Application of reactive acrylate microgels in water-base coatings

J Shanghai Univ (Engl Ed), 2009, 13(1): 67-71Digital Object Identifier(DOI): 10.1007/s 11741-009-0113-2Application of reactive acrylate microgels in water- base coatingsSA Sheng- shu (撇圣淑)},ZHANG Bao-hua (张宝华)"，YANG Qing (杨青)"， WANG Xia-qin (王夏琴)2,MAO Zhi-ping (毛志平)21. School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, P. R. China2. Key Laboratory of Science and Technology of Eco -Textile, MOE, Donghua University, Shanghai 201620, P. R. ChinaAbstract Reactive acrylate microgels with diferent reactive groups such 8 carboxyl, hydroxide groups had excellent prop-erties such as quick-dry, low viscosity, high adhesion and hardness, which made them extensively used in preparing paints orin coating modifcation. Reactive acrylate microgels were prepared by emulsion co-polymerization with zwitterions surfactant,anionic surfactant and nonionic surfactant as co emulsifier. The water base baking paints made from reactive acrylate micro-gels and melamine-formaldehyde resin had excellent combination properties. The aluminium powder can be well-dispersed inthe paints. The infuences of monomer components on the properties of the water-base baking paints were discussed in thispaper. And the baking paints were also compared with the marketing solvent acrylate baking paints. It was found that thewater-base acrylate amino baking paints had better combination properties than the organic solvent acrylate baking paints,wbich means that the water-base baking paints had a bright marketing future.Keywords acrylate, reactive microgels, water-base, baking paints, elamine formaldehyde resinIntroductiongels can be used as a rheology modifer or as an auxiliaryagent in the motorcar industry to produce a good metal-A polymeric microgel is defined as an internallylic efect[14l.cross- linked polymeric microparticle in a liquid mediumIn this report, reactive acrylate microgels were pre-with particles having an average particle diameter frompared by emulsion co polymerization with zwitterions1 nm to 1000 nml1-2. Microgels can be preparedsurfactant, anionic surfactant and nonionic surfactantby several ways such as emulsion polymerization3s, so-as co-emulsfers. The reactive acrylate microgels werelution polymerization间， dispersion polymerizationcombined with water-base melamine-formaldehyde resinsoap-free emulsion polymerizationl), micro emulsionand aluminium powder to prepare a water-base acrylatepolymerizationl7] or precipitation polymerization8.amino baking paints. The infuences of the monormerThe microgels made from solution polymerization hadcomponents on the properties of the water-base bakingbeen in very low concentration, thus the solution poly-paints were studied here. And the baking paints weremerization method was only used in theoretical study.also compared with the marketing solvent acrylate bak-The precipitation polymerization method has been sel-ing paints. It was found that the water-base acrylatedom used since it is hard to control in the microgelamino baking paints had better composite propertiespreparing process. The emulsion polymerization and thethan the organic solvent acrylate baking paints whichdispersion polymerization were used commonly in themeans that the water-base baking paints had a brightpreparing process of microgels, but the dispersion poly-marketing future.merization method need special dispersant which washard to synthesis. The emulsion polymerization was the1 Experimentalmost popular method9l to prepare microgels because ofits simple process and the excellent combination proper-.1 Preparation of reactive acrylate microties of the microgels prepared. The comparison betweengelsthe emulsion polymerization and dispersion polymeriza-A 2.0 g zwiterion surfactant, 1.0 g Aerosol-OT (2-tion was shown in Table 1l10]. The key to prepare micro-ethylhexyl sulfosuccinate sodium), 0.75 g OP (nonylgels through emulsion polymerization is the selection ofphenyl polvethvlene glvcol ether), 0.25 g sodium bicar-emulsifier and the zwitrions surfactantl11-13). Micro-bon:中国煤化工ater were placed in aReceived Jan.15, 2007; Revised Mar.12, 2007CNMHGProject supported by the Science Foundation of Shanghai Municipal Eaucationt ommission (uran Iio.03AK59)Corresponding author ZHANG Bao-hua, PhD, Assoc. Prof, E-mail: zhangbh@shu.edu.cnJ Shanghai Univ (Eng] Ed), 2009, 13(1) 67-71fAask, then heated to 87 °C with stirring. A monomerthe emulsion was kept at 87 °C for half an hour, thenmixture of 2.5 g N, N'-mathylene bisacrylamide, 32 g n-the microgels emulsion was discharged as white