Note: Descriptions are shown in the official language in which they were submitted.
~23~7~Z~L
POLYSACCHARIDE DERIVATIYES CONTAINING AlDEHYDE
GROUPS, THEIR PREPARATION FROM THE CORRESPONDING ACETALS
AND USE AS PAPER ADDITIYES
The present invention relates to polysaccharide derivatives
containing aldehyde groups and to the acetal derivatives used in the
preparation thereof. It also relates to a non-oxidative process for
introducing aldehyde groups into polysaccharides. It further relates
to the use of the cationic aldehyde-containing derivatives as paper
additives.
As used herein, the term "paper" includes sheet-like rnasses and
molded praducts made from fibrous cellulosic materials which may be
derived from natural sources as well as from synthetics such as poly-
amides, polyecters, and polyacryliç resins, and from material fibers
such as asbestos and glass. In addition, papers, made from combinations
of cellulosic and synthetic materials are applicable herein. Paper-
board is also included within the broad term "paper".
c Oxidative and non~oxidative methods have been used to introduce
aldehyde groups into polysaccharides such as starches, gums, celluloses.
The oxidative methods used have included treabment with periodic acid,
periodates, or alkali metal ferrates. See U.S. Pat. No. 3,086,969
(issued April 23, 1963 to J. E. Slager) which discloses an improved
process for the preparation of a dialdehyde polysaccharide, ~e.g.,
starch) using periodic acid; U.S. Pat. No. 3,062,652 ~lssued Nov. 6,
1962 to R. A. Jeffreys et al.) which discloses the preparation of
dialdehyde gums (e.g., gum acacia, pectin, and guar) using periodate or
periodic acid; and U.S. Pat. No. 3,632,802 (issued Jan. 4, 1972 to J. N.
.
7h2~
- 2
BeMiller et al.) which discloses a method for oxidizing a carbohydrate,
(e.g., starch or cellulose) with an alkal; metal ferrate.
In the above methods the aldehyde groups are formed by the oxi-
dation of the hydroxyl groups on the ring and/or side chain. Treatment
with periodic acid or periodate selectively oxidizes the 2~3-glycol
struc~ures (i.e., the adjacent secondary hydroxyl groups on the ring
carbon atoms), cleaves the ring, and results in a "so-called" dial-
dehyde derivative which is principally a hydrated hemialdal and intra-
and intermolecular hemiacetals. Treatment of carbohydrates with alkali
metal ferra~es selectively oxidizes the primary alcohol group on the
side chains ~ithout ring cleavage or oxidation of the ring hydroxyls.
The disadvan~ages o~ the oxidative method include degradation to
lower molecular weight products and the formation of carboxyl groups
due to further oxidation of the aldehyde groups. U.S. Pat. No.
3,553,193 (issued Jan. 5, 1973 to D. H. LeRoy et al.) describes a
method for oxidizing starch using an alkali metal bromite or hypo-
bromite under carefully controlled conditions. The resulting dialde-
hyde is reported to have a substantially greater proportion of carbonyl
groups li.e., aldehyde groups) than carboxyl groups. It also discloses
a method for selectively oxidizing the side chains of starch deriva-
tives (e.g., an alkoxylated starch such as dihydroxypropyl starch)
under the same process conditions whereby the underivatized starch
hydroxy groups on the rings are substantially non-oxidized.
The presence of carboxylic groups in aldehyde starches has several
disadvantages in addition to the obvious reduction in the degree of
aldehyde substitution. These include the introduction of hydrophilic
properties due to the carboxyl groups, an upset in the cationic/anionic
1~3'71~:~
ratio when a cationic starch base is used (as in most papermaking wet
end uses), and the possible formation of salts (in the above paper-
making end use) which could give rise to ionic crosslinking.
The non-oxidative methods typically involve the reaction of the
polysaccharide with an aldehyde-containing reagent. See U,S. Pat. Nos.
3,5~9,618 (issued July 7, 1970 to S. M. Parmerter) and U.S. Pat. No.
3,740,391 (issued June 19, 1973 to L. L. Williams et al.) which cover
starch derivatiYes and U.S. Pat. No. 2,803,558 (issued Aug. 20, 1957 to
G. D. Fronmuller) which covers a gum derivative. The starch deriva-
tive of Parmerter is prepared by reaction with an unsaturated aldehyde(e.g. acrolein) and has the structure Starch-O-CH(Rl)-CH(R2)-CHO where
Rl and R2 are hydrogen, lower alkyls or halogen. The starch derivative
of Williams is prepared by reaction with acrylamide followed by reaction
O OH
Il I
with glyoxal and has the structure Starch-O-CH2-CH2-C-NH-CH-CHO. The
gum derivative of Fronmuller is prepared by treating the dry gum (e.g.,
locust bean or guar gum) with peracetic acid to reduce the viscosity,
neutrali~ing, and then reacting with glyoxal. Water-soluble cellulose
ethers (e.g., hydroxyethylcellulose) have also been reacted with
glyoxal or ureaformaldehyde to give aldehyde-containing derivatives.
One of the disadvantages of introducing the aldehyde groups directly
using an aldehyde-containing reagent is the possibility of the deriva-
tive crosslinking prior to use. This is a particular disadvantage
when the products are being used to impart ~emporary wet strength to
paper via a crosslinking reaction with the cellulose fibers. The
Williams patent (cited above) alludes to this problem when it notes
~237~
-- 4 --
tha~ solutions of the glyoxalated polymers "are stable for at least a
week when diluted to 10~ solids by weight and adjusted to pH 3" (see
Col. 3, lines 60-63). The Parmerter patent notes that the starch
aldehyde is "a substantially non-crosslinked granular starch deriva-
tive" and discusses the importance of the non-crosslinked character
(see Col. 2, lines 40-45).
Therefore there is a need for aldehyde-containing polysaccharide
derivatives and an improved non-oxldative method for their preparation
which does not crosslink thP derivative.
The present inven~ion provides novel polysaccharide aldehyde deriva-
O qH
tives which have the formula Sacch-O-CH2-R-C-N-R2-CHO, Sacch-O-CH-C-CHO,
R1 R R4
OH R!6
Sacch-O-CH2-CH-R5-N+-R8-CHO Y~, as well as novel polysaccharide
R7 o ,OA
acetals which have the formula Sacch-O-CH2-R9-C-N-R2-C ? , or
Rl `OA'
OH / OA OH ~6 ,OA
Sacch-O-CH-C-CH , or Sacch-O-CH2-CH-R5-N+-R8-CH . Y~.
