Starch Oxidation Modified Adhesive (in)

Du Jiangong et al. started with the oxidation mechanism of H2O2 to starch molecular chains, and thoroughly analyzed the whole process and relevant mechanism of acidification degradation-catalysis-oxidation-gelatinization of starch molecular chains, and the stability and main influencing factors of the binders. Discussed. Raw materials are hydrogen peroxide, sulfuric acid, hydrochloric acid, heavy metal catalysts, sodium hydroxide, borax, and the like. Hydrogen peroxide under the action of acid and catalyst, the starch molecules degrade rapidly to reach the required viscosity. At the same time, the starch molecules have a certain amount of carboxyl or aldehyde groups. During the gelatinization and storage process, these strong hydrophilic groups The function of the agglomerates and the presence of an appropriate amount of base are used to maintain the stability of the adhesive viscosity to maintain an optimum use of the adhesive.
Li Qiaoyun mixes the appropriate amount of water and starch at room temperature with water and dissolves polyacrylamide first. After adding appropriate amount of NaOH, a small amount of FeSO4 is used as a catalyst, oxidation is performed with H202 (reaction time is 1 h), borax is added to crosslink, and finally. Add driers bentonite (-200 mesh) and other additives (tributyl phosphate, etc.).
1.2 Potassium Permanganate (KMn04)
Wang Yanbin, Su Qiong Process for preparing oxidized starch by using potassium permanganate composite oxidant: Add 50 kg of starch and 90 L of water into the reactor, start stirring, stir the material until it becomes homogeneous emulsion, and heat up with electricity. The reaction temperature was controlled at 5°C, 1% ferrous sulfate and 0.5% FeCl3 were added, and reacted as a catalyst with potassium permanganate at 55-60°C for 2-3 hours. When the solution was milky white, the oxidation reaction occurred. At the end of the reaction, 50 kg of water was added to the reaction mixture, and the mixture was stirred at 55° C., and then the prepared 30% NaOH was added for gelatinization for 20 min to obtain a stable fluid liquid. The borax was dissolved in the solution and the tributylase was 15 kS. Bentonite, 0.5kg of carboxyethyl cellulose in 50kg aqueous solution was added to the reactor, stirred thoroughly at 55°C to obtain yellow thick viscous starch glue, modified by adding 3% urea-formaldehyde resin to obtain modified starch glue.
Deng Bo and Tang Hongmin use KMn04 as an oxidant and reaction indicator, borax as a tackifier, and urea-aldehyde condensate as a drier to make a starch adhesive. The process is simple, no heating equipment is required, and the product quality is stable. Can save for a long time. The addition of borax can increase the degree of cross-linking, increase the initial viscosity, corrugated board will not run edge; adding urea aldehyde condensate can increase the drying speed, prevent glue from penetrating the back of the paper and affect the quality of the carton. The synthesis process is: a. Pretreatment: Put the cornstarch in the reaction barrel, add water to stir, and slowly add the NaOH solution under stirring, so that the pH of the reaction mixture is in the range of 10-11. The mixture was stirred about 20 minutes once every 2 minutes, and after 1 hour, it was filtered with double gauze. Static precipitation, remove the upper water reserve; b. Oxidation: Add fresh water to the pretreated starch, stir well, slowly add a solution of concentrated sulfuric acid and water under stirring, stir well, and then add a solution of potassium permanganate and water, stir well. After that, place it for a day (shorter hot days, longer cold days), during which it is stirred several times until the starch turns to white, and then the siphon removes the upper layer of water; c. Rinse: Add water to the oxidized starch, stir, stand, and siphon to remove the upper layer of water. Add water and stir evenly, and let stand and siphon to remove the upper layer of water; d. Gelatin Add clear water to the oxidized starch after rinsing, and then slowly add the solution of sodium sulfide and water under stirring. After the addition, stir well and place it for 30 minutes (stirred every 10 minutes). Then add a solution of caustic soda and water slowly under stirring. After the addition, stir well. If the foam is too much, appropriate amount of tributyl phosphate can be added to defoam (if the amount is too much, the product viscosity decreases); e. Complexation: The solution of borax dissolved in hot water is slowly added to the paste under stirring, and then stirred for 10 minutes after the addition; f. Modification: Mix urea with formaldehyde, heat to 90°C in a well-ventilated place, cool to room temperature, and add it to the complexed paste under stirring. Stir thoroughly after adding. 8. Water transfer ratio: According to the actual rotational speed requirement of the corrugated board machine, the consistency of the starch glue should be adjusted. When the rotation speed is high, the glue liquid should be thin, otherwise the phenomenon of glue rejection will occur. The season also has an effect on the water ratio, with higher winter water ratios and lower summer water ratios. In general, the total weight ratio of starch to glue is 1:7 to 1:8.
Wang Yanbin and Su Qiong comprehensively evaluated the characteristics, reaction conditions, product performance, and economic benefits of various types of oxidants, and used KMnO4 oxidant to thermally oxidize under acidic conditions, with the shortest time, easy control of reaction, low consumption of oxidants, and low cost. The product performance meets the basic requirements for coating film forming substances. The stability can be adjusted by the oxidant concentration, pH value, reaction temperature, and time; the color of the glue solution can also be controlled by the presence of manganese. Cheng Cungui et al. used corn starch as a raw material to produce oxidized starch by oxidation of potassium permanganate, together with urea-formaldehyde resin, catalyst, driers, preservatives, etc., and used thermal oxidation, phosphoric esterification, and polymer monomers. The unique method combining the branch copolymerization method effectively solves the problems of poor starch stability and short storage period, and develops a highly stable oxidized starch adhesive for corrugated board with quick drying characteristics. Zulixia et al. oxidized corn starch with potassium permanganate at 60-65°C to obtain a milky white oxidized starch. Crosslinked with glyoxal and magnesium chloride to obtain a viscous viscous liquid. Crosslinked oxidized starch adhesive was prepared. The water resistance and drying speed are better than ordinary oxidized starch adhesives.
1.3 Sodium Hypochlorite NaCIO
Wang Yanbin, Su Qiong Modified corn starch into 40% starch milk in the reactor, adjusted the pH to 10 with 3% NaOH solution while stirring, added 2% NaClO dry weight to the starch, and adjusted the pH to 6 at any time with HCI. To prevent the swelling of the starch granules, washing with Na2Cl3 solution and drying. Xu Jianqiu chose sodium hypochlorite and studied the influence of various influencing factors. a. Starch milk concentration effect: Starch milk concentration has little effect on reaction speed and viscosity. Within a certain concentration range, as long as the product quality can be ensured, increasing the concentration can increase the equipment utilization rate and yield, and production is preferably 18 to 25°C. ;b. The effect of pH: pH has a great influence on the oxidation reaction, pH is between 8 and 10, the reaction time is short; c. Temperature control: The higher the reaction temperature, the faster the reaction. However, if the temperature is too high, the starch granules gelatinize and swell, thereby affecting the progress of the reaction, and the generated salts and chloride ions are difficult to remove. Due to the high temperature, the color of the finished product may be affected, which affects the quality of the product. Temperature control in trial production is suitable at 35-40°C. Since the reaction is an exothermic reaction, the temperature of the cooling water can be lowered to the optimum temperature through the interlayer of the enamel reaction pot. d. The amount of oxidant: the amount of sodium hypochlorite is 10% to 20% of dry starch, that is, the ratio of available chlorine content to dry starch is 1%; e. Time control: The length of reaction time has a great relationship with several factors in front. The time is generally controlled at 5~8h; f. Cleaning: Centrifugal dryer is used to clean the water several times to remove free Cl- and soluble impurities. (To be continued)