Brief introduction of the advantages of paper-plastic composite products
Paper-plastic composite products require firm adhesion, clean, smooth, smooth surface, no blistering, curling, no loss of film, film out, etc. There are many factors that affect composite quality, both objective and subjective. It involves the environmental factors of the operating place (indoor temperature, humidity, dust, etc.), as well as the factors of the product itself (inks, paper types, printing methods, etc.), and adhesives and films used in combination with paper and plastic As well as the process conditions, operation methods and the structure and technical performance of the laminating machine are closely related, a comprehensive analysis is required.
1. Bonding fastness of composite products
The factors that affect the adhesion fastness of the composite products are: the adhesion of the glue itself, the affinity of the glue with the film, paper and ink layer, the state of the glue layer, and the operating process conditions.
1. The adhesive strength of the glue depends on the production process formula of the raw material machine of the glue and the solid content of the laminating glue. Some products have better adhesion after compounding. After a period of time, the film peels off, that is, the film is detached from the paper, and the film is peeled off by hand. It is even separated with a fingernail. When the surface is detached, either fold the composite product toward the film surface, and the film is detached from the paper surface at the crease, or curl the composite product toward the film surface, which also causes the film to detach from the paper surface. These phenomena prove that the adhesive force of the adhesive is invalid due to the influence of external natural conditions.
2. The influence of the affinity of glue and film on the compound fastness
The chemical structure of the polypropylene film used for compounding does not have active genes, and it is a non-polar substance, which has poor affinity for glue and causes difficulties in surface adhesion. Therefore, the film should be corona treated to make its surface products unsaturated double bonds and carbon groups, so that its surface energy has active genes, and as a result, the surface roughness of the film increases, which is beneficial to the coating of glue. When the corona-treated film changes the properties of the film surface, it changes from a non-polar substance to a polar substance, which is beneficial to improve the affinity between the adhesive and the film. However, the corona-treated membrane has a time limit, which will subside after a long time. The information is 6 months. The surface tension of the failed membrane is reduced, and the information is lower than 39 dynes / cm2. How to distinguish the inside of the corona of the film and whether the corona treatment has failed? Two methods are introduced here.
(1) Use a fountain pen to write or scribble on the film surface. The side easily stained with ink is the corona treatment surface. If the water does not shrink or form beads, and it is not easy to wipe off, it means that the corona treatment surface has not failed.
(2) Use 38Mn / m surface tension indicator: 54g formamide, 46g ethylene glycol ether, and then test. If the indicator does not shrink by itself within two seconds, the corona treatment is considered qualified.
3. The influence of the affinity of glue and paper on the compound fastness.
Paper is a kind of porous material interwoven with plant fibers. It fills the holes and improves the water resistance of the paper through sizing to make up for the depressions on the surface. In order to improve the flatness and smoothness of the surface, a layer of paint is applied on the paper surface, which is made by calendering or super calendering.
There are many types of paper used in printed products. Generally, white cardboard, coated paper and glass cardboard are used for laminating. Classify them. One is that the paper structure is relatively tight and the surface is relatively flat, such as coated paper and cellophane. The other is that the paper structure is relatively loose and the surface is rough, such as whiteboard. Its internal structure is similar to the first category, and its surface condition is close to the first category. When the adhesive layer and the paper are compressed and combined, the compound fastness to the paper with poor surface smoothness is worse. The high point of the paper surface is combined with the glue, while the low-lying area is not glued to the glue, and the glue layer and the paper surface are combined in the form of point contact. For paper with high surface smoothness, the composite fastness is higher. The adhesive layer and the paper surface are basically combined in the form of point contact, and more glue is in contact with the paper surface. For paper with loose structural adhesive, the paper wool is easily taken away by the adhesive layer after peeling off. Therefore, the size of the glue should be adjusted according to the paper during use to fill the uneven surface of the paper and improve the adhesion fastness.
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