SU1296441A1 - Screw for treating polymeric materials - Google Patents

Abstract

The invention relates to equipment for the processing of polymeric materials, in particular to augers for the processing of polymeric materials. The aim of the invention is to improve the quality of the polymer melt by intensifying the process of its mixing. To achieve this goal, the screw consists of several zones, in particular mixing and injection zones. The auger is provided with screw ribs with a pressure surface on the side of the discharge zone. The auger is made with a constant in magnitude and varied ush in azimuth by the eccentricity of the core in the mixing zone to form helical channels of variable depth. The eccentricity of the core is chosen equal to the height of the screw edge of the screw. Through holes are made in the core in the mixing zone. The length of the holes is selected in the range of 0.2-1.5 screw diameter. The cross-section of the cross section of the holes is made decreasing from the longitudinal axis of the screw in the direction of decreasing the depth of the screw channel and from the forcing surface of the screw rib towards the pressure zone. The cross-sectional dimensions of the through holes of the subsequent core section in the direction of the discharge zone are chosen to be smaller than the cross-sectional dimensions of the through holes of the previous core core section. The polymer melt during the rotation of the screw moves to the mixing zone. Then, in the mixing zone, it breaks up into separate streams and flows through the through holes. Next, the polymer melt exits through holes, is poured into one stream. The flow moves further in the direction of the injection zone, and again goes to the through holes in the next section of the core in the mixing zone. This process is repeated. The use of the invention makes it possible to intensify the process of its mixing by means of multiple separation and merging of polymer melt and, consequently, to improve its quality. 1 hp f-ly, 6 ill. lO (L Yu co 05 4 4

Description

The invention relates to equipment for the processing of polymeric materials, in particular to augers for the processing of polymeric materials.

The purpose of the invention is to improve the quality of the polymer melt by intensifying the process of mixing it.

FIG. 1 shows a pork for processing polymeric materials, general view; in fig. 2-4 - the same, a cross-section in the mixing zone with a different arrangement of through holes; in fig. 5, 6 is a diagram for determining the length of through holes.

The auger consists of a zone 1-4 of transportation, melting, mixing and injection, respectively. The auger is provided with screw ribs 5 with an injection surface on the side of the injection zone 4. The auger is made with a constant magnitude and a change in y-Sh. I in azimuth eccentricity €. the core 6 in the mixing zone 3 to form the screw channels 7 of variable depth. The eccentricity of core 6 is chosen equal to the height of the screw rib 5 of the screw. Through holes 8 are made in the core 6 in the mixing zone 3. The length of the holes 8 is 1 in the range of 0.2-1.5 auger diameter. The cross-sectional area of the holes 8 is made decreasing from the longitudinal axis 9 of the auger in the direction of decreasing the depth of the screw drip 7 and from the injection surface O of the screw rib 5 in the direction of the injection zone 4. The cross-sectional dimensions of the through holes 8 of the next in the direction of the discharge zone 4 of the core section 6 are chosen to be smaller than the cross-sectional dimensions of the through holes 8 of the previous core section. Through holes 8 can be made intersecting, parallel, intersecting. The edges of the through holes 8 are made with radii R from the entrance and exit of the polymer melt. In this case, about R 00.

The screw works in the following way.

The polymer melt during the rotation of the auger from the zone 1 of transportation through zone 2. The meltpear moves to zone 3 of mixing. In the latter, the polymer melt, breaking up into separate fluxes, flows through the through holes 8, made in the core b in the mixing zone 3. Next, the polymer melt comes out of the through holes 8, merges into one stream, which, moving further in the direction of the discharge zone 4, again goes into the through holes 8 of the next (in the direction of the discharge zone 4) core 6 section. The process repeats according to the number of through holes 8 of the core 6 in the mixing zone 3 (according to the number of core sections in this zone). The quality of the mixture of the polymer melt with various ingredients depends on the total strain and stresses.

the shift developed in the processed melt, as well as from the formation of new phase interfaces. At the same time, developed stresses and shear deformations

in the polymer melt depends on the geometrical dimensions of the through holes 8. To ensure high values of shear stresses and, consequently, a high intensification of the mixing process of zone 3, the length of the through holes 8 of the core 6 in this

zone should be maximized. The maximum possible length (t) of the through hole 8 is determined by the expression

 l, 5 ()

cos a

where t is the edge pitch;

α-angle between the axis of the through-hole and the longitudinal axis of the screw; b - the width of the ridge of the screw rib.

For single-thread screws, t d, where d is the diameter of the screw.

The maximum length of the through holes 8 is 1.5 dia. Of auger. The minimum length of the through holes 8 is equal to .5 auger diameter. The minimum length of the through holes 8 is determined from the condition that these holes can be made in the core, based on the magnitude of the eccentricity (which is here chosen to be equal to the height of the screw rib 5, the core blocking the channel in the extruder body — not shown). approximately equal to 0.1 diameter p) some. When the eccentricity is e, the minimum length of the through hole 8 in the core 6 in the mixing zone 3 is approximately equal to

2e, i.e. 0.2 screw diameter. The possibility of varying the length of the through holes 8 of the core 6 in the mixing zone 3 makes it possible to optimize the magnitude of the developed shear deformation required to improve the quality of the polymer melt. The shear stress and pressure in the polymer melt increase with approaching the injection surface o. screw ribs 5 of the screw, as well as reducing the depth of the screw channel 7 in the gap between the extruder body and the core 6 in the mixing zone 3 due to the roller effect. Therefore, the cross-sectional area of the holes 8 is made decreasing from the screw longitudinal axis 9 in the direction of decreasing the depth of the screw channel 7 and from the discharge surface of the screw rib 5 towards the injection zone 4. The cross-sectional dimensions of the through holes 8 that follow in the direction of the discharge zone 4 of the core 6 section are chosen to be smaller than the cross-sectional dimensions of the through holes 8 of the previous core section b, as the pressure and magnitude of the developed stress deformations and

shift, i.e. improved polymer melt mixing.

Thus, the use of the invention allows, through multiple separation and mixing of polymer melt streams, to intensify the process of its mixing and, consequently, to improve its quality.

Claims (2)

1. Screw for processing polymeric materials with a longitudinal axis, zones of transportation, melting, mixing and injection, screw ribs with a pumping surface on the side of the pumping zone and constant and changing yush.im azimuth eccentricity of the core in the mixing zone to form variable depth screw channels, FIG. g In order to improve the quality of the polymer melt by intensifying its mixing process, the eccentricity of the core is chosen to be equal to the height of the screw auger rib, and through holes in the core in the mixing zone are made in the range of 0.2-1.5 of the screw diameter, and the cross-sectional area of the holes is made decreasing from the longitudinal axis of the screw in the direction of decreasing the depth of the screw channel and from the pressure surface of the screw edge towards the pressure zone. 2. The screw according to claim 1, characterized in that the cross-sectional dimensions of the through-holes of the subsequent section of the core in the direction of the injection zone are chosen to be smaller than the cross-sectional sizes of the through-holes of the previous section: core. 9 Fig 6