater than about five fiber
diameters.
[0032] Processes for Forming Fibers
[0033] As described above, one process for forming lyocell fibers
is the dry jet/wet process. In this process the filaments exiting
the spinneret orifices are mechanically drawn through an air gap
and then submerged and coagulated and stretched mechanically in a
liquid bath before drying. Dried lyocell fiber can be cut to
different length from 2 to 12 mm. Never dried lyocell can be cut to
2 to 12 mm too and used directly for fibrillation.
[0034] Another process is generally termed "melt blowing". The
fibers are extruded through a series of small diameter orifices
into an air stream flowing generally parallel to the extruded
fibers. This draws or stretches the fibers. The stretching serves
two purposes. It causes some degree of longitudinal molecular
orientation and reduces the ultimate fiber diameter. Melt-blowing
typically produces fibers having a small diameter (most usually
less than 10 .mu.m) which are useful for producing non-woven
materials.
[0035] In one embodiment of the melt-blowing method, the dope is
transferred at somewhat elevated temperature to the spinning
apparatus by a pump or extruder at temperatures from 70.degree. C.
to 140.degree. C. Ultimately the dope is directed to an extrusion
head having a multiplicity of spinning orifices. The dope filaments
emerge into a relatively high velocity turbulent gas stream flowing
in a generally parallel direction to the path of the latent fibers.
As the dope is extruded through the orifices the liquid strands or
latent filaments are drawn (or significantly decreased in diameter
and increased in length) during their continued trajectory after
leaving the orifices. The turbulence induces a natural crimp and
some variability in ultimate fiber diameter both between fibers and
along the length of individual fibers. The crimp is irregular and
will have a peak to peak amplitude that is usually greater than
about one fiber diameter with a period usually greater than about
five fiber diameters. At some point in their trajectory the fibers
are contacted with a regenerating solution. Regenerating solutions
are nonsolvents such as water, lower aliphatic alcohols, or
mixtures of these. The NMMO used as the solvent can then be
recovered from the regenerating bath for reuse. Preferably the
regenerating solution is applied as a fine spray at some
predetermined distance below the extrusion head.
[0036] A somewhat similar process is called "spunbonding" where the
fiber is extruded into a tube and stretched by an air flow through
the tube caused by a vacuum at the distal end. In general,
spunbonded fibers are continuous while melt blown fibers are more
usually in discrete shorter lengths.
[0037] Another process, termed "centrifugal spinning", differs in
that the fiber is expelled from apertures in the sidewalls of a
rapidly spinning drum. The fibers are drawn somewhat by air
resistance as the drum rotates. However, there is not usually a
strong air stream present as in meltblowing.
[0038] Dissolving Grade Pulp
[0039] Most currently available lyocell fibers are produced from
high quality wood pulps that have been extensively processed to
remove non-cellulose components, especially hemicellulose. These
highly processed pulps are referred to as dissolving grade or high
alpha (or high .alpha.) pulps, where the term alpha (or .alpha.)
refers to the percentage of cellulose (Tappi, T 203 CM-99). Thus, a
high alpha pulp contains a high percentage of cellulose, and a
correspondingly low percentage of other components, especially
hemicellulose. The processing required to generate a high alpha
pulp and the fact that pulp yield is less because a high alpha pulp
contains less of the starting raw material significantly adds to
the cost of lyocell fibers and products manufactured from lyocell
fibers.
[0040] Dissolving grade pulps are traditionally produced by the
sulfite process but the kraft process can be used with certain
modifications.
[0041] When the kraft process is used to produce a pulp, a mixture
of sodium sulfide and sodium hydroxide is used to pulp the wood.
Conventional kraft processes stabilize residual hemicelluloses
against further alkaline attack, so it is not possible to obtain
acceptable quality dissolving pulps, i.e., high alpha pulps,
through subsequent treatment of kraft pulp in the bleaching stages
because the hemicellulose remains in the pulp. In order to prepare
dissolving type pulps by the kraft process, it is necessary to give
the raw material an acidic pretreatment before the alkaline pulping
stage. A significant amount of material primarily hemicellulose, on
the order of 10% or greater of the original wood substance, is
solubilized in this acid phase pretreatment and thus process yields
drop. Under the prehydrolysis conditions, the cellulose is largely
resistant to attack, but the residual hemicelluloses are degraded
to a much shorter chain length and can therefore be removed to a
large extent in the subsequent kraft cook by a variety of
hemicellulose hydrolysis reactions or by dissolution.
