Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A new pulp and process for pulping
Field of the invention
The present invention is directed to a new pulp, which is derived from
lignocellulosic material subjected for agitation in aqueous tetra-
alkylammonium salt
solution under microwave irradiation. The invention is also directed to a
process for
pulping lignocellulosic material and to a process for softening
lignocellulosic
material.
Background art
Pulp
Pulp is the raw material for the production of paper, paperboard, fiberboard,
and
similar manufactured products. In purified form, it is a source of cellulose
for rayon,
cellulose esters, and other cellulose derived products.
Pulp is obtained from plant fiber and is, therefore, a renewable source.
Fibrous
plants have been used a source for writing materials, eg. papyrus, since the
earliest
Babylonian and Egyptian civilizations. The origin of papermaking, which is the
formation of cohesive sheet from the rebonding of separated fibers, has been
attributed to Ts'ai-Lun in China in 105 AD, who used bamboo, mulberry bark,
and
rags. The use of wood as a source of papermaking was not commercially applied
until the mid-1800s. The principal wood-pulping processes in use today, eg,
the
groundwood, soda, S02, or acid sulfite, and the sulfate or kraft processes
were
developed in 1844, 1853, 1866 and 1870, respectively. Since their development,
the
basic processes have been modified and adapted and the technology has been
highly
refined.
As with most industries, the environmental and energy concerns of the 1970s
effected large changes in the operation of pulp and paper mills as well as
much
research effort to develop the most energy-efficient and cleanest methods for
the
production. In most cases, the practical result for the short term has been
add-on
methods, eg. scrubbers, precipitators, holding ponds, etc, which minimize the
discharge off effluents. Other trends have been the increasing use of high
yield
pulps by modifying the ground wood processes to improve pulp quality, the use
of
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more of the tree in harvesting and chipping, and elimination or minimization
of
malodorous sulfur compounds in pulping and the toxic and corrosive chlorine
compounds from bleaching.
Before pulping processes, the wood material is treated by harvesting, barking,
chipping and screening processes. The purpose of chipping for pulping is to
reduce
the wood to a size that allows penetration and diffusion of the processing
chemicals
without excessive cutting or damage to fibers. The chips, which are ca 20 mm
long,
are fairly free-flowing and can be transported pneumatically or on belts and
then
stored in piles or bins, Kirk-Othmer, Encyclopedia of Chemical Technology, 3
rd
edition, pages 379-391.
The present pulps can be subdivided into mechanical and chemical pulps.
Said mechanical pulps are subdivided into groundwood pulp, thermomechanical
pulp (TMP) and chemithermomechanical pulp (CTMP). Groundwood pulp is
prepared by pressing wet wood against a wetted rotating grindstone, with the
axis of
the wood parallel to the axis of the wheel. Temperatures in the immediate
grinding
zone can be 180-190 C. The movement of the water and the removal of pulp
controls and dissipates the heat, thus preventing charring of the wood
material.
After such treatment, the groundwood pulp contains a considerable proportion
of
(70-80 wt-%) of fiber bundles, broken fibers, and fines in addition to the
individual
fibers. The fibers are essentially wood with the original cell-wall lignin
intact. They
are, therefore, very stiff and bulky and do not collapse like the chemical-
pulp fibers.
Since groundwood pulps are obtained in yields of ca 95%, their cost is
relatively
low. The main direct cost other than wood is power, which is ca 49-75 kJ (11,7-
17,9
kcl)/ton for normal paper grades.
Thermomechanical pulp (TMP) is prepared by presteaming the wood chips to 110-
150 C in order to make them malleable. A thermoplasticization of the wood
occurs
when it is heated above the glass transition point of wet lignin. When these
chips
are fiberized in a refmer at high consistency, whole individual fibers are
released;
separation occurs at the middle lamella and a ribbonlike material is produced
from
the S1 layer of the cell wall. The amount of fibrillization depends on the
refining
conditions and is critical to the properties of the pulp. This material has a
high light-
scattering coefficient, although it is lower than that of groundwood, and is
highly
flexible, which gives good bonding and surface smoothness to the paper. The
increased proportion of long fibers improves the tearing properties of TMP-
pulps,
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but the fibers in this fraction are stiff and contribute little to bonding.
