Study On Preparation Of Silica Sol/Self Crosslinking Styrene Acrylic Emulsion And Its Application In Interior Wall Coatings

Using styrene(St)and butyl acrylate(BA)as main monomers by semi continuous seeded emulsion polymerization with core-shell,crosslinking modification methods,studied the effects of emulsifier,initiator,monomer ratio,crosslinking agent types and dosage on the self crosslinking styrene acrylate emulsion and film properties.The results showed that in the "semi starvation state" adding initiator,emulsifier polyoxyethylene alkyl ether ammonium sulfate(KL-525)and 2-acrylamide-2-methyl propane sulfonic acid sodium salt(COPS-2)(mass ratio 2:1)total amount accounted for the main monomer 2wt%,crosslinking agent with epoxy silane oligomer(SOE-40)added the amount of 2wt% or N-hydroxyethyl acrylamide(HEMAA)by adding 1wt%,the gel rate of emulsion was less than 1% and the film scrub was up to 756 times.Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and transmission electron microscopy(TEM),Malvern laser scatter,contact angle and thermogravimetric(TG)were used to determine the mechanism of self crosslinking styrene acrylic emulsion.FT-IR analysis showed that the HEMAA grafted copolymer;SEM and TEM analysis showed that the structure of emulsion particles matched the designed morphology structure.Malvern laser scatter results indicated that particle size matched Malvin particle size.Contact angle and TG analysis showed that the water absorption ratio of latex film decreased from 24.4% to 7.4%,T0.5 increased by 35.04 degrees.Crosslinking mechanism analysis pointed out that the self crosslinking emulsion process is divided into three stages,main for fugacity crosslinking.Silica sol modification was further studied to overcome the disadvantage that the self crosslinking styrene acrylate emulsion monomer conversion rate is not high and the latex film adhesion,resistance and scrub resistance are poor.The results showed that,by in situ polymerization,adding silica sol dominant monomer dosage of 5%wt,pH in 8.0~ 9.5 LS-30 and the dropping time was 20~30min,the adhesion of composite latex film prepared by lifting two grades,hardness 0.76,scrub resistance up to 1232 times.The redox system of H2O2/FF6 M in reducing the residual monomer was better than t-BHP/FF6 M,when the total amount of H2O2/FF6 M was 0.2wt% and the ratio of 2:1,the monomer conversion rate was upto 99.43%.FT-IR analysis showed that the silica sol by crosslinking agent Y-methacryloxypropyl trimethoxysilane(A-174)grafted onto polymer emulsion;XRD composite latex film and fracture surface analysis of SEM showed that the silica was successfully encapsulated in self crosslinking core-shell styrene acrylic latex particles,suggesting that silica sol dispersed in the emulsion;TG analysis showed that the T0.5composite latex film increased by 39.24 degrees.Finally,a high pigment volume concentration(PVC)of interior latex paint was prepared with the self-made silica sol / modified styrene acrylic composite emulsion.The effects of thickening agent,wetting dispersant,pigments and functional monomer on the interior wall paint performance were studied.The results showed that the anionic associative thickener and alkali swelling the ionic water-soluble cellulose ether compound,nonionic wetting agent and non-ionic dispersant collocation matched,enhanced the system stability and latex scrub resistance.Optimization of power structure and adding functional monomer could also improve the latex scrub-resistance.Coatings test results indicated that the volatile organic compounds(VOC)was not detected(detection limit of 2g/L),the free formaldehyde was8 ppm and the latex scrub was up to 1450~1560 times.