Perspective in-mold labeling technology
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
In-mold labeling has been in Europe, America and the United States for more than 20 years. In recent years, this new labeling technology has been rooted in China, and is used in oil, daily use, food and pharmaceutical industries.
What is an in-mold label? It refers to special label paper made of PP or PE synthetic paper on the surface and coated with a special hot melt adhesive. The printing is made into a trademark. Use the robot to pick up the printed label and place it in the mold. The vacuum hole on the mold attaches the label firmly to the mold. When the raw material of the plastic bottle is heated and drooped in a hose shape, the mold with the label is quickly closed, and the air is blown into the hose to make it close to the mold wall. At this time, the temperature in the entire mold is relatively high, and the bottle body is tightly attached to the bottle body. The prototype label-shaped adhesive begins to melt and bonds with the plastic bottle in the mold. Thus, when the mold is opened again, the plastic bottle is formed into a body, and the label and the bottle body are integrated into one body. The printed trademark is firmly embedded in the surface of the plastic product. The label and the plastic bottle are on the same surface, and there is no label on the surface. The color image is printed directly on the surface of the bottle.
This kind of packaging effect without labeling is favored by consumers. This article will introduce the main techniques involved in in-mold labeling techniques.
First, Materials
The technical content of the in-mold label is very high, and the first thing that comes out is the material. The earliest entry into the Chinese market was the Japanese YUPO in-mold label, which claimed to be the most successful in-mold label material in the world. Now, the French Polyart blown mold internal standard has also entered the Chinese market, and some local enterprises are also stepping up research and development of this material.
The in-mold label must first have good printability, and ensure that the ink is firmly attached to the surface. The post-processing process should ensure good processing suitability, such as die-cutting and cold stamping processing. Secondly, this material should meet the special characteristics and be combined with the plastic bottle during blow molding.
Printing surface
middle layer
Adhesive layer
The structure of the in-mold label material, the intermediate layer of the printing surface, the adhesive layer
In-mold labeling materials are divided into two categories: paper and plastic film. The former will change shape when exposed to water or moisture, but its advantage is that there is no static electricity interference, which reduces the loss of the label when blowing the bottle. In addition, it is not the same material as the plastic bottle, and it is not convenient for recycling. Nowadays, plastic film and plastic in-mold labeling materials are generally used inside and outside the country.
The in-mold label material structure consists of a printing surface, an intermediate layer and an adhesive layer. The function of the printing surface is to accept the ink and form a color picture; the middle layer supports the printing surface to give the material sufficient stiffness and transparency, and it does not change shape on the printing machine and high temperature, ensuring accurate printing. The adhesive layer will melt at high temperatures, allowing the label material to be integrated with the plastic container, ensuring that the label and the plastic bottle are firmly bonded together.
There are three types of printed surface materials: PE, BOPP and PE +PP. Since most of the plastic containers currently belong to PE materials, the use of PE in-mold labels is more conducive to recycling, because they are all homogenous materials. In order to improve the ink affinity of the printed surface material during the production of the in-mold label, it is generally necessary to apply a surface coating or to increase the surface energy by a corona discharge method.
There are two structures on the surface of the adhesive layer: flat no-mesh structure and textured structure. The former is directly in contact with the blank when in use, and naturally vents, suitable for the small area label. The latter embossed the textured structure on the surface, and when the gas was used, the gas was exhausted through the exhaust passage of the mesh to avoid the production of the bubble. The adhesive layer also has anti-static properties to prevent double sheets during printing. In addition, it has a sliding property to ensure smooth separation of the labels, so that the printing process can be carried out smoothly.
Second, Printing of the in-mold label
Different printing factories can choose different printing processes according to their own equipment. Offset, flexo, embossing, and gravure printing can be used to print in-mold labels, currently with both offset and flexo printing.
1.Offset printing
The advantage of offset printing on the fine mesh printing side is ten points, but the line, the solid printing effect and the printing saturation are not comparable to other printing methods. Offset printing can't be done with Inline printing as a soft print, so you must perform offline die cutting, cold ironing, glazing, etc. after printing. However, the offset printing is suitable for the printing of small batch labels, and the cycle is short and flexible.