There is much
less fiber fragmentation than in groundwood pupls.
Chemithermomechanical pulp (CTMP) is prepared in the same manner as TMP but
the chips are pretreated by a mild treatment with sodium sulfite at pH 9-10.
In the
process, the chips are impregnated with the chemicals, steamed to 130-170 C
and
subsequently, refined. The yield is 90-92%, which is 2-3% lower than in TMP. A
range of properties can be obtained by adjusting processing variables but in
general,
CTMP pulp has greater long-fiber fraction and lower-fines fraction than a
comparable thermomechanical pulp. The intact fibers are more flexible than TMP
fibers and, consequently, better shhet-forming and bonding properties are
obtained.
CTMP pulping is reported to be particularly suitable for pulping high-density
hardwoods.
In chemical pulping, sufficient lignin is dissolved from the middle lamella to
allow
the fibers to separate with little, if any, mechanical action. However, a
portion of the
cell-wall lignin is retained in the fiber, and an attempt to remove this
during
digestion would result in excessive degradation of the pulp. For this reason,
ca 3-4
wt-% of lignin is normally left in hardwood chemical pulps and 4-10 wt-% is
left in
softwood chemical pulps. The lignin is subsequently removed by bleaching in
separate processing if completely delignified pulps are to be manufactured.
The concentration of the cooking liquor in contact with the wood influences
the rate
of delignification. Because the time required for diffusion of the chemical
through
the wood structure and the depletion of the reagent concentration as it
penetrates the
chip, delignification proceeds more slowly at the center of the chip. In order
to
prevent overcooking of the principal portion of the pulp, digestion is
normally
halted before the centers of the larger chips are adequately delignified. The
resultant
pulp thus contains a portion of nondefibered wood fragments, which are
separated
by screening and returned to the digester or fiberized mechanically.
The dominant chemical wood-pulping process is the kraft or sulfate process.
The
alkaline pulping liquor or digesting solution contains about 3 to 1 ratio of
sodium
hydroxide and sodium sulfide. The name kraft, which means strength in German,
characterizes the stronger pulp produced when sodium sulfide is included in
the
pulping liquor, compared with the pulp obtained if sodium hydroxide alone is
employed, as in the original soda process. The alternative term, ie, the
sulfate
process is derived from the use of sodium sulfate as a makeup chemical in the
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recovery process. Sodium sulfate is reduced into sodium sulfide in the
recovery
furnace by organic-derived carbon.
Solutions of sodium sulfide and sodium hydroxide are in equilibrium:
H20 + Na2S NaHS + NaOH
Aqueous sodium sulfide is therefore a source of hydroxide ions and must be
considered in adjusting the chemical charge. A system has been developed in
the
North American industry to put sodium hydroxide and sodium sulfide on an
equivalent basis by expressing them both as their equivalent weight to sodium
oxide, Na20. The percent of sodium sulfide in the mixture, when both Na2S and
NaOH are expressed as Na20, is known as the sulfidity. The chemical charge,
liquor composition, time of heat-up and time and temperature of reaction are
functions of the wood species or species mix being digested and the intended
use of
the pulp. A typical set of conditions for southern pine chips in the
production of
bleachable-grade pulp for fine papers is active alkali 18%; sulfidity 25%;
liquor to
wood-ratio 4:1; 90 minutes at 170 C in the top heating zone and 90 min at 170
C
in the second zone. Hardwoods require less vigorous conditions primary because
of
the lower initial lignin content.
