working principle

The dry laminating machine is mainly used for the coating and lamination of cellophane, aluminum foil, nylon, paper PET, OPP, BOPP, CPP, NY, PE and other reel-shaped substrates.

The working principle of dry compound machine is as follows:

1. Preparation

First of all, install the guide rollers of the substrate according to the routing direction, adjust the adhesive in proportion, start the heating system of the oven, and when the corresponding set temperature is reached, start the transmission motor to start the coating production.

2. Coating

3. Compound

After EPC gas-liquid deviation correction, it enters into the composite part and is bonded with the base material of the second unwinding part to realize the composite process.

4. Cooling and winding

After cooling the coil, the overall production and processing of the substrate is completed. The following issues should be noted during production.

(1) Adjust the flatness of the substrate by adjusting the position of the deflection roller.

(2) The composite pressure between the composite rolls is adjusted by adjusting the relative distance between the two composite rolls.

(3) By adjusting the tension clamp of clutch and brake to control the traction tension and winding tension of the substrate, the machine can run smoothly, thus obtaining good coating quality and composite effect.

Operation and commissioning technology

The dry-type composite products often have defects such as bubble wrinkling and poor adhesion.

1. Methods to avoid bubbles in finished products

(1) Increase the depth of adhesive or select adhesive with good wettability.

The adhesive that is too thin or with poor wettability is easy to flow, making the adhesive on the base material uneven, and thus prone to longitudinal or transverse water lines. Bubbles are likely to appear in the part with small amount of glue, which can be reduced by increasing the concentration of adhesive or selecting adhesive with good wettability.

(2) Corona treatment of substrate

Some plastic film substrates have poor adhesive adhesion ability. In order to improve the adhesion ability of such substrates and ensure the coating quality, the surface tension of the substrate is required to reach about 42~56Mn/cm. Before coating, a set of corona processor can be added to carry out corona treatment on the substrate surface to make the surface fuzz, so as to enhance the surface tension, so as to increase the amount of adhesive coating on the substrate surface to avoid bubbles.

(3) When the scraper is installed and adjusted correctly, the amount of glue applied mainly depends on the depth of the mesh hole of the anilox roll. The deeper the mesh hole is, the more glue applied, the less light the mesh hole is. Correct adjustment of the scraper can ensure a more uniform amount of glue applied, thus reducing or avoiding bubbles.

In the actual operation process, it is advisable to adjust the pressure of the scraper with the 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 lift the scraper to form a gap, making the coating uneven.

Because the surface of the anilox roll is not smooth, if the installation angle of the scraper is too large, when it is running at high speed, the elastic scraper blade is easy to vibrate or jump, making the glue spring up, causing the difference in coating amount to increase. Generally, the radial angle between the scraper and the contact point of the anilox roll is between 15 ° and 30 °.

If the scraper is flat, the coating amount will be even. Otherwise, the difference in coating amount will become larger. The flatness of the scraper depends on the installation method of the scraper, and the other part may also be related to the impurities inside the blade holder groove or the blade and the lining. Therefore, when installing the scraper, clean the lining first, and then put the new blade behind the lining, and put it into the blade holder groove. When tightening the screw on the back of the blade, tighten it gradually from the middle of the blade to both sides, and tighten it alternately on both sides, To prevent the blade from warping, it usually takes two or three times to tighten the screw. While tightening the screw, use a cloth to clamp the blade and the lining, and tighten it outwardly, so that the assembled scraper is relatively flat.

(4) Proper drying temperature

The proper drying temperature can make the adhesive on the surface of the substrate fully dry bath. Generally, the dry bath temperature should be adjusted to 80~100 ℃. If the temperature of several baths is too high, the adhesive surface has crusted, and the part below the surface is not fully dry, which makes it difficult for the exhaust gas to escape, and it is easy to bubble. On the contrary, the dry bath temperature is too low, and the adhesive cannot be completely dried. After a period of time, the finished product will also form bubbles due to the natural volatilization of the adhesive. During the composite, the temperature of the composite heating roller will be increased, and the composite angle will be reduced, which is conducive to the bubbles discharging from the composite film.

(5) Adjust composite pressure and speed

If the composite pressure is not enough, it is easy to produce bubbles. Increasing the composite film's pressing temperature and composite pressure can greatly reduce bubbles. Since the contact between the two composite rolls is a linear contact, reducing the operating 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 the film, clean the composite roll, and pay attention to environmental sanitation.

2. Methods to avoid wrinkling of finished products

(1) Reduce the tension of traction substrate

The film stretch is too large and the shape is not enough, so it is easy to cause the composite film to wrinkle when cooling and shrinking. 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 errors, some plastic film substrates are prone to wrinkle on the guide rollers. During production, the flatness of the substrate can be adjusted by adjusting the position of the deflection roller. Of course, we can also add some flattening rolls or bending rolls to the appropriate position before lamination to stretch the film.

(3) Adjust the pressure of compound roller

In the production process, special attention should be paid to adjusting the composite pressure of the two composite rolls. Uneven composite pressure, such as low pressure, is most likely to cause the composite film wrinkling.

In addition, cleaning the composite roll and replacing the damaged rubber press roll can also prevent the wrinkling of the composite product. In the design, if a preheating roll is added to preheat the surface of the second unwind substrate before the composite, the temperature of the second unwind substrate and the coated substrate before the composite is basically the same, and can also prevent the curling deformation of the composite film after cooling.

3. Methods to avoid poor adhesion of finished products

(1) Too little glue coating or no adhesive coating on the surface of part of the substrate will cause the two substrates to be difficult to fit when composite. We can choose the anilox roller with deep mesh holes, or increase the amount of glue coating on the surface of the substrate by increasing the pressure of the rubber roller and reducing the contact pressure between the scraper and the anilox roller. For some plastic film substrates, corona treatment can be carried out before coating to make their surface fuzz, so as to improve the adhesive adsorption capacity of the substrate and increase the amount of adhesive on its surface.

(2) Select appropriate drying temperature

Too high or too low temperature will affect the adhesion fastness of the composite film. When the substrate is coated in a dry bath, the heating temperature is too high or after high temperature cooking, the surface layer of the adhesive will be carbonized, thus damaging the bonding ability of the adhesive. If the drying temperature is too low, the adhesive will not cure completely, the adhesive's viscosity is poor, and the composite is not firm. After a period of time, bubbles will easily form in the composite film, which will damage the composite quality of the product. Of course, we can choose the adhesive with high temperature resistance and good cooking resistance to adapt to drying at higher temperatures, such as polyurethane adhesive.

(3) Properly increase the composite pressure

Excessive lamination pressure or uneven pressure at both ends of the lamination roller will cause the surface of the composite film to wrinkle, and the hollow tunnel will be formed at the wrinkle after lamination, which will affect the bonding fastness of the finished product. Proper increase of composite pressure is beneficial to improve the bonding force of composite.

In addition, in order to improve the bonding effect and quality of the composite, foreign matters, dust and other sundries should be avoided from adhering to the adhesive or the composite surface of the substrate.

Conclusion

During operation, carefully observe all kinds of problems and faults in the production process, and reasonably use the above methods to eliminate the faults. When there are multiple problems or failures, it may not be possible to take a single method into account. At this time, the light should be avoided and the heavy should be paid attention to. The key problems should be solved and then other methods should be used to solve the secondary problems one by one.