METHODS OF PREPARING HALOHYDROXYPROPYLTRIALKYLAMMONIUM HALIDES

FIELD

The present invention relates to methods of preparing halohydroxypropyl- trialkylammonium halides.

BACKGROUND

Halohydroxypropyltrialkylammonium halides are useful intermediates for modification of natural and synthetic polymers, particularly in production of cationic polysaccharides. They are generally prepared by reaction of certain trialkylamines, or their salts, with epihalohydrins. In the past, those skilled in the art used only relatively pure epihalohydrin feedstreams because of the effects of impurities on final halohydroxypropyltrialkylammonium halides. Thus, "prime" epihalohydrins command a generous premium. In contrast, offstream epihalohydrins, also known as "dirty" epihalohydrins or propylene oxide epihalohydrins, which contain significant levels of a variety of impurities, are relatively inexpensive. For example, propylene oxide epihalohydrin is a waste product from propylene oxide manufacture.

In the past, offstream epihalohydrin feeds have been considered unusable because the aromatic impurities would be expected to persist in the final product, resulting in unacceptable environmental and reporting problems.

Thus, what is needed are methods of preparing halohydroxypropyltrialkylammonium halides that can be employed using epihalohydrin feedstreams containing significant levels of a variety of impurities.

SUMMARY

In one embodiment, the present invention provides processes for preparing a halohydroxypropyltrialkylammonium salt, comprising reacting, in an aqueous reaction mixture, a trialkylamine hydrohalide salt and its corresponding free amine with an epihalohydrin feed, wherein the epihalohydrin feed includes greater than 1 ppm of an aromatic impurity, allowing the halohydroxypropyltrialkylammonium salt product to form having the detectable amount of aromatic impurity, extracting the halohydroxypropyl- trialkylammonium salt product with a halogenated organic solvent, and obtaining an halohydroxypropyl-trialkylammonium salt, wherein the detectable amount of the aromatic

impurity is reduced to less than 1 ppm of an aromatic impurity.

DETAILED DESCRIPTION

In one embodiment, the present invention provides processes for preparing a halohydroxypropyltrialkylammonium salt, comprising reacting, in an aqueous reaction mixture, a trialkylamine hydrohalide salt and its corresponding free amine with an epihalohydrin feed, wherein the epihalohydrin feed includes greater than 1 ppm of an aromatic impurity, allowing the halohydroxypropyltrialkylammonium salt product to form having the detectable amount of aromatic impurity, extracting the halohydroxypropyl- trialkylammonium salt product with a halogenated organic solvent, and obtaining an halohydroxypropyl-trialkylammonium salt, wherein the detectable amount of the aromatic impurity is reduced to less than 1 ppm of an aromatic impurity.

The invention provides a process for preparing halohydroxypropyl-trialkylammonium halides from epihalohydrin feeds that include detectable levels of aromatic impurities. Such epihalohydrin feeds have heretofore been avoided because the aromatic impurities would be expected to persist in the final product, resulting in unacceptable environmental and reporting problems in particular. It has now been found that such feeds may be employed with the inventive process, even where relatively high, e.g., greater than 1 percent by weight, levels of aromatics are present in the epihalohydrin feed.

In general the epihalohydrin feed as employed herein is defined as including at least about 1 part per million (ppm) of at least one aromatic compound. This amount of total aromatic compound is defined herein as "detectable," and "not detectable" is concomitantly defined as a total aromatic compound content of less than about 1 ppm. In some embodiments the amount may be from about 1 ppm to about 2 percent by weight, and in other embodiments the lower limit may be from about 50 ppm, while the upper limit may be to about 1 percent by weight.

