Technology

Technology History

High-pressure autoclave polyethylene technology was developed by ICI in the United Kingdom. A pilot plant was built in 1937, but construction of a full-scale plant was postponed due to the intensification of the war with Germany. However, in response to strong demand as it was ideal as a high-frequency insulating material for radar, operations began in 1942^[1]. 

In 1954, an ICI research team came to Japan to license its technology to Sumika. A contract was signed in 1955, and production began in 1958^[1]. 

The Swing Production of Ethylene-Vinyl Acetate (EVA) and Low-Density Polyethylene (LDPE) technology was subsequently further developed by Sumitomo, that has since then awarded 11 licenses and has been supplying clients world-wide through its own production facilities in Japan, Singapore and Saudi Arabia^[2].

Dual Reactor System

Today, the process is only licensed as a proprietary dual-reactor system with an intercalated heat exchanger as described in US4123600^[3.a] and US4271280^[3.b], which Sumitomo claims to be the only existing process with a dual reactor cascade^[2], allowing for the the reaction conditions to be made somewhat milder, resulting in stable operation and less decomposition incidents. The dual reactor system also has a comparatively lower investment costs and consumes less feedstock and energy compared with the single reactor process version, operating costs being reduced by almost 20% (15% lower cooling water, 20% lower electrical power consumtion)^[2].   

In 2024, Sumitomo announced a collaboration agreement with Lummus Technology as the exclusive and worldwide licensor of the Sumitomo EVA/LDPE Technology^[2]. 

The process—branded Hyperlene™— by Lummus Technology, is depicted in the attached illustration (showing one single autoclave reactor) and described as follows^[4]:

• Ethylene is compressed from battery limit conditions to intermediate pressure. It is mixed with recycled monomer and (when producing EVA) vinyl acetate as comonomer.
• The monomer is then further compressed to operating pressure (1,200 – 2,000 barg) in a secondary compressor.
• The monomer mix is cooled and fed to the first autoclave reactor in multiple positions and a reaction initiator (typically, an organic peroxide) is injected into the reactor at various positions to initiate the radical polymerization reaction to form polyethylene (LDPE or EVA).
• A chain transfer agent is applied to control the molecular weight.
• The reaction is exothermic and the reactor operates adiabatically.
• After the first reactor, the monomer/polymer mixture is cooled down before it enters a second autoclave reactor along with the monomer and initiator to maximize the conversion of the monomer.
• The monomer/polymer mixture then is reduced in pressure to intermediate level and enters the high-pressure separator where the majority of monomer is recovered and returned to the inlet of the secondary compressor.
• The polyethylene flows in molten condition and with a further pressure reduction into the low-pressure separator, before entering the extruder. 
• After the extruder, there are blending and pellet devolatilization silos. EVA products have a sticky nature and will undergo special handling in these sections.

References

1. Chemical Industry Topics From knak's database,18^th Apr 2006, The beginning of excessive competition in Japanese petrochemicals The competition to introduce polyethylene technology.
2. Sumitomo Chemical > Technology Licensing > Sumitomo EVA/LDPE Process. (Accessed 29^th Dec 2024)
3. a. Shinishiro Kita et al., Priority Date 4^th Aug 1077, US4123600, Assigned to Sumitomo Chemical Co Ltd, Process for the high pressure production of polyethylene, Status: Expired - Lifetime.
   b. Yasumi Tomura et al., Priority data 17^th Dec 1979, US4271280A, Assigned to Sumitomo Chemical Co Ltd, Process for producing polyethylene, Status: Expired - Lifetime. 
4. Lummus Technology > Process Technologies > Polymer Technologies, Hyperlene A LDPE and EVA Technology. (Accessed 29^th Dec 2024)