U.S. patent application number 13/817178 was filed with the patent office on 2013-09-19 for method for the production of oxidized cellulose fibers, oxidized cellulose fiber sheet materials or oxidized cellulose nonwovens, and use thereof.
This patent application is currently assigned to CARL FREUDENBERG KG. The applicant listed for this patent is Gunter Scharfenberger, Bernd Schlesselmann, Julia Schmidt, Wiebke Schmitz. Invention is credited to Gunter Scharfenberger, Bernd Schlesselmann, Julia Schmidt, Wiebke Schmitz.
Application Number | 20130244523 13/817178 |
Document ID | / |
Family ID | 44654054 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130244523 |
Kind Code |
A1 |
Schmitz; Wiebke ; et
al. |
September 19, 2013 |
METHOD FOR THE PRODUCTION OF OXIDIZED CELLULOSE FIBERS, OXIDIZED
CELLULOSE FIBER SHEET MATERIALS OR OXIDIZED CELLULOSE NONWOVENS,
AND USE THEREOF
Abstract
A method for the production of at least one of oxidized
cellulose fibers, oxidized cellulose fiber sheet materials and
oxidized cellulose nonwovens includes introducing at least one of
cellulose fibers, cellulose fiber sheet materials and cellulose
nonwovens into a reactor. A temperature of the reactor is set in a
range from 25.degree. C. to 80.degree. C. Gaseous nitrogen dioxide
is introduced into the reactor so as to oxidize the at least one of
cellulose fibers, cellulose fiber sheet materials and cellulose
nonwovens. A temperature of the reactor is set in a range from
20.degree. C. to less than 160.degree. C. The at least one of
oxidized cellulose fibers, oxidized cellulose fiber sheet materials
and oxidized cellulose nonwovens are neutralized with at least one
base.
Inventors: |
Schmitz; Wiebke; (Mannheim,
DE) ; Schmidt; Julia; (Essen, DE) ;
Schlesselmann; Bernd; (Weinheim, DE) ;
Scharfenberger; Gunter; (Frankenthal, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schmitz; Wiebke
Schmidt; Julia
Schlesselmann; Bernd
Scharfenberger; Gunter |
Mannheim
Essen
Weinheim
Frankenthal |
|
DE
DE
DE
DE |
|
|
Assignee: |
CARL FREUDENBERG KG
Weinheim
DE
|
Family ID: |
44654054 |
Appl. No.: |
13/817178 |
Filed: |
July 29, 2011 |
PCT Filed: |
July 29, 2011 |
PCT NO: |
PCT/EP11/03805 |
371 Date: |
February 15, 2013 |
Current U.S.
Class: |
442/327 ;
427/248.1; 536/56 |
Current CPC
Class: |
C08B 15/04 20130101;
D06M 2101/06 20130101; D06M 11/60 20130101; Y10T 442/60 20150401;
D21C 9/002 20130101; A61L 15/28 20130101; D06M 23/06 20130101; C08L
1/04 20130101; A61L 15/28 20130101; D06M 11/64 20130101 |
Class at
Publication: |
442/327 ;
427/248.1; 536/56 |
International
Class: |
D06M 23/06 20060101
D06M023/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2010 |
DE |
10 2010 034 782.5 |
Claims
1-9. (canceled)
10. A method for the production of at least one of oxidized
cellulose fibers, oxidized cellulose fiber sheet materials and
oxidized cellulose nonwovens, the method comprising: a) introducing
at least one of cellulose fibers, cellulose fiber sheet materials
and cellulose nonwovens into a reactor; b) setting a temperature of
the reactor in a range from 25.degree. C. to 80.degree. C.; c)
introducing gaseous nitrogen dioxide into the reactor so as to
oxidize the at least one of cellulose fibers, cellulose fiber sheet
materials and cellulose nonwovens; d) setting a temperature of the
reactor in a range from 20.degree. C. to less than 160.degree. C.;
and e) neutralizing the at least one of oxidized cellulose fibers,
oxidized cellulose fiber sheet materials and oxidized cellulose
nonwovens with at least one base.
11. The method according to claim 10, wherein step c) is performed
to provide a degree of oxidation between 1% and 50%.
