FI107387B - A new cationic starch, its preparation and use - Google Patents

Description

This invention relates to a novel cationic starch, its preparation and its use as an additive in the manufacture of paper.

Water soluble cationic starches are used as an additive at the wet end of papermaking to, among other things, increase retention and improve the tensile strength of the paper. The cationization of starch is accomplished by processing the starch with reagents containing cationic groups si-10. Such a cationization reagent may contain cationic amino, immonium, ammonium, sulfonium or phosphonium groups, but today, the industrially most important cationic starches are prepared by etherifying starch with compounds containing tertiary amino groups or quaternary ammonium groups. Of these, starches containing quaternary ammonium groups are most preferred because, unlike cationic starches containing amino groups, they are cationic under both acidic, neutral and alkaline conditions. Quaternary starches are prepared by forming ether or ester bonds between the hydroxyl groups of the starch structure and the cationization reagent.

In addition to cationization, industrial cationic starches are also often modified by esterification or etherification of the starch structure with short-chain carbohydrates, and by anionization and cross-linking of the cationic starch.

The first cationic starches for use as a paper additive were patented in U.S. Pat. No. 2,813,093 in 1957 and since then, cationic starches have been one of the most common wet-end chemicals in papermaking (see, e.g., Modified Starches: Properties and Uses, eds. Cationic starches are further developed for paper and other applications. At present, ",« ». · Tertiary or quaternary aminoalkyl ethers of cationic starch are the 30 most common additives in papermaking. In the textile industry, cationic starches 107387 can be used to improve the fabric feel of the fabric and to increase the retention of anionic impurities in flocculation processes in waste water treatment.

So far, starch has been cationized with compounds of petrochemical origin, and Ny-5 seeks to find more natural solutions by conserving non-renewable resources and exploiting renewable resources by demonstrating e.g. new uses for agricultural by-products. A new cationized starch made from natural products has now been invented to meet this need. The starch according to the invention also has the advantage that it is well suited for cationization in food and paper and board used in food packaging due to its non-toxic properties, food grade properties and beneficial nutritional properties of betaine.

The present invention demonstrates that cationized starch can be prepared by esterifying starch with betaine or trimethylglycine. The water-soluble cationic starch thus produced, i.e. starch betainate, can be used as a food additive at the wet end of papermaking to improve e.g. retention, water permeability, and strength of the paper produced.

Betaine is an internal salt containing a quaternary cationic trimethylammonium group. Betaine is a natural substance commonly found in natural plants, especially in sugar beet. Betaine is thus a natural and renewable product, and it: - thus differs completely from the cationization reagents known hitherto, which are of petrochemical origin and quite toxic. The structural formula of betaine is shown in the following figure.

CH, l +

CH.-N-CH? -COO

3 I 2 ch3 The starch may be any naturally occurring starch, for example tuber-30 starch (e.g. potato), root starch (e.g. tapioca, airow root or sweet potato), or cereal starch (e.g. barley, wheat, rice or sorghum). . For esterification, whey starches, modified starches, modified starches, hydrolyzed or oxidized starches, acid treated starches, or even other long chain polysaccharides may also be used.

Starch esters, their preparation and properties, and applications have been known per se for decades, as shown in, e.g. Starch: Chemistry and Technology, 2nd Ed., edited by RL Whistler, JN BeMiller and EF Paschall, Academic Press Inc. 1984 and Modified Starches: Properties and Uses edited by OB Wurzburg, CRC Press, Boca Raton, 1986. Starch esters are used in particular. plastics and additives, textiles and papermaking, especially for 10 paper coatings. Cationic starch esters have not been described in the literature with the exception of a few exceptions: the preparation and use of starch anthranilic ester as a paper retention agent is described in US 3,620,913 (1971) and in the preparation of starch reaction products using isatoic anhydride US 3,511,830 (1970), US 3,513,156 (1970) and US 3,620,913 (1970). This results in the formation of anthranilate esters having primary amino groups which can, if desired, be cationized by either low pH or by alkylation with alkyl halides, sulfonates or other alkylation reagents. Similarly, the use of isatoic anhydride or quinoline anhydride, i.e. 2,3-pyridinedicarboxylic acid anhydride, in the esterification of starch is described in US Patent 3,052,561 (1962). The prepared products are recommended for use in the preparation of cationic starch. DE 4,208,946 A1 to Wacker-Chemie GmbH describes the preparation of amino acid esters of starch, but the process of cationization of the products is not disclosed at all and the products are shown to be mainly suited to the needs of the pharmaceutical industry.

