Apparatus and method for forming polymer crumb

Abstract

The present invention provides a contractor apparatus and method for removing solvent from a polymer cement. The resulting polymer is substantially free of solvent and exhibits improved oil absorption and lower fines. In one aspect, a contractor is provided including a cylindrical casing having a high pressure section, a convergence section, a high velocity section, a divergence section, and a discharge section. The polymer cement is introduced into the high pressure section to significantly and unexpectedly improve solvent removal. The convergence and divergence sections have cross-sectional areas that correspond to an effective angle from about 4° to about 65°, such as 6°. The polymer cement is mixed with high pressure steam. After converging, the polymer cement forms more uniform droplets due to high shear of steam. In the divergence and discharge sections, the polymer is substantially devolatized.

1. A contactor for separating the solvent from the polymer in a polymer cement, said contactor comprising:
 (a) a tubular casing comprising 
 (i) a first section having a constant outer diameter, an inlet for the polymer cement, and means for the introduction of steam, whereby said polymer cement and said steam are mixed together and droplets of solvent begin to form; and  
 (ii) a second section of increasing inner diameter such that said second section has a diverging cross-sectional area with an effective angle of divergence of about 6°; and  
 (iii) a third section having a constant inner diameter and means for discharging said polymer and said solvent which have been separated from the polymer cement; and  
 
 (b) an insert positioned within the tubular casing such that an annulus is formed between the tubular casing and the insert to allow flow of said polymer cement, droplets of said solvent, and steam through the annulus, said insert comprising 
 (i) a first portion having a constant outer diameter and which is positioned such that it extends in said first section of the tubular casing; and  
 (ii) a second portion which has an increasing outer diameter and which is positioned within said first section of the tubular casing to provide the annulus with a converging cross-sectional area that corresponds to an effective angle of convergence of about 6°; and  
 (iii) a third potion having a constant outer diameter and which is positioned within said first, second and third sections of the tubular casing to provide the annulus with 1) a high shear section with a substantially constant cross-sectional area between said first section of the tubular casing and said third portion of the insert wherein the velocity of the polymer cement, droplets of steam, and steam flowing through the annulus increases to supersonic speed and a uniform distribution of droplets is established; and 2) a diverging cross-sectional area, between said second section of the tubular casing and said third portion of the insert, that corresponds to an effective angle of divergence of about 6°, whereby the pressure within the annulus drops such that a vacuum is created by the pressure differential, resulting in rapid de-volatilization of the solvent, thus providing separation of the solvent from the polymer.