| Due to its excellent weatherability, environment-friendly, low cost and safety in theprocess of manufacture and use, acrylate emulsion has been widely used in many fields, suchas coatings, adhesives, inks and textile. However, latexes are hydrophilic due to functionalgroups and ionic charges derived from surfactant, initiator, buffer, and functionalcomonomers, and do not easily wet the hydrophobic substrate surfaces. Compared tosolvent-based products, acrylate emulsion has poor water, heat and creep resistance andadhesive properties, especially, it’s hard to adhere to low polar and no polar surfaces whenused as pressure sensitive adhesive (PSA). Therefore, a great challenge is faced to keep thebalance of good adhesive properties, wettability and high temperature resistance, so thatacrylate emulsion can reach the properties of solvent-based products for high-performanceapplication. In this dissertation, rosin derivatives/acrylate composite emulsions were preparedby using reactive surfactant, and rosin derivatives with high softening point as tackifying resin.Then latex films with excellent adhesive properties, creep resistance, high temperatureresistance and water resistance were obtained via curing. Effects of a series of conditions onemulsion polymerization and latex film properties were systematically investigated, andstructures of emulsion and latex film were characterized and analysized. Meanwhile, relevantmechanisms in emulsion polymerization were explored. Main research contents and resultsare listed as following:Firstly, stable polymerized rosin/acrylate composite emulsion was successfully preparedby semicontinuous pre-emulsification polymerization using butyl acrylate (BA),2-ethylhexylacrylate (2-EHA) and methyl methacrylate (MMA) as main monomers, acrylic acid (AA) and2-hydroxyethyl acrylate (2-HEA) as functional monomers, allyloxy nonylphenolpolyoxyethylene (10) ether (ANPEO10) and its ammonium sulfate (DNS-86) as reactivesurfactants, and polymerized rosin as tackifying resin. Effects of the polymerizationtechnology, reaction conditions, reactive surfactants content and ratio, polymerized rosincontent on the emulsion polymerization process and latex film properties were studied. Thecomposite emulsion was characterized by dynamic light scattering (DLS), Fourier transforminfrared spectroscopy (FT-IR), differential scanning calorimeter (DSC), gel permeationchromatography (GPC) and transmission electron microscopy (TEM). The results showedthat the optimal polymerization conditions were0.5wt%initiator KPS,0.6wt%surfactantsand ANPEO10/DNS-86=1,6wt%polymerized rosin and reaction temperature80℃. It couldalso be found that the reactive surfactants incorporated in the polymer chain via polymerization reaction, and could effectively reduce water absorption ratio of the latex film;polymerized rosin had good compatibility with acrylate copolymer. However, carbon-carbonconjugated double bonds of the residual rosin acid in polymerized rosin could play the role ofchain transfer and inhibitor, and hence inhibited the formation of branched and crosslinkedpolymer.Secondly, polymerized rosin/acrylate composite emulsion was cured by curing agentaziridine (XC-113) and hexahydroxy-methyl melamine resin (HMMM). Effect of curingcondition on adhesive properties of PSAs, and effects of curing agent content and ratio on gelfraction, swelling degree, water absorption ratio, adhesive properties and high temperatureresistance of PSAs were studied. It was found that the optimal curing condition was110℃/3min for XC-113and150℃/5min for HMMM.With the increasing of curing agentcontent, the crosslinking density of PSAs increased, swelling degree, tack and peel strengthdecreased, cohesion strength and high temperature resistance of increased. It was found thatXC-113and HMMM had synergistic effects on curing acrylate composite emulsion. When themass ratio of XC-113/HMMM was1/2and the total content of curing agent was1.8wt%, theball tack, peel strength and shear resistance of PSAs were19#steel ball,9.0N/25mm and morethan1500min, respectively, and high temperature resistance of reached180℃.Third, hydrogenated acrylic rosin/acrylate composite emulsion was prepared bysemi-continuous pre-emulsification polymerization using BA and MMA as main monomers,AA and2-HEA as functional monomers, DNS-86as surfactant, and hydrogenated acrylicrosin as tackifying resin. The effects of polymerization conditions, hydrogenated acrylic rosincontent and monomers composition on polymerization process and latex film properties wereinvestigated. The composite emulsion and its latex film were characterized by FT-IR, DLS,DSC, TGA and GPC. The optimal polymerization conditions were5wt%MMA,2wt%DNS-86,3h of feeding time and1.5h of soaking time. Also, hydrogenated acrylic rosin couldobviously improve monomer conversion in the emulsion polymerization of acrylates andincreased the polymerization stability in comparison with polymerized rosin. Whenhydrogenated acrylic rosin content was10wt%, monomer conversion could reach98.0wt%and the coagulum ratio was only0.26wt%. DSC analysis showed that polymerized rosin andpolyacrylate exhibited good compatibility, and the adding of polymerized rosin into acrylatepolymer incrceased the glass transition temperature of composite latex film.Fourth, curing conditions of hydrogenated acrylic rosin/acrylate composite emulsion viaepoxy silicone curing agent (9301) and polyisocyanates curing agent (2012) were investigatedand the effects of curing agent content on composite latex film microstructure and properties were studied. Compared to aziridine SC-100, the working life of composite emulsion addedinto2102,9301and SC-100was6h,12h, and48h, respectively; the curing efficiency of thethree curing agent was9301<2102<SC-100. The latex film cured by9301, which containedorganic silicone in molecular structure, had better water resistance than films cured by2102and SC-100and its thermal decomposition temperature was improved. Although the additionof hydrogenated acrylic rosin could increase adhesive properties of PSAs, excessivehydrogenated acrylic rosin caused the decrease of polymer bulk viscosity and cohesionstrength, and further made high temperature resistance and anti-aging properties poor. Whenhydrogenated acrylic rosin and curing agent2102content were5wt%and2.5wt%, PSA couldget the reasonable comprehensive performance, and peel strength was9.2N/25mm and hightemperature resistance was200℃. |
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