As society's demand for plastic flexible packaging has increased year by year, plastic packaging is covering the market in accordance with its inherently colorful colors, novel designs and ease of use. However, due to the lack of technical information on the manufacturing and material selection of most small and medium-sized packaging color printing companies, professional knowledge has not been popularized, and the quality of the packaged goods has deteriorated and the loss has been enormous. The packaging business is difficult to expand. I will integrate the theory into practical suggestions for the reference of many colleagues in the soft packaging industry.
In general, the printing method is classified into embossing, gravure printing, plain printing, screen printing, and the like. Plastic printing is gravure printing, and the gravure printing machine that is often referred to is a machine-type (or arrangement) gravure printing machine.
1, printing machine
The printing speed of the plastic printing unit is determined by the length of the paper feeding distance between the printing group and the quality of the drying box. The longer the color distance and the better the effect of the oven, the faster the printing speed. Conversely, the printing speed will not go up. The accuracy of the printing press is not only required to synchronize the operation of the various parts of the printing press, but also It is required that the tension control system in each part has good stability, only the tension control design is reasonable, the material discharge is stable, the winding is stable, and the printing will not run in order to maintain the accuracy of the color registration.
2, printing plate
The production of gravure printing plates is divided into corrosion (manual version) and electric engraving (electric engraving). At present, the manual version is inexpensive, but the printing effect is still good for electric engraving, especially the level version. In practice, it has been found that electric engraving requires higher ink. The quality of the printing plate directly affects the printing effect.
3, ink
Plastic gravure ink, solvent ink and water-based ink. Solvent inks are further divided into table Printing Inks and inner printing inks (composite inks).
Table printed plastic gravure ink: The surface is smooth and glossy, which is more abrasion resistant and odor than printing ink. In the lamination process, one-component glue should be used, and the combination with the two-component glue is poor. Note that the amount of glue cannot be too large. Table printing ink is divided into common ink, water resistant ink (beverage packaging ink), label ink (calendar ink), clear ink and so on. Water-resistance ink is mainly used for printing on milk packaging, beverage packaging and frozen food packaging products. Label ink is very smooth, anti-adhesion, scratch resistance, is the best ink for printing a variety of labels. Transparent ink is a special ink for printing aluminum foil and aluminum foil.
Ink (composite ink) is characterized by bright color, print tasteless, peel strength, but the film is not soft and wear-resistant wipe, view its print dull, conducive to laminating. If using glue dry compound, two-component glue should be used. One is to increase the firmness of the composite, and the other is to reduce the odor. However, when one-component glue is used for compounding, the printed ink will often be dissolved or compounded with harmful odor of the glue, and the composite fastness is poor (note that it is not allowed to add alcohol solvent). In addition, there are common composite inks in the ink, which is the ink printing of OPP film (polypropylene ink). Polyester ink should be used for printing PET film (polyester film). The printed pattern is more firm and adhesion does not occur. In short, what kind of special ink is used on what kind of film is the principle of plastic gravure ink.
Water-based inks are generally used for the printing of paper products including paper-plastic composite products. Its characteristics are to meet the paper printing ink absorption, making the print color full, more rare is its solvent is water and ethanol, the environmental pollution is small, known as the environmental protection of the green ink.
4, compound
Composite plastic flexible packaging, sub-film extrusion composite, dry adhesive compound and non-plastic hot pressing compound. Extrusion compounding means that the PE or PP material is hot melted and then extruded to form a film, and the composite product is formed by hot pressing on the printing film, which is characterized by low cost and reduced glue pollution. However, it is better to select the type of extrusion material and control the extrusion temperature, and add a small amount of glue or AC agent as a coupling agent between the film formations.
Dry coating machine laminating machine length, heating method, gluing method, glue control, retractable material tension control, hot drum temperature control and whether it has a cooling and setting device constitute its price level, grade level. In the process of gluing and compounding, first of all, the user should understand that if the glue is to be even, the glue must be diluted. To restore the viscosity of the glue, the solvent on the paint must be volatilized (that is, the concentration process), and thus the compound must be The amount of glue is the key to composite processing. Compounding should pay special attention to reduce the amount of glue. It is therefore recommended not to use it in food packaging.
One-component glue is difficult to eliminate because it is used with surface printing ink prints. Therefore, it is recommended not to use it in food packaging. Special attention should be paid to reducing the amount of glue when compounding.
If using two-component glue compound, in addition to the glue according to the technical data required by the manufacturer to match the ratio, it should also pay attention to the content of curing agent, to reasonably control the amount of glue in order to reduce the odor, the production of plastic dots .
In addition, if you want to use PE film as lamination material, pay special attention to the surface tension of PE film. Usually it should be above 45-52 dyne to ensure the firmness after lamination. (It is recommended to install EDM on the laminator. machine).