Although the kraft process is a highly developed, adaptable, and efficient
process,
there are some problems and disadvantages for its use. Efforts are being made
in
individual mills to minimize energy, water, and chemical requirements.
Additionally, there are two problems inherent in the chemistry of the process,
namely low carbohydrate yield and the formation of malodorous organic sulfur
compounds.
One modification to the kraft process that is being applied commercially is
the
polysulfide process. When elemental sulfur is added to a solution of sodium
sulfide
and sodium hydroxide, the sulfur dissolves and forms a mixture of complexes
with
the general formula NaaSx (where x is 2-5, depending on the equilibrium
conditions
and how much sulfur is added). Sulfur Na2Sx is an oxidizing agent, which,
under the
conditions of lcraft pulping, converts the hemiacetal function to a relatively
alkali-
stable aldonic acid. The increase in yield in polysulfide process is
proportional to
the amount of added sulfur to ca 10% based on wood.
One additional pulping method is sulfite pulping. In the original sulfite
pulping
process, wood was pulped with an aqueous solution of SO2 and lime. Calcium
sulfite has very limited solubility above pH 2, and excess of SOZ gas was
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maintained in the digester in order to keep the pH below said level. Thus, the
process can be contrasted with the kraft or soda processes as being an acid
process.
Currently, bases other than calcium are used with SO2 solutions, and sulfite
pulping
refers to a variety of processes in which the full pH range is utilized for
all or part of
the pulping. Magnesium, sodium, and ammonia are used as alternatives to
calcium.
Magnesium sulfide has decreasing solubility above pH 5, but sodium and
ammonium sulfites are soluble at pH 1-14.
In addition to previously discussed pulping methods there are some
semichemical
pulping methods. The distinctions between semichemical and high yield chemical
processes are very small and are more a matter of gradation between the
mechanical
and full chemical processes. A semichemical process is essentially a chemical
delignification in which the chemical processes are stopped at a point where
mechanical treatment is necessary to separate fibers from partially cooked
chips.
Any known chemical process can be used to produce semichemical pulp. The
pulps,
although less flexible, resemble chemical pulps more than mechanical pulps
because they are not dependent on rupture of the fiber wall for bonding. The
yield is
60-85% with a lignin content of 15-20%. The lignin is concentrated on the
fiber
surface.
Microwaves
It is known from the recent literature concerning organic synthesis that the
reaction
times of the organic reactions are remarkable reduced when the energy
necessary
for the occurrence of the reaction is introduced to the system by using
microwave
irradiation. The commonly used frequency for microwave energy is 2.45 GHz.
There is a wide and continuously increasing literature available in the area
of using
microwave techniques in organic synthesis. An example of a short summary
article
of this topic was published by Mingos in 1994 (D. Michael P. Mingos;
"Microwaves
in chemical synthesis" in Chemistry and industry 1. August 1994, pp. 596-599).
Loupy et. al. have recently published a review concerning heterogenous
catalysis
under microwave irradiation (Loupy, A., Petit, A., Hamelin, J., Texier-
Boullet, F.,
Jachault, P., Mathe, D.; "New solvent-free organic synthesis using focused
microwave" in Syntlaesis 1998, pp. 1213-1234). Another representative article
has
been published by Strauss (C.R. Strauss; "A combinatorial approach to the
development of Environmentaly Benign Organic Chemical Preparations", Aust. J.
Clzetn. 1999, 52, p. 83-96).
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Microwaves in mechanical pulping
Patent CA 2008526 discloses manufacturing of pulps using microwave heating of
impregnated lignocellulosic material. The impregnation is conducted with state
of
the art pulping liquor (Na2SO3-solution) in the presence of catalysts and
chelating
agent. The impregnation of said chemicals is followed by irradiation of
resulting
material in a microwave-transparent digester. This is followed by a separate
mechanical refining step. The main advantage of microwave treatment is the
reduction of cooking time and consumed energy.