The constitution of the aromatic impurity may vary. For example, ethyl benzene, benzene, monohalobenzene, e.g., monochlorobenzene, or a combination thereof may be present in the epihalohydrin feed. In other embodiments, the aromatic impurity may be, for example, dihalobenzene, trihalobenzene, tetrahalobenzene, pentahalobenzene, hexahalobenzene, alkylbenzene wherein the alkyl is from Cl to C 12 and includes saturated and/or unsaturated bonds, dialkylbenzene wherein the alkyl is from Cl to C 12 and includes saturated and/or unsaturated bonds, combinations thereof, and the like. Additional impurities may also be present, such as, for example, l,3-dichloro-2-propanol, 2,3-dichloro-l-propanol,

and combinations thereof. Other impurities may include 1 ,2-dichloropropane, 2,3-dichloro- 1-propene, 2-bromo-l-chloropropane, l-bromo-2-chloropropane, 2-methyl-2-pentenal, 1,2,2- trichloropropane, 1,3-dichloropropane, l-chloro-2-propanol, 2-chloro-l-propanol, trichloropropane, tichloroisopropyl ether isomers, combinations thereof, and the like.

In one embodiment, a crude epihalohydrin waste stream resulting from propylene oxide processing may be employed as the epihalohydrin feed. The constitution of one such waste stream may include, in one embodiment, 97.56% by weight epichlorohydrin; 0.78% by weight ethyl benzene; 0.06% by weight monochlorobenzene; 10 ppm benzene; 1.56% by weight l,3-dichloro-2-propanol; and 0.04% by weight 2,3-dichloro-l-propanol. Other waste streams, useful in certain embodiments as the epihalohydrin feed for the invention, may include differing levels and types of aromatic impurities.

The process of the invention is suitable for any trialkylamine and the corresponding hydrohalide, but is particularly useful for trialkylamines and their hydrohalides, such as trimethylamine, tri-n-propylamine, dimethyl stearylamine, dimethyl dodecylamine, triethylamine, tri-n-butylamine, tri-n-hexylamine, dimethylmonoethylamine, dimethylmono- n-butylamine, dimethylcyclohexylamine, dimethyl-monoisopropylamine, methylethyl-n- propylamine, methylethyl-n-butyl-amine, methyl dialkyl amines, and other tertiary amines having linear, branched or cyclic hydrocarbon groups, each independently containing from 1 to 20 carbon atoms, and their hydrohalides, preferably dimethylstearylamine, dimethyl dodecylamine, or trimethylamine, and their hydrohalides; and more preferably trimethylamine and its hydrohalides, particularly its hydrochloride.

The trialkylamines and their salts are commercially available or are formed in reactions within the skill in the art such as the reaction of the corresponding trialkylamine with an acid, preferably a hydrohalic acid, to form the amine hydrohalide, more preferably with hydrochloric acid. While the hydrohalide is preferred, any acid that sufficiently neutralizes the base may be useful in the practice of the invention; therefore, any acid salt is suitable in the present invention, preferably salts which do not form a buffer, more preferably inorganic acid salts, and most preferably monovalent inorganic salts such as nitrates or divalent inorganic salts such as sulfates. Organic salts, such as the acetate or formate, may also be used.

The epihalohydrin feed may include any epihalohydrin, but epichlorohydrin is the preferred epihalohydrin because it is readily available and chloride ion is considered to be more environmentally acceptable than other halides.

In a preferred embodiment, trialkylamine is admixed with the corresponding trialkylammonium salt, preferably hydrohalide, preferably in aqueous solution, and more preferably under conditions such that both the amine and the hydrohalide are in aqueous solution. While any concentration of the amine combined with trialkylamine salt may be suitable for use in the practice of the invention, for convenience and to achieve a desirable rate of reaction with the epihalohydrin while avoiding excessive waste water handling, the initial concentrations are preferably sufficiently high to achieve a rapid rate of reaction, conveniently at least about 10 weight percent, but insufficient to precipitate the salt or product, thus less than about 60 weight percent, more preferably from about 40 to about 60 weight percent, based on the combined amine and hydrohalide weight in aqueous admixture prior to the epihalohydrin feed addition. Alternatively, an amine is partially neutralized with the acid, preferably hydrohalic acid, or an amine salt is partially neutralized with a base. Partial neutralization optionally takes place in situ, e.g., by simultaneous or sequential addition of amine and acid. Any means within the skill in the art for forming admixtures of the free amine and its salt in the preferred ratios is suitable for use in the practice of the invention.

The amine and hydrohalide are conveniently admixed just prior to reaction with the epihalohydrin feed. Alternatively, an admixture is prepared in advance or obtained commercially. If the admixture is stored, it is advantageous to store the mixture in a closed container to prevent free amine from escaping when the amine is volatile.

