U.S. patent application number 15/932303 was filed with the patent office on 2018-09-27 for polysaccharide suspension, method for its preparation, and use thereof.
The applicant listed for this patent is LENZING AG. Invention is credited to Markus HAGER, Gert KRONER, Johann MANNER, Martina OPIETNIK, Sigrid REDLINGER.
Application Number | 20180273731 15/932303 |
Document ID | / |
Family ID | 55527164 |
Filed Date | 2018-09-27 |
United States Patent
Application |
20180273731 |
Kind Code |
A1 |
OPIETNIK; Martina ; et
al. |
September 27, 2018 |
POLYSACCHARIDE SUSPENSION, METHOD FOR ITS PREPARATION, AND USE
THEREOF
Abstract
The present invention relates to a novel stable colloidal
polysaccharide suspension containing .alpha.(1.fwdarw.3)-glucan, a
cost-effective method for its preparation, and possible uses of
these polysaccharide suspensions.
Inventors: |
OPIETNIK; Martina; (4840
Vocklabruck, AT) ; MANNER; Johann; (4852 Weyregg,
AT) ; HAGER; Markus; (4800 Attnang-Puchheim, AT)
; REDLINGER; Sigrid; (4860 Lenzing, AT) ; KRONER;
Gert; (4863 Seewalchen, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LENZING AG |
4860 Lenzing |
|
AT |
|
|
Family ID: |
55527164 |
Appl. No.: |
15/932303 |
Filed: |
February 3, 2016 |
PCT Filed: |
February 3, 2016 |
PCT NO: |
PCT/AT2016/000007 |
371 Date: |
February 16, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 3/05 20130101; C08L
5/00 20130101; C09D 105/00 20130101; C08L 2203/16 20130101; C08L
2203/02 20130101; C08B 37/0009 20130101; C08L 2201/54 20130101;
C08J 2305/00 20130101 |
International
Class: |
C08L 5/00 20060101
C08L005/00; C08B 37/00 20060101 C08B037/00; C08J 3/05 20060101
C08J003/05; C09D 105/00 20060101 C09D105/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2015 |
AT |
A56/2015 |
Claims
1. A phase-stable, colloidal polysaccharide suspension
characterized in that the polysaccharide consists at least partly
of .alpha.(1.fwdarw.3)-glucan, that the .alpha.(1.fwdarw.3)-glucan
was never dried during its preparation, that the suspension was
prepared from a press cake having a polysaccharide content between
4 and 80% by weight, preferably between 15 and 45% by weight, and
that the polysaccharide concentration of the suspension is between
0.01 and 50% by weight, preferably between 1.0 and 20% by
weight.
2. A suspension as claimed in claim 1, characterized in that the
.alpha.(1.fwdarw.3)-glucan content of the polysaccharide is between
1 and 100% by weight, more preferably between 80 and 100% by
weight.
3. A polysaccharide suspension as claimed in claim 1, wherein at
least 90% of the .alpha.(1.fwdarw.3)-glucan consist of hexose units
and at least 50% of the hexose units are linked via
.alpha.(1.fwdarw.3)-glycosidic bonds.
4. A polysaccharide suspension as claimed in claim 1, containing
apart from the polysaccharide material 1 to 200% by weight, related
to the polysaccharide quantity, in incorporated additives selected
from the group comprising pigments, titanium oxides, especially
substoichiometric titanium dioxide, barium sulfate, ion exchangers,
polyethylene, polypropylene, polyester, latex, activated carbon,
polymeric superabsorbents, and flame retardants.
5. A method for preparing a polysaccharide suspension,
characterized in that a. the base material used is a press cake of
an initially moist polysaccharide material consisting at least
partly of .alpha.(1.fwdarw.3)-glucan, b. the press cake has a
solids content between 4 and 80% by weight (related to the entire
press cake), preferably between 15 and 45% by weight, c. the
desired polysaccharide concentration is adjusted to between 0.01
and 50% by weight (related to the entire suspension), preferably to
between 1.0 and 20% by weight, d. subsequently comminution with a
dispersing unit is carried out.
