Discussion on labeling and injection molding proce

Discussion on labeling and injection molding process of in mold labels

1. Uniqueness of in mold labeling

* in mold labels are located in the bottle arm of plastic containers, while other labels are on the surface of containers

* can withstand multiple impacts from plastic bottle molding, filling to packaging

* adhere to the container from the beginning of processing, and then enter the filling process to support Yantai in building a world-class chemical new material 1 integrated industrial zone, bottle washing, packing and transportation

2. There are two ways of labeling in the mold: blow molding for bottle processing and injection molding for box processing

blow molding process

I. blow molding process

the semi molten cylindrical hollow plastic material is extruded by the extruder, and the plastic resin gradually falls into the mold. At the same time, the mechanical arm (i.e. the suction cup inside the mold) sends the label to the inner wall of the mold for fixation, the mold clamps the semi molten cylindrical material, and the air enters to expand and form the container. After the pressure is released, The resin material can be processed into the shape of the required mold

II. The main application of blow molding bottle body

is mainly used for liquid packaging products. Finally, such as shampoo, rubber washing products of kitchen and bathroom products, cosmetics, chemical products and medicine bottles, as well as fruit juice bottles and personal care products. 95% of the in mold labeling production in North America adopts blow molding process, while the vast majority of European products adopt injection molding process due to short production cycle, small batch size, and consumers' critical taste for products

III. blow molding process

1. During blow molding, the back of the label is brushed with a layer of heat sealing coating. The liquid adhesive or coextrusion adhesive coated for the label factory is added to the film during the extrusion process. This coating can be melted during blow molding and then adhered to the plastic bottle body. It is suitable for polyester bottles and various PE and PP bottles

2.1000ml hollow plastic containers (such as shampoo, shower gel, detergent, etc.) have light weight and short cooling time. They can be dropped immediately after opening the mold. There are no other products between the two half molds when labeling, and then re calibrate the sensor to work normally. There is plenty of space, and various forms of mechanical arms can enter the mold for labeling

3.ml and other large hollow plastic containers (such as clothing softener, lubricating oil, antifreeze, etc.), due to the heavy product and long freezing time, the conditions such as mold opening distance, mold depth and external cooling must be considered

labeling process

in order to prevent labels from rubbing and generating static electricity due to shaking during transportation, it is recommended to use special cartons for packaging; In order to ensure the flatness of labels, rubber bands should not be used for binding

first, discuss the labeling methods in detail by classification

1. Vacuum adsorption method

this is the most common and widely used method at present. A vacuum pump (i.e. vacuum suction cup) is installed behind the mechanical arm of the labeling machine. The mechanical arm absorbs the label in a vacuum manner and sucks up the label by applying negative pressure. Plastic packaging products enterprises can add vacuum micropores on the original mold by themselves, without special equipment, low cost and good use effect

2. Electrostatic adsorption method

in the blow molding process, there is also the electrostatic method of labeling in the mold, which relies on the instantaneous static electricity generated by the manipulator to adsorb the label, but compared with the vacuum adsorption method, it is technically difficult and has poor stability; The label is prone to uneven surface. The electrostatic adsorption method has special requirements for the physical properties of in mold labeling equipment and labels:

a. add an electrostatic elimination system on the equipment to eliminate the residual static electricity after each labeling, so as to avoid its impact on the electrical control system of in mold labeling machine and the label adhesion caused by static electricity, so as to ensure that only one label is produced each time and improve the yield

b. add a high-voltage electrostatic distribution system on the equipment to evenly apply enough electrostatic charge to the label in a short time, and stick the label on the inner cavity of the blow mold at zero potential through the manipulator

c. select appropriate label substrate and printing ink

II. The influence of the shape of plastic packaging products on the labeling accuracy

1. The most common cross-section of plastic containers is elliptical and fan-shaped, the fitting surface of the label is close to the arc and the radius of curvature is large, and the label fits closely with the mold. Before the plastic material is inflated, the label is not easy to produce displacement and displacement

2. Some plastic containers have three-dimensional curved surfaces (nearly spherical, such as clothing softener packaging bottles). The use of vacuum adsorption will cause frequent vibration of labels and displacement in a short time, and the smaller the radius of curvature of the surface, the more serious this phenomenon is

III. requirements for labeling effect

transparent labels require that the surface after labeling is formed is smooth and fully reflects its appearance effect, which can be achieved by selecting the appropriate mold, mold temperature and tube embryo temperature

at present, opaque labels have several effects, such as flat light, matte, cloth pattern, pearlescent, etc. users can choose by themselves according to the design requirements and formulate relevant production processes to achieve the actual effect of products consistent with the design purpose

IV. how much do you know about the labeling conditions in the mold

(1) the temperature of the die extruder is generally controlled at 165 ℃ -215 ℃ according to the production status,

(2) the label must be smoothly adsorbed on the mold wall in the mold,

(3) if the barrel is deformed after the label is fitted, it should be adjusted in time