Dry and wet film comparison

According to the different materials and equipments, the coating film can be divided into a coating type coating and a precoating type coating. Actually, two kinds of laminating technologies are currently popular on the market: solvent-free hot-melt adhesive pre-coating film dry-type composite technology and emulsion-type adhesive that is adhesive-coated wet composite technology. They are representative processes of dry film coating technology and wet film coating technology. Below will be a general introduction and comparison of the two processes.

1, the process of two composite processes

Solvent-free hot melt adhesive pre-film dry composite process is as follows:

First, a hot-melt adhesive pre-coating film is used, and then the hot-melt adhesive pre-coating film is leveled. At this time, the printed matter is conveyed and the film is subjected to hot-pressing, and the product is cut after the completion of pressing.

The emulsion adhesive is the adhesive wet compound process flow as follows: First adjust the BOPP film to achieve the tension balance, use the emulsion adhesive and thinner to adjust, and apply the obtained adhesive to the BOPP film. When the printed matter is conveyed, the film is hot pressed together with the film, and the product is cut after curing.

2, the materials used in the two composite processes

Solvent-free hot-melt adhesive pre-film dry-type composite process using the main material for the hot sol, which is EVA (or EEA, EAA) resin, tackifying resin (such as polymer rosin, hydrogenated rosin, petroleum resin, etc.) and modifiers (Microcrystalline waxes, antioxidants, plasticizers, etc.) Melt produced by melting at 150 to 200 degrees.

Because the hot sol contains no solvent, the main ingredient EVA is non-toxic and odorless. It is harmless to the operator and the environment, and it is convenient for storage and transportation. Its 100% solids content can all be used for compounding. High bonding strength and good transparency. Heating is sticky and room temperature curing, suitable for automated continuous production, high efficiency. And EVA adhesion is good, can be used for paper, plastic, aluminum foil, fabric and other substrate adhesion. However, it is not high in heat resistance and should not be used as a material that is used under conditions of high temperature (100 degrees) adhesion. Because of the above-mentioned characteristics of the hot melt, it only possesses the properties that other adhesives do not have that can be adhered only by heat, can be peeled off under the same heat, and the disintegration characteristics can be recovered, so that the waste compound can be recycled.

Emulsion adhesives are the main materials used in the adhesive wet composite process. They are emulsion adhesives. They are monomers (such as acrylate, vinyl acetate, etc.), initiators (such as potassium persulfate) and emulsifiers ( For example, OP-10, etc.) Dispersion-dispersed polymerization An emulsion formed in a solvent such as toluene (or xylene, ammonia) or the like.

The adhesive has a solid content of 50-60%, which is half that of the hot melt. When diluted with water, there will be a brief increase in viscosity. When the acid, salt, solvent, colloid with opposite charge, heat, cold junction, pressure, water evaporation, current and other conditions come into contact, there will be flocculation phenomenon, destroy the stability of the quality.

3, two kinds of equipment of the composite process

Solvent-free hot-melt adhesive pre-film dry-type composite is a hot-pressing process, as long as it has a hot-press structure covered (composite) machinery can be used.

2. Emulsion adhesives, ie, adhesives, wet compounding are the compounding and curing process. A ready-to-apply water-based laminator is required.

A schematic diagram of the equipment used for the two composites is shown in Figure 1 and Figure 2.

Figure 1: Schematic diagram of dry composite equipment

Figure 2: Schematic diagram of wet composite equipment

4, the description of two kinds of compound craft

Solvent-free hot melt adhesive pre-film dry composite process. The complex production process has been simplified to a single hot press. As long as the operator gives a reasonable heat. To ensure that the hot melt fully melted and composite carrier. The printing ink layer can be easily compounded by misalignment and misalignment.

Milking-type adhesive is a glue wet composite process. Is to replace the solvent-based adhesive that has been heavily contaminated in the wet adhesive compounding process into an emulsion adhesive. Due to the inability to ensure the volatilization of organic solvents in the process of adhesive coating production, the solvent content is lower. Therefore, the drying part in the wet glue compounding equipment is dispensed with. The solvent is absorbed directly from the substrate and then slowly volatilized. Become a true "wet", "cold" lamination process. This makes the core technology of the emulsion cavity adhesive that is glue coated wet composite technology to perform effective control of coating, cold pressing and drying.

5, the development of two composite processes

With the advent of the global digital economy, the development of composite processes must follow the laws of pollution-free, high-efficiency, high-quality, high-efficiency, easy-to-operate, and recyclable economic sustainable development, and use advanced science and technology to continuously improve itself. In order to be competitive in the international market.

Due to the use of environmentally friendly BOPP film as a composite material, the dry film coating process has high coating quality, no pollution, simple device construction, easy operation, and high production efficiency. The waste composite product can be processed in 60oC slurry water. The advantages of separating and disassembling the sorting and recycling, and adapting to the requirements of exquisite, green and aseptic processing after printing in the 21st century are in line with the IS014000 series of international standards for environmental management and have broad prospects for development.

In addition to preventing and improving the adhesion phenomenon of the equipment in operation, the wet coating technique is more important to continue to improve the emulsion adhesive so that it can truly achieve non-toxic, odorless, non-polluting, fast drying, Strong adhesion, high toughness, strong adhesion, good weather resistance and recyclability.

Source: Wins