Sufficient amine is admixed with or otherwise present with the amine salt, preferably an amine hydrohalide, to reach an initial pH (before addition of epihalohydrin feed) of from about 8.1 to about 9.2, preferably from 8.1 to about 9.0, more preferably from about 8.1 to about 8.9 at 1O ⁰ C. These pHs correspond to an amine hydrohalide to total free amine plus amine hydrohalide percentage of from about 99.0 to about 90.0, preferably from 99.0 to about 93.0, more preferably from about 99.0 to about 95.0 as calculated based on a chart of pKa's of trimethylamine and corresponding temperatures from Dissociation Constants of Organic Bases in Aqueous Solution by D.D. Perrin (Butterworths, London, 1965, p. 15), reproduced in Table 1. This percentage corresponds to the mole percentage of hydrohalic acid used to neutralize amine.

TABLE 1

As Table 1 shows, measured pH varies with temperature. For instance, a pH of 8.5 measured at 3O ⁰ C corresponds to 94 mole percent trimethylamine hydrochloride, but the same pH measured at 2O ⁰ C corresponds to 96.4 mole percent trimethylamine hydrochloride. The process may, therefore, be characterized in terms of mole percent of trimethylamine hydrohalide (TMA-HCl), based on combined free amine and trimethylamine hydrohalide, and the pH may be stated for convenience as that measured at 1O ⁰ C. For convenience, the following chart gives corresponding mole percentage TMA, pH calculated at 15 ⁰ C, and molar concentration:

TABLE 2

The trialkylamine/trialkylammonium hydrohalide admixture is reacted with the epihalohydrin feed. At least about a stoichiometric amount of epihalohydrin feed is reacted with the admixture so that the amine is reacted, substantially completely, with the epihalohydrin to form the desired product. Preferably, the epihalohydrin to amine plus hydrohalide ratio is from about 1 to about 12, more preferably from about 1.05 to about 1.20, and most preferably from about 1.10 to about 1.20. Amounts in excess of that reacted with the other reagents usually form dihalopropanol under reaction conditions.

In one embodiment, the free amine is present in an amount corresponding to from about 1 to about 10 mole percent, based on total moles of free amine and trialkylamine hydrohalide salt.

Advantageously, the epihalohydrin feed is added to the aqueous amine, amine hydrohalide admixture (hereinafter, the reaction mixture). Alternatively, the epihalohydrin feed is added simultaneously with the aqueous admixture to form the desired product. When the epihalohydrin feed is added, the temperature is advantageously sufficient to result in a desired reaction rate, conveniently to have the reaction proceed with minimal build-up of reactants and a relatively slow exotherm, but slow enough to avoid appreciable diquaternary compound and dihaloalcohol by-product formation. The term "appreciable" is defined as equal to or greater than 1 weight percent diquaternary compound based upon the weight of the desired product, in the case of trimethylamine reacted with epichlorohydrin, 3-chloro-2- hydroxypropyl-trimethylammonium chloride, plus diquaternary compound and less than 10 weight percent dihaloalcohol by-product based upon the weight of the desired product plus dihaloalcohol. The temperature of addition is preferably from about O ⁰ C to about 15 ⁰ C, more preferably from about 5 ⁰ C to about 15 ⁰ C, and most preferably from about 1O ⁰ C to about 15 ⁰ C.

The pH of the reaction mixture will be increased by addition of the epihalohydrin feed and its reaction with the amine/hydrohalide admixture. Observed pH is preferably from about 7.5 to about 11 after all epihalohydrin feed is added.

The epihalohydrin feed is preferably added to the admixture over a period of time rather than all at once to avoid an exotherm which is difficult to control and leads to high levels of aqueous and organic by-products. Conveniently, it is preferably added over a period of from about 1 to about 4 hours.

Alternatively, the process is continuous and comprises adding the epihalohydrin feed and amine/amine salt admixture in stoichiometric amounts or the preferred ratios in a continuous fashion. The continuous process advantageously has a shorter residence time in a

mixer than in a reactor. A batch process advantageously has the epihalohydrin feed added slowly to the amine salt admixture with continual mixing during and after the addition.

