The corrugated board production process is ever-changing, and the situation is changing rapidly. Carton factories often need to adjust the adhesive formulation and improve the adhesion of the board. This requires rubber-making personnel to have a very clear understanding of the characteristics and functions of the ingredients in the ingredients. Below, the “Packaging Zone” micro-editor will explain to you the characteristics and functions of various ingredients in the tile line starch adhesive in detail.
First of all, water is mainly used as a carrier for biochemical reactions, and plays the role of dilution, penetration, uniformity and diffusion. The adhesive is transferred to the corrugated paper to be processed through the carrier, and then penetrates into the corrugated paper. Second, water is necessary during the expansion of the starch granules that give the adhesive stickiness. The water quality required for the preparation of the adhesive is tap water, and well water or ground water cannot be used.
Starch is the main body of biochemical reactions. Starch is a natural carbohydrate extracted from chlorophyll-containing plants. Many industries prefer to use starch as a binder because the cost of starch is relatively low, and it is biodegradable and can be extracted from renewable raw materials.
After corn starch is dried, the weight composition of various components is roughly as follows:
Starch and carbohydrates-80%
The composition of other starches is also roughly the same. The starch raw materials generally contain about 80% starch, and impurities other than starch are basically eliminated in the starch manufacturing process. The pure starch content after starch drying should be more than 99%.
3. Sodium hydroxide
Sodium hydroxide (NaOH, also known as caustic soda) is an oxidant in the biochemical reaction. It mainly acts as a gelatinizer in the adhesive. It also has the function of infiltrating and softening the cardboard fibers, and can improve the penetration of the adhesive. Too much amount of caustic soda will reduce the gelatinization temperature of the adhesive and increase the PH value of the adhesive; too little amount of caustic soda will make the adhesive gelatinization temperature higher, starch cannot be completely gelatinized, and poor penetration , Corrugated board has higher moisture content and lower physical index. In the SteinHall glue making process, caustic soda is used to gelatinize the preliminary starch-loaded starch to enhance its viscosity. In the one-bucket glue making process, adding caustic soda when the starch swells can also enhance the viscosity.
The scientific name is disodium tetraborate decahydrate (Na2B4O7*10H2O), which is mainly used for cross-linking, complexing and thickening in adhesives. Excessive amount of borax will cause the adhesive to have too strong cohesive force, and it will become rubbery after coagulation, which will lose its adhesive effect, resulting in delamination of the cardboard; Increase the moisture content of the cardboard.
In addition, borax interacts with cooked starch, which can change the viscosity of the adhesive and affect its fluidity and permeability. When used with caustic soda, it can also improve the initial bonding strength and shear stability. The amount of borax is adjusted according to the corrugated paper and facial paper used in the production of corrugated cardboard. If the paper quality is poor, the amount of borax should be appropriately increased; if the paper quality is good, especially imported sizing paper, the amount of borax can be omitted or appropriately reduced.
There are mainly two kinds of cross-linking agent (or bridging agent) and stabilizer (terminator). The use of additives can effectively improve the adhesive performance and moisture resistance of corrugated cardboard, and can make the adhesive not easy to be emulsified after curing, so as to improve the corrugated cardboard’s edge compressive strength, flat compressive strength, and burst strength. Under the premise, the basis weight of the base paper can be appropriately reduced; the use of additives can effectively reduce the gelatinization temperature of the adhesive, increase the speed, and improve the flatness of the corrugated board; the use of additives can appropriately reduce the amount of starch under the premise of ensuring the bonding effect.
In addition, there are preservatives and water resistance enhancers. Cooked starch paste and expanded starch molecules are prone to bacterial degradation. Preservatives help to avoid contamination and prevent the paste from growing bacteria and causing a decrease in viscosity. Preservatives such as formaldehyde are traditionally used, but in recent years they have been gradually replaced by more environmentally friendly and safer products.