latexbutyl methacrylate, 7.0 g 2-hydroxyethyl acrylate, 0.5 gwith blue light.acrylic acid, 0.75 g OP, 20 mL of deionized water was1.2 Formulations of water-base acrylateadded in a beaker and pre-emulsificated for 15 min underamino baking paints and solvent acry-high speed stirring, then it was added drop-wise to thelate baking paintsfask within 2 h. Simultaneously an initiator solution ofThe formulations of water-base acrylate amino bak-0.25 g ammonium persulfate in 14.5 mL of deionized wa-ing paints of reactive acrylate microgels and melamine-ter was added drop by drop to the fask within2 h. Afterformaldehyde resin (Resimene 717) and those of the sol-all the monomers and initiator solution were dropped,vent acrylate baking paints were shown in Table 2.Table 1 Comparison between the emulsion polymerization and dispersion polymerizationPropertiesEmulsion polymerizationDispersion polymerizationParticle size/nm20~500200~2000Selection of monomerMore selective of co monomer Hard to use bydrophobic monomerGel produced/(mmol.g 1)0~3X 10-30~10- 4Surface functional groupsAcidic, alkaline, polar groups Hard to introduce polar groupsDispersionAqueous solventsStabilityInstabilityOrganic solventsTable 2 Formulations of water-base acrylate amino baking paints and solvent acrylate baking paintsSampleFormulationAmounts/%Reactive acrylate microgels emulsion (40%)Water-base acrylate aminoResimene 71716baking paintsButyl alcoholLittleAluminium powder (42 um)Acrylate resin solution (56%);0Curing agent (45%)30Solvent acrylate baking paintsOrganic DiluentAluminiun powder (42 um)Note: Resimene 717 was from the Shanghai Maipoluo Co. Ltd; Aluminium powder (42 um) was from the Changzhou ShineAluminium Co. Ltd; Acrylate resin solution, Curing agent, Organic Diluent were from the Dongsheng Xinwei Chemical EngineeringCo. Ltd.1.3 Preparation of baking paintsment (GB 1720-79); and impact resistance property wasAccording to Table 2, all the materials were addedmeasured by the impact resistance testing equipmentand uniformly mixed in the beaker, and the mixture(GB/T 1732-1993).was milled with the cone mill. Then the water-baseThe water-resistant properties and alkali resistantacrylate amino baking paints and the solvent acrylateproperties of the baking paints films were measured asbaking paints were gained.follows: the aluminium pieces with flms were put into1.4 Preparation of water-base acrylatewater (or 10% sodium hydroxide solution), and the timeamino baking paints filmswas recorded when bubbles appeared.The water-base acrylate amino baking paints was2 Result and discussioncoated on the standard aluminium pieces and was putinto an oven to be dried within 30 min at 140 °C.2.1 Influence of 2-hydroxyethyl acrylate on1.5 Characterization of water-base acrylatethe properties of water-base acrylateamino baking paints flmsThe mechanical properties of the baking paints flms中国煤化工/l acrylate on thewere measured by the National Standard of Chinawate: paints was shown inmethod. The hardness property was measured byTable;YHC N M H Gpaints was that reac-the pencil sclerometer (GB/T 6739-1996); the adhesiontive acrylate microgels/Kesimene 717/aluminium pow-property was measured by the adhesion testing equip-der=80/16/4.J Shanghai Univ (Engl Ed), 2009, 13(1): 67-716It can be seen from Table 3 that the properties ofKOH) and the preparing process was easy to control.the baking paints films became better as the more 2-2.2 Infuence of 2-hydroxyethyl acrylatehydroxyethyl acrylate was used. This may be becauseand acrylic acid on the propertiesthat the polar bydroxyethyl groups of 2-hydroxyethylof water-base acrylate amino bakingacrylate can improve the films properties. When moreamount of the 2-hydroxyethl acrylate was used in the mi-paints filmscrogel preparation process, the viscosity of the microgelsThe infuence of 2-hydroxyethyl acrylate and acrylicemulsion would increase which made the emulsion poly-acid on the water-base acrylate amino baking paintsmerization process out of control. As a result, the filmswas shown in Table 4. The component of baking paintsmade fromg 2-hydroxyethyl acrylate had the bestwas that reactive acrylate microgels/ Resimene 717/alu-combination properties (its value of hydroxyl was 58 mgminium powder= =80/16/4.Table 3 Infuence of 2 hydroxyethyl acrylate on the properties of the water-base acrylate amino baking paints films2-hydroxyethylImpactResistance toSampleHardnessAdhesionacrylate/gresistance/kg.cmwater/halkali/h7.06H .504006.06H32235.05H24:0.015l2H5l08Note: Hardness: 6H>5H>4H>3H>2H>H>HB>B>2B>3B> 4B>5B>6B; Adhesion: 1>2>3>4>5>6>7; Impact