R3 R4 ~OA ' R7 OA'
It also provides a polysaccharide aldehyde having the formula
Sacch-O-R10-CHO prepared by hydrolyzing, at a pH of 7 or less, a
OA
polysaccharide acetal having the formula Sacch-O-R10-CH which is
\ OA'
~237~æ~L
prepared by reacting the polysaccharide, at a pH of about 9 or above,
with an acetal reagent which does not substantially crosslink or
oxidi~e the polysaccharide during the reaction. The reagent is
described hereafter.
In the above formulas Sacch-O- represents a polysaccharide mole-
cule (wherein in the hydrogen of a hydroyxl group of a saccharide
unit has been replaced as shown); R is (CH2)n or a divalent aromatic
group and n is zero or greater; R9 is (CH2)n or a divalent aromatic
group and n is zero or greater, with the proviso that n is 1 or more
when the polysaccharide molecule is a starch molecule; R1, R6 and R7
are hydrogen, an alkyl (preferably methyl), aryl, aralkyl, or alkaryl
group; R2, R5 and R8 are (CH2)m with m being 1-6 (preferably 1-2);
R3 and R4 are hydrogen or a lower alkyl3 preferably methyl; R10 is a
divalent organic group, containing no starch-reactive substituents; A
and A' are independently a lower alkyl or A and A' together form at
least a 5-membered cyclic acetal; and Y is an anion such as a halide,
sulfate, or nitrate. The polysaccharide molecule may be modified by
the introduction of cationic, anionic, nonionic, amphoteric, and/or
zwitterionic substituent groups. As used herein, the terms "cationic"
and "anionic" are intended to cover cationogenic and anionogenic groups
and the term "reactive substituents" refers to substituents which react
with polysaccharide to form a covalent bond.
The aldehydes are prepared by hydrolyzing the corresponding acetal
at a pH of less than 7, preferably 5 or less, most preferably 2.U-4~0.
5 The acetals are prepared by reacting the polysaccharide with an
/ OA
acetal reagent having the general structure Z-R11-CH , where Z is
\ OA'
~Z37~2~
- 6
an organic group capable of reacting with the saccharide molecule to
form an ether derivative and selected from the group consisting of an
epoxide, a halohydrin, an ethylenically unsaturated group, and a
halogen and Rl1, if present, is a divalent organic group containing
5 no reactive substituents.
O OA
Typical reagents have the formula X-CH2 R9-~-N-R2-CH
R1 \ OA'
O / OA ~ O / OA R3 ~4 / OA
10 CH2=CH-C-N-R2-CH , H - C---CH , HC - C-CH , or
R1 `OA' R3 R4 \ OA' I 1H \ OA'
O R6 OA
H ~ -~ H_R5_N+_R8_CH , where R1 to R9 and A and A' are as
l7 \ OA'
defined above and X is chlorine, bromine, or iodine. In the halohydrin
reagent the halogen and hydroxyl groups may be interchanged.
The aldehyde and acetal derivatives are useful in conventional appli-
cations where water soluble or water swellable polysaccharide deriva-
tiYeS are useful, for example, as coatings, adhesives and paper additives.
The cationic aldehyde-containing derivatives are particularly useful as
paper additives. They are useful as temporary wet strength additives,
for example in tissue/toweling paper stocks, and as wet and dry strength
additives for all paper types including liner board. Typical cationic
and cationogenic groups include the diethylaminoethyl ether groups
introduced by reaction with 2-diethylaminoethylchloride hydrochloride
or 3-(trimethyl ammonium chloride)-2-hydroxypropyl ether groups~intro-
duced by reaction with 3-chloro-2-hydroxypropyl trimethylammonium
~1~3712~
chloride.
When the polysaccharide is starch, applicable starch bases which
may be used herein may be derived from any plant source including corn,
potato, sweet potato, wheat, rice, sago, tapioca, waxy maize, sorghum,
high amylose corn, or the like. Starch flours may also be used as a
starch source. Also included are the conversion products derived
from any of the former bases including, for example, dextrins prepared
by the hydrolytic action of acid and/or heat; oxidized starches
prepared by treatment with oxidants such as sodium hypochlorite;
fluidity or thin-boiling starches prepared by enzyme conversion or mild
acid hydrolysis; and derivatized and crosslinked starches. The starch
base may be a granular starch or a gelatinized starch, i.e. non-
granular starch.
When the polysaccharide is gum, applicable bases which may be
used herein are polygalactomannans, which are heteropolysacchrides
composed principally of long chains of 1-~4 ~ -D-mannopyranosyl units to
which single unit side chains of ~ -D-galactopyranosyl units are joined
by 1--~6 linkages and hereafter referred to as "gums". Also included
are degraded gum products resulting from the hydrolytic action of acid,
heat, shear, and/or enzyme; oxidized gums; and derivatized gums. The
preferred gums include gum arabic, as well as guar gum and locust bean
gum because of their commercial availability.
When the polysaccharide is cellulose, applicable ~ases useful herein
include cellulose and cellulose derivatives, especially water-soluble
cellulose ethers such as alkyl and hydroxyalkylcelluloses, specifically
methylcellulose, hydroxypropylmethyl cellulose, hydroxybutylmethyl-
- cellulose, hydroxyethylmethylcellulose, and ethylhydroxyethylcellulose.
~23~
Methods for preparing the modified polysaccharide bases are well-
known to those ski11ed in the art and discussed in the literature.
See, for example, R.L. Whistler, Methods in Carbohydra~e Chemistry,
Yol. IV, 1964, pp. 279-311; R.L. Whistler et al., Starch-Chemistry and
Technology, Vol. II, 1967, pp. 293-430; R.L. Davidson and N. Sittig,
Water-Soluble Resins, 2nd Ed., 1968, Chagter 2; and R.L. Davison, ~land-
book of Water-Soluble Gums and Resins, 1980, Chapters 3, 4, 12 and 13
directed to cellulose derivatives, Chapters 6 and 14 directed to gums,
and Chapter 22 directed to starch.
