In the production of BOPP film, both semi-finished products and finished products must be wound on the coiling core. Because the film is thin and the winding is tight, it will lead to the possibility of adhesion between the films. When the surface layer of the film (anti-viscosity agent is usually added to the surface layer of the film) adds a certain amount of anti-viscosity agent and polypropylene resin insoluble, due to its particle size is 3 ~ 5um, and the surface thickness of the film is generally 1um, convex exposed on the surface of the anti-viscosity agent between the film formed an air isolation layer, to play the role of anti-viscosity.
As the anti-blocking of BOPP film, it must have good anti-viscosity, and dispersion, be non-toxic, and have a close refractive coefficient with polypropylene resin. At present, there are inorganic and organic anti-blocking agents in the domestic and foreign BOPP market. Inorganic anti-blocking agents mainly include synthetic silicon dioxide, synthetic China clay, glass beads, calcium carbonate, and so on. The shape of this kind of anti-adhesive is irregular or round, the particle size is about 3 ~ 5um, transparent, sensitive to moisture, in addition to silicon dioxide is hard, another hardness is moderate, in addition, anti-blocking agents have a high surface area, conducive to the absorption of other additives, this aspect of silicon dioxide anti-adhesive performance is slightly obvious.
Organic anti-viscosity agents are new varieties developed in recent years, among which the more typical products are silicone polymers, such as polysiloxane polymers. This kind of anti-stick agent has the function of anti-stick and slippage, the particle size is about 4um, round, transparent, softening temperature or melting point is low, and is not sensitive to moisture and other additives adsorption.
According to the raw materials used in the product, BOPP anti-stick agent can be preprepared with polypropylene homopolymer, polypropylene copolymer, and even slippery agent to make masterbatch, the concentration is generally 2 ~ l5, with a low concentration of its better dispersion.