Production and materials of the hottest plastic fl

The production and materials of plastic flexible packaging

with the increasing demand for plastic flexible packaging in society year by year, plastic packaging is covering the market according to its inherent demand and shortage of high-end professional talents, which will be more severe with the 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 become southern, with huge losses, 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. The printing speed of the printing machine

Plastic printing unit is determined by the 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 is. On the contrary, the printing speed will not go up

in addition to the synchronous operation of the front and rear parts of the printing machine, the accuracy of the overprint of the printing machine also requires that the tension control system of each part be stable. Only when the tension control design is reasonable, the feeding is stable, and the winding is stable, the printing will not run, and the accuracy of the overprint can be maintained

2. The production of gravure printing plate can be divided into corrosion (manual version) and electric engraving (electric engraving). At present, the price of manual version is low, but the printing effect is still good, especially the hierarchical version. 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 printing ink, including solvent based ink and water-based ink. Solvent based inks are divided into surface printing inks and internal printing inks (composite inks)

surface printing plastic gravure ink: the surface is smooth and shiny, which is more resistant to friction and smells than internal printing oil. 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 on milk packaging, beverage packaging and frozen food packaging products. 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 film). 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. It is characterized by low cost and reduced glue pollution. However, the effect will be better if you choose the right material for extrusion, control the extrusion temperature, and add a small amount of glue or AC agent as coupling agent between film-forming

length of drying channel of dry-type glue laminating machine. Heating mode, gluing mode, gluing amount control, material tension control, hot drum temperature control and whether there is a cooling and shaping device 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, make it brittle. Pay special attention to the surface tension of PE film, which should be above 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 a composite lining film. High pressure polyethylene film has high extensibility and good impact resistance, but it is not suitable for use as a composite lining film for fried foods and real and cooking bags

pp film is also called polypropylene film. It has high transparency, high strength, good gas and water resistance, but 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, PVCD high resistance diaphragm, PVC, PP, PE heat shrinkable film

producers and users 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 affordable qualified packaging bags

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

I. diluent proportion of 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%, isopropanol 50%, n-butanol 3%