[0042] The prehydrolysis stage normally involves treatment of wood
at elevated temperature (150-180.degree. C.) with dilute mineral
acid (sulfuric or aqueous sulfur dioxide) or with water alone
requiring times up to 2 hours at the lower temperatures. In the
latter case, liberated acetic acid from certain of the naturally
occurring polysaccharides (predominantly the mannans in softwoods
and the xylan in hardwoods) lowers the pH below 4.
[0043] A non-dissolving kraft pulp may also be used for lyocell. It
has its degree of polymerization adjusted to 200 to 1100 and its
copper number and transition metals adjusted to be compatible with
the lyocell solvents. It will be described hereafter.
[0044] Degree of Polymerization
[0045] The term "degree of polymerization" (abbreviated as DP)
refers to the number of D-glucose monomers in a cellulose molecule.
Thus, the term "average degree of polymerization", or "average
D.P.", refers to the average number of D-glucose molecules per
cellulose polymer in a population of cellulose polymers.
[0046] The DP of a pulp will depend on the species of wood being
used. Hardwoods and softwoods will have different DPs. The DP of a
pulp will also depend on the pulping system and bleaching system
being used. A kraft paper pulp which retains hemicellulose will
have a higher DP than a kraft or some sulfite dissolving pulps
which has far less and usually no hemicellulose. Some dissolving
pulps can have a high DP.
[0047] The DP of a pulp will also depend of the method of measuring
it. The measurements of DP in this application are by ASTM Test
1975-96 which uses a Cuene (cupriethylenediamine) solvent. Other
tests use a Cuam (cuprammonium hydroxide) solvent or a LiCl/DMAc
(lithium chloride/dimethylacetamide) solvent. Klemme et al
Comprehensive Organic Chemistry, Vol. 1, Fundamentals and
analytical methods, Wiley-VCH 1998 report the following D.P. for
pulps using Cuam: Papergrade softwood pulp: greater than 1000,
dissolving grade softwood pulp: 300-1700, paper grade hardwood
pulp: greater than 1000, dissolving grade hardwood pulp:
300-1000.
[0048] Sixta Handbook of pulp, Vol. 2, Wiley-VCH 2006 lists pine
kraft pulp with ECF bleaching to have a DP.sub.v of 2207 measured
with a Cuene solvent and DP.sub.w 2827 and a DP.sub.n of 659
measured with LiCl/DMAc/cellulose solution using GPC procedure.
[0049] Sixta also shows the DP for different species, pulping
systems and bleaching systems. Sixta provide the following DP:
kraft pine with ECF (elemental chlorine free) bleaching has a Cuene
DP of 2207 and a Cuam DP of 2827, kraft spruce with TCF (total
chlorine free) bleaching has a Cuene 1648 and a Cuam DP of 2251,
eucalyptus kraft with ECF bleaching has a Cuene DP of 2355 and a
Cuam DP of 2847, beech sulfite pulp with ECF bleaching has a Cuene
DP of 2240 and a Cuam DP of 2636, spruce sulfite pulp with TCF
bleaching has a Cuene DP of 3074 and a Cuam DP of 3648, spruce
sulfite pulp with ECF bleaching has a Cuene DP of 2486 and a Cuam
DP of 3144, and beech sulfite pulping with TCF bleaching has a
Cuene DP of 3489 and a Cuam DP of 4050. It is noted that the Cuam
method has higher DPs than the Cuene method.
[0050] The DP distribution can be unimodal, i.e., the modal DP
value being the DP value that occurs most frequently within the
distribution, or multimodal, i.e., a distribution of cellulose DP
values that has several relative maxima. A multimodal, treated pulp
might be formed, for example, by mixing two or more unimodal,
treated pulps, each having a different modal DP value. The
distribution of cellulose DP values can be determined by GPC method
(Sixta Handbook of pulp, Vol. 2, Wiley-VCH 2006).
[0051] Lowering the Degree of Polymerization
[0052] There are methods for reducing the DP of a non-prehydrolyzed
kraft pulp to a DP in the range of 200 to 1000 or a DP in the range
of 300 to 850, or a DP in the range of 400 to 750. It may be done
without substantially reducing the hemicellulose content. The pulp
can be a bleached, semi-bleached or unbleached kraft softwood pulp.
Low DP saw dust pulp, lyocell pulp or viscose grade pulp can be
manufactured using these methods.
[0053] This D.P. reduction treatment occurs after the pulping
process and before, during or after the bleaching process, if a
bleaching step is utilized. This includes a portion of the D.P.
reduction step occurring at the same time as a portion of the
bleaching step. Preferably the bleaching step, if utilized, occurs
before treatment to reduce the average D.P. of the cellulose.