The starch reactions with the derivatizing reagents that introduce
the acetal groups are carried out using the general procedure described
in U.S. Pat. No. 3,880,832 issued April 29, 1975 to M.M. Tessler. Granu-
lar reactions are typically carried out in water at 20-50C, preferably
about 40-45C. Non-granular starch reactions may be carried out at
higher temperatures (e~g., up to 100~C). Tne reaction mixture is pref-
ferably agitated. Reaction time may vary from 0.5-2a hours, preferably
8-16 hours, for aqueous reactions or from 1-8 hours for reactions
carried out in a substantially dry reaction medium. It will depend on
such factors as the amount of reagent employed~ the temperature, ~he
scale of the reaction, and the degree of substitution desiréd. The pH
is maintained at 10-13, preferably 11-12, during the reagent addition
and during the entire reaction using a base such as sodium, potassium,
or calcium hydroxide. Sodium sulfate is typically added to the reac-
tion mixture to reduce swelling of the granular starch, it is not used
when calcium hydroxide is the base.
Potassium or sodium iodide is a good catalyst for reacting the chloro-
- acetylated amine derivatives, but it is not necessary for a satisfac-
~31~2~
- 9 -
tory reaction with the starch. After completion of the reaction, the
excess alkali is neutralized and the pH is adjusted to 7-8 using any
conventional acid prior to recovery of the starch. If the final pH of
the starch derivative is less than 5-6, the derivatives may crosslink
with time and disperse poorly or not at all.
The gum reactions with the acetal reagents are carried out in a
two-phase reaction system comprising an aqueous solution of a water-
miscible solvent and the w~ter-solubl~ reagent in contact with the solid
gum. The water content may vary from 10 to 60~ by weight depending upon
the water-miscible solvent selected. If too much water is present in
the reaction system, the gum may swell or enter into solution thereby
complicating recovery and purification of the derivative. The water-
misci~le solvent is added in the amount sufficient for the preparation
of a slurry which can be agitated and pumped. The weight ratio of water-
miscible solvent to gum may vary from 1:1 to 10:1, preferably from
1.5:1 to 5:1. Suitable water-miscible sol~ents include al~anols, glycols,
cyclic and acylic alkyl ethers, alkanones, dialkyformamide and mixtures
thereof. Typical solvents include methanol~ ethanol, isopropanol,
secondary pentanol, ethylene glycol, acetone, methyethylketone, diethyl-
ketone, tetrahydrofuran, dioxane, and dimethylformamide. The reaction
times and temperatures used for the aqueous reactions are suitable for
the solvent reaction.
The cellulose reactions with the acetal reagents are conveniently
carried out using the procedure of U.S. Pat. No. 4,129,722 (issued Dec.
12, 1978 to C. P. Iovine et al.). The cellulose or cellulose deriva-
tive is suspended in an organic solvent and a water solution oF the
derivatizing reagent is added thereto. Derivatization in the resultant
..
,
~23~
- 10 -
two-phase mixture is ordinarily carried out with agitation at tempera~
tures of 30 to 85C., adding alkali iF necessary to effect reaction.
At least one of the initial phases (i.e., the suspended cellulose or
cellulose derivative or the aqueous reagent solution) contains a suit-
able surfactant. It is important that the organic solvent used in theinitial cellulose phase be immiscible with the aqueous derivatizing
reagent phase, that it not dissolve the cellulose derivative as it is
formed, that it have a boiling point at or above the temperature of the
derivatizing reaction, that it be insensitive to alkali and not parti-
cipate in the derivatization reaction.
The two phase procedure may also be used to prepare starch and gumderivatives as well as cellulose derivatives. It may also be used to
prepare derivatives containing substituents derived from different
reagents without isolating the substitution product from each reagent.
This multiple substitution may be accomplished by the addition of
several different reagents to the substrate-surfactant alkali mixture
at the same time or sequentially.
After completion of the acetal reaction the solid acetals may be
separated, if desired, from the reaction mixture by centrifugation or
filtration. Preferably, the derivative is purified by washing with
water in the case of the starch derivatiYes, with the aqueous solution
of water-miscible solvent in the case of the gum derivatives or with
the solvent in the case of the cellulose derivatives. Further washing
with a more anhydrous form of the same solvent may be desirable for the
gum derivatives. The derivatives are then dried using conventional
methods, as in a vacuum, drum, flash, belt, or spray drier.
The conversion of the polysaccharide acetals to the aldehydes is
~L23~Z~
carried out under acidic conditions, typically at a p~l of 6 or less,
preferably 5 or less, most preferably at 2-3. It may be carried out
directly without isolation of the acetal or the acetal may be isolat-
ed as above and resuspended in water prior to conversion. If desired,
the derivatives may be recovered as described above.
In addition to preparing the above aceta~s, or aldehydes, modified
derivatives may be prepared which contain other substitutent groups,
hydroxyalkyl groups (e.g., hydroxypropyl ether groups), carboxyalkyl
ether groups (e.g., carboxymethyl), ester groups (e.g., acetate
groups), tertiary amino groups ~e.g., diethylaminoethyl ether groups),
and quaternary amine groups, (e.g. 3-(trimethylammonium chloride)-
2-hydroxypropyl grops or 4-(trimethylammonium chloride)2-butenyl
groups), introduced prior to or subsequent to reaction with the acetal
derivatizing reagent or introduced simultaneously by reaction with the
acetal reagent and other derivatizing reagent.
The aldehyde derivatives used as paper additives preferably con-
tain cationic (e.g., such as the quaternary ammonium and teriary
amine group discussed above), amphoteric, and/or zwitterionic groups.
These derivatives are dispersed in water before use. The granular
starch derivatives are cooked to provide the dispersed derivative.
The starch may be cooked prior to derivatization to form the
acetal, subsequent to derivatization, after conversion to the aldehyde,
or most conveniently during conversion of the acetal to the aldehyde.
Cooking at pH 6 or less simultaneously converts the acetal to aldehyde
and solubilizes and disperses the starch aldehyde. Any conventional
cooking procedure may be used, such as cooking a slurry con~aining the
water-soluble or water-swellable derivative in a boiling water bath for
~23~
- 12
about 20 minutes, blowing in steam to heat the slurry to about 93C
(200F), or jet cooking. If a water-dispersible or water-soluble
starch base is used for the preparation of the acetal, it will not be
necessary to cook the acetal during the acid hydrolysis.
