Method for extruding plastic masses

Abstract

The invention relates to a process for extruding plastic compositions. The process in particular relates to the conveying, kneading and/or mixing of plastic compositions, in particular of polymer melts and mixtures of polymer melts, above all thermoplastics and elastomers, particularly preferably polycarbonate and polycarbonate blends, also with the incorporation of other substances such as for example solids, liquids, gases or other polymers or other polymer blends.

Claims

1. A process for extruding plastic compositions comprising the steps of providing a twin- or multi-screw extruder, and conveying or kneading and/or mixing a plastic composition in said twin- or multi-screw extruder, said extruder comprising screw elements with screws co-rotating in pairs and being fully self-wiping in pairs, wherein each screw has one of a generating screw profile and a generated screw profile consisting of arcs with non-infinite radiuses, each of the generating and generated screw profiles being axisymmetrial referring to one axis which passes through the point of rotation of the respective screw profile, and each of the generating and generated screw profiles comprises one sealing zone, one or more transition zones, one channel zone, one or more tip zones, one or more flank zones, and one or more grooved zones, and each screw profile consisting of a sequence of the one sealing zone—one of the transition zones—the one channel zone—another of the transition zones, wherein each sealing zone is a sequence of one of the tip zones—one of the flank zones—another of the tip zones, each channel zone is a sequence of one of the grooved zones—one of the flank zones—another of the grooved zones, and each transition zone is one of the flank zones, wherein each sealing zone of the screw elements is distinguished in that relative to the point of rotation of the screw profile, the flank zone has an angle δ_fb1 which is greater than or equal to half the aperture angle between the two barrel intermeshes (δ_fb1≧arc cos(0.5*a/ra))(wherein “a” is the centerline distance and “ra” is the outer screw radius”) , relative to the point of rotation of the screw profile, one tip zone has an angle δ_kb1 which is less than or equal to the difference of the tip angle of a single-flighted Erdmenger screw profile minus the aperture angle between the two barrel intermeshes (δ_kb1≦π-4*arc cos(0.5*a/ra)), relative to the point of rotation of the screw profile, the other tip zone has an angle δ_kb2 which is less than or equal to the difference of the tip angle of a single-flighted Erdmenger screw profile minus the aperture angle between the two barrel intermeshes (δ_kb2≦π-4*arc cos(0.5*a/ra)), and each channel zone is distinguished in that relative to the point of rotation of the screw profile, the flank zone has an angle δ_fb2 which is greater than or equal to half the aperture angle between the two barrel intermeshes(δ_fb2≧arc cos(0.5*a/ra)), relative to the point of rotation of the screw profile, one grooved zone has an angle δ_nb1 which is less than or equal to the difference of the tip angle of a single-flighted Erdmenger screw profile minus the aperture angle between the two barrel intermeshes (δ_nb1≦π-4*arc cos(0.5*a/ra)), relative to the point of rotation of the screw profile, the other grooved zone has an angle δ_nb2 which is less than or equal to the difference of the tip angle of a single-flighted Erdmenger screw profile minus the aperture angle between the two barrel intermeshes (δ_nb2≦π-4*arc cos(0.5*a/ra)).

2. The process as claimed in claim 1, wherein the sum of the angles of the tip and flank zones δ _kb1, δ _kb2 and δ _fb1 of the sealing zone is in the range from 0.75*δ _gz (the angle between two barrel intermeshes) to 2* δ_gb (the angle relative to the center point of the barrel bores) +δ_gz and the sum of the angles of the grooved and flank zones δ_nb1, δ_nb2 and δ_fb2 of the channel zone is in the range from 0.75*δ_gz to 2*δ_gb+δ_gz.

3. The process as claimed in claim 1, wherein the sum of the angles of the tip and flank zones δ_kb1,δ_kb2 and δ_fb1 of the sealing zone is in the range from δ_gz to δ_gb+δ_gz and the sum of the angles of the grooved and flank zones δ.sub.13 nb1, δ_nb2 and δ_fb2 of the channel zone is in the range from δ_gz to δ_gb+δ_gz.

4. The process as claimed in claim 1, wherein the transition zone consists of a flank zone.

5. The process as claimed in claim 1, wherein the screw profiles bring about linear sealing of the intermesh zone.

6. The process as claimed in claim 1, wherein the screw profiles bring about punctiform sealing of the intermesh zone.

7. The process as claimed in claim 1, wherein the maximum distance of the tip zones of the sealing zone of the screw profiles from the barrel is in the range from 0 to 0.05 times the centerline distance.

8. The process as claimed in claim 1, wherein the maximum distance of the tip zones of the sealing zone of the screw profiles from the barrel is in the range from 0 to 0.025 times the centerline distance.

9. The process as claimed in claim 1, wherein the screw elements are configured as conveying elements or mixing elements by extending the screw profiles helically in the axial direction.

