Dry composite products often have defects such as bubbles, wrinkling and weak adhesion. Today, the soft packaging bag manufacturer, Beite packaging, introduces how to deal with the defects of dry composite products.
1. Methods to avoid bubbles in finished products
(1) Improve the depth of the adhesive or choose a good wetting adhesive.
The adhesive with too thin or poor wettability is easy to flow, which makes the adhesive uneven on the substrate, so that the longitudinal or transverse water lines are easy to appear. Small amount of glue on the part is likely to appear bubbles, you can increase the concentration of adhesive or choose a good wetting adhesive to reduce the generation of bubbles.
(2) Corona treatment of substrate
In order to improve the adhesion ability and ensure the coating quality, the surface tension of the substrate should reach about 42 ~ 56Mn / cm. Before coating, a set of corona processor can be added to the surface of the substrate for corona treatment, so as to enhance the surface tension, so as to improve the surface tension Glue the surface to avoid bubbles.
(3) When the scraper is installed and adjusted correctly, the size of the glue application mainly depends on the depth of the net hole of the anilox roller. The deeper the mesh hole is, the more glue is applied, and the shallower the net hole is, the less the coating amount is. The correct adjustment of the scraper can ensure that the glue amount is more uniform, so as to reduce or avoid bubbles.
In the actual operation process, it is appropriate to adjust the pressure of the whole scraper by using the pressure hammer method. The pressure of the scraper is generally 200 ~ 400kPa. When coating, if the pressure of the scraper acting on the anilox roller is too small, when impurities are mixed, it is easy to jack up the scraper to form a gap and make the coating uneven.
Because the surface of the anilox roller is not smooth, if the angle of the scraper is too large, the elastic blade will easily vibrate or jump when it is running at high speed, which will cause the glue liquid to bounce up and cause the difference of coating amount to increase. Generally, the radial angle between the scraper and the roller is selected between 15 ~ 30 °.
If the scraper is flat, the coating amount will be uniform. Otherwise, the coating amount difference will become larger. The flatness of the scraper depends on the installation method of the scraper. In addition, it may be related to the impurities in the blade slot or on the blade and lining. Therefore, when installing the scraper, clean the lining first, and then put the new blade behind the lining and install it into the tool carrier groove. When tightening the screw on the back of the blade, you should first remove the blade from the middle of the blade In order to prevent the blade from warping, the screw should be tightened two or three times. At the same time, the screw should be tightened with cloth to clamp the blade and lining, and the blade should be tightened to the outside. In this way, the assembled scraper will be relatively flat.
(4) Suitable drying temperature
If the drying temperature is appropriate, the adhesive on the surface of the substrate can be fully dried. Generally, the drying temperature should be adjusted to 80 ~ 100 ℃. If the temperature of some baths is too high, the surface of adhesive has already crusted, and the parts below the surface are not completely dried, so that the exhaust gas is difficult to escape, and foaming is easy to occur. On the contrary, if the temperature of the drying bath is too low, the adhesive can not be completely dried. After a period of time, the finished product will form bubbles due to the natural volatilization of the adhesive. When compounding, increase the temperature of the composite heating roller and reduce the composite angle, which is conducive to the bubble discharging from the composite film.
(5) Adjusting compound pressure and speed
If the composite pressure is not enough, it is easy to produce bubbles. If the pressing temperature and pressure of the composite membrane are increased, the bubbles can be greatly reduced. Since the contact between the two composite rolls is line drawing contact, reducing the running speed of the equipment can increase the pressing time between the composite rolls, so that bubbles can be fully discharged from the composite film, which is also conducive to reducing bubbles.
In addition, in order to prevent dust adhesion on the composite surface of the film, it is necessary to clean the anilox roll and film, clean the composite roller and pay attention to environmental hygiene.
2. Methods to avoid wrinkling of finished products
(1) Reduce the tension of traction substrate
It is easy to cause wrinkling of the composite film when it is cooled and shrinked. Wrinkling can be reduced by properly reducing the running tension of the substrate.
(2) Adjust the flatness of the substrate
If the guide rollers assembled on the dry laminating machine have parallelism error, then some plastic film base materials are easy to produce wrinkles on the guide rollers. During production, the flatness of the base material can be adjusted by adjusting the position of the deflection adjusting roller. Of course, we can also add some flattening roller or bending roller at the appropriate position before lamination to stretch the film.
(3) Adjust compound roller pressure
In the production process, special attention should be paid to the adjustment of the composite pressure of the two composite rollers. The uneven composite pressure, such as low pressure, is most likely to cause the composite film to wrinkle.
In addition, cleaning the composite roll and replacing the damaged rubber roller can also avoid wrinkling of the composite product. In the design, if a preheating roller is added before the composite to preheat the surface of the second unwinding substrate, the temperature of the second unwinding substrate and the coated substrate before lamination is basically kept the same, and the curling deformation of the composite film after cooling can be prevented.
3. Methods to avoid loose bonding of finished products
(1) Too little glue or no adhesive on the surface of part of the substrate will cause the two substrates to be difficult to fit. We can choose the anilox roller with deep mesh hole, or increase the rubber roller pressure and reduce the contact pressure between the scraper and the anilox roller to increase the glue amount on the surface of the substrate. For some plastic film substrate, corona treatment can be carried out before coating to make its surface fluffy, so as to improve the ability of the substrate to absorb adhesive and increase the amount of coating on the surface.
(2) Choose suitable drying temperature
If the temperature is too high or too low, the adhesion fastness of the composite film will be affected. Coating substrate dry bath