U.S. patent application number 10/037240 was filed with the patent office on 2002-10-03 for method of producing microcrystalline.
Invention is credited to Guo, Jian Xin, Matheson, Jim, Murphy, Sheila, Shaver, Linnea.
Application Number | 20020139498 10/037240 |
Document ID | / |
Family ID | 26713949 |
Filed Date | 2002-10-03 |
United States Patent
Application |
20020139498 |
Kind Code |
A1 |
Matheson, Jim ; et
al. |
October 3, 2002 |
Method of producing microcrystalline
Abstract
The present invention relates to a new method for producing
microcrystalline cellulose using never-dried pulp as the cellulose
source.
Inventors: |
Matheson, Jim;
(Jacksonville, FL) ; Guo, Jian Xin; (Chester,
NY) ; Murphy, Sheila; (St. Simon's Island, GA)
; Shaver, Linnea; (Tuxedo, NY) |
Correspondence
Address: |
OSTRAGER CHONG & FLAHERTY LLP
30th Floor
825 Third Avenue
New York
NY
10022-7519
US
|
Family ID: |
26713949 |
Appl. No.: |
10/037240 |
Filed: |
January 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60259960 |
Jan 5, 2001 |
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Current U.S.
Class: |
162/76 ; 162/207;
162/60 |
Current CPC
Class: |
C08B 15/02 20130101;
D21C 9/004 20130101 |
Class at
Publication: |
162/76 ; 162/60;
162/207 |
International
Class: |
D21C 003/04; D21C
009/02; D21F 005/00 |
Claims
We claim:
1. A method of producing microcrystalline cellulose comprising
selecting as a starting material, a never-dried cellulosic
material.
2. The method of claim 1 wherein the cellulosic material is
prehydrolyzed kraft hardwood.
3. The method of claim 1 wherein the cellulosic material is
prehydrolyzed kraft softwood.
4. The method of claim 1 wherein the cellulosic material is
hardwood sulfite.
5. The method of claim 1 wherein the cellulosic material is
softwood sulfite.
6. The method of claim 1 wherein the cellulosic material is
paper-grade softwood.
7. The method of claim 1 wherein the cellulosic material is
paper-grade hardwood.
8. The method of claim 2 wherein the prehydrolyzed kraft hardwood
is ESTERCELL.TM..
9. The method of claim 2 wherein the prehydrolyzed kraft hardwood
is TYRCELL.TM..
10. The method of claim 2 wherein the prehydrolyzed kraft hardwood
is VISCOCELL.TM..
11. A method of producing microcrystalline cellulose comprising:
(a) selecting as a starting material, a never-dried cellulosic
material; (b) subjecting the cellulosic material to acid
hydrolysis; (c) neutralizing the acid, (d) washing; and (e) drying
to form microcrystalline cellulose.
12. The method of claim 11 wherein the cellulosic material is
prehydrolyzed kraft hardwood.
13. The method of claim 11 wherein the cellulosic material is
prehydrolyzed kraft softwood .
14. The method of claim 11 wherein the cellulosic material is
hardwood sulfite.
15. The method of claim 11 wherein the cellulosic material is
softwood sulfite.
16. The method of claim 11 wherein the cellulosic material is
paper-grade softwood.
17. The method of claim 11 wherein the cellulosic material is
paper-grade hardwood.
18. The method of claim 12 wherein the prehydrolyzed kraft hardwood
is ESTERCELL.TM..
19. The method of claim 12 wherein the prehydrolyzed kraft hardwood
is TYRCELL.TM..
20. The method of claim 12 wherein the prehydrolyzed kraft hardwood
is VISCOCELL.TM..
21. The method of claim 11 wherein the acid hydrolysis step is
carried out with dilute sulphuric acid.
22. The method of claim 11 wherein the acid hydrolysis step is
carried out with dilute hydrochloric acid.