6. A method as claimed in claim 5, wherein after step d. an
additional treatment with a dispersing unit, preferably with a high
pressure homogenizer, is carried out.
7. A method as claimed in claim 5, wherein the degree of
polymerization of the .alpha.(1-.fwdarw.3)-glucan used, expressed
as weight average DP.sub.w, is between 200 and 2,000, preferably
between 400 and 1,000.
8. A use of the polysaccharide suspension as claimed in claim 1 for
the production of polysaccharide layers.
9. A use of the polysaccharide suspension as claimed in claim 1 as
a binder for other materials, wherein the adhesive effect is
achieved by drying and the formation of hydrogen bonds.
10. The use of the polysaccharide suspension as claimed in claim 9,
wherein the other material is a nonwoven material.
11. The use of the polysaccharide suspension as claimed in claim 9,
wherein the other material is present in a quantity of 200 to 1000%
by weight, related to the polysaccharide quantity.
12. A use of the polysaccharide suspension as claimed in claim 1
for the preparation of dried polysaccharide powder.
13. A dry polysaccharide powder as claimed in claim 12, prepared by
spray drying.
14. A use of the polysaccharide suspension as claimed in claim 1 as
a viscosity modifier.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a novel stable colloidal
polysaccharide suspension containing .alpha.(1.fwdarw.3)-glucan, a
cost-effective method for its preparation, and possible uses of
these polysaccharide suspensions. Such suspensions are often also
referred to as "gels", and in the present invention both terms
shall be construed as synonymous.
Prior Art
[0002] It is known that natural polysaccharides such as xanthan
gum, alginate, guar gum, starch, etc., and also cellulose
derivatives such as carboxymethyl cellulose, hydroxymethylpropyl
cellulose dissolve as colloids in water and, in certain conditions,
exhibit gel-forming capacity. Due to their water solubility, the
above-mentioned substances do not form stable colloidal
suspensions.
[0003] Cellulose is the most widely encountered polysaccharide
worldwide. The preparation of suspensions from nanofibrillar
cellulose and fibrous pulp gels having cellulose I structure,
respectively, is known. Relevant prior art patents and publications
are cited in WO2013/006876A1. The preparation of cellulose gels
according to the amine oxide process and having cellulose II
structure is described in WO2013/006876A1. Meanwhile, it was found
that it is also possible to use a high pressure homogenizer to
prepare a phase-stable cellulose suspension with a cellulose
concentration between 0.1 and 4.0% by weight and a water retention
capacity from 500 to 5000% from a spinning dope according to the
amine oxide process with a higher cellulose content (for example of
13% by weight of cellulose).
[0004] Compared to microfibrillated cellulose or other types of
nanocellulose, cellulose gels prepared according to the amine oxide
process (the solvent used is a tertiary amine oxide, preferably
N-methylmorpholine-oxide) exhibit significant product advantages:
They no longer have a purely fibrous structure, but are largely
isotropic. The particles are highly swollen and form a
3-dimensional network. These gels can be obtained by precipitating
various molded bodies from the spinning dope, weakening these
molded bodies through enzymatic treatment, coarse comminution, and
subsequent grinding in a high pressure homogenizer.
[0005] U.S. Pat. No. 7,000,000 describes fibers obtained by
spinning a solution of polysaccharides that consist substantially
of hexose repeat units linked via .alpha.(1.fwdarw.3)-glycosidic
bonds. These polysaccharides can be prepared by bringing an aqueous
solution of saccharose into contact with GtfJ glucosyl transferase,
isolated from streptococcus salivarius (Simpson et al.
Microbiology, vol 41, pp 1451-1460 (1995)). As used herein,
"substantially" means that there may be sporadic defects within the
polysaccharide chains, where other bond configurations occur. For
the purposes of the present invention, these polysaccharides shall
be referred to as ".alpha.(1.fwdarw.3)-glucan".
