Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~i17~
PROCESS FOR THE PRODUCTION OF
DIALDEHYDE CELLULOSE FROM CELLULOSE
This invention relates to a process for the manu-
facture of dialdehyde cellulose. It pertains particularly to
a process for the manufacture of dialdehyde cellulose on the
large commercial scale by the oxidation of cellulosic pulps
derived from the papermaking industry~
Dialdehyde cellulose has important real and potential
industrial applications as a paper and textile sizing material,
as an adhesive component, as a thickening agent for foods, and
in the tanning of hides in the manufacture of leather. In
particular, it is useful as an intermediate in the manufacture
of a variety of other cellulose derivatives, including dicarboxy
cellulose, tricarboxy cellulose, glyoxal and the like.
The oxidative conversion to dialdehyde cellulose of
polysaccharides in general, and starch in particular, using
periodic acid an an oxidizing agent is well known. In the case
of cellulose, the reaction proceeds according to the following
schematic equation:
H H ~ -
-
HOCH O + IO4 > Hl=O o + IO3 + H2O
HC-O- I HC-O~
HC HC --- ¦
H2COH H2COH
Cellulose Dialdehyde
Cellulose
The general reaction has been described in Jackson et
al, the Journal of the American Chemical Society, Vol. S9, pp.
2049-2050, (1937), and in Pfeifer et al, Industrial and
;~0 Engineering Chemistry, Vol. 52, pp. 201-207 (1960). It is
further characterized in S~ager, U.S. 3,086,969. The emphasis `
in these and other ~ ;
-1- ' '
~rior art investigations, however, haa been toward the oxidativ~
conversion of the pol~saccharide stzrch t~ dialdehyde ~tarch$
rather than the conversion of th~ polysaccharide cellulose to di-
aldehyde collulose.
Thus Jackson et al describe in detail successful conversion
of starch to dialdehyde starch, but indicate the resistance of
cellulose to the oxidation by citing cellulose oxidation times
of from 18 to 37 days, and the degradatio~ of the dialdehyde ce~-
ulose product by the acid reaction medium.
Similarly, although Slager discloses in a general way the
periodic acid oxidation of cellulose to dialdehyde cellulose, he
gives specific examples drawn exclusively to the conversion of
starch to dialdehyde starch under carefully defined and critical
reaction conditions, in particular using a periodic acid reaction
medium having a pH of less than 1Ø
It does not necessarily follow that the convertibility of
starch to dialdehyde starch under stipulated reaction conditions
is an indication that under the same or similar conditions cellu-
lose can be converted to dialdehyde cellulose. It is well estab-
lished that each chemical entity has its own peculiar character-
istics and properties, not necessarily forecastable by comparison
to another chemical entity even though the latter be closely re-
lated structurally to the former.
Thus, although starch and cellulose broadly are classified
together as polysaccharides~ they have in fact significant dif-
ferences of structure and properties. For example, whereas
starch is an alpha glucoside, cellulose is a beta glucoside.
Starch is a mixture of polymers of amylose and amylopectin; cell-
ulose, a linear polymer of beta glucoses. Starch is a powder;
cellulosa a fiber. Biologically, starch is digestible by humans,
whereas cellulose is nondigestible. Another inherent difference
is indicated in the Jackson et al reference, supra, wherein an
oxidation time of as littl~ as 24 hours is report~d for ~tarch,
and an oxidation time of as much as 37 days is reported for cel-
lulose, in the conversion of th2~e two substances to their res-
pective dialdehyde derivatives under substant;ally similar reac-
tion conditions.
The resistance of cellulose to selectiv~ oxidation raisos
significant obstacles to the application of this procedure to th~
commercial production of dialdehyde cellulose. Thus, the long
reaction times of several or many days are unsuited to the suc-
cessful operation of a commercial process. The comparative re-
sistance of cellulose to oxidation favors the production of a
multiplicity of oxidative byproducts, which not only lower the
yield of the desired dialdehyde cellulose, but result in contam-
ination of the product.
The same factor promotes the degradation of the periodic
acid oxidizing agent to iodine derivatives other than iodic acid.
