FI73227C - Process for preparing a cationic starch. - Google Patents

Description

1 73227

Method for preparing cationic starch

The preparation of cationic starch is a well-known commercial method. An initial aqueous slurry process 5 for quaternizing starch using the reaction product of epichlorohydrin and amine is disclosed in U.S. Patent 2,876,217. It is also contemplated in the art that such a process should use an alkali metal salt, e.g. Starch 10 is usually slurried in water to a dry weight of about 10-42%. Reaction times are usually 12 to 20 hours, the slurry is maintained at a pH between 11 and 12, and the temperature must be low to prevent gelation during the process, usually from room temperature to 50 ° C. The reaction product must then be neutralized and washed to remove salts. According to U.S. Pat. No. 3,422,087, cationic starch products can be prepared without alkali and at a much higher temperature than normal, up to temperatures just below 200 ° C, which is the tanning temperature of the polysaccharide.

The invention relates to a process for the preparation of cationic starch by reacting a halohydrin-quaternary amine with starch in an alkaline aqueous slurry having a dry starch solids content of at least 40% by weight in the presence of an alkaline catalyst. The process is characterized in that (1) the reaction is started using 0.35-1.2% alkali metal oxide or hydroxide, based on the total weight of the reaction mixture, and (2) 0.15-0.8% alkaline earth metal oxide is then added, based on the total weight of the reaction mixture, to complete the reaction.

The use of a combination of an alkali metal oxide or hydroxide and an alkaline earth metal oxide or hydroxide as a catalyst in a specified reaction in the reaction lowers the viscosity of Kati-35 onic starch and allows the use of solid starch up to 46% by weight (dry weight) to give the desired product. compared to the use of alkali metal oxide or hydroxide or alkaline earth metal oxide or hydroxide alone. When a halohydrin-quaternary amine reacts with an alkaline earth metal oxide or hydroxide, an epoxide group is formed from a halohydrin group.

The catalyst of the present invention is a combination of an alkali metal oxide or hydroxide and an alkaline earth metal oxide or hydroxide used sequentially, the latter being added after the start of the reaction by the former. The alkali metal oxide or hydroxide is used in a concentration of 0.35 to 1.2% by weight and preferably 0.6 to 1.0% by weight, and the alkaline earth metal oxide or hydroxide is used in a concentration of 0.15 to 0.8% by weight, preferably 0.3 to 0%, At a concentration of 6 ppm to 15%. When less than the indicated amount of either catalyst is used, low yields are obtained and insufficient lime can be added from the gel mill. Too much of both is uneconomical and mixing of the reactant slurry with too much alkaline earth metal oxide or hydroxide becomes difficult and filtration is difficult when too much alkali metal oxide or hydroxide is used. The alkali metal is preferably sodium or potassium and the alkaline earth metal is preferably calcium or barium.

The halohydrin-quaternary amine has the formula O independently selected from the group consisting of C 1 -C 4 straight chain and branched alkyl radicals, provided that the total number of carbon atoms in the groups R, R and R 2 is not more than 8 and n is 1-3. Thus, for example, 73227 starch is reacted with 3-chloro-2-hydroxypropyltrimethylammonium chloride according to the process of the present invention using an aqueous starch slurry containing 40-46% by weight of 5 dry starch, 2-4% by weight of 3-chloro-trichloroethyltrimethylmethyl In the presence of 0.5-2.0% by weight of anti-gelling agent, all percentages are calculated from the total reaction mixture. At lower temperatures, which reduce the rate of gelation, the use of an anti-gelling agent can be dispensed with, but to reduce the reaction time, the temperature must be raised and an anti-gelling agent used. Even at low temperatures, it is preferable to use an anti-gelling agent because it itself increases the rate of the reaction.

If the amount of starch in the slurry is less than 40%, the yields become unfavorably low, while for those greater than 46% the mixing of the reactants is difficult and there is a possibility of gelation. If the cationic reagent is used less than the lower use limit, the product is less effective as a paper additive. A usable amount greater than that mentioned is uneconomical and no additional benefits are obtained. A higher than useful amount of anti-gelling agent is also uneconomical and does not provide additional benefits.