[0006] A disclosure of the preparation of such glucans can be found
in U.S. Pat. No. 6,284,479 A1: the polysaccharide mixtures
described therein are to contain .alpha.(1.fwdarw.3)-,
.alpha.(1.fwdarw.6)-, (1.fwdarw.2)- and (1.fwdarw.4)-linked glucans
in proportions that were not explained in further detail. These
products shall be used, entirely or partially, replace starch or
latex in coatings. However, U.S. Pat. No. 6,284,479 A1 does not
provide any further details in this regard.
[0007] U.S. Pat. No. 7,000,000 first discloses possible ways to
enzymatically prepare .alpha.(1.fwdarw.3)-glucan from
monosaccharides. In this way, relatively short-chained
polysaccharides can be prepared without the loss of monomer
building blocks, as the polymer chains are built using the monomer
building blocks. In contrast to the preparation of short-chained
cellulose molecules, the preparation of .alpha.(1.fwdarw.3)-glucan
is the more cost-effective, the shorter the polymer chains are, as
in that case only a very short residence time in the reactors will
be required.
[0008] Another option for the enzymatic preparation of
.alpha.(1.fwdarw.3)-glucan from monosaccharides is disclosed in
WO2013/036968A1 and WO2013/036918A2. According to this method, a
particularly pure .alpha.(1.fwdarw.3)-glucan, substantially without
the formation of other polysaccharides, can be prepared.
[0009] Glucan gels are known in literature, however, none of those
found contains .alpha.(1.fwdarw.3)-glucan. Those found in
literature are either .alpha.(1.fwdarw.4)-glucans produced by
glucan phosphorylases (JP2006211989) and processed into a gel by
dissolving in alkaline medium and renewed precipitating
(US2003185863, WO2012073019A1). Or .beta.(1.fwdarw.3)-glucans that
are water soluble and are processed into a gel by adding starch and
plasticizers (US2003185863). A direct preparation of such gels
without preceding dissolving and precipitating or other chemical
pretreatments is not known.
Object
[0010] Compared to the state of the art, the object was to provide
a phase-stable colloidal polysaccharide suspension whose
preparation requires no chemical or enzymatic pretreatment of the
polysaccharide and offers high energy efficiency. The
polysaccharide base material should be inexpensive to produce, and
the process of preparing the suspension should be simplified as
compared to existing methods.
DESCRIPTION OF THE INVENTION
[0011] Surprisingly, this object was achieved by using
biotechnologically produced and never-dried
.alpha.(1.fwdarw.3)-glucan. From the polysaccharide described in
U.S. Pat. No. 7,000,000, and particularly in WO2013/036968A1 and
WO2013/036918A2, as long as it was never dried, it is possible to
prepare, by solely mechanical treatment, a polysaccharide
suspension that has no fibrillar structure and forms a
3-dimensional network.
[0012] The .alpha.(1.fwdarw.3)-glucan can be prepared by bringing
an aqueous solution of saccharose into contact with GtfJ
glucosyltransferase isolated from Streptococcus salivarius (Simpson
et al. Microbiology, vol 41, pp 1451-1460 (1995)).
[0013] Hence, the solution of the above-mentioned object consists
in providing a phase-stable colloidal polysaccharide suspension
that is characterized in that the polysaccharide consists at least
partly of .alpha.(1.fwdarw.3)-glucan, that the
.alpha.(1.fwdarw.3)-glucan was never dried during its preparation,
that the suspension was prepared from a press cake having a
polysaccharide content between 4 and 80% by weight, preferably
between 15 and 45% by weight, and that the polysaccharide
concentration of the suspension is between 0.01 and 50% by weight,
preferably between 1.0 and 20% by weight.
[0014] The .alpha.(1.fwdarw.3)-glucan content of the polysaccharide
may be between 1 and 100% by weight, more preferably between 80 and
100% by weight. The remaining polysaccharides can preferably be
cellulose gels, more preferably such that were prepared according
to the amine oxide process and have cellulose II structure. For
example, such gels can be prepared according to WO2013/006876A1.
