Modified starch and preparation method and application thereof

Abstract

The invention relates to modified starch and a preparation method and application thereof. The modified starch is mainly prepared from a starch aqueous solution and a cationic starch complexing agent;the chemical structure of the cationic starch complexing agent is composed of the following parts: (i) one or more hydrophobic groups, wherein at least one hydrophobic group is capable of reacting with starch to form an inclusion complex, and (ii) one or more hydrophilic groups, wherein at least one of the hydrophilic groups is a cationic hydrophilic group; and the hydrophobic groups and the hydrophilic groups are separately located at two ends of a same molecular structure and are bonded through chemical bonds to form an asymmetric and polar structure. The modified starch is used for papermaking, the adsorption rate of the starch on the surface of fibers or in pulp can be greatly increased, so that the retention rate of the starch in paper is increased, the strength of the paper can be improved, the loss of the starch in the pulping and papermaking processes is reduced or even eliminated, and thus COD emissions are reduced.

Description

technical field [0001] The invention relates to the technical field of papermaking and starch modification, in particular to a modified starch and its preparation method and application. Background technique [0002] Starch is a natural high-molecular carbohydrate that widely exists in seeds, stems or roots of plants. It is abundant in resources and low in price. It is widely used in industries such as industry, food, textiles, papermaking, feed, medicine, construction, and drilling. . Starch is one of the most important raw materials for papermaking. It is often the fourth largest component of paper and board by weight, after cellulose, inorganic fillers and moisture. Cultural and packaging paper and paper plates are major users of starch. The consumption of starch in the papermaking industry in the world is about 5 million tons, which is about 1.6% of the total output of papermaking and paper plates in the world. [0003] China's paper production has maintained rapid d...

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Problems solved by technology

The above methods have disadvantages. The cationic starch produced by the wet method not only consumes a lot of water, but also the discharged sewage pollutes the environment. The wastewater is difficult to treat, and the alkaline chemicals used can lead to starch degradation and transformation. low rate

Dry production is to mix starch with reactive chemical reagents, dry to almost anhydrous and then react at 120-150°C. Although the pollution is less, the disadvantages are low reaction conversion rate, relatively high requirements for equipment and technology, and high production costs. , production conditions are difficult to control, starch products are easily over-gelatinized, which affects product quality, and the reaction cycle is long and energy consumption is high; the organic solvent method uses a large amount of water-soluble organic solvents (such as methanol, ethanol, isopropanol, etc.) in the preparation process ), disperse the starch in it to form a slurry, and react with the cationizing agent to prepare the cationic starch

Due to the use of a large amount of organic solvents, this method has the disadvantages of high production cost, poor safety, and easy pollution of the environment, so it is rarely used in industry.

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