The reaction time is 4 to 14 hours depending on the temperature, and is preferably 7 to 10 hours. Temperatures in the range of 35-60 ° C and preferably in the range of 45-55 ° C are used.

The yields in the process of the present invention are 70-85%. This can be compared to known and conventional yields in the range of 55-60%. In addition to yield advantages, 35 shorter reaction times and reduced waste disposal are achieved.

Although corn starch is used in the following 4,73227 experiments, cereal, rice, potato and waxy corn starches can also be used in the present method.

Suitable anti-gelling agents include, for example, Na 2 SO 4, NaCl, KCl, K 2 SO 4, Na 2 CO 3 and K 2 CO 3. Sulfates are preferred.

When the reaction is complete, the resulting cationic starch is usually neutralized with an acid such as hydrochloric acid, citric acid, nitric acid, phosphoric acid or adipic acid to a neutral pH of 10 or below, usually to a pH of about 6.

After neutralization, the product is usually filtered and washed. The product obtained is usually dried before use.

The following experiments illustrate the invention and the known art for comparison.

Examples 1-12 and Comparative Examples A-D

In Example 1, a 1,500 ml round bottom flask was equipped with a stirrer and placed in a constant temperature bath at 50 ° C. To the flask were added 15.4 g of a 50% solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride and a basic solution prepared by dissolving 2 g of NaOH in 97 g of water. The contents of the flask were mixed and after epoxide formation, determined from a decrease in pH from 13.2 to 13.3 (after about 2 minutes), 121.74 g of corn starch mixed with 2.7 grams of Na 2 SO 4 was added to the vessel at a rate to ensure a uniform dispersion. (10-15 minutes). This mixture was heated with stirring at 50 ° C for 10 minutes, during 30 minutes the pH dropped to about 10. A slurry containing 1 g of CaO in 3 grams of water was then added, increasing the pH from 10.0 to 11.4. The mixture of reactants was kept at this temperature with stirring for 8 hours. At the end of this reaction period, 10 ml of water was added to further reduce the viscosity. The pH was then lowered to 6.5 by neutralization with 1N hydrochloric acid. The starch slurry was filtered and washed four times with 100 ml of water. In this experiment, a nitrogen content of 0.463% was obtained, which was a yield of 79% based on 3-chloro-2-hydroxypropyltrimethylammonium chloride.

Examples 2-12 and Comparative Experiments A-P were performed in the same manner. The order of addition (unless otherwise indicated) was always: (1) sodium hydroxide, (2) water, (3) chlorohydrin-quaternary-amine salt, (4) starch + salt inhibitor, and (5) calcium oxide.

The temperatures at which the reactions were performed were: in Examples 2-6 and Comparative Experiment D, 45 ° C; in Examples 7-12 and Comparative Experiments A-C, 50 ° C. All reaction times were 8 hours.

The amounts of catalysts (a) NaOH and (b) CaO are given for each example and comparative experiment, as well as the amounts of quaternary salt (quat), water, starch and inhibitor salt (Na2SO4).

All samples were neutralized to pH 6 after completion of the reaction, filtered and washed Four times with 100 milliliter of 20 liters or 10 milliliters of water depending on the size of the reaction. Yield was measured as nitrogen growth analyzed according to the Kjeldahl method.

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Claims (4)

73227 Claim A process for preparing cationic starch by reacting a halohydrin quaternary amine with starch in an alkaline aqueous slurry having a dry starch solids content of at least 40% by weight in the presence of an alkaline catalyst, characterized in that (1) the reaction is started using 0.35- 1.2% of alkali metal oxide or hydroxide, based on the total weight of the reaction mixture, and (2) 0.15 to 0.8% of alkaline earth metal oxide, based on the total weight of the reaction mixture, is then added to complete the reaction. Process according to Claim 1, characterized in that the alkali metal is sodium or potassium and the alkaline earth metal is calcium or barium. Process according to Claim 1, characterized in that up to 46% by weight of starch is used from the reaction mixture. Process according to Claim 1, characterized in that a gelling inhibitor is added to the reaction mixture before the addition of the alkaline earth metal oxide catalyst.