Synthesis, characterization and evaluation of macromonomers used to prepare rheology modifiers for possible improvement of the pigmentation of decorative coatings

Sprong, Ewan (2000-03)

Thesis (MSc)--Stellenbosch University, 2000.


ENGLISH ABSTRACT: There is a decrease in viscosity when universal colorants are added to the latex coating system. Two different routes were taken to investigate this problem. The first was to investigate the thickening mechanism of the coating system. For this purpose six different hydrophobically modified alkali-soluble (HASE) thickeners were synthesized. The second was to compile new color concentrate formulations. The HASE thickeners consist of acrylic acid and a second associative monomer. The associative monomer (macromonomer) contained a long chain hydrophilic segment, terminated with a hydrophobic group. The hydrophilic segment consists of polyethoxylation, situated between the ethylenic unsaturation at one end of the molecule and the terminal hydrophobe at the other end. Three different macromonomers were prepared by coupling the hydroxyl end groups of three commercially available nonionic surfactants with either acrylic acid or acryloyl chloride. A much higher yield of macromonomer was obtained when the nonionic surfactants were reacted with the acryloyl chloride. Six HASE thickeners were synthesized by means of free radical addition polymerization. The first three HASE thickeners had the same backbone length and each thickener containing one type of hydrophobic macromonmer. The hydrophobic macromonomers differed in the length of their repeating oxyethylene units. They contained either 20, 50 or 100 oxyethylene units. The next three HASE thickeners were very similar to the first three except that 5% of the acrylic acid in the backbone was substituted with a second, phosphated, macromonomer, meaning that these thickeners each contained two types of macromonomers. These thickeners were then introduced into a standard latex coating formulation. By comparing the rheology profiles of the different coatings it was possible to determine the thickening efficiencies of the different thickeners. These coatings were also evaluated for their viscosity stability when tinted with a universal colorant. The HASE thickeners containing the second phosphated macromonomer showed superior thickening efficiency. All six coatings showed excellent stability on tinting with a universal colorant. Following the second route of investigation, eight universal colorant formulations consisting of only one polymeric dispersant in each of the formulations as sole wetting and dispersing additive were made up. A commercially available universal colorant was used as standard against which the new formulations were tested. The colorants were tested for color strength, their compatibility with the different coating groups, and the rheology profiles of the tinted vs. untinted coating systems. The two colorant formulations that contained EFKA 4550 as the polymeric dispersant performed very well in all the coating groups.

AFRIKAANSE OPSOMMING: Daar is 'n afname in viskositeit wanneer universele kleurstowwe by die lateks-bedekkingsisteem gevoeg word. Twee verskillende roetes is gevolg om die probleem te ondersoek. Die eerste was om die verdikkingsmeganisme van die bedekkingsisteem te ondersoek. Vir die doel is ses verskillende hidrofobies gemodifiseerde alkali-oplosbare (HASE)-verdikkers gesintetiseer. Die tweede was om nuwe kleurkonsentraatformulerings saam te stel. Die HASE-verdikkers bestaan uit akrielsuur en 'n tweede assosiatiewe monomeer. Die assosiatiewe monomeer (makromonomeer) bevat 'n langketting-hidrofiliese segment, met 'n hidrofobiese endgroep. Die hidrofiliese segment bestaan uit herhalende oksi-etileen eenhede, tussen die etileniese onversadigdheid aan die een punt van die molekuul en die hidrofobiese endgroep aan die ander punt. Drie verskillende makromonomere is voorberei deur die koppeling van die hidroksiel-endgroepe van drie kommersieel beskikbare anioniese sepe met akrielsuur of akriloielchloried. 'n Baie hoër opbrengs van makromonomere is verkry toe die anioniese sepe met die akriloielchloried gereageer is. Ses HASE-verdikkers is gesintetiseer deur middel van vrye radikaal addisie polimerisasie. Die eerste drie HASE-verdikkers het dieselfde ruggraatlengte en elke verdikker bevat een tipe hidrofobiese makromonomeer. Die hidrofobiese makromonomere verskil in die lengte van hul herhalende oksi-etileen eenhede. Die hidrofobiese makromonomere bevat of 20, 50 of 100 oksietileen eenhede. Die volgende drie HASE-verdikkers stem baie ooreen met die eerste drie behalwe dat 5% van die akrielsuur in die ruggraat vervang is deur 'n tweede, fosfaatbevattende makromonomeer, wat beteken dat hierdie verdikkers elk twee tipes makromonomere bevat. Hierdie verdikkers is in 'n standaard lateks bedekking formulering gevoeg. Deur die vergelyking van die reologie profiele van die verskillende bedekkings was dit moontlik om die verdikkings effektiwitiet van die verskillende verdikkers te bepaal. Hierdie bedekkings is ook geevalueer vir hulle viskositeits stabiliteit as dit met 'n universele kleurstof gekleur word. Die HASE-verdikkers wat die tweede fosfaatbevattende makromonomeer bevat, het uitstekende verdikkings effektiwiteit getoon. Al ses bedekkings het uitstekende stabiliteit getoon tydens kleuring met 'n universele kleurstof. Deur die tweede roete van ondersoek te volg, is agt universele kleurstof formulerings wat bestaan uit slegs een polimeriese dispergeermiddel opgemaak. 'n Kommersieel beskikbare universele kleurstof is gebruik as standaard waarteenoor die nuwe formulerings getoets is. Die kleurstowwe is getoets vir kleursterkte, hul verenigbaarheid met die verskillende bedekkingsgroepe, en die reologie profiele van die gekleurde teenoor die ongekleurde bedekkingsisteme. Die twee kleurstof formulerings wat EFKA 4550 as die polimeriese dispergeer middel bevat, het baie goed gevaar in al die bedekkingsgroepe.

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