It promotes notably the production of free iodine which, being
per se an active oxidizing agent in aqueous medium, attacks the
dialdehyde cellulose and converts it inter alia to carboxy cellu-
loses.
The conversion of periodic acid to iodine derivatives otherthan iodic acid also destroys one of the principal advantages of
the ~eriodic acid system for converting cellulose to dialdehyde
cellulose, in that whereas in that system the iodic acid product
may be converted electrolytically almost qua~titatively back to
periodic acid, which then may be reused, this is not the case
with free iodine and the other reduced products of periodic acid
which accordingly are lost for further use in the process. In
view of the high cost of iodine and its compounds, this repres~
ents a serious economic loss which can spell out the difference
be~ween a procedure for the production of dialdehyde cellulose
which is commercially successful, and one which is not.
The present invention is predicated on the discovery that
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~ 7 ~ 1
cellulose may ~e oxidized by meta periodate ions selectively ar,d
almost quantitatively to dialdehyde c211ulose in accordance ~th
the reaction set forth above, with substantially no conversio~
o~ the periodic acid to ~roducts other than iodic acid, and with
the substantially quantitatlve recovery of the latter for conv~r-
sion to periodic acid, provided the oxidative reaction is carr-ed
out under controlled conditions of critical character as set
forth herein.
It is a further finding that the dialdehyde cellulose so
produced may be isolatad in a pure condition, well suited for its
various industrial applications, including its use as a raw mat-
erial for the manufacture of dicarboxy callulose and other deri-
vatives.
Still another advantage of the process as described herein
is the fact that it may be applied to a wide variety of commer-
cially available cellulosic raw materials, and in particular to
ordinary papermaking pulp, including the clay-containing sludges
available in large quantities as waste byproducts from the clar-
ifiers which are components of conventional papermaking appara-
tus. -
Still another value of the process described herein is that
it may be carried out rapidly, i~e. in from 3 to 6 hours, on the
large commercial scale, using relatively simple equipment.
The foregoing and other advantages are obtained by the exec-
ution of a process which, stated broadly, comprises reacting cPl-
lulose in aqueous medium with meta periodate ion used in a molar
ratio of from 1.2 to 12 moles periodate ion per mole of cellu-
1O8Q at a temperature of from 36 to 60 C. and a pH of between
2 and the pH at which periodate ion is converted to a water in- --~
soluble para periodate. The reaction is carried out for a time
sufficient to convert the cellulose substantially completely to
dialdehyde cellulose, the meta periodate ion being contemporane-
ously converted to iodate. In typical instances, this may be
1(3~i~7~1
accomplished in r~action times of the order of 3 to ~ hours.
Thereafter the dialdehyde cellulose product is separated
from the reaction mixture, and washed, The iodate-conteini~g
filtrate and washings are processed for conversion of their con-
tent of iodate back to a salt of periodic acid, for èxample sod-
ium meta periodate, which then is reused in the conversion of a
further quantity of cellulose to dialdehyde cellulose.
Considering the foregoing in greater detail:
A wide variety of cellulosic substances may be used as
starting materials for the process of the present invention.
These include cotton, as well as cellulosic materials derived
from wood. The materials employed should be relatively free from
metallic ion contaminants, but may contain substantial quanti-
ties, i.e. as much as 40% by weight or more, of inert contamin-
ants. Especially applicable are the cellulosic pulp slurries
derived from the paper industry. These may be either original
slurries, re-slurried wet lap, or slurries reconstituted from
dried pulp, and may have their origin in any of the wood species
which conventionally are converted to papermaking pulps.
It is a particular fsature of the process of the invention
that it may be applied to the pulp slurries obtained as sludges
in the clarifiers and other units of papermaking apparatus even
though such sludges contain large amounts of clay and other inert
components. The invention thus provides a useful outlet for the
utilization of these low cost materials with the end result of
converting them into a useful product, dialdehyde cellulose, of
substantially increased value. It also assists in overcoming a
serious problem of sludge disposal.
