Influencing factors and control methods of storage

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Influencing factors and control methods for the storage of plant starch adhesives

in recent years, China's carton and printing industry has eliminated the use of foamed soda (sodium silicate as adhesive) and gradually selected plant starch adhesives. Adhesives made of corn starch, sweet potato starch, wheat starch and so on are commonly used as materials for bonding cartons, wine boxes, document bags, envelopes and so on

advantages of plant starch: 1) cheap raw materials, wide sources and convenience. 2) Natural plants cause less environmental pollution. 3) Non toxic side effects. 4) The glue making process is convenient and fast

disadvantages of plant starch adhesive: 1) short storage period, easy to decay and mildew; 2) Plant starch adhesive is easy to be eaten by rats and insects; 3) The viscosity of the adhesive is poor, and the color whiteness of the starch adhesive after drying is poor and becomes brittle

plant starch adhesives are easy to deteriorate and have a short storage period. This problem is caused by the factors of plant starch raw materials, such as the origin and composition of starch, the nature and content of additives, resomer reg; Lr708 is a random copolymer obtained by copolymerization of L-LA and dl-la (mass ratio 70:30), including formula, process, storage method, etc

1 the reason for the short storage period of plant starch

the storage period of plant starch glue is short, which is prone to corruption and mildew. A very important reason is insufficient gelatinization. Insufficient gelatinization is mainly caused by two conditions: one is the low dosage of gelatinizer; Second, the gelatinization temperature is low or the gelatinization time is short, so that the gelatinization of plant starch can not reach the appropriate level. Starch, water and gelatinizer shall be stirred evenly. When heated in the pot, the temperature of the bottom layer and the upper layer shall be the same. If the plant starch gel deteriorates after 3 days to 6 months of storage, it indicates that the gelatinization and complexation of the starch are insufficient, because the ungelatinized starch molecules are more vulnerable to bacterial erosion than the gelatinized starch molecules. The gelatinization temperature is high and the gelatinization reaction proceeds faster. In the thermal process, the viscosity of the hot glue is not equal to the viscosity of the liquid after cooling. Therefore, the viscosity index in the quality index of starch glue should not be directly used here to investigate the degree of complexation

2 control the pH value of starch glue

the pH value of plant starch glue produced is 7. It is alkaline because gelatinizer, complexing agent and other alkaline substances are added to the starch. If the alkalinity of plant starch glue is too strong, the imprinted ink color and the gloss of hot stamping electrochemical aluminum foil printed on paper and carton will decrease and change color. The pH value should be neutralized by acid and alkali to control the pH range at about pH 9

in addition, in the post binding and bonding process of gold and silver printing products, if the adhesive is alkaline, acidic or contains sulfide, the gloss of gold and silver printing will be reduced, resulting in serious fading and discoloration of printing products. There are many examples in work practice

3 defoaming treatment should be carried out for plant starch adhesive.

during the production and transportation process, plant starch adhesive will mix with air, and its movement law conforms to sinusoidal waveform to form bubbles. Bubbles will not only affect the use of starch adhesive, but also promote the corruption, deterioration and mildew of starch adhesive. Because there is oxygen in the air, it will oxidize the starch adhesive, causing corruption and mildew. Butanol, octanol, triphenyl phosphate, etc. are usually used as defoamers for starch adhesives. Plant starch defoamers have dual functions of defoaming and foam inhibition. The selected defoamers and foam inhibitors are non-toxic, tasteless and colorless

triphenyl phosphate is a solid insoluble in water. Because its melting point is about 50 ℃, it can be dispersed in hot water after melting, so it can be evenly dispersed in the starch glue solution, so it can effectively eliminate and inhibit bubbles in the solution in time 21187-t4

4 preservatives added to plant starch

formaldehyde and sodium benzoate are commonly used preservatives, which have strong reducibility and protect the oxidation of other additives. Adding preservatives to plant starch is the most effective way to inhibit the corruption, deterioration and mildew of starch glue. The commonly used preservative is sodium benzoate, which has an ideal anti-corrosion effect. Its dosage is 0.15% - O.3% of the total mass of starch glue. Do not add too much sodium benzoate. It is not that the more preservatives are added, the better the anti-corrosion effect will be. Sodium benzoate is a safe and non-toxic preservative, and some foods are also added with a small amount to prevent corrosion

5 storage and transportation of plant starch

too high storage temperature of plant starch glue will promote the corruption and drying of glue liquid. The storage temperature should be 20 ℃ ~ 25 ℃. It should be placed in a ventilated and cool place, avoid being directly exposed to sunlight near the window, increase the temperature, and it is better to put it in a place with stable ambient temperature. The packaging container of plant starch glue is required to be sealed without air leakage, so as to prevent the container from cracking and air leakage during handling. The starch glue is covered tightly on the surface of the starch glue with a piece of paper and plastic in the container, so as to prevent it from being oxidized and deteriorated in contact with the air. The storage appliance is not tightly sealed for a long time, which will inevitably cause the surface of plant starch glue to deteriorate

6 other

in order to prevent rat bites and moths, some manufacturers often add pesticides, BHC powder and other toxic and harmful chemicals to plant starch glue, which is very unscientific, harmful to human body and dangerous

reprinted from: packaging world

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