10. The process as claimed in claim 1, wherein the screw elements are configured as a kneading element by extending the screw profiles in portions in an offset manner in the axial direction.

11. The process as claimed in claim 1, wherein clearances in the range from 0.1 to 0.001 relative to the diameter of the screw profile are present between screw elements and barrel and/or between neighboring screw elements.

12. The process as claimed in claim 1, wherein the plastic compositions are thermoplastics or elastomers.

13. The process as claimed in claim 12, wherein the thermoplastics used are polycarbonate, polyamide, polyester, polylactide, polyether, thermoplastic polyurethane, polyacetal, fluoropolymer, polyether sulfones, polyolefin, polyimide, polyacrylate, polyphenylene oxide, polyphenylene sulfide, polyether ketone, polyarylether ketone, styrene polymers, styrene copolymers, polyvinyl chloride or a blend of at least two of the stated thermoplastics.

14. The process as claimed in claim 13, wherein polycarbonate or a blend containing polycarbonate is used as the thermoplastic.

15. The process as claimed in claim 14, wherein the elastomer used is styrene-butadiene rubber, natural rubber, butadiene rubber, isoprene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, butadiene-acrylonitrile rubber, hydrogenated nitrile rubber, butyl rubber, halobutyl rubber, chloroprene rubber, ethylene-vinyl acetate rubber, polyurethane rubber, thermoplastic polyurethane, gutta percha, acrylate rubber, fluororubber, silicone rubber, sulfide rubber, chlorosulfonyl-polyethylene rubber or a combination of at least two of the stated elastomers.

16. The process as claimed in claim 1, wherein fillers or reinforcing materials or polymer additives or organic or inorganic pigments, or mixtures thereof, are added to the polymer.

17. A process for extruding plastic compositions comprising the steps of providing a twin- or multi-screw extruder, and conveying, kneading, and/or mixing a plastic composition in said twin- or multi-screw extruder, said extruder comprising screw elements with screws co-rotating in pairs and being fully self-wiping in pairs, wherein each screw has one of a generating screw profile and a generated screw profile consisting of arcs with non-infinite radiuses, each of the generating and generated screw profiles being axisymmetrial referring to one axis which passes through the point of rotation of the respective screw profile, and each of the generating and generated screw profiles comprises one sealing zone, one or more transition zones, one channel zone, one or more tip zones, one or more flank zones, and one or more grooved zones, and each screw profile consisting of a sequence of the one sealing zone—one of the transition zones—of the one channel zone—another of the transition zones, wherein each sealing zone is a sequence of one of the tip zones—one of the flank zones—another of the tip zones, each channel zone is a sequence of one of the grooved zones—one of the flank zones—another of the grooved zones, and each transition zone is one of the flank zones.

Description

EXAMPLES

(1) Examples 1-11 present tests on a ZSK 40 Sc from Coperion Werner & Pfleiderer and a ZSK 32 Mc from Coperion Werner & Pfleiderer. The ZSK 32 Mc has a centerline distance of 26.2 mm and a barrel diameter of 31.8 mm. The ZSK 40 Sc has a centerline distance of 33.4 mm and a barrel diameter of 40.3 mm. The aperture angle between the two barrel intermeshes δ_gz amounts in the ZSK 32 Mc to approx. 69° and in the ZSK 40 Sc to approx. 68°. The double-flighted conveying elements used in the examples with an Erdmenger screw profile according to the prior art have a tip angle of approx. 20° on the ZSK 32 Mc and a tip angle of approx. 21° on the ZSK 40 Sc. The single-flighted conveying elements used in the examples with an Erdmenger screw profile according to the prior art have a tip angle of approx. 110° on the ZSK 40 Sc. The conveying elements used according to the invention and in the examples have a sealing angle of approx, 106° on the ZSK 32 Mc, consisting of a tip angle δ_kb1 of approx. 9′, a flank angle δ_fb1 of approx. 88° and a tip angle δ_kb2 of approx. 9°, and a channel angle of approx. 110°, consisting of a groove angle δ_nb1 of approx. 12°, a flank angle δ_fb2 of approx. 86° and a groove angle δ_kb2 of approx. 12°. The conveying elements used according to the invention and in the examples have a sealing angle of approx, 104° on the ZSK 40 Sc, consisting of a tip angle δ_kb1 of approx. 3°, a flank angle δ_fb1 of approx. 98° and a tip angle δ_kb2 of approx. 3°, and a channel angle of approx. 110°, consisting of a groove angle δ_nb1 of approx. 8°, a flank angle δ_fb2 of approx. 94° and a groove angle δ_kb2 of approx. 8°.

(2) Intermediate plates are introduced at a number of locations on the ZSK40 Sc, which serve to accommodate the measurement systems (see for example FIG. 29, intermediate plate (2)). These intermediate plates are likewise designated by the term barrel below for the purpose of simplification.