The aldehyde derivatives described herein may be used as beater
additives, although their addition to the pulp may occur at any point
in the paper-making process prior to the ultimate conversion of the wet
pulp into a dry web or sheet. Thus, for example, they may be added to
the pulp while the latter is in the hydropulper, beater, various stock
chests, or headbox. The derivatives may also be sprayed onto the wet
web. If the derivative is trapped in the wet fibers after spraying,
it may not be necessary to use cationic aldehyde derivatives but they
are preferred.
The aldehydes herein may be effectively used for addition to pulp
prepared from any type of cellulosic fibers, synthetic fibers, or
combinations thereof. Among the cellulosic materials which may be used
are bleached and unbleached sulfate ~Kraft) bleached and unbleached
sulfite, bleached and unbleached soda, neutral sulfite, semi-chemical
chemiground wood, ground wood or any combination of these fibers.
Fibers of the viscous rayon or regenerated cellulose type may also be
used if desired.
Any desired inert mineral fillers may be added to the pulp which is
to be modified with the aldehydes herein. Such materials include clay,
titanium dioxide, talc, calcium carbonate, calcium sulfate and diatomac-
ous earths. Rosin or synthetic internal size may also be present ifdesired.
The proportion of the aldehyde to be incorporated into the paper
";l
L~ . ~,. * Trade Mark
~37~Z4
- 13
pulp may ~ary in accordance with the particular pulp involved and the
properties desired (e.g., wet strength, temporary wet strength, or dry
strength). In general, it is preferred to use 0.1-10~, preferably
0.25-5% of the derivative, based on the dry weight of the pulp.
Within this preferred range the precise amount which is used will
depend upon the type of pulp being used, the specific opera~ing condi-
tions, the particular end use for which the paper is intended, and the
particular property to be imparted. The use of amounts greater than
5~, based on the dry weight of the pulp, is not precluded, but is
ordinarily unnecessary in order to achieve the desired results.
In the examples which follow, all parts and percentages are given
by weight and all temperatures are in degrees Celsius unless otherwise
noted. Reagent percentages are based on dry polysaccharide. The
nitrogen content of the cationic bases and resulting acetals was
measured by the Kjeldahl method and are based on dry polysaccharide.
In the paper tests, the tensile strengths are reported as breaking
length (m.j. The breaking 1ength is the calculated limiting length of
a strip of uniform width, beyond which, if such as strip were suspended
by one end, it would break of its own wei~ht. The breaking length
(air dry) in meters (m.) is calculated using the formula B.L. = 102,000
T T'
R = 3,658 R', where T is tensile strength in kN./m., T' i5 tensile
strength in lb./in., R is grammage (air dry) in g./m.2, and R' is weight
per unit area (air dry in lb./1000 ft.2). Paper specimens are selected
in accordance with TAPPI T 400 sampling procedure. Those evaluated for
wet strength and temporary wet strength were saturated with distilled
water by immersion and/or soaking until the paper sample was thoroughly
~237~Z4
- 14 -
wetted. The strength was evaluated in accordance with TAPPI T 494 om-82.
The measurements were carried out using a constant rate of elongatlon
apparatus, i.e. a Finch wet strength device, which is described in TAPPI
Procedure T 456 om-82 (1982). The dry strength was evaluated in accor-
dance with TAPPI T 494 om-81.
Example I
This example describes the preparation of known cationic starch
acetals by several methods using various starch bases. The reagents
used for preparing the starch acetals have the general formula
0 / OA
X-CH2-C-N-R2-CH , where R1 is H or -CH3, R2 is -CH2-, A and A'
R1 \ OA'
are - CH3 or -C2Hs, and X is Cl or Br. They are prepared by reacting
a haloacetyl halide with aminoacetaldehyde diethyl acetal or methyl-
aminoacetaldehyde dimethyl acetal as described below.
Acetal Reag nt Preparation
Reagent A - N-(2,2-Dimethoxye~hyl)-N-methyl-2-chloracetamide, which has
!l /OCH3
the formula Cl-CH2-C-N-CHz-CH , is prepared by adding chloroacetyl
IH3 OCH3
chloride ~29.05 9.) dropwise to a stirred mixture of methylaminoacetal-
dehyde dimethyl acetal ~33.5 9.) in toluene (170 ml.) and 20~ aqueous
sodium hydroxide (52.9 9.). The reaction was cooled by ;mmersion in an
ice/brine bath and the addition rate was adjusted to maintain the reac-
tion temperature at 0-5C. The total addition took 10 mins. at which
time the cooling bath was removed. Agitation was continued for an ad-
ditional 10 mins. and the phases were then separated. Excess toluene
~%37~2q~
- 15 -
was removed from the upper organic phase by distillation at the aspira
tor to gi~e Reagent A as a brown liquid.
Reagent B - N-(2,2-Diethoxyethyl)chloroacetamide, which has the formula
e ,oc2H5
Cl-CH2-C-y-cH2-cH , was prepared as above except that aminoacet-
H OC2Hs
aldehyde diethyl acetal (37.4 9.) was substituted for the methylamino-
acetaldehyde dimethy7 acetal. The product was isolated as a yellow
waxy solid.
Reagent C - N-(2,2-Dimethoxyethyl)-N-methyl-2-bromoacetamide, which
1 / OCH3
has the formula Br-cH2- -1_CH2_CH , was prepared in the same way
CH3 \ OCH3
as Reagent A except that bromoacetyl chloride (40.4 g.) was substituted
for the chloroacetyl chloride. The product was isolated as a brown
liquid.
Starch Reactions
Part A. Consecutive Reactions Usin~ Cationic Reagent Followed by
Acetal Rea~ent
(1) A waxy maize starch (250 g.) was slurried in 375 ml. of
water. To the slurry was added 2.3~ calcium hydroxide (Ca(OH)2)
followed by 6.3~ of a 50~ aqueous solution of 2-diethylaminoethylchloride
hydrochloride (DEC). The reaction was run at 40C. for S hrs. A 10~
aqueous hydrochloric acid solution (HCl) was added to adjust the pH to
3Ø The mixture was filtered and the solids washed. A portion of the
filter cake containing 50 g. of the cationic starch ether was dried and
analyzed. Cationic N was 0.28~.
