Continuous free radial polymerization in a wiped-surface reactor

A process of making a pressure sensitive adhesive composition by polymerizing one or more free radical polymerizable vinyl compounds which process comprises:

• (a) continuously feeding to a wiped surface reactor comprising a vessel and at least one rotor inside the vessel having a wiping portion located close to the inside surface of the vessel and a root portion spaced susbtantially further from the inside surface than the wiping portion wherein the root surface is wiped continuously during rotation of the rotor raw materials which comprise unpolymerized vinyl compounds without any substantial amount of polymerized vinyl compounds, and at least one initiator for free radical polymerization under the following conditions:
• (i) all raw materials being fed substantially free of oxygen, and
• (ii) at least one monomer being a liquid unpolymerized vinyl compound having a viscosity less than about 4000 centipoise which is fed under a pressure at least as high as the vapor pressure of the combined raw materials at the temperature to which the exotherm of the free radical polymerization brings them in the reactor;
• (b) reacting the raw materials to desired conversion;
• and
• (c) continuously withdrawing a polymeric material from the wiped surface reactor.

A process of making a pressure sensitive adhesive composition by bulk polymerizing one or more free radical polymerizable vinyl compounds which comprises:

• (a) continuously feeding to a wiped surface reactor comprising a vessel and at least one rotor inside the vessel having a wiping portion located close to the inside surface of the vessel and a root portion spaced substantially further from the inside surface than the wiping portion wherein the root surface is wiped continuously during rotation of the rotor raw materials which comprise a polymer syrup comprising at least one partially reacted vinyl monomer having been stabilized at a conversion of about 5 to 10 percent and at least one initiator for free radical polymerization, said raw materials being substantially free of oxygen;
• (b) reacting the raw materials to the desired conversion;
• and
• (c) continuously withdrawing a polymeric material from the reactor, said polymeric material having a bimodal molecular weight distribution.