The cellulose starting material need be subjected to no
special purification or treating procedures before being employed
in the hereindescribed process, especially when it comprises a
cellulosic papermaking pulp. If a reconstituted pulp is employ-
ed, the cellulose preferably first is fluffed to provide a maxi-
17~1
mum surface area and thus acc~lerate the reaction rate corres-
pondingly. Th~ cellulosic fibers may have an inherent moisture
content of from 1 to lO~o by weig'nt.
The foregoing and other cellulose starting materials are
employed in aqueous medium at consistencies, expressed as per-
centage concentration of the cellulose in the reaction mixtur~,
suitable for maximum efficiency of use of the selective oxidizing
agent employed. The consistency selected is determined by such
factors as the water content of the cellulose fibers, the solu-
bility of the oxidizing agent employed, and the presence or ab-
sence of substantial amounts of clay or other inert adulterants.
It also is determined by working factors such as the ease of mix-
ing the reactants and washing the product for dialdehyde cellu-
lose purification and chemical recovery in the particular appar-
atus employed.
The consistency also should be adjusted to take into account
the respective water solubilities of the reactants and products.
Thus if the oxidizing agent is sodium meta periodate~ the con-
sistency of the reaction mixture should be sufficiently low to
insure the solubility of the sodium meta periodate reactant and
of the sodium iodate product. It is apparent that using insuf-
ficient water to insure the solubility of the sodium meta perio-
date would reduce the speed of reaction as well as the ultimate
yield. Using insufficient water to insure the solubility of the
sodium iodate product would promote precipitation of thP latter
from the reaction mixture with attendant problems of product re-
covery and purification .
In general, the pulp should have a consistency of between 1
and 15% by weight. A consistency of below 1 is so dilute as to
~o be impractical for commercial operation of the process. A con-
sistency of greater than 15~ introduces problems of mixing the
reactants, establishing uniform reaction conditions, and washing
the product. A preferred consistency range is from 4% to 8% by
1(~617~
weight.
The oxidizing agent employed for the selectiv2 and almo3t
quantitative conversion of the cellulo~e to dialdehyde cellulo~
is an aqueous solution of meta periodate ions. The ox dizing
agent thus may have as its source a meta periodate of suffici~nt
water solubility to be useful, and free from metallic ions which
may adversely affect the course of the reaction. Sodium meta
periodate is a preferred example of such a compound. Periodic
acid, derived by electrolytic processes from iodic acid, or by
chemical oxidation of elemental iodine, also may be employed. In
the latter case adjustment of the pH of the periodic acid product
to a value of pH 2 to pH 4.6 is required.
The ratio of use of the reactants, i.e. the molar ratio of
meta periodate ion to cellulose, is important to the successful
operation of the hereindescribed process. If too little of the
oxidizing agent is used, the reaction will proceed slowly and
the degree of conversion of the cellulose to dialdehyde cellulose
will be correspondingly low. If the molar ratio is too high,
overoxidation of the cellulose is favored, with consequent loss
of product through oxidative degradation of the cellulose, the
formation and loss of free iodine, and excessive consumption of
the cellulose starting material.
Additionally, the upper molar ratio limit is determined by
practical considerations such as the high cost of iodine and its
derivatives, the desirability of maintaining a given reaction
mixture consistency, and the necessity of establishing a reaction
mixture which can be worked up effectively.
In view of these various considerations, it is desirable to
employ in the present process a molar ratio of meta p~riodate
ion to cellulose of 1.2 to 12, preferably 1.2 to 3.
Critical to the success of the hereindescribed procedur2 is
adjustment of the pH of the reaction mixture to a predetermined
value of between pH 2 and pH 4.6. Where sodium meta periodate
106178~
is employed as the source of th~ oxidizing meta periodate ion5,
~stablishmQnt of a pH of grPater than 4,6 r~sults ln the conver-
sion of the water soluble meta periodate to th~ water insoluble
para periodate in accordance ~7ith the following equation:
NaI04 ~ 2 NaOH ~- 3 2 6 ~
Precipitation of the sodium para periodate obviously would re-
move from the reaction mixture a significant part or all of the
periodate ions needed for the reaction, thereby at the least re-
ducing the dialdehyde cellulose content of the product, and at
the most rendering the desired selactive oxidation totally im-
possible of execution.
