Factors Affecting Storage of Plant Starch Adhesives and Control Methods

In recent years, China's cartons and printing industry have eliminated the use of brewing alkali (water glass as a binder) and gradually selected vegetable starch glues. The commonly used corn starch, sweet potato starch, wheat starch, etc. are used as glue boxes and wines. Boxes, paper bags, envelopes and other materials.
The advantages of plant starch: 1) The raw materials are cheap, the sources are wide and convenient. 2) The natural plant environment is less polluted. 3) No toxic side effects. 4) Glue processing is quick and easy.
Disadvantages of vegetable starch binders: 1) Short storage period, easy to spoil, mold, moldy; 2) Plant starch adhesives easily bitten by rat bites; 3) Poor adhesion of adhesives, color of starch gums after drying The degree is poor and it becomes brittle.
Vegetable starch adhesives are prone to spoilage and have a short shelf life. This problem arises because of the factors of the plant starch raw material itself, such as the origin and composition of the starch, the nature and content of the additive, the formulation and the process, the manner of storage, and the like.
1 The short storage period of plant starch The reason for the short shelf life of plant starch gum, which is prone to spoilage, mildew, and mouldiness, is one of the most important causes of insufficient gelatinization. Gelatinization is mainly caused by two conditions. The first is the amount of gelatinizer. Less; Second, the gelatinization temperature is low or the gelatinization time is short, so that the gelatinization of plant starch can not reach a suitable level. Starch, water and pasting agent require uniform stirring. When placed in a pan, the temperature of the bottom layer and the top layer should be the same. If the vegetable starch gum is degraded during storage from 3 days to 6 months, it indicates that the starch is gelatinized and undercomplexed because the non-gelatinized starch molecules are more susceptible to bacterial attack than the gelatinized starch molecules. The gelatinization temperature is high and the gelatinization reaction proceeds faster. The viscosity of the hot glue in the hot-process glue is not equal to the viscosity of the glue after cooling. Therefore, the viscosity index in the starch quality index should not be directly used to examine the degree of complexation.
2 The pH value of the starch glue produced by the control of the starch glue has a pH value of more than 7, which is alkaline. This is due to the addition of pasting agents, complexing agents and the like in the starch which are all alkaline substances. If the alkali is too strong, the color of the printed ink on the paper or paper box, the glossiness of the hot stamping electro-aluminum foil will be decreased and discolored, and the pH value shall be neutralized with the pH to control the pH value to be around 9.
In addition, in the binding process of gold and silver products after sequential binding, if the adhesive is alkaline, acidic or contains sulfides, etc., the gloss of printed gold and silver will be reduced, causing more serious prints. Fading, discoloration, and many examples of work practices.
3 Plant starch adhesives should be defoamed
In the process of production and transportation of vegetable starch glue, air will be mixed into bubbles, which will not only affect the use of starch glue, but also will promote the deterioration and mildew of the starch adhesive. Oxygen in the air will oxidize the starch binder and cause spoilage and mildew. Starch gum usually uses butanol, octanol and triphenyl phosphate as defoamers. Plant starch defoamer has dual functions of defoaming and foam suppression. The defoaming and foam suppressing agents used are non-toxic and odorless. Colorless is the best.
Phosphate triphenyl phosphate is a solid that is insoluble in water. Since its melting point is about 50°C, it can be dispersed in hot water after melting, so it can be uniformly dispersed in the starch glue solution, so that it can eliminate and inhibit the liquid in a timely and effective manner. bubble.
4 Preservatives added to plant starch Formaldehyde and sodium benzoate are commonly used preservatives and have strong reducibility to protect the oxidation of other additives. Adding preservatives in the vegetable starch is the most effective way to inhibit the corruption, deterioration, and mildew of the starch gum. Commonly used preservatives are sodium benzoate, the effect of anticorrosion is ideal, the amount of starch glue is 0.1 5% ~ O. At 3%, do not overdosed sodium benzoate. The more the preservative is added, the better the antiseptic effect will be. Sodium benzoate is a safe and non-toxic antiseptic. Some foods also have a small amount of anti-corrosion effect. The mechanism of antisepsis is different from that of antiseptics. Therefore, excessive addition of sodium benzoate can not increase its antiseptic effect.
5 Storage and transportation of plant starch Storage temperature of starch in plants is too high to promote the spoilage and drying of the glue. Storage temperature should be 20 °C to 25 °C. It should be placed in a cool, ventilated place and avoid sunlight. Direct irradiation increases the temperature, and it is better to place it in a place where the ambient temperature is stable. The packaging container of vegetable starch glue requires airtight sealing and prevents the container from leaking during the handling process. The starch glue covers the surface of the starch glue with a piece of paper and plastic in the container to prevent it from contacting with the air. The long-term sealing of storage equipment will surely cause the surface of the starch glue to spoil.
6 Others In order to prevent rat bites and insects, some manufacturers often add pesticides, 666 powder and other poisonous and harmful chemicals to the vegetable starch glue. This is a very unscientific practice, harmful to the human body and dangerous.