Hybrid acrylic-urethane dispersions

Information on the preparation of hybrid acrylic-urethane dispersions by synthesis, published so far is quite scarce. More detailed data on this process are available only in the patent literature. 

The basic process was first patented by Inmont, USA, in 1982 [9]. They simply claimed polymerisation of vinyl polymers in DPUR. In 1986, a patent for another method of preparation of hybrid acrylic-urethane dispersions (diluting of prepolymer-ionomer with monomers, emulsifying the resulting solution in water and polymerisation) was granted to Witco, USA [26]. 

In subsequent years the number of patents dealing with hybrid acrylic-urethane dispersions increased rapidly, and approximately 30 patents have been granted so far worldwide, the majority in Japan. 

Based on this brief literature survey, it seems quite clear that not all features of the hybrid acrylic-urethane dispersions have been studied so far. The purpose of the present study is to clarify the effect of various factors on the properties of acrylic/styrene-urethane dispersions. Some results of preliminary investigations of the particle morphology will also be revealed. 

One can also make combined acrylic/urethane (hybrid) aqueous dispersions (33). Acrylic monomers are emulsion polymerized in the presence of an aqueous dispersion of a hydroxy-terminated polyurethane. The polyurethane stabilizes the aqueous dispersion, minimizing need for surfactant. Coalescence requires balance of the Tg of both the urethane and acrylic parts of the system. Compositions based on an IPDl/polypropylene glycol/DMPA urethane with styrene/methyl methacry-late/butyl acrylate are reported to form films at low temperatures. 

MAA) and the resultant polymerization gave a urethane/acrylate hybrid dispersion [568]. The urethane/acrylic hybrid had markedly improved water resistance over the physical blend of the components. Polyurethane/acrylic hybrids were compared with polyurethane/acrylic waterborne blends, with increased phase mixing in the hybrids observed, resulting in improved mechanical properties [569]. 

Uses Surf, modifier, mar resist, aid, antiblocking agent for aq. coatings, wood coatings, varnishes, industrial coatings, acrylic and styrene/acrylic disps., urethane disps., hybrid systems, water-reducible alkyds Features Improved scratch/metal mark resist. uniform matting Properties Micronized disperses easily in aq. coatings without use of added hydrophilic surfactants Lanco 1588 LF [Lubrizol]... 

Hybrid aqueous dispersions were prepared containing both acrylic resins and polyurethane to provide enhanced properties for coating applications. Nanosized (approximately 50 mn) hybrid latexes were prepared at 30 C by the redox-initiated miniemulsion polymerisation of n-butyl methacrylate monomer in the presence of a urethane prepolymer. A stabiliser, of low molecular weight and low water solubility, was required to obtain stable particles of the required size. 7 refs. 

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