[0054] The methods of reducing the DP can include treating pulp
with acid, or an acid substitute, or a combination of acids and
acid substitutes, steam, alkaline chlorine dioxide, cellulase, the
combination of at least one transition metal and a peracid,
preferably peracetic acid, and the combination of ferrous sulfate
and hydrogen peroxide.
[0055] The following methods are illustrative.
[0056] A means of treating the pulp in order to reduce the average
D.P. of the cellulose without substantially reducing the
hemicellulose content is to treat the pulp with acid. Any acid can
be utilized, including, but not limited to: hydrochloric,
phosphoric, sulfuric, acetic and nitric acids, provided only that
the pH of the acidified solution can be controlled. Sulfuric acid
is used because it is a strong acid that does not cause a
significant corrosion problem when utilized in an industrial scale
process. Additionally, acid substitutes can be utilized instead of,
or in conjunction with, acids. An acid substitute is a compound
which forms an acid when dissolved in the solution containing the
pulp. Examples of acid substitutes include sulfur dioxide gas,
nitrogen dioxide gas, carbon dioxide gas and chlorine gas.
[0057] The acid, or combination of acids, is preferably utilized in
an amount of from about 0.1% w/w to about 10% w/w in its aqueous
solution, and the pulp is contacted with the acid for a period of
from about 2 minutes to about 5 hours at a temperature of from
about 20.degree. C. to about 180.degree. C. The amount of acid or
acid substitute will be sufficient to adjust the pH of the pulp to
a value within the range of from about 0.0 to about 5.0. The
amount, time, temperature and pH can be at a range within these
ranges. The rate at which D.P. reduction occurs can be increased by
increasing the temperature and/or pressure under which the acid
treatment is conducted. Preferably the pulp is stirred during acid
treatment, although stirring should not be vigorous.
[0058] When the reagent is steam, the steam is preferably utilized
at a temperature of from about 120.degree. C. to about 260.degree.
C., at a pressure of from about 150 psi to about 750 psi, and the
pulp is exposed to the steam for a period of from about 0.5 minutes
to about 10 minutes. The steam may include at least one acid. The
steam may include an amount of acid sufficient to reduce the pH of
the steam to a value within the range of from about 1.0 to about
4.5. The exposure of the pulp to both acid and steam permits the
use of lower pressure and temperature to reduce the average D.P. of
the cellulose compared to the use of steam alone.
[0059] When the reagent is a combination of at least one transition
metal and peracetic acid, the transition metal(s) is present at a
concentration of from about 5 ppm to about 50 ppm, the peracetic
acid is present at a concentration of from about 5 mmol per liter
to about 200 mmol per liter, and the pulp is contacted with the
combination for a period of from about 0.2 hours to about 3 hours
at a temperature of from about 40.degree. C. to about 100.degree.
C.
[0060] When the reagent is a combination of ferrous sulfate and
hydrogen peroxide, the ferrous sulfate is present at a
concentration of from about 0.1 M to about 0.6 M, the hydrogen
peroxide is present at a concentration of from about 0.1% v/v to
about 1.5% v/v, and the pulp is contacted with the combination for
a period of from about 10 minutes to about one hour at a pH of from
about 3.0 to about 5.0.
[0061] Yet other means of treating the pulp in order to reduce the
average D.P. of the cellulose, but without substantially reducing
the hemicellulose content, is to treat the pulp with alkaline
chlorine dioxide or with alkaline sodium hypochlorite, oxygen, or
ozone.
[0062] The hemicellulose content of the treated pulp, expressed as
a weight percentage, is from about 7% by weight to about 30% by
weight or a range within that range. As used herein, the term
"percent (or %) by weight" or "weight percentage", when applied to
the hemicellulose or lignin content of treated pulp, means weight
percentage relative to the dry weight of the treated pulp.
[0063] Hemicellulose and lignin content are measured by a sugar
content assay based on Tappi T249 cm-00 and lignin content in the
same sample was estimated from the solid residue after filtration
of sugar solution from hydrolyzed samples.
[0064] Copper Number
[0065] If a nonprehydrolyzed kraft pulp is used for lyocell then
its DP needs to be reduced as discussed above and it is further
treated to lower the copper number to a value of less than 2.0,
more preferably less than about 1.1, most preferably less than
about 0.7, as measured by Tappi T430 cm-99. A low copper number is
desirable because it is generally believed that a high copper
number causes cellulose degradation during and after dissolution.