Comparative Example 1

(3) The twin-screw extruder (FIG. 28) comprises a structure consisting of 5 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (6). Barrel (2) contains a measurement point (10) for a melt temperature sensor. Barrel (3) contains a degassing opening (7). Barrel (4) is closed and barrel (5) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (8). The flange is followed by a valve (9) for throttling purposes. The internal diameter of valve (9) and line (8) amounts in each case to 15 mm, the valve length to 95 mm and the line length to 120 mm.

(4) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (10). The screw is then provided with 8 double-flighted conveying elements with the pitch 40 mm and length 40 mm and one conveying element with the pitch 40 mm and length 20 mm.

(5) At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h of Makrolon® 2805 (manufacturer: Bayer MaterialScience AG), the temperature (12) of the melt was measured at the end of the extruder in the flange (5) at various pressures adjusted by means of the pressure sensor (13) upstream of the valve (9). The inlet temperature of the melt into the twin-screw extruder was also measured (11). The extruder barrels (1, 2, 3, 4, 5), lines (6, 8) and the valve (9) were heated to 290° C. The results are shown in Table 1.

(6) TABLE-US-00001 TABLE 1 Pressure upstream of valve 20.6 bar 40.4 bar 60.1 bar 79.8 bar Inlet temperature (11) 320° C. 320° C. 319° C. 319° C. Outlet temperature (12) 334° C. 338° C. 342° C. 346° C. Outlet-inlet  14° C.  18° C.  23° C.  27° C. temperature differential

Example 2

(7) The extruder was of the same structure as in Example 1. In comparison with Example 1, the make-up of the screw downstream of the bush was changed as follows: the 8 double-flighted conveying elements with a pitch of 40 mm and length of 40 mm and the one conveying element with a pitch of 40 mm and a length of 20 mm were replaced by conveying elements according to the invention. The conveying elements have a pitch of 30 mm and a length of 30 mm and 11 units were placed on the screw. At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h of Makrolon® 2805 (manufacturer: Bayer MaterialScience AG), the temperature (12) of the melt was measured at the end of the extruder in the flange (5) at various pressures upstream of the valve (9). The inlet temperature (11) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5), lines (6, 8) and the valve (9) were heated to 290° C.

(8) The increase between the melt inlet and melt outlet temperature is distinctly lower when screw elements according to the invention are used in comparison with conventional double-flighted elements from Example 1, as is shown by the results in Table 2.

(9) TABLE-US-00002 TABLE 2 Pressure upstream of valve 20.3 bar 40.1 bar 60.2 bar 80.1 bar Inlet temperature (11) 321° C. 321° C. 322° C. 322° C. Outlet temperature (12) 328° C. 331° C. 334° C. 336° C. Outlet-inlet  7° C.  10° C.  12° C.  14° C. temperature differential

Example 3

(10) The extruder was of the same structure as in Example 1. In comparison with Example 1, the make-up of the screw downstream of the bush was changed as follows: the 8 double-flighted conveying elements with a pitch of 40 mm and length of 40 mm and the one conveying element with a pitch of 40 mm and a length of 20 mm were replaced by screw elements according to the invention and conventional single-flighted elements. Both types of elements have a pitch of 30 mm and length of 30 mm and 5 units of the screw elements according to the invention followed by 6 conventional single-flighted elements with a pitch of 30 mm and a length of 30 mm were placed on the screw. At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h of Makrolon® 2805 (manufacturer: Bayer MaterialScience AG), the temperature (12) of the melt was measured at the end of the extruder in the flange (5) at various pressures upstream of the valve (9). The inlet temperature (11) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5), lines (6, 8) and the valve (9) were heated to 290° C.

(11) The example compares conventional single-flighted conveying elements with the conveying elements according to the invention. The results in Table 3 reveal distinctly higher temperatures in the case of conventional single-flighted elements.

(12) TABLE-US-00003 TABLE 3 Pressure upstream of valve 20.7 bar 39.8 bar 60.2 bar 79.9 bar Inlet temperature (11) 320° C. 320° C. 320° C. 320° C. Outlet temperature (12) 334° C. 337° C. 340° C. 342° C. Outlet-inlet  14° C.  17° C.  20° C.  22° C. temperature differential

Comparative Example 4

(13) The twin-screw extruder (FIG. 29) comprises a structure consisting of 8 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (9). Barrel (2) contains a measurement point (12) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (10). Barrel (5) contains a measurement point (13) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (14) for a melt temperature sensor. The barrel (8) is open at the end, such that the figure-of-eight-shaped bore of the barrel is visible.

(14) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (12). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (13). The screw is then provided with 8 double-flighted conveying elements with a pitch of 40 mm and length of 40 mm.