Scott et al. (TAPPI Fall Technol. Trade Fair, pp. 667-676) have reported a
process
for "microwaving logs for energy savings and improved paper properties for
mechanical pulps". The treatment was conducted as a pretreatment for
mechanical
pulping without any impregnation of additional chemicals. The energy
consumption
in subsequent mechanical pulping was decreased up to 15% for the highest
employed power level. Apparently, the wooden material was softened by the
rapid
evaporation of water and thus, rapid rupture of the lignocellulosic material.
Microwaves in dissolution of wood and cellulose
FI20031156 discloses a microwave-assisted method to dissolve lignocellulosic
material in ionic liquids. The dissolution is complete and can be adapted to
any kind
of lignocellulosic materials, including soft- and hard wood. The dissolution
must be
conducted in substantial absence of water. The dissolved material components
can
be separated from the resulting ionic liquid solution.
Rogers et al. published in 2002 a method for dissolution of pure cellulose
fibers into
ionic liquids in the microwave field (Swatloski, R.P.; Spear S.K.; Holbrey,
J.D.;
Rogers, R.D. Journal of American Chemical Society, 2002, 124, p. 4974-4975).
Also here, the dissolution must be conducted in substantial absence of water.
Other non-derivatizing organic solvents for cellulose are widely described in
"Conlprehensive Cellulose Chemistry, Volume 1, Wiley-VCH, page 59-67.
Amongst other, aqueous solutions of different tetra-alkylammonium hydroxides
have been proved to be efficient solvents for cellulose. A complete
dissolution is
achieved readily. Since water is always present in excess volumes, said
solvents are
not practical in derivatization of cellulose.
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Summary of the invention
Pulping is a significant and one of the most energy consuming industries in
the
world. Due to the climate change, continuously growing population, and thus
energy consumption, there is a great demand for new, energy-efficient
production
technologies in all fields of industry. In pulping, elimination or
minimization of
malodorous sulfur compounds would be an additional asset.
It is an object of this invention to provide a new pulp material.
Another object of this invention is to provide a process for pulping
lignocellulosic
material.
A further object of this invention is to provide a process for softening the
lignocellulosic material.
Further objects will become apparent from the following description and
claims.
It is known that cellulose can be completely dissolved in said aqueous tetra-
alkylammoniumhydroxide solution. It is also known that wood can be dissolved
in
ionic liquids in substantial absence of water.
When conducting tests to dissolve cellulose in wood material into aqueous
tetra-
alkylammonium hydroxide solution in microwave field, it was surprisingly found
that it was not the cellulose but the lignin in wood material that was
dissolved in salt
solution.
Unexpectedly, the agitation could be conducted in a manner wherein a complete
to
substantial delignification took place and cellulose remained intact as
bunches of
fine, long fibers. The present invention accomplishes a new kind of pulp and
process for preparing it.
By tuning the salt concentration and agitation time, the delignification could
be
avoided and simultaneously, the wood material was dramatically softened.
Both in delignification (pulping) and in softening of lignosellulosic
materials,
surprisingly short treatment was required in order to achieve said results.
The
lignosellulosic material such as wood could be either delignificated or
softened
already after one minute's agitation in microwave field.
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Detailed description of the invention
According to the invention there is provided a new pulp, which pulp is derived
from
lignocellulosic material subjected for agitation in aqueous tetra-
alkylammonium salt
solution under microwave irradiation.
The agitation can take place with or without stirring of lignocellulosic
material in
said solution.
The lignocellulosic material can be virtually any kind of lignocellulosic
material.
The primary source of fiber for pulp is wood, such as softwood and hardwood.
Other sources include straws, grasses and canes. Pulp fibers can be
principally
extracted from any vacular plant found in nature, also nonwood sources such as
straws, grasses, eg, rice, esparto, wheat and sabai; canes and reeds, eg,
primarily
bagasses or sugar cane; several varieties of bamboo; bast fibers, eg, jute,
flax, kenaf,
linen, ramie, and cannabis; leaf fibers, eg agaba or manila hemp and sisal.
