Production and materials of the hottest plastic fl

the production and materials of plastic flexible packaging

with the social demand for plastic flexible packaging increasing year by year, plastic packaging is covering the market according to its inherent characteristics of bright colors, novel patterns and convenient use. However, because most small and medium-sized packaging color printing enterprises lack technical data for manufacturing and material selection, and professional knowledge has not been popularized, the packaged goods have deteriorated, the losses are huge, and the packaging business is difficult to expand. I will integrate theory into practice and give some suggestions for many colleagues in the field of flexible packaging

generally, printing methods include embossing, gravure, lithography, silk screen printing, etc. Plastic printing is gravure printing. The gravure printing machine often mentioned refers to the unit type (or arrangement type) gravure printing machine

1. Printing machine

the printing speed of the plastic printing unit is determined by the length of the paper walking distance between the printing color groups of the printing machine and the effect of the drying box. The longer the distance between colors and the better the effect of the oven, the faster the printing speed will be. On the contrary, the printing speed will not go up. The accuracy of the printing machine, in addition to requiring the operation of all parts before and after the printing machine to be the same as that of the project, which adopts the technical step of HPO plus production of caprolactam by Royal DSM group of the Netherlands, also requires that the tension control system of all parts be stable, only the tension control design is reasonable and the feeding is stable, The reeling is stable, and the printing will not run off the plate, so as to maintain the accuracy of chromatic registration

2. Printing plate

gravure plate is made of corrosion (manual plate) and electric engraving (electric engraving plate). At present, the price of manual plate is low, but the printing effect is still good, especially the layered plate. In practice, it is found that electric engraving requires high ink. The quality of printing plate production directly affects the printing effect

3. Ink

plastic gravure ink, including solvent ink and water-based ink. Solvent based inks are divided into surface printing inks and internal printing inks (composite inks)

surface printing plastic gravure printing ink: the surface is smooth and shiny, which is more wear-resistant and smelly than internal printing ink. Single component glue should be used for lamination processing, which has poor adhesion with two-component glue. Note that the glue amount should not be too large. Table printing ink is divided into ordinary ink, water-resistant ink (beverage packaging ink), label ink (calendar ink), transparent ink, etc. Water resistant ink is mainly used for printing milk packaging, beverage packaging and frozen food packaging products, and has obtained the approval of a well-known lighting lamp customer sample downstream. The label ink is very smooth, anti adhesion, scratch resistant, and is the best ink for printing all kinds of labels. Transparent ink is a special ink for printing aluminum foil and aluminum foil

inner printing ink (composite ink) is characterized by bright color, tasteless printing, high peel strength, but the conjunctiva is relatively soft and not wear-resistant. Judging from its Matt printing, it is conducive to lamination processing. If gluing dry compounding is adopted, two-component glue should be used. One is to increase the composite firmness, and the other is to have a small smell. However, when one component glue is used for compounding, the ink on the printed matter is often dissolved or the compounded finished product will bring the harmful smell of glue, and the compounding firmness is poor (note that alcohol solvents are not allowed to be added). In addition, there is common compound ink in the internal printing ink, which is the ink printing of OPP film (polypropylene ink). Polyester ink should be used for printing PET film (polyester film), and its printing pattern is more firm, and there will be no adhesion. In short, the principle of plastic gravure ink is to use what type of special ink on what film

water based inks are usually used for printing paper products, including paper plastic composite products. Its characteristic is that it can meet the ink absorption of paper printing and make the printing full. What's more difficult is that its solvent is water and ethanol, which has little environmental pollution and is known as a green ink for environmental protection