In general, when using an amine/amine hydrohalide reactant admixture, while a relatively low temperature is advantageous for addition or admixing of epihalohydrin feed with the amine admixture, a relatively higher temperature is advantageous for at least part of the reaction time. Thus, it is advantageous to have a first time period which preferably includes addition of at least a majority of the epihalohydrin feed at a temperature at least about 10 degrees Celsius below that of a second period during which the reaction is allowed to proceed further. The second period at a higher temperature advantageously results in a lower residual, unreacted amine in the reaction mixture after reaction is ended. Variations within these two periods are within practice of the invention. For instance, while it is preferable to add the epihalohydrin feed during the first period while the temperature is lower, optionally at least a portion, preferably less than half, most preferably little to none of the epihalohydrin feed is added during the second period at the higher temperature.

In a preferred embodiment, the first period extends beyond the time required for addition of the epihalohydrin feed to allow reaction to include that which is achieved during addition as well as continuing reaction. The time after addition of epihalohydrin feed is complete during which additional reaction takes place is referred to herein as "digest time." The first period preferably includes, in addition to an addition time, a digest time, which digest time is preferably sufficient to allow a predetermined amount, preferably at least about 85 percent of the amine and amine salt, to react with the epihalohydrin feed. In preferred embodiments, this time is at least about 0.5 hour, and more preferably at least about 1 hour. Preferably the digest period ends when sufficient halodihydroxytrialkylammonium halide product has formed such that the rate of formation of dihaloalcohol becomes at least about equal to the rate of formation of product.

While the first period, whether or not it includes a digest time, is preferably at the temperatures stated for addition of the epihalohydrin feed, the second period is desirably at a second, higher temperature, which is sufficiently higher to result in less residual amine after reaction than would be observed if the same reaction (same reactants, total time, addition time, and reaction conditions), were to take place entirely at the temperature used during the first period. This second temperature is preferably at least about 10 ⁰ C above that used for the first period, and is preferably less than 8O ⁰ C, but at least 15 ⁰ C, more preferably less than 75 ⁰ C but at least 3O ⁰ C, most preferably less than 7O ⁰ C but at least 4O ⁰ C. The second period preferably is a digest time, which digest time is preferably sufficient to result in less residual

amine, more preferably is at least about 0.5 hour, most preferably at least about 1 hour. Preferably, this digest time ends when at least about 90 weight percent of the amine, more preferably at least about 99 weight percent of the amine has reacted, most preferably when less than about 50 ppm of amine remains. Preferably the second period ranges from about 0.5 to about 4 hours, most preferably the digest is from about 1 to about 3 hours.

Those skilled in the art will recognize that the present invention includes variations such as gradual increase in temperature from one period to another, for instance, in response to the reaction exotherm. Even when there is gradual increase, there is a period within a first temperature range and a second period within a second temperature range. In such cases, the preferred period of time at any individual temperature will be shorter than is preferred when there are two relatively constant temperatures. The term "relatively constant" is used to recognize that in practice there is often variation within a temperature held "constant", for instance, a thermostat may allow a few degrees above and below a set temperature. Such a temperature held within a range is more constant than a continually rising or falling temperature. In reactions where there is changing temperature, the temperature during a period is taken as the average temperature during the period. The invention also includes use of more than two or three temperatures, for instance, several short digests at different temperatures.

After reaction of the epihalohydrin feed and trialkylamine and its salt has reached a predetermined stage of completion, preferably is essentially complete, that is, at least about 90 percent by weight, more preferably at least about 99 percent, by weight of the limiting reactant (preferably the amine plus trialkylamine salt), is reacted, the reaction is ended by removal or reduction of the residual epihalohydrin and, where still present, of by-products. Some by-products are unavoidably produced and are optionally reacted suitably before, after, or when possible, during the process of the invention. An epoxy by-product, 2,3- epoxypropyltrimethylammonium chloride, which may form when the epichlorohydrin feed is reacted with the trimethylamine, is optionally converted to 3-chloro-2- hydroxypropyltrimethylammonium chloride product by hydrochlorination. Hydrochlorination is within the skill in the art, for instance, where an equimolar amount of hydrochloric acid is added and reacted at 2O ⁰ C to 100 ⁰ C.