Reducing the pH of the reaction mixture to a value of less
than pH 2 has the adverse and critical effect of destroying al-
together the selective character of the oxidation, i.e. the oxi-
dation of the cellulose selectively to dialdehyde cellulose with
negligible production of carboxy celluloses, nd of the further
oxidative degradation products of cellulose.
Concomitant with the overoxidation of the cellulose, is the
overreduction of the meta periodate, with the consequent produc-
tion of free iodine and of the lower valent compounds of iodine.This has two adverse effects:
First, since free iodine in aqueous medium is an oxidizing
agent, it overoxidizes and solubilizes the cellulose in the man-
ner explained above. Second, it causes loss of iodine, and thus
prevents the recovery of iodine by the conversion of the iodic
acid reaction product to meta periodate starting mat~rial. Loss
of iodine is fatal to the successful commercial operation of the
hereindescribed process, since its success is keyed to the sub-
stantially total recovery and re-use of the high cost iodine-
containing reactants.
It is to be noted further that in regard to the execution of
. . . , :
.. , . . ~ .. ~.. : : . :. ;
17~1
the procedure neces3arily at a pH l~vel of fro~n 2 to 4 6, a fun-
damental and surprisin~ distinction between the beha~ior of th
polysaccharide starch and the polysaccharide cellulose is ev1-
denced. As s~t forth in Sla~er U.S. 3,086,969, supra, the perio-
date oxidation of starch requires a reaction mixture pH of less
than l; as disclos~d herein, the commercially successful p~rio-
dat~ oxidation of cellulose requires a reaction mixture pH of
from pH 2 to pH 4,6.
Still another reaction variable requiring close control in
the execution of the hereindescribed procedure is the reaction
t~mperature, In general, the process may be carried out satis-
factorily using a reaction temperature of from 36 to 60C. More
specifically, a preferred temperature range is constituted by the
range of from 40 to 50C.
Whera the reaction temperature is below 36C., the reaction
takes place too slowly to be practical. In fact, where the tenD-
erature is at ambient room temperature, reaction times of several
days are required for its completion. On the other hand, where
the reaction temperature is above 60 C. .he reaction becomes
erratic. The yields and ex?ected results from successive runs ~- -
are not reproduceable and undesirable side reactions occur, These --
are of the character noted above, involving overoxidation of th
cellulose and overreduction o~ the meta periodate. As a conse- ~
quence~ thsre tand to be formed as by-products substantial a-
mounts of carboxy cellulose and of the oxidative degradation pro-
ducts of cellulose. Also, free iodin~ is formed, resulting in
undesired degradation of the cellulose and in loss of iodine.
Still further, the water insolubility and other physical proper-
ties of the desired dialdehyde cellulose product are affect~d ad-
versely~ with detriment to its eas~ of r~cov~ry and its applica-
tion to its various end uses.
Th~ duration of the reaction is determined principally by
variables discussed abovs, in particular th~ consistency, molar
_9~ ' ' '
-. .
