Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ w~g3,25~84 21~ 3 P~T/~93/~516~
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PROCESS FOR ACTIVATION OF CELLULOSE , ~;
This invention relates to a process for activation `
of cellulose~wherein the cellulose is sub~ected to high
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agitation for a short periad of time~
T ~ .u~a~ ` e 54 CellUl^5Q a~QtZtQ b~in~ina
with wood pulp, the wood pulp is ~ypically supplied to l~ ;
the manufacturer in ~he form of a re}atively dense sheet
~ ~ 2~ ~h` ~ n c_=~___ ~__ ~_ ~ a ~____ _SSQd
into bales. The wood pulp does not readily disinteyrate
to form a composition capable or under yoing acetylation '~
and therefore the sheets of wood pulp must be prepared ~.
.for the acetyl~ition step in a prior step typically ~.
rererred to as 'tactivation". l~.
In accordanc2 with methods well known in the art, .
the ac.i~Jatio~ step can ~2 ~ u_~2d:~y ~.ech~nic_lly
sub~dividing tAe sheet of wood pulp a~d then conkact~ng ~1.
: the units of sub-divided wood pulp with acetic materials
~r a: ~2r;~: Q~ ti~e. .j;~
; Although the activa~ion proces~es of t~e pri~r art l:
are effective~in producing a composition which can be l.:
satisfactorily acetylated, these processes require .
~25 relatively long pe~iods of time. For:example, the ~:~
activation processes of the prior art typically require
times of several hours and or~en require times or more
~:th~ 2 hours. Due to the time ~alue of:capital, it
wou}d be very desirable to reduce the time required to '''.','!':'
conduc~ the activation process. ..
We have now discovered a process for the acti~ation
: of cellulose which can be conduc~ed in an extremely ~,
: ch¢rt ~eriod o time comDared to the procqsses of the
: prior art.~ We have accomplished the objective of
conducting the activation process in a very short time ~.
by subjecting the activation composition to a very high
rate of agitation.
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In summary, our invention can be thought of as ';
: ~ a process comprising ':
~ (A) introducing cellulose and water into an i~:.
; activation zone, ' "::: 5 ~B) introducing acetic acld and a catalyst into i,
the activatiQn æo~
: (C) subjecting the cellulose, wa~er, acetic acid
, . . .
: and catalyst to an agitation in the range of
~ ~ - ~3 4~ OW~-I ~ 2~ ~5'~-~ ~r~
combined weight o~ the first and second
streams for a period of time of less than 10
: seconds. .~Theiwood pulp, o~ten call~d cellulose, which is ;:
: useful in our process can comprise any or ;the wood pulps
typically sold in the trade. :Speci$ic examples of ,~:
suitable cellulose:include so~thern and Canadian 1.
hardwoods and so~twoods.
The units of cellulose sheet must have a cross
sectional diameter of le5s th~t 2 ~h~ hi5 ~ h~
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20~ ~accomplished by me~hznically sub-dividing the sneet of
cellulose into:units of this size by meth~ds well known
; in tne ar~, such~as a hammer mill.
The amount of ce}lulose which is:introduced into ~:~
:: the~activation zone is broadly~in the range of 1 to 60
;25~ w ~ er~en~, prereraDly in the range:o~ 30 to 55
weight percent, based on the co~bined weight o~ t_e ''"~'
: ::celluloser water, acetic acid and catalyst. ;.
: The céllulose can be introduced into the activationzone by donventional means such as allowing the
30 : cellulose units to fall under the in~luen~e of gravity
from the means to su~-di~ide the units into
activation 20ne. Pre~erably, the cellulose is~sub-
:~ ~ : divided in a hammer mill and the unit~:of:sub-divided~ .
cellulose are allowed to ~all from the exit of the f
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hammer mill into the en~ry port of the apparatus used to ..
perform the high agitation.