12. The method according to claim 11 wherein the degree of
oxidation is between 5% and 35%.
13. The method according to claim 10, wherein the temperature in
step b) is in a range from 30.degree. C. to 60.degree. C.
14. The method according to claim 10, wherein the temperature in
step d) is not more than 100.degree. C.
15. The method according to claim 10, wherein the at least one base
includes gaseous ammonia.
16. The method according to claim 10, wherein the at least one of
cellulose fibers, cellulose fiber sheet materials and cellulose
nonwovens have a fiber fineness of 0.5 dtex to 30 dtex and a fiber
length between 3 mm and 120 mm.
17. The method according to claim 10, wherein the at least one of
cellulose fibers, cellulose fiber sheet materials and cellulose
nonwovens have a moisture content of 7% by weight at the
maximum.
18. The method according to claim 10, farther comprising adding at
least one additive including at least one of synthetic polymers,
biopolymers, active ingredients and special additives to the at
least one of oxidized cellulose fibers, oxidized cellulose fiber
sheet materials and oxidized cellulose nonwovens,
19. The method according to claim 4, wherein the at least one
additive includes at least one of polyvinyl alcohols, polyolefins,
polyethylene glycols, polyesters, medications and agents that
promote wound healing.
20. The method according to claim 10, wherein the gaseous nitrogen
dioxide is used without the addition of halogenated hydrocarbons
and is circulated.
21. The method according to claim 10, wherein a pressure of the
reactor is in a range from 0.1 bar to 7 bar,
22. The method according to claim 21, wherein the pressure is in a
range from 0.8 bar to 3 bar.
23. Oxidized cellulose fibers, oxidized cellulose fiber sheet
materials or oxidized cellulose nonwovens produced by a method
according to claim 10, which exhibit an absorption of an aqueous
0.9% sodium chloride solution in a range from 400% to 10,000% by
weight.
24. A method of using at least one of oxidized cellulose fibers,
oxidized cellulose fiber sheet materials and oxidized cellulose
nonwovens produced by the method according to claim 10, for a
medical sector, as or for at least one of wound dressings, tissue
constructions, tissue growing, tissue engineering, implants,
packaging, cosmetic, hygiene or household products, cleaning
supplies and filters, insulating substances and support materials,
catalysts, furniture, clothing, interlinings, interfacing, noise
and heat protection.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. National Phase application under
35 U.S.C. .sctn.371 of International Application No.
PCT/EP2011/003805, filed on Jul. 29, 2011, and claims benefit to
German Patent Application No. DE 10 2010 034 782.5, filed on Aug.
18, 2010. The International Application was published in German on
Feb. 23, 2012 as WO 2012/022421 under PCT Article 21(2).
FIELD
[0002] The present invention relates to a method for the production
of oxidized cellulose fibers, oxidized cellulose fiber sheet
materials or oxidized cellulose nonwovens as well as to the use
thereof.
BACKGROUND
[0003] The term fiber sheet material refers especially to an
ordered or unordered single-layer or multi-layer combination of
many fibers.
[0004] U.S. Pat. No. 3,364,200 A describes the oxidation of
cellulose with nitrogen dioxide/dinitrogen tetroxide for use in the
medical sector. According to U.S. Pat. No. 3,364,200 A, the
cellulose is oxidized with liquid nitrogen dioxide, nitrogen
tetroxide or mixtures thereof and the oxidized cellulose is treated
by means of special washing methods that particularly also provide
for the use of halogenated hydrocarbons.
[0005] The above-mentioned method is disadvantageous from an
environmental standpoint and calls for additional cleaning
steps.
[0006] German patent application DE 44 26 443 Al describes the
oxidation of polysaccharide powder, especially starch, with
nitrogen dioxide/dinitrogen tetroxide gases. In order to achieve a
thorough mixing of the starch powder with the gas, preferably
additional components are used such as, for example, zeolites or
silica gel, which have to be separated out again after the process.
The produced polycarboxylate powders are used as builders or
co-builders in detergents and cleaning agents.