5, plastic film
Due to the different requirements of the packaged goods, the different plastic films required for different packages are also different. The following describes the properties and uses of the most commonly used plastic films.
PE film is also a polyethylene film, its use is extremely wide. The feature is low cost, good water resistance, but poor gas barrier properties. Low-pressure polyethylene has low elongation and large tensile strength. It can make the packaging bag very thin, but has poor heat sealing properties and should not be used as a composite film. High-pressure polyethylene film has high extensibility and good impact resistance, but it should not be used as a compound film for deep-fried foods and vacuum and cooking bags.
PP film is also called polypropylene film, which has high transparency, high strength, good gas barrier and water resistance, and only poor oxygen barrier properties. Vacuum, cooking and medicine, beverages and other packaging should not use this film as a fabric. The CPP uniaxially-stretched polypropylene film and the heat-sealable biaxially oriented polypropylene film are very good and most commonly used in vacuum packaging or retort-packed composite liners.
PET, also known as polyester film, has high tensile strength, poor impact resistance, high transparency, and good resistance to oxygen and gas barriers, but it is not resistant to sun exposure and water vapour permeability and can be used as an ordinary vacuum bag or medicine bag. Aluminum plated fabric and substrate. Not suitable for cooking bags.
PA film is commonly known as nylon film and is currently used as a fabric for cooking bags. Its cost is high, and vacuum bags are generally not used.
Other membranes, such as: PE cling film for vegetable and fruit and meat packaging, water-soluble PVA film, PVDC high barrier film, PVC, PP, PE heat shrinkable film....
Producers and applications must select the fabrics and linings necessary for packaging according to the inherent characteristics of various film materials, and strive to produce affordable, quality and cheap qualified bags.
6, Appendix plastic intaglio ink commonly used diluent ratio for reference:
First, the proportion of printed plastic gravure ink using thinner:
Fast drying solvent: ethyl acetate 20%, toluene 80%
Dry solvent: butyl acetate 20%, toluene 80 or 100%
Slow drying solvent: butyl acetate 20%, xylene 80%
(Note: Cannot add alcohol solvent)
Second, table printing plastic gravure ink using thinner ratio:
Fast drying solvent: ethyl acetate 20%, toluene 80%, isopropyl alcohol 40%
Dry solvent: ethyl acetate 25%, toluene 50%, isopropyl alcohol 45%
Slow drying solvent: xylene 50%, isopropyl alcohol 50%
Slow drying solvent: xylene 50%, isopropyl drunk 50%, n-butanol 3%
In general, the printing method is classified into embossing, gravure printing, plain printing, screen printing, and the like. Plastic printing is gravure printing, and the gravure printing machine that is often referred to is a machine-type (or arrangement) gravure printing machine.
1, printing machine
The printing speed of the plastic printing unit is determined by the length of the paper feeding distance between the printing group and the quality of the drying box. The longer the color distance and the better the effect of the oven, the faster the printing speed. Conversely, the printing speed will not go up. The accuracy of the printing press is not only required to synchronize the operation of the various parts of the printing press, but also It is required that the tension control system in each part has good stability, only the tension control design is reasonable, the material discharge is stable, the winding is stable, and the printing will not run in order to maintain the accuracy of the color registration.
2, printing plate
The production of gravure printing plates is divided into corrosion (manual version) and electric engraving (electric engraving). At present, the manual version is inexpensive, but the printing effect is still good for electric engraving, especially the level version. In practice, it has been found that electric engraving requires higher ink. The quality of the printing plate directly affects the printing effect.
3, ink
Plastic gravure ink, solvent ink and water-based ink. Solvent inks are further divided into table Printing Inks and inner printing inks (composite inks).
Table printed plastic gravure ink: The surface is smooth and glossy, which is more abrasion resistant and odor than printing ink. In the lamination process, one-component glue should be used, and the combination with the two-component glue is poor. Note that the amount of glue cannot be too large. Table printing ink is divided into common ink, water resistant ink (beverage packaging ink), label ink (calendar ink), clear ink and so on. Water-resistance ink is mainly used for printing on milk packaging, beverage packaging and frozen food packaging products. Label ink is very smooth, anti-adhesion, scratch resistance, is the best ink for printing a variety of labels. Transparent ink is a special ink for printing aluminum foil and aluminum foil.
