Without any tank or impeller dimensions, it is difficult to make recommendations about how to improve the gear box, motor horsepower, or anchor size.  However, some educated guesses about tank and impeller dimension would suggest that the motor should not overload as long as the viscosity is less than 20,000 cp, which is viscous.
 
I suspect that your problems with the mixer becoming stuck during the addition of the methyl acetoacetate has more to do with poor bulk mixing than with excessive physical properties.  An anchor mixer does not do a good job of taking materials added at the surface and distributing them throughout the tank.  However you process takes place, you probably have an excess of the methyl acetoacetate near the surface of the tank.
 
Your best option to reduce the problems with the mixer becoming stuck is to reduce the rate of methyl acetoacetate addition, allowing time for it to be more uniformly mixed.  Depending on the thickness of the mixture, reducing the speed from 30 rpm to 25 rpm may actually improve the mixing, especially for drawing the addition off the surface.  Ultimately, a mixer capable of some top-to-bottom motion, such as a helical ribbon, would improve the batch uniformity.

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