Process for the production of polysaccharides

Polysaccharides corresponding to formula (I) ##STR1## in which S is a recurrent monosaccharide unit and PA1 B is a group of formula (Ia) attached to the monosaccharide unit S by an O atom ##STR2## are prepared by reaction of polysaccharides with an alkyl halide corresponding to formula (II) ##STR3##

This invention relates to a process for the production of cationic 
polysaccharides. 
Cationic polysaccharides are highly regarded as auxiliaries in paper 
manufacture, as starting products in the production of highly active 
filter materials which are used in the medical field and in the food 
industry and as additives for hygienic and cosmetic cleansing and care 
preparations. Basic polysaccarides are used inter alia as ion exchangers 
(U.S. Pat. No. 4,199,485) for the production of acid-soluble 
polysaccharides (U.S. Pat. No. 2,623,041) and as starting products for the 
synthesis of cationic polysaccharides (cf. U.S. Pat. No. 2,768,162). Their 
activity is generally greater, the more cationic groups they contain. 
Accordingly, it would be desirable to be able to substitute polysaccharides 
to a more or less high degree in accordance with the particular 
requirements. 
At a very early stage, cellulose sulfonates were reacted with amines in 
order to obtain N-containing celluloses. However, the degrees of 
substitution obtained were inadequate (for example 0.8% by weight N; cf. 
Angew. Chem. 39, 1509 to 36 (1926)) and the yields were poor (cf. J. Amer. 
Chem. Soc. 63, 1688 to 1691). 
After alkylation for the purpose of cationization, the cationized cellulose 
always has to be subjected to elaborate purification and reprecipitation 
process to separate it from the cationic polyethers (see Examples 1 to 3 
of U.S. Pat. No. 3,472,840). 
A process for the production of derivatives of CMC with quaternary ammonium 
is known from DE-PS 3 820 031. This known process is characterized in that 
a) an alkali metal salt of carboxymethyl cellulose is reacted with alkyl 
halides, particularly methyl chloride, to form the ester of carboxymethyl 
cellulose, 
b) amines corresponding to the following general formula 
##STR4## 
are added to the resulting carboxymethyl cellulose ester and c) finally, 
the aminoamido celluloses are quaternized with generally known alkylating 
agents. 
However, this known process is attended by some serious disadvantages, 
namely: 
1. Only those cellulose ethers which bear the carboxymethyl substituent 
(CMC, CMHEC) can be reacted by the process. 
2. The process is not economical. The three-stage synthesis is very 
time-consuming (see Example 1a: reaction time 21 h) and involves two 
purification steps. 
3. The degree of substitution of cationic groups cannot be established as 
required and is dependent upon the carboxymethyl cellulose used. Partial 
conversion of the carboxylate groups into quaternary ammonium groups is 
not possible, giving products containing both cationic and anionic groups 
which, as already known, leads to the formation of inner salts so that the 
products become insoluble in water (ionic crosslinking). 
4. The esterification of the carboxymethyl cellulose is not clear-cut. The 
methyl chloride decomposes under the reaction conditions mentioned with 
formation of methanol and hydrochloric acid. As a result of this 
decomposition, the process is accompanied by a whole number of secondary 
reactions involving the polymer, ultimately leading to water-insoluble 
products (see Comparison Example). 
5. As a result of the secondary reaction and the reaction parameters, the 
quaternary polymer has a much lower viscosity than the carboxymethyl 
cellulose used (see Example 3 of the patent). 
The problem addressed by the present invention was to provide cationic 
polysaccharides having a clear-cut, flexibly adjustable substitution and 
as high a degree of substitution as possible by clear-cut reactions using 
inexpensive reagents. 
The present invention relates to a process for the production of 
polysaccharides corresponding to formula (I) 
##STR5## 
by reaction of polysaccharides based on recurring units S with an alkyl 
halide corresponding to formula (II) 
##STR6## 
in which S is a monosaccharide unit and 
B is a group of formula (Ia) attached to the monosaccharide unit S by an O 
atom 
##STR7## 
n=an integer of 1 to 6, R.sup.1 =H, C.sub.1-4 alkyl, 
R.sup.2 =an alkylene radical which may interrupted by at least one O or N 
atom, 
R.sup.3,R.sup.4 =an alkyl, aralkyl or aryl radical, an alkyl radical which 
may be interrupted by at least one heteroatom, 
m=a number of 0.05 to 3.0, 
R.sup.5 =an alkyl radical optionally containing an olefinic double bond or 
an O atom or an aralkyl radical, 
Y=Cl, Br, 
X.sup..crclbar. =an anion or 
R.sup.3 and R.sup.4 together with the common N atom form a ring optionally 
containing another heteroatom. 
