Paper Coating Technology (3)

Film coating operation should pay attention to the problem

1. The thickness of the plastic film (BOPP) used for laminating should be 0.01 mm to 0.22 mm, and the transparency should be more than 90%, and the thermal shrinkage should be small. If the pre-coating film is on the machine, you should check the shelf life of the plastic film, whether the coating layer on the plastic film is even, whether the surface has been scratched, crush, impurities, stains and so on.

2. According to the size of the product that needs to be covered, choose a plastic film of different specifications and width. At the same time, the side profile should be adjusted according to the requirements of the product, and the gap of the paper feeding roller should be adjusted according to the paper thickness, and the guide roller should be adjusted so that the tension on both sides of the plastic film is consistent, and the plastic film is free from wrinkles on the surface during operation.

3, when the film is transferred in the process of conveying the paper is not allowed, the adhesive glue will be transferred from the part of the plastic film is not covered with the rubber roller roller, with the growth of time, stranded on the rubber roller roller As the amount of glue gradually increases and the viscosity increases, the adhesive glue accumulated on the rubber roller roller will produce a certain strength of sticking force on the printed product, resulting in localized tensile deformation of the coated film to generate wrinkles.

4. In the laminating operation, the blanket cylinder and the heating cylinder of the lamination roller should be kept flat, the mirror surface of the heating cylinder should be clean, and the pressure balance rollers on both sides should be flexible in rotation. The installation position of the applicator roller should be correct so that the adhesive can be coated evenly. The pressure roller should be installed stably to ensure that the printed surface has the same force. In the process of mechanical operation will be changed at any time, there is a failure, the operator must pay attention to observation, so that early detection and early detection of failure.

Causes and Treatments of Common Film Failures

Lamination is a process in the post-printing process. Various quality problems often occur in the lamination, directly affecting the quality of the lamination of the printed product, causing unnecessary losses and waste, which must be taken seriously. deal with.

1, film products surface blisters foaming

Phenomenon and reason:

(1) The humidity of the paper is large, and the printed product is not dried and the film is covered. After the film is gradually dried after the film is coated, water vapor in the paper evaporates, and variegated dots or bubbles are formed between the surface of the paper print and the plastic film.

(2) Paper prints have dust, impurities, and smudges on the surface after printing with dust and dust or plastic film.

(3) When the paper is printed, the release agent and excessive drying agent are added to the ink.

(4) The adhesive glue of the film is too thick or too thin, and the adhesive layer is too thin or too thick.

(5) Coater coated adhesive adhesive is not uniform or adhesive aging.

Approach:

(1) Dry the paper prints and adjust the temperature and humidity of the workshop.

(2) Clean dust and impurities on the surface of paper and plastic film.

(3) Control the addition and release of anti-sticking agent and quick-drying agent in ink when printing paper.

(4) Strictly mix the ratio of adhesive and thinner to adjust the thickness of the adhesive layer and the concentration of the glue.

(5) Adjust the gap between the two rolls of the coater to make it uniform and replace the aged adhesive glue.

2, wrinkling when the paper print film is covered

Phenomenon and reason:

(1) Paper prints are subject to high humidity or high ambient temperature and humidity in the production site, resulting in tightly printed paper sheets or wavy flounces.

(2) When the film is coated, the roller pressure is uneven or the gap between the guide rollers is not equal, resulting in unevenness in the coating of the paper product, resulting in wrinkling.

(3) When the conveyer belt conveys the paper, the paper print is skewed and the rules are not uniform.

Approach:

(1) Strictly control the change of temperature and humidity in the workshop, knock out the deformed printed paper and then perform lamination.

(2) Adjust the laminating pressure between the blanket cylinder and the heating cylinder of the lamination roller and the gap between the guide rollers.

(3) Adjust the guide roller conveyor belt and adjust the side guide moment, and note that the paper feed moment is neat.

3, plastic film wrinkling

Phenomenon and reason:

(1) The temperature of the heating roller or the temperature of the drying tunnel when the film is laminated is too high, and the plastic film is softened and deformed. Under the pressure of the heating roller, the film is wrinkled.

(2) In the laminating operation, the pulling force of the film is too tight, causing the film to wrinkle or wrinkle.

(3) The filming speed is too fast, the adhesive glue is not completely dry, causing the film to wrinkle.

Approach:

(1) Adjust the temperature of the hot-pressing cylinder or the temperature of the drying tunnel so that it conforms to the hot-pressing conditions.

(2) Adjust the traction force of the plastic film, adjust the stretch roller, loosen the film pressure, flatten the film, and press it together.

(3) Decrease the speed of the main machine of the laminator, slow down the transfer time, and press the plastic film and the paper print in a state where the adhesive glue is completely dry.

4, film product processing curl

Phenomenon and reason:

(1) The paper print is damped and deformed.

(2) The climate is humid and the temperature and humidity of the production site are high.

(3) The heating roller temperature of the laminating roller is high, and the laminating pressure between the blanket roller and the heating roller of the laminating roller is large.

(4) The plastic film is too tight.

Approach:

(1) After the laminated product is flattened, slit it.

(2) Control the temperature and humidity of the production site environment.

(3) Properly lower the temperature of the heating roller of the nip roller and adjust the laminating pressure between the blanket roller and the heating roller of the nip roller.

(4) Adjust the traction force of the plastic film.

5, after the paper-plastic lamination is not strong, in the post-processing of natural separation of paper and plastic

Phenomenon and reason:

(1) The ink layer of the printed paper that needs to be coated is not dry.

(2) The pressure at the time of paper-plastic lamination is too small, the speed of lamination is fast, and the film temperature is low.

Approach:

(1) Extend the drying time of paper prints.

(2) Properly increase the pressure of lamination, adjust the speed of lamination, and the temperature of lamination.

6, after the film printed surface whitening

Phenomenon and reason:

(1) The temperature and humidity of the filming site environment is too high, the outer layer of the printed paper sheet is dried, and the inner layer is still not dry.

(2) Water vapor is contained between the paper print and the plastic film overlay after coating.

Approach:

(1) Strictly control the temperature and humidity of the production site environment.

In summary, the reasons that affect the quality of the coated products are many, and it is a high-tech work to achieve the best results after the paper prints are coated. We should solve specific problems by strictly crafting, standardizing operations, analyzing causes, identifying major problems, and targeting specific situations. Only in this way can we reduce waste and continuously improve the quality of film-covered products to meet the needs of the market.