The remaining filter cake (about 200 g. starch) was reslurried in
~37~
- 16 -
150 cc water; 80 9. of sodium sulfate (Na2S04) were added; and the pH
was raised to about 11.0-11.5 by adding a 4.5~ sodium hydroxide (NaOH)
solution containing 10~ NazS04. A total of 19.0 9. (9.5~ of Reagent
A was added. The slurry was placed in a bath at 45C for 16 hrs. while
maintaining the pH above 11.0 with the 4.5~ NaOH solution. The pH was
adjusted to about 7.0-8.0J with 10~ HCl. The resulting product was
filtered, washed with water adjusted to pH 7.0-8.0, and dried. It con-
tained 0.72~ total N. The nitrogen content due to the acetal substitu-
ent was 0.44~.
(2) The DEC reaction was carried out as in (1) except that corn
starch was used. Cationic N was 0.29~. Acetal reaction was carried out
using 5~ potassium iodide (KI) as a catalyst (see U.S. Pat. No. 3,880,832
cited previously). A total of 1000 9. of the cationic corn starch was
suspended in 1250 ml. of water containing 300 g. Na2S04. An aqueous
solution of 40 9. NaOH, 50 9. Na2S04, and 710 9. water was added
slowly to the starch slurry. Then 300 9. of Reagent B were added all
at once followed by the KI. Reaction conditions were 16 hr. at 45C.
The derivative was recovered as above but, after washing, it was resus-
pended in water and 5 9. sodium bisulfite was added. The slurry was
~iltered but not washed. The bisulfite salt prevents oxidation of the ~~
salts to iodine which produces a brown color. Acetal N was 0.41~.
(3) The DEC reaction was carried out on a waxy maize starch using
the procedure of (1) except that 40~ Na2S04 was used to repress swel-
ling and 4.5~ NaOH was used to maintain the pH at above 10.8. Cationic
N was 0.232~. The acetal reaction was ~arried out as in (1) except that
11~ Reagent A (based on about 200 9. starch remaining in the slurry) was
used. No Na2S04 was added. The pH was adjusted to above 10.8 with
4.5~ NaOH. Reaction conditions were 19 hr. at 40~C. Acetal N was 0.37~.
~37~LZ~
- 17 -
(4) The DEC and acetal reactions were carried out on a waxy maize
starch using Reagent A (9.5%) and the procedure of (3) except that 12
aqueous potassium hydroxide was used to control the reaction and no
Na2S04 was used. Cationic and acetal N were 0.25~ and 0.45~ respect
ively.
(5) The DEC reaction was carried out on a waxy maize starch using
the procedure of (3). Cationic N was 0.26~. The acetal reaction was
carried out in 300 ml. of water containing 80 g. Na2S04. The pH was
adjusted to 11.~-11.5 using the NaOH/Na2S04 solution of (1). Reagent
A (11~) was used; the reaction conditions were 19 hr. at 30C. Acetal
N was 0.40~.
(6) The DEC and acetal reactions were carried out as in (5) except
at 50C. Cationic and acetal N were 0.26~ and 0.32~ respectively.
Part B. Simultaneous Reaction
(1) An unmodified waxy maize starch was slurried in water and
3.15~ DEC and 12~ Reagent A were added while maintaining the pH above
11.0 with a 4.5~ NaO~ solution. The reaction mixture was maintained at
45C and pH 11.0-11.5 for 16 hr. and then neutralized to pH 7.5. The
product was recovered as above. It had a total N content of 0.77~.
(2) A similar reaction was carried out using potato starch (200 9.)
and 16 parts of a 50~ solution of 3-chloro-2-hydroxypropyl trimethyl
ammonium chloride and 12~ Reagent A. The product contained 0.91~ total
N. Cationic N was not determined (theoretical was about ~.3~ maximum).
The potato starch base contained about 0.013~ N. Acetal N should be
about 0.60~.
Part C Consecutive Reaction Using Acetal Reagent Followed by
_ationlc Reagent
An unmodified waxy maize starch (1000 9.) was slurried in 1500 cc.
3~
- 18 -
water containing 400 9. Na2S04, and the pH was raised to 11.2 with a
NaOH solution made by dissolving 40 9. of solid NaOH and 90 y. Na2S04
in 7709. water. The above acetal reagent A (10~ was added and the
reaction was maintained at pH 11.2 and 45C for 16 hrs. The product
S (recovered as above) had an acetal N content of 0.57~.
The resulting acetal (200 9.) was reacted with 16 g. of the 50%
aqueous DEC solution as described in above. The final product con-
tained 0.72% total N.
Part D. Dry Reaction
200 9. of a cationic, waxy maize starch (0.26~ nitrogen) made as
in Part A - No. 3 were impregnated in a Hobart mixer with a solution
consisting of 24 g. acetal reagent A, 2.5 9. NaOH and 24 cc water.
After stirring to insure a homogeneous blend, the sample was placed in
a jar in an oven at 75C. After 2 hrs. the sample was suspended in
95-100~ ethanol and filtered. The resulting filter cake was resuspended
in a 1:1 (by volume) ethanol-water mixture, pH was adjusted to 7.5, and
the sample was filtered and washed repeatedly with the 1:1 ethanol-
water. Final nitrogen on the purified product was 0.48~J and therefore
an acetal nitrogen of 0.22~ was obtained by the "dry" reaction.
Example II
This example describes the preparation of novel starch acetals
using reagents other than the acetamide reagents of the previous example.
Acetal Reagent Preparation
Reagent D - N-~2,2-Dimethoxyethyl)-N-methyl-3-chloropropionamide, which
0 ~ OCH3
has the formula Cl-cH2-cH2-c-7-cH2 CH , was prepared according
. CH3 ~OCH3
to the procedure used to make Reagent A except the chloropropionyl
~;~37~
- 19 -
chloride (32.7 g.) was substituted for chloroacetyl chloride. The
product was isolated as a pale yellow 1iquid.