The copper number is an empirical test used to measure the reducing
value of cellulose. The copper number is expressed in terms of the
number of milligrams of metallic copper which is reduced from
cupric hydroxide to cuprous oxide in alkaline medium by a specified
weight of cellulosic material. The copper number of the treated
pulp can be reduced, for example, by treating the pulp with sodium
borohydride or sodium hydroxide or by treating the pulp with one or
more bleaching agents including, but not limited to, sodium
hypochlorite, chlorine dioxide, peroxides (such as hydrogen
peroxide) and peracids (such as peracetic acid).
[0066] The copper number of the low DP pulp used in the blend with
lyocell fiber does not need a low copper number and need not be
treated to reduce the copper number. It can, however, have a
reduced copper number.
[0067] Fibrillated Blend of Lyocell and Low DP Pulp
[0068] Applicants have found that a fibrillated blend of lyocell
and a pulp having a low degree of polymerization (DP) provides a
material that does disperse, does filter well, and does provide
better modulus of elasticity, toughness and strength. What physical
attributes are provided and how much is provided will depend on the
material with which the lyocell/pulp blend is combined.
[0069] In one embodiment the DP of the low DP pulp can be from 200
to 1000 as measured by ASTM Test 1975-96 which uses a Cuene
(cupriethylenediamine) solvent. In another embodiment the DP of the
low DP pulp can be from 300 to 850 as measured by ASTM Test
1975-96. In another embodiment the DP of the low DP pulp can be
from 400 to 750 as measured by ASTM Test 1975-96.
[0070] In one embodiment the blend can be from 25 to 75 percent by
weight lyocell with the remainder low DP pulp. In one embodiment
the lyocell can be 40 to 60 percent by weight lyocell with the
remainder low DP pulp. In one embodiment the lyocell can be 50
percent by weight with the remainder low DP pulp.
[0071] In one embodiment the lyocell has a length of 3 to 12 mm. In
one embodiment the lyocell has a length of 3 to 10 mm. In one
embodiment the lyocell has a length of 4 to 8 mm. In each of these
embodiments fibril of the fibrillated lyocell usually has a
diameter or width in the range of 30 to 800 nanometers to provide
an aspect ratio of greater than 100 to one million or more.
[0072] The low DP material breaks into fibrils, particles and lines
which are useful in dispersing the lyocell material.
[0073] The blend is formed by fibrillating the lyocell and low DP
pulp together. In one embodiment the lyocell and low DP pulp may be
mixed in a disintegrator or hydropulper for from 20 to 240 minutes.
In another embodiment the lyocell and low DP pulp may be mixed in a
disintegrator or hydropulper for from 60 to 180 minutes. The
disintegrator operates at 2700 to 3300 rpm and the hydropulper at
around 500 to 900 rpm. The consistency of the blend in the mixer
will be from 0.5 to 5%. The consistency of the blend in the
disintegrator is around 1-2% and in the hydropulper 2-4% on a
weight basis. In one embodiment the energy required for
fibrillation would be from 0.5 to 500 kwh per ton of blend. In one
embodiment the energy required for fibrillation would be 0.5 to 100
kwh per ton of blend. In one embodiment the energy required would
be 0.5 to 10 kwh per ton of blend. The energy in the disintegrator
in one embodiment is from 160 to 190 kwh (kilowatt hours) per ton
of blend and in another embodiment from 170 to 180 kwh per ton of
blend and in one embodiment the energy of the hydropulper is less
than 50 kwh per ton of blend and in another embodiment the energy
in the hydropulper is from 0.5 to 25 kwh per ton of blend. The
consistency of the blend can be changed to a consistency of 0.05 to
50% and added to the material to be reinforced or filtered. The
fibrillated blend can be shipped in a water slurry at a consistency
of 1 to 80%.
[0074] It has been noted that the 3 to 12 mm lyocell fibrillates
while the shorter low DP fiber does not fibrillate significantly
but does form fines. This is not true of higher DP pulp which does
not form fines to the same extent as low DP pulp.
[0075] A low DP pulp/lyocell blend can have pulp fibers which have
fibrillation. It has been noted that the lyocell fiber has more
fibrillation in the blend than when fibrillated alone. Low DP
fibers have limited fibrillation when fibrillated alone and less
than when fibrillated in a blend with lyocell. High DP pulp in a
pulp/lyocell blend has less fibrillation when compared to low DP
pulp in a pulp/lyocell blend.
[0076] The blend could be incorporated into various materials such
as rubber, polyvinyl alcohol, other elastomeric materials,
cellulose ethers, polyurethane, polylactic acid and latexes such as
polystyrene-co-butyl acrylate and in water soluble polymers. It
could be incorporated into materials in which biodegradability as
well as high maximum strength, modulus of elasticity and strength
to rupture are required. The blend could be incorporated into
adhesives to provide thermal creep. The blend could be used as a
rheological modifier in water borne coatings. The blend could also
be used in starch based materials.