Preferably lignocellulosic material is wood, such as softwood and hardwood.
The lignocellulosic material can be in its original form as found in nature,
or it can
be partially processed. In one preferred embodiment of the invention, the
lignocellulosic material consists of wood chips, i.e. the lignocellulosic wood
material has been subjected into barking and chipping before agitation of said
material in aqueous tetra-alkylammonium salt solution under microwave
irradiation.
The lignocellulosic material can pre-treated by impregnating water or said
aqueous
tetra-alkylammonium salt solution into lignocellulosic material.
The content of tetra-alkylammonium salt in aqueous tetra-alkylammonium salt
solution can be 1-75 wt-%, preferably 5-60 wt-% and most preferably 10-40 wt-
%.
The cation of of the tetra-alkylammonium salt is
Ri
R4-N-RZ
R '3
wherein R1, RZ, R3 and R4 are independently a C1-C30 alkyl, C3-C8 carbocyclic
or
C3-C8 heterocyclic group and the anion of the salt can be halogen,
pseudohalogen,
perchlorate, C1-C6 carboxylate or hydroxide.
Preferably, the anion is chloride or hydroxide, most preferably the anion is
hydroxide.
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An especially preferred preferred tetra-alkylammonium salt is the salt wherein
Rl,
R2, R3 and R4 are independently C4 alkyl and anion of the salt is hydroxide.
When miscible with water, also other organic ionic compounds can be employed
as
a salt component when agitating lignocellulosic material under microwave
irradiation according to the invention. A variation of such ionic compounds,
known
as ionic liquids is described in FI20031156.
The agitation can be carried out at a temperature between 40 C and 270 C,
preferably at a temperature between 70 C and 210 C, and most preferably
between
120 C and 190 C.
It is also possible to apply pressure when subjecting lignocellulosic material
for
agitation in aqueous tetra-alkylammonium salt solution under microwave
irradiation. VYhen applied, the pressure is preferably below 20 Bar, more
preferably
below 10 Bar and most preferably between 2 Bar and 9 Bar.
The agitation time can vary between 1 minute to 24 hours, depending on the
employed salt and concentration thereof, nature and concentration of
lignocellulosic
material, on the agitation temperature as well as possibly applied pressure.
The pulp according to the invention can be employed as material for the
production
of paper, paperboard, fiberboard, and similar manufactured products
According to the invention there is also provided a process for pulping
lignocellulosic material, in which process the lignocellulosic material is
subjected
for agitation in aqueous tetra-alkylammonium salt solution under microwave
irradiation in order to establish partial or complete delignification.
In the pulping process, the agitation can take place with or without stirring
of
lignocellulosic material in said solution.
The lignocellulosic material can be virtually any kind of lignocellulosic
material.
The primary source of fiber for pulp is wood, such as softwood and hardwood.
Other sources include straws, grasses and canes. Pulp fibers can be
principally
extracted from any vacular plant found in nature, also nonwood sources such as
straws, grasses, eg, rice, esparto, wheat and sabai; canes and reeds, eg,
primarily
bagasses or sugar cane; several varieties of bamboo; bast fibers, eg, jute,
flax, kenaf,
linen, ramie, and cannabis; leaf fibers, eg agaba or manila hemp and sisal.
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Preferably, the employed lignocellulosic material is wood, such as softwood
and
hardwood.
The lignocellulosic material can be in its original form as found in nature,
or it can
be partially processed. In one preferred embodiment of the invention, the
lignocellulosic material consists of wood chips, i.e. the lignocellulosic wood
material has been subjected into barking and chipping before agitation of said
material in aqueous tetra-alkylammonium salt solution under microwave
irradiation.
The lignocellulosic material can pre-treated by impregnating water or said
aqueous
tetra-alkylammonium salt solution into lignocellulosic material.