They can also be prepared according to the amine oxide process, as
already described further hereinabove, with a cellulose
concentration between 0.1 and 4.0% by weight from a spinning dope
with a higher cellulose content (for example, of 13% by weight of
cellulose) by using a high pressure homogenizer.
[0015] Furthermore, the remaining polysaccharides can be
gel-forming polysaccharides known to those skilled in the art, such
as cellulose derivatives, for example carboxymethyl cellulose, or
starch. Such mixtures can for example be employed advantageously in
the paper industry.
[0016] The remaining polysaccharides can also be other glucans,
particularly .alpha.(1.fwdarw.6)-, (1.fwdarw.2)-, and
(1.fwdarw.4)-linked glucans.
[0017] In particular, the polysaccharide suspension according to
the invention is also advantageous because it was prepared without
chemical or enzymatic pretreatment, without high pressures, and
without high shear rates during comminution, as well as without
dissolving or precipitating steps.
[0018] In a preferred embodiment, a dispersing unit which generates
a low shear rate as compared to, for example, high press
homogenizers, for example, an Ultraturrax.RTM. mixer or a colloid
mill, is employed during the preparation of the polysaccharide
suspension from the press cake.
[0019] The above-mentioned remaining polysaccharides can preferably
be added to the .alpha.(1.fwdarw.3)-glucan during this suspension
preparation process.
[0020] According to the invention, the polysaccharide suspension
may, apart from the polysaccharide material, also contain 1 to 200%
by weight, related to the polysaccharide quantity, in incorporated
additives selected from the group comprising pigments, titanium
oxides, especially substoichiometric titanium dioxide, barium
sulfate, ion exchangers, polyethylene, polypropylene, polyester,
latex, activated carbon, polymeric superabsorbents, and flame
retardants.
[0021] In a preferred embodiment of the inventive method at least
90% of the .alpha.(1.fwdarw.3)-glucan are hexose units and at least
50% of the hexose units are linked via
.alpha.(1.fwdarw.3)-glycosidic bonds. It is used in its never-dried
form.
[0022] The suspension according to the invention is based on a
water-containing, particularly an initially moist,
.alpha.(1-.fwdarw.3)-glucan that was never dried after its
preparation. In water, .alpha.(1.fwdarw.3)-glucan is not dissolved
as a colloid. No dissolving or subsequent precipitating step as
described for glucan gels known in literature is necessary.
Typically, for the preparation of cellulose gels, a pretreatment to
weaken the surface structure (enzyme treatment, chemical treatment)
with a downstream treatment by means of high pressure homogenizers
is employed. For the preparation of the inventive polysaccharide
suspensions, the above-mentioned preparation steps are not
necessary; grinding using a dispersing unit (e.g., Ultraturrax.RTM.
or a colloid mill) is sufficient. Compared to a cellulose gel, this
reduces severalfold the total energy to be used. By avoiding a
dissolving step during the preparation of the inventive
suspensions, the introduction of residual quantities of solvent
into the final suspension is prevented, which makes it particularly
suited for applications in sensitive fields of use (foodstuffs,
pharmaceuticals, and cosmetics).
[0023] The polysaccharide used as a base material for the
suspension is preferably prepared according to U.S. Pat. No.
7,000,000 and more preferably according to WO2013/036968A1 and
WO2013/036918A2. According to the invention, it is used in its
initially moist state, i.e., it was never dried prior to preparing
the suspension. It consists at least partly of
.alpha.(1.fwdarw.3)-glucan. In the last procedural step of its
preparation, it is pressed to a solids content between 4 and 80% by
weight (related to the entire press cake), preferably to 15 to 45%
by weight. By adding water, the desired polysaccharide
concentration is adjusted to between 0.01 and 50% by weight
(related to the total suspension), preferably to between 1.0 and
20% by weight, and by subsequent comminution using suitable
dispersing units (e.g., Ultraturrax.RTM., colloid mill, . . . ) the
polysaccharide suspension is prepared. Pretreatments to weaken the
molded bodies and subsequent treatments under high shear (for
example in the high pressure homogenizer) are not absolutely
necessary to form these polysaccharide gels. This constitutes a big
advantage over cellulose gels. The solids content of the
polysaccharide suspensions according to the invention shall be
between 0.01 and 50% by weight, preferably between 0.1 and 20%, and
the polysaccharide must never be dried during their
preparation.