SUMMARY
[0007] In an embodiment the present invention provides a method for
the production of at least one of oxidized cellulose fibers,
oxidized cellulose fiber sheet materials and oxidized cellulose
nonwovens. At least one of cellulose fibers, cellulose fiber sheet
materials and cellulose nonwovens is introduced into a reactor. A
temperature of the reactor is set in a range from 25.degree. C. to
80.degree. C. Gaseous nitrogen dioxide is introduced into the
reactor so as to oxidize the at least one of cellulose fibers,
cellulose fiber sheet materials and cellulose nonwovens. A
temperature of the reactor is set in a range from 20.degree. C. to
less than 160.degree. C. The at least one of oxidized cellulose
fibers, oxidized cellulose fiber sheet materials and oxidized
cellulose nonwovens are neutralized with at least one base.
DETAILED DESCRIPTION
[0008] The present invention provides, in an embodiment, an
improved method for the production of oxidized cellulose fibers,
oxidized cellulose fiber sheet materials or oxidized cellulose
nonwovens, especially for the production of oxidized cellulose
wound dressings, said method being particularly simple and
efficient as well as environmentally friendly, since it especially
can make do without the use of additional mixing additives, and
whereby especially no waste products are formed and/or no demanding
cleaning steps are necessary.
[0009] In an embodiment, the oxidized cellulose fibers, oxidized
cellulose fiber sheet materials or oxidized cellulose nonwovens
produced according to the method should exhibit an especially high
absorption of an aqueous 0.9% sodium chloride solution
(physiological saline solution), they should be water-insoluble,
and they should be suitable for many uses, especially in medical
applications, particularly for wound care.
[0010] The absorption of an aqueous 0.9% sodium chloride solution
is determined on the basis of German standard DIN 53923. Instead of
the absorption of water, the absorption of an aqueous 0.9% sodium
chloride solution is determined.
[0011] According to an embodiment of the invention, the method for
the production of oxidized cellulose fibers, oxidized cellulose
fiber sheet materials or oxidized cellulose nonwovens, especially
with a degree of oxidation between 1% and 50%, preferably between
5% and 35%, comprises the following steps: [0012] a) using
cellulose fibers, cellulose fiber sheet materials or cellulose
nonwovens, [0013] b) setting the temperature within the range from
25.degree. C. to 80.degree. C. [77.degree. F. to 176.degree. F.],
preferably from 30.degree. C. to 60.degree. C. [86.degree. F. to
140.degree. F.], [0014] c) introducing gaseous nitrogen dioxide,
[0015] d) setting the temperature within the range from 20.degree.
C. [68.degree. F.] to less than 160.degree. C. [320.degree. F.],
preferably up to 100.degree. C. [212.degree. F.], and [0016] e)
neutralizing the oxidized cellulose fibers, oxidized cellulose
fiber sheet materials or oxidized cellulose nonwovens with bases,
particularly with gaseous ammonia.
[0017] The terms fibers, fiber sheet materials or nonwovens made of
cellulose refer to those made of pure cellulose and also to those
made of cellulose derivatives or of cellulose in combination with
other polysaccharides.
[0018] Examples of these are preferably cellulose ethers, such as
methyl cellulose, ethyl cellulose or butyl cellulose, hydroxymethyl
cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose,
carboxymethyl cellulose, cellulose esters, such as cellulose
acetate, bacterial celluloses, viscoses as well as their
copolymers, such as block copolymers, graft copolymers, random or
alternating systems.
[0019] Cellulose fibers, cellulose fiber sheet materials or
cellulose nonwovens as the starting material are preferably used at
a fiber fineness of 0.5 dtex to 30 dtex, preferably between 1 dtex
and 10 dtex, especially preferably between 1.5 dtex and 5 dtex, as
well as especially with a fiber length between 3 mm and 120 mm,
whereby fibers that are preferably between 5 mm and 80 mm are of
interest for the production of nonwovens. Since the fibers, fiber
sheet materials or nonwovens are porous and have capillary
forces--in contrast, for instance, to the use of powders--this has
a positive influence on the conveying of the gaseous oxidant, for
instance, through the reactor. The gas is fed along the fibers,
thereby permitting a homogeneous distribution of the oxidation
gas.