N-(2,2 Dimethoxyethyl)-N-methyl acrylamide, which has the
o OCH3
formula CH2=CH C-N-CH2-C ~ , was prepared according to the proce-
CH3 \ OCH3
dure used to make Reagent A except that acryloyl chloride (23.3 9.) was
used instead of chloroacetyl chloride and 4-t-butylcatechol (0.1 g.)
was added to the organic phase before removal of the solvent. The
final product was isolated as a clear liquid by distillation (65-66C
0.2-0.3 mm Hg.).
Reagent F - 1,2-Epoxy-3,3-dimethoxypropane, which has the formula
~ 0 ~.OC2H5
CH2 - CH-CH , was prepared from acrolein as descr1bed D. T.
OC2H5
Weisblat et al. See J. Am. Chem. Soc., Vol. 75, p. 5~93 (1953).
Reagent G - N-(2,2-Dimethoxyethyl)-N,N-dimethyl-N-(2,3-epoxypropyl)
ammonium chloride, which has the formula
/ O \ CH3 / OCH3
CH2 - CH-CH2-N+-CU2-CH Cl~, was prepared by adjusting the
CH3 \ OCH3
pH of a 40~ solution of dimethylaminoacetaldehyde diethyl acetal (30.01
9.) to pH 7.5 with concentrated HCl and then dropping epichlorohydrin
(22.8 9.) into the solution. The reaction mixture was held for 2 hrs.
while maintaining the pH between 7.5-8.5 by the addition of concentrat-
ed HCl or 50~ NaOH. The temperature was maintained at 30-35C. Impuri-
ties and excess reagent were removed from the reaction mixture by extrac-
tion with ethyl acetate (4 times with 65 ml. each time). The product was
~237~Z~L
- 20 -
isolated as an aqueous solution which ~as pH adjusted to 7Ø
Rea~ent H - 1,2-Epoxy-3,3-dimethyoxypropane, which has the formula
/ O\ /OCH3
CH2 - CH-CH , was prepared using the procedure of D. T. Weisblat
~ CH3
except that trimethyl orthoformate was used in place of triethyl ortho-
formate.
Reagent I - 1,2-Epoxyethyl-1,3-dioxalane, which has the farmula
O O--CH2
CH2 - CH-C ~ ¦ , can be prepared by a modification of the procedure
\Q--CH2
of D.T. Weisblat et al. The ethylene acetal of acrolein is used instead
of the diethyl acetal.
Reagent J - 3-(Chloromethyl)-N-(2,2-dimethoxyethyl)-N-methyl benzamide,
which has the formula
O OCH3
~ I - N - CH2 - CH , was prepared according to the
Cl ~2 lH3 \ OCH3
procedure used to make Reagent A except that 3-(chloromethyl) benzoyl
chloride (48.6 g.) was used instead of chloroacetyl chloride. The
product was isolated as a pale yellow oil after removal of the solvent.
It contained 4.8~ N (theoretical 5.15~.
Starch Reactions
The starch reactions with Reagents D to G and J were carried out
as in Example I, Part A, No. 1 using 30 9. Na2S04 in the slurry of
starch (100 9.) and a solution of 3.4 9. NaOH and S 9. Na2S04 in 70
9. water to adjust the pH. The reagent amounts, starch base, and
nitrogen content are shown below.
~L%3~ 4
- 21 -
~ Cationic N ~ Acetal N
Starch Basein B _ e Acetal Rea~t in Cationic Acetal
Waxy corn 0.270 15X n 0.240
Waxy corn 0.270 lZ~ E 0.360
Waxy corn 0.270 12~ F None*
Corn None 15~ G 0.380
Corn None 10~ J 0.279
*No nitrogen in acetal reagent
~
This example describes the preparation of acetal starch derivatives
other than cationic derivatives.
A. Potato, waxy maize, and tapioca starch were reacted with
Reagent A of Example I using the following procedure: 100 9. of starch
were slurried in 150 ml. water containing 30 g Na2S04. A solution of
3.4 9. NaOH, 5 9. Na2S04 and 70 9. water was added slowly to the
slurry, followed by 12 9. of Reagent A. The samples were reacted 45C,
16 hrs. and worked up using the method in example 1. Acetal nitrogen
was 0.40~, 0.46X and 0.41~, respectively.
B. High amylose corn starch (70~ amylose) was reacted with 20~ of
Reagent A using a procedure similar to that described in Examp1e 1 -
Par~ C except that the starch was not treated with DEC after reaction
with the acetal reagent. The product contained 0.99~ acetal nitrogen.
C. A waxy maize 85 fluidity starch was reacted wi~h 15% of Reagent
A (see Example 1) using the procedure of Part B above. The product
contained 0.75~ acetal nitrogen.
D. A waxy maize starch cross-linked with phosphorus oxychloride
and containing hydroxypropyl groups via reaction with propylene oxide
was reacted with Reagent A using the procedure described above in A.
~37: LZ9~
- 22 -
EXAMPLE IV
This example describes the preparation of guar gum acetals and a
gum arabic acetal.
Part A
A cationic guar gum was prepared by slurrying 60 parts of yuar gum
in 360 parts of 50~ aqueous isopropanol, heating the slurry to 40C, and
bubbling nitrogen gas into the slurry for 1 hr. A total of 7.2 parts of
50~ aqueous sodium hydroxide was added, the slurry was stirred for about
10 min.J and 4.8 parts of 50~ aqueous DEC were added. The slurry was
stirred for 4 hr. at 40C. The pH was lowered to 8.2 with dilute acetic
acid, and the derivative was recovered by filtration, washed with
aqueous isopropanol followed by 100~ isopropanol, and air-dried. It
contained 0.93~ N.
The resulting derivative may then be reslurried as above in aqueous
isopropanol and further treated with 3 parts potassium iodide, 2.4 parts
sodium hydroxide, and 1.2 parts of Reagent A of Example I. The reaction
should be carried out for about 16 hr. at 45C. The derivative may be
recovered and purified as above and should be useful in imparting wet
and dry strength to paper.
Part B
A total of 100 9. of guar gum was slurried in 600 ml. of a mixture
of 1:1 water and isopropanol. The mixture was heated to 45C, and 12.5
9. of 40~ sodium hydroxide were added. The mixture reacted for about
16 hours (overnight) with stirring. It was neutralized with acetic
acid to p~ 8.5, filtered, and washed with 1500 ml. of the isopropanol-
water mixture. The initial nitrogen on the guar was 0.677~; after the
above alkali-solvent treatment it was reduced to 0.25~.