The amount of water in the which is introduced into
the activation zone is broadly in the range of 0 to g9
weight pexcent, preferable in the range of 2 to 20
cellulose, water, acetic acid and catalyst.
The water is introduced into the activation zone .~.
U,inC C;~ Je.. l,i::~ai ~ n ~ e~a 1J 3PinY ::~?2- U... ~e- j
pressure.
The ~irst step of the process of this invention has
been described as in~roducing a first stream of both ,.
cellulose and water into the activation zone. While the
pr~ferred emDodiment is for both the cellulose and wa~er i.
~o be c~ined ~nto one st_ez~ it is fully w~th~n the i,.
scope o- t~.e:invention far the ceilulose and wa~er ~o be
introduced into the actiuation zone as ~eparate streams. ;:
The acetic acid use~ul in the ~econd step of the
~ce~ ~f t h~s nuen~i~n is the tv~e t~icallv used in
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the prepaxation oî celiulose acetate and is well known
in the art. Preferably glacial acetic acid is used. I'~
;~ : The catalyst useful in the second step of the
process of this invention can be methane ~ulfonic acid,
methane disulfonic acid, sulfoac2tic acid, sulfuryl
chloride or sulfuric acid. P~eferably the catalyst is
_~f"-'~ ac~ a~d ~s~e Fr~ y LS ~% s~ u~ic acid.
The acetic acid and cataIyst are introduced into
the activation zone using conventional means, preferably
being pumped under pressure.
: . 30 The serond step of the process o~ this invention
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dQscxibed æs ~ntroducin a second stream of
: both acetic acid and catalyst into the acti~ation zone.
While the p~eferred embodiment is for the acetic acid
. and catalyst to be com~ined into one stream it is fully
within the scope of the invention for these materials to
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be introduced into the activa~ion zone as separate
streams. ~;
The amount of acetic acid is broadly in the range 1.
of 1 ko 99 weight percent, preferably in the range sf 30 i.
to 50 weiyht percent, based on the combined weight of
th_ c~ lc,c, -~at r, a~z~ic ~cld and ca~alyst~
The amount of catalyst is broadly in the range of . .....
0.2 to 6 weight.percent, preferably in the ra~ge of 1 to~:
3 -~ei~ pe_cen-, ~zsea n t:~_ c^~inl-d ~e~ c~
cellulose, water, acetic acid and catalyst.
Th~ process of this in~ention can be operated
: ei~her as a batch process or a continuous process. ::
Preferably, the process in operated as a continuous
: process. ;:'
This inv~ntion has been described in terms or ~irst ..
introducing the~stream of cellulose ~nd water into the ;i;
activation zone and then introducing the stream of
acetic acid and catalyst Lnto the activaticn ~on_.
r~ k~~, t~.~ r-~~~S~ e~a~ ~m~sly ~nd ,~
bo~h~oî ~hese streams are introduced into the activation
: zone simultaneousl~ he proc~s is pr2r iced cn 2
batch basis, the streams can be introduced in any ord~r
: or can be introduced simultaneously.
Agitation of the activation composition is a
critical ~eature o~ this invention. In thls invention, ~'
~G ~ icn co3pcsi~ion i5 as~tated within a
particular range. The range is expressed in ~2rms of
the requirement;for elestrical energy to mechanically
. perform ~he agitation and is broadly in the range of ~:~
~:: 3Q 0.04 to 4.0 kilowatts per pound, preferably 0.1 tG 1 '
cw~s pe- po~n~, of thr cs.~k~nPd weight oE
: cellulose, water, acetic acid and catalyst.
Mechanical pparatus required to achieve this rate
of agi~ation is well known in the art and is
commercially ava~lable. Since a mixing function is
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inevitably associated with the high rate of agitation, '
this apparatus is often re~erred to as a "mixer". :~
Specifically, the apparatus is often called a high ~:
consistency mixer by those ~killed in the art.
