Application of Kinds of Adhesives in Packaging Industry (I)

Introduction

The use of adhesives in the packaging industry has been around for a hundred years. It is a kind of material that firmly binds various solid materials together by the interface function. It is also called adhesive or glue, which is simply called "glue". In the packaging industry, there are many kinds of adhesive materials. Different types of materials, such as metals, wood, plastics, paper, and composite films, have different physical and chemical properties, which have a great influence on the bonding strength. Therefore, according to different materials, choose different adhesives and bonding processes. With the development of the packaging industry, the consumption of adhesives has remained at a high level, and the global packaging industry accounts for about 35% of the total amount of adhesives. Based on this, it is speculated that the packaging industry may be the largest consumer market for adhesives.

A foam alkali adhesive

The chemical name of scolated alkali is sodium silicate, which is a colorless crystal or a white powder. It is made of quartz sand and sodium carbonate. It is soluble in water and is alkaline. The transparent syrupy solution is called "water glass". The viscosity of the water glass solution increases dramatically after gradually losing water, and later causes hardening, so it can be used as an adhesive. Paosite is an early use adhesive in the packaging industry. Mainly used in the carton industry.

1.1 The advantages and disadvantages of scoplasm adhesive

Due to the simple operation and production process, the fibrous base adhesive has a faster drying speed (relative to the starch adhesive). It has been widely used by the industry for many years. However, it also has the disadvantages of wet deliquescence, slow adhesion, increased carton, etc. It is not suitable for the needs of rapid packaging and fine packaging; moreover, it contains high alkali content, is easy to efflorescence, has strong corrosiveness to paper, and pollutes the environment. . According to reports from some manufacturers, because the pH value of the paper is 7 and it is a neutral substance, bupropenic alkali is weakly alkaline. Using it as a binder for high-grade wine boxes will make the paper slightly alkaline. Alkaline substances will have a certain influence on galvanized aluminum foils, inks, gold powders, and silver powders. They will have a certain chemical reaction, and are particularly prone to chemical reactions with the metal powders in the galvanized aluminum foil. This will make the original aluminum foil with a bright color and color lose its originality. Some of the luster, the color completely turned pale yellow, thus affecting the aesthetics of the packaging carton. Over time, it can also tarnish the ink layer on prints. Therefore, in the carton, carton paste box is best not to use as the adhesive scouring alkali, because it will have a great impact on the aesthetics of the package. As for what kind of adhesive, it must first analyze the physical and chemical properties of the adhesive. And its acid, alkali on paper, ink, electrochemical foil, gold powder, silver powder and coating and many other aspects of the impact.

1.2 The development trend of silicate

At present, babuloic acid has been listed as an internationally prohibited adhesive for use in cartons and cartons. However, adhesives made from silicates and other substances are a new trend. For example, the use of battoin and various organic glues (starch, dextrin, etc.) to form a high-quality mixed ray can increase its viscosity, and at the same time overcome the disadvantages of slow adhesion of silicates. Currently. It has also been reported that the use of scouring alkali to modify the polyvinyl alcohol adhesive to obtain excellent adhesive properties.

2 Use of starch adhesives

Due to its high strength, light weight, no corrosion, no pollution, and low cost, starch adhesives are widely used in corrugated paperboard, carton production, and automatic labeling to replace it. Years of brewing alkali. Since the 1970s, China has successively developed starch adhesives for gelatinization of starch, oxidized starch, compound starch, esterified starch, and adhesive starch, among which oxidized starch adhesives are most widely used.

2.1 Advantages and disadvantages of starch adhesives and comparison with silicates

Relevant authorities of the State have long prescribe (GB-5034-85) the use of starch adhesives for processing corrugated cardboard or use other adhesives with the same adhesive effect. Sodium silicate must not be used. Starch adhesives have advantages such as greater bond strength, lighter weight, no corrosion, low cost, and ease of manufacturing as compared to scorodrene. Currently, from the use of adhesives in the packaging industry, starch adhesives account for a significant portion of the binding of paper packaging materials and paper containers. More than 10 years have passed. Until now, mainly in China's carton packaging industry, battoin has been used. The use of starch adhesives is rare. The main reason is that the starch drying rate is too slow. This is because starch is a natural polymer with glucose as the structural unit, which consists of amylose and amylopectin. Amylose is essentially a linear polymer. A large number of hydroxyl groups make the polymer highly hydrophilic.

In foreign countries, the starch adhesives for corrugated boxes are mainly used on the forming machines and are equipped with automatic drying devices, so they do not have the problem of slow drying speed. Because our country's packaging is still relatively backward, there are few manufacturers that use the forming machine to dry the automatic lines in the carton production. Moreover, China's carton factory is mainly a small township enterprise, and there are certain difficulties in establishing a drying automatic line, which seriously affects the general promotion of starch adhesives. Therefore, at present there are still a large number of corrugated cartons production plants, especially some stand-alone machines, and small, hand-carton cartons are still continuing to use traditional scoroders as adhesives. The preparation of starch glue is generally made by heat, the production cost is high, and the shelf life is short. In addition, the more representative is the cold starch glue, first made by the adhesive plant powder packaging products, and then by the carton factory with the current use. The principle is to oxidize the starch. After centrifugation, drying, and with fillers; this process has a low production cost, but it is inconvenient to use, and the formulated starch glue needs to be used up on the same day. Can not save, the quality of the glue is not stable. Therefore, so far, the domestic general small and medium-sized carton factory still use babbitine.

(to be continued)