25

The use of betaine hydrazide in the derivatization of dialdehyde starch has been previously described in the preparation of retention agents for use with pulp fibers (C. L. Mehltretter, T. E. Yeates, G. E. Hamerstrand, B. T. Hofifreiter and C. E. Rist, Tappi 44, 1962, 750). However, the starch hydrazones formed are toxic, their preparation is complicated, and the products are by no means organic.

The present invention uses a natural amino acid, betaine, to cationise starch. Depending on the degree of substitution of the product, organic starch, strongly or weakly cationized, is obtained directly. The product is suitable for use as a papermaking retardant, for reducing the water retention capacity of the pulp and for enhancing the strength of the paper. The cationized starch described herein can also be advantageously used to purify process water from the fines, for example in the context of TMP pulping, as described by V. Bobackan, J. Näsman, and D. Eklund 1998 5 (Journal of Pulp and Paper Science 24, 1998,78). Because of their physiologically acceptable properties, the starch betaine ester is particularly suitable as an additive for food paper and board and for treating effluent water.

Cationic starch betainate is prepared by esterifying the hydroxyl groups of starch with betainyl chloride or betainyl anhydride. The betainyl chloride used for the esterification is prepared from betaine anhydrous, betaine hydrochloride or other inorganic or organic salts of betaine. Betaineyl chloride is an acid chloride which can be readily prepared from betaine by known acid chloride preparation methods. Preferably, betainyl chloride can be prepared from betaine using, inter alia, thionyl chloride or oxalyl chloride in the presence of N, N-dimethylformamide. Betainyl anhydride, in turn, is an acid anhydride prepared by dehydration of betaine, betaine hydrochloride or other inorganic or organic salts of betaine.

20 The structural formula of starch betainate is shown below. St represents the polymer structure of the starch.

O CH, II I *

The esterification reaction is performed in an organic solvent, preferably 1,4-dioxane or toluene, using a tertiary amine, preferably pyridine, as the esterification catalyst. The reaction is carried out at a relatively high temperature, preferably near the reflux temperature of the solvent used. The reaction time is 1 to 24 hours, preferably 2 to 6 hours. An example of an esterification reaction is given below. When the esterification is carried out using betaine anhydride, the esterification may also be carried out in alkaline ·; water mixture.

5, 107387

The invention will now be explained in the light of the examples.

Example 1.

In this example, dry, native potato starch is esterified. The esterification reaction was carried out in 1,4-dioxane and pyridine was used as the esterification catalyst. For laboratory scale, the procedure described below was used. The degree of substitution of the reaction product can be influenced by the reaction time, the amount of catalyst, and the amount of betainyl chloride added.

13 g of potato starch 15.8 g (0.33 eq.) Of betaineyl chloride 19.8 ml (1 eq.) Of 156 mg of 1,4-dioxane The starch was stirred in refluxing pyridine for 30 min. 156 ml of 1.4-20 dioxane and 13.9 g of betainyl chloride were added and the reaction mixture was refluxed for 4 hours under argon at 110 ° C. The solvent was poured from the reaction vessel and the product was dissolved in water. The product was precipitated from water by adding ethanol and the precipitate formed was filtered. The product was collected, washed with a mixture of ethanol and diethyl ether and dried in vacuo. The yield was 14.3 g (63%) and the degree of substitution of the product was 0.9 (theoretical 1.0).

Example 2.