. ' ~ , ,' , ' ., , ' . ~ ~
~ 0617~1
ratio of reactants, prI and temperature, It is a ~eatur~ of the
invention, hoT,Iever~ that when the3e variables are controll~d
within the limits set forth, the reaction will ~roceed almos~ to
com~letion in an operating ~ariod of from 3 to 6 hours. In oth2r
words, at the end of this reaction duration, the cellulose ~,1ill
have been cor.vert~d practically quantitatively to dialdehyde cel-
lulose, to the substantial exclusion of carboxy celluloses and
other cellulose oxidation products~ and the meta periodate con-
sumed will have been converted quantitatively to iodate, thus
determining thP successful effectuation of the process on a com-
mercial scale,
Procedurally the procsss of the invention for the selective
oxidative conversion of cellulose to dialdehyde csllulose is
carried out in a simple and uncomplicated manner,
The waste paper pulp or oth~r selected cellulose starting
material is placed in a reaction vessel and mixed with water to
the desired consistency. Sodium meta periodate or other source
of meta periodate ion is added in predetermined amount, One al-
ternate source of meta periodate ion comprises sodium para per-
;odate having its pH adjusted to a value of pH 2 to pH 4,6 andresulting from the chemical oxidation of iodine, Another source
of the periodate ion is the iodic ion resulting from a previous
run, and oxidized to periodate ion electrolytically,
The pH of the reaction mixture is adjusted to the desirsd
level of pH 2 to pH 4,6 by adding any strong acid which is non-
rcactive toward the other constituents of the mixture, Suitable
acids are sulfuric acid, phosphoric acid, or benzene sulfonic
acid, Unsuitable acids are the halogenated acids which are oxi-
dizable under the conditions of the reaction, and nitric acid
which per se is an oxidizing agent reactive toward the desired
dialdehyde cellulose product.
The temperature of the reaction mixture is adjusted to the
desired level of between 36 C, and 60 C, and controlled ~
--10-- .
-'' : ' "" ,' ; '' , . ' '' ' ' ~" '' ' ' ' .
.. . . . ..
~06~7~
out the entire reaction. ~here the reaction is ~xGth rmic, 3ucn
control may be achieved by circulating cooling wat~r ~5 required
through the jacket of a jacketed reaction vessel,
At the conclusion of Lhe reaction period, after the cellu-
lose has been substantially comoletely converted to dialdehyde
cellulose, the latter is separated from th~ reaction mixture and
waQhed one or more times with water. As thus obtained, the dial-
dehyde cellulose is sufficiently pure or most of its commercial
uses.
The washin~s are processed for recovery of their content of
iodate compound, This is accomplished chemically, or by electro-
lytic oxidation of the iodate to meta periodate in well known
manner. The meta periodate then is used in the oxidation of a
further quantity of cellulose to dialdehyde cellulose.
It is a particular feature of the invention, which makes it ~ -
highly attractive commercially, that the procedure outlined a-
bove proceed~ almost quantitatively to yield reaction products ~ -
which may be isolated in a pure condition with almost no loss of
reagepts.
Thus the conversion of the cellulose to a dialdehyde cellu-
lose product having substantially two carbonyl groups per glu-
cose unit takes place in yields of 95 to 100%, typically about
98~, and the dialdehyde cellulose product is isolated in a form
and condition wQll suited to its various commercial uses.
Similarly, the electrolytic conversion of the iodate product
to meta periodate occurs in yields of from 96~ to 100%, typica~y
98~ or better. It~ too~ is recovered in a commercially useful
form in which it may be applied to the oxidation of a further
~uantity of cellulose to dialdehyde cellulose. ~ ;The process of tha invention is illustrated in the following
examples, wherein parts are given in parts by weight.
- 1 1- :.,
1(36~7~
Example 1
This example illustrates a preferred process for car~ying
out the oxidative conversion of cellulose to dialdehyd~ cellu-
lose.
The cellulose raw material for this ~rocedure wâs a reconsti-
tut~d pulp made up of well fluffed cellulose derived from bleach~
ad kraft pulp made from Douglas fir and Pin wood chips. It had
a water contant of 6.3% by weight.
69.2 Grams (0,4 mole) of air dried cellulose (6.4% water
content~ and 1000 ml. of water at 50 C. were placed in a reac-
tion vessel provided with stirring and heat control means. 107.0
Grams (0.5 mole), a 25% molar excess, of sodium meta periodat~
was added. This represents a molar ratio, periodate ion to cel-
lulose, of 1.25. The reaction mixture was blended at high speed
until the cellulose was well disperssd. The pH of the dispersed
mixture was 4.6. Its consistenoy was 6.25%.
The reaction mixture was gently agitated at 50 C. for 5
hours while maintaining the pH at a value of from 3 to 4.6.
