线型低密度聚乙烯薄膜透光性的研究

Study on Light Transmittance of Linear Low Density Polyethylene Film

Unipol气相流化床工艺生产的线型低密度聚乙烯（LLDPE）的结晶度高，薄膜透光性比高压低密度聚乙烯薄膜的透光性差，影响了LLDPE薄膜的应用与推广。分析认为，降低LLDPE薄膜中的灰分含量、调整LLDPE薄膜的结晶性能，有助于降低LLDPE薄膜的雾度，提高LLDPE薄膜的透光性。实际生产经验表明，乙烯分压从0．85MPa降至0．60MPa时，LLDPE薄膜的雾度下降了3％～5％；使用高活性催化剂和优质添加剂，可使LLDPE薄膜中灰分的质量分数从4×10^-4降至1×10^-4；成核剂的使用及吹膜工艺参数的调整，可改善LLDPE薄膜晶核的形态及尺寸，达到了改善LLDPE薄膜透光性的目的。

The film of linear low density polyethylene （LLDPE）, produced by Unipol gas phase fluidized bed process, was low in light transmittance comparing with film of high pressure low density polyethylene due to high crystallinity of former. Factors influencing light transmittance of LLDPE film： crystallinity, ash content of film, polymerization conditions of resin, etc., were investigated. When ethylene partial pressure during polymerization reduced from 0. 85 MPa to 0.60 MPa, haziness of resulted film would drop 3%-5%. By using high performance catalyst and additive, ash content in film would reduce from 4×10^-4 to 1×10^-4 （ mass fraction）. By improving blow molding conditions and using nucleating agent, light transmittance of film can also be enhanced.