Note: Descriptions are shown in the official language in which they were submitted.
10~27
This invention relates to highly absorbent materials made by
chemically modifying the naturally occurring gtructure of cellu-
lose ethers having sufficiently high degrees of ether substi-
tution to be soluble in water but being further modified to ';
become highly absorbent insolu'ble cellulose ethers.
Cellulose fiber and regenerated cellulose are raw ' "
..: .
materials for many co~mercial absorbent products including, for ''
example, such products for absorbing body fluids as catamenial
napklns and tEmpons, diapers and~surgical dressings. WhiLe,
- in the main, unmodified cellulose has proven usè~ul in such
products, in an effort to improve product quality and economy, ~ ~
the art has~searched for improved materials. It was discovered "~'~', -
for example, that cellulose ethers such as carboxymethyl~cellu-
lose~ethers such as carboxymethyl~cellulose exhibited incressed
ab~sorption~and retention properties~fo~r body ~luids, these
desirable properties~increasing with the degree of ether'sub-
st~itution (D.S.).'~Aecordingly, such materials in, of course,
insolubIe form are useful in products for absorbing body ~luids
such teachings being disclosed in U.S. Patent 3,005,456, issued ''-
to Graham on October 2~, 1961. Further in U.S. Patent 3,589,364
issued to W. L.~ Dean~and G. N. Ferguson on June 29, 1971~ e is
disclosed'a particular~form o~ insoluble, carboxymethyl `'
celIulose having a hi~gh~degree~of~substitution of ether gr~ups .~.
~: : , .: . .
. .
-
5~27
and insolubilized by wet crosslinking the cellulose using j;, -
methods such as are described in U.S. Patent No. 3,241,553
issued to F. H. Steiger on March 22, 1966. The U~S. Patent
3,678,061, still another form of insoluble carboxymethyl
cellulose is disclosed having a high degree of substitution,
and in this case, insolubilized by an acid and heat treatment. ~ -
U.S. Patent 3,256,372 to Adams et al discloses grafting
hydrophilic polymers to the cellulose backbone and, in our
; -: .
U.S~ Patent 3,889,678 issued on July 17, 1975, we disclose
still another chemical modification of cellulose whereby a -
balanced quantity of ionic and nonionic copolymer moieties
are grafted to the cellulose backbone and may be grafted to
:~: .: . .,
modified forms of cellulose as well. ~--
Each of these references teach modified forms of
cellulose w'nich represent great improvements in absorption
and retention capacities for body fluids over the properties
`'~''!',.'.~.'.".;:, .'
of unmodified cellulose. Notwithstanding these prior art
improvements, the search continues for still better absorbents.
SUMMPRY OF THE INVENTION -
It has now been discovered that a form of modified '
cellulose may be provided which far exceeds the~ absorption ~ -
and retention properties of prior art modified cellulose and !~' ';' ' ''
hence, is advantageously employed as an absorption media in an
absorbent body for products such as catamenial napkins and ~;
tampons, diapers and dressings provided for absorbing and
:
retaining body fluids. In accordance with this invention, an
insoluble etherified cellulose graft copolymer is provided
comprising an etherified cellulose which is soluble in water
.. .. .
in the absence of grafting and is insolubilized by having,
.,.~ . .
grafted to the cellulose backbone, a quantity of side chains ;
of polymer moieties sufficient to render said ethers insoluble.
-3
'~ ' ','.
~ 0451Z~
In accordance with the invention there is provided
an absorbent product for absorging body fluids comprising
water-insoluble carboxyalkyl cellulose having a degree of sub- -
stitution ranging from about 0.4 to about 1.3 average number
o~ carboxyalkyl groups per anhydroglucose unit. The carboxy-
alkyl cellulose has grafted unto its celluloce backbone side
chains of hydrophilic polymer moieties in an amount which ranges
from about 10 to about 90% by weight, based on the weight of
the grafted carboxyalkyl cellulose and sufficient to render -
the grafted carboxyalkyl cellulose insoluble and to provide
said grafted carboxyalkyl cellulose with an XOW in 1.5% by ;
weight aqueous sodium chloride solution of at least 30.
The particular etherified cellulose may be selected
from the group consisting of carboxyalkyl cellulose, phospho-
noalkyl cellulose, sulfoalkyl cellulose, and salts thereof,
and a sufficient quantity of such etherifying groups are
present per anhydroglucose unit in the cellulose chain to
render such ethers water-soluble if the grafted polymer groups ;~
were not present. Such a degree of ether substitution (D.S.)
of at least 0.35 ether groups per anhydroglucose unit is
generally sufficient. Salts of such ethers should generally
: . ,
comprise the alkalai metal and ammonia salts, e.g., Li
NaC5, K, or NH3 salt~
The cellulose ethers are rendered insoluble by
graftlng, to the cellulose backbone, side chains of homopolymer
;or copolymer moieties which side chains may be made up of
hydrophilic, hydrophobic or both hydrophilic and hydrophobic
polymeric moieties and should be present in sufficient quanti-
~ - i
~ ~ties to render the ether water-insoluble. The quantity of ~ ~-
side chains which must be grafted to the backbone will vary in
,
~ aocordance with the type of ether and the D.S~ of the ungrafted ,- -
lV~S~
cellulose ether~ For example, in the case of carboxymethyl
cellulose at a D.S. of 0.4, the side chains should constitute
~??, ::.'.''- !, .,, '
.~ ~
.~ "' ":,",'
,'`;' . '"'" '
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''' ' ,,"; ''
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lO~S127
approximately at lea~t 10% by weight of the grafted cellu-
lose ether. At a D.S. of 1.2, the side chains should be at
least ab~ut 25% by weight of the grafted cellulose ether. :
The side chains could constitute as much as 90~/O or more.