[0024] Summing up, the inventive method for preparing a
polysaccharide suspension is characterized in that a) a press cake
of an initially moist polysaccharide material is used as a base
material, which polysaccharide material consists at least partly of
.alpha.(1.fwdarw.3)-glucan, b) the press cake has a solids content
between 4 and 80% by weight (related to the entire press cake),
preferably from 15 to 45% by weight, c) the desired polysaccharide
concentration is adjusted (typically by adding water) to between
0.01 and 50% by weight (related to the entire suspension),
preferably to between 1.0 and 20% by weight, and d) subsequently, a
comminution using a dispersing unit is carried out.
[0025] By additional treatment using a high pressure homogenizer as
a grinding unit, it is possible to slightly improve the homogeneity
of the suspension further if necessary.
[0026] However, once the polysaccharide prepared according to U.S.
Pat. No. 7,000,000 and, in particular, according to WO2013/036968A1
and WO2013/036918A2 was already dried prior to the formation of the
suspension, i.e., if it is no longer initially moist, by suspending
it again in water gels will be formed only to a limited degree,
which exhibit only low suspension stabilities and barely
perceptible viscosity increases.
[0027] The degree of polymerization of the
.alpha.(1.fwdarw.3)-glucan used in the method according to the
invention, expressed as weight average DP.sub.w, can be between 200
and 2,000; values between 400 and 1,000 are preferred. Due to the
enzymatically controlled preparation of these glucans, their
molecular weight distribution is very narrow. Such narrow
distributions do not occur with natural polysaccharides.
[0028] The suspensions according to the invention exhibit,
depending on the adjusted suspension concentration, film-forming
properties and are particularly well suited for the preparation of
polysaccharide layers, especially of sheets or coatings of other
bodies, for example for coatings on different surfaces. This
includes for example paper and packaging applications. If the
suspensions according to the invention form films or layers, they
act as barriers for many substances because of their uniform and
dense structure. The polysaccharide suspension according to the
invention is also suited as an additive to existing coating
mixtures, e.g., in the paper industry. These films or layers can be
formed by doctoring, spraying, or brushing, and/or by evaporating
the aqueous phase and/or by additional measures such as heating or
pressing. These films or layers can be connected firmly with the
substrate (especially if this substrate also contains
polysaccharides), or be separate. For the purpose of forming a
film, wet strength agents or plasticizers can still be added to the
polysaccharide suspension according to the invention. Also
crosslinking of the films or layers is possible. The coatings can
be continuous or also intermittent. Possible intermittent coatings
are perforations or also the creation of artistically designed
patterns or ornaments.
[0029] In addition to the production of films or coatings, also the
production of other molded bodies from the polysaccharide
suspension according to the invention is possible, for example, by
means of extrusion or also by using suitable molds. For this
purpose, it is advantageous to use the polysaccharide suspension
according to the invention in as high a concentration as possible
and to add suitable additives to it, respectively.
[0030] Furthermore, the suspensions according to the invention are
well suited for all types of use where viscosity modifiers are
needed in order to produce a cream-like consistency of the final
products. The swollen polysaccharide particles are able to bind
large quantities of water and thus already exert a thickening
effect at lower concentrations than the polysaccharide suspensions
prepared according to the state of the art.
[0031] The polysaccharide suspension according to the invention can
be used as a base material for the preparation of dried
polysaccharide powder which is also a subject-matter of the present
invention. Simple drying of the inventive suspensions causes
agglomerates and compact layers to be formed due to the formation
of hydrogen bonds, which explains the film-forming properties.
Special drying methods (spray drying, freeze drying) cause the
formation of separated particles and fewer agglomerates. Spray
drying also makes it possible to produce hybrid particles. The
additives can be admixed to the suspension according to the
invention during its preparation or only be added during the drying
process. Another drying option is supercritical drying. In this
case, the aqueous phase is replaced by a suitable, apolar solvent.