2. Intaglio
Solid printing and printing color saturation is better than offset printing, which is not suitable for printing small dots and layers of trademarks. However, the color difference control is more convenient. On the gravure press, the in-mold label material has a longer path than the other printing methods, so the static electricity is larger. The gravure plate has a high cost and a long cycle, so it fits into the long version of the in-mold label.
3. embossing
The embossing is suitable for printing the solid and line marks, and the effect of printing small dots is not ideal. The color difference control of the same batch of products is also easier, but the ink bar will appear. From a cost perspective, it is cheaper than both gravure and flexo.
4. Flexo printing
The highlight of the flexible version of the printing is that the printing and finishing process can be done in one go. The front end is the feeding end, and the rear end is finished with the final printing product, which realizes the printing and post-processing connection production. Now, with the improvement of flexographic plate making technology, the printing quality of dot printing has been greatly improved. The in-mold label has been approved by some manufacturers for flexo printing, but the printing with environmentally friendly water-based ink is still immature. It is a highly mobile UV ink and has become the trend of in-mold label printing.
Third, Post-processing of the in-mold label
After the in-mold label is printed, the finishing procedure such as glazing, bronzing, and die-cutting is performed according to the customer's requirements.
1.Polishing
In order to improve the gloss of the in-mold label and the surface decoration characteristics of the product, the in-mold label after printing can be glazed to improve the wear resistance and high temperature resistance of the in-mold label. When labeling, if vacuum adsorption in-mold label is used, antistatic agent should be added and the smoothness of varnish should be added properly. If electrostatic labeling is used, the varnish should not be added with antistatic agent; If the inner label needs to be bronzing, it should be gilded with UV varnish. If the varnish is added with additives, it should be tested before glazing to avoid scrapping the entire batch.
2. Hot stamping
The hot stamping on the in-mold label material can be used for different hot stamping processes after first hotening or over-oiling. Hot stamping can use both cold and hot stamping techniques.
Cold bronzing is mainly used for flexographic printing. The use of cold stamping to obtain better visual effects requires higher process technology. We recommend a process of printing after cold ironing, so that a thicker layer of ink can be used to cover the edge of cold stamping. glitch. This technique is recommended if the customer is able to accept the visual effects of cold ironing.
For the hot stamping of the in-mold label, the influence factors include anodized aluminum, bronzing temperature, bronzing pressure and bronzing speed. When hot-hot, the hot-melt foil with the hot-melt adhesive melting point lower than the hot-melt adhesive melting point of the in-mold label material should be selected, and the hot stamping pressure and time should be strictly controlled to avoid the concave and convex deformation of the in-mold label material. In the case of hot stamping, firstly, the material characteristics of the in-mold label and the bronzing suitability of the electro-aluminum are preliminarily adjusted. The size of the bronzing plate and the bronzing speed are adjusted to determine the bronzing temperature and the bronzing pressure. First, the pressure is adjusted, and then the bronzing temperature is determined. In general, bronzing can increase the added value of the in-mold label.
3. Die cutting
The die-cutting of the in-mold label is very similar to that of the Poke card, which is a cut-off die-cutting. Since the die cutting is the last processing step of the in-mold label, the static electricity removal during die cutting is very important, because the static electricity removal is unreasonable and causes the stacking to be untidy, which leads to problems such as inaccurate labeling position and double sheeting.
The die-cutting of the in-mold label is divided into two types: single-sheet die-cutting and roll-to-roll die-cutting. The specific method used depends on the manufacturer's equipment and the type of in-mold label material. In these two die-cutting modes, the roll paper die is divided into an inline die cut and an offline die cut.
The flat paper flat die cutting method is suitable for the inner mold label material of the reel. This is an off-line die cutting method, and the die cutting precision is very high. It has two types of paper conveying, one is intermittent paper feeding, the die cutting device is only for upper and lower movement, and the other is continuous paper feeding. The die cutting device not only moves up and down, but also moves forward and backward. The labels after the two work-mode die-cuts are sent to the stacking station via the transfer belt.