S While polymers that are hydrophili~ and ~olymers . .
that are hydrophobic or copolymers bein~.both hydroPhilic
and hydrophobic may be grafted to the cellulose backbone,
particular advantage accrues in using ~er the hydrophilic
polymer or the hydrophilic/hydrophabic copolymers as with these,
the resulting grafted cellulose ether exhibits e~en greater -
absorption and retention properties, this sur~risingly being :~
the case without~sacrificing insolublllty.
DETAILED DESCRIPTION OF THE~ INVENTION`
, . . . .-
' ;' ' - ~ .. '-.
In accordance with this invention, a product is
provided which is the result of havin~ cellulose undergo the . .
two chemical reactions of etherification and polymér graftin~. . ``
The starting material for these reactions may bè natural cellu~
lose fibers such as:, f~r example, wood pulp, hem~..bagasse,
. . ~,. .
cotton, and the like or may be a regenerated cellulose fiber .
such as rayon. ~
Prefërably, the etherified ~ellulose i~ selected
from the group con8isting of carboxyalkyl cellulosej ~hos- :~
: :.. , - .
phonoalkyl cellulose, sulfoalkyl cellulose, and the alkali .;
.: . . . . . .. .
metal salts the~eof. Etherification is generally accomplished `.` :-
.
, ., '' . .':
_5~
.:
,
- :, . .: .
~" ' : .:. '
:
.
~O~SlZ7
.:
by r~acting cellulose with an etherification rea~,ent in an . .
alkaline dispersing media. For example, sodium carboxymethyl ~ .
cellulose may be made by the process clescribed by R. L, Whisler
in "Carbohydrate Chemistry", Vol. III (Cellulose), at page~ ;
322-327, Acad~mic Press, Inc. (1963) wherein there is disclosed :.~ .. -.. .
methods of converting cellulosic materials, notably cotton : :~
linters, into carboxymethyl cçllulose by reaction with chloracetic : :
acid and aqueous sodium hydroxide in a propanol solution. The .:
so-called slurry p~ocesses for manufacturing sodium carboxy-
methyl cellulose is described in U.S. Patent 3,34S,855 issued
to Russel Nelson on~October 17, 1967 wherein the de~ree of
etherification (D.S:.) is con~rolled and can be varied in the
range of from about 0.4 to about 1.6. This product is ` :
available commercially in either powdered or fibrous form,
although it should be noted that even higher D.S. products
ranging from 2.5-2.77 can be made in accordance with the process . :.. .. . .
deæcribed in the aforementioned publica~ion by Whistler. ;.
~ Phosp~onoalkyl ceiIulose may bé msd2 in a ~imilar `: :
., - ....
manner employing a phosphonoalkylating rea~ent solution ~om- `. .:.
prising a basic aciueous ~olution o~ a compound of; the ~tructure~
. -: .
OX
R-P ~ o ;;
' ~ ' \, , :.
wherein X is a h~lo~en and R is an alkylene radical. A:pre- .
ferred reagant is;ch]Loromethylpho8phonic dichloride.
.-, . .
:~ ~ ', "; ,'' ':, ,'
' ` , '
,~,
~ 4 5 ~ 27 - -
Sulfoalkyl cellulose may be made in a similar ~;
manner employing sulfoalkylating rea~,ent solution comPrising
a basic aqueous solution of a compound of the structure:
. o ~,. . .
X - R - S - oY
1 1
0 . '~ .
wherein X is a halogen, R is an alkylene radical and Y is
chosen from the group consisting of a haloge~, hydrogen, or ;~
alkali metal atom.~ A preferred reagent is chloroethyl-
sulfonic acid. -~
The resulting cellulose eth~r should have suffi-
cient etheri~ying groups to render it water-soluble in the
absence of other treatment . Generally, for a carboxymethyl
cellulose ether, a D.S. of at least about 0.35 will accomplish `~
thiæ re3ult, particularl~y for the alkali metal salts of these ,
ethers. As is well-known in the art, the D.S. may be con- .
trolled during the etherification process by controlling the ~;
reaction time and~temperature and~the proportions of reactants.
In accordance~wi~h this invention, the ethcrs have ~ ~;
grafted onto the c~ellulose backbone thereof, side c~ ~ o~
polymer or copolymer moieties in ~sufflcient quantity to render
the~gra~ted product~insoluble in water. Such side chBdnB may `i ;
comprisP hydrophilic or hydrophobic moieties and, in act,
a given molecule~of cellulose e~her could be provLted with
variouæ combinatianB of theBe kinds of polymers.
. ,, . ~: . . .
,:
. ! ,,
~ -7-~ ~
. ~ :. .. :
.