In the pulping process, the content of tetra-alkylammonium salt in aqueous
tetra-
alkylammonium salt solution can be 1-75 wt-%, preferably 5-60 wt-% and most
preferably 10-40 wt-%. The cation of of the tetra-alkylammonium salt is
R'
i+
R4-N-R2
R3
wherein R1, R2, R3 and R4 are independently a C1-C30 alkyl, C3-C8 carbocyclic
or
C3-C8 heterocyclic group and the anion of the salt can be halogen,
pseudohalogen,
perchlorate, Cl-C6 carboxylate or hydroxide.
Preferably, the anion is chloride or hydroxide, most preferably the anion is
hydroxide.
An especially preferred preferred tetra-alkylammonium salt in the pulping
process
is said salt wherein R1, R2, R3 and R4 are independently C4 alkyl and anion of
the
salt is hydroxide.
When miscible with water, also other organic ionic compounds can be employed
as
a salt component when in the pulping process according to the invention.
Applicable compounds are exemplified in FI20031156.
In the pulping process according to the invention, the agitation can be
carried out at
a temperature between 40 C and 270 C, preferably at a temperature between 70 C
and 210 C, and most preferably between 120 C and 190 C.
It is also possible to apply pressure when subjecting lignocellulosic material
for
agitation in aqueous tetra-alkylammonium salt solution under microwave
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irradiation. When applied, the pressure is preferably below 20 Bar, more
preferably
below 10 Bar and most preferably between 2 Bar and 9 Bar.
The agitation time can vary between 1 minute to 24 hours, depending on the
employed salt and concentration thereof, nature and concentration of
lignocellulosic
material, on the agitation temperature as well as possibly applied pressure.
In pulping process according to the invention, it is advantageous to choose
said
parameters in a manner that delignification of lignocellulosic material is
partial or
complete.
The pulped lignocellulosic material can be employed as material for the
production
of paper, paperboard, fiberboard, and similar manufactured products
According to the invention there is further provided a process for softening
lignocellulosic material, in which process the lignocellulosic material is
subjected
for agitation in aqueous tetra-alkylammonium salt solution under microwave
irradiation.
In the softening process, the agitation can take place with or without
stirring of
lignocellulosic material in said solution.
In said softening process, the lignocellulosic material can be virtually any
kind of
lignocellulosic material. The primary source of fiber for pulp is wood, such
as
softwood and hardwood. Other sources include straws, grasses and canes. Pulp
fibers can be principally extracted from any vacular plant found in nature,
also
nonwood sources such as straws, grasses, eg, rice, esparto, wheat and sabai;
canes
and reeds, eg, primarily bagasses or sugar cane; several varieties of bamboo;
bast
fibers, eg, jute, flax, kenaf, linen, ramie, and cannabis; leaf fibers, eg
agaba or
manila hemp and sisal.
Preferably, the employed lignocellulosic material is wood, such as softwood
and
hardwood.
The lignocellulosic material can be in its original form as found in nature,
or it can
be partially processed. In one preferred embodiment of the invention, the
lignocellulosic material consists of wood chips, i.e. the lignocellulosic wood
material has been subjected into barking and chipping before agitation of said
material in aqueous tetra-alkylammonium salt solution under microwave
irradiation.
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The lignocellulosic material can pre-treated by impregnating water or said
aqueous
tetra-alkylammonium salt solution into lignocellulosic material.
In the softening process according to the invention, the content of tetra-
alkylammonium salt in aqueous tetra-alkylammonium salt solution can be 1-75 wt-
%, preferably 5-60 wt-% and most preferably 10-40 wt-%. The cation of of the
tetra-alkylammonium salt is
Rl
i+
R4-N-R2
R3
wherein R1, R2, R3 and R4 are independently a C1-C30 alkyl, C3-C8 carbocyclic
or
C3-C8 heterocyclic group and the anion of the salt can be halogen,
pseudohalogen,
perchlorate, C1-C6 carboxylate or hydroxide.
