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    Home > Chemicals Industry > Chemical Technology > Cationic Starch (2)

    Cationic Starch (2)

    • Last Update: 2021-12-31
    • Source: Internet
    • Author: User
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    (5) Highly substituted cationic starch

    Weigh 7.


    The preparation methods of quaternary ammonium cationic starch can be roughly divided into organic solvent method, water solvent method and dry method


    The current industrial applications are mainly low-substitution quaternary ammonium alkyl starch ethers, and high-substitution cationic starches have different degrees of application performance, such as flocculation, decolorization, and dye coloring rate, as the degree of substitution increases.


    (1) In a simple glass bottle equipped with a stirrer, add 5.


    (2) using ethanol as the raw material and a- amylase and hemicellulase were mixed in a liquid containing cationic starch reacted at 50 ~ 60 ℃ and 6bar, the membrane then separated and refined


    (3) In order to improve the efficiency and speed of the reaction, the semi-dry method can be used to prepare the epoxy quaternary ammonium cationic agent, that is, an alkali catalyst and a small amount of organic or inorganic solvent are added to the reaction system, and the reaction is carried out at 60~90℃ for 2h, the conversion rate It is 95%


    Add a small amount of sodium hydroxide and an appropriate amount of water into the beaker, add an appropriate amount of starch after the sodium hydroxide is dissolved and stir for 10 minutes, add 2 mL of isopropanol , and then add GTA and stir for 1 hour


    Adding a small amount of organic solvent in the reaction process can reduce the solubility of water to starch and prevent starch gelatinization; it can also maintain the swelling state of starch, so that the cation reagent and alkali catalyst are evenly distributed in the reaction system, and the reaction efficiency is improved.


    In the presence of an alkali catalyst, starch and N-(2,3-epoxypropyl)trimethylammonium chloride are reacted in a semi-dry process


    (4) Dry the industrial starch with airflow to make the water content less than 3%, weigh 60g and place it in a mixer equipped with a high-speed mixer


    The heating process of dry preparation of cationic starch is generally the medium transfer heat


    Microwave dielectric heating is the action of electromagnetic waves on polar molecules, causing them to vibrate and rotate, and the electromagnetic waves are converted into heat energy


    Microwave radiation will produce "local hot spots", that is, the overall temperature of the system is still very low, but the temperature in a certain area rises relatively high


    Microwave is an electromagnetic wave with a frequency ranging from 300MHz to 300GHz.


    Microwave technology is applied in the fields of chemical reactions, chemical analysis and environmental protection, and shows the advantages of saving energy and time, simplifying operating procedures, reducing the use of organic solvents, increasing the reaction rate and significantly reducing the environmental hazards caused by waste generated by chemical reactions


    Mix the cationic etherifying agent with the NaOH aqueous solution in a certain proportion, spray the mixture on the starch quickly, mix well, put it in the microwave oven, after the reaction is completed, take out a part of the crude product and wash it with absolute ethanol several times, filter it under 50℃ After drying, quaternary ammonium salt type cationic starch is obtained


    In the process of microwave dry synthesis of quaternary ammonium salt type cationic starch flocculant, a small amount of water needs to be added.
    The activation of starch, the ring closure of quaternary ammonium salt and the synthesis of cationic flocculant all require free OH-; at the same time, water is still microwave Initiator of dielectric heating solid phase reaction
    .
    Generally, solid materials cannot effectively absorb microwaves
    .
    Only polar small molecules like water, alcohol, acid, etc.
    can effectively absorb microwave energy, turn electromagnetic waves into chemical energy, and initiate the cationization reaction of starch
    .
    But on the other hand, water solvents can cause two side reactions: one is the hydrolysis reaction of the cationic etherification agent.
    The by-products generated after hydrolysis have no cationization ability, so that the effective concentration of the cationization agent in the reaction system is reduced, and the product is The relative viscosity decreases; the second is that the water solvent decomposes the generated cationic starch to produce starch and cationic etherifying agent hydrolyzate, which also causes the relative viscosity of the product to decrease
    .
    Therefore, too much water is not conducive to the progress of the reaction
    .
    The above experimental results show that the mass fraction of water in the reaction system is about 30% and good results are obtained
    .

    Under the condition that the molar ratio of cationic etherifying agent to starch is 0.
    35, the molar ratio of NaOH to cationic etherifying agent is 1:2, and the microwave power is 184W, the radiation time is 5min
    .

    Radiation is the use of radiation (UV, EB, rays, visible light, fluorescence, etc.
    ) to irradiate the object to be processed in the liquid phase, so that the molecules will be instantly excited under the action of high-energy rays, and then a rapid chemical reaction process will occur, resulting in excellent performance Product
    .
    It has the characteristics of high speed, low energy consumption, almost no pollution, and suitable for continuous production
    .

    Radiation technology has developed into a new type of "green" technology with characteristics and application advantages, which is called "new technology for green industry facing the 21st century"
    .

     

     

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