. ~
:,,
, i , , : . ~ . ~ ., .
,~: ' ~ . ;~'
~ 0 ~ 5 1 27
Hydrophilic polymer moieties usable for this
purpose may be, for example, poly(acrylic acid~, sodium
poly(acrylate), poly(methacrylic acid), potassium poly(meth-
acryla~e), poly(vinyl alcohol sulfate), poly(phosphoric acid),
poly(vinyl amine), poly(4-vinyl pyridine), hydrolyzed poly
(aryloitrile) and the like. ~ :
Also usable are hydrophobic polymers such as,
for example, poly(methyl methacrylate), Poly(eehyl methacrylate),
_~ poly(ethyl acrylate), poly(butyl acryIate), poly(vin~yl ~cetate),
poly(styrene), poly(butadiene), pvly(isoprene~, and the like.
Copolymers of any of- these groups are likewise : :~
usable and, in particular, stiLl ~reater enhancement of absorp- ;.
tion and retention properties are realized when :at lea3t a
.
portion of the polymer moieties are chosen from the group
15 characterized as hydrophilic.
The cellulose ethers may be combined with either ~:~
the preformed homo- or copolymers in the irst instance, or
with the precurs~er~monomers of these polymers wi~h ~olymerization . :.:
taking place in situ. In eithe~ event, the reactants may be
dispersed, and the reaction carried out, in a vapor medium Dr
a non-aqueous medium such as, for exampl~, acetone alcohols ~.
(e.g., methanol, e-thanol, isopropan~l, etc.), ben~ene,:liquid . .
ammonia and the lilce. Preferably, howe~er,~che:grafting
reaction is carrie~ out in an aqueous medium.
,
.
'~''~ ".'.
:
,: .
.
,
~)4SlZ7
~ hen the ~rafting is carried out in a liquid
medium, to promote dispersion and hence, more uniform poly-
merization of some monomers (e.g. butadiene), it is desirable
to add a few drops of an emulsifier to the reaction mixture.
Examples of such an emulsifier are Triton X-lOO*(one of a class
of acrylalkyl polyether alcohols, sulfona~es, and sulfates
sold by Rohm & Haas); sodium lauryl sulfate; lauryl bromethyl
ammonium chloride; a cationic quaternary ammonium salt of the
alkyl trimethylammonium chloride and dialkyl dimethylammonium
chloride type wherein the average alkyl compo~ition is 90~,/,
dodecyl, 9% tetradecyl and 19% oxtadecyl and which is supplied
as a solution of 33% active ingredient, 17~/~ sodium chloride,
and 50% water by Armour & Co. as ~rquad 12* lauryl pyridinium
chloride, and the like. `^
The grafting reaction may be initiated with an ~;
ionic initiator (e.g., alkali hydroxides),a cationic initiator -
(e.g. a Lewis acid such as boron trifluoride), or even with - -
radiation (ultraviolet, gramma, or electron beam radiation).
It is preferred, however, that the grafting be carried ou~ by
the free radical polymerization mechanism using a free radical
initiator such as, for example, ceric ion, ferrous ion, ;
cobaltic ion, (NH4)2S208 cuprous ion, and the like. The
ceric ion initiator is preferred.
Because most ree radical reactions are inhibited r","
by the presence of oxygen, it is desirable to flush out
essentially all the oxygen from the reaction vessels by bubblin~ -
an inert non-oxidizing gas such as nitrogen, helium, argon, e~c.,
through the system prior to the addition of the free radical
initiator.
* Trademark
_9_ ' '' ., '
1045~LZ7
The pH range used for the reaction depends on the
particular initiator used. One coulcl use anywhere from a
highly acidic pH (0.8-2.3) to a highly basic pH ~I'2 14),
depending on the choice of initiator. For the preferred ~ '
ceric ion initiator, the pH should be acidic, i.e., less than
seven and preferably about 0.8 to about 2.3. '~
The grafting reaction may be carried out at
temperatures ranging from room temperature (i,e. 20 to 30C.~ '
to the normal boiling point of the low2st ~oiling component ,'
of the mixture. If the reaction is carried out under greater
th~n atmospher~c pressure, the temperature could then be ;',~
raised above the normal boiling point of ~he lowest boiling',' ~
component of the mixture. The rea~tion mixture may al90 be -,
cooled below room temperature, if desired. - ` ";'
, . . .
A satisfactory product may be obtained by grafting~. '"
either inherently hydrophilic or hydrophobic polymers or ~7,'. ~'
mixed ~opolymers to the cellulose in the manner~de~eribed above. "' ""
However, as i8 pointed out herein, particular advantage ,,
accrues to e~hers grafted with a~ l~ast partially,hydrophilic '''~
chains and a satisfactory method of accomplishing this~is to ~`;,
flrst grat, by,the method described above,a polymer whi~h is
at least'partially hydrolyzable and then ~ubsequently hydrolyzing
the product to produce an at least partially hydrophilic
grafted chain. Such hydrolyzabl,e pol~mer is for'example, poly-
acrylonitrile whiçh can be hydrolyzed to'hydrophilic alkali
metal poly(acryl~te). When copolymers o~ poly,acrylonitrlle ,;
~''` ':'; ~ "'', ' ~
.