The treated guar ~30 9.) was slurried in 100 ml. of the isopro-
~237~2~
- 23 -
panol-water mixture followed by 24.7 9. of 20~ sodium hydroxide. The
temperature WdS raised to 45C and 51 9. of Reagent A (see Example I)
were added. The reaction was allowed to run 4 hours, followed by
neutralization with acetic acid to pH 8.5, filtration, and washing with
1500 ml. of the isopropanol-water mixture. The g N on the final gum
acetal was 0.54~.
Part C
Gum arabic (25 9.) was added to 50 ml. of water which contained
0.62 9. of sodium hydroxide (pH 11.3). Then 2.5 9. of Reagent A of
Example I was added (10~ based on the wt. of the gum). The slurry
was reacted for 6 hours at 45C, the pH was adjusted to 7.5 with 10~
hydrochloric acid, and the soluble gum arabic derivative was recovered
- by alcohol (i.e., ethanol) precipitation. The N content was 0.535%
compared with 0.344~ for the underivatized base.
EXAMPLE V
This example describes the preparation of cellulose acetals. They
were prepared using the general procedure of U.S. Pat. No. 4,129,722
(cited previously).
A total of 20 9. SPAN-80 (a surfactant available from Hercules) was
dissolved in 200 9. Isopar E (petroleum solvent composed mostly of ~8
isoparafins, b. p. of 116-142C) in a 500 ml. flask equipped with a
thermometer, mechanical agitator, condenser and suitable size dropping
funnels. Cationic hydroxyethylcellulose (50 9.) grafted with dimethyl-
diallylammonium chloride (DMDAAC) was added to the solvent-surfactant
blend. Then 15 9~ of Reagent A of Example I was dissolved in 10 ml.
water and added to the reaction mixture over a 30 min. period. This
was followed by addition of 8 ml. of 10 N NaOH. The temperature was
* Trade Mark
',
~:3~ 2~
- 2, -
raised to 50C and held 3 hrs., followed by cooling to room temperature
and neutralization to pH 8.0 with HCl. The cellulose derivative was
filtered, washed with Isopar E and dried. Cationic N was 0.81~. Total
N after dialysis was 1.43%. Acetal N was therefore 0.62b.
Using an identical procedure methyl cellulose (Methocel from Dow
*
Chemical Co.) and cellulose (C-8002 alpha-cellulose from Sigma Co.)
were reacted with 30~ and 40~, respectively, of Reagent A. Acetal N on
the methyl cellulose was 0.54~ before and after dialysis. Acetal N on
the alpha-cellulose was 0.3~ after exhaustive washing with water.
Example VI
The following chart (A) shows a list of reactants which, when
O / OA
reacted, will give acetamide reagents of the type X-CH2-C-N-R2-CH
\ OA'
that can be reacted with polysaccharides such as starch, gum, and
cellulose using the procedures of Examples I, IY or V. The indicated
polysaccharide acetals should result from the reaction.
Example VII
The following chart (B) shows a list of reactants which, when
reacted and then convent;onally oxid;~ed, w;ll give an epoxide reagent
of the type
/ O / OA
HC - C CH
¦ l4 ~ OA~
R R
that can be reacted with polysaccharides such as starch, gum, or cellu'lose
using the procedure for Reagent F o~ Example II, when starch is the base
or a modification of that procedure when gum or cellulose are the bases~
* Trade ~lark
~37~Z~
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- 30 -
EXAMPLE VIII
This example describes the preparation of the aldehydes.
The starch acetals were converted to the corresponding aldehydes
by slurrying the acetal in water (e.g., 100 parts of water/1 part of
starch~ and adjusting the pH to 2.5-3.0 with a dilute solution of
hydrochloric acid. The starch ace~als were cooked in a boiling water
bath, prior to, after, or during the acidification to gelatinize the
starch. The total cooking time was about 20 mins. The slurry was
stirred during the acid addition and/or initial cooking. The cook was
cooled rapidly.
The cellulose acetals ~ere converted to the corresponding aldehydes
as above but it was not necessary to cook the cellulose derivatives.
The gum acetals can be conYerted to the corresponding aldehydes in a
like manner.
Example IX
This example describes the use of the cationic starch aldehydes and
cationic cellulose aldehyde as paper strength additives. The aldehydes
were added to the indicated paper furnish and handsheets were prepared
at pH 6.0, dried at 121C (250F.), cooled, cut into 1 in. strips, and
cured at 105C (221F.) for 5 min. The wet and dry tensile strengths are
reported as breaking length (B.L.). The addition level was 20 lb./ton.
The derivatives and paper test results are given in Table I. All
but No. 21 imparted initial wet strength and dry strength and were
superior to the prior art cationic dialdehyde starch in initial wet
strength. The cationic cellulose aldehyde provided the highest wet and
dry strength.
~;~3~24
- 31 -
Example X
This example shows the ef~ect of pH on the aldehyde generation.
It also as illustrates the preparation of starch acetals containing
mixed acetal substituent groups.
Part A - Preparation of The Mixed Acetal Reagents
Reagents K, L, and M were prepared by stirring 25 9. portions of
Reagent A of Example I with ~00 ml. of isopropanol (Reagent K), n-but-
anol (Reagent L), and tert-butanol (Reagent M) with 5 drops of concen-
trated hydrochloric acid for about 18 hours at room temperature. The
reaction mixtures were filtered and s~ripped on a rotary evaporator
at 40-50C, ~ollowed by vacuum pumping at 0.5 mm. Hg for 2 hours at
room temperature. NMR analysis showed that about 10-20~ of the dimeth-
oxy groups (i.e., -CH(OCH3)z) had been exchanged with the respective
solvents thus introducing isopropoxy groups (i.e.,-CH(OCH(CH3)2)2.
n-butoxy groups (i.e., -CH(OCH2CH2CH2CH3)2), (and tert-butoxy
groups -CH(OC(CH3)3)2)-
Part B - Preparation of The Starch D~rivatives
Cationic waxy maize acetal starch derivatives were prepared using
the above reagents and the procedure of Example I, Part A (3).
