Hydrophobically
modified methacryl- and acrylamide polymers are well-known kinetic
hydrate inhibitors (KHIs). Polymers of N-isopropylmethacrylamide
(IPMAM) are now commercially available. However, both polyIPMAM and N-isopropylacrylamide homopolymer (polyIPAM) have low cloud
and deposition points, making it difficult to use them in the field
because of precipitation problems. Comonomers that are more hydrophilic
can be copolymerized with IPMAM or IPAM to raise the cloud point.
In this work, we have synthesized and investigated a series of new
copolymers of IPAM and a new dimethylhydrazidoacrylamide monomer (DMHAM)
as KHIs for the first time using high-pressure gas hydrate rocker
rig equipment. The novel polymers have high cloud points in deionized
water and also in brine solutions compared to polyIPAM. A 1:2 copolymer
of DMHAM/IPAM gave the highest KHI performance for this class of copolymer
with a cloud point at 58 °C in deionized water. A 1:1 copolymer
gave only a small reduction in performance but has a cloud point of
83 °C in 3.6% NaCl and no cloud point in deionized water. Tests
were carried out using high-pressure slow constant cooling rocking
cell experiments with a structure-II-forming natural gas mixture at
approximately 80 bar.