By Guo Lingyan, CNCIC

Metallocene polyethylene is an interpolymer of ethylene and α-olefin with metallocene as the polymerization catalyst, and the product density and comonomer content can be varied within a wide range. Metallocene polyethylene is significantly different in performance from polyethylene polymerized with conventional catalysts, with better texture, ductility, clarity and toughness.

   Metallocene polyethylene is difficult to process and generally needs to be blended with ordinary polyethylene. m-LLDPE is one of the most commonly used types, mainly for various metallocene products with a density in the range of 0.915-0.925 g/cm3 and a melt flow rate (MFR) at 1.0. According to incomplete statistics, China's m-LLDPE accounts for about 16% of the national LLDPE market demand.

Only 4 companies have industrial production

   At present, only Sinopec Qilu PC, China National Chemical Corporation Shenyang Chemical Co., Ltd., PetroChina Daqing PC, and PetroChina Dushanzi PC have realized industrialized production of m-LLDPE, all being C6 copolymerization due to the fact that the raw materials of C6 copolymerized m-LLDPE are more easily available and have advantages in terms of product performance and production cost. In 2018, the domestic production was about 350 000 tons, and the operating rate was less than 40%, of which 84.4% was PE-RT pipe, and 15.6% film products. The product types and technology sources are shown in Table 1.

   Table 1   China's m-LLDPE production company in 2018

   China’s m-LLDPE PE-RT pipes are basically produced with self-developed technology while films are produced with Univation technology. Among the above four companies, three have independently developed PE-RT pipes and realized large-scale and stable production: Qilu Petrochemical produced more than 100 000 tons of PE-RT pipes in 2018, accounting for 50% of the national total; Daqing Petrochemical achieved batch production of PE-RT pipe in 2017, with an output of more than 10 000 tons in 2018; Dushanzi Petrochemical successfully developed PE-RT pipe in 2017 and realized batch production in 2018. However, film-grade m-LLDPE is still in the trial production in China. The high price of imported catalysts and the instability of product quality have curbed production enthusiasm.

High import dependency

   In 2018, China's m-LLDPE consumption was about 1 million tons, of which C6 copolymerization accounted for 87.4% and C8 copolymer products 12.6%; and of which domestically produced m-LLDPE only took 12% with the rest imported.

   From the perspective of consumption, m-LLDPE is mainly applied to food packaging, industrial packaging, agricultural film and PE-RT pipe in China, accounting for 94.9% of the total consumption of m-LLDPE. At the same time, C6 m-LLDPE and C8 m-LLDPE have different consumption sectors: C6 m-LLDPE's main applications are industrial packaging, food packaging and PE-RT pipe, while the main applications of C8 m-LLDPE are food packaging and industrial packaging.

   1. Industrial packaging

   In China, industrial packaging is the main consumer of m-LLDPE, accounting for 37% of total consumption. m-LLDPE has good tear resistance, good puncture resistance, low temperature sealing and good impact resistance, and is thus commonly used in the production of FFS film, heat shrink film, stretch wrapping film, industrial packaging lining, medical packaging and garbage bags. 

   In industrial packaging, m-LLDPE is mainly used in the production of FFS membranes. Form, film & seal film (referred to as FFS film) is a film that has been developed in China for heavy-duty packaging in recent years and is mainly used for automatic packaging lines of large-scale synthetic resin products. In order to ensure the strength and heat-sealing performance of the film, the raw material m-LLDPE is added up to 50% for FFS film.

   2. Food packaging

   Food packaging is the second largest consumer of m-LLDPE in China, accounting for approximately 29% of total consumption. m-LLDPE has excellent toughness and strength, and its film product can be thinned, thereby reducing raw material cost, processing cost and transportation cost. In addition, m-LLDPE can be combined with BOPET, BOPP, BOPA and other films to make high temperature steaming and cooking bags, vacuum bags, etc., especially suitable for packing meat, convenience food, frozen food, etc. It has excellent low temperature sealing performance and can hence improve the production speed of the automatic packaging machine to a certain extent and is thus suitable for the high-speed bag production line.

   3. Agricultural film

   The agricultural film sector accounted for 8.4% of total consumption. At present, the main types of agricultural film on the market are: ordinary agricultural film, PE functional film, EVA functional film and PO film, among which PO film is the development trend of the agricultural film market.

   In general, the addition ratio of m-LLDPE in PO film is fixed, at about 50%. The advantages of PO film are: reducing pests and diseases, suitable for pollution-free vegetable production, strengthening thermal insulation performance, anti-static, non-sticky, long service life, and moderate UV permeability.

   4. PE-RT pipe

   PE-RT, namely heat-resistant polyethylene, retains the excellent flexibility of PE and improves its heat resistance. At present, PE-RT pipe accounts for 70% to 80% of the domestic floor heating pipe market, while the most important raw material of PE-RT pipe is m-LLDPE, which takes 20% of the total domestic m-LLDPE consumption.

   A series of downstream applications of m-LLDPE have already been common in Chinese people’s daily life. With the breakthrough of domestic production technology, the price gap between m-LLDPE and ordinary LLDPE will continue to decrease in the future, which will further expand m-LLDPE applications.