The strength of the hydrogen bonds is reduced during removal of the
solvent by means of supercritical CO.sub.2 and the 3-dimensional
network of the gel remains intact; so-called aerogels are
formed.
[0032] Prior to the drying step, it is also possible to add
so-called "spacers" to the inventive suspension. The spacers can,
for example, be inorganic salts, polyethylene glycol, cellulose
derivatives, or also other substances known as spacers in the field
of gels. These spacers are deposited between the polysaccharide
molecules and, by doing so, prevent the formation of excessively
strong hydrogen bonds. Even though agglomerates are formed in this
case, they can be redispersed. The formation of these agglomerates
can be advantageous for dosing applications.
[0033] Hereinbelow, spray drying will be described in greater
detail: the substrate to be dried, i.e., the polysaccharide gel
according to the invention, is atomized into fine droplets via a
nozzle. The droplets are discharged together with the hot air
stream in a separating cyclone, and, during this process, water is
evaporated. Different parameters such as the solids concentration,
the size of the spraying nozzle, or the temperature difference
between supply air and exhaust air flow can be used to influence
the particle structure. The polysaccharide particles obtained in
this process have an average diameter from less than 1 .mu.m to up
to 5 .mu.m. The principle and the schematics of spray drying are
shown in FIG. 8 wherein: [0034] A: Supply of polysaccharide
suspension [0035] B: Supply of spray air (=compressed air) [0036]
TE: Temperature measurement for supply air [0037] TA: Temperature
measurement for exhaust air [0038] 1: Intake port for supply air
[0039] 2: Electrical heater [0040] 3: Spraying nozzle [0041] 4:
Spraying cylinder [0042] 5: Exhaust air [0043] 6: Separating
cyclone [0044] 7: Exhaust air outlet filter [0045] 8: Collection
vessel for dried particles
[0046] The suspensions according to the invention have
shear-diluting properties and, due to the simple application
methods (brushing, spraying, etc.), can also be used as a binder
for other materials, and they are sufficiently liquid so as to also
fill small gaps. In such case, the other material is preferably
present in a proportion of 200 to 1000% by weight, related to the
quantity of polysaccharide. During drying, hydrogen bonds are
formed, and, with them, a relevant "adhesive effect" is
achieved.
[0047] In particular, when used as a binder, for example, for
nonwovens or similar open structures, the polysaccharide suspension
according to the invention can be applied such that either the
entire structure or only parts thereof are penetrated by the
suspension or a superficial coating is created. This results in yet
another significant increase of the strength of the resulting
composite material as compared to the original structure. When
brought into contact with water, such structures reinforced with
.alpha.(1.fwdarw.3)-glucan-containing suspensions can be broken up
again, which makes them suitable for possible uses in the field of
"flushable wipes", i.e., wipes that can be defibered in the waste
water stream.
[0048] According to the invention, further functional ities can be
incorporated into the polysaccharide suspension through the even
introduction of additives. A variety of organic (chitosan, . . . )
and inorganic (nanosilver, zinc oxide, . . . ) additives as well as
color pigments can be introduced into the suspension.
[0049] Hereinbelow, the invention will be described with reference
to examples. However, the invention is expressly not limited to
these examples, but also includes all other embodiments that are
based on the same inventive concept.
EXAMPLES
[0050] General information: percentages are always to be understood
as % by weight unless indicated otherwise.
Example 1
[0051] A press cake of water-containing, initially moist
.alpha.(1.fwdarw.3)-glucan (dry matter content=17.6% by weight) is
suspended in deionized water and, using an Ultraturrax.RTM. ("UT"),
type IKA T50 basic, 6,000 rpm, is comminuted for 4 minutes. In this
experiment, the suspension to be comminuted contained 3.05% by
weight of .alpha.(1.fwdarw.3)-Glucan (atro). The suspension
prepared in this way was divided into two subquantities, and one
subquantity was additionally pumped in circulation via a high
pressure homogenizer (HDH), type GEA Niro Soavi NS 1001L-2K,
operating pressure 1,000 bar, for 2 passes. Then, the two glucan
suspensions were characterized based on viscosity and water
retention capacity.
