DD216898A1 - COUNTERFEITING DOUBLE SNAIL - Google Patents

Abstract

The invention relates to a twin-screw in twin-screw extruders with opposite kaemmenden screws for plasticizing. Homogenizing and extruding plastic mass, in particular polymeric materials such as PVC, polyethylene, polyamide and. a. The aim of the invention is to improve the throughput and the product quality of the extrudate of twin screw extruders and at the same time reduce the energy consumption. The invention has for its object to provide quasi-double screws a) a maximum throughput at Gewaehrleistung a predetermined Mindestmischgueteb) a maximum Mischguete at Gewaehrleistung a predetermined Mindestdurchsatzleistungc) a maximum throughput at Gewaehrleistung an optimally high Mischguete and optimally low Antriebsbedarfd) a maximum Mischguete With the guarantee of an optimally high throughput and an optimally low drive requirement, the object is achieved by forming four dimensionless ratios which reflect the mutual dependence of the design parameters of the twin screw and assume defined ranges of values according to the tasks a) to d) , The invention finds application in twin-screw extrusion for the production of semi-finished and finished products.

Description

Counter-intermeshing twin screw Field of application of the invention

The invention relates to a twin screw in twin-screw extruders with counter-rotating meshing screws for plasticizing, homogenizing and extruding plastic masses, in particular polymeric materials such as PVC, polyethylene, polyamide and others.

Characteristic of the known technical solutions

The known screws for processing plastic masses in screw presses with two intermeshing screws have a wide variety of constructional features, which are determined by the respective processing processes to be implemented with these screws. (In the case of twin-screw extruders loaded with solid material, for example in the form of powder, granules or fibers, the process steps are conveying, preheating and precompressing the solid starting material in the solid state, as well as melting and compressing, homogenizing and extruding If the twin-screw extruder is charged with melt and / or fluid, then only the processes conveying the melt for pressure build-up, homogenization and pressing out are to be carried out in the same machine.

There are already a number of screw constructions known which aim to ensure a controlled introduction of energy into the processing material, a good homogenization of the material and high throughput rates.

The solutions according to DD-WP 90628 and DD-VVP 125258, however, concern only single-screw or multi-worm or double-flight worms.

The invention DD-WP 134616 is based on a solution which provides that at least one screw channel is designed cross-sectionally that are formed by a plurality of preferably parallel to the screw land extending and offset in their longitudinal profile arranged tracks. This is an adaptation of the Querschnittsε geometry to the Piastizier- and conveying process can be achieved, which makes it possible to fully utilize the solid pressure for a gentle deformstive stress and optimal mixing of the processing material and to realize optimal heat transfer conditions. The inventions according to DD-AP 109826 and DE-AS 1802593 provide that working surfaces are formed between helically guided Schnekken webs and worm grooves and working areas in Zwichelbereich the worm or that a given supplied heat energy is realized in conjunction with an internal heating of the worm, the prevent the return flow, increase the melt pressure at the discharge end, to improve the homogenization and the delivery rate.

All known twin-screw embodiments including DE-PS 879913 and DE-PS 1007499 have in common that their functional properties in view of the required Oruckverlauf over the extruder length, the throughput behavior and with regard to a good mixing of the processed material is not satisfactory. All mentioned construction principles of combing dop- »

It is peculiar that the stated objectives should be achieved by redesigning a single constructive or technological feature. However, this procedure can not satisfy, unlike Einschnekken due to the pronounced intermeshing twin screws exchange ratio between all constructive \ ind technological parameters and the integral process variables (throughput, pressure build-up, mixing effect, drive power demand). Although a prevention of the backflow in the gusset area according to the design solution DE-PS 1802593 leads to an increase in the hate pressure at the discharge end of the extruder and to an improvement in the delivery rate. At the same time, however, the exchange frequency of the delivery volume between the individual screw chambers worsened over the length of the screw, the ionizing effect of the material located in the screw channel outside the gusset region decreases and the core strand known for intermeshing counter-rotating twin screws in the cross section of the screw channel, which is characterized by a poor mixing effect , increases in its dimensions. Although the controllable heat supplied to DD-AP 109826 improves the conditions for a controlled Piastizier- and conveying process in general, but here as in all other solutions mentioned, it is not the subject of the invention, the complex relationships between the design and technological parameters of the screw or of the extruder and the integral process variables for the constructive solution. In none of these cases is a direct minimization of the drive power requirement of the twin screws achieved or desired.

Object of the invention

The aim of the invention is to improve the throughput and the product quality (homogeneity) of the extrudate of twin-screw extruders and at the same time reduce the energy expenditure for extrusion.