The reaction mixture then was filter~d to separate the solid
dialdehyde cellulose product. An aliquot of the filtrate was
analyzed for periodate content and the total amount of periodate
calculated. The value obtained indicated a dialdehyde cellulose
content of 100.5% of the theoretical, the excess percen~age val-
ue being within the limits of axperimental error.
The filtered dialdehyde cellulose product was washed with
one 500 ml. portion of water, next with two 200 ml. portions of
water, and finally with two 200 ml. portions of methanol. -
After air drying the dialdehyde cellulose product weighed
62.5 grams, or 97.5% of theory.
Example 2 -
This example illustrates the application of the process of
the invention to a papermaking pulp obtained as a waste residue
from paper mill clarifiers and containing a large proportion of
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10617~1
clay filler,
The papermaking pulp employ2d comprised the sludg2 residu~
obtained from the clarifi~rs of a large kraft ~ap r mill. Th~
sludg~ contained 45,6% cellulos~ and 54.4% papermaking clay, in-
cluding a proportion of titanium dioxide and other inorganic fil-
lers.
17,65 Grams of sodium paraperiodate and 100 ml. water were
placed in a 3-neck, l-liter flask. The sodium paraperiodate was
acidified with 5% sulfuric acid to a pH of 3,65, thereby conver-
ting it to sodium meta periodate, Water then was added to a tot-
al volume of 203.75 ml. ~ - -
17,75 Grams of the cellulosic sludge having a cel~ulose con-
ten~ of 8.094 grams was added to the flask and mixed in. The
consistency of the mixture was 3,6% and the molar ratio, meta pe~
iodate to cellulose~ was 1,2.
The mixture was heated at 32-40 C, with stirring for eight
hours.
Periodically, an aliquot of 0.50 ml. of the clear reaction
solution was titrated with standard O.OS N sodium arsenite to de-
t9rmine the end point of the oxidation.
After a reaction period of eight hours the pH of the reacti~
mixture was 3,5. The fully oxidized sludge was collected on a
ilter and washed with water, It then was driad at 100 to 105C,
for three hours, to constant weight, It weighed 17,1142 grams.
DetQrmination of carboxyl following a Cannizzaro reaction gave a
value of 24,98~, This indicated a dialdehyde cellulose content
o~ 97,69~.
The cellulosic content o the sludge thus was convertad sub-
stant;ally completely to dialdehyde cellulose isolated in a form ;
suitable for conversion to other cellulose derivatives and for -
separation from its substantial content of clay.
The dialdehyde cellulose obtained as above was separated f
its content of clay by placing 10 grams of the dialdehyde cellu-
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.. ~ . ~ , . , . . ; :,. .:; . , :
10617t~
lose sludge and 150 ml. water in a 300 ml, round bo~tom fla~k.
The mixture was rQfluxed for 2 1/2 hours on an oil bath kept at
120 C,
The resulting dialdehyde cellulos~ solution was separated
from the clay residue by filt~ring i~ hot and washing the clay
residua with hot water. The filtrate then was concentrated in a
steam heated rotary evaporator, The concentrate was evaporated
to dryness, It had a constant weight of 4,26 grams, represent~
a 94,67~ yield of dialdehyde cellulose, This product had a
Cannizzaro-reaction-determined dialdehyde cellulos~ contant of
g7,78~,
Example 3
This example illustrates the application of the process of
the invention to the conversion of cotton to dialdehyde cellulose.
It also illustrates the use of sodium paraperiodate as the souræ
of the meta periodat~ ion used as the oxidizing agant,
A mixture of 17,65 grams sodi~m para periodate and 100 ml,
water contained in a one liter flask was acidified with 5% sul-
phuric acid to a pH of 3.65. Additional water was added to exa~
tly 160 ml,
8.05 Grams of cotton cellulose was added to the mixture in
the flask and heat~d immediately to 50 C. Th~ consistency of
the resulting reaction mixture was 3,6% and the molar ratio~ meta
periodate to cellulose, was 1,2, The reaction mixture was main-
tained at ~his temperature with constant stirring for 7,5 hours,
The progress of the r~action was followed by titrating O,S0
ml, aliquots of the clear reaction liquor with standard 0,OS N
sodium arsenite, in the presence of sodium bicarbonate buffer
and O,S0 gram potassium iodide, using starch as an indicator,
After a reaction period of 7 1/2 hours~ the reaction mixture had
a pH of 3,5,
The solution then was filtered off and the dialdehyde cellu--
lose product washed with water and dried at 105 C, for thras
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~0617b~1
hours, The wei~ht of the dried ?roduct ~,1as 7,92 grams, or a
yield of 99,62%, A Cannizzaro determination of aldehyd indica~
an aldehyde content of 99,29% of theory.