[0052] The water retention capacity (WRC) of the glucan particles
was determined as follows: an exactly defined quantity of
suspension was introduced into special centrifuge tubes (with a
drain for the water). Then, centrifuging was carried out for 15 min
at 3,000 rpm, and the moist glucan was weighed immediately
thereafter. The moist glucan was dried over night at 105.degree.
C., and then the dry weight was determined. The WRC was calculated
according to the following formula:
WRC[%]=(m.sub.f-m.sub.t)/m.sub.t*100 [0053] (m.sub.f=moist mass,
m.sub.t=dry mass)
[0054] The determined dry contents (TS) and WRC are compiled in
Table 1.
TABLE-US-00001 TABLE 1 Dry contents and WRC of the glucan
suspensions Suspension after UT Suspension after UT + HDH TS [%]
WRC [%] TS [%] WRC [%] 3.05 1203 3.01 1538
[0055] The viscosities of the two suspensions exhibit
shear-diluting behavior and do not differ in their curves (FIG. 1).
The viscosities were determined using a Malvern Kinexus rheometer
with a cone plate measuring system (CP4/40 S0687 SS) in a shear
rate range from 10-200 s.sup.-1.
[0056] For comparison purposes, experiments with dried glucans were
conducted. The glucans used were linear glucans with different
degrees of polymerization (DP.sub.w 1,000 and DP.sub.w 500) and a
branched glucan. In each of the three cases, the gels formed were
not uniform, and there was phase separation. The suspensions were
adjusted to a solids content of 2-3%, pre-comminuted by treatment
in the Ultraturrax.RTM. (UT, IKA T50 basic, 6,000 rpm) for 4 min,
and then treated with the high pressure homogenizer for 2 passes at
an operating pressure of 1,000 bar. Following that, dry content and
WRC were determined (Table 2). The WRC is far below the values of
the gels produced from initially moist glucan. Also, these
suspensions exhibit no increase in viscosity.
TABLE-US-00002 TABLE 2 Dry contents and WRC of the gels from dried
glucan Linear glucan DPw 1,000 Linear glucan DPw 500 Branched
glucan TS [%] WRC [%] TS [%] WRC [%] TS [%] WRC [%] 2.23 247 2.20
164 2.77 203
[0057] The suspensions treated in this way were swollen over night
in order to make the surface more accessible. On the following day,
the samples were treated again with the HDH for 4 passes at 1,000
bar. It was demonstrated that the dried glucans used are unsuitable
for preparing suspensions: even after 6 passes on the HDH, there
still was phase separation, and particles were visually
recognizable (FIG. 2).
Example 2
[0058] By preparing a bigger quantity of glucan gel (4% by weight)
in a pilot-plant-based experiment with a colloid mill (IKA Colloid
Mill MK2000/10), it was to be demonstrated that even large
quantities of polysaccharide can be processed into a homogeneous
suspension without the use of high pressure homogenizers.
[0059] From 3.69 kg of never-dried, initially moist
.alpha.(1.fwdarw.3)-glucan (TS=16.25%) and 11.3 kg of water, a
glucan gel having a solids content of 3.9% was prepared by grinding
in the colloid mill (IKA Colloid Mill MK2000/10). After 15 minutes
of grinding with a gap of 0.1 mm at maximum output, the glucan gel
was ready. Subsequently, it was characterized as follows:
[0060] Viscosity: the glucan gel was measured on the Malvern
Kinexus rheometer with a cone plate measuring system (CP4/40 S0687
SS) in a shear rate range from 10-200 s.sup.-1. The suspension
according to the invention exhibited shear-diluting behavior (FIG.
3).