(15) At various rotational speeds of the screws and a throughput of 80 kg/h of Makrolon® 2805 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (14)) of the melt was measured at the end of the extruder. The temperature was additionally measured with a manual thermometer (15) which was held in the melt at the open outlet. The inlet temperature (measurement point (11)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8) and line (9) were heated to 290° C. The results are shown in Table 4.

(16) TABLE-US-00004 TABLE 4 Rotational speed rpm 100 150 200 250 300 350 Inlet 319° C. 319° C. 318° C. 318° C. 318° C. 317° C. temperature (11) Outlet 324° C. 334° C. 339° C. 348° C. 350° C. 349° C. temperature (15) Outlet-inlet  5° C.  15° C.  21° C.  30° C.  32° C.  32° C. temperature differential

Example 5

(17) The twin-screw extruder (FIG. 29) comprises a structure consisting of 8 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (9). Barrel (2) contains a measurement point (12) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (10). Barrel (5) contains a measurement point (13) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (14) for a melt temperature sensor. The barrel (8) is open at the end, such that the figure-of-eight-shaped bore of the barrel is visible.

(18) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (12). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (13). The screw is then provided with 11 conveying elements according to the invention with a pitch of 30 mm and length of 30 mm.

(19) At various rotational speeds of the screws and a throughput of 80 kg/h of Makroion® 2805 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (14)) of the melt was measured at the end of the extruder. The temperature was additionally measured with a manual thermometer (15) which was held in the melt at the open outlet. The inlet temperature (measurement point (11)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8) and line (9) were heated to 290° C. The results in Table 5 reveal distinctly lower temperatures and temperature differentials between the inlet (11) and outlet (15) than in Table 4 in Example 4.

(20) TABLE-US-00005 TABLE 5 Rotational speed rpm 100 150 200 250 300 350 Inlet 321° C. 318° C. 318° C. 319° C. 319° C. 318° C. temperature (11) Outlet 321° C. 331° C. 333° C. 329° C. 342° C. 351° C. temperature (15) Outlet-inlet  0° C.  13° C.  15° C.  10° C.  23° C.  33° C. temperature differential

Example 6

(21) The twin-screw extruder (FIG. 29) comprises a structure consisting of 8 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (9). Barrel (2) contains a measurement point (12) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (10). Barrel (5) contains a measurement point (13) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (14) for a melt temperature sensor. The barrel (8) is open at the end, such that the figure-of-eight-shaped bore of the barrel is visible.

(22) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (12). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (13). The screw is then provided with 5 conveying elements according to the invention with a pitch of 30 mm and length of 30 mm. The screw was then provided with 6 conventional single-flighted conveying elements with a length of 30 mm and a pitch of 30 mm.

(23) At various rotational speeds of the screws and a throughput of 80 kg/h of Makrolon® 2805 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (14)) of the melt was measured at the end of the extruder. The temperature was additionally measured with a manual thermometer (15) which was held in the melt at the open outlet. The inlet temperature (measurement point (11)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8) and line (9) were heated to 290° C. The results in Table 6 reveal distinctly higher temperatures and temperature differentials between the inlet (11) and outlet (15) than in the process according to the invention in Table 5 in Example 5.

(24) TABLE-US-00006 TABLE 6 Rotational speed rpm 100 150 200 250 350 Inlet temperature (11) 317° C. 317° C. 318° C. 317° C. 318° C. Outlet temperature (15) 321° C. 330° C. 338° C. 345° C. 350° C. Outlet-inlet  4° C.  13° C.  20° C.  28° C.  31° C. temperature differential

Comparative Example 7

(25) The twin-screw extruder (FIG. 30) comprises a structure consisting of 9 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (12). Barrel (2) contains a measurement point (14) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (13). Barrel (5) contains a measurement point (15) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (16) for a melt temperature sensor. Barrel (9) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (10) (round). The flange is followed by a valve (11) for throttling purposes. The internal diameter of valve (11) and line (10) amounts in each case to 15 mm, the valve length to 95 mm and the line length to 120 mm.

(26) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (15). The screw is then provided with 8 double-flighted conveying elements of a pitch of 40 mm and length of 40 mm.

(27) At various rotational speeds of the screws and a throughput of 80 kg/h of Bayblend® T45 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (17)) of the melt was measured at the end of the extruder. The inlet temperature (measurement point (18)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8, 9), line (10, 12) and the valve (11) were heated to 240° C. The valve (11) is completely opened. The results are shown in Table 7.

(28) TABLE-US-00007 TABLE 7 Rotational speed rpm 150 250 350 Inlet temperature (18) 274° C. 274° C. 274° C. Outlet temperature (17) 285° C. 292° C. 300° C. Outlet-inlet  11° C.  18° C.  26° C. temperature differential

Example 8

(29) The twin-screw extruder (FIG. 30) comprises a structure consisting of 9 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (12). Barrel (2) contains a measurement point (14) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (13). Barrel (5) contains a measurement point (15) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (16) for a melt temperature sensor. Barrel (9) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (10) (round). The flange is followed by a valve (11) for throttling purposes. The internal diameter of valve (11) and line (10) amounts in each case to 15 mm, the valve length to 95 mm and the line length to 120 mm.