[0077] Fibrillated lyocell by itself does not disperse easily. It
tends to agglomerate. The tendency of the fibrils is to curve in on
themselves or to intertwine.
[0078] Applicant has discovered that combining fibrillated lyocell
with a low DP pulp having a DP of 200 to 1000, a material having
good dispersibility is created. Fibrillated lyocell with higher DP
pulp will not disperse as well as with the lower DP pulp.
Fibrillated lyocell with higher DP pulp will not have as good a
modulus of elasticity, toughness or strength as fibrillated lyocell
with low DP pulp.
[0079] There are ways of showing dispersibility.
[0080] One is showing the turbidity stability of the blend in water
using EPA method 180.1. In this test, the turbidity of slurry of
the blend in Nephelometric turbidity units was measured 10 to 30
times in half to one minute to check the variability. An easily
dispersible material will have a stable slurry. There will not be
great variability. There will not be clumps and empty spots in the
slurry. The standard deviation of the turbidity will be small.
[0081] Lyocell alone can have a standard deviation of 0.4 to 2.5. A
blend of fibrillated lyocell and low DP pulp which have been
fibrillated together can have a standard deviation of 0.1 to 0.3. A
blend of fibrillated lyocell and higher DP pulp which have been
fibrillated together can have a standard deviation of 0.5 to above
9.
[0082] Another method is to determine the time it takes to filter a
specified amount of water from a water/cement mix. The longer it
takes to filter the specified amount of water the better the
dispersion of the fiber. It takes about one and a half to two times
as long for fibrillated lyocell alone or a blend of fibrillated
lyocell and higher DP pulp which have been fibrillated together to
drain than a fibrillated low DP pulp. For example, if it takes
around one minute for the fibrillated low DP pulp to drain a
specified amount of water from the cement mixture then it will take
the fibrillated lyocell or the blend of fibrillated lyocell and
higher DP pulp to from a minute and half to two minutes to drain
the same amount of water.
[0083] It will take even longer for the blend of fibrillated
lyocell and low DP pulp which have been fibrillated together to
drain. It will take the blend of fibrillated lyocell and low DP
pulp from two and a half to three and a half times longer to drain
than the low DP pulp by itself. For example, if it takes the low DP
pulp by itself a minute to drain a specified amount of water then
it will take the blend from two and a half to three and a half
minutes to drain the same amount of water.
[0084] The faster drainage times shows that there is less material
throughout the water cement mix filtering the system. There are
open spots through which the water can drain quickly. The drainage
is slowed down when there is a uniform distribution of material
throughout the cement matrix.
[0085] Applicant as unsure why the low DP pulp provides better
dispersion. The properties of the fibers were checked with FQA
(Jeremy Meyers and Hiroki Nanko TAPPI Spring 2005 Technical
Conference, pages 1-8) to see if there was an attribute that might
cause the dispersion. Table 5 has a comparison of fiber
properties.
[0086] The viscosity as measured by Tappi T-230 of a low DP pulp is
from 20 to 50 centipoises while the viscosity of the higher DP
pulps is 70 centipoises and up. The Carboxyl groups of a low DP
pulp are 4.25 to 5.25 as compared to 3 to 3.5 for a higher DP pulp.
The number of fibers per gram of pulp is greater than 5.5 million
for a low DP pulp as compared to 4.5 to 5.3 million for a higher DP
pulp. The LWAFL (length weighted average fiber length) is under 2.3
mm for a low DP pulp as compared to greater than 2.4 to for a
higher DP pulp. The kink index for a low DP pulp is greater than 2
for a low DP pulp as compared to 1.8 or less for a high DP pulp.
The curl index for a low DP pulp is greater than 0.2 for a low DP
pulp as compared to 0.18 or lower for a higher DP pulp. The WWAFL
(weight weighted average fiber length) of a low DP pulp is less
than 3.2 mm as compared to 3.3 or higher for a higher DP pulp. The
LW fines [length weighted, under 0.2 mm] of a low DP pulp is
greater than 6% by weight as compared to less than 5.3% for a
higher DP pulp. Upon disintegration (Tappi T227 om-94), a low DP
pulp has much lower fiber length, higher population and much higher
fines than a higher DP pulp refined under same condition (Tables 2
and 6).
[0087] It may be that the additional fines aid in the dispersion
and entanglement reduction of the lyocell/low DP pulp blend. It may
be that one of the other differences account for the dispersion and
reduction in entanglement.