In one preferred embodiment, 
R.sup.1 =H, CH.sub.3 
R.sup.2 =--CH.sub.2 CH.sub.2 --, --(CH.sub.2).sub.3 --, --(CH.sub.2).sub.4 
--, --(CH.sub.2).sub.6 --, 
##STR8## 
--(CH.sub.2).sub.3 --O--(CH.sub.2).sub.2 --, --(CH.sub.2).sub.2 
--O--(CH.sub.2).sub.2 --, 
R.sup.3 =CH.sub.3, C.sub.2 H.sub.5, C.sub.3 H.sub.7, C.sub.4 H.sub.9, 
##STR9## 
R.sup.4 =CH.sub.3, CH.sub.2 CH.sub.2 OH, CH.sub.2 CH.sub.3, CH.sub.2 
--CH.sub.2 --O--CH.sub.3 or 
R.sup.3,R.sup.4 together with N atom form the group 
##STR10## 
R.sup.5 =CH.sub.3, CH.sub.2 CH.sub.3, CH.sub.2 --CH.dbd.CH.sub.2, 
##STR11## 
CH.sub.2 --CH.sub.2 OH X.sup..crclbar. =Cl.sup..crclbar., 
Br.sup..crclbar., SO.sub.4 Me.sup..crclbar., SO.sub.4 Et.sup..crclbar. 
toluene sulfonate, methane sulfonate, phosphate, sulfate. 
In a particularly preferred embodiment, 
R.sup.1 =H, 
R.sup.2 =--(CH.sub.2).sub.2 --, --(CH.sub.2).sub.3 --, 
R.sup.3,R.sup.4 =CH.sub.3, CH.sub.2 CH.sub.3 
R.sup.5 =CH.sub.3, CH.sub.2 --CH.dbd.CH.sub.2, 
##STR12## 
CH.sub.2 CH.sub.2 OH, CH.sub.2 CH.sub.3, X.sup..crclbar. 
=Cl.sup..crclbar., SO.sub.4 Me.sup..crclbar., SO.sub.4 Et.sup..crclbar.. 
The alkyl halides corresponding to formula II have never been described 
before. Accordingly, the present invention also relates to compounds 
corresponding to formula II. The substituents apart from Y have the same 
meaning as in the above definition of formula Ia. The same also applies to 
the preferred substituents. Y=Cl, Br. 
The compounds corresponding to formula II may readily be obtained by 
conventional methods known to the expert. 
Starting products for polysaccharides corresponding to formula (I) are, 
preferably, polyglycosans, such as cellulose, the various derivatives of 
cellulose, such as methyl cellulose, or mixed cellulose ethers, such as 
methyl hydroxyethyl celluloses, carboxymethyl celluloses, their various 
salts with sodium, potassium or ammonium ions; starch, dextrins, glycogen; 
polyfuctosans, such as inulin and graminin; polymannosans, 
polygalactosans, and also mixed polysaccharides, such as hemicelluloses, 
and polyxylosans or polyarabinosans. 
Preferred starting products are cellulose and derivatives thereof, starch 
and dextrins, particular preference being attributed to cellulose, methyl 
cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl 
cellulose, carboxymethyl cellulose and salts thereof and starch. 
The solubility of the ammonium polysaccharides according to the invention 
in alcohols or water depends both upon the starting material, upon the 
degree of substitution and upon the degree of quaternization and may be 
adjusted as required. 
The viscosity stages of the products may be adjusted through the choice of 
the polysaccharides which have a corresponding average degree of 
polymerization. Low-viscosity products can be produced by using 
polysaccharides oxidatively or hydrolytically degraded by standard 
methods. 