Presentation of the essence of the invention

The invention has the object of providing meshing twin screws to schaff s, taking into account the mutual dependence of the constructive parameters axial play, radial play, pitch, screw diameter and Schneckeneingriffsgrad (ratio of radial play and worm thread depth) with the processing material adapted fast and gentle promotion of polymer melts and / Or other fluids

a) a maximum throughput while ensuring a predetermined minimum mixing quality (quality),

b) a maximum mixing quality while ensuring a specified minimum throughput,

cj a maximum throughput while ensuring an optimal mix quality and an optimal low drive requirement and

d) a maximum mixing quality while ensuring an optimal high throughput and an optimally low drive requirement

achieve...

According to the invention, the object is achieved in that the dependence between said design parameters of a counter-meshing twin screw can be described by the following dimensionless ratio indicators, which according to the tasks a) to d) assume the following value ranges given in Table 1.

Relationship code

tasks

 benstellunc

K

K.

0.50 to 0.52

0.159 to 0.163

4.16 to 4.32

0.81 to 0.85

from 0.37 to 0.39

.192-.196

4.37 to 4.55

0.82 to 0.86

0.39 to 0.41

0.176 to 0.182

4.56 to 4.74

0.83 to 0.87

0.39 to 0.41

0.113 to 0.119

7.06 to 7.35

0.75 to 0.79

T (D

JT O are. 1

O IK

'H

, , .-,. , ... - 6 S e tting s p e c tio n 1

The invention will be explained below in four embodiments.

Example 1 ' : ".'

The design of a twin screw according to the solution according to the invention according to the object a) is characterized in that the design parameters depicted in FIG. 1 assume the values indicated in Table 2.

Example 2 '.

The design of a twin screw according to the solution of the invention according to the task b) is characterized in that the structural parameters shown in Figure 1 assume the values given in Table 2.

Example 3 ... '

The design of a twin screw according to the solution according to the invention according to the task c) is characterized in that the structural parameters shown in Figure 1 take the values indicated in Table .2.

Example 4

The design of a twin screw according to the invention solution according to the problem d) is characterized by the fact that the design parameters depicted in FIG. 1 assume the values indicated in Table 2.

^ ~ "" ^. "Execution" ^ ~ "* - ^. example 1 2 ..; 3 .. 16o Constructive ^ "" ^ - ^^^ parameters ^ *** \ ^ _ 125 125 160 137.80 Inner corner diameter, D (mm) 95.55 97.00 125.60 11.10 Screw core diameter, d (mm.) 14,74 14.01 '.. 17,20 92,50 Flight depth, H ₀ · (mm) 92.12 73.74 95 »56 200 Aisle width, W ₀ (mm) 200 149 200 21.80 Pitch, t (mm) 27.02 20.81 21.80 ^ 2.45 Pitch angle, <* (°) 2.51 2.24 2.51 -. 2.51 Basic game S ₀ . (Mm) 2.51 2.51 2.51 Backlash, S _f - (mm)

Table 2

Claims (1)

Invention claim 1 * Counter-intermeshing twin screw in Doppelschnekkxtrudern characterized in that the dimensionless ratio of the interdependent structural parameters (Schnekkenaußendurchnserser, Schneckenkerndurchmaß, flight depth, aisle width, pitch, pitch angle, basic clearance and Flankenspie-1) for securing - a maximum throughput while guaranteeing a given minimum mixing quality (quality) the following value ranges K ₁ = 0.50-0.52, K ₂ 0.159-0.163, K ₃ * 4.16-4.32 and K ₄ β 0.81-0.85, but preferably the VVerte K ₁ = 0.51, K ₂ β 0.161. K ₃ = 4.24 and K ₄ = 0.83, - a maximum mixing quality while ensuring a specified minimum throughput the following value ranges K ₁ > 0.37-0.39 / K ₂ «0.192-0.196, K ₃ = 4.37-4.55 and K ₄ «0.82-0.85, but preferably the values K a 0.38,, K ₂ '0.194, K ₃ = 4.46 and K ₄ = 0, 84, -. a maximum throughput while ensuring an optimal mix quality and an optimally low drive requirement the following value ranges K ₁ »0.39-0.41, K ₂ 0.176-0.182, K ₃ » 4.56-4.74 and K ₄ a 0.83 -0.87, but preferably the values K ₁ = 0.40, K ₂ . β 0.179, K ₃ 4.65 and K ₄ «0.85, - a maximum mixing quality while ensuring an optimal high Durznsstzleistung and an optimal low drive requirement following ranges of values K = 0.39-0.41, K ₂ = 0.113-0.119, Ι < ₃ 7.06-7.35 and K. = 0.75-0.79, but preferably the values K = 0.40,. K ₉ = 0.116, K _x »7.21 and Κ _Λ = 0.77 accept. For this oin sheet drawings.