[0088] Additives
[0089] For many uses a hydrophobic fiber is needed. The fibrillated
blend may be treated with additives to allow better blending with
the materials such as rubber, thermoplastics, and other materials
with which it can be combined. Additives that can be used for
hydrophobicity are sizing agent such as AKD or ASA or a cationic
surfactant, a low level of substitution of cellulose acetate,
dispersant (like Hydropalat 1080), attaching a silane to cellulose,
reacting a monoamine with a hydrophobic end to the carboxyl groups
on cellulose
[0090] Lignin
[0091] Each of the fibrillated blends of lyocell and low DP pulp
can also be made hydrophobic by the use of lignin in the lyocell,
the low DP pulp or both. The starting material for the lyocell
would be a lightly bleached or unbleached pulp. The low DP pulp can
be unbleached or lightly bleached. The amount of lignin can be as
high as 90% of the weight of the lyocell or pulp or both by the
addition of lignin. Fiber (wood fiber or lyocell) with lignin is
more hydrophobic and can enhance bonding with hydrophobic polymers
like rubber.
EXAMPLES
[0092] In the following examples Weyerhaeuser Peach.RTM. pulp is
used as an example of a low DP pulp. Examples of high DP pulps are
Weyerhaeuser fluff pulps NB 416, FR 416, FR 516 and LV bleached. UB
unbleached pulp is an example of a low DP pulp containing lignin.
LV is a highly carboxylated pulp (30 meq/100 gram) using
Weyerhaeuser Longview pulp as starting pulp and the method
described in U.S. Pat. No. 6,524,348.
[0093] The following two examples show the manufacture of a
lyocell/low DP pulp blend using a low energy hydropulper and a high
energy disintegrator.
Example 1
Use of Hydropulper (90 Minutes)
[0094] A 2.75 wt % consistency solution with water (56.5 kg), 6 mm
lyocell fibers (0.91 kg at 92% solids), and never-dried Peach.RTM.
pulp (3.65 kg at 23% solids) was added to a 40 gallon lab
hydropulper. The hydropulper was turned on and ran for 90 minutes.
A "typical" hydropulper would run at about 700 rpm. The energy in
the hydropulper is 25 kwh per ton of blend. Dried Peach.RTM. can be
used too.
Example 2
Use of Disintegrator (90 and 180 Minutes)
[0095] A 1.2 wt % consistency solution with water (1.94 kg), 6 mm
long lyocell fibers (13.2 g at 92% solids), and never-dried
Peach.RTM. pulp (52.2 g at 23% solids) was added to a standard
British Disintegrator (Tappi T227 om-94). The Disintegrator was
turned on and ran at 3000 rpm for 90 and 180 minutes. The energy in
the disintegrator is 175 kwh per ton of blend. The pulps may be dry
or never dry. Dry wood pulps include fluff NB 416, FR 416,
Peach.RTM. pulp and unbleached pulp (UB). Table 1 shows that highly
fibrillated cellulose blend from 6 mm long lyocell and Peach.RTM.
pulp had lower freeness than lyocell/NB 416 or lyocell/FR 416
blends with the same lyocell/pulp blend ratio made under the same
refining condition. A highly fibrillated cellulose blend from 6 mm
long lyocell and unbleached pulp with DP of 760 and lignin content
of 1.9% also had low freeness. It is believed that low freeness
indicates more fines. Fines are particles having a size less than
250 microns.
TABLE-US-00001 TABLE 1 Freeness of cellulose pulp and lyocell fiber
blend with high fibrillation Freeness (CSF, ml) of the slurry
Composition Lyocell/ Lyocell/ Lyocell/pulp Lyocell/UB* Peach NB416
Lyocell/FR416 British Disintegrator (consistency: 1.2%, 90 minutes,
example 2) 0/100 696 >700 704 5/95 630 25/75 190 290 330 50/50
108 (6.68)** 68 (6.30)** 106 (7.32)** 94 75/25 44 58 58 95/5 49 55
54 100/0 36 (1.90)** British Disintegrator (consistency: 1.2%, 180
minutes, example 2) 50/50 0 22 0 (100% lyocell) Hydropulper
(consistency: 3%, 90 minutes, example 1) 50/50 38 75 *UB =
unbleached kraft pulp, **Hemicellulose (xylan and mannan).