Exampl~ 4
This example illustrates the ~ffect of temperature on th~ --
hereindescribed procedure,
The cellulose used was a mixture of Douglas fir and Ponderos2
pine pulp, It had a water content of 6,3% by weight.
To a suspension of 69,2 grams (0.4 mole) of the well fluffed
10cellulose in 2000 ml, of water at 50 C, was added 107.0 grams
(0,5 mole) of sodium meta periodate, The reaction mixture was
contained in a flask equipped with means for stirring and heating,
It had a pH of 4,6 and à consistency of 3,2%, The molar ratio of
periodate ion to cellulose was 1,25,
The reaction mixture was stirred at 50 C. for 5 hours and
filtered, An aliquot of the filtrate was analyzed iodimetrically
for periodate content, The value obtained indicated a dialdehyde
content of 100,5% of the theoretical,
The filtered dialdehyde cellulose was washed with 3 x 500 ml.
portions of water, then with 2 x 200 ml. portions of methanol,and
dried to constant w~ight at room temperature, The yield of iso-
lated product was 62.5 grams, or 97.5% of theory.
The foregoing procedure was repeated with selected reaction
tamperaturas of between 20 and 60 C. for selected reaction per-
iods. In ~11 oases the oxidation was carried out at a pH of 4.6
with a 25% molar excess of sodium meta periodate, The results
are indicated in Table I below.
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lV6i71~1
TABLE I
Carbonyl Content Dialdehyde Cellulo~e
Temp~rature C. Time (% of Theory) Yield (% o~ Th~or~)
20 3 Days 91 99
20 4 Days 99+ 98
43 1 Hour 30 98
43 2 Hours 59 97
43 3 Hours 81 97
43 4 Hours 90 97
43 5 Hours 94 97
43 9 Hours 100 97
50 5 Hours 101 96
60 2 Hours 94 96
60 3 Hours*
60 4 Hours*
Excessiva decomposition present
It is apparent from the foregoing that at reaction tempera-
tures of the order of 20 C., the required reaction time is in-
ordinately long. On the other hand, overoxidation and decomposi-
tion, as evidenced by the production of frea iodine and decreased : :
yield of dialdehyde cellulose, became evident at 60 C,
Example 5
The following example illustrates the adverse effect of car-
rying out the hereindescribed reaction at a pH value of less than
pH 2.
Sodium p~raperiodate, 17.8500 grams in 100 ml. water, was
acidified with 2% sulfuric acid to a pH of 1.1, Water was addPd
to a final volume of 204 ml.
17.750 grams of papermill sludge containing 8.1 grams of
cellulose was added to form a mixture having a consistency of
~.6~ and a molar ratio of periodate ion to cellulose of 1.66. :~.
This mixture was heated to a temperature of 39 to 46 C. and
stirred constantly over a reaction period of four hours, ~ :
During the reaction period excessive decomposition of the
periodate started after a reaction time of 3t4 hour and continued : :
over the entire reaction period, as indicated by the lib~-ration
of free iodine in the reaction mixture. This was formed in in-
creasing amount, the color of the reaction mixture changing dur- :~
ing the course of the reaction from light brown to dark brown to
: ~:
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1(3617~1
purpl- .
At the ~nd of the react,,on period, the mixtur~ ~I,as filt~red
and the oxidizsd cellulosic sludge washsd with water and then o-
vsn dried to constant T~elght. The dried product had a dialdehyde
c~llulose content of 4.35 grams. This indicates a 45,64% loss OL
dialdehyde cellulose through overoxidation of the cellulos~ start-
ing matarial.