[0020] In contrast, the process control becomes more difficult when
powders are used since a special reactor design is needed and
additives have to be used in order to ensure an intensive and
thorough mixing, so as to avoid the agglomeration of a
polysaccharide that is to be oxidized and so as to ensure the
formation of a fluidized bed.
[0021] Consequently, the method according to an embodiment of the
invention allows for a particularly simple and flexible reactor
design.
[0022] In order to reduce the humidity to a moisture content of 7%
by weight at the maximum and to bring the employed cellulose
fibers, cellulose fiber sheet materials or cellulose nonwovens to
the desired temperature, the reactor is preferably dried with inert
gas that has been preheated to the reaction temperature such as,
for instance, helium, argon or carbon dioxide or else air,
preferably with nitrogen. The reaction temperature here is between
25.degree. C. and 80.degree. C. [77.degree. F. and 176.degree. F.],
preferably between 30.degree. C. and 60.degree. C. [86.degree. F.
and 140.degree. F.].
[0023] In a preferred embodiment of the method, the gaseous
nitrogen dioxide is introduced at gas throughput rates ranging from
0.1 to 10 molar equivalents of nitrogen dioxide per hour, relative
to the hydroxy group that is to be oxidized. This is likewise
carried out in the preheated state.
[0024] Through the use of gaseous instead of liquid nitrogen
dioxide, it is possible to attain a high reactivity, especially a
shorter retention time or reaction time.
[0025] The reaction process can be carried out at particularly low
gas throughput rates since the use of cellulose fibers, cellulose
fiber sheet materials or cellulose nonwovens does not call for
intensive and thorough mixing. This is also advantageous in terms
of safety since, for example, in case of an accident or leak in the
reactor, the personnel is exposed to lower concentrations of
nitrogen dioxide. At the same time, the homogeneous distribution of
the gas can be easily achieved so that the result is a particularly
uniformly oxidized product with a uniform degree of oxidation.
[0026] The desired degree of oxidation is advantageously 1% to 50%,
preferably between 5% and 35%, relative to the number of OH groups
in cellulose that are to be oxidized, and it is determined, for
instance, by means of infrared spectroscopy (IR) or titration of
the oxidized groups.
[0027] Higher degrees of oxidation are not of interest with an eye
towards particularly desired products, especially towards their use
as wound dressings, nor are they feasible, since, for example, the
wound dressing is supposed to gel as it absorbs large quantities of
water and, in particular, it should not dissolve as is the case,
for instance, when used as a detergent or cleaning agent.
[0028] When the desired quantity of oxidant has been introduced, or
the desired degree of oxidation has been reached in order to shift
the equilibrium towards the product side, the entire system is set
to a temperature within a range that is preferably between
20.degree. C. and 100.degree. C. [68.degree. F. and 212.degree.
F.], whereby care is taken to ensure that the upper limit of
160.degree. C. [320.degree. F.] is not exceeded, since ever-greater
degradation is observed at higher temperatures.
[0029] This step also ensures that the content of groups containing
nitrogen is minimized in the final product, especially when
nitrogen dioxide is used as the oxidant.
[0030] In order to remove the residues of oxidant, especially of
nitrogen dioxide, flushing is carried out preferably with inert
gas, especially with nitrogen.
[0031] The method according to an embodiment of the invention is
particularly environmentally friendly, simple and efficient, since
the gaseous oxidant, especially the gaseous nitrogen dioxide, can
be circulated during the process control, and no additional
chemicals have to be used such as, for instance, fluorocarbons or
chlorofluorocarbons.
[0032] Nitrogen oxide that is formed during the reaction with
nitrogen dioxide can be converted back into nitrogen dioxide by
means of oxidation with oxygen and can be used for the further
oxidation in order to improve the environmental balance of the
process in that no waste product is formed.
[0033] Subsequently, the acid groups of the oxidized cellulose
fibers, oxidized cellulose fiber sheet materials or oxidized
cellulose nonwovens are neutralized with bases, particularly with
gaseous ammonia.