Preferably, the anion is chloride or hydroxide, most preferably the anion is
hydroxide.
An especially preferred preferred tetra-alkylammonium salt in the softening
process
is said salt wherein Rl, R2, R3 and R4 are independently C4 alkyl and anion of
the
salt is hydroxide.
When miscible with water, also other organic ionic compounds can be employed
as
a salt component when in the pulping process according to the invention.
Applicable compounds are exemplified in FI20031156.
In the softening process according to the invention, the agitation can be
carried out
at a temperature between 40 C and 270 C, preferably at a temperature between
70 C
and 210 C, and most preferably between 120 C and 190 C.
It is also possible to apply pressure in the softening process according to
the
invention. When applied, the pressure is preferably below 20 Bar, more
preferably
below 10 Bar and most preferably between 2 Bar and 9 Bar.
The agitation time can vary between 1 minute to 24 hours, depending on the
employed salt and concentration thereof, nature and concentration of
lignocellulosic
material, on the agitation temperature as well as possibly applied pressure.
In softening process according to the invention, it is advantageous to choose
said
parameters in a manner that lignocellulosic material is only softened, not
pulped.
Accordingly, no substantial delignification takes place during the softening
process
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according to the invention. The lignocellulosic material structure is ruptured
and
impregnated with aqueous tetra-alkylammonium salt solution in a manner where
the
energy and/or chemical consumption in subsequent processing steps is
decreased.
The softened lignocellulosic material can be employed as material for the
production of paper, paperboard, fiberboard, and similar manufactured
products.
The present invention accomplishes a new pulp, which can be manufactured in a
rapid and energy efficient manner. The degree of delignification is tunable
and
resulting pulp is of high quality consisting of fine, long fibers. The present
also
accomplishes a process for softening lignosellulosic material. Said softened,
malleable material can then be processed further in a more energy efficient
manner.
Accordingly, the present invention results in lower energy consumption and
thus,
environmental benefits. Also formation of malodorous organic sulfur compounds
is
avoided. The employed tetra-alkylammonium salt is a relatively cheap chemical,
which is preferably recycled.
Examples
The following examples describe the invention without limiting said invention
into
examples. In examples 1-10, treated lignosellulosic material were sticks of
Finnish
softwood cut from 20 mm long wood chips. The sticks were cut parallel to wood
lamellas in order to facilitate long fibers. The original reason to cut the
sticks was
the restricting size of the microwave reactor, namely 5 ml.
Example 1
Treatment of softwood in 40% aqueous tetrabutylammonium hydroxide in
microwave field - 5 minutes at 170 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 40%
tetrabutylammonium hydroxide solution and agitated for 5 minutes at 170 C in
a
sealed reactor tube equipped with magnetic stirring bar.
The agitation resulted in dark brownish solution comprising long fiber fines.
Washing with water gave both bunches of detaches pale beige fibers as well as
completely separate fibers.
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Example 2
Treatment of softwood in 20% aqueous tetrabutylammonium hydroxide in
nzicnowave field - 5 minutes at 170 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 20%
tetrabutylammonium hydroxide solution and agitated for 5 minutes at 170 C in
a
sealed reactor tube equipped with magnetic stirring bar.
The agitation resulted in dark brownish solution comprising long fiber fines.
Washing with water gave both bunches of detaches pale beige fibers as well as
completely separate fibers. The pulp composition was slightly more intact
compared
to that of example 1.
Example 3
Treatment of softwood in 10% aqueous tetrabutylammonium hydroxide in
microwave field - 5 minutes at 170 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 10%
tetrabutylammonium hydroxide solution and agitated for 5 minutes at 170 C in
a
sealed reactor tube equipped with magnetic stirring bar.
The agitation resulted in dark brownish solution comprising long fiber fines.
