Technology and effect of the hottest in mold label

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Technology and effect of in mold label (I)

in model label (abbreviated as IML, which has obtained the invention patent authorization of the United States and Canada) refers to a pre printed paper, composite or film label, with a special hot-melt adhesive coated on the back, which is placed in the model before plastic blowing, injection molding or thermoforming to generate a plastic bottle or box. The label and the container form a whole box. The label and the bottle body are basically on the same plane, and the edge of the label can't be seen, just like printing pictures and texts directly on the surface of the bottle body. The labeling machine is no longer needed in the future. It is a new labeling technology with great potential

manufacturing process of in mold label

take the common PP bottle as an example. The label also uses PP synthetic paper. After surface treatment and trademark printing, it is coated with special hot-melt adhesive on the back, and then die-cut to make the label. The label in the mold can be divided into front label and back label according to the different positions, that is, the trademark pasted on the front or back of the package. The printed labels are stacked in single sheet form, and the front label and back label are placed in two boxes of the in mold labeling machine respectively

at the beginning of a cycle of the mold, the mold of the bottle body is opened, and the printed front and back labels are sucked up by the manipulator and placed at the corresponding positions in the mold. The label printing faces the inner wall of the mold, and the small hole on the mold absorbs air, and the vacuum is used to firmly adsorb the label in the mold. At the same time, the plastic bottle raw materials are heated and droop in a soft tube, and the molds with labels adsorbed on the inner wall are quickly closed. Air is blown into the hose to make the plastic bottle close to the inner wall of the mold. At this time, the temperature in the whole mold is quite high. When the back of the label is close to the bottle body, the solid adhesive coated on the back of the label begins to melt, and the label and the plastic bottle body are combined in the mold

when the mold is opened, the plastic bottle body is formed, and the label and the bottle body are integrated. The printed trademark is embedded on the surface of plastic products. In this example, the label is on the same surface as the bottle, as if there is no label, and the color graphics and text are directly printed on the surface of the bottle

materials for in mold labels

label materials used for in mold labels are mainly divided into two categories: paper and plastic film. At the beginning of the appearance of in mold labels, paper labels coated with hot melt adhesive backing were placed in the model and bonded to blow bottles or fused to bottles. Recently, for the purpose of recycling and performance, synthetic paper materials such as Polyart or synteape have been used, especially the newly developed OPP film (directly melted on the container, eliminating the orange peel effect). All in mold label materials must have good flatness, so that there will be no failure when they are input from the nozzle of the injection molding machine

1. Ordinary synthetic paper has poor surface smoothness, low strength, small elastic deformation, and difficulty in high-grade color printing. It is suitable for large-area application of barrel containers. The paper label is easy to deform in case of water or moisture, which reduces the use value. However, it is less affected by static electricity when used, and the loss when blowing the bottle to absorb the label is relatively small. Paper labels and plastic bottles are not homogeneous materials, which is not conducive to the recycling of bottle bodies

2. The film material is a special multi-layer coextrusion surface material with smooth surface, which can be printed in a variety of printing methods. In the process of label processing, the deformation will not cause overprint and inaccurate die cutting. Some film materials can stretch and shrink and deform (such as primax, FasClear, etc.). When applied to the bottle body, they can deform with the shape of the bottle body, and the label will not wrinkle after compounding to the surface of the bottle body. Because the ink will not penetrate under the surface of the film material, the color of the label printed by the film material is bright, and the color effect is much better than that of the paper material. Now, plastic film in mold label materials are generally used at home and abroad

Japan Yupo in mold label was the first to enter the Chinese market, and this in mold label material has a good reputation in the world. Now, French Polyart blow molded in mold labels have also entered the Chinese market. Some domestic enterprises are stepping up the research and development of in mold label materials

in mold labels are required to have good printability, so that the ink can be firmly attached to the surface of the material; In the post-processing process to have good processing adaptability, suitable for die-cutting and cold stamping processing. In mold label materials also need to have good use characteristics, which can be integrated with plastic bottles during blow molding

in mold label material structure is composed of printing surface, intermediate layer and adhesive layer. The function of printing surface is to receive ink and form color pictures and texts; The middle layer supports the printing surface, gives the material enough stiffness and transparency, does not deform on the printing machine and under the action of high temperature, and ensures the accuracy of overprint; The adhesive layer melts under the action of high temperature, so that the label material and the plastic container become one, ensuring that the label and the plastic bottle are firmly adhered together

there are generally three kinds of surface materials for printing: PE, BOPP and pe+pp. At present, most plastic containers are made of PE, so the use of PE in mold labels is more conducive to the initial realization of China's strategic transformation from a large material country to a powerful material country for recycling. When printing in mold labels, in order to improve the ink affinity of printing surface materials, it is generally necessary to coat the surface coating or improve the surface properties by corona discharge

there are two kinds of structures on the surface of the adhesive layer: flat non striated structure and striated structure. The adhesive layer with non textured structure can directly contact with the blank and exhaust naturally, which is suitable for small area labels. The surface of the adhesive layer with the striated structure is embossed with the striated structure. When labeling, the gas between the label and the bottle body is vented through the striated exhaust channel, reducing the generation of bubbles. The adhesive layer also has antistatic property to prevent double sheets during printing; The adhesive layer should also have certain sliding property to ensure the smooth separation of labels and the smooth printing process

printing and processing of in mold labels

the face paper of in mold label materials is mostly synthetic paper, which can be printed by sheet fed printing machine or web gravure printing machine. Different printing manufacturers can choose different printing processes according to their own equipment conditions. Some printing plants also use flexographic printing, letterpress printing and offset printing with small and medium format, plus offline die cutting and forming. At present, offset printing and flexographic printing are in the majority

