Common causes of film failure and troubleshooting

The film is coated with polypropylene (PP), polyvinyl chloride (PVC) and other plastic films by mechanically evenly applying a layer of adhesive to achieve bonding with the paper under a certain temperature and mechanical pressure. Solid process. During the lamination process, the temperature, pressure and time of the paper and the plastic film passing through the thermal lamination mechanism are handled. The fusion stage controls the thickening of the adhesive, the amount of glue, the drying tunnel temperature, the heat roller temperature, and the mechanical pressure. , mechanical speed and other factors, you can avoid the bubble when the film, paper and plastic bonding is not secure and other issues.

The laminating process is to apply the adhesive on the surface of the printed matter and the plastic film, and then bonding them together after hot pressing to form a paper-plastic-in-one printing product. After the film is covered, the printed product has more than one surface. Thin and transparent plastic film, the surface is smoother and brighter, which improves the glossiness and fastness of the printed matter, makes the ink color more vivid, and the printed product through the film has moisture-proof, waterproof, anti-stain, wear-resisting and chemical resistance. And so on.

The lamination process requires the production personnel who are engaged in laminating processing to apply the proper processing temperature and pressure according to the different properties of the paper and the ink, so that the adhesive can firmly bond the plastic film and the printed paper into a paper-plastic integrated one. Film coating product quality standards: The surface is clean, flat, not blurred, good finish, no wrinkle, no blistering, no paper-plastic separation, no powder foil marks. Appropriate dryness, no sticking to surface film or paper. After slitting the film, the size of the slit is accurate, the edge is smooth, and no film is produced. No obvious curling, seven bends and Alice problem.

Plastic film composite process finishing of printed matter, under normal circumstances, there are advertising pictures, all kinds of calendars, books and magazine covers, packaging food boxes, wine boxes and other box-type packaging. After the surface of the paper is coated with a film, the printed products are also subjected to printing, scraping, gluing, baking, die-cutting, indentation, and the like. At the same time, it will also be influenced by chemical substances such as printing ink thinners, various solvents, moisture and dry oil, and corrugated cardboard pastes. The printed products will also undergo external forces such as folding, scraping, pressing, and die-cutting. Impact, exposure to higher temperatures, baking, sunlight, ultraviolet light, and moist environment. Only by satisfying these conditions can a laminated product be considered a qualified printed product.

1 coating adhesive and adhesive fastness

The adhesive is an intermediate material that covers the printed matter and the film, and mainly plays a role of adhesion. The performance of the adhesive under certain conditions is one of the key factors that determine the quality of the film.

There are two types of adhesive used for the film. The first is rubber type; the second is resin type. Printing companies must choose adhesives according to the specific conditions of different papers and printings. In general, a rubber-type adhesive may be used for a small print area on the surface of a paper sheet. In contrast, a resin-type adhesive may be used for a large printed image having a large surface area. This is because most of the printed products use resin type bright light and quick-drying inks. Therefore, the resin-type adhesive and the resin-type ink film surface are easily adhered to each other, and accordingly, the adhesive fastness is good. The resin-type adhesive is generally composed of two or more components. To some extent, the operator's difficulty is increased. For example: A and B are two resin composition ratio. Problems such as the service life of the adhesive after mixing will directly affect the degree of bonding, but as long as the strict grasp of the production process can be resolved.

During the lamination process, the adhesive must not only bond firmly with the polypropylene plastic film, but also bond with the paper firmly. Therefore, the viscosity value of the adhesive directly affects the bonding strength of the paper and the plastic film. In the actual working process, due to the different area of ​​the printing ink layer of the product, the method of adding thinning water can be adopted to continuously adjust the concentration of the adhesive. . The surface area of ​​the printed product is small, the adhesive concentration can be reduced by about 15%, and the corresponding graphic product with a large area has to increase the adhesive concentration. Since the adhesives used by the factories do not belong to the same manufacturer, their properties, proportions, chemical compositions, and adhesives are different. There is no single standard and they can only be treated differently according to their specific conditions. .

2 Wrinkle when filming

1 paper wrinkle phenomenon: The main reason is that when the paper passes through the hot lamination mechanism, it does not receive natural heat and pressure in a flat and natural manner, but appears longitudinal or oblique wrinkles, and most of them appear on the tip of the dragging part.

2 wrinkles of plastic film: The main reason is that the film appears in the process of conveying. Due to improper traction, the tension of the film may be large or small, and the film may appear oblique, longitudinal or transverse wrinkles.

3 Wrinkles of paper and film: After the plastic film and paper of the hot laminating mechanism, wrinkles in the longitudinal direction or in the center portion of the film may occur at the tip portion.

3 film bubble causes and solutions

After the film is applied to the slitting, indentation, storage, package, corrugating, and stacking of books, the overprinted multi-colored dark-printed position of the printed matter is exposed. The thick layer of the ink layer is prone to sand-like stripes and worms. The phenomenon of turbulence in the prominence of the tortoise-like film, commonly known as "bubbling", occurs in similarly-shaped bubbles in severely unprinted parts of the white paper.

