Preparation And Characterization Of Acrylate Emulsion Modified By Hydrogenated Acrylic Rosin

Acrylic emulsion pressure sensitive adhesive is harmless to human and environmentallyfriendly product with good resistant to climate. Generally speaking, its adhesive property canbe improved by adjusting its co-monomer composition. However, tackified resins (TRs) areusually added to obtain better peel strength against substrate with little polarity or low surfaceenergy. Highest polarity of abietyl acid and its derivatives which have good compatibilitywith acrylic emulsion make them the best choice among all the commercial TRs includingpetroleum resin and terpene resin. In this paper, tackified BA/MMA/AA/HEA acrylicemulsions were prepared via core-shell emulsion polymerization and microemulsionpolymerization using potassium persulfate (KPS) as initiator, allyloxy nonylphenolethoxylates ammonium sulfate (DNS-86) or/and sodium dodecyl sulfate (SDS) as emulsifier,n-pentanol (n-PTL) as co-emulsifier, hydrogenated acrylic rosin (HAR) as TR which wasdissolved in the mixed monomers.During the core-shell emulsion polymerization, the effect of core monomer content,emulsifier ratio of core to shell, chain transfer agent and HAR content on monomerconversion, coagulum ratio, particle diameter and particle size distribution of emulsion,crosslinking degree and water absorption ratio of latex films were investigated. The resultsshowed that monomer conversion reached98.4%, coagulum ration as low as0.22%, milkybluish HAR tackified acrylic emulsion could be obtained with moderate viscosity and solidcontent of50%when0.5wt%KPS,2wt%DNS-86，35wt%core monomer,2:1emulsifierratio of core to shell,0.2wt%CTA and6wt%HAR were used. Besides, it was found thatHAR could play the role of CTA and inhibitor which reduced the reaction rate, crosslinkingdegree and molecular weight of sol. DSC curves proved good compatibility between HARand acrylic emulsion and glass transition temperature of co-polymer increased with theincorporation of HAR.During the microemulsion polymerization, the effect of the ratio of emulsifier to co-emulsifier on microemulsion area, emulsifier ratio of DNS-86to SDS and content, type of co-emulsifier, monomer feeding method and time, HAR content on the polymerization processand properties of emulsion were studied. The results showed that the largest microemulsionregion could be achieved when SDS/n-PTL was2and high monomer conversation of99.3%,low coagulum ratio of0.03%, particle diameter of44.2nm acrylic micoemulsion could beprepared with the solid content of30%and good emulsion stabilities. Meanwhile, the addition of HAR made the particle diameter bigger, particle size distribution boarder and theappearance of emulsion turbid.The effect of HAR content on adhesive properties (ball tack, peel strength and cohesivestrength) and heat resistance of Pressure sensitive adhesives (PSAs) casted from those twokinds of latex and post-cured PSAs were investigated; FTIR was used to characterize thestructure of PSAs. It can be concluded that the addition of HAR can improve PSAs’ adhesiveproperties, but reduce cohesion strength and heat resistance.1wt%crosslinker9301couldimprove cohesion strength and heat resistance with no sacrifice of peel strength. Comparedwith core-shell emulsion polymerization, PSAs obtained by microemulsion polymerizationhad better cohesion and heat resistance but worse peel strength.