[0061] Microscopy: the glucan gel was filled between two microscope
slides, whereby a thin layer was formed. This layer was subjected
to microscopic examination. A strip of adhesive tape (Scotch tape,
matt, approx. 0.3 mm) was adhered to the rim of each lower slide in
order to achieve uniform layer thickness. The photos were taken on
the ZEISS Discovery V12 stereomicroscope with 50-fold magnification
and bottom illumination (FIG. 4). Agglomerates can be recognized
that are formed from the very small particles in the suspension.
However, these agglomerates can not be felt when rubbed between the
fingers and will disintegrate again under the slightest shear.
[0062] Glass tube method: 10 g of glucan gel were weighed into
glass tubes (length=approx. 9.7 cm, O 2.5 cm) provided with closure
caps, shaken, placed upside down, and photographed after 10
seconds. The glass tube was positioned in front of a black
background and illuminated from the above using a table lamp
(distance to underlying surface about 22 cm).
[0063] The photos were taken using a Canon EOS450D digital camera.
Again, no particles are visible (FIG. 5). A uniform, dense film is
formed along the glass wall.
[0064] The film-forming properties of these suspensions were tested
on different surfaces.
[0065] The suspension according to the invention of Example 2 was
applied onto polyester (PES) sheets or glass by doctoring and
spraying, respectively. Both coating methods produced continuous,
uniform films that adhere readily to the substrates. FIG. 6 shows
the transparency of such films on PES sheets: the right-hand side
of the picture is covered with the coated PES sheet; the left-hand
side is not covered.
[0066] SEM photos (Hitachi S-4000 SEM scanning electron microscope)
were taken of the air-dried films; here, we see the structure of
the dense layer which simultaneously exhibits a large inner surface
(FIG. 7).
[0067] In addition, SEM photos were taken of the freeze-dried
glucan gel (FIG. 8). Here, we can notice the 3-dimensional spongy
network that is formed in the glucan gel and imparts to the
inventive suspension its unique properties.
Example 3
[0068] Glucan gels having different solids concentrations were
produced in a manner similar to Example 2. As the solids content
increases, the viscosities of the suspensions increase (FIG. 9),
while the water retention capacity (WRC) decreases. While
suspensions having a solids content of 3 and 4% can still be
processed with an HDH, suspensions having a solids content of 5%
can only be comminuted with a device with lower shear such as an
Ultraturrax IKA T50 basic ("IKA"), as the HDH is unable to pump
such highly viscous suspensions. Table 3 shows that, as the solids
content increases, the viscosity increases, but the WRC decreases
at the same time.
TABLE-US-00003 TABLE 3 Comparison of viscosities and WRC of the
various glucan gels after comminution. Treatment after HDH after
IKA after UT TS [%] 3 4 5 WRC [%] 1538 1504 506 Viscosity
[50.sup.s-1] 0.2009 0.8555 1.731
Example 4
[0069] In the following example, the 3% glucan gel from Example 3
was dried in a laboratory spray dryer (Buchi Mini Spray Dryer
8-290, see FIG. 10). The particle size distribution was determined
by means of laser diffraction (measuring apparatus from Helos) in
iso-propanol. Parameters: supply air temperature 180.degree. C. and
exhaust air temperature 62.degree. C.; nozzle size 1.4 mm. The
particle size distribution was as follows:
x.sub.10=0.79 .mu.m; x.sub.50=2.2 .mu.m; x.sub.90=5.29 .mu.m;
x.sub.99=8.27 .mu.m.
Example 5
[0070] 1.887 kg of never-dried, initially moist
.alpha.(1.fwdarw.3)-glucan (TS=39.74%) and 5.613 kg of water were
used to prepare a suspension with 10% of glucan by using an IKA
mill (IKA MK2000/10 colloid mill). After 20 minutes of grinding
with a gap of 0.1 mm and at maximum output, the glucan suspension
was ready. A stable suspension was formed which in terms of its
viscosity is comparable with the 4% glucan suspension from Example
2 (FIG. 12).
[0071] Furthermore, microscopic photos (FIG. 13) were taken of the
gel from Example 5 under the conditions described in Example 2.
Again, small particles can be noticed which, however, also in this
case cannot be felt between the fingers.
* * * * *