Strictly putting a good production process is an important part of the coating process. We know that the entire coating process can be roughly divided into three stages: pretreatment, lamination, and slitting. In terms of its importance, it is mainly in the first two stages. The purpose of the pre-treatment is twofold: First, it is the de-wetting of the moisture in the printed product. As the printing paper will emit a large amount of water vapor impact colloid under the hot pressure of the hot roller. This results in loss of adhesiveness of the film adhesive, lowering of the adhesive strength and occurrence of bubble phenomenon, and secondly, further curing of the ink layer of the printed product. There will be a certain amount of solvent in the ink layer if no pretreatment is performed. After lapping, the problem is not found for a certain period of time, and the solvent slowly dissipates over time. Slowly further dissolution of the colloid leads to a loss of stickiness of the colloid, which releases the paper from the plastic film, that is, blistering. The actual work has been tested, a print is divided into two groups, a group of pre-film treatment, and the other group does not carry out pre-treatment, and then under the same conditions for coating, after a period of time observed, the results found that after No foaming occurred in the treatment, and it was easier to foam without treatment. Therefore, the pre-treatment must be carried out so that the various solvents in the ink layer can be volatilized as quickly as possible so as to ensure the permanent firmness of the adhesive strength.

In the actual work, the cover skins, calendars, cards, and packaging after the film were found, and no blisters were found after the cover book, book cut, and packaging. But after a while. After delivery, bubbles were found in the hands of customers. It's confusing, but it's actually not an incomprehensible phenomenon. It also fully shows that the blistering after the coating has a great relationship with the solvent and other chemical components contained in the ink layer, especially the large area of ​​the printed image. If pre-treatment products are taken before filming. There will be no such phenomenon. It is necessary to strictly deal with issues related to good production processes. Of course, there are other factors that lead to poor adhesion of the film products. For example, the adhesive itself has quality problems, the adhesive is too thick, the added thinning water is too small, the speed is too fast, the temperature is too low, and the pressure is low. , Too much paper dust and other aspects, as long as the strengthening of process management, strengthen the preparation of raw materials acceptance inspection. Fixed point procurement of good quality materials can be solved. In addition, products such as covers, packaging, decorations, advertisements, and the like that require films are left to stand for a period of time after printing, and the conjunctiva is completely cured in the glue in the ink layer. After the solvent is evaporated, it is covered again. You can also overcome the problem of blistering.

4The effect of temperature, pressure, speed, and amount of glue on the fastness of adhesion

Paper and plastic film are the effects of temperature, pressure, and speed on the fastness of the adhesive by hot laminating mechanism. Two kinds of paper-plastic materials are irrelevant to each other and rely on adhesive mediation. Compounding can only be achieved under the effect of thermal stress.

Under the effect of hot pressing force. The adhesive molecules move faster.

Increased capacity, paper, ink molecules attracted to spread. Infiltrate into paper prints and ink layers to produce better affinity. Solidification occurs. The cohesive force generated by the thermosetting properties of the adhesive polymer resin, the plastic film and the printed paper form a solid combination, the appropriate composite temperature, pressure, composite time, the amount of adhesive coating is the quality of paper-plastic composite products Protection.

1 drying tunnel temperature control at 40 ~ 45 °C;
2 hot roll temperature is controlled according to the technical specifications of different types of adhesive at 50 ~ 80 °C;
3 The mechanical pressure is directly proportional to the adhesive force, the pressure is large and the adhesive force is strong, the pressure is low, and the adhesive force is poor. Under the action of the strong pressure, the adhesive is more conducive to infiltrating into the interior of the paper to improve the adhesive force, so the mechanical can withstand Under the circumstances, the pressure is better than the small point, and the surface pressure is controlled at 100kg/cm2 to 150kg/cm2;
4 Machine speed is related to the pressing time. It will determine the length of the pressing time. The length of the pressing time is related to the adhesive force, and the adhesive force with a long pressing time is greater than the short time. In general, the smooth speed of the paper can be faster, and the speed of the paper is slow;
5 The amount of glue used to coat the adhesive, according to experience, according to the roughness of the paper, the size of the printed graphics area, different paper to adjust the amount of glue. Poor paper smoothness, rough or ink coating should be larger. On the contrary, the coating of coated paper with high smoothness should be smaller.

5 film finished curled

The main performance is that after the composite finished product is cut, it is curled in the direction of the film and cannot be maintained in a flat state. When severe, it curls into a cylindrical shape automatically. The main reasons are: 1 the paper being coated is too thin; 2 the paper has more moisture and humidity; 3 the air temperature is low; 4 the paper is loose and has poor smoothness; 5 the film has high pressure, high temperature and long time.