Pre~erably the apparatus is a Model 48 Micar High
Con5is ~ency mixer sola Dy Black Clawson, Snar~le
Di~ision. Other apparatus suitable for use in this
invention are d~sclosed in U.S. 4,016,353. !.
~ 2 F~e-e--e~ c~ ~G,,~ hg~e ~h_ appara~us is
a Model 48 Micar High Consistency mixer the first stream
is introduced into the hopper of the apparatus and tne .;
second s~ream is introduced into the highly agitated :~
mixiny barrel. ~.
The per~oa of time the acti~ation composition is
subjected to the high rate or agilation is an extremely :-.
impor~ant ~ea~ure o~ ~his inven~ion. The period of time
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the activation mixture is subjected to the high rate of :
agitat~en ls ~roadl~ less ~kan ~0 seconds, pr~4e~b~ y
The ac.ivation composition is subjected to the high
rats o~ ~gita~n ~c- ~e sp_~ifi c pe-iod ~ ti~e ~y
operating the mixer continuously and adjusting the
rotor~stato- con~iguration.
~ The process of this invention has been described as
an "acti~ation proeess". By the term "activation ~:
p,oc ~s~'-we m2~n ~hat the compos-tion wnich exits rrom
the mixer can, in ~ome instances, be fully activated and
therefore can be immediately introduced into the
acetylation step without the necessity to age the
: 30 composition for a period of time. By this term we also
mean ~hu ~ th- composl~o~ -~hlch ~xlts from the mixer is
not fully activated and must be aged prior to
:introduction of the composition into the acetylation
step. Whether any additional aging is required, or how
much additional aging is required, varies widely
WO93/255g4 ,~,~ . . PCT/US93/0516~
213~733 ~:
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depending on numerous factors understood by those
skilled in the art, such as the temperature ~f the .;
c~mposition, the type of catalyst and the amount of
catalyst. Typically, the composition i5 aged for a ,.
period of time in the range of 10 minutes to 3 hours,.`.:~
preferably 20 min~tes to ~o m~' n~ ¢,
As has been discussed earlier, an advantage of this
invention is that the time ~or the activation s-tep is .
5ig~if l 52n~ s~ a- ~ . -h~_~, 2-~-n
when aging is required the combination of the time
. requir~d for agitation and the time required for aging -.
: : .is ~ill slgni~icantly less t~an the time for the ~`.
a~tivation steps of the prior art. ::.
The practice of this in~ention can be iilustra~ed
by the fo~lowing example.
A hammer mill is posit~cned s~ch that the outpu~ o.
sub-divided cellulose units will fall into the hopper or
a Model 48 Micar ~igh Consistency mixer sold by Black
Clawson, Shartle Di~sion~ The highlv agitated mix~.g
: 20 barrel entry port o_ the ~ixer is adapted with piping to
: receive th~ a s~ream of acetic acid and sulfuric acid.::
: A con~inuouC activation process is then conducted~.
wh~rein a roll of hardwood cellulose containin~ water is ~.
fed into the hammer mill at ambient conditions and sub-
: 25 dl~id~d i~o units:having a cross sectional diameter of:~
: less than 2 inches which fall i~to the ho~er of the
continuously operating mixer. The composition of this ~;
stream is 96 lbs~min cellulos~ and 4 lbs~min water. 84
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lbs~min acetic acid and 4 lbs~min sulfuric acid are
continuously pumped into the mixer through the highly
:: agitated mixing barrel entry port. The rate o~ ;
~: agitation is adjusted to 1.5 to 2.5 kilowatts per pound
of the combined weight of all four components. Based on
the physical configuration o~ the mixer, the time the :~
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activation composition is subjected to this rate of ~-
agitation for 1 to 3 seconds.
The composition exiting from the mixer was aged 20
to ~0 minutes to become ~ully activated and fed to a
conventional acetylation process and successfully ,~.
~ ace~ylated in~o a product which was further processed by ,.
: ~ conventional means inko commercially acceptable
; cellulose aceta~e. :.
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