Example 3
Properties of Refined Lyocell/Pulp Blend
[0096] This example shows that a refined Peach.RTM./lyocell blend
or a refined unbleached low DP pulp/lyocell blend will generate
more fines during refining than a refined high DP pulp/lyocell
blend as shown in Table 2. The high DP pulps are LV bleached and NB
416. The extra fines from pulp, higher population and shorter low
DP fibers in their blend with lyocell will enhance lyocell fibril
dispersion in the blend and reduce mechanical entanglement among
lyocell fibrils due to extra dilution and spacing among long
lyocell fibrils. The blend may contain from 25 to 75 weight %
lyocell and 75 to 25 weight percent low DP pulp. At high lyocell
content (95/5 lyocell/NB416), the blend may have higher fines, but
lower population than lyocell/Peach of same composition (table 2),
but this extra fines from lyocell/NB416 is possibly from
over-fibrillated lyocell fiber. This will not benefit the
utilization of lyocell fibrils for composite applications.
Lyocell/Peach with 95/5 ratio also had high fine than 75/25 ratio.
Again, fines from lyocell do not imply higher dispersion. High
lyocell ratio in blend will have high entanglement even it is high
fines. This indicated that a proper lyocell/pulp ratio is important
and only fines from pulp will benefit dispersion for these blends
with proper lyocell/pulp ratio.
[0097] In this example, lyocell alone or lyocell was combined with
the different pulps in the ratios shown and the blends were
fibrillated either in a British disintegrator or a hydropulper for
the times shown. The blends were in aqueous solution at the
consistencies disclosed in Example 1 for the hydropulper and
example 2 for the British disintegrator. The resulting material was
tested for the fiber properties shown.
TABLE-US-00002 TABLE 2 Properties of refined lyocell fiber or its
50/50 blend with pulp Lyocell (8 mm) Yes Yes Yes Yes Yes Pulp used
No LV NB416 UB Peach Pulp bleached yes yes no yes DP (fibrillated
blend) 589 1100* 1140 690 542 Fiber Properties FQA British
disintegrator (90 minutes, example 2) Fibers per gram, million 22.1
8.6 11.0 14.4 15.6 LWAFL, mm 2.26 2.18 2.48 2.13 2.12 Fiber
Coarseness, mg/100 m 11.3 20.8 16.2 14.4 15.7 Kink Index 2.29 1.4
2.4 2.5 3.1 Curl Index 0.35 0.19 0.38 0.39 0.42 WWAFL, mm 3.75 3.31
3.81 3.64 3.60 LW Fines, % 14.0 7.1 9.2 11.0 11.9 Fiber Properties
FQA Hydropulper (90 minute, example 1) Fibers per gram, million
LWAFL, mm 2.22 1.45 Fiber Coarseness, mg/100 m Kink Index 2.22 2.26
Curl Index 0.24 0.28 WWAFL, mm 3.43 2.96 LW Fines, % 9.2 22.6
Properties of refined lyocell fiber blend with pulp Lyocell
(L)/Pulp L/NB416 L/Peach .RTM. L/Peach .RTM. L/Peach .RTM. L/Peach
.RTM. ratio 95/5 95/5 75/25 50/50 25/75 Fiber Properties FQA 90
minutes refining(example 2) Fibers per gram, million 13.4 17.3 19.9
15.6 16.7 LWAFL, mm 2.55 2.68 2.23 2.12 2.02 Fiber Coarseness,
mg/100 m 12.7 12.8 11.8 15.7 15.5 Kink index 3.3 3.3 3.3 3.1 2.8
Curl Index 0.56 0.59 0.54 0.42 0.33 WWAFL, mm 4.19 4.19 3.74 3.60
3.19 LW Fines, % 13.8 12.9 11.7 11.9 11.0 LV is a paper grade pulp
from Longview pulp mill Weyerhaeuser with 30 meq/100 gram of
carboxyl groups. *estimated DP is 1100.
Example 4
Suspension Stability of Refined Lyocell/Pulp Blend
[0098] One method of showing dispersion is showing the turbidity
stability of the blend in water using EPA method 180.1. The
following table gives a comparison among fibrillated lyocell, a
blend of fibrillated lyocell and Peach.RTM. pulp having a DP of
700, and a blend of fibrillated lyocell and NB 416 pulp having a DP
of 1500.
TABLE-US-00003 TABLE 3 Turbidity (11 reading in half minute) of the
suspension in water (0.003%) Lyocell/NB Sample Lyocell
Lyocell/Peach .RTM. 416 Blend 50/50 50/50 Standard deviation
(STDEV) 2.25 0.29 8.56
[0099] In this test for slurry stability, half minute time is used
to record turbidity of the slurry. Stable slurry will have low
turbidity variability (lower standard deviation). The stability of
the lyocell/low DP blend has far greater stability than the lyocell
alone or the lyocell and higher DP pulp.