.. . . .
.
.
~ 5~2~
and relatively non-hydrolyzable polymer moieties, e.g.
methyl methacrylate, ethyl acrylate, butadiene and the like, -~
are grafted to the cellulose ether cmd subsequently hydrolyzed
in a controlled manner, a mixed polymer chain results which
is partially hydrophilic and partially hydrophobic. Hydro- ~
lyzation is accomplished by reacting the grafted-ethers;, pre- -
ferably under reflux, with an excess of 8 so1ution of a
_- strong base, e.g., sodium hydroxide, potassium hydroxide,
lithium hydroxide, and like bases. The concentration of
this solution may be from about 1% to about 50/0 by weight.
The ~eight percen~ of polymer grafted tQ the
cellulose ether (based on the weight of grafted ether) depends
to the major extent upon the D.S. of the ether. Generally,
the greater the D.S., the greater the weight percent of
- . : :
grafted polymer required to render the otherwise ~ater-soluble
.
cellulose ether insoluble. It has been ~ound that this rela- ;
tionship is essentially independent o~ the na~ure of the polymer,
-
i i.e., ~he hydrophilicity or hydrophobicity of the p~lymer.
The following table illustrates this relationship -
using sodi~m carboxgmethyl cellulose of varying D.~S~. as exeilplary
cellulose e~hers. ; ~
MINIMUM POLYMER GRAFTING TO INSOLUBILIZE ~,., ~.`
SODIUM CARBOXYMETHYL CELLULOSE
._ . . . . . . _ ;
Degree o~ Sub-
Qititution of CMC 0.3 n.4 o.s o.~ 0.7 0.8 0.9 l.O l.l 1.2 1.3
Minimum Polgmer
Add-On (~/O) - ~ 0~ 9 12 13 ~14 15 17 19 21 23 27
,. ~ ~':.':
.~
.:
;. .
1~45127
The gra~ted cellulose ethers of this invention have
been found to be significantly greater in both absorption and ~-~
retention properties over prior chemically modified forms
of cellulose and even over the grafted unetherified cellulose '
described in our above referenced U.S. Patent 3,889,678.
While the products of this invention may be used in the form of
powders, it is preferred that, when they are used in a fibrous
absorbent body in a product for absorbing body fluids, they ;~
retain the original fibrous structure. Several methods of
producing such a fibrous product will occur to one skilled in
the art in view of the teachings herein. For example, when
the products of this invention are formed by first producing
water-soluble alkali metal cellulose ethers and then grafting
.,. ~ ,.
in an aqueous media, the ungrafted intermediate product can
be temporarily water-insolubllized by treating it with an acid
solution. Thereafter, the grafting can take place in a water ~
media, while still preserving the fibrous structure. Subsequent ; --
to grafting, the product can be treated with an alkali metal
hydroxide to convert the ether ba-k to its original alkali
metal salt form. Alternatively, the sequence of reaction steps
could be varied to either first graft unetherified cellulose
and then subsequently etherify or to both graft and etherify
essentially simultaneously. In any event, the fibrous structure
of the cellulose can be maintained. - , ;
,
~ , .
, ', ,
,..
.' :' :. ~ ~
,., :
.;...:: :
-12-
.: .
S~
. ~:
The products of this invention may be used alone ::
or mixed with unmodified cellulose, or other absorbent material, .~ .
in the manufac~ure of absorbent napkins, tampons, sponges and
the like. Fibrous products of this invention either alone or
in combination with other materials such as, for examPle>
untreated cellulo8e,:may also be made into nonwoven fabrics or
tissue, which fabrics or tissue are useful in the manufacture of
absorbent napkins, tampons, sponges and the like.
The grafted cellulose ethers of this invention, : .
lO their properties and the methods of prPparation will be more;.~ .
.
fully understood from a considerat~on of the ollowing examples .~
... ..
which are gi~en for the purposes of illustration and are not
to be construed as limiting the invention in spirit or in scope;;:.
.. . . .
except as set forth in the appended claims. ~ ~
. . ~ . . .
.. EXAMPLE 1 ..
A series of samples of commereial1y available
sodium carboxymeth~ .cellulose powder having a.~.S.. of ~.4- ..
l.2 are obtained from Hercules, Inc. of Wilmington:, Delaware. .. .
Twenty gram8 of each sample is converted to the acid form by . . ;.
treating with 250 ml~. of a methanol-nitric acid so.1ution (1~0 ml.
2n HN03 in one liter MeOH) for twenty-four hours at 25C. The re~
sulting acidified:material is washed thoroughly wit~distilled .;.;
water and then placed in a reactor wi~h 1000 ml. of distilled
~,
water. Oxygen is.removed ~rom the i~iystem by purging;with
nitrogen for one ha1~ hour. Ten ml. of a ceric ammonium nitrate ..... :
. :;., , . :
, . .
.- . ~ .. .: " ,
. -13- ~ ~
. . .
~, ~ ' ' ,.
: . .
. . . ~.
,~ :.: .
