Synthesis And Modification Of Vinyl Acetate-Acrylamide Copolymer Surfactant

Polymeric surfactant is a kind of widely utilized chemical products in various fields such as medical treatment,coating,material,petroleum,etc.Especially in the petroleum field,because of unique thickening and viscosity reduction function of the polymeric surfactant,polymeric surfactant could be widely utilized in the process of the tertiary oil recovery.When oil is driven by the aqueous solution of the polymer surfactant as the displacing liquid,the aqueous solution of the polymer surfactant has a higher viscosity,which can effectively reduce the mobility difference between oil phase and water phase and increase the driving force in the process of oil displacement.On the other hand,it has good interface performance,which c.an emulsify crude oil and increase crude oil recovery rate effectively.Currently in China the main technology methods of the tertiary oil recovery are surfactant flooding and polymer flooding.In this thesis,polyI,mer surfactants with highly effective thickening and viscosity reduction was investigated in details because it can combine advantages of surfactant flooding and polymer flooding.The molecular structure of VAc and acrylamide(AM)copolymer was modeled by means of the Material Studio software.After optimization of the model,an aqueous surfactant solution system was established.The viscosity characteristics of the solution system were studied by means of taking the radius of gyration as an index.It was found that the temperature had a certain influence on the viscosity of the solution system.When the monomer ratio of VAc:AM was 1:3,the solution system had the best viscosity performance,and the viscosity of the solution system was positively correlated with the polymerization degree of this copolymer.Based on the molecular simulation,the copolymer surfactant VAc-AM was successfully synthesized by the continuous reaction method,and its molecular structure was characterized by the infra-red spectra.The polymerization conditions were optimized,and the optimal polymerization conditions were as follows:the reaction temperature was 60 0C,the reaction tirme was 4 hrs.,the raw material monomer concentration was 20 wt%,and the initiator concentration was 0.08 wt%.When the VAc-AM ratio was 1:3,the surface tension of the copolyrmer aqueous solution had a minimum value of 55 mN/m at the room temperature.The te:mperature had an enhanced effect on the surface tension.When the concentration of the copolymer aqueous solution reached 1600 mg/L or more,the thickening ratio of this copolymer surfactant to water can be more than 80 times.Moreover,the polymer had strong salt resistance.It can maintain surface properties and thickening properties at high salinity as like as at a low salt environment.In order to further strengthen the surface property of the copolyrmer surfactant VAc-AM,the copolymer was modified by grafting etherification with different carbon chain length fatty alcohols.It was found experimentally that after etherification modification with lauryl alcohol in VAc-AM,the product can have a minimum surface tension of about 35 mN/m while it can keep high salt resistance and thickening property as like as before etherification modification.By means of the Ubbelohde viscometer,the molecular weight of the modified copolymer surfactant VAc-AM was about 60,000.The CMC concentration was 0.02 g/mL.The interfacial tension betvween this surfactant and crude oil can be close to 10-2 mN/m.In addition,it had good emulsifying ability and stability of the emulsion solution was strong.The maximum foaming height was 460 mL,and the half-life of the foam was 140 s through the foam property test.