30 g of potato starch 18.3 ml (1 eq) of pyridine 9.5 g (0.25 eq) of betainyl chloride in 150 ml of 1,4-dioxane 6 107387 Starch was stirred in refluxing pyridine for 30 min. 150 ml of 1,4-dioxane and 9.5 g of betainyl chloride were added and the reaction mixture was refluxed for 4 hours under argon at 110 ° C. The solvent was poured from the reaction vessel and the product was dissolved in 5 water. The product was precipitated from water by adding ethanol and the precipitate formed was filtered. The product was collected, washed with a mixture of ethanol and diethyl ether and dried in vacuo. The yield was 11.83 g (60.6%) and the degree of substitution of the product was 0.39 (theoretical 0.75).

10

Example 3.

15 g of barley starch 23 ml (1 eq) of pyridine 15 14.3 g (0.3 eq) of betainyl chloride in 200 ml of 1,4-dioxane

Barley starch was stirred in refluxing pyridine for 30 min. 200 ml of 1,4-dioxane and 14.3 g of betainyl chloride were added and the reaction mixture was refluxed for 4 hours under argon at 110 ° C. The solvent was poured from the reaction vessel and the product was dissolved in water. The product was precipitated from water by adding ethanol and the precipitate formed was filtered. The product was collected, washed with a mixture of ethanol and diethyl ether and dried in vacuo.

. The yield was 16.15 g (61%) and the degree of substitution of the product was 0.07 (theoretical 0.9).

25

Example 4.

• • <.

30 g of potato starch 7.6 ml (1 eq.) Of pyridine 6.3 g (0.4 eq.) Of betainyl chloride in 60 ml of toluene 7 107387 Starch was stirred in refluxing pyridine for 30 min. 60 ml of toluene and 6.3 g of betainyl chloride were added and the reaction mixture was refluxed for 4 hours under argon at 115 ° C. The solvent was poured from the reaction vessel and the product was dissolved in water. The product was precipitated from water by adding ethanol and the precipitate formed was filtered. The product was collected, washed with ethanol and water and dried in vacuo. The yield was 1.12 g (11.2%).

The cationic, water soluble starch betainate prepared is added to the wet end of the papermaking process by 0.1 to 2% of the amount of pulp fiber to improve the fines, pigments, water permeability and strength of the paper produced.

10

The cationized starch according to the invention can also be used as an aid in the textile industry and in the purification and utilization of waste water, in particular lignin-containing waste water.

The following table shows a few examples of starch betainates prepared in connection with the invention.

Table 1. Starch betainates and properties obtained with them Sample starch DS Tear Tensile Turbidity b) Strength index) (NTU)% index) (Nmg'1) Pulp (mNmV ') •: Without starch 0 ... 9.25 61.33 0.5 Starch betainate 0.6 0.44 9.95 67 0.3 Starch betainate 0.6 0.21 9.72 64.33 0.5 Starch betainate 0.6 0.06 8.8 60.83 0 , 4a) The results were measured according to the SCAN-P 38:80 and SCAN-P 11:73 standards using 60 g / m 2 sheets of bleached birch pine (60/40) pulp.

b) Bleached birch-pine (60/40) sulphate pulp was used in the tests and turbidities were measured with a HACH 2100 AN IS turbidimeter.

Claims (5)

8 107387 Novel cationic starch characterized in that it consists of starch and betaine and that in the product betaine is covalently bonded by ester bond to 5 parts of the starch hydroxyl groups and that the product has the following structural formula wherein St represents the polymer structure of starch. O CH, Il l St-O-C-CH 2 -N-CH 3 ch 3 10 Process for the preparation of a novel cationic starch according to claim 1, characterized in that the cationic starch is prepared by esterifying the hydroxyl groups of the starch with betainyl chloride in an organic solvent using a tertiary amine as the esterification catalyst. 15 Process for the preparation of a novel cationic starch according to claim 1, characterized in that the cationic starch is prepared by esterifying the hydroxyl groups of the starch with betainyl anhydride in an alkaline aqueous mixture or in an organic solvent using a tertiary amine as the esterification catalyst. • ·: 20 A method according to claim 1 or claims 2 to 3. Use of cationic starch prepared according to the invention as a papermaking additive. Use according to claim 4, characterized in that the novel cationic starch is used as an additive to the wet end of papermaking to improve the retention of fines, the water-release properties of the web and the strength of the paper produced. 9 107387