Description
FIELD OF INVENTION
[0001] This invention generally relates to a method for producing
microcrystalline cellulose (or MCC) from a cellulose source
material, and more particularly, to the production of MCC using
never-dried pulp as the cellulose source.
BACKGROUND OF INVENTION
[0002] Microcrystalline cellulose is a well-known material that has
a wide variety of commercial applications, for example in food,
pharmaceutical and cosmetic preparations.
[0003] The traditional and preferred method of producing MCC from
cellulosic materials includes the steps of acid hydrolysis of the
cellulosic material, acid neutralization typically with ammonium
hydroxide, filtering, washing and drying to yield MCC. In the acid
hydrolysis step, the acid removes amorphous cellulose material
leaving a substantially insoluble residue comprising microcrystals
of cellulose, also called cellulose crystalline aggregates and
commonly referred to in the art as MCC, or in earlier publications
as level off degree of polymerization ("LODP") cellulose. O. A.
Battista "Hydrolysis and Crystallization of Cellulose," Industrial
and Engineering Chemistry, 142, pp. 502-507 (1950). The MCC can be
further processed by attrition or other means to produce colloidal
particles or to produce a form suited for a particular end use.
[0004] Many different cellulosic materials have been effectively
used in MCC manufacture, with the most common being wood pulp. Wood
pulp has traditionally been available in sheet form, having been
formed into sheets and dried for ease of storage and transport.
When used to manufacture MCC, such wood pulp sheets must be
shredded or broken apart and rewetted in a mineral acid solution
(hydrolysis) in order to reconstitute a pulp slurry, which is then
used in the MCC producing process. Thus, the traditional process
requires the steps of forming a pulp sheet, drying the pulp sheet,
breaking the pulp sheet apart and re-wetting the pulp sheet.
[0005] U.S. Pat. Nos. 3,141,875, 3,146,168, 3,251,824, 3,278,519
and 3,357,845 to Battista disclose various articles, structures and
pharmaceutical compositions made from cellulosic materials. The
cellulosic material is produced through hydrolysis of a cellulose
ether or a cellulose ester of an organic acid with hydrochloric
acid, followed by mechanical disintegration of the resulting
hydrolyzed, water insoluble crystals in an aqueous medium which can
be neutral or alkaline, to form colloid-forming particles.
[0006] U.S. Pat. No. 2,978,446 to Battista discloses a method for
making MCC which includes hydrolyzing a purified cellulose source
with hydrochloric acid, filtering to remove the hydrolyzed
amorphous cellulose from the crystalline cellulose, mechanically
disintegrating the crystals in an aqueous acidic medium,
neutralizing the acid and washing the resulting cellulose
crystals.
[0007] It is known in the art to utilize never-dried pulp as the
starting material in MCC manufacture via enzymatic hydrolysis with
cellulase. U.S. Pat. No. 5,346,589 to Braunstein discloses a method
of making MCC wherein the cellulose source is never-dried pulp.
However, the never-dried pulp is hydrolyzed with a cellulase enzyme
rather than acid.
[0008] The use of fibrillated never-dried pulp as the starting
material in the manufacture of MCC is also known. U.S. Pat. No.
4,391,973 to Cruz, Jr. discloses a method for making what is
referred to as "a new physical form of cellulose" with properties
that are clearly different than those of MCC. The starting material
is preferably fibrillated never dried pulp and the process is
similar to the known process for MCC manufacture as taught in the
aforementioned '446 patent to Battista, except that the pulp, is
"fibrillated" prior to hydrolysis. This fibrillation, or milling,
of the pulp replaces the mechanical disintegration of the isolated
cellulose crystals as taught in the '446 patent, otherwise the
process is identical: the pulp is added to water and hydrochloric
acid and heated to 104-106.degree. C. for 14-15 minutes, then is
washed, filtered, neutralized and dried.
