Packaging adhesive (top)

As the outerwear of products, packaging has become an important factor influencing the competitiveness of products. People have higher and higher requirements for it. They require elegant packaging, stimulating and attracting consumers, but also require simple technology, low cost, and durability. It even requires special functions such as anti-counterfeiting and anti-theft. With China's accession to the WTO, China's more goods will go to the world, so the traditional relatively backward packaging industry will face a severe test, and packaging will also be one of the breakthroughs in changing the price of domestic goods in the international market. This will inevitably stimulate the rapid development of the domestic packaging industry to some extent

The relationship between packaging and adhesive materials is very close. The development of bonding technology has enabled many new materials and technologies to be used in the packaging industry, creating conditions for packaging. It can be said that without adhesives, there are no bright and colorful modern commodity packaging. Packaging is also an important consumer sector for adhesive materials. According to statistics, in 1989, the world's total production value of adhesive materials was approximately US$13 billion, of which packaging consumption accounted for US$3.5 billion. In the United States, developed countries such as the United States accounted for more than 20% of total consumption of packaging adhesive materials in 1990, and their sales growth rate is estimated. It will remain at about 9%, exceeding its growth rate in the construction and automotive industries.

The main uses of adhesives in the packaging industry include: preparation, forming and sealing of corrugated paperboard, cartons and cartons; roll-tube bonding and capping of mandrels, paper cans, paper tubes, and sticking of bottles, cans and cans Standards and seals, composites of paper and paperboard, polymer films, metal foils; laminating and sealing of flexible packaging plastic bags, peelable protective films; pressure-sensitive packaging and merchandising strapping. Even for adhesives of the same type, the types thereof are numerous. Which type of adhesive is selected in actual production depends on the production conditions, the production cost, the use of the substrate, and the end use. In view of space limitations, this article is divided into three parts according to the use of paper packaging, plastic flexible packaging, label nameplate glue, etc. to give a brief introduction:

First, paper packaging

There are two types of paper packaging, one is pure paper packaging, such as corrugated paper boxes, paper drums, paper boxes, paper bags, it is the most use of the most widely used packaging. The other category is paper-based composite packaging, such as paper/plastic composite bags (bags), paper/aluminum foil composite boxes (bags), and paper/wood composite material boxes (boxes).

The first type of adhesive used for pure paper packaging is based on natural starch glue. Starch adhesives, as universal adhesives, have unique advantages in terms of raw material source, manufacturing process, cost, environmental hygiene and use. Compared with silicate (also known as water glass), starch glue has the characteristics of high adhesive strength, light weight, no corrosion, no pollution, high strength, and good toughness. In foreign countries in the early 1950s, starch glue was used instead of babbitine, which was used in the manufacture of cartons and cardboard. China has also banned the use of water glass in the preparation of cartons. However, starch glue has one disadvantage: its made of starch glue has a water content of more than 70%, and it is slow to dry. At the same time, the water in the adhesive penetrates into the paper during the drying process, which reduces the initial tack force and prolongs the production cycle. If it cannot be dried in time, it will cause running edge, squeaking, slitting, and the like. The phenomenon has limited its application.

Starch gum production methods can be divided into three categories: Stein-Hall method, oxidation method and biological fermentation method. The Stein-Hall method is a thermal gelatinization method. It heats at the bonding site and gelatinizes the starch to form a bond. The bonding speed is fast and the energy consumption is high, and it needs to be used on special equipment. Oxidation is divided into thermal oxidation and chemical oxidation. It breaks starch molecules into fragments through oxidizing agent or heating, then pastes with caustic soda and then is complexed with borax. This method is simple in production process, low in cost, and is now commonly used. The bio-fermentation method utilizes enzymatic hydrolysis of starch by enzymes to produce high-solid-content starch glue with a neutral pH, making the starch glue significantly improved in initial tack, tack retention, drying speed, and shelf life. This technology is also improving the grade of starch glue.

In addition to starch gums, synthetic polymer emulsions are also used in many applications such as corrugated paper, enamel tile, and matt. The synthetic properties of synthetic polymer emulsions are ideal, especially the weather resistance, water resistance, and cold resistance. , Toughness, and initial tack are all unmatched by starch glue. Although the cost of synthetic polymer emulsions is high, its usage still shows an encouraging trend. Synthetic polymer emulsions used in this category include polyvinyl acetate emulsion (PVAC) and its modified products.

The second type of paper-based composite packaging is a relatively high-end packaging form developed on the basis of the first type. Compared with pure paper packaging, the composite packaging is not only luxurious in appearance but also full of magnificent styles. New packaging features such as moisture and stain resistance, tear strength and crush resistance have all been greatly improved. Because of this, the scope of application and the amount of use of such packaging are developing at an alarming rate. Composite rubber is a key material for composite packaging processes. The traditional compound rubber is a solvent type. It dissolves SBS, rosin, terpene and other high-molecular substances and additives in toluene and other organic toxic solvents to make a solution of about 40%. It is diluted with solvent before use and becomes low. The solid content was coated on a biaxially oriented polypropylene (BOPP) and oven-dried. Then the film and paper were pressed together by hot rollers. This process discharges a large amount of toxic flammable and explosive solvents into the air, which seriously pollutes the environment, impairs the health of the operating workers, and causes serious fire hazards. In addition, the use of a large number of auxiliaries such as rosin, composite rubber aging resistance is also very poor, the composite product is easy to yellowing, short life, energy consumption, high cost, although this process is still dominant in the market, but Its tendency to be replaced by environmentally friendly adhesives has been widely accepted and respected.

The domestic environment-friendly compound adhesive has entered the mature stage of technology and is in the stage of promotion and application. In the market, the main types of environmental protection compound glues are divided into two categories. One is compound adhesives modified with ethylene-vinyl acetate emulsion (VAE emulsion) as the basic material. This kind of product has the advantages of good cover powder capability and good processability, but it also has the disadvantages of small composite strength, difficult use in winter, large amount of glue consumption, and high cost, and thus it is gradually withdrawing from the compound rubber market. The second category is acrylate-based emulsion-modified adhesives. As long as the molecular structure is well-designed, these products can overcome all of their shortcomings while having the advantages of VAE emulsion-modified adhesives. Among them, Sichuan Vision Industrial Co., Ltd. is a representative of the Fasette series rubber. The emulsion has similar flowability and solid content as the VAE emulsion, so that the powder coating ability and process adaptability are excellent, and the weather resistance, temperature adaptability, and peeling fastness are all excellent and the cost is greatly reduced. Not only composite paper / BOPP, but also composite paper / PET, paper / PVC, paper / aluminum foil, paper / paper, and has formed a large-scale production and sales. It can be predicted that through the joint efforts of people in the industry, the environmental protection of rubber compound fully replaces solvent glue is just around the corner.