The polysaccharides are alkalized for etherification. The alkalization of 
the polysaccharides and their subsequent etherification may be carried out 
in the presence of organic solvents. Suitable organic solvents are lower 
alcohols which preferably contain 2 to 4 carbon atoms per molecule, ethers 
preferably containing 2 to 4 carbon atoms, hydrocarbons and dipolar 
aprotic solvents, such as for example dimethyl acetamide or dimethyl 
sulfoxide, or mixtures of these solvents. For alkalization, the 
polysaccharides are preferably sprayed with sodium hydroxide in a 
concentration of 18 to 100% by weight and preferably 40 to 50% by weight. 
The quantity of sodium hydroxide used depends upon the desired degree of 
quaternization. According to the invention, the etherification reagent 
(II) is preferably added either before the sodium hydroxide or after the 
alkalization phase. For etherification, the reaction mixture is heated to 
temperatures of 50.degree. to 100.degree. C. and preferably to 
temperatures of 70.degree. to 90.degree. C. and the temperature level 
established is maintained until the reaction is complete. The 
etherification times are between 1 and 15 h, depending on the temperatures 
and the solvent. 
The reaction product is worked up in known manner by separation and washing 
with aqueous organic solvents. 
The water-soluble cationic polysaccharides according to the invention are 
suitable as additives for hygienic and cosmetic cleansing and care 
preparations, as auxiliaries in paper manufacture and for the treatment of 
textile fibers to improve handle. 
In addition, the water-soluble cationic polysaccharides are used as 
aggregating agents. Aggregation in the context of the invention is 
intended to encompass flocculation, coagulation and precipitation. 
Flocculating agents are process auxiliaries for rationalizing solid/liquid 
separation processes. By using flocculating agents, it is possible 
significantly to increase the sedimentation rate in water of suspended 
solids which are frequently present in colloidal form. Effective 
flocculating agents achieve almost complete flocculation of the suspended 
particles so that the residual solids contents in the liquid phase are 
largely minimized. In addition, the use of flocculating agents increases 
the solids content of the solid phase so that the sedimented sludges can 
be dewatered by machine in a technically and economically favorable 
manner. 
Flocculating agents are divided into primary flocculating agents and 
flocculation aids. Primary flocculating agents are chemical compounds 
which form substantially water-insoluble precipitates. They include the 
Fe, Al and Ca salts widely used in practice. Their addition initially 
neutralizes the charge of the suspended particles which are generally 
stabilized by negative surface charges, so that the electrical double 
layer of the particles is destroyed and rapid coagulation occurs. As 
hydrolysis of the inorganic compounds progresses, water-saturated 
voluminous flocs containing water ingredients are formed and precipitate. 
The disadvantage of flocculation with inexpensive inorganic metal salts is 
that the flocculation process is dependent on temperature and confined to 
a narrow pH range, the flocs sediment at a relatively slow rate and large 
sludge volumes are formed. 
Flocculation aids are cationic, anionic or neutral water-soluble polymers 
of high molecular weight which do not have these disadvantages. By ion and 
dipole interactions between the polymers and the suspended particles, the 
colloidal particles initially undergo coagulation in this case, too. Given 
a sufficiently high molecular weight, the macromolecules are capable of 
combining several of the destabilized particles to form rapidly 
sedimenting, shear-stable macroflocs. Flocculation aids are widely used in 
water treatment and wastewater treatment in the petroleum, paper, coal and 
ore industries and in certain branches of the chemical industry. 
The cationic polysaccharides produced in accordance with the invention may 
advantageously be used in quantities of 0.01 to 0.5% by weight. Depending 
on their degree of cationization and their molecular weight, they may be 
"tailored" for each field of application. 
In numerous applications where liquid and semisolid products are produced 
and stored, microorganisms represent a problem because of their ability to 
proliferate and their metabolism. At the present time, no methods are 
available for removing mycotoxins once they have formed from food without 
destroying the food (H. K. Frank, Schriftenreihe des Bundes fur 
Lebensmittelrecht und Lebensmittelkunde, No. 76, 1974). The 
water-insoluble cationic polysaccharides produced in accordance with the 
invention are used in the production of highly active filter materials. 
For the reasons explained above, these highly active filter materials are 
of considerable interest in the pharmaceutical industry and in the 
beverage industry. 
The way in which filter layers work is based primarily on 
a mechanical sieve effect, 
a depth effect 
an adsorption effect. 