(30) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (15). The screw is then provided with 11 conveying elements according to the invention of a pitch of 30 mm and length of 30 mm.

(31) At various rotational speeds of the screws and a throughput of 80 kg/h of Bayblend® T45 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (17)) of the melt was measured at the end of the extruder. The inlet temperature (measurement point (18)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8, 9), line (10, 12) and the valve (11) were heated to 240° C. The valve (11) is completely opened. The results are shown in Table 8 and reveal lower temperatures than in Table 7 in Example 7.

(32) TABLE-US-00008 TABLE 8 Rotational speed rpm 150 250 350 Inlet temperature (18) 275° C. 275° C. 273° C. Outlet temperature (17) 281° C. 291° C. 297° C. Outlet-inlet  6° C.  16° C.  24° C. temperature differential

Comparative Example 9

(33) The twin-screw extruder (FIG. 30) comprises a structure consisting of 9 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (12). Barrel (2) contains a measurement point (14) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (13). Barrel (5) contains a measurement point (15) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (16) for a melt temperature sensor. Barrel (9) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (10) (round). The flange is followed by a valve (11) for throttling purposes. The internal diameter of valve (11) and line (10) amounts in each case to 15 mm, the valve length to 95 mm and the line length to 120 mm.

(34) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (15). The screw is then provided with 8 double-flighted conveying elements of a pitch of 40 mm and length of 40 mm.

(35) At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h of Bayblend® T45 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (17)) of the melt was measured at the end of the extruder in the flange (9) at various pressures (pressure measurement sensor (19)) upstream of the valve (11). The inlet temperature (measurement point (18)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8, 9), line (10, 12) and the valve (11) were heated to 240° C. The results are shown in Table 9.

(36) TABLE-US-00009 TABLE 9 Pressure upstream of valve in bar 13 40 70 Inlet temperature (18) 273° C. 274° C. 273° C. Outlet temperature (17) 291° C. 296° C. 301° C. Outlet-inlet  18° C.  22° C.  28° C. temperature differential

Example 10

(37) The twin-screw extruder (FIG. 30) comprises a structure consisting of 9 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (12). Barrel (2) contains a measurement point (14) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (13). Barrel (5) contains a measurement point (15) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (16) for a melt temperature sensor. Barrel (9) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (10) (round). The flange is followed by a valve (11) for throttling purposes. The internal diameter of valve (11) and line (10) amounts in each case to 15 mm, the valve length to 95 mm and the line length to 120 mm.

(38) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (15). The screw is then provided with 11 conveying elements according to the invention of a pitch of 30 mm and length of 30 mm.

(39) At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h of Bayblend® T45 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (17)) of the melt was measured at the end of the extruder in the flange (9) at various pressures (pressure measurement sensor (19)) upstream of the valve (11). The inlet temperature (measurement point (18)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8, 9), line (10, 12) and the valve (11) were heated to 240° C. The results are shown in Table 10 and reveal lower temperatures than in Table 9 in Example 9.

(40) TABLE-US-00010 TABLE 10 Pressure upstream of valve in bar 20.4 39.8 70.3 Inlet temperature (18) 275° C. 275° C. 275° C. Outlet temperature (17) 289° C. 292° C. 298° C. Outlet-inlet  14° C.  17° C.  23° C. temperature differential

Example 11

(41) The twin-screw extruder (FIG. 30) comprises a structure consisting of 9 barrel parts, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the first barrel (1) by way of a heated pipe (12). Barrel (2) contains a measurement point (14) for a melt temperature sensor. Barrel (3) is closed and barrel (4) contains a degassing opening (13). Barrel (5) contains a measurement point (15) for a melt temperature sensor. Barrels (6) and (7) are closed and barrel (8) contains a measurement point (16) for a melt temperature sensor. Barrel (9) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (10) (round). The flange is followed by a valve (11) for throttling purposes. The internal diameter of valve (11) and line (10) amounts in each case to 15 mm, the valve length to 95 mm and the line length to 120 mm.

(42) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow two double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). The screw is then provided with 5 double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm. A bush then follows with a length of 35 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (15). The screw is then provided with 5 conveying elements according to the invention of a pitch of 30 mm and length of 30 mm. There then follow 6 conventional single-flighted conveying elements of pitch 30 mm and length 30 mm.