[0034] As an alternative, of course, the use of other basic
reagents for the neutralization is also possible such as, for
example, the use of alkaline alcoholic solutions such as, for
instance, potassium hydroxide solution.
[0035] Thanks to the use of gaseous ammonia, however, there is no
longer a need to clean and dry the product. Since this type of
process control can thus make do without the use of solvents and
since no waste products are generated, this reaction control is
particularly efficient and environmental friendly.
[0036] Subsequent to the neutralization, flushing is preferably
carried out again with inert gas, especially with nitrogen.
[0037] The method according to an embodiment of the invention takes
place particularly quickly, especially in just a few hours.
However, in other methods for manufacturing wound dressings such
as, for instance, the method of Johnson & Johnson according to
U.S. Pat. No. 3,364,200 A, the process takes several days.
[0038] In an advantageous embodiment of the method, at least one
additive can be added to the oxidized cellulose fibers, the
oxidized cellulose fiber sheet materials or the oxidized cellulose
nonwovens, and said additive can be selected from among the
following synthetic polymers, biopolymers, active ingredients
and/or special additives.
[0039] Examples of synthetic polymers that can be used are
polyoxymethylenes, polyamides, such as polyamide-66, polyurethanes,
polyvinylpyrrolidones, polyvinylamines, polyethylene imines,
polyesters, such as polyethylene terephthalate, polycarbonates,
polysiloxanes, such as polydimethylsiloxane, polyvinylalcohols,
polyolefins, such as polyethylene or polypropylene, polycarboxylic
acids, such as polyacrylic acid, polyacrylates, polymethacrylates,
such as polymethyl methacrylate or poly-(2-hydroxyethyl
methacrylate), polyalkylene oxides, such as polyethylene glycol or
polyethylene oxides, polystyrenes, polyvinylacetates,
polyvinylchloride, polycaprolactones, polylactides, polyglycolides
or polyhydroxybutteric acids.
[0040] Examples of biopolymers that can be used are proteins, such
as collagen, silks, keratins, albumins, polysaccharides, such as
starches, modified starches, celluloses, cellulose derivates, such
as cellulose ethers, cellulose esters, bacterial celluloses,
viscoses, chitins, chitosanes, caseins, pectins, agar, guar gums,
hyaluronic acid or alginates.
[0041] Examples of active ingredients or special additives that can
be used are medications, such as antibiotics, analgesics, agents
that promote wound healing, antibacterial, antiviral or
antimicrobial preparations, organic acids, enzymes, vitamins,
nicotine, proteins that have a positive effect on wound healing,
growth factors, such as purines or pyrimidines, stabilizers, carbon
compounds, such as activated charcoals, graphenes, carbon
nanotubes, metals, such as gold or silver, cyclodextrines,
inorganic particles, silicon particles, ceramics, such as silica
gels or silicates.
[0042] The above-mentioned polymers can be used as homopolymers, as
copolymers, for example, as block copolymers, graft copolymers,
random or alternating systems, or in any mixture of these.
[0043] The above-mentioned active ingredients or additives can be
added or adsorbed in pure form, in any desired mixture with each
other and/or in encapsulated form.
[0044] As additives, special preference is given to polyvinyl
alcohols, polyolefins, polyethylene glycols, polyesters,
medications as well as agents that promote wound healing.
[0045] Another advantage of the method is that the reaction can be
carried out practically pressure-free, that is to say, at normal
pressure, preferably at a pressure in the range from 0.1 bar to 7
bar, especially preferably from 0.8 bar to 3 bar.
[0046] The oxidized cellulose fibers can be processed and bonded to
form nonwovens.
[0047] The fibers, fiber sheet materials or nonwovens made of
oxidized cellulose can be further processed in any desired form.
Thus, they can be made into any three-dimensional shape, and can
also be used in combination with supports, especially through
application onto a support or through incorporation into a support
such as, for example, so-called sandwich structures.
[0048] Subsequent chemical modification is also conceivable.
[0049] The cellulose fibers, oxidized cellulose fiber sheet
materials or oxidized cellulose nonwovens produced according to an
embodiment of the invention have particularly low nitrate and
nitrite contents, less than 10% by weight.