[0009] U.S. Pat. No. 4,427,778 to Zabriskie discloses a method of
making MCC wherein the cellulose source is hydrolyzed with a
cellulase enzyme. U.S. Pat. No. 5,175,275 to Dobashi discloses a
method for preparing powdery crystalline cellulose by treating a
cellulosic source material with a cellulase, subjecting the
enzyme-treated cellulose material to mild acid hydrolysis, followed
by mechanical disintegration of the hydrolyzed cellulose material.
U.S. Pat. No. 6,037,380 to Venables discloses a method for the
manufacture of colloidal MCC from MCC wherein the MCC is wet-ground
with an attriting aid under high shear high solids mixing
conditions.
[0010] None of the related art provides for a traditional method of
producing MCC using never-dried pulp as the cellulose source
material. It is known that drying causes irreversible changes to
the pulp fibers and reduces the ability of acid to penetrate the
cellulose. (The Effect of Drying Conditions on the Swelling and
Bonding Properties of Bleached Kraft, 2000, Thad C. Maloney and
Hannu Paulapuro, Helsinki University of Technology, PO Box 6300,
FIN-02015 HUT, Finland; Cellulose Cocrystallization in
Hornification of Kraft Pulp, 1996, Roger Newman and Jacqueline A.
Hemmingson, Industrial Research Limited, PO Box 31-310, Lower Hutt,
New Zealand). Since the method of the present invention utilizes
never-dried pulp, said method reduces the time and cost of
producing MCC. Further, because the fiber is never dried and is not
made into sheets, the resulting fiber pulp has reduced fiber
damage.
SUMMARY OF THE INVENTION
[0011] It is therefore an object of the present invention to
provide a method of producing MCC from cellulosic materials,
wherein the cellulose material is never-dried pulp.
[0012] Another object of the present invention is to provide a
method of producing MCC from never-dried pulp, which method
includes the traditional means of hydrolyzing a cellulose source
with a mineral acid.
[0013] Another object of the present invention is to provide a
method of producing MCC from never-dried pulp, wherein the
never-dried pulp is any wood pulp, including but not limited to
prehydrolyzed kraft hardwood, prehydrolyzed kraft softwood,
hardwood sulfite, softwood sulfite, paper-grade softwood or
paper-grade hardwood.
[0014] Another object of the present invention is to provide a
method of producing MCC from never-dried pulp, which method
includes the traditional means of hydrolyzing a cellulose source
with a mineral acid, wherein the mineral acid is hydrochloric acid,
sulfuric acid, phosphoric acid, or nitric acid.
[0015] A further object of the present invention is to provide a
method of producing MCC from fibers that have not been subjected to
heat or thermal energy for drying, thereby reducing the fiber
damage produced through fiber handling in the process of sheet
making and drying.
[0016] Another object of the present invention to reduce production
time and cost by eliminating thermal drying, rolling/baling and
shredding stages from the process of producing MCC.
[0017] Another object of this invention is to provide a method for
producing MCC products which products are comparable in quality and
functionality to existing MCC products and can be adapted for a
variety of uses, including the use of MCC in the manufacture of
various articles.
[0018] Other objects, features and advantages of the present
invention will be apparent when the detailed description of the
preferred embodiments of the invention is considered which should
be construed in an illustrative and not limiting sense as
follows.
DISCLOSURE OF THE INVENTION
[0019] In accordance with a preferred embodiment of the invention,
MCC is produced by subjecting never-dried pulp to acid hydrolysis
and neutralizing the residue of the acid. The recovered cellulose
is then subjected to various treatments in order to form
microcrystalline cellulose. For instance, the pulp is then washed
and dried to form MCC. Since the use of never-dried pulp eliminates
the steps of drying the fiber, forming sheets and then rewetting
the sheets to form a pulp slurry, this method reduces the time and
cost of traditional MCC producing processes. Furthermore, since
thermal drying of the wood pulp causes a collapse of lumen in the
natural wood fibers (fiber hornification), which could lead to poor
accessibility by acid during MCC manufacture, the never-dried pulp
has higher acid accessibility, resulting in reduced processing time
and cost.
