John M. Geurts

Formation and Crosslinking of Latex Films through the Reaction of Acetoacetoxy Groups with Diamines under Ambient Conditions

We investigated the processes of film formation, polymer diffusion, and crosslinking of latex films at ambient temperature, using low Tg methacrylate latex bearing acetoacetoxy groups, and curing the systems with 1,6-hexanediamine as the crosslinker. The addition of diamine induces floc formation, which modifies the rheological properties of the dispersion and increases its drying rate when coated onto a substrate. The crosslinking reaction between diamine and acetoacetoxy groups occurs at a rapid rate, even in the dispersed state. Although the crosslinking reaction precedes polymer diffusion in the two systems we examined, latex films with relatively good solvent resistance are obtained.

Latexes with intrinsic crosslink activity

In order to develop and study ‘two pack in one pot’ systems, i.e. binder systems consisting of a blend of complementary reactive latexes, epoxy- and amino-functional latexes were prepared and characterised, with atte lion especially directed to control of the number of functional groups and control of the molecular weight. The investigation is focused on the control of the molecular weight of epoxy-functional latexes and on the incorporation of amino groups in latexes by using amino-functional methacrylic monomers. To determine the reactivity of the epoxy and amino groups and to check which factors influence the crosslink reaction a number of blends were prepared from both solution and emulsion copolymers and dried at ambient temperatures. It was found that the major factors, which affect the efficiency of crosslinking, are the Tg and the molecular weight of the copolymers and, in the case of a ‘two pack in one pot system’, the rate of the polymer-polymer reaction in relation to that of the polymer-polymer interdiffusion.

Molecular mass control in methacrylic copolymer latexes containing glycidyl methacrylate

Results are presented on the preparation and characterization of batch emulsion copolymers of butyl methacrylate and glycidyl methacrylate (GMA). The two main problems occurring during an emulsion copolymerization with GMA are partial hydrolysis of the epoxy groups and internal crosslinking of the latex particles formed. The influence of chain transfer agents (CTA) on the degree of crosslinking was investigated. Furthermore, the effect of reaction temperature and the addition of methacrylic acid on the sol/gel content of the polymer formed and on the rate of epoxy hydrolysis were investigated. It was found that lowering the reaction temperature did not increase the sol content; however, it significantly decreased the extent of hydrolysis. The addition of a CTA (especially CBr4) increased the sol content of the polymer, and good control over the molecular mass was achieved. The addition of methacrylic acid showed that this monomer can be used without any complications with respect to the control of the sol content of the polymer formed.

Preparation of epoxy-functionalized methyl methacrylate-butadiene-styrene core-shell particles and investigation of their dispersion in polyamide-6

Functional core—shell impact modifiers of glycidyl methacrylate (GMA) functionalized methyl methacrylate—butadiene—styrene (MBS) have been prepared via a seeded semi-continuous emulsion polymerization. These functional MBS—GMA particles were blended with polyamide-6. Investigations by transmission electron microscopy showed a very good dispersion of the particles in the polymeric matrix, compared with blends of MBS with polyamide-6 where a third functional polymer styrene—maleic anhydride was added.

Some Trends in the Preparation and Use of Reactive Latices

Reactive polymers constitute an important class of binder materials for application in, e.g., coatings and resins. Traditional solvent-borne systems consist of low molecular weight material dissolved in a suitable organic solvent. During application and evaporation of the solvent network formation occurs, resulting in an increase in the molecular weight, the viscosity and the glass transition temperature (Tg). Through the formation of a network these thermoset resins attain their desired properties: insolubility in most organic solvents, good water resistance, good hardness development, and good resistance against blocking.