[0050] Moreover, they have an especially good capacity to absorb an
aqueous 0.9% sodium chloride solution (physiological saline
solution).
[0051] The cellulose fibers, oxidized cellulose fiber sheet
materials or oxidized cellulose nonwovens according to an
embodiment of the invention preferably exhibit an absorption of an
aqueous 0.9% sodium chloride solution in a range from 400% to
10,000% by weight, especially preferably in a range from 400% to
5000% by weight, particularly preferably in a range from 400% to
3500% by weight.
[0052] Therefore, they are preferably used in the medical sector,
especially preferably as or for wound dressings, tissue
constructions or tissue growing (tissue engineering) or for
implants, but also for packaging, cosmetic, hygiene or household
products, especially cleaning supplies and/or for filters,
insulating substances and/or support materials, especially for
catalysts, furniture, clothing, especially as interlinings or
interfacing, and for noise and/or heat protection.
EXAMPLE
[0053] Cellulose fibers (100 grams, made by means of the NMMO
(N-methylmorpholine N-oxide) method in a titer of 1.7 dtex) are
placed into a flask at about 50.degree. C. [122.degree. F.] and
preferably at a pressure of 1 bar, whereby they are pre-dried if
the moisture content is not in the range from 0% to 7% by
weight.
[0054] In order to allow the defined conditions, the flask interior
is flushed with preheated inert gas, preferably with nitrogen.
Subsequently, 6 molar equivalents of nitrogen dioxide per hour,
relative to the alcohol group that is to be oxidized, are used for
the conversion into carboxyl groups amounting to 9% to 11% after 30
minutes and 30% to 35% after one hour in cellulose. The degree of
oxidation of the primary alcohol groups of the glucose molecule, as
a function of the fiber diameter, can be determined by means of
infrared spectroscopy (IR) or titration of the oxidized groups.
[0055] After the reaction, the gas feed is shut off and the flask
is heated to a temperature between 50.degree. C. and 100.degree. C.
[122.degree. F. and 212.degree. F.], preferably to about 80.degree.
C. [176.degree. F.], for about half an hour. This step ensures that
the content of groups containing nitrogen in the final product is
minimal.
[0056] In order to remove residues of nitrogen dioxide, the
cellulose fibers are once again flushed with inert gas, preferably
with nitrogen.
[0057] The nitrogen oxide that is formed during the reaction can be
converted into nitrogen dioxide by means of oxidation with oxygen
and, in order to avoid waste products, can be returned to the
circulation system of the above-mentioned oxidation process of the
cellulose. This improves the environmental balance of the
process
[0058] The subsequent neutralization of the acid groups of the
oxidized cellulose can be achieved with all kinds of bases.
Preferably, the oxidized fibers are neutralized here with gaseous
ammonia and checked for a gelling effect. The use of gaseous
ammonia avoids the need for cleaning and drying the product.
[0059] After the neutralization, the flask is preferably flushed
once again with nitrogen.
[0060] The oxidized cellulose fibers absorb 400% to 3500% by weight
of an aqueous 0.9% sodium chloride solution as a function of the
degree of oxidation.
[0061] The values for the absorption of an aqueous 0.9% sodium
chloride are determined on the basis of DIN 53923. Instead of the
absorption of water described in the DIN standard, the absorption
of an aqueous 0.9% sodium chloride solution is determined.
[0062] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive. It will be understood that changes and
modifications may be made by those of ordinary skill within the
scope of the following claims. In particular, the present invention
covers further embodiments with any combination of features from
different embodiments described above and below.
[0063] The terms used in the claims should be construed to have the
broadest reasonable interpretation consistent with the foregoing
description. For example, the use of the article "a" or "the" in
introducing an element should not be interpreted as being exclusive
of a plurality of elements. Likewise, the recitation of "or" should
be interpreted as being inclusive, such that the recitation of "A
or B" is not exclusive of "A and B." Further, the recitation of "at
least one of A, B and C" should be interpreted as one or more of a
group of elements consisting of A, B and C, and should not be
interpreted as requiring at least one of each of the listed
elements A, B and C, regardless of whether A, B and C are related
as categories or otherwise.
* * * * *