The filtrate and washings of the oxidation mixtura wer~ pro-
cessed to determine the loss of periodate oxidizing agent.
To this end the filtrate ~nd washings were neutralized with
5~ sodium hydroxide after which 7,3 grams of excess sodium hydrox-
ide was added. This rPpresented 3 moles of sodium hydroxide per
mola of sodium paraperiodate, The mixture was heated on a steam ~'
bath and bubbled with chlorine until it was neutral. After the
reaction mixture had remained at room temperature over night, the
precipItated sodium metaperiodate was filtered off, dried and
weighed. It weighed 3.81 grams, indicating a loss of periodate
during the oxidation of 78.55%. '~
Example 6 ~-
This example illustrates the process of the invention with '
incremental meta periodate addition during the course of the reac- ,
tion. ~,
A suspension of 0,87 grams (0.005 mole) of fluffed paper
pulp cellulose derived from Douglas fir and pine wood chips and
having a 6~ moisture content was mixed in a reaction vessel with
25 ml. of 0.25 molar sodium meta periodate. The consistency of
the reaction mixture was 3,4%, Its pH was 4.6, and the molar rat-
io of periodate ion to cellulose was 2,04. During the course of
the reaction the mixture was kept at 43 C, with occasional shak-
in~-
At one hour intervals the reaction mixture was analyzed with
sodium arsenite for periodate content. Sufficient solid sodium
periodate then was added to bring the concentration of periodate
-17-
106178~
back to 0.25 molar and the pH to 3 to 4,6. The per cent oxida-
tion was calculated from the amount of periodate consur~2d. Th~
reation was complete in 5 hours. The data are given below.
TABLE II
Ratio of Total Millimols Cumulative Carbonyl
Periodate Employed P~riodate Millimols Content
Hrs, to Cellulose AddedPeriodat~ Added (9~ of Theorv)
.
0 1.25:1 0 6.~5 0
1.2:1 1.627.87 32
2 1.57:1 1.379.24 59
1.85:1 .9810.22 79
4 2.04:1 .3710.59 87
2.04:1 0 10,59 98
At the conclusion of the reaction, the dialdehyde pulp was
water separated from the reaction mixture by filtration and wash-
ed twice with water used in amount equal to one-half the volume
of the oxidizing solution, and air dried.
Example 7
This example illustrates the high efficiency of iodine re-
10 covery which may be achieved by the practice of the present inven-
tion.
A suspension of 9,35 grams of cellulose pulp (0,054 mole)
having a water content of 6.896 was suspended in a solution of 14.
378 grams sodium paraperiodate in 100 ml. water. The consistency
o$ the reaction mixture was 7.55%. The molar ratio of periodate
ion to cellulose was 1.25.
Th2 r~action mixture was heated with stirring at 43 C. for
fivs hours. At hourly intervals additional sodium metaperiodate
was added as required to keep the periodate concentration at ap-
20 proximately its starting value.
At the end of the reaction period the oxidized pulp was fil-
tered and washed with S x 100 ml. portions of water. The initial
,and subsequent filtrates were kept separate and analyzed for ~ ~ -
-18- ~
- , . . . . , . :, , .
10~17~1
iodine content, Th~ percent iodine recovery in eacn was c~lcula-
ted and tabulated cumulatively, The r~sults are shown in th
following tabl :
Moles IO4- in Moles IO - in Total moles
reaction reaction3 Iodine in re- ~ Iodine
Filtrate Filtrate action filtrate Recovered
:
0.0528 0.0532 0.1060 84.8
1st Wash
FiltratP
0,0087 0,0075 0.0162 13.0
2nd Wash
Filtrate
0.0013 0.0001 0.0014 1.1
3rd ~ 4th
Wash Filtrate
0,0012 0.0001 0.0013 0.96
.
TOTALS:
0.0640 0.0609 0.1249 99.9~
As indicated, the recovery of iodine was substantially
quantitative.
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