In film production, the choice of raw materials such as stabilizers, resins, plasticizers, lubricants and fillers has a great impact on product quality. So how do they affect the production of PVC film?
1. Plasticizer: Plasticizer is one of the important additives in soft film formulation. The amount of calendered film is large and there are many varieties. Typically, 25 plasticizers are used simultaneously. The most commonly used is dioctyl phthalate, or DOP, suitable for use with DBP, DOA, DOS, and M-50 (besylate of petroleum) in amounts of 40 to 50 PHR. The amount of plasticizer for the blown film is lower than for calendered film, typically 3040 PHR. DOP is the main variety, with epoxy ester and M-50. When selecting plasticizers, pay attention to the difference in plasticizing efficiency of different varieties, and the total plasticizing efficiency should meet the requirements of product softness. At the same time, the use of the film, combined with the health and toxicity of plasticizer varieties, ensures the environmental protection, safety and health of the product.
2. Lubricant: Due to a large amount of plasticizer in the formula and the high lubricating efficiency of some stabilizer components, the amount of lubricant added in the PVC soft film formulation is less, so it is not as important as the hard product. It is usually dominated by stearic acid, and sometimes wax lubricants can be added to blown films to improve surface gloss.
3. Stabilizer: The type of stabilizer is mainly selected according to the film's stability, processing method and transparency requirements. The transparent film usually chooses organotin, transparent calcium-zinc composite stabilizer and transparent rare earth stabilizer. The main types of opaque films are lead salt stabilizers and metal soap stabilizers. Metal soap stabilizers commonly used in calendered films are barium cadmium, barium cadmium zinc, barium lead, etc., which are composite stabilizers.
4. Polyvinyl chloride resin: Due to the large content of plasticizers in the formula, it is necessary to choose a high molecular weight suspending resin with good plasticizing energy to suspend. Typically Sg-2 and SG-3 resins are chosen. Indicators, in addition to resin plasticizers, have higher numerical requirements for the absorption of 100g of resin, and should also choose less volatile matter, low "fish-eye" number, uniform particle size, and apparent density of the resin.
5. Other additives: In the blown film formulation, calcium carbonate and diatomaceous earth are appropriately added to improve the opening rate. In colored films, pigments are also necessary, but the varieties suitable for PVC need to be selected. In some products with higher weatherability requirements, the formulation will add additives such as antioxidants and light stabilizers.
6. Filler: Calcium carbonate is the most commonly used filler in PVC opaque films. In general, choose varieties with uniform particle size and small particle size. When the dose is large, most should be treated by conjugation. In addition, the film is also used to fill kaolin, red mud, etc.