With the development of the market economy, the demand for flexible packaging in various industries is also rising year by year. The development of flexible packaging materials and processing technology continue to improve, flexible packaging in many areas is playing an increasingly important role, so what are the composite ways of flexible packaging? This article briefly describes five composite methods of flexible packaging, and the content is for the reference of friends in the adhesive supply chain:

Flexible packaging composite

The "composite" in the flexible packaging industry is actually the meaning of "lamination", which is to make the film of different properties stick together in a certain way, and then seal it to protect the contents. Flexible packaging composite processing methods mainly include dry composite, wet composite, extrusion composite, co-extrusion composite and so on. Each compound way has advantages and disadvantages, comprehensive understanding to avoid bias!

01 Dry compound

Among the various processing technologies of composite film, dry composite is the most traditional and widely used composite technology in China, which is suitable for complex varieties, small batches and a wide variety of packaging products. Widely used in food, medicine, cosmetics, daily necessities, light industrial products, chemicals, electronic products and other packaging.

Dry composite is coated with a coating device (generally using gravure cable roller coating) on the plastic film coated with a layer of solvent-based adhesive, the solvent is removed by the recoating machine and dried, in the state of hot pressing and other substrate composite, such as film, aluminum foil adhesion into a composite film, the process is as shown in the following figure, because it is in the adhesive "dry" state (solvent-free state) composite. Hence the name dry compound.

Dry composite is suitable for a variety of composite film substrate and film and aluminum foil, paper between the composite, a wide range of applications, excellent corrosion resistance to chemical media, such as food with alkali, acid, spicy, grease and other ingredients, cosmetics with water, flavor, emulsifier and other ingredients, chemicals with solvents, pesticides and other ingredients, widely used in the contents of the harsh conditions of packaging.

With high composite strength, good stability and high product transparency, it can produce both high and mid-range composite films, and can also produce frozen, fresh-keeping or high-temperature sterilization composite films. Easy to use and flexible, simple operation, suitable for multi-variety, batch less production.

However, the dry compound itself also has defects of poor safety and hygiene, environmental pollution and higher cost, and the development of alcohol-soluble and water-soluble adhesives has slowed down the pressure of solvent-based adhesives in terms of safety and hygiene, environmental pollution and cost to a certain extent.

Dry composite still occupies a large proportion in the processing methods of composite materials, and at this stage it is still a composite processing method that can not be replaced by extrusion composite, wet composite and solvent-free composite.

02 Wet compound

Wet composite is a composite substrate (plastic film, aluminum foil) surface coated with a layer of adhesive, in the adhesive is not dry, through the press roller and other materials (paper, cellophane) composite, and then through the hot drying channel to become a composite film.

Wet composite is characterized by simple process operation, less adhesive dosage, low cost and fast composite speed. The adhesives used in wet compounding method mainly include polyvinyl alcohol, sodium silicate, starch, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyacrylate, natural resin, etc.

The working principle of the wet composite is basically similar to that of the dry composite, the difference is that the dry composite is to heat the film coated with adhesive through the drying channel, and then hot press bond with the composite material after the organic solvent in the adhesive evaporates; The wet compounding method is to directly compound the adhesive coated film with the composite material, and then enter the drying channel for drying.

When wet composite is used, at least one of the two substrates is a porous material (such as paper or cardboard) so that the diluent contained in the adhesive evaporates when drying.

Therefore, wet composite is widely used in the composite of paper/fiber, paper/paper, paper/cardboard, paper/aluminum foil and other materials.

03 Extrusion composite

Extrusion composite is to melt the thermoplastic material such as pe or pp in the extruder and squeeze it into the flat die, and form a sheet film after flowing out immediately with another or two films through the cooling roll and composite roll composite together. Compared with other composite methods, extrusion composite has the advantages of low equipment cost, less investment, clean production environment, no residual solvent, high production efficiency and simple operation. Extrusion composite plays a very important role in the composite processing of plastics.

Extruded coated film

Extrusion coating is a method of melting thermoplastic such as polyethylene from the flat head, pressing it into another substrate between two rollers in close contact, and then making a composite film after cooling.

Unwinding substrate is generally already printed PET, BOPP, paper and other materials, such as instant noodle packaging bags is a typical example of extrusion coating production, its structure: BOPP printing film/LDPE(or PP).

Extruded composite film

Extrusion composite is the extruded resin sandwiched in the middle of the two substrates, which plays the role of an adhesive that combines the two substrates together, and is also a composite layer.

The first substrate is often PET, BOPP, PA, paper and other materials, the second substrate is generally LDPE, CPP, aluminum foil, aluminum plating film and other materials, extrusion resin is generally PE, PP, EVA, EAA and other resins. General ordinary washing powder packaging film can be combined with this method, the structure is as follows: BOPP printing film/extrusion resin/PE film.

04 Solvent-free composite

The adhesive used in solvent-free composite has attracted much attention because it does not contain organic solvents. In developed countries such as Europe and the United States, solvent-free composite has become the main method for the production of flexible packaging composite materials.

It is a composite method of coating the substrate with solvent-free adhesive and directly bonding it with the second substrate. Although the adhesive is used as the dry composite, the adhesive does not contain organic solvent and does not need drying device. Due to its superior environmental friendliness, product performance can also be achieved with dry composite, is the future direction of development.

05 Co-extruded composite

Co-extruded composite is a molding method in which two or more different plastics are fused and plasticized into a pair of mouth dies through two or more extruders, or the plastics supplied by various extruders are combined into an entrance die through a distributor to prepare composite films.

The different plastics mentioned here can be different kinds of plastics, or the same kind but different grades of plastics, or the same grade but different formulations of plastics. The cost of co-extrusion composite is low, which is 20%-30% lower than that of dry composite, and the adhesive or anchor coating (AC agent) is not used in the co-extrusion composite process, so the hygiene is good and there is no environmental pollution problem.

However, due to the obvious limitations of the material, the composite film produced by the co-extrusion composite process is limited to various thermoplastics, and if the composite material containing aluminum foil, paper, etc., can not be produced by co-extrusion composite.

In addition, it can not be printed between composite films, and when the film needs to be printed, the pattern, text, etc., can only be printed to the surface of the composite film.

Sinograce Chemical has water-based composite adhesives for dry composite and wet composite, welcome to buy, and exchange adhesive technology.