[0020] The expression "never-dried" is intended to refer to a
cellulose material that has not been dried using heat or other
thermal energy during or following any type of preliminary
processing after having been harvested. In this case, cellulose
material subjected to mechanical dewatering or pressing that
removes free liquid without the use of heat is considered to be
never-dried pulp. The material may contain lignin and
hemicelluloses. Such materials may include waste fiber or recycled
fiber that is not thermally dried after the de-inking process.
[0021] Traditionally, a very high purity dissolving pulp (with a
low hemicellulose content (<2.0%) and a high R-10 (up to 98%) is
used as the starting material for MCC. In the present invention
wherein never-dried pulp is used in the MCC producing process any
type of wood pulp, regardless of purity may be used.
[0022] In a preferred method of the present invention, the
never-dried pulp fibers may be any dissolving pulp grade including
but not limited to prehydrolyzed kraft hardwood, prehydrolyzed
kraft softwood, hardwood sulfite, softwood sulfite, paper-grade
softwood or hardwood. Examples of prehydrolyzed kraft hardwood
include ESTERCELL.TM., TYRCELL.TM., and VISCOCELL.TM., all of which
are commercially available from International Paper, Chemical
Cellulose Business, 61 Carthage Point Road, Natchez, MIss.
39120.
[0023] Hydrolysis may be effected by various specific methods,
including the use of various mineral acids. Examples of mineral
acids include hydrochloric acid, sulfuric acid, nitric acid and
phosphoric acid. Acid hydrolysis is carried out under traditional
conditions. For instance, never-dried fiber can be subjected to
hydrolysis at an acid concentration of 0.1 to 2.5 normal, a
temperature of about 1 00.degree. C. to 125.degree. C. for about 5
to 25 minutes. Hydrolysis achieves substantially complete removal
the amorphous form of the cellulose starting material and yields
highly crystalline particulate cellulose.
[0024] The recovered cellulose consists essentially of aggregates
of the so-called crystalline cellulose. This cellulose is separated
by filtration and washed free of acid using methods well known in
the art. Preferably, the wash may contain a small amount, about 1%,
of ammonium hydroxide to insure the removal of the acid. The
recovered cellulose is then dried according to methods well known
in the art, for example flash drying or spray drying to form
microcrystalline cellulose.
[0025] The following examples describe the manner and process of
making and using the present invention and set forth the best mode
contemplated by the inventors for carrying out the invention, but
are not to be construed as limiting the invention.
EXAMPLE 1
[0026] Ten (10) grams (OD) of never-dried ESTERCELL.TM. fibers were
placed in a three-necked flask fitted with a mechanical stirrer and
positioned in a heating mantel. Deionised water was added to the
flask to make a slurry having total water content in the reaction
vessel of 634 ml. The slurry was stirred and heated to about
100.degree. C. While stirring, hydrochloric acid (165.6 ml) was
added to the slurry such that the final concentration of the
hydrochloric acid was 2.5N. The temperature of the stirred slurry
was raised to about 106.degree. C. After 15 minutes the heating
mantel was switched off and deionised water (100 ml) was added to
the reaction vessel. The fiber suspension was filtered through a
sintered funnel containing two pre-wetted Whatman #541 filter
papers, washed with deionised water. The cellulose was then
transferred to a 500 ml beaker and approximately 300 ml of
deionised water was added to the beaker. The solution was then
neutralized to pH 7 with ammonium hydroxide (1%). Using a sintered
funnel, the cellulose was rewashed with deionised water (500 ml).
The final slurry was freeze-dried.
EXAMPLE 2
[0027] Example 1 was repeated but the time period for hydrolysis at
about 106.degree. C. was 10 and 20 minutes, respectively.