(43) At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h of Bayblend® T45 (manufacturer: Bayer MaterialScience AG), the temperature (measurement point (17)) of the melt was measured at the end of the extruder in the flange (9) at various pressures (pressure measurement sensor (19)) upstream of the valve (11). The inlet temperature (measurement point (18)) of the melt into the twin-screw extruder was also measured. The extruder barrels (1, 2, 3, 4, 5, 6, 7, 8, 9), line (10, 12) and the valve (11) were heated to 240° C. The results are shown in Table 11 and reveal higher temperatures than in Table 10 in Example 10.

(44) TABLE-US-00011 TABLE 11 Pressure upstream of valve in bar 20.1 40.1 70.6 Inlet temperature (18) 278° C. 278° C. 278° C. Outlet temperature (17) 296° C. 302° C. 303° C. Outlet-inlet  18° C.  24° C.  25° C. temperature differential

(45) In Examples 12 and 13, melting was performed on a ZSK 32Mc (Coperion Werner & Pfleiderer) with a mixture of Makrolon® 3108 (manufacturer: Bayer MaterialScience AG) and ODS® 2015 (manufacturer: Bayer MaterialScience AG). The Makrolon® 3108 was colored purple with 1% of colored Makrolex® 420. The experiments were carried out with the structure in FIG. 31. The ratio of Makrolon® 3108 and ODS® 2015 amounts to 25%:75% (%=mass %).

(46) The extruder has a length of 24 L/D. The extruder consists of a feed zone (9) provided with conveying elements, a melting zone (10) occupied with kneading blocks and a metering zone (11), the configuration of which was varied. The pellets were predried. The die (7) at the extruder outlet is a flat film die with a slot height of 1 mm and a width of 140 mm.

(47) The polymer film emerging from the die was photographed by a CCD camera and backlit with a light source. The camera has 1280×960 pixels and a resolution of 29 μm/pixel. An image of the polymer film was taken every second and a total of 180 images were taken per test.

(48) If the most highly viscous Makrolon® 3108 is not completely melted, dark purple blemishes in the polymer film are recorded by the camera. The edge of the polymer film is recognized by the camera and the area of the polymer film in the image calculated. The ratio of said area to the area of dark purple blemishes is calculated. This serves as a measure of a screw configuration's melting performance. The greater the proportion of unmelted pellets, the poorer is the screw make-up.

Comparative Example 12

(49) The twin-screw extruder (FIG. 31) has a structure of 6 barrels (1-6) in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 32Mc with a 32 mm barrel diameter from Coperion Werner & Pfleiderer. The pellets are fed (12) into the first barrel (1). The other barrels (2-6) are closed and at the end there is a flat film die (7).

(50) The two screws (not shown) are provided symmetrically with screw elements. In the feed zone (9) the screws are provided with double-flighted conveying elements with a pitch of 42 mm and 63.5 mm. The feed zone extends as far as the middle of barrel (4), then the melting zone (10) starts. The melting zone (10) extends as far as the end of the fifth barrel (5) and consists of triple-flighted kneading blocks and transition kneading blocks providing a transition from double- to triple-flighted or vice versa. Flow was restricted at the end of the melting zone by a ZME element and/or left-handed kneading blocks.

(51) The metering zone (11) or pressure build-up zone begins at the end of the fifth barrel. It consists of a double-flighted conveying element with length 28 mm and pitch 28 mm. There then follow two conveying elements with a length of 42 mm and a pitch of 42 mm. There then follows a screw tip with pitch 28 mm and length 42 mm.

(52) At a throughput of 130 kg/h and a rotational speed of the screws of 400 rpm, unmelted pellets occupy 4.53% of the polymer film area (see Table 12).

Example 13

(53) The structure is the same as in the reference example. Only the metering zone or pressure build-up zone was provided with screw elements according to the invention.

(54) The conveying zone (11) begins at the end of the fifth barrel. It now consists of five screw elements according to the invention of length 28 mm and pitch 28 mm.

(55) Exactly the same operating conditions were established as in the reference test. It was surprisingly found that the proportion of unmelted pellets drops to 1.89%. The screw elements according to the invention thus unambiguously exhibit an improvement during melting in comparison with the current prior art.

(56) TABLE-US-00012 TABLE 12 Throughput in Rotational speed Particle Screw make-up kg/h in rpm area in % Comparative Example 12 130 400 4.53 Example 13 130 400 1.89

(57) Examples 14 and 15 relating to compounding were carried out on a ZSK 32Mc (Coperion Werner & Pfleiderer). The experiments were carried out with the structure in FIG. 32. The composition consists of 40.17 mass % component A, 47.60 mass % component B, 8.90 mass % component C and 3.33 mass % component D

(58) Component A

(59) Linear polycarbonate based on bisphenol A with a relative solution viscosity of η.sub.rel=1.275 measured in CH.sub.2Cl.sub.2 as solvent at 25° C. and in a concentration of 0.5 g/100 ml.