After the epichlorohydrin feed, amine/amine salt reaction is completed, the 1,3- dichloro-2-propanol, that may result in the case of epichlorohydrin reacting with trimethylamine, and residual epichlorohydrin are advantageously separated from the product. Removal is suitably by any method within the skill in the art, but preferably by distillation,

preferably azeotropic distillation, most preferably vacuum azeotropic distillation. These means of distillation are preferred because they provide economical separation and do not introduce foreign solvent material. Additionally, vacuum conditions minimize temperatures and resultant thermal degradation of product.

The azeotropic distillation preferably takes place in the presence of sufficient water to provide the azeotropic composition of water with the dihalopropanol, which is 75 weight percent water. The water phase can be allowed to separate and reflux. Initially, there is advantageously enough water to allow loss due to solubility of water removed with the dihalopropanol (including dissolved water) and enough to provide water for the azeotrope. Because of the heterogeneous nature of the azeotrope which allows the water to reflux back, very little additional water will be needed.

Vacuum distillation can be accomplished at any pressure below atmospheric, conveniently from about 50 to about 100 mm Hg (about 7 to about 13 kPa) corresponding to temperatures within the column varying from 3O ⁰ C to 9O ⁰ C.

Preferably the product is produced "substantially without" diquaternary or diol byproducts. By "substantially without", it is meant that such by-products are each present in amounts less than 1 weight percent relative to the product halohydroxypropylammonium salt. Preferably there is less than 2,000 ppm diol by-product in an aqueous solution of 65 weight percent product. More preferably, there is less than 1 percent diquaternary by-product in an aqueous solution of 65 weight percent product. It is believed that intermediates which would otherwise lead to diquaternary by-products are converted to halohydroxypropyl- trialkylammonium halide, thus improving efficiency of use of raw materials.

The present invention is particularly suited for reducing or removing aromatic impurities that persist, being present in the epihalohydrin feed and remaining unreacted throughout the process with the result that the impurities appear in the halohydroxypropyltrialkylammonium halide product. Thus, they are not technically byproducts. These aromatic impurities are removed, following completion of the trialkylamine/trialkylamine salt and epihalohydrin feed reaction as described hereinabove. This removal or reduction, from detectable to non-detectable levels, may be accomplished by means of an azeotropic distillation as described hereinabove, thus serving the goal of reduction of dihaloalcohol by-products as well as aromatic impurities. In another embodiment, a simple solvent extraction, using preferably multiple extractions with a halogenated organic solvent, such as methylene chloride, perchloroethylene, chloroform, carbon tetrachloride, combinations thereof, and the like may be employed. In another

embodiment, a vacuum distillation may be carried out, and in yet another embodiment, a combination of the above-described methods may be employed. For example, a series of solvent extractions, followed by vacuum distillation to remove the selected solvent, may be particularly effective in ensuring that detectable levels of aromatic impurities do not remain in the final halohydroxypropyltrialkylammonium halide product.

Measuring such concentrations of diquaternary and diol by-products is within the skill in the art, for instance, by liquid chromatography of an aqueous solution of halohydroxypropyltrialkylammonium halide product, which product is most preferably in a concentration of about 65 weight percent in water. Such liquid, preferably paired-ion chromatography is suitably conducted on a system such as that available from Agilent Technologies. Such a system has a pump, sample injection system, radial column compression system, and a refractive index detector. Suitable columns include, for instance, C- 18 reverse-phase columns. A paired-ion chromatography reagent such as that prepared from 3.98 g (grams) of 1 -octane sulfonic acid, 116 g sodium perchlorate, 132 g methanol and 1750 g high purity water, filtered through, e.g., 0.45 micron paper and degassed 15 minutes under vacuum is suitably used as chromatographic solvent, and a solution such as 5 percent methanol in water (similarly filtered and degassed) is suitably used to flush the column prior to periods of inactivity. These solution concentrations are optionally optimized for some liquid chromatography columns. Determining chromatograph parameters is within the skill in the art, but for the suggested system, suitable combinations include a pump flow rate of 1.5 mL/min. and using a detector having an internal temperature of 4O ⁰ C. The chromatography system is preferably used with data acquisition software, such as ChemStationTM for LC, commercially available from Agilent Technologies. High purity standards may be prepared by methods within the skill in the art and used to calibrate the system. The system is preferably purged with the paired-ion chromatography reagent at least until a flat baseline is obtained. Then a weighed sample may be introduced into the system, e.g., using a syringe and sample injection valve. Peak areas are obtained using the system and an integrator and compared with the calibration standard to ascertain concentration. This procedure is within the skill in the art.