(1) offset printing has outstanding advantages in fine dot printing, with rich printing levels, but the line, field printing effect and printing saturation are not as good as other printing methods. Offset printing cannot realize on-machine printing processing like flexo printing. After printing, offline die cutting, cold pressing, polishing and other processes must be carried out. However, offset printing is suitable for small batch and multi variety label printing, with short cycle and strong flexibility

(2) gravure printing is superior to offset printing in field printing and printing color saturation. Color difference control is relatively convenient, but it is slightly insufficient when printing small dots and rich layers of trademarks. On gravure printing machines, the paper path of label materials in the mold is longer than that of other printing methods, so the chance of static electricity is greater. Gravure plate making has high cost and long cycle, which is suitable for in mold label printing of long plates

(3) embossing is suitable for printing field and line trademarks. The effect of printing small dots is not ideal. It is also easy to control the color difference of the same batch of products, but ink bars are easy to appear. From a cost perspective, embossing is cheaper than gravure and flexo printing

(4) the advantage of flexographic printing is that the printing and subsequent processing processes can complete the final printing and processing products at one time. Now, with the improvement of flexographic plate making technology, the dot printing quality has been greatly improved. Flexographic printing of in mold labels has been recognized by some manufacturers, but printing with environmental friendly water-based ink is not mature. At present, experienced manufacturers use UV ink with good fluidity, which is also the main trend of in mold label printing. UV ink is suitable for printing in mold labels with high quality requirements. The printing color is bright and fast drying, which is suitable for large and medium-sized batch production. For the label process of curing surface coating with UV or electron beam, the ink used is very important

(5) silk printing is suitable for making transparent labels that need background color or large field area

the printing characteristics of in mold labels are as follows:

1 When designing the in mold label used as the surface of the container, the shape of the trademark should be determined according to the outline of the container to be coated, and the thickness of the label is about 60 μ m-100 μ M

2. The requirements of in mold label for paper feeding and tension control mainly focus on reducing the deformation of label material. The printing machine should be equipped with an automatic material tension control device to make the material tension even during the paper feeding process, so as to ensure the accuracy of label overprint. Excessive paper feeding tension will deform the label material, and eventually lead to the bending of the label in the running direction of the machine. The paper core tube of label material raw material should be larger (such as 152mm). The larger the diameter of the paper core tube, the smaller the bending deformation of the material near the paper core, which can improve the deformation of the label after processing

3. The combination degree of film material and ink is mainly determined by the surface tension of the material. In order to ensure high-quality printing quality, label materials are generally corona treated. The surface tension of the label material is lower than 40 × When 10N (40 dyne) -5n (40 dyne), corona treatment must be carried out to ensure the adhesion fastness of the ink on the label material. The surface tension of the label material is greater than 40 × When 10N (40 dyne) -5n (40 dyne), corona treatment can be avoided. After all, corona treatment also has a negative effect. This process will generate a lot of static electricity on the surface, making it difficult to peel off the label

4. Common film in mold label materials are relatively soft, and most of them are stacked when labeling, which is easy to generate static electricity. Labels with static electricity will lead to irregular stacking, and labels cannot be separated smoothly, resulting in inaccurate labeling positions and double sheets. Therefore, electrostatic eliminators should be installed on printing, die cutting, waste discharge, label cutting, label stacking and other stations to reduce the static electricity carried on the finished label. Proper temperature and humidity can also reduce the generation of static electricity. Therefore, the temperature of the printing workshop should be kept at 21 ℃ ± 2 ℃ and the relative humidity should be kept at 50%

when installing the electrostatic eliminator, the position should be 1mm-1.5mm away from the material surface. Thickness not exceeding 178 μ M material is generally installed with an electrostatic eliminator. Thickness over 178 μ M, it is better to install an electrostatic eliminator on the back of the material. The positions of the two electrostatic eliminators should be staggered from left to right, and do not install them face to face

5. Choose the right ink and polish to improve the scratch resistance of the label. Offset printing should use fast drying non skinning inks, such as pop, TSP inks, etc., and the quality of UV ink printing is better. Embossing and flexo printing mostly use UV ink, which dries quickly and the ink color is bright

6. First determine the front and back of the label, that is, the printing surface and the surface of the adhesive. During the inspection, the surface tension of the material can be checked, or the method of wiping the film surface with solvent can be used for identification

7. According to the shrinkage deformation ratio of the film, the label arrangement direction of the label should be parallel to the machine direction to minimize the deformation of the label

9. The amount of offset fountain solution is 10% - 15% less than that of general offset printing methods, as long as the plate is not dry. Excessive amount of fountain solution will cause false drying in printing and emulsification of ink in the face of global environmental and energy constraints. The pH value of fountain solution should be controlled at about 6-6.5

post processing of in mold labels