Water-based adhesives use high-molecular polymers, water-soluble resins, etc. as the main raw materials, water as the solvent, low odor, environmental protection and non-toxic. With the continuous improvement of people's awareness of environmental protection, water-based adhesives have become the mainstream of the market in recent years. In practical applications, some packaging and printing companies lack sufficient knowledge of water-based adhesives, which causes some quality problems. Among them, the problem of "difficult bonding" of water-based adhesives is one of the technical bottlenecks that plague many packaging and printing companies. In order to let more packaging and printing companies understand water-based adhesives, the author will elaborate on the characteristics and selection of water-based adhesives, hoping to give the industry some inspiration.

Features of water-based adhesives

1. Applicable substrate

Any kind of adhesive is not omnipotent, a kind of adhesive is only suitable for bonding a certain or a certain type of material. At present, water-based adhesives are mainly used for the bonding between polishing paper/paper, PET/~, BOPP/paper, PVC/paper, plastic/plastic and other substrates.

2. Inherent characteristics

Each water-based adhesive has its "intrinsic characteristics". The inherent characteristics of water-based adhesives mainly include appearance (product appearance and film appearance), solid content, density, pH value, solvent composition 56 2012/10 printing technology. Packaging decoration ratio, opening time, high/low temperature resistance, initial Viscosity, curing viscosity, etc. The bonding methods of water-based adhesives are generally divided into three types: machine bonding, hand bonding, machine bonding and hand bonding. Different bonding methods correspond to different inherent characteristics. For example, when using machine bonding, the water-based adhesive is required to have a short open time; when using hand bonding, the water-based adhesive is required to have a long open time; when the film is bonded, the film is required to be flexible and have a high curing viscosity. In terms of high/low temperature resistance, the water-based adhesive is required to be baked at 60~C for 72 hours, and then frozen at 1 10°C for 72 hours, the bonding strength remains unchanged, and there is no degumming, brittle film and other phenomena.

3. Advantages and disadvantages

The advantages of 　　 water-based adhesives are: water-based adhesives belong to an emulsified system, so their viscosity does not change with the change of polymer molecular weight, and it is environmentally friendly, non-flammable, and easy to clean. The disadvantage is that the water-based adhesives are added with various emulsifiers, stabilizers, pH regulators, and cold-resistant antifreeze agents, which will cause certain pollution to the environment. In addition, water-based adhesives evaporate slowly, have poor initial viscosity, are expensive, have poor wettability to plastic films, and are easy to rust equipment.

The choice of water-based adhesive

1. Application indicators

Some packaging and printing companies report: Some water-based adhesives will be degummed soon after being glued; the viscosity is not stable, sometimes the bonding is firm, sometimes it is not bonding; the application is good in hot weather, but in the weather It can't be applied under cold conditions... In fact, this is due to insufficient understanding of the application indicators of water-based adhesives. Different types of water-based adhesives have different preparation methods and production processes, so their chemical and physical properties are also different, that is, different application indicators. The author believes that the more important application indicators of water-based adhesives in the packaging and printing industry mainly include four aspects: bonding strength, high/low temperature resistance, moisture resistance and stickiness. Defects such as weak bonding, degumming, and brittle film that often occur in practical applications are basically caused by the failure of the above four application indicators.

2. Cost-effective

When choosing water-based adhesives, the principle of "quality first, price second" should be followed. However, some packaging and printing companies have a one-sided view, misunderstanding that the higher the price of water-based adhesives, the better the quality; on the contrary, the worse the quality. In fact, this is not absolute. The author believes that when choosing a water-based adhesive, you must first understand the characteristics of the processed product and choose an adhesive with a higher cost performance. This is a reasonable way to buy.