Study On The Synthesis Of Water Soluble Acrylic Coatings

Acrylic resin has better glossiness, weather-resistant, chemical resistance, safety of productionand low price. But organic solvent of acrylic resin which is synthesized in traditional way will polluteenvironment when it volatilizes. Unlike organic solvent resin, waterborne resin has some advantagesof low price, safety in use, energy conservation, low environment pollution and non-toxic. Moreover,the varnish made from water-soluble acrylic resin has some good features such as non-toxic, odorless;acid and alkali resistant, inflaming retarding; good glossiness, good adhesion, no fading; andweather-resistant, chemical resistance. It is a kind of green environmental products of low VOC.However, water-soluble acrylic resin also has some shortcomings: hot-sticky cold-brittle, pooranti-adhesive back, poor heat resistance and low hardness after resin film drying. To solve theseproblems, in this study, we used the method of free radical solution polymerization to synthesizewater-soluble acrylic resin. Firstly, we optimized the formulation of water-soluble acrylic resincoating, and used self-made hexamethoxy methyl melamine formaldehyde resin (HMMM) ascrosslinking agent to improve the heat resistance and others properties. And then, we used SiO2,which is modified by KH-550, to blend the water-soluble acrylic coating, to improve the filmhardness. Finally, the performances of acrylic coatings were systematicly characterized. In this study,we finished the works as below：1. Synthesis of water-soluble acrylic resin. Through single variable repeat experiments, usingMethyl methacrylate (MMA), butyl acetate (BA),2-hydroxyethyl methacrylate (HEMA) andacrylic acid (AA) as main reaction monomer, azobisisobutyronitrile (AIBN) as initiator, we gotdifferent waterborne acrylic resin samples. By comparing their viscosities and testing theirperformances of the coatings, we expected to get an ideal formula. The experiments proved thatunder the circumstance of other conditions remaining unchanged, we got the best integratedperformance of waterborne acrylic resin when reaction temperature is95℃, MMA in an amountof4.8mL, AA in an amount of3.0mL, BA in an amount of12.0mL, HEMA in an amount of 4.0mL, AIBN in an amount of0.45g and the neutralization degree of85%. Besides, according toFT-IR, the disappearance of C=C and C-H at1643cm-1and990cm-1respectively, indecated thatthe copolymer of2-hydroxyethyl methacrylate/butyl acrylic/methyl methacrylate/acrylic wassynthsised succesfully.2. Crosslinking and curing of water-soluble acrylic resin by using self-made HMMM as across-linking agent. By mixing formaldehyde and melamine in different ratio at differenttemperature, observing their time of dissolution and the time of crystals precipitation, andmeasuring free formaldehyde content and methylol content, we chose the group which haslowest energy consumption and free formaldehyde content as cross-linking agent to cross-linkand cure the acrylic resin. The effects of cross-linking agent, curing temperature, and curing timeon the resin properties were studied. With18vol%~28vol%cross-linking agent, baking it for10~15minutes in150℃, we obtained waterborne acrylic resin film which performanced well.Furthermore, we used FT-IR to characterize waterborne acrylic coating. After curing the coatingfilm, stretching vibration absorption peak of hydroxyl (O-H) group at3415cm-1significantlydecreased, which indicated a large amout of O-H and-COOH were involved in the curingreaction.3. Modification of water-soluble acrylic coatings. The different amount of modified ultra-fine SiO2by KH-550was physically blended in optimal waterborne acrylic resin coating obtained by themethod above. And then the influences of ultra-fine SiO2on the performance of water-solubleacrylic paint before and after the modification of ultra-fine SiO2were tested.3wt%was theoptimum usage amount of modified ultra-fine SiO2that mixed in waterborne acrylic resincoating. Finally, SEM was used to characterise the modified ultra-fine SiO2-water-soluble acryliccoatings. The results showed that the dispersions of modified SiO2are much better thanunmodified SiO2due to the weaker agglomeration in the films with unmodified SiO2.