Synthesis Of Water-based Low Temperature Self-crosslinkable Acrylic Resin And Its Application In Water-based Ink For Pe/PP Thin Film

Recent years, for serious environmental pollution, all the countries have legislated aseries of rules of environmental protection in order to reduce the emission of VOCs.Water-based ink has been instead of oil-based ink in some development countries in theindustry of food packages, children toys and medical treatment which have close relationshipwith human. Water-based ink is difficult to be applied in PE/PP thin film due to low polarityand easy curl deformation at high temperature. In this paper, we developed a low temperature(≤60℃)self-crosslinkable water-based acrylic resin as the binder of water-based ink forPE/PP thin film. The self-crosslinkable water-based acrylic resin has high performances ofglossniess, crosslinking degree, adhesion, water-resistance, solvent-resistance, and low VOCs.A low temperature self-crosslinkable water-based acrylic resin was synthesized byadopting free radical solution polymerization method and using AIBN as initiator, MMA ashard monomer, BA as soft monomer, AA, HPA and DAAM as functional monomer. Theinfluence of formula and process factors on molecular weight, conversion rate, solubility,Tgand film properties of acrylic resin were investigated. The results showed that99.2%conversion rate and good water solubility and stability of acrylic resin can be obtained whenthe amount (based on the total monomers) of AIBN is2%, DAAM is2%, AA is9.2%, HPA is5.8%, the resin content is40%, the weight ratio of PMA to DMF is2:1, on the condition of3hours of adding time of monomers and4hours of holding time of reaction.Film property of the low temperature self-crosslinkable water-based acrylic resin beforeand after ADH and DAAM crosslinking reaction was studied. It was found that the Tg andpencil hardness were both improved after crosslinking reaction. The more usage of DAAMcould obtain the higher crosslinking degree, while Tg of film is nearly no difference. Whenthe usage of DAAM is2%and the ADH and DAAM weight ratio is0.8, the film crosslinkingdegree is88.35%, the water absorbing capacity is10.28%, the pencil hardness is2H,suggesting the film property is best. The FT-IR and DSC results both indicate the DAAM wascrosslinked with ADH.The water-based ink with low VOCs was prepared by using the low temperature(≤60℃)self-crosslinkable water-based acrylic resin and water-based pigment. The properties ofthe ink were compared with other inks from commercial water-based and solvent-based resin.The optimized formula of ink at the weight ratio of pigment and resin of20:65have100%of film colouring power,1level of adhesive strength,89°of glossiness (60°), and foldingresistance, blocking resistance and dry fractional resistance of film.