4. Compounding

compounding of plastic flexible packaging, laminating film extrusion compounding, dry gluing compounding and glueless hot pressing compounding, etc. Extrusion compounding refers to extruding PE or PP material into a film after hot melting, and hot pressing compounding on the printed film to form a composite finished product, which is characterized by low cost and reduced glue pollution. However, it is better to choose the type of extrusion material and control the extrusion temperature, and add a small amount of glue or AC agent as coupling agent between film-forming

the length of drying channel, heating mode, gluing mode, gluing amount control, material tension control, hot drum temperature control and whether there is a cooling and shaping device of the dry gluing and laminating machine constitute its price and grade. In the process of gluing and compounding, first of all, users should understand that if gluing is to be uniform, the glue must be diluted, and if the viscosity of the glue is to be restored, the solvent on the coating must be volatilized (that is, the concentration process), so the gluing amount on the composite is the key to compounding. Special attention should be paid to reducing the amount of glue when compounding. Therefore, it is recommended not to use it in food packaging

since one component glue is used with surface printing ink and printing materials, the smell is difficult to eliminate, so it is recommended not to use it in food packaging, and special attention should be paid to reducing the amount of glue when compounding

if two-component glue is used for lamination, in addition to the proportion of glue according to the technical data provided by the manufacturer, attention should also be paid to the content of curing agent, and the amount of glue should be reasonably controlled to reduce the generation of odor and glue spots on the laminating products

in addition, if PE film is to be used as laminating lining, special attention should be paid to the surface tension of PE film. Generally, it should be above 45-52 dyne to ensure the firmness after laminating (it is recommended to install an electric spark processor on the laminating machine)

5. Plastic film

due to the different requirements of the packages, different packages require different plastic films. The properties and uses of the most commonly used plastic films are briefly introduced below

pe film is also known as polyethylene film, which is widely used. It is characterized by low cost, good water resistance, but poor gas resistance. Low pressure polyethylene has small extensibility and high tensile strength. It can make the packaging bag very thin, but its heat sealing performance is poor, so it is not suitable to be used as composite film. High pressure polyethylene film has high extensibility and good impact resistance, but it is not suitable to be used as a composite lining film for fried foods and vacuum and cooking bags

pp film is also called polypropylene film. It has high transparency, high strength, good gas and water resistance, and only poor oxygen resistance. Vacuum, cooking, medicine, beverage and other packaging should not use this film as fabric. CPP unidirectional stretch polypropylene film and heat sealable unidirectional stretch polypropylene film are the best and most commonly used composite linings for vacuum packaging or cooking packaging

pet, also known as polyester film, has high tensile strength, poor impact resistance, high transparency, good oxygen and gas resistance, but it is not resistant to sunlight and has small water vapor permeability. It can be used as the fabric and substrate of ordinary vacuum bags, medicine bags and aluminized bags. Not suitable for cooking bags

pa film, commonly known as nylon film, is currently used as the fabric of cooking packaging bags. Its cost is high, and generally vacuum bags are not used

other films, such as PE fresh-keeping film for vegetables, fruits and meat packaging, water-soluble PVA film, PVDC high resistance diaphragm, PVC, PP, PE heat shrinkable film

producers and Chinese dream applicators who propose to realize the "great rejuvenation of the Chinese nation" should choose the necessary fabrics and linings for packaging according to the inherent characteristics of various film materials, and strive to produce affordable, high-quality and low-cost qualified packaging bags

6. Appendix common diluent ratio of plastic gravure ink for reference:

I. ratio of diluent used in plastic gravure ink for internal printing:

fast drying solvent: ethyl acetate 20%, toluene 80%

medium dry solvent: butyl acetate 20%, toluene 80 or 100%

slow drying solvent: butyl acetate 20%, xylene 80%

(Note: alcohol solvent cannot be added)

II Proportion of diluent used in surface printing plastic gravure ink:

fast drying solvent: ethyl acetate 20%, toluene 80%, isopropanol 40%

medium dry solvent: ethyl acetate 25%, toluene 50%, isopropanol 45%

slow drying solvent: xylene 50%, isopropanol 50%

ultra slow drying solvent: xylene 50%, isopropyl alcohol 50%, n-butanol 3%