[0100] The following table provides more suspension stability data
for other samples. As can be seen, suspension from
Lyocell/Peach.RTM. blend at 50/50 ratio still has the highest
suspension stability (the lowest standard deviation).
[0101] It is known that charged nanocellulose surface improves
nanocellulose dispersion but a blend of lyocell with high carboxyl
group pulp with high DP (the LV fiber) did not show good stability
(a high standard deviation). This may be the result of a poor
generation of fines
TABLE-US-00004 TABLE 4 Turbidity (25 reading in one minute) of the
suspension in water (0.003%) Lyocell/Pulp 50/50 50/50 50/50 50/50
Pulp Peach .RTM. FR416 LV Peach .RTM. additive no no no no STDEV
0.26 0.58 0.84 0.13
[0102] Another method is to determine the time it takes to filter a
specified amount of water from a water/cement mix. The longer it
takes to filter the specified amount of water the better the
dispersion of the fiber. The three materials used in the first test
as well as a low DP pulp sample were used. The filtration times in
seconds were: low DP pulp alone, 55 seconds; lyocell alone 101
seconds; lyocell/high DP (1500 DP) 50/50 blend 103 seconds; and
lyocell/low DP (700 DP) 50/50 blend 178 seconds. Again the low DP
blend showed better dispersion.
[0103] Applicant is unsure why the low DP pulp provides better
dispersion. The properties of the fibers were checked with FQA
(Jeremy Meyers and Hiroki Nanko TAPPI Spring 2005 Technical
Conference, pages 1-8) to see if there was an attribute that might
cause the dispersion. Table 5 has a comparison of fiber
properties.
TABLE-US-00005 TABLE 5 Fiber properties FR 416 FR 516 NB 416 Peach
.RTM. Fluff Fluff fluff Chemical Properties Viscosity, mPa * s 22
78 70 224 DP 700 1148 1110 1498 R-10, % 81.5 86.9 86.6 87.5 R-18, %
85.7 87.4 87.2 87.8 Carboxyl group, meq/100 g 4.65 3.3 Fiber
Properties FQA Fibers per gram, million 5.7 4.9 5.2 4.6 LWAFL, mm
2.24 2.55 2.44 2.67 Fiber Coarseness, mg/100 m 20.8 21.2 20.3 21
Kink Index 2.2 1.8 1.7 1.4 Curl Index 0.22 0.18 0.18 0.14 WWAFL, mm
3.13 3.44 3.31 3.4 LW Fines, % 6.2 5.2 5.3 4.4
[0104] It can be seen that the viscosity (Tappi T-230) and DP of
Peach.RTM. pulp are lower than the others. The R-10 and R-18 (Tappi
T-235 cm-00) of Peach.RTM. pulp are slightly lower than the others.
The Carboxyl groups of Peach.RTM. pulp are higher than NB 416. The
number of fibers per gram of Peach.RTM. pulp is higher than the
others. The LWAFL (length weighted average fiber length) of
Peach.RTM. pulp is lower than the others. The kink and curl index
of Peach.RTM. pulp are higher than the others. The WWAFL (weight
weighted average fiber length) of Peach.RTM. pulp is lower than the
others and the LW fines [length weighted, under 0.2 mm] of
Peach.RTM. pulp is higher than the others. Upon disintegration
(Tappi T227 om-94), Peach.RTM. pulp has much lower fiber length,
higher population and much higher fines than the FR 416 refined
under same condition (Table 6).
TABLE-US-00006 TABLE 6 Refining performance of Peach and fluff pulp
FR 416 FR 416 Peach .RTM. Peach .RTM. Chemical Properties Refining
time (minute) 5 90 5 90 5 90 5 90 Freeness 751 704 749 696 Fiber
Properties FQA Fibers per gram, million 6.8 7.0 9.7 12.8 LWAFL, mm
2.54 2.59 2.44 2.47 2.16 2.20 2.05 2.05 Fiber Coarseness, mg/100 m
20.1 19.7 18.0 17.2 Kink Index, 1/mm 1.8 1.6 2.2 1.9 2.3 2.1 3.0
2.7 Kink number, 1/mm 0.9 0.8 1.0 0.9 1.1 1.0 1.3 1.1 Curl Index
0.16 0.12 0.19 0.16 0.19 0.16 0.25 0.21 WWAFL, mm 3.30 3.53 3.20
3.24 3.02 3.10 2.75 2.79 LW Fines, % 5.8 5.7 5.8 5.6 7.9 8.6 6.4
8.1
* * * * *