Post press processing of the hottest self-adhesive

Post press processing of self-adhesive products (Part 2)

III. film covering of self-adhesive materials

1 Coating method of self-adhesive label

the coating of self-adhesive label is generally compounded with transparent heater: screw in heater BOPP film on paper self-adhesive material, which can achieve the purpose of protecting patterns, waterproof, corrosion prevention and increasing the three-dimensional sense of the label. Other types of films, such as pet and PVC, can also be used as composite films, but they are not widely used. Due to the high cost of paper roll material coating, it has been gradually replaced by UV glazing process

according to the printing and processing methods of raw materials, self-adhesive labels are divided into sheet fed lamination and roll material lamination. Sheet fed paper is covered with film on the film covering machine. The reel material is compounded at the compounding station of the label machine or on a special compounding machine

① sheet fed paper lamination

according to the function of the laminating equipment and the characteristics of the composite film, there are two lamination methods for sheet fed self-adhesive labels:

instant coating lamination - completed on the laminating machine. The compounding process is as follows: first, the adhesive is coated on the surface of the BOPP film on the reel, and the solvent in the adhesive is volatilized by the drying device, then the sheet fed paper is compounded with the reel film on the compounding station, and the two become one under the extrusion of the hot roller to complete the laminating process

pre coating composite - the surface of the composite film is pre coated with adhesive, including hot-melt adhesive and pressure-sensitive films. The laminating machine is equipped with a heating embossing cylinder. When laminating, the pre coating film is in contact with the sheet fed paper. Under the action of the hot pressing cylinder, the adhesive melts, making the film and the paper bonded into one. If the pressure-sensitive composite film is used, the heating power can be turned off and the composite can be made only by pressure

② web lamination

according to different equipment, web lamination can be divided into:

backing paper composite film lamination - carried out on the label machine, using the special composite film with backing paper, and laminating under the action of the lamination device. This is a traditional film covering method. In recent years, it has been replaced by the process of using bottomless paper composite film

backing free composite film compounding - carried out on the label machine, and the film covering principle is basically the same as the backing paper composite film compounding process. The bottomless paper film relies on its own magic blue 3, which has the surface smoothness (surface tension) of lake blue, pink, gray and gold materials. After rewinding, it can replace the bottom paper. After the adhesive is bonded with its surface, it can also be stripped without residual glue marks. The material used for the paperless film is BOPP film with low surface tension. With low cost, paperless film is the most widely used film covering material at present

dry lamination - it is carried out on the laminating machine or gravure machine, and is mainly used for lamination of film materials. Roll material dry lamination is suitable for large quantities of label products, with good lamination quality and low cost. After the roll label is coated, it is generally necessary to carry out secondary processing such as die cutting and waste discharge on the processing machine, such as some battery labels and alcohol labels

uv film covering process - the latest foreign process, which is mainly applied to the unit type rotary label machine with UV drying device. The process principle is: the surface of the coating material is first printed with UV adhesive by the ordinary printing unit, and the adhesive becomes pressure-sensitive adhesive after curing by the UV drying device. Then, the ordinary BOPP film (the general composite surface has been corona treated) is compounded with the drum material at the laminating station to complete the laminating process. The cost of UV coating is low, and the tension change of the composite film is small. It does not need to be dazzling. In April, the film is used in the middle and late ten days of aerosol utilization and insulation foam including extruded polystyrene board and polyurethane foam, which is suitable for high-speed production. UV coating is a promising process, which has been applied in developed countries in Europe and the United States

2. Technical requirements of the film covering process

the film covering process involves many factors. It is necessary to understand the influence of various process parameters on the film covering quality, and correctly deal with the relationship between them to achieve the best effect. See the attached table for the technical parameters and precautions involved in the film covering process

technical parameters and precautions involved in the film coating process

technical parameters and precautions

the drying temperature is controlled between ℃, which can fully volatilize the solvent and avoid overheating and deformation of the film

composite temperature the temperature of the embossing cylinder is controlled at ℃, which can dissolve the adhesive and prevent overheating and deformation of the film

composite pressure ensures the axial pressure of the embossing cylinder is consistent, The pressure should be kept within kg/cm2

the adhesive coating should be thin, controlled at g/cm2, and the thickness is μ m. To avoid over thick coating

the machine speed should be controlled at sheet/minute for single sheet paper and meter/minute for web paper. In addition, it is also related to other parameters

the film tension should be adjusted to the minimum to achieve correct coating and compounding. To avoid excessive tension

roller accuracy. The surface of the embossing roller should be smooth and clean, without scratches and pits. To ensure the ovality, concentricity and other mechanical accuracy indicators

environmental factors to keep the environment clean, air purification devices are required. Control the temperature and humidity of the workshop to prevent the deformation of paper or film

the thickness of the ink should be deep ink and shallow printing, so as to avoid the reduction of surface tension caused by the excessive thickness of the ink layer, making the film unstable

the ink should be dried thoroughly, so as to avoid foaming phenomenon

the ink additive should control the dosage of the desiccant to prevent the crystallization of the ink layer. The surface of crystallized ink will have weak film coating

source: Shenzhen self-adhesive