Cast polypropylene film production process and the domestic status quo the pha
Polypropylene film according to production method, properties and different uses can be divided into cast polypropylene (CPP) film, PP Inflation (IPP) films and biaxially oriented polypropylene (BOPP) film of three. PP polypropylene film of the world's total consumption of 20%, is second only to injection molding, fiber (including stretching) the third largest application of products, China accounted for PP consumption structure of PP films share is relatively low, only about 10%. CPP film has good transparency, high gloss, good stiffness, good wet resistance, heat resistance, excellent, easy-to-sealing characteristics of joint, and its resistance to including sexual and Packaging Machinery Applicability than Polyethylene Film, so in the field of packaging films occupy a certain position, CPP film after printing, bag, for food, stationery, groceries and Textile And other packaging materials can also be combined with other film after use, usually as a composite film of the inner and outer materials. Used in various foods, including required pasteurization of food, condiments, soups and daily necessities such as packaging. 1, CPP film production process CPP process described above generally use T type die method, this system characteristics of the method are: (1) flat membrane eliminates stage tubular film blown film method, easy to drive, waste less; (2 ) flat membrane production, PP molecules arranged in order, it will help improve film clarity, luster and thickness uniformity, suitable for advanced packaging; (3) flat membrane with a special retention tank with a die gap integrated, easy adjustment. Blow molding method and casting the production of films shown in table 1. First raw material resin melt extruder, die casting molten resin to smooth the surface of the cooling roll into a thin film on the rapid cooling. The thickness measurement, traction, corona treatment, flattened, cut side edge of thick materials, re-started and rolling paper for the film. 2, CPP film production process points T-type head is one of the key equipment of production, the nose should be designed so that the width of material along the lip evenly throughout the machine out, no head retention within the internal flow channel dead, and has a uniform temperature of materials m aterials required to considerations include the rheological behavior of materials, including various factors. To use precision machining head, commonly used type is decreasing manifold hanger head. After cooling roller surface should be finishing, surface roughness no greater than 015mm, speed should be stable, to avoid fluctuations in vertical thickness. By -ray or infrared Gauge Monitoring the film thickness to achieve a satisfactory thickness tolerances. CPP to produce qualified films, not only have good material, but also to master the processing conditions. The greatest impact on the films is temperature. Resin temperature, the film's longitudinal (MD) tensile strength increase, increased transparency, fog gradually diminished, but the film's transverse (TD) tensile strength decreased. More appropriate temperature of 230 ~
250 . Cooling the upper hand roll film and the cooling roller blade to the surface of a thin air layer, so that film uniformity cooling, thereby maintaining the high-speed production. Air knife adjustment must be appropriate, the wind can make excessive or improper angle of the thickness of instability or paste roll, resulting in the appearance of wrinkles or affect the quality of patterns emerged. Cooling roll temperature, the membrane stiffness increases, the haze increases. Cooling roller surface if the internal additives precipitated material must be clean shutdown, so as not to affect the film surface quality. CPP film relatively soft, rolling to be under the film when the thickness of factors of production adjust the speed of pressure and tension. Or will cause formation of ripple effects. Tension select products according to the size of the tensile strength is usually higher winding tension, winding drum after the product is not easy relaxation and deviation phenomenon occurs, but when at the beginning of take-up prone to ripple affect volume level. Instead, take-up tension and to begin effective, but it is getting more prone to membrane relaxation phenomena deviation. Therefore, the tension should be medium size, and constant tension control. 5, CPP film applications and development trends CPP film variety, a general single layer membrane, composite membrane, low temperature heat sealing film, low thermal seal film, low-temperature impact-resistant film, anti-static film, high-temperature cooking film, general cooking film, metal vapor deposition, bread packaging films, Vegetables Packaging film, fiber packaging films, containers, composite membrane, the longitudinal easy to tear film. CPP film composite membrane and cooking to packaging as the main market, Japan CPP film composite with 50% of the total amount. CPP film as good heat resistance, cooking package is to play its specialty areas, the two areas of application are also growth markets. Composite coating is mainly used in food packaging, demand growth is also faster than the relatively slow growth in food packaging. Packaging development because of the sub, small bag of personal use of packaging, convenience and fresh direction conducive to the development of CPP film and its applications. The oxygen barrier coating of metal vapor, moisture, UV cut off good, with growth and growth barrier packaging, and metal evaporated PET film ratio, overall performance is poor, but cheap, for small packages. Metal vapor deposition on crops, small products, livestock processed food packaging applications were stable and moderate growth, while bread, bags of fiber packaging and specifications application declines. Application of CPP film composite membrane from the monolayer to the direction of, LLDPE with a sealing film with the main material, CPP in the heat resistance, stiffness, moisten better than LLDPE, but the high melting point temperature caused by poor sealing and resistance to disadvantage of poor impact properties, need to develop high-quality resin and modified CPP were out of technology to solve. CPP film challenges facing the development of other materials, and competition can not be said to be very optimistic about the prospects, such as the successful development of heat-
resistant grades of LLDPE and metallocene catalyst (single site) produced more than LLDPE grades, performance different, able to satisfy user requirements.