Ink (composite ink) is characterized by bright color, print tasteless, peel strength, but the film is not soft and wear-resistant wipe, view its print dull, conducive to laminating. If using glue dry compound, two-component glue should be used. One is to increase the firmness of the composite, and the other is to reduce the odor. However, when one-component glue is used for compounding, the printed ink will often be dissolved or compounded with harmful odor of the glue, and the composite fastness is poor (note that it is not allowed to add alcohol solvent). In addition, there are common composite inks in the ink, which is the ink printing of OPP film (polypropylene ink). Polyester ink should be used for printing PET film (polyester film). The printed pattern is more firm and adhesion does not occur. In short, what kind of special ink is used on what kind of film is the principle of plastic gravure ink.
Water-based inks are generally used for the printing of paper products including paper-plastic composite products. Its characteristics are to meet the paper printing ink absorption, making the print color full, more rare is its solvent is water and ethanol, the environmental pollution is small, known as the environmental protection of the green ink.
4, compound
Composite plastic flexible packaging, sub-film extrusion composite, dry adhesive compound and non-plastic hot pressing compound. Extrusion compounding means that the PE or PP material is hot melted and then extruded to form a film, and the composite product is formed by hot pressing on the printing film, which is characterized by low cost and reduced glue pollution. However, it is better to select the type of extrusion material and control the extrusion temperature, and add a small amount of glue or AC agent as a coupling agent between the film formations.
Dry coating machine laminating machine length, heating method, gluing method, glue control, retractable material tension control, hot drum temperature control and whether it has a cooling and setting device constitute its price level, grade level. In the process of gluing and compounding, first of all, the user should understand that if the glue is to be even, the glue must be diluted. To restore the viscosity of the glue, the solvent on the paint must be volatilized (that is, the concentration process), and thus the compound must be The amount of glue is the key to composite processing. Compounding should pay special attention to reduce the amount of glue. It is therefore recommended not to use it in food packaging.
One-component glue is difficult to eliminate because it is used with surface printing ink prints. Therefore, it is recommended not to use it in food packaging. Special attention should be paid to reducing the amount of glue when compounding.
If using two-component glue compound, in addition to the glue according to the technical data required by the manufacturer to match the ratio, it should also pay attention to the content of curing agent, to reasonably control the amount of glue in order to reduce the odor, the production of plastic dots .
In addition, if you want to use PE film as lamination material, pay special attention to the surface tension of PE film. Usually it should be above 45-52 dyne to ensure the firmness after lamination. (It is recommended to install EDM on the laminator. machine).
5, plastic film
Due to the different requirements of the packaged goods, the different plastic films required for different packages are also different. The following describes the properties and uses of the most commonly used plastic films.
PE film is also a polyethylene film, its use is extremely wide. The feature is low cost, good water resistance, but poor gas barrier properties. Low-pressure polyethylene has low elongation and large tensile strength. It can make the packaging bag very thin, but has poor heat sealing properties and should not be used as a composite film. High-pressure polyethylene film has high extensibility and good impact resistance, but it should not be used as a compound film for deep-fried foods and vacuum and cooking bags.
PP film is also called polypropylene film, which has high transparency, high strength, good gas barrier and water resistance, and only poor oxygen barrier properties. Vacuum, cooking and medicine, beverages and other packaging should not use this film as a fabric. The CPP uniaxially-stretched polypropylene film and the heat-sealable biaxially oriented polypropylene film are very good and most commonly used in vacuum packaging or retort-packed composite liners.
PET, also known as polyester film, has high tensile strength, poor impact resistance, high transparency, and good resistance to oxygen and gas barriers, but it is not resistant to sun exposure and water vapour permeability and can be used as an ordinary vacuum bag or medicine bag. Aluminum plated fabric and substrate. Not suitable for cooking bags.
PA film is commonly known as nylon film and is currently used as a fabric for cooking bags. Its cost is high, and vacuum bags are generally not used.
Other membranes, such as: PE cling film for vegetable and fruit and meat packaging, water-soluble PVA film, PVDC high barrier film, PVC, PP, PE heat shrinkable film....
Producers and applications must select the fabrics and linings necessary for packaging according to the inherent characteristics of various film materials, and strive to produce affordable, quality and cheap qualified bags.
6, Appendix plastic intaglio ink commonly used diluent ratio for reference:
First, the proportion of printed plastic gravure ink using thinner:
Fast drying solvent: ethyl acetate 20%, toluene 80%
Dry solvent: butyl acetate 20%, toluene 80 or 100%
Slow drying solvent: butyl acetate 20%, xylene 80%
(Note: Cannot add alcohol solvent)
Second, table printing plastic gravure ink using thinner ratio:
Fast drying solvent: ethyl acetate 20%, toluene 80%, isopropyl alcohol 40%
Dry solvent: ethyl acetate 25%, toluene 50%, isopropyl alcohol 45%
Slow drying solvent: xylene 50%, isopropyl alcohol 50%
Slow drying solvent: xylene 50%, isopropyl drunk 50%, n-butanol 3%
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