ZO Nitrogen analysis showed the following:
Starch Reagent ~ Cationic N ~ Acetal N
-
21 J 0.28 0.37
22 K 0. 28 0 . 33
23 L 0.28 0.34
2~ Control - 0.28
Part C - Evaluation of Wet Strength after Conversion To Aldehyde
at Various pH Values
One gram samples of the above starch acetals were slurried in
s E ~ 7~;Z9~
>I , Cl~ > O ~ 1 o o ~ o
V~ ~
-
a~ .
3 = E
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In . 3 s s s s s s s o a~ ~ 3 ~ 3 a~ s ~ r~
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33
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- 34 -
water to a total weight of 100 9. and the pH was adjusted to pH 2.5
or 5Ø The starches were cooked and evaluated in paper handsheets
as in Example YIII, Part A. The results are shown in Table II.
Table II
Cationic Initial
Starch Derivative No.Cook pH (lb./ton) Wet Strength
21 2.5 10 279
21 2.5 20 409
21 5.0 10 82
21 5.0 20 287
22 2.5 10 231
22 2.5 20 370
22 5.0 10 91
22 5.0 20 279
23 2.5 10 251
23 2.5 20 413
23 5.0 10 97
23 5.0 20 29
Control 5.0 20 89
(Cationic Starch Base)
The results show that the wet strength was much higher for starch
acetal derivatives cooked at pH 2.5 ra~her than pH 5Ø At the higher
addition level the wet strength increased even for the derivatives
cooked at the higher pH. This shows aldehydes were generated at the
higher pH.
Example XI
This example describes the temporary wet strength provided by the
cationic aldehydes. The aldehydes were eYaluated for both tissue/
toweling applications ~Part A) and board and bag applications (Part B).
P rt A
The deriYatives evaluated were the aldehydes prepared from a
cationic waxy corn starch acetal similar to the derivative of Example
~L~23~Z~
- 35 -
I - Part A-1 and the cationic cellulose acetal Example V, One starch
aldehyde was cooked as in Example VIII, but at a pH of 7, to provide a
liquid starch acetal. The acetal was then hydrolyzed to the aldehyde
by adausting the pH to 2.5 and then heating at 90-100C for 10-15 min.
It was then added to the paper furnish. The other starch aldehyde was
prepared by cooking the acetal at pH 2.5.
One cationic cellulose acetal was cooked as above at pH 7 to
provide a liquid cellulose acetal. It was then hydrolyzed to the
aldehyde by adjusting the pH to 2.5 and cooked as above. The other
cellulose acetal was cooked at pH 2.5. For comparison, the cationic
starch base, as well as cationic starch acetal which had been cooked
at a pH of 7 but not hydrolyzed, were evaluated (see Table II).
The addition 1evel was 20 lb./ton. The furnish was a 50:50
bleached sulfite:bleached Kraft. The paper sheets were prepared on the
Noble and Wood Sheet Mold. The paper weight was about 5 lb./1000 sq.
ft. The wet and dry strength results are shown in Table III.
The results show that all the cationic derivatives improved the dr
strength with the cationic starch aldehyde providing the most improve-
ment. Only the cationic aldehydes improved the wet strength. The
starch aldehyde prepared by simultaneously cooking and hydrolzing the
acetal was better than the precooked and subsequently hydrolyzed acetal
in dry strength, initial wet strength, and temporary wet strength.
TABLE III
Wet Strength ~ Relative
Dry (B.L. in m.) _ Wet Strength*
Strenqth 30 16 30 1~
Sample(B.L. in m.) Initial Min. Hr.Initial Min. Hr.
Blank1210 49 20 33 4.1 1.7 2.7
Cationic1640 83 43 N.D. S.1 2.6 2.1
Starch Base
~;~3~
- 36 -
TABLE III (cont'd)
Wet Strength % Relative
Dry (B.L. in m.) Wet Strength*
Stren~th 30 16 30 16
5 Sample (B.L. in m.) Initial Min. Hr. Initial Min. Hr
Cationic 1530 71 51 32 4.7 3.3 2.1
Starch Acetal
(comparative)
Cationic Starch 2140 382 26~ 122 17.9 12.1 5.7
Starch Aldehyde
(cooked at pH 2.5)
Cationic 1830 296 217 N.D. 16.2 11.9 N.D
Starch Aldehyde
(precooked
acetal)
Cationic 1550 335 25B N.D. 21.6 16.6 N.D
Cellulose
Aldehyde
Cationic -1610 350 277 N.D. 21.7 17.2 N.D.
Cellulose Aldehyde
(precooked acetal)
*Wet Strength/Dry Strength x 100.
N.D. - Not determined.
Part B
Some of the derivatiYes were also evaluated at 20 lb./ton in a
furnish of 100~ unbleached Kraft containing 3~ alum (i.e., aluminum
sulfate). The paper weight was about 42 lb./1000 sq. ft. The results
are shown in Table IV.
The results again show that all the cationic derivatives improved
the dry strength with the cellulose aldehydes being the best. Only the
aldehydes provided wet strength.
TABLE IV
Wet Strength ~ Relative
Dry(B.L. in m.r Wet Strength _
Strenath 30 16 ~ 30 16
Sample (B.L. in m.) Initial Min. Hr. Initial ~in. Hr.
Blank 5330 516 455 360 9.7 8.5 6.8
~;~3~
- 37 -
TABLE IV (cont'd)
Wet Stren~th g Relative
Dry (B.L. in m.) Wet Strength
Strenqth 30 16 30 16
5 Sample (B.L. in m.T Initial Min. Hr. Initial Min. Hr.
Cationic Starch 6050 533 471 N.D.8.8 7.8 N.D.
Starch Base
Cationic 5720 507 404 N.D.8.9 7.1 N.D.
10 Starch Acetal
Cationic 5711 1100 746 63719.3 13.1 11.2
Starch Aldehyde
(cooked at pH 2.5)
Cationic 6710 1660 1400 116024.7 20.9 17.3
15 Cellulose
Aldehyde
Cationic 6160 1640 1420 N.D.26.6 23.1 N.D.
Cellulose Aldehyde
(precooked acetal)
In summary, the present invention is seen to provide polysaccharide
aldehydes, which are generally useful for imparting strength to paper,
as well as the corresponding acetals us~ed in the preparation of the
aldehydes. It further provides a non-oxidative method for introducing
aldehyde groups into polysaccharides.