(60) Component B

(61) ABS polymer produced by emulsion polymerization of 50 wt. %, relative to the ABS polymer, of a mixture of 27 wt. % acrylonitrile and 73 wt. % styrene in the presence of 50 wt. %, relative to the ABS polymer, of a particulate crosslinked polybutadiene rubber (average particle diameter d.sub.50=0.35 μm).

(62) Component C

(63) Styrene-acrylonitrile copolymer with a styrene-acrylonitrile weight ratio of 72:28 and an intrinsic viscosity of 0.55 dl/g (measurement in dimethylformamide at 20° C.).

(64) Component D

(65) Component D consists of additives such as mold release agent and heat stabilizer.

(66) The extruder has a length of 40 L/D and consists of a feed zone (14) provided with conveying elements, a melting zone (15) occupied with kneading blocks and a metering zone (16), the configuration of which was varied, upstream of a die (11). The pellets were predried. The die (11) at the outlet of the extruder is a four-hole die. Downstream of the die (11), the Bayblend was drawn through a water bath and pelletized.

(67) Samples of the pellets were taken at the established operating point. 50 pellets were analysed under a microscope. The cylindrical pellets were illuminated at the end face and observed under the microscope from the opposite side. Depending on the screw make-up and operating point, unmelted polycarbonate zones, through which light shines, may be visible in the otherwise opaque pellet. These zones are known as windows. The number of windows relative to the sample of 50 pellets is a measure of melting. Ideally, there are no windows.

Comparative Example 14

(68) The twin-screw extruder (FIG. 32) comprises a structure consisting of 11 barrels, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 32Mc with a 32 mm barrel diameter from Coperion Werner & Pfleiderer. The pellets are fed (12) into the first barrel (1). The other barrels (2, 3, 4, 5, 6, 7, 8, 10) are closed with the exception of barrel (9), where there is a degassing opening (13). A four-hole die (11) is mounted at the end.

(69) The two screws (not shown) are provided symmetrically with screw elements. At the start in the feed zone (14) the screws are provided with double-flighted conveying elements. The feed zone (14) extends as far as the start of the barrel (7), then the melting zone (15) starts. The melting zone (15) extends as far as the middle of the barrel (8) and consists of triple-flighted kneading blocks and transition kneading blocks providing a transition from double- to triple-flighted or vice versa. Flow was restricted at the end of the melting zone by ZME element and/or left-handed kneading blocks.

(70) The metering zone (16) or pressure build-up zone starts in the middle of the barrel (9) after the melting zone. It consists of a double-flighted conveying element with length 28 mm and pitch 28 mm. There then follow two ZME elements with a length of 13 mm and a pitch of 13.5 mm. There then follow three double-flighted conveying elements with pitch 42 mm and length 42 mm. Then there are three double-flighted conveying elements with pitch 28 mm and length 28 mm, followed by conveying elements with pitch 28 mm and length 14 mm. Finally, there is the screw tip with a length of 42 mm and a pitch of 28 mm.

(71) At a throughput of 145 kg/h and a rotational speed of 600 rpm of the screws, 100 windows were visible in 50 pellets (see Table 13). At a throughput of 160 kg/h and a rotational speed of 600 rpm of the screws, 211 windows were visible in 50 pellets.

Example 15

(72) The twin-screw extruder (FIG. 32) comprises a structure consisting of 11 barrels, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 32Mc with a 32 mm barrel diameter from Coperion Werner & Pfleiderer. The pellets are fed (12) into the first barrel (1). The other barrels (2, 3, 4, 5, 6, 7, 8, 10) are closed with the exception of barrel (9), where there is a degassing opening (13). A four-hole die (11) is mounted at the end.

(73) The two screws (not shown) are provided symmetrically with screw elements. At the start in the feed zone (14) the screws are provided with double-flighted conveying elements. The feed zone (14) extends as far as the start of the barrel (7), then the melting zone (15) starts. The melting zone (15) extends as far as the middle of the barrel (8) and consists of triple-flighted kneading blocks and transition kneading blocks providing a transition from double- to triple-flighted or vice versa. Flow was restricted at the end of the melting zone by ZME element and/or left-handed kneading blocks.

(74) The metering zone (16) or pressure build-up zone starts in the middle of the barrel (8) after the melting zone. It consists of a screw element according to the invention of length 28 mm and pitch 28 mm. There then follow two ZME elements with a length of 13 mm and a pitch of 13.5 mm. There then follow 10 screw elements according to the invention with pitch 28 mm and length 28 mm.

(75) Exactly the same operating conditions were established as in the reference test. It was surprisingly found that the number of windows can be distinctly reduced with the novel screw elements (see Table 13). The screw elements according to the invention thus unambiguously exhibit an improvement during melting of Bayblend® T45 in comparison with the current prior art.