resistance:50 kg.cm> 40 kg:cm>30 kg.cmTable 4 Infuence of 2-hydroxyethyl acrylate and acrylic acid on the properties of the baking paints films2-hydroxyethyI acrylate:Resistance to Resistance toHardness Adhesionacrylic acid/g7.0:0.5486.0:0.56l5.0:0.532t4.0:0.55120104.0:1.0 .4H230It can be seen from Table 4 that when the total2.3 Infuence of the ratio of reactiveamounts of 2-hydroxyethyl acrylate (7.0 g) and acrylicacrylatemicrogelsand melamine-acid (0.5 g) were 7.5 g, the properties of baking paintsformaldehyde resin (Resimene 717) onhad the best combination properties. When Sample 6 inthe properties of water-base acrylateTable 4 was compared with Sample 1 in Table 3, it canamino baking paints flmsbe found that the combination properties of the bak-The baking paints were prepared with water-ing films were improved when acrylic acid was added.base melamine-formaldehyde resin (Resimene 717And the stability of the microgel emulsion polymeriza-tion was also improved. The reason may be that thereand reactive acrylate microgels. Water-base melamine-was synergic efect between the 2-hydroxyethyl acrylateformaldehyde resin and reactive acrylate microgels willand acrylic acid. When the amounts of acrylic acid wereform cross-links by the etherification at the high tem-1.0 g, the baking paints films had worse properties. Beperaturecause acrylic acid would dramatically increase the vis-N-CHh-0CH:+PmOH→N- -CH2 - OP+CHzOH.cosity of microgel emulsion which infuence the prepar-中国煤化工ing process or microgels. As a result, the baking paints1HCNMHGof reactive acrylatefilms made from 7.0 g 2-hydroxyethyl acrylate and 0.5 gbaking paints wasacrylic acid had the best combination properties.shown in Table 5. The amounts of 2-hydroxyethyl acry-70J Shanghai Univ (Engl Ed), 209, 13(1): 67-71late and acrylic acid in the reactive acrylate microgelsble 6 that the contents of the aluminium powder waswere 7.0:0.5.negatively relative to the film properties. Then the con-It was found from Table 5 that the films with thetent of aluminium powder was controlled about 4% ofratio of water-base melamine-formaldehyde resin (Res-the total weight of the baking paints, the baking paintimene 717 ):reactive acrylate microgels= 1:5 had the bestreaches the best combination properties. If the amountcombination properties. When the ratio was less thanof aluminium powder was less than 4%, the color ef-1:5, the properties of the baking paints were worse,fect of baking paints was not perfect. If the amount ofbecause reactive group of the microgels had not re-aluminium powder was more than 4%, the combinationacted completely and less cross-links formed. And whenproperties were bad.the ratio was more than 1:5, the baking paints flms2.5 Comparison of the water-base acrylatealso had worse properties. Because self-condensationpolymerization would occur when there were extraamino baking paints films and the sol-melamine-formaldehyde resins which made the film hadvent acrylate baking paintsworse properties. Therefore, the amount of melamine-The comparison of the water-base acrylate aminoformaldehyde resin should not be more than the needbaking paints fims and the solvent acrylate bakingto prevent the self-condensation polymerization and topaints was shown in Table 7.form the desired stereo cross-linking structure.It can be seen from Table 7 that the combination2.4 Infuence of aluminium powder on theproperties of water-base acrylate amino baking paintsproperties of water-base acrylate aminowere better than the solvent acrylate baking paints. Itbaking paints flmsmeans that the water- base baking paints have a poten-The infuence of aluminium powder on the bakingtial market in replace of the marketing solvent acrylatepaints was showen in Table 6. It was found from Ta-baking paints. .Table 5 Infuence of diferent ratio of reactive acrylate microgels and Resimene 717 on properties of the baking paints filmsResimene 717: reactivempactResistanceRessistanceSampleHardnesAdhesionacrylate microgels/gresistance/kg.cmto water/hto alkali/h111:3H215IH136H483:2721142HTable 6 Infuence of aluminium powder on properties the baking filmsAluminiumHardness AdhesionImpactResistance to Resistancepowder/%water/h503534038303228826Table 7 Comparison of the water-base acrylate amino baking paints films and the solvent acrylate baking paintsResistance toHardnessresistance/kg-cmalkali/hWater-base acrylate amino1_50baking paints of Sample 6中国煤化工Solvent acrylate baking paints5nYHCNMHGJ Shanghai Univ (Engl Ed), 2009, 13(1): 67-71713 Conclusion[5] MURRY M J, SNOWDEN M J. 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