Meth Acrylic Esters of Polyalkoxylated Trimethylolpropane

Oligomeric agents were prepared by condensing trimethylolpropane with ethylene and/or propylene oxides and capping with acrylic acid. These materials were subsequently crosslinked using 2,2 -azobisamidinopropane dihydrochloride, which formed superabsorbent swellable hydrogel addition polymers and were useful as components in diapers or in feminine hygiene products. 

An autoclave was charged with trimethylolpropane (77 g) and 45% aqueous KOH (0.5 g) and then azeotroped at 80°C and 20 mbar. The mixture was next treated with ethylene oxide (759 g) at, 45°C to 155°C and reacted at elevated pressure until no further change in pressure was observed. The mixture was stirred an additional 30 minutes at 150°C and then treated with propylene oxide (167 g) at 120°C to 130°C. The reactor was purged, the contents cooled to 60°C, and the catalyst removed by filtration. The product was isolated and consisted of 30-tuply ethoxylated and 5-tuply propoxylated trimethylolpropane. 

The Step 1 product (1427 parts) was converted into the corresponding acrylate ester by treating with acrylic acid (216 parts), sulfuric acid (5 parts) in methyl-cyclohexane (345 parts), hydroquinone monomethyl ether (3 parts), triphenyl phosphite (1 part), and hypophosphorous acid (1 part). The reaction continued until 44 parts of water were removed before beginning the vacuum distillation. The residue was purified by filtering through a K300 filter, and the acid number was determined. The product viscosity was adjusted to 330 mPas by the addition of 96 parts of acrylic acid, and a colorless product was isolated. 

TABLE 1. Properties of hydrogels prepared by free radically polymerizing the corresponding triacrylate with 2,2 -azobisamidinopropane dihydrochloride. 

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Title (Meth)Acrylic Esters of Polyalkoxylated Trimethylolpropane... 

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