By virtue of the mechanical sieve effect, large particles of sediment are 
retained on the surface of the layer. They do not penetrate into the 
pores. Finer sediment particles penetrate more deeply into the layer, 
become caught up in the material network and gradually clog the pores 
(depth effect). By virtue essentially of the electrical charge ratios of 
the sediment particles to the raw materials, the sediment particles which 
have penetrated into the layer are adsorbed at the surfaces of the pores 
(adsorption effect). These effects are dependent on the material 
properties of the raw materials (kieselguhr, cellulose, cotton). The 
effectiveness of a filter layer is defined by the cleanness with which it 
clarifies and is determined by a combination of the sieve, depth and 
adsorption effects. 
In germ filtration, conventional filter layers show inadequate cleanness of 
clarification because of their inadequate adsorption capacity. 
In germ filtration tests, test filters in which the raw material cellulose 
was partly replaced by the cationic polysaccharides according to the 
invention showed enhanced activity against pyrogenic germs and endotoxins 
as fibrous filters or aluminium-oxide-filled filter layers.

EXAMPLES 
Example 1 
226 g (2.0 mol) chloroacetic acid chloride are rapidly added dropwise with 
stirring at 0.degree. to 5.degree. C. to a solution of 209 g (2.05 mol) 
N,N-dimethylamino-1,3-propylamine in 300 g isopropanol. 252 g (2.0 mol) 
dimethyl sulfate are added dropwise to this solution over a period of 30 
minutes at 0.degree. to 5.degree. C., followed by the dropwise addition 
over a period of 1 hour at 9.degree. to 10.degree. C. of 80 g sodium 
hydroxide in the form of a 50% aqueous solution. After slow heating to 
50.degree. C., the reaction mixture is kept at that temperature for 3 to 5 
hours. The salt precipitated is filtered under suction, washed with 
isopropanol and dried: 112 g, corresponding to 95% of the theoretical 
yield. 
Concentration of the combined filtrates by evaporation gives a light brown 
oil; 553 g, corresponding to 97% of the theoretical yield. 
The analytical data correspond to the structure: 
EQU Cl--CH.sub.2 --CO--NH(CH.sub.2).sub.3 --N.sup..sym. (CH.sub.3).sub.3 
SO.sub.4.sup..crclbar. CH.sub.3 (III) 
______________________________________ 
Elemental analysis: 
C N Cl S 
______________________________________ 
Calc. % 35.5 9.2 11.9 10.5 
Found % 35.0 9.1 11.3 10.5 
______________________________________ 
Molecular weight as determined by vapor pressure osmosis in DMF: 320 (calc. 
304). 
Example 2 
16.2 g (0.1 mol) finely ground cotton linters are suspended in 300 ml 
dioxane and alkalized for 1 h at room temperature with 18% NaOH. 30.5 g 
(0.1 mol) of the quaternizing reagent III are then added to the alkali 
cellulose. The temperature is slowly increased to 50.degree. C. and kept 
at that level for 120 minutes. After cooling, the reaction product is 
neutralized with acetic acid, purified with 70% methanol and dried. A 
water-insoluble cationized cellulose ether having an N-content of 2.5%, 
corresponding to a DS of 0.2, based on the cationized group, is obtained. 
The IR spectrum shows a strong amide band at 1,550 cm.sup.-1 and 1,670 
cm.sup.-1. 
Example 3 
27 g of a hydroxy ethyl cellulose (HEC) having a molar degree of 
substitution of 2.4 are suspended in 300 ml DMSO/toluene (1:1) and 
alkalized for 1 h at room temperature with 4.8 g NaOH (prills). 30.5 g 
(0.1 mol) of the quaternizing reagent III are then introduced into the 
reaction vessel. The temperature is slowly increased to 90.degree. C. and 
kept at that level for 8 h. After cooling, the reaction product is 
neutralized with nitric acid and purified with 80% acetone. A 
water-soluble, cationized HEC containing 4.6% nitrogen, corresponding to a 
DS of 0.78, is obtained. The chemicals yield, based on the etherifying 
agent, is 78%. The IR spectrum again shows the strong amide bands. 