Washing with water gave both bunches of detaches pale beige fibers and the
pulp
composition more intact compared to that of example 2.
Example 4
Treatrnent of softwood in 10% aqueous tetrabutylammonium hydroxide in
microwave field - 30 minutes at 170 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 10%
tetrabutylammonium hydroxide solution and agitated for 30 minutes at 170 C in
a
sealed reactor tube equipped with magnetic stirring bar.
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The agitation resulted in dark brownish solution comprising long fiber fines.
Washing with water gave both bunches of detaches pale beige fibers and the
pulp
composition resembled to that of example 1.
Example 5
Treatment of softwood in 40% aqueous tetnabutylammonium hydroxide in
microwave field - 5 minutes at 120 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 40%
tetrabutylammonium hydroxide solution and agitated for 5 minutes at 120 C in
a
scaled reactor tube equipped with magnetic stirring bar.
The agitation resulted in dark brownish solution comprising long fiber fines.
Washing with water gave both bunches of detaches pale beige fibers as well as
completely separate fibers. The pulp composition resembled to that of example
2.
Example 6
Treatnzent of softwood in 5% aqueous tetrabutylammonium hydroxide in microwave
field - 5 minutes at 120 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 5%
tetrabutylammonium hydroxide solution and agitated for 5 minutes at 120 C in
a
sealed reactor tube equipped with magnetic stirring bar.
The agitation resulted in brownish solution comprising some wooden sticks and
long fiber fines. Washing with water gave dramatically softened sticks of
wood,
some fines detached from said sticks.
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Example 7
Treatnaent of softwood in 40% aqueous tetyabutylammonium hydroxide in
microwave field - 5 minutes at 80 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 40%
tetrabutylammonium hydroxide solution and agitated for 5 minutes at 80 C in a
sealed reactor tube equipped with magnetic stirring bar.
The agitation resulted in brownish solution comprising some wooden sticks and
long fiber fines. Washing with water gave dramatically softened and partially
detached sticks of wood, some fines being also detached from said sticks.
Example 8
Treatment of softwood in 10% aqueous tetrabutylammonium hydroxide in
microwave field - 30 minutes at 80 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 10%
tetrabutylammonium hydroxide solution and agitated for 30 minutes at 80 C in
a
sealed reactor tube equipped with magnetic stirring bar.
As in example 7, the agitation resulted in brownish solution comprising some
wooden sticks and long fiber fines. Washing with water gave dramatically
softened
and partially detached sticks of wood, some fines being also detached from
said
sticks.
Example 9
Treatment of softwood in 10% aqueous tetrabutylammonium hydroxide in
mict=owave field -1 hour at 70 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 10%
tetrabutylammonium hydroxide solution and agitated for 1 hour at 70 C in a
sealed
reactor tube equipped with magnetic stirring bar.
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Here, the agitation resulted in transparent, pale brownish solution comprising
some
wooden sticks. Washing with water gave dramatically softened and partially
detached sticks of wood.
Example 10
Comparative tneatment of softwood in 40% sodium hydroxide (NaOH) in
microwave field - 5 minutes at 170 C
Approximately 750 mg of softwood sticks were mixed into 4,5 ml of aqueous 40%
sodium hydroxide (NaOH) solution and agitated for 5 minutes at 170 C in a
sealed
reactor tube equipped with magnetic stirring bar.
Here, the agitation resulted in destruction of fiber material giving slimy,
brownish
pieces of organic material with non-fibrous properties.
Example 11
Comparative treatment of softwood in 40% aqueous tetrabutylammonium hydroxide
without micNowave field
Approximately 2000 mg of softwood sticks were mixed into 12 ml of aqueous 40%
retrabutylammonium hydroxide (NaOH) solution and agitated for overnight at 95
C in a flask equipped with magnetic stirring bar.
Also here, the agitation resulted in destruction of fiber material giving
slimy,
brownish pieces of organic material with non-fibrous properties.
