Continuous conveying process and device for shear-sensitive fluids

Abstract

The invention relates to a process for continuously conveying shear-sensitive fluids, in particular polymer latices or plastics dispersions, which is accompanied by the taking of samples and the processing and analysis thereof, to a device for implementing the process and to a new double-long-stroke reciprocating pump.

1 . Process for continuously conveying shear-sensitive fluids having a viscosity of up to 100,000 mPa.s with a pump capacity of 10 ml/h to 100 l/h, characterised in that the fluid is aspirated via at least one clearance-free, positive valve ( 4 ) by a piston ( 8 ) of a double-long-stroke reciprocating pump ( 3 ) while fluid is synchronously emitted by the second piston ( 9 ) from the second piston chamber ( 24 ) likewise via at least one additional clearance-free, positive valve ( 5 ) towards the conveying side and after total evacuation of the second piston chamber ( 24 ) the valve ( 4 ) is opened on the emission side and closed on the suction side while valve ( 5 ) is closed on the emission side and opened on the suction side and the direction of motion of the pistons ( 8 ,  9 ) is synchronously reversed, whereby the pistons ( 8 ) and ( 9 ) are located on a spindle ( 14 ).  
     
     
         2 . Process according to  claim 1 , characterised in that the shear-sensitive fluid is conveyed in a recirculating loop ( 2 ) which is coupled to a reactor ( 1 ).  
     
     
         3 . Process according to claims  1  and  2 , characterised in that the shear-sensitive fluid is a polymer latex or a plastics dispersion.  
     
     
         4 . Process according to claims  2  and  3 , characterised in that the fluid is pumped into the region of reduced pressure via an overflow valve ( 6 ) or a sluice which is connected between the recirculating circuit ( 2 ) and a region of reduced pressure.  
     
     
         5 . Process according to  claim 3  to  4 , characterised i that the region of reduced pressure is part of a metering loop ( 7 ) which is parallel to the recirculating loop ( 2 ) and by way of metering devices exhibits at least one calibrated vacuum vessel with pressure gauge for determining monomer concentration of the polymer latex.  
     
     
         6 . Device for implementing the process according to  claim 1 , exhibiting a double-long-stroke reciprocating pump ( 3 ), at least one clearance-free, three-way valve ( 4 ) which is positively controlled via a contact switch ( 26 ) of the double-long-stroke reciprocating pump ( 3 ) and at least one clearance free, three-way output valve ( 5 ) which is likewise positively controlled via a contact switch ( 26 ) of the double-long-stroke reciprocating pump ( 3 ).  
     
     
         7 . Device according to  claim 6 , characterised in that it is connected to a recirculating loop ( 2 ) which is coupled to a reactor ( 1 ).  
     
     
         8 . Device according to  claim 7 , with an overflow valve ( 6 ) or a sluice on the emission side of the conveying device in the recirculating loop for transporting fluid into a region of reduced pressure.  
     
     
         9 . Low-pulsation, clearance-free, double-long-stroke reciprocating pump with a pump capacity of 10 ml/h to 100 l/h for conveying shear-sensitive fluids having a viscosity of up to 100,000 mPa.s, exhibiting two pistons ( 8 ,  9 ) on a common drive spindle ( 14 ), an angle-stroke gearing ( 10 ) with control gearing ( 11 ) connected upstream for driving the pistons ( 8 ,  9 ), a ring ( 12 ) for adjusting the stroke volume of the pump heads ( 23 ,  24 ), a contact switch ( 26 ) for changing the direction of rotation, an initiator disc ( 27 ) and also double seals on the head of the pistons ( 23 ,  24 ).  
     
     
         10 . Double-long-stroke reciprocating pump according to  claim 9 , characterised in that the spindle ( 14 ) exhibits an anti-torsion device.  
     
     
         11 . Double-long-stroke reciprocating pump according to claims  9  and  10 , characterised in that the spindle ( 14 ) is a telescopic spindle and replaces the adjusting nut ( 12 ).  
     
     
         12 . Double-long-stroke reciprocating pump according to  claims 9  to  11 , characterised in that the movement of the piston is controlled via a hydraulic system instead of the angle-stroke gearing ( 10 ) with control gearing ( 11 ) connected upstream.