Example 4 
18.9 g of a methyl hydroxyethyl cellulose (MHEC) having an average degree 
of substitution, based on methyl, of 1.48 and a molar degree of 
substitution, based on hydroxyethyl, of 0.13 are suspended in 300 ml 
dimethyl acetamide/cyclohexane (1:1) and alkalized for 1 h at room 
temperature with 4.8 g NaOH (prills). 30.5 g (0.1 mol) of quaternizing 
reagent III are then introduced into the reaction vessel. The temperature 
is increased slowly to 70.degree. C. and kept at that level for 8 h. After 
cooling, the reaction product is neutralized with nitric acid and purified 
with 80% acetone. A water-soluble, cationized MHEC containing 3.4% 
nitrogen, corresponding to a DS of 0.35, based on the quaternized group, 
is obtained. The IR spectrum again shows the strong amide bands. 
Example 5 
23.3 g (0.1 mol) of a carboxymethyl cellulose (CMC) having an average 
degree of substitution, based on the carboxymethyl group, of 0.9 are 
suspended in 300 ml dimethyl sulfoxide and the suspension is alkalized for 
1 h at room temperature with 0.1 mol 50% NaOH. 30.5 g (0.1 mol) of 
quaternizing reagent III are then added. The temperature is slowly 
increased to 90.degree. C. and kept at that level for 10 h. After cooling, 
the reaction product is neutralized with acetic acid, washed with 70% 
methanol and dried. A cationized CMC containing 4.1% nitrogen, 
corresponding to a DS of 0.55, based on the cationic group, is obtained. 
The chemicals yield is thus 55%. In addition to the carboxylate band at 
1,610 cm.sup.-1, the IR spectrum shows the amide bands at 1,670 cm.sup.-1 
and 1,550 cm.sup.-1. 
Comparison Example (Corresponding to DE-PS 3 820 031) 
a) Esterification of the carboxymethyl cellulose 
As in Example 1a), 228.4 g (1 mol) sodium carboxymethyl cellulose having a 
degree of modification of 0.84, viscosity of a 2% aqueous solution 546 
mPa.s (rotational viscosimeter), pH value 7.5, and 403.6 g methyl chloride 
are heated for 9 h at 80.degree. C. in a 2 liter laboratory autoclave. A 
pressure of approximately 25 bar is established. The methyl chloride is 
then evaporated in vacuo at 50.degree. C. The IR spectrum of reaction 
product shows that there is no longer any carboxylate band at 1,610 
cm.sup.-1. Instead, a new band has appeared at 1,750 cm.sup.-1. 
The product is insoluble in water, the supernatant solution having a pH 
value of 3.4. 
b) Aminolysis of the CMC ester 
As in Example 2b), 100 g of the reaction product obtained in accordance 
with a), 80 g dimethyl aminopropyl amine and 330 g methanol are heated 
with stirring for 3 h to 140.degree. C. in a 2 liter laboratory autoclave, 
filtered under suction after cooling and washed with aqueous methanol 
until neutral. 
In addition to the expected amide bands at 1.550 cm.sup.-1 and 1,670 
cm.sup.-1, the IR spectrum of the reaction product shows an equally large 
carboxylate band at 1,610 cm.sup.-1. The carbonyl band at 1,750 cm.sup.-1 
has disappeared. 
A 2% aqueous solution of the aminolysis product has a viscosity, as 
measured with a rotational viscosimeter, of 16 mPa.s. 
c) Quaternization of the aminolysis product 
As in Example 3a), 30 g of the reaction product from b), 50 g methyl 
chloride and 480 ml methanol are kept at room temperature for 15 h in a 2 
liter laboratory autoclave. After cooling, the excess methyl chloride is 
removed by evaporation, the methanol is filtered off under suction and 
dried. 
The IR spectrum is identical with the product of step b; no Cl.sup.- can 
be detected. 
Under these reaction conditions, no quaternization takes place. 
If the reaction is carried out over a period of 4 hours at 80.degree. C., a 
water-insoluble product is obtained. The supernatant solution has a pH 
value of 2.5. 
The IR spectrum shows the following bands: 
1,750 cm.sup.-1 (main band, --COOH, --OCOOMe) 
1,670 cm.sup.-1, 1,550 cm.sup.-1 (amide bands) 
1,610 cm.sup.-1 (--COO.sup..crclbar. Na.sup..sym.)