10~5~27 ~;
.
solution (0.1 Molar Ce (IV) in 1 Normal nitric acid) was then ~.
added and, after five minutes, a predetermined quantity of .
acrylonitrile (varying from 5 to 30 rnl.) is added. The reaction "
is allowed to procèed for two hours, at 25C., under a nitrogen ::~
atmosphere. The resulting grafted cellulose ethers are trans~
ferred to a Buchner~funnel and washed thoroughly with water ; ~-.
and acetone. The washed ethers arç then converted to the .' ' :
alkali metal salt ~o.rm by being treated wit~ a 5V,~ 801ution by ''' . ~.
weight Qf potassium hydroxide in methanol for 24 hours at 25C. .'~
The prodùct is washed with methanol and dried at 105C. '' .-
The resulting'series of hydrophobic-polymer :~
grafted alkali metal cellulose ethers are tested to determine the .'
weight percent o~grafted'polymer and the water:and ~salt solution
absorption and re.tention properties. The polymer concentration '
of these samples.'ie.determined by nitrogen analy6i~s wherein -".'
the nitrogen content of the grafted e~thers is obtained by the ''
Kjeldahl method, using an ammonia.electrode, this:method being `~
described in Official Methods and Analysis or the Association o~ '' '
Official Analytical: Chemists, Washington, D.C., 12th ~dition
Edited by W. Horowitz, 1975, code no. 47.023.
Aqueous liquid absorbency is determined by the' `.'~
"XOW Test", wheréin an approximately one-half gram samvle
of the test materLa1 ls accurately weighed and~ stirred into a ''.'."'
bqaker containing 100 ml. o~ the aqueous test ~luid. A~ter ;~.''"~ '
twenty minutes, t~e~mixture i9 fiItered through a piece of nylon '.~
t;;rico abric and àllowed ~o drain for ive minutes. The f;ltrate '"~'.
is collected and measured in the graduated cylinder. The l!~OW", '.~.'.' '.
the absorption capacity'of the material expressed in units o '.
,
grams o~ absorbed liquid per gram of test material'is calculated ~ ~
as follows: ~ ' '.' '
.
~ : ` , , , ' '' '
. . : . . . :
XOW = 100-fil~rate (ml ~
weight of te~,t material (dry)
Aqueous fluid retention capacity i~determined . :
by using a Porous'Plate Testing Apparatus, as described in :i
de~ail in Textile Res. J., 37, pp 356-366, 1967. ~B~le1y, t~is ,,:
test involveg placing the test material in what is essentially, ,
a Buchner funnel having a porous bottom plate and h~ldi~ the .
sample in place by applying thereon a standard weight to maintain ~
,
a standardized confinin~ pressure. The porous plate is placed,,~
in contact with a reservoir of liquid and the':sample is allowed '~
to absorb liquid'through the porous plate until saturated.
. . . ~ . .
By maintaining the,eample at essentially the level of the '.. ,'`,~ ''
, reservoir, the liquid absorbed is sub~ected ~to essentially a '~'"
zero hydraulic head with respect to the reservoir. To determine
liquid retention,~the saturated sample i~ elevated with res~ect ,-'',.~',. .
to the liquid reeervoir thereby imposing a hydraul~c~ head uPon .
the liquld absorbed, the head'arbitrarily chose~ss 35.5 cm. ,'.''~
- of fluid. The apparatus is provided with means for:~directly .,.
measuring the volume of liquid retained under this,hydraulic . ~;i''
head. Reten~ion values~are-repor~ed as the volume retained ~er ,.,'~
unit weight o the'sample. -:' , ,,',: ,,.',
, The-results of these te~ts are tàbulated in Table I ,.:: ~ :
usin~,v~riously, aqueous salt 801ution8 and water'.~ As a control, "';~
ethers, as commercially obtained, are likewi e tested and repor~ed
as "unmodified".~ As a further control, ethers which are acidi- ,': '-~
fled following the above-desoribed procedure and'then:converted '' . ;
back to ~he salt,~~rm withou~ undergoin~ the ~ra~ting reaction
are tested and also reported in Table I a~, "treated controls". ' . "'
': ' - ,';, :"~.
--1 5 - ; .~ . :
. ,~ :. . :.. . ,:
. .
' ! ',
:
~Sl;~
For comparative purposes, wood pulp fibers are also t~:ted and
reported as "cellulose fiber". - ` -i
~: -
Table I
:,
ABSORBENCY OF HYDROPHOBIC POL~IER tP. AN)
. GRAFTED CMC (K-SALT) POWDER
: Absorp~lon Pr~ erties .. :.'
Carboxymethyl -. I~-N~Cl -. ~ l-.S~
Cellulose Polymer . Solution . . Solution . Water
Powder Add-On Retention (cclg) ~DW ~ow
DS (%) ~orous P?ateW 8) ~l~.)
0.4 - O NA ;NA 2 . NA
(unmodified) :;
0.4 ~: O NA ~ NA NA . :
(treated control) , .~ -: : :
Q. 4 3. 9 NA NA . NA
0 4 17 2 8 1; ~2 56 :
0.4 . 38.2 4.4 - 16 ~ . : 18 ~ ::
.
0-7 . O NA ::~NA : NA .`~ :
(unmodified)
~.7 ; O -::~- M~ . , ,NA~ NA, ` ;~:.
(~reated control),
0.7 3.7 NA :-~ :-MA NA
0.7 ~ :: 13.4 ~6.5 22 . 6~ :~ !