Measuring the aromatic impurity can be achieved by analysis using an HP-5890 Series II Plus (GC) equipped with a flame ionization detector (FID), ChemStationTM data acquisition system and a capillary column. The column can be a HP-WCOT, 50m x 0.2mm x 0.33mm FFAP film thickness. The injector and detector temperatures should be 18O ⁰ C and 22O ⁰ C, respectively. The column oven is temperature programmed from 60° C for 4.00

minutes to 200° C at a rate of 10° C/minute with a final hold time of 6.00 minutes. A programmable autosampler is used to inject a 1.0 μL sample into a split mode injector. Helium is used as the carrier and make-up gas to the detector. All of the samples analyzed with this method should be with methylene chloride as the media. The GC is pre-calibrated via any conventional external standard method.

The level of dihaloalcohol, in the case of epichlorohydrin feed reacted with trimethylamine hydrochloride, l,3-dichloro-2-propanol, made is advantageously low, preferably from about 1.0 weight percent, in an aqueous solution of about 65 weight percent product, to about 10.0 weight percent, in an aqueous solution of about 65 weight percent product, to about 5.0 weight percent, in an aqueous solution of about 65 weight percent product. Measuring such concentrations of dihaloalcohol by-product is within the skill in the art, for instance, by gas chromatography of an extraction using an organic solvent such as ethyl ether, methylene chloride, perchloroethylene, or carbon tetrachloride of an aqueous solution of halohydroxypropyltrialkylammonium halide product, which product is most preferably in a concentration of about 65 weight percent in water. The organic layer is then analyzed on a gas chromatograph equipped with a column coated with (5 percent phenyl)- methylpolysiloxane, commercially available from J&W Scientific under the trade designation DB-5, using a flame ionization detector.

The level of starting trialkylamine hydrochloride left in the reaction solution is advantageously lower than with other processes, preferably less than about 250 ppm in a 65 weight percent solution of the product, more preferably less than about 50 ppm in a 65 weight percent solution of the product. Analysis for residual amine (as exemplified here in the form of the hydrochloride salt) is within the skill in the art. For instance, a sample containing trimethylamine hydrochloride and 3-chloro-2-hydroxypropyltrimethylammonium chloride is conveniently prepared for analysis by preparing a 0.1 weight percent sample in an ion chromatography mobile phase solution. The sample is analyzed on an ion chromatography system using a poly(butadiene)maleic acid absorbed onto amorphous silica column commercially available from Waters Corporation under the trade designation IC-PakTM Cation M/D column. The analysis is done using a conductivity detector. The mobile phase is a 98 weight percent solution of 3 millimolar (mM) HNO3/0.1 mM EDTA (ethylenediaminetetraacetic acid) and 2 weight percent isopropanol.

EXAMPLES

The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention. All percentages are by weight of the active ingredient unless otherwise specified.

Example 1 (Comparative)

This example shows preparation of a "control" halohydroxypropyl-trialkylammonium halide wherein the presence of aromatic impurities is not reduced.

To a 500 mL jacketed round bottom flask, about 334.78 g of trimethylamine hydrochloride solution (59.3 percent active) is added. The temperature of the solution is decreased to about 15 ⁰ C using a glycol bath circulated through the reactor jacket. About 10.57 g of aqueous trimethylamine (25 percent active) is added to the trimethylamine hydrochloride solution (2.12 total amine moles) to increase the pH to approximately 8.5.