The round paper circular die is suitable for the inner label of the roll. There are two types of die cutting: wire die cutting and off-line die cutting. Circular die cutting is the most perfect die-cutting method. Its die-cutting precision is very high, but the cost of making die-cutting rolls is high, and it is suitable for long-lived in-mold labeling of more than 100,000 sets. This die-cutting method is used in the flexible printing process for wire-to-line processing, which is highly efficient and relatively popular in the United States.
Sheet-fed flat die-cutting is suitable for sheet-fed die-cut labeling materials. This is an off-line die-cutting method. The processing precision is general. The paper is fed by the automatic paper feeder, and the paper is automatically discharged after die-cutting. Place it on the stacking station.
Fourth,In-mold labeling method
After the die-cutting is formed into a label, the robot is sucked into the cavity one by one, and the label and the plastic bottle are melted into one body by using the extruded plastic temperature and the suction air pressure. Now, there are two ways to label the in-mold: vacuum negative pressure suction and static electric suction.
The vacuum mode is the most common and widely used method in the past. The plastic packaging company can add vacuum holes to the original molds, no special equipment, low cost, good effect, and no easy to detect the vacuum mark. This technology has been very mature.
The static mold suction method realizes the in-mold adsorption label. The biggest advantage of this technology is that there is no need to change the original blow molding equipment, but there is no successful case in China that has actually been put into use. Static electric suction type has special requirements on the physical properties of in-mold labeling technology equipment and labels:
1) A high-voltage static power transmission system must be added to the equipment. The static load should be evenly applied to the label in a short period of time, and the label should be attached to the cavity of the blow mold at zero potential through the mechanical arm.
2) An electrostatic elimination system must be added to the equipment to eliminate residual static electricity after each labeling, to avoid affecting the internal control system of the labeling machine and the labeling of the label due to static electricity.
3) Appropriate label base and appropriate printing ink must be selected.
Fifth, Advantages of in-mold labeling
1.Appearance
The in-mold label and the plastic container are formed in one shape, and the corners of the label are not visible on the plastic bottle body. The appearance is very beautiful. Secondly, because the impression of the in-mold label is good, it is suitable for printing the original and the fine draft, so the visual expression is very strong. Since there is no corner in the in-mold label, there is no such thing as "cursor" and "drop" as no glue. In the wet and humid environment, the in-mold label will not bulge and will not mold.
2. Anti-counterfeiting
At present, there are only a few companies in China that offer in-mold labeling and labeling services because of the large amount of investment in one-time equipment. In the mold design, label printing and processing, labeling and forming process contains many variables, so the in-mold label is stored in the technical barrier, it is not an easy task to fake and copy the trademark. Nowadays, the self-adhesive label is very mature, the fraud is easy, and the cost of making fakes is low. Therefore, the fake products are popular and damage the interests of the producers. The in-mold label was used to allow the manufacturer to eat the anti-counterfeiting centering pill, and it was finally possible to breathe a sigh of relief.
3. Reuse and reuse
The in-mold label material and the plastic bottle belong to the same material. After the consumer uses the product, the plastic bottle can be crushed and recycled. The recycling efficiency is high and the cost is low. It belongs to the green environmental protection packaging material. If it is a non-dry label, the recovery is more troublesome. It is necessary to tear off the adhesive label, remove the adhesive on the bottle, and then recycle it, the efficiency is low, and the recovery cost is high. Therefore, the in-mold label conforms to the development trend of green packaging.
Sixth, Application of in-mold labeling
From the perspective of development at home and abroad, the in-mold label is mainly used in the following industries:
1. Oil industry: Plastic container packaging including lubricant oil, gear oil, antifreeze and other products.
2. Daily product industry: packaging products such as bath gel, shampoo, detergent, decontaminant and personal care products.
3. Food industry: Soy sauce, ice cream, coffee, fruit juice, tea, sour milk and other products.
4. Pharmaceutical industry: high-grade medicine packaging
Although the time of the in-mold labeling is not long, it is attracting more and more manufacturers. In Europe and the United States, the development of in-mold labels began to enter the stable development track; in the country, the in-mold label is developing at a high speed of 70%. In the future, the in-mold label will launch a strong challenge to the non-adhesive label, and will eliminate the paper-based in-mold label and complete the development of the plastic label. Moreover, the number of end users using in-mold labels will increase.