Synthesis And Application Research Of Self-crosslinking Core-shell Structure Acrylic Emulsion At Ambient Temperature

Polyacrylate emulsion is known as an environmental-friendly emulsion with excellentperformance, which is easy to prepare and widely applicable. Self-crosslinking acrylicemulsion with hard core-soft shell structure and active keto-carbonyl group was synthesizedby core-shell emulsion polymerization, and film was cured at ambient temperature thoughreaction of ketone and hydrazide. To further improve comprehensive performances,multi-crosslinking system was used to modify emulsion. Various factors influential foremulsion performance were discussed during the experiment such as polymerizationconditions, crosslinking system and cross-linking monomer dosage, curing conditions, etc.Resultant emulsion was applied to bond phenolic resin-coated corrugated paper. Severalfactors were found to be influential for boiling water-resistance properties and adhesion of theemulsion after being boiled, such as polymer glass transition temperature, type and amount oforganic siloxane monomer, type and amount of film forming additive, etc. Optimum processand formula were obtained. Some innovative ideas in latex structure design and crosslinkingsystem of emulsion are proposed in this paper.As is indicated from experimental results, optimum polymerization condition wasdetermined as follows: hybrid emulsifier constitutes of m(CO-436), m(CO-630) andm(COPS-1) at a ratio of 1~1.5︰0.8~1︰0.2~0.3, at a total dosage of 2~2.8 wt%. Dosage ofDDM is 0.1~0.2 wt%. A combination of thermal initiation (0.4 wt% of APS) and redoxinitiator system (0.1 wt% of THBP, 0.1 wt% of SFS) was adopted to initiate thepolymerization. Dosage of AA and functional monomer mixture (GMA+HEA) were set at1~3wt% and 2~3wt% respectively. DAAM were all added to the shell, at dosage of 1.5~2wt%. m(ADH)/ m(DAAM) ratio was controlled at 0.8~1, m(core)/ m(shell) ratio is designedat 4/6~6/4. All weight ratios above are based on total monomer content. At conditions above,emulsions with high solid content and conversion rate, as well as highlycross linked film withwide molecular weight distribution and low water absorption could be prepared.Several testing methods such as FTIR, DSC and TEM were adopted to characterize theemulsion. Emulsion particle size and molecular weight distribution were determined byparticle size analyzer and GPC respectively. FTIR spectra confirmed the crosslink reaction between ketone and hydrazino group. Two glass transition temperatures at 18.2℃and 44.5℃could be clearly observed in DSC curve of the resultant emulsion sample. Obviouscore-shell structure was shown in TEM images.It is suggested from application experiments that different kinds of organic siloxanemonomer were used to modify emulsion for improving boiling water-resistance. To achieveequivalent modification effect, C-1757 (4wt %) has to be added at dosage of eight times ofZ-6040(4wt %). Film forming additive could improve the permeability of the latex onsubstrate, and also help alleviate blistering of film during boiling water. As is compared withRohm & Haas AC-261P, self-prepared latex exhibit better performances such as lower waterabsorption and slighter blistering, thus having a huge potential application prospect.