EXAMPLE 3
[0028] In this example, machine dried ESTERCELL.TM. fibers were
used instead of the never-dried fibers. A pulp slurry of the
machine-dried ESTERCELL.TM. in water was prepared before adding the
acid. All other processing steps remained the same.
EXAMPLE 4
[0029] A three-necked flask fitted with a stirrer and positioned in
a heating mantel was filled with 800 ml of 2.5N hydrochloric acid
and heated up to about 106.degree. C. Then, 10 grams (OD)
machine-dried ESTERCELL.TM. fiber was added to the flask to form an
acid slurry. The slurry was stirred and the temperature of the
stirred slurry was maintained at about 106.degree. C. for 15
minutes. Then, 100 ml of deionised water was added to the reaction
vessel to form a fiber suspension. The fiber suspension was then
filtered through a sintered funnel having two pre-wetted Whatman
#541 filter papers and washed with deionised water. The cellulose
was then transferred to a 500 ml beaker and deionised water was
added to approximately 300 ml. The solution was then neutralized to
pH 7 with ammonium hydroxide (1%) and the cellulose was rewashed
with deionised water (500 ml) using the sintered funnel. The final
slurry was freeze-dried.
EXAMPLE 5
[0030] In this Example, never-dried SOLVEKRAFT.TM. fibers were
used. All processing steps are the same as Example 1.
SOLVEKRAFT.TM. is commercially available from International Paper,
Chemical Cellulose Business, 61 Carthage Point Road, Natchez, Miss.
39120.
EXAMPLE 6
[0031] In this Example, machine-dried SOLVEKRAFT.TM. pulp was used
instead of never-dried SOLVEKRAFT.TM. fibers. All processing steps
were the same as in Example 4.
[0032] The hydrolysis time, and leveling-off degree of
polymerization (LODP) of the MCC powders produced in Examples 1-6
are shown in Table 1. LODP is a property of MCC that is commonly
measured and can indicate product performance. LODP is a
measurement of the number of glucose molecules in the cellulose
chain.
[0033] The LODP value is dependent primarily upon the starting
cellulosic material and to a lesser extent upon the severity of the
hydrolyzing conditions. In general, the LODP of native cellulose
fibers is in the range of between 200 and 300, whereas that derived
from regenerated cellulose lies in the range of from 25 to about
60. Table 1 shows that for the same hydrolysis conditions, the LODP
is higher for never-dried pulps. This provides the manufacturer of
MCC with the added advantage of being able to modify the processing
conditions, for example, decreasing hydrolysis time or acid
concentration for a given temperature to produce the same LODP for
a dried pulp.
1 TABLE 1 CELLULOSE HYDROLYS MATERIAL IS TIME LODP REMARKS EXAMPLE
ESTERCELL .TM. 15 minutes 158 Never-dried 1 Pulp EXAMPLE ESTERCELL
.TM. 10 minutes 160 Never-dried 2 Pulp ESTERCELL .TM. 20 minutes
156 Never-dried Pulp EXAMPLE ESTERCELL .TM. 15 minutes 154 Machine-
3 Dried Pulp EXAMPLE ESTERCELL .TM. 15 minutes 152 Machine- 4 Dried
Pulp EXAMPLE SOLVE- 15 minutes 167 Never-dried 5 KRAFT .TM. Pulp
EXAMPLE SOLVE- 15 minutes 150 Machine 6 KRAFT .TM. Dried Pulp
[0034] Although the invention has been described with reference to
preferred embodiments which should be construed in an illustrative
and not limiting sense, it will be appreciated by one of ordinary
skill in the art that numerous modifications are possible in light
of the above disclosure. For example, different acid strengths or
different acids may be used. There is potential that a weaker acid
is required to hyodrphous cellulose of never-dried fibers as
compared to machine-dried fibers. Further the current pulp making
process may be modified to further reduce production time, chemical
cost saving and yield improvements. All such variations and
modifications are intended to be within the scope and spirit of the
invention.
* * * * *