At present, the production process of Bopp laminating film mainly includes tube film method and flat film method. The tubular membrane method is a two-way one-step stretching method. The flat film method is further divided into two-way one-step stretching and two-way two-step stretching.
The tubular film method is to stretch the longitudinal and transverse directions of the Bopp laminating film while blowing the bubble tube. The principle of the method is to first extrude a tube to a thickness of 40 to 50 times that of the film product, and then cool the tube with a water bath. In fact, the biaxial stretching of the method occurs when the second bubble is formed, and the bubble is formed between the first and second pairs of the nipples under appropriate pressure adjustment, and the longitudinal stretching is driven at a relatively fast speed. The second pair of clubs came to achieve. According to the manufacturer of the printed cat network consumables, the production process of the film-membrane method has the advantages of simple equipment, low investment, small footprint, infinite material loss, and simple operation. However, due to the shortcomings of low production efficiency and large product thickness tolerance, it has hardly developed since the 20th century and is currently only used to produce special varieties of Bopp laminating film.
The flat film method of the Bopp laminating film production process is to first form a melt or solution of a high molecular polymer into a sheet or a thick film through a narrow machine head, and then in a dedicated stretching machine at a certain temperature and setting. The Bopp laminating film is formed at a constant speed, simultaneously or in two directions (longitudinal, transverse), and is subjected to appropriate cooling or heat treatment or special processing. The Cat Network Expert Advisory Group pointed out that this production process can evenly balance the longitudinal and transverse mechanical properties of the Bopp laminating film, and can also intentionally produce films with different properties in the longitudinal and transverse directions.
The tube film method of the production process of Bopp laminating film is inferior to the flat film method production process in various comparisons. How does the specific situation of the disadvantages manifest? The manufacturer of the cat network summarized these points: low shrinkage, poor uniformity of thickness, inability to precisely control temperature and draw ratio, and low heat seal temperature resin problems.
The bonding force between the substrate (BOPP) and the hot melt adhesive (EVA) constituting the laminating film (indicated by "heat sealing strength"), in the processing process after the composite of the printed matter and the laminating film (such as rolling line, bump After the treatment, and the use of the printing process plays a very important role, only if the heat sealing strength reaches a certain value, the delamination of the substrate and the hot melt adhesive layer will not occur, so as not to affect the appearance quality of the printed product. How to get the desired effect, in the normal production process, the EVA melt casting contact with BOPP, the time is short, the temperature is not high enough, the bond between the two is almost zero, so two The bonding force between the two is also almost zero. Through the adjustment experiment of the process parameters of the relevant process parts in the pre-coating process, the ideal bonding force (heat sealing strength) can be finally obtained.