By Liang Tao, PetroChina Lanzhou Chemical Research Center

Nitrile Butadiene Rubber (NBR) is a synthetic rubber copolymerized by acrylonitrile and butadiene and is a typical non-crystalline oil-resistant rubber. It is mainly used as oil-resistant rubber products, modifiers, adhesives, etc., and is widely seen in the production of sealing materials, rubber tubes and other parts for industries such as machinery, aerospace, weapons, ships, petrochemicals, and automobiles.
   There have been many NBR plants in China (see Table 1), and the products have covered low-nitrile, medium-nitrile and high-nitrile series to largely meet the domestic demand. Local NBR market is developing towards product differentiation, specialization, functionalization, high performance and environmental protection. The specialty segment has grown slowly, as the limited category and quantity cannot meet the high-end demand in the civil and military rubber fields.

   Table 1   China’s NBR producers and their capacities

1. Hydrogenated NBR

   The production of hydrogenated NBR globally was about 23 kt in 2018. At present, the capacities in overseas markets are primarily held by Germany-based Lanxess, at 10 kt/a, and Japan-based Zeon, at 12 kt/a. In China, Shanghai Zannan has a capacity of 1 kt/a, actual output of 300-500 tons, based on the Zhan Catalyst that has been developed on its own. Shandong Daon Company’s newly-built 1 kt/a hydrogenated NBR unit in Longkou, Shandong uses the catalyst developed by its own proprietary technology, and the products have been put into the market gradually. Although the annual consumption of hydrogenated NBR is increasing, the limited market appetite will drive the prices down.

2. New NBR/PVC products

   NBR/PVC (polyvinyl chloride) products can be divided into two categories: blended rubber and co-sediment rubber. Blended rubber is made through a mixture of NBR and PVC, and is widely used in the production of rubber covered rollers, rubber gaskets, wire and cable jackets, oil-resistant brake rubber tubes, oil pipes and various oil seals for the textile industry. Based on latex co-precipitation process, co-sediment rubber is made by NBR latex and PVC paste or powder, after conglomeration, dehydration and drying.

3. NIBR

   Ternary copolymerized nitrile rubber (NIBR) is a special small grade. A third monomer isoprene is placed in the process of NBR polymerization so as to improve certain properties of the product while making full use of C5 resources. With 35% of the content of acrylonitrile in foreign NIBR products, they have better physical and processing properties, and they are mainly used in high-end printer rubber rollers. However, there have been no NIBR products in China yet.

4.  XNBR

   Carboxylated nitrile rubber (XNBR) is a terpolymer of butadiene, acrylonitrile and unsaturated carboxylic acids. It is a high-performance, high value-added material with superior oil resistance, wear resistance and adhesion, and outperforming mechanical properties at high temperatures. It is mainly used as aerospace adhesives, dynamic seals for mechanical equipment and high-pressure rubber tubes for oil fields. At present, PetroChina Lanzhou Chemical Research Center has completed the pilot development of XNBR, marking a breakthrough in the areas of XNBR technology and products.

5. Ultra-high NBR

   Ultra-high nitrile butadiene rubber refers to a NBR grade with the acrylonitrile content at or above 46% approximately. It is used in special products with high oil resistance and can also be used as a material for improving oil resistance when in processing. The consumption is not big, and it is a high value-added product with small output. It is worth R & D, as it is a material to blend in and modify downstream products to improve their oil resistance.

6. Powdered NBR

   At present, the domestic capacity of powdered NBR is about 20 kt/a, outstripping the local demand. Domestic powdered NBR is mainly used in the automotive brake pad market. With the development of the market, the focus should be on how to strengthen the development of functional powdered NBR, such as carboxyl powdered NBR, semi-crosslinked powdered NBR and graft modified powdered NBR. If the products are applied in niche market, the profits will be encouraging.

‍7.  Fluorinated NBR

   Fluorinated NBR is a ternary copolymer composed of acrylonitrile, butadiene and fluorine-containing monomers. As a brand-new high-end grade of NBR, it is one of high value-added products. Fluorinated NBR’s weather resistance is 10% higher than ordinary NBR. It is mainly used in defense military and high-end application fields. Lanzhou Chemical Research Center has completed the pilot technology R&D in preparations for commercial production of fluorinated NBR.
   In the future, the domestic NBR market will see more furious competition. The development of technologies and production of high value-added specialty products is bound to be a way out during the period of the “14th Five-Year Plan”. With the all-around implementation of environmental protection policies on anti-oxidant and other auxiliary products, the specialty NBR market will have breakthroughs in the coming few years, with key grades to cover local demand gradually and small high-value-added grades to develop continuously.