0.7 19.5 : $.S 18 : 34 ~: :
0.7 ~ 41.9 ~ 3.4 10 11 '`f'. '"~ :. . ' '
0.9: 0 ~ A NA NA
(unmodified~ ~ : : ::, .:.::
0.9 : ~. 0 ~ . N~ N~ - ~ NA
(treated control)
0.9 :;~ 12.7 ~ ~ NA . NA. NA ::
O.g ~ 25.5 : 5.:8 - 18 18
~ 34.6. ;~ 3:~ 14: 19
1.2 ~ O ~ NA ~ NA NA
(unmodi~ied) : . O NA ~ . ~ ' . '' '~` ' '~
(treated control) : . ,.~: NA
1.2 . 0.7: : N~ . NA~ . NA
1.2 15.Q NA .N~ NA
1.2 ::: 27.4 . 3.3 12 ~ . 20 ,:'-,~
1.2 ~ 41.4 2.3 ~ 9 : 12 : ~.
Cellulo~e Fiber ~ $ 16 ~ 16 - :~
(reerence)
:., : . , ::,
: . NA - Not applicable because ehe materi~l was soluble or gelled in
P~N Polyaerylonitrile ~
.::
' ~ : : ' ' ~ ;. . '
-16~
~S~
: .
As can be 3een from the results of Table I, the
grafting technique of this invention has insolubili7ed the
etherified cellulose and has general:Ly end~wed the resulting
product with absorb~ncy properties (~ROW values) a~ least as
good as those o~ wood pulp. The retention values have
increased markedly. :
EXAMPLE 2
; ' ' '''' ~",~.-
The procedure of Example 1 is carried out with the .. ..
exception tKat the grafted polymer is rendered hydro~hilic ..
by undergoing a.h~drolysis step to conver~ the volyacryloni~
1~ trile to alkali me~al polyacrylate. The acidified grafted :.. : ~ . cellulose ethers reDulting ~rom the grafting step of Example 1 ..
are hydrolyzed by.being refluxed with a solution of 6~, potas~
slum (or where noted, sodium) h~droxide in a solution of 90~/0 ::
ethanol/20% water, by volume, for Qne hour and then:washed ~`~.... :
with an ethanol/water solution and dried at 105~.. Polymer
content and absorption and retention prQpertie3~are determined
by the method described in Exam~le I ànd the results are .
reported ln Table II. ~
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Table II
ABSORBENCY OF HYDROPHILIC POLXMER
~ALKALI METAL-POLYACRYLATE) ~,RAFTED CMC
(ALKALI METAL-SALT) POWDER
Ab~orDtion ProDerties
5Carb~ thyl l~ Cl ~ g/oN-aCl ~-
Cellulose Polymer Solution SolutionW~ter
Pbwder Add-On Alkali RQtention (CC/g) ~ ow ''- '
_ ~/0) M~t l_ POIOUB Plate ~ ~g/p7~(g/~ ,_,_ ''' "',
0.4 O K N~ 1 NA NA
10(urmodifi2d) --
~ 0.4 0 K NA ~A . NA
(treat0d control)
0.4 3.9 K MA ~ ~A NA
0.4 17.2 K 9.1 32 11~
15 0.4 23.1 - Na 10.0 , 24 . .
0.4 37.9 13.8 30 ~2~ .. ', ; -
0.4 38.2 10,5 29 . 119
0.4 - 56.5 ~a 16.5 33 ~ " .. .. :
0.4 79.6 Na 23.8 46 - ` `
0.4 89.~ ~ Na 26.3: 4
' ' ' ~ ~ NA '
( ~ dified) ' . , "
O 0 , ' NA ~ N~ ' '.` ~. . .
(treated control)
0.7 3.7 K NA NA - ~A -^.
0.7 13.4 K : 4.8 40. 98 ~:
0.7 19.~ K 5.9 43 106 ;
0.7 41.~ K 5.3 - 46 . 126
0.7 44.1 :. K - 41 : Na `
0.7 48.2- K 25.0 44 :, Na . .
0.7 71.0 K 19.3 46 Na
0.7 82.9: K ~ 24.4 49 Na ~. '
0.7 91:.5 K 22.6 47 ; -Na ... .
: O.9 O ~ K ~ NA NA ~A
35~ (unKx~fi~d) : :
0.9~ ~ O .: K ~ NA NA ~ ~A
(treated c~ntrol) .
0.9 12.7 K MA NA - . MA ~
. 0.9:: 25.5- K 10.0 42 . : 117 ;-
~:40 0.9 : 34.4-~ K . 8.5 44 100 ::
O.g : 75.5 .: K : : 18.6 42 Na
1.2 . O K ~ N~ - NA: : NA -:
:: ~ 1.2 0 : K ~ ~A ~NA~ : NA~45: (treated c~ntrol) ~ :
: 1.2 0.7 :. K NA NA: N~ ~N~
1 2 15.0;: K : NA NA~ . NA
27.4 K 4.9 43 82
~ 1 22 : ~1 4 ~ ~ K ~; 23 7 45 : NA
:Cellulose Fiber -- 1.5 16 16 .
:(reference)
NA - Nbt applicable because the materiaI wa$ ~oluble in fluid. ;~
- . -18- - .
