Preparation And Properties Of Removable Acrylic Pressure Sensitive Adhesive Emulsions

Removable pressure sensitive adhesive is widely used in temporary protective film of medical, automotive, building materials, home appliances, LCD and other fields. Removable polyacrylic emulsion pressure sensitive adhesive is environmentally friendly, so it attracted attention in recent years. The acrylic pressure sensitive adhesive emulsions were prepared with butyl acrylate (BA), methyl methacrylate (MMA) and acrylic acid (AA) as monomer, potassium persulfate (KPS) as initiator and sodium dodecyl sulfate (SDS) as emulsifier. Then, the pressure sensitive adhesives were modified by the diacetone acrylamide (DAAM)/adipic dihydrazide (ADH) room temperature self-crosslinking system. Finally, the crosslinking polyacrylic pressure sensitive adhesives were further modified by 2-(perfluoroalkyl)ethyl methacrylate to improve the removable performance.The acrylic pressure sensitive adhesive emulsions were prepared by pre-emulsification semi-continuous emulsion polymerization. The effects of the stirrer agitation, the amount of KPS, the amount of SDS and the mass ratio of soft monomer to hard monomer on stability of emulsion polymerization, emulsion properties and mechanical performances of pressure sensitive adhesive tapes were discussed. The proper reaction conditions were determined as follows:the stirrer agitation was controlled at 240 r/min,the amount of KPS, SDS was 0.7% and 3%, respectively, and the mass ratio of soft monomer to hard monomer was 80/18. In these conditions, the polymerization had low gel fraction, high productivity and good stability, and the prepared polyacrylic emulsions and latex films showed good comprehensive performances.Room temperature self-crosslinking polyacrylic emulsions were prepared by introduction of DAAM on backbone via random copolymerization, and the effect of the amount of DAAM on performances of self-crosslinking polyacrylic emulsion and pressure sensitive adhesive tapes was studied. The results were as follows:storage stability of the emulsion decreased rapidly with the increasing of DAAM amount,and the emulsion particle size distribution showed that latex particles occurred more coalescence with the increasing of DAAM amount. The mechanical performances of pressure sensitive adhesive tapes were also affected by the amount of DAAM. When the amount of DAAM was 2% of the total mass of monomers, various mechanical performances of pressure sensitive adhesive tapes were moderate, the tapes were easy to be removed, and prolonged adding of peel strength was little. Simultaneously, the emulsions had good storage stability.Room temperature self-crosslinking polyacrylic emulsions modified with 2-(perfluoroalkyl)ethyl methacrylate through copolymerization was prepared. The fluorinated emulsion was stable and showed good integrated performance. Furthermore, the performances of the prepared pressure sensitive adhesive and several commercial products were compared. The results were as follows:a small amount of fluoromonomer,0.5% of the total mass of the monomers, could significantly improve the storage stability of self-crosslinking pressure sensitive adhesive emulsion, improve various mechanical performances of pressure sensitive adhesive tapes,and enhance removable performance. The removable performance was improving with continuing to increase the amount of fluoromonomer, but the cost performance was relatively low in this case. Compared with several commercial products, the prepared pressure sensitive adhesives had relatively low peel strength and were easy to be removed. And the prolonged increasing of peel strength was at a low level.