Emulsion Copolymerization Of Vinyl Acetate/Vinyl Ester Of Versatic Acid

Vinyl acetate polymers (PVAc) are widely used in coatings and adhesives, but lacking of enough water resistance and alkali resistance limits its use areas. Vinyl ester of Versatic acid (VeoVa) is a good copolymerization monomer with excellent water resistance, weather resistance and alkali resistance.As VeoVa copolymerized with VAc, the performances of copolymer emulsion could be improved. Influences of VAc/VeoVa10 emulsion copolymerization recipe and conditions on the copolymerization kinetics, size and size distribution of copolymer latex particles, copolymer molecular weight and molecular weight distribution, copolymer composition and performance of copolymer latex film were investigated in this thesis, to optimize copolymerization conditions and to provide foundation for preparation of VAc/VeoVa10 copolymer latex with good integrated performances.VAc/VeoVa10 emulsion copolymerization was studied using sodium dodecyl sulfate (SDS) as emulsifier, poly(vinyl alcohol) (PVA) as protective colloid, and potassium presulfate (KPS) as initiator. The effects of reaction temperature, initiator concentration, emulsifier concentration, monomer composition, and protective colloid concentration on the time-conversion relationship and copolymerization rate (Rp) of phase Ⅱ were investigated. It is showed that Rp increased as copolymerization temperature increased. The Rp had the following relationships with the concentrations of KPS, SDS and PVA: R_p ∝ [KPS]^0.658, R_p ∝ [SDS]^0.371 and R_p ∝ [PVA]^0.58.Monomer composition had no significant influence on the Rp. Because of the great water solubility of VAc monomer, VAc/VeoVa10 copolymerization kinetics departed from the classical emulsion polymerization kinetics, and was close to the kinetics of VAc emulsion homopolymerization. However, it still had little difference with the kinetics of VAc emulsion homopolymerization due to the existence of VeoVa10 in feeding monomers.The effects of polymerization temperature, initiator concentration, emulsifier concentration, monomer composition, and protective colloid concentration on thecopolymer latex particles size and size distribution, and number of latex particles(N_p)were also investigated. It is showed that copolymer latex particles size and size distribution decreased, N_p increased as copolymerization temperature, initiatorconcentration and emulsifier concentration increased. The relationships between N_p and [KPS], N_p and [SDS] show as follows: N_p ∝ [KPS]^0.893, and N_p ∝ [SDS]^1.07,which also departed from the classical emulsion polymerization behavior. The particles size and size distribution of copolymer latex increased, and N_p decreasedas copolymerization conversion and protective colloid concentration increased. Monomer composition had no significant influence on particle size and size distribution of latex copolymer.Molecular weight and its distribution of copolymer was tested by GPC. It is showed that the average molecular weight decreased, and molecular weight distribution increased as the copolymerization temperature and initiator concentration increased; the average molecular weight increased as emulsifier concentration increased. The realationship between the number average molecular weight (M_n) and [KPS] and[SDS] show as follows: M_n ∝ [KPS]^-0.375, M_n ∝ [SDS]^0.16, which was departed fromthe classical emulsion polymerization behavior as X_n ∝[I]^-3/5[S]^3/5. This is relatedwith the great water solubility and chain transfer constant of VAc monomer. The copolymerization conversion had no significant influence on molecular weight of copolymer.The VAc/VeoVa10 copolymer composition was tested by NMR, and T_g ofcopolymer was tested by DSC. The effects of feeding monomer ratio on the copolymer composition and T_g of copolymer were investigated. The results showedthat copolymer composition was close to feeding monomer ratio, T_g of copolymer decreased as VeoVa10 content in copolymer increased.The water resistance and alkali resistance of VAc/VeoVa10 copolymer latex filmwere tested based on National Standard (GB) and current standards, effects of VeoVa10 content and PVA concentration on the copolymer latex film performances were investigated. The results showed that the water resistance and alkali resistance of VAc/VeoVa10 copolymer latex film increased as VeoVa10 content increased. When VeoVa10 content was 20%, the performances of copolymer latex film exceed the standard of the first class coating products in GB/T9755-2001. The water resistance of copolymer latex film decreased as PVA concentration increased.