11)45~LZ~
As in the prior example, it can be seen from
Table II that soluble cellulose ethers have been successfully
insolubilized by grafting. Notwithstanding this insolubilization,
it should be noted that in this case of grafted hydrophilic
polymer moieties, ~he XOW values of t~he grafted ethers far
exceed that of cellulose fibers. As in the foregoing example,
retention values are also greatly improved.
, ' . . . . .
~ EXAMPLE 3 ~ ~
~ . .... . .
,
The procedure of Example 2 is carried out with the
exception that, in~addition to adding acrylonitrile to the
grafting reactor, various quantities of ethyl acrylate are
added so as to grat, to the cellulose, polymer moieties of
both poly(ethyl acrylate) and poly(acrylonitrile~. These grafted ~ :
copolymer ethers are then hydrolyzed in accordance with the
method set out in Example 2, to produce an at least;partially ~:~
hydrophilic polymer moiety grafted to the cellulose ether. The -~
quantity of polymer add-on is determined by measurin~ the
differential weight before and after grafting. Additionally,
. ~ .. ...
the retention and absorbency of these grafted ~opolymer
ethers is measured~and reported in Table III. ,
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Table III
ABSORBENCY OF HYDROLYZED COPOL ~ R
GRAFTED CMC POWDER (Na SALT)
.
XOW . ..
Carboxymethyl Copolymer (g/~) in
5Cellulose Monomer Ratio Add-On 1.5~/~ NaCl ,'
DS in Grafted CMC ~/0)_ Solution
4 ~ O NA
(unmodified)
0 4 ~ - O NA
10 (treated control) 3 ~-
0.41:1 AN /EA4 (hydrolyzed) 82 5 48
0.43:1 AN/EA (hydrolyzed) 84 4 34
0.43:1 AN/EA (hydrolyzed) 84.4 642
0.7 - O NA
(unmodified)
0 7 ~ O NA :-
(treated control)
0.71:1 AN/RA (hydrolyzed) 74.9 51
0.73:1 AN/EA (hydrolyzed) 79.1 35
0.9 - O NA
(unmodified)
(treated control) NA .
0.9 l:l AN/EA (hydrolyzed) 68 3 52
0.9 3:1 A~/EA (hydrolyzed) 71 3 34 ;.
1.2 -
(unmodified) : :
1.2 -
(treated control) .:
1.2 ~ 1:1 (hydrolyzed)74.2 602
1.2 3:1 (hydrolyzed~76.1 37
. .
Cellulose Fiber - - 16 ~,;
(reference)
Hydrolyzed cellulose poly(ethyl acrylate-acrylonitrile) copolymer
35 2 Tendency to Gel ~-
3 r
AN - acrylonitrlle
4 EA - Ethyl acrylat~e
NA - Not applicable because the material was soluble in fluid.
`' . . .
''
11~)45~27 :
As can be seen from the table, the copolymer
grafting has resulted in insolubilizing the otherwise soluble
cellulose ethers. The XOW values show that the copolymer
graft results in a product more absorbent than wood pulp or
the hydrophobic homopolymer graf~ and somewhat less absorbent
than the hydrophilic homopolymer graft.
EXAMPLE 4
. . -. .
A series of fibrous sodlum carboxymethyl cellulose
are prepared in accordance with the method described in Methods ~ ~
of Carbohydrate Chemistry, Vol. III, Edit R. L. Whistler, ~ ;
Academic Press, N.Y. (1963), p. 322, whereby fifteen grams of
southern pine, kraft, fully bleached, wood pulp is slurried `
into 400 mls. of isopropanol. Forty mls. of 23~/o by weight
aqueous sodium hydroxide are slowly stirred into this slurry
for a period of 30 minutes at room temperature. Eighteen
grams of monochloroacetic acid are slowly added, by stirrlng
,
into the mixture for a period of 30 minutes and the mixture
is allowed to react for a period of 3~ hours while~being maintained
at a temperature of 55C. The so-treated fibers are then fil- ;
tered from the reaction mixture and transferred to a beaker P!0 ;
containing a mixture of 707/30~/0 by volume, methanol-water
solution and')sufficient acetic acid is added to neutralize the ;~
so-foxmed slurry. ~The slurry is filtered and the resultin~ ;
fibers are washed; first with a 7~ /30~/~ by volume methanol-water
wash and then with~a 95%j5~iO by volume, methanol-water wash. i~,
-21-
; .,
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The washed fibers are dried at 70 C for two hours. The re~
sulting product is fibrous sodium carboxymethyl cellulose ::
having a degree of substitution of 0.64. Various quantities,
as reported in Table IV below, of hydrolyzed acrylonitrile :
homopolymer and acrylonitrile/ethyl acrylate copolymer are
grafted to the fibrous cellulose ethers following ~he procedures .:~
of the foregoing examples 2 and 3. The XOW values for these
graf~ed samples as well as treated and untreated controls and -:: :
a comparative unetherified cellulose fiber sample, are . -
10 likewise reported in Table IV. :
~- '; ',. '
.
Table IV
ABSORBENCY OF HYDROPHILIC POLYMER GRAFTED
TO Na CMC FIBER AND HY~ROLYZRD COPOLYMER :
GRAFTED TO Na CMC FIBER -:.