Over a period of about three hours about 212.42 g of a crude waste stream of epichlorohydrin (97.56 percent active, 2.24 moles, contaminants: Ethyl benzene - 0.78%; Monochlorobenzene - 0.06%; Benzene - 10 ppm; l,3-Dichloro-2-propanol - 1.56%; 2,3- Dichloro-1-propanol - 0.04%) is added to the trimethylamine/trimethylamine hydrochloride admixture while maintaining a temperature between about 1O ⁰ C and about 2O ⁰ C.

After the epichlorohydrin feed addition is complete the reaction solution is allowed to digest for one hour at 15 ⁰ C. The reaction solution is then allowed to digest for one hour at 6O ⁰ C. The reaction solution is then heated to 7O ⁰ C and the pH is reduced to about 2 using concentrated hydrochloric acid and kept at these conditions for one hour.

The reaction product is a halohydroxypropyltrialkylammonium salt product having the detectable amount of aromatic impurity.

Halohydroxypropyltrialkylammonium salts are generally useful for preparing cationic starches. About 3.62 g of the reaction product formed above is combined with about 65.89 g of water, about 50.55 g of unmodified corn starch (approximately 88 percent active, 12 percent water), and about 9.99 g sodium hydroxide (25 percent active). Upon addition of the reactants, the starch slurry becomes too thick to stir and the resulting starch product is deemed unusable, most likely from cross-linking of the starch by dichloropropanol.

Example 2 (Comparative)

This example shows use of a commercial halohydroxypropyltrialkylammonium salt to prepare cationic starch. Commercially available QU AT™ 188 Cationic Reagent (3-chloro-2-

hydropropyltrimethylammonium chloride - 69.24%; 2,3-dihydroxypropyltrimethyl- ammonium chloride -0.13%; l,3-bis(trimethylammonium chloride)-2-hydroxypropane - 0.79%), having a calculated purity of 98.7 percent, is prepared from an epihalohydrin feed that contains no detectable amount of aromatic impurity to start. The product itself also contains no detectable amount of aromatic impurity.

To prepare a cationic starch, 3.77 g of QU AT™ 188 cationic reagent is combined with 65.92 g of water, 50.38 g of unmodified corn starch (approximately 88 percent active, 12 percent water) and 9.76 g sodium hydroxide (25 percent active) at a temperature of about 4O ⁰ C for about 16 hours. The cationic starch slurry is then filtered and washed several times with water.

The washed and dried cationic starch is analyzed to contain 0.30 percent nitrogen. This would be an acceptable cationic starch for commercial sale.

Example 3

The reaction solution from Comparative Example 1 is taken and extracted with methylene chloride eight times. The extracted solution is then sparged with nitrogen for 15 minutes. The final purified solution is analyzed for aromatic impurities. It contains 71.38 percent 3-chloro-2-hydropropyltrimethylammonium chloride, 0.08 percent 2,3- dihydroxypropyltrimethylammonium chloride, and 0.69 percent l,3-bis(trimethylammonium chloride)-2-hydroxypropane. The purity is calculated to be about 98.9 percent. In other words, surprisingly, this halohydroxypropyltrialkylammonium salt is as pure as the commercial product from Comparative Example 2. The salt product contains no detectable amount of aromatic impurity.

To prepare a cationic starch, about 3.54 g of the 3-chloro-2-hydropropyltrimethyl- ammonium chloride reaction product is combined with 65.84 g of water, 50.36 g unmodified corn starch (approximately 88 percent active, 12 percent water), and 9.77 g sodium hydroxide (25 percent active) at a temperature of about 4O ⁰ C for about 16 hours. The cationic starch slurry is then filtered and washed several times with water. The washed and dried cationic starch is analyzed to contain 0.29 percent nitrogen.

A comparison of the cationic starches is given in TABLE 3:

TABLE 3

As shown in TABLE 3, compositions formed by the presently claimed inventive methods allow use of a previously unexploited, and generally considered unworkable, impure feedstock to work as effectively as a commercial product.

It is understood that the present invention is not limited to the embodiments specifically disclosed and exemplified herein. Various modifications of the invention will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the appended claims.

Moreover, each recited range includes all combinations and subcombinations of ranges, as well as specific numerals contained therein. Additionally, the disclosures of each patent, patent application, and publication cited or described in this document are hereby incorporated herein by reference, in their entireties.