Large and small quality accidents in flexible packaging companies occur from time to time and always cause management headaches. So how to prevent the occurrence of quality accidents? The author believes that the most effective way is to strengthen the various internal inspections of the enterprise, so that the products they make are well known. Everything is at the forefront of the accident, and wants to be at the forefront of the accident, from the source, to prevent product quality accidents.
First, the quality control point of raw materials
1. Film appearance
The first is to check the flatness, thickness, and jaggedness of the two ends of the film. The thickness of the film is generally regarded as a qualified product within ± 5um. If the thickness is greatly different, it will cause fluctuations in the overprint of the printed pattern and the uniformity of the composite sizing. Visual inspection of the film with zigzag ends will cause printing and compound film breakage, resulting in a large number of scraps. (Thickness gauge and visual inspection method.)
To check the static and dynamic friction coefficients of the original film, use the film's friction coefficient meter to detect.
2.Corona value of film
The corona value directly affects the adhesion of the ink and the peel strength after compounding. (Corona pen, corona liquid configured by yourself)
Table 1 Corona values required for various film substrates
Self-distribution halo formulation:
3. Selection and application of thin film materials
The PA film should be selected as A-grade product when it is used for cooking packaging bags . There are step stretching method and synchronous stretching method in the production of PA film. The so-called step stretching method is to stretch the longitudinal or transverse direction first, and then stretch the other. One direction, and the synchronous stretching method is simultaneous stretching in the horizontal and vertical directions, so its shrinkage rate is basically the same when it is exposed to temperature. In the cooking process, the cooking bag is often curled due to the different shrinkage ratio of PA, and the phenomenon of warping is formed.
AL film: density is 2.67g / cm3, excellent barrier property, poor tensile strength, easy to break. AL has a very high corona value on one side, but only about 38 dynes on the other side. One of the most important factors that determines the quality of AL is that the cooling oil must be cleaned during the production of aluminum foil, otherwise it will have a great impact on the composite strength. You can use cotton swabs dipped in distilled water and tap water to wipe the aluminum foil at an angle of 45 °. Once rubbed, the water can spread evenly, which proves that the oil stains are well treated. On the contrary, if the water is in the form of water drops on the aluminum foil, it can be concluded that there is oil stain on the aluminum foil, which is a substandard product.
Aluminized film: The density is basically the same as that of the original aluminized substrate, with little change. Main inspection: adhesion fastness of aluminum plating, pin eye and uniformity of aluminum layer.
4.Quality control methods for other raw materials
Additives for films: Put the films in a curing room at 50-60 ° C for 8-20 hours, and test the coefficient of friction of the film. If the coefficient of friction is larger than that before curing, it means that there is a lot of additives, this method only Can detect the presence or absence of additives, not the amount of additives. (Film friction coefficient meter)
Detection of solvent purity: purity and moisture content of solvents such as ethyl acetate, toluene, n-propyl acetate, isopropanol, and butyl acetate (meteorological chromatograph).
A simple test of the viscosity of inks and glues is to fill the ink or glue with a No. 3 Zahn cup according to a certain dilution ratio, and use the time required to run out to determine the viscosity. The longer the draining time, the larger the viscosity will be, and vice versa, the viscosity will be smaller.
Simple detection of solid content: open the ink, glue bucket, take a certain amount of ink or glue and pour it into the beaker, do not cover the lid, put it in a 50 ° C curing room, and after curing for 24 hours, weigh the ink or glue at this time divided The weight is the so-called solid content, because all solvents are basically evaporated in the curing chamber. (Measuring cup, beaker)
Second, the quality control points that should be paid attention to in the printing process
Surface visual inspection: accurate overprinting, no knife wire, clear printed text pattern. Rewind neatly, the amount of tension, with or without violent tendons. (Visual inspection)
Ink dilution viscosity before the machine: Adjust the appropriate ink viscosity according to machine speed, drying effect, etc. (No. 3 cup, stopwatch)
The adhesion of the ink can be tested by using 3M adhesive tape along 45 °. The best adhesion is that the ink does not transfer. (3M tape)
Detection of ink residual solvents: Meteorological chromatograph is used to detect the residual condition of each solvent.
Third, the quality control points that should be paid attention to in the composite process
Prediction method of sizing amount: sizing amount = 1/5 × glue concentration × glue density × mesh depth.
Detection of sizing amount: After the glue is applied, the printed film (blank film) that has not entered the composite roll is taken from the left, middle, and right three, and their weights are subtracted from the weight of the uncoated raw film, and finally they are taken. average value. (Tensile scale)
Visual inspection of the composite film for air bubbles and white spots. (Visual inspection)
Detection of the tension of the composite film: In the composite film between the winding and the composite roller, draw a cross shape with a blade to see the rolling direction of the composite film at the open position. If it curls toward the inner film, it proves that the inner film tension is large and it should be appropriately reduced Intimal tension. Conversely, reduce the tension of the mask. Unmatched tension of the composite film can also cause tunneling and wrinkling. (Visual inspection)
For the detection of the heating and exhaust of the drying tunnel on the compound machine, you can use a thermometer to check the temperature error. Use a wind meter to check the wind speed of the inlet and outlet wind or use a thin film on the two ports of the drying tunnel of the compound machine. See if the film is blowing in or out. If it is facing outward, it is proved that the incoming air is greater than the outgoing air. You can adjust and increase the amount of outgoing air to try to ensure that the drying tunnel is in a vacuum state. (Wind speed detector)
The peeling force and heat-sealing strength of the cured composite film need to be tested on a film tensile machine to obtain the corresponding peeling data. (Film Tensile Machine)
Residual solvent of composite membrane: Meteorological chromatograph detects the residual amount of solvent.
Friction coefficient of composite film: After curing, a film friction coefficient meter is needed to obtain the proper data.
Water-cooking and cooking of composite film: After the composite film is made into a bag, the contents are filled, and the corresponding water-cooking and cooking test (with or without air bubbles, delamination, peeling force, etc.) is performed after being evacuated by a vacuum machine Meet requirements or meet standards. (Vacuum extractor, back pressure cooking pot, film tensile machine)
Fourth, the quality requirements of the cutting process
To achieve a flat section, moderate tension, no violent tendons, etc. (visual inspection method).
Five, the quality requirements of bag making process
The size of the bag, the heat-sealing position (gauge), and the flatness of the bag can be visually inspected, and the film tensile machine for heat-sealing strength testing can be used.
Six, special detection technology for special composite bags
Boiled packaging bag: The bag should be filled with objects or water (the amount of liquid such as water should be controlled at 1/2 or 1/3 of the bag volume). After boiling at 100 ° C for 40 minutes, there are no bubbles and delamination.
After the contents of the cooking bag are filled, evacuate and place in a pressure cooker at 121 ° C or 135 ° C for 20 to 40 minutes after high temperature sterilization, without delamination and air bubbles. (Back pressure cooking pot)
The product quality of flexible packaging printing enterprises is affected by many external factors, so enterprises should strengthen various inspections in the production process. Testing is the most powerful guarantee for product quality, and it is the most effective way to prevent product quality accidents.