: ., . . :
Total : XOW .`.
Carboxymethyl : Polymer ~glg) in ,. ~.
15Cellulose Monomer Ratio Add-On 1.5~/. NaCl
DS in Grafted CMC (~!~_ Solution
0.64 - 0 Solublé .
~ !
(Na-Salt)
0.64 - 0 ~ Soluble .
20 (treated control - : -~
:K-Salt~ ~ ~
Na 0.64 :~ : AN (hydrolyæed) 74.8 51 . :
Na 0.64 ~ AN (hydrolyzed) 88.6 , 82* . .::
Na 0.64 . : AN (hydrolyzed) 88.6 46
25Na 0.64 AN (hydrolyzed) 88.6 ~ 45 -
Na 0.64 : 3:1 AN/EA (hydrolyzed) 83.9 40 -:
Na 0.64 1:1 AN/EA (hydroIyzed) 69.9 48 - .
Na 0.64 : 1:1 AN/EA (hydrolyzed) 82.9 49
Na 0.64 :1:1 AN/EA (hydrolyzed) 87.8 40 ~^:
30Na 0.64 ~:3 AN/EA (hydrolyzed) 81.3 59
. Na 0.64 ~ EA (hydrolyzed) 83.6 100*
Cellulose Fiber `~ -
(reference) ~ - 0 16
.: .
* Tendency to form gel : ~ -
. . :
, .,:
-22~
.....
:
~ 5~
Comparative Example
For comparative purposes, unmodified and several ,~
chemically modified cellulosic materials are evaluated for their
fluid retention and XOW values and tabulated in Table V which
follows. The material designated as '~Cellulose Fibers" is
untreated, comminuted, southern pine, kraft, fully bleached
wood pulp. The material designated "CMC" is sodium carbo~ymethyl
cellulose powder having a D.S. of 0.35 or greater and obtained ~`
from Hercules, Inc. The material designated as "Crosslinked
,: , , ,
CMC" is wet crosslinked sodium carboxymethyl cellulose made in ;
accordance with the methods described in the aforementioned
U.S. Patent 3,589,364 issued to Dean, et al. The material `
designated as '`Hydrolyzed PAN Grafted Cellulose" is a natural, ; ~
unetherified cellulose having grafted thereto a completely hydro- ` ;
philic hydrolyzed poly (acrylonitrile) homopolymer, said polymer
.,. : - : ...
constituting approximately 66% by weight of the grafted fiber. ;;
The material designated as "Hydrolyzed Copolymer Grafted Cellu- ~ ~
lose" is an unetherified cellulose having grafted -thereon a - ~; -
partially hydrolyzed acrylonitrile/ethyl acrylate copolymer in
a 50/50 molar monomer ratio, said copolymer representing
approximately 90% by weight of the grafted cellulose and being
the material described and cIaimed in our aforementioned U.S.
Patent 3,889,678. These materials are compared, for their - - `
fluid retention and XOW values, to samples of the etherified
grafted cellulose of this invention, also tabulated below and
referenced to tables herein.
'.,'~
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~IL1)4~7
Table V
COMPARISON OF ABSORP~ION CAPABILITI~S
OF IiIF FER~:NT ABS(:)RBE~JT FIBI~RS AND .
SEI.ECTED POL~R GR~FTED ~a CMG 5A~LES
Fluid
Retentioll XOW ~ .
Material ~ c/g) (~/g) in ..
De8cription 1% ~aCl 1~5% ~aCl .;
Materials ~Refere!~ices Solution Solu~ion
Cellulose Fibers - . :1. 5 : 16
.
C~: (DS ~ O. 35) . _ Dissolved D~solved ~:
, ~ .
C~osslinked ~IC :.
(DS _~0. 7) . - ~ . IO 22-24 l -
Hydrolyzed PA~ 14~ ; 27-28
Graft~d Cellulo~e ~ .
- . ~ . , . . -
Hydrolyzed Copolymer ~ : 11 . 2 2- 26 -
Graf~ed Ce}lulo3e~
Poly~er Gr`aftad CMC . ~. ~
0 . 4 DSi56 . $70~0I~er . See Table I~E . 17. . . 33
0.4 DS/79. 6~ Polymer. - -do- . . - 24: :46
O. 4 DS/89 . 9% Polymer . -do- . 2~ - 46
0.7 DS/42.~% Polym~r : -do- : 25 . 44
0.7 DS/7L.0% Polymer -do~ 19 ~ 46
0.7 DS/82.9% Polymer -do- .: . 24 49
0.9 DS/75:.5% Polymer -doD i :19 . ~ 42
1.~ lDS/77.1Z Poly~er -do~ 4 . 45
0.4 DS/84.4% Copolymer See Table IlI _ : ~ 64
O. 7 DS/74. 97~ opol~rmer. -do- . : - 51
0. 9 DS/68.3% ~Cop~lymer -do- ~ . 52
--24--
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3L~45~Z~
As Table V shows, in all cases, the materials
of this invention exceeded, both in fluid retention and in
XOW values, each o~ the samples of the various other chemically
modified and unmodified cellulo8ics to which ~hey were compared.
.
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