(76) TABLE-US-00013 TABLE 13 Throughput in Rotational speed Number of Screw make-up kg/h in rpm windows Comparative Example 14 160 600 211 Example 15 160 600 58 Comparative Example 14 145 600 100 Example 15 145 600 18

(77) Examples 16-19 relating to polymer conveying were carried out on a ZSK 40Sc (Coperion Werner & Pfleiderer). The experiments were carried out with the structure in FIG. 33.

(78) The twin-screw extruder (FIG. 33) comprises a structure consisting of seven barrels (1-7), in which are arranged co-rotating, intermeshing screws. The machine has a barrel diameter of 40 mm. The polymer melt is fed into the second barrel (2) by way of a heated pipe (9). Barrel (3) is closed and barrel (4) contains a measurement point (14) for a melt temperature sensor. Barrel (5) contains a degassing opening (10). Barrels (6) and (7) are closed. Barrel (8) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (13) (round). The flange is followed by a valve (12) for throttling purposes. The internal diameter of valve and line amounts to 15 mm for a valve length of 95 mm and a line length of 120 mm. Upstream of the valve (12), the pressure is measured by means of the sensor (11). The outlet temperature of the melt is measured with a manual thermometer which is held in the opening of the valve (12).

Comparative Example 16

(79) The twin-screw extruder (FIG. 33) comprises a structure consisting of seven barrels, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the second barrel (2) by way of a heated pipe (9). Barrel (3) is closed and barrel (4) contains a measurement point (14) for a melt temperature sensor. Barrel (5) contains a degassing opening (10). Barrels (6) and (7) are closed. Barrel (8) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (13) (round). The flange is followed by a valve (12) for throttling purposes. The internal diameter of valve and line amounts to 15 mm for a valve length of 95 mm and a line length of 120 mm.

(80) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with three double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow five double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). Downstream of the bush is located a ZME element with a length of 20 mm and a pitch of 10 mm. The screw is then provided with two double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm.

(81) The screw is then provided with eight double-flighted conveying elements with a pitch of 40 mm and length of 40 mm.

(82) At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h, the increase in temperature was measured at various pressures (pressure measurement sensor (11)) upstream of the valve (12). The following materials were handled: Polypropylen®, Polystyrol®, Pocan®. The temperature (measurement point 14) of the melt in the twin-screw extruder was measured. The temperature was additionally measured with a manual thermometer (15) at the outlet of the tube. The thermometer was held in the melt in the tube. Table 14 shows the increase in temperature from (14) to (15).

(83) TABLE-US-00014 TABLE 14 Increase in temperature in K Pressure upstream of valve in bar Material 20 35 50 65 BASF Polystyrol ® 454C 2 Kg 20 24 26 30 Basell, Polypropylen Metocene ® 18 21 25 29 HM 562S BASF, Polystyrol ® 158K 17 21 26 31 Lanxess, Pocan ® B 1600 13 18 21 22

Example 17

(84) The twin-screw extruder (FIG. 33) comprises a structure consisting of seven barrels, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the second barrel (2) by way of a heated pipe (9). Barrel (3) is closed and barrel (4) contains a measurement point (14) for a melt temperature sensor. Barrel (5) contains a degassing opening (10). Barrels (6) and (7) are closed. Barrel (8) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (13) (round). The flange is followed by a valve (12) for throttling purposes. The internal diameter of valve and line amounts to 15 mm for a valve length of 95 mm and a line length of 120 mm.

(85) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with three double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow five double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). Downstream of the bush is located a ZME element with a length of 20 mm and a pitch of 10 mm. The screw is then provided with two double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm.

(86) The screw is then provided with 11 screw elements according to the invention with a pitch of 30 mm and length of 30 mm.

(87) At a rotational speed of the screws of 250 rpm and a throughput of 80 kg/h, the increase in temperature was measured at various pressures (pressure measurement sensor (11)) upstream of the valve (12). The following materials were handled: Polypropylen®, Polystyrol®, Pocan®. The temperature (measurement point 14) of the melt in the twin-screw extruder was measured. The temperature was additionally measured with a manual thermometer (15) at the outlet of the tube. The thermometer was held in the melt in the tube. Table 15 shows the increase in temperature from (14) to (15). The novel development exhibits a lower increase in temperature for all products.

(88) TABLE-US-00015 TABLE 15 Increase in temperature in K Pressure upstream of valve in bar Material 20 35 50 65 BASF, Polystyrol ® 454C 2 Kg 18 21 25 26 Basell, Polypropylen Metocene ® 18 21 24 28 HM 562S BASF, Polystyrol ® 158K 16 20 22 25 Lanxess, Pocan ® B 1600 — 16 19 19

Comparative Example 18

(89) The twin-screw extruder (FIG. 33) comprises a structure consisting of seven barrels, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the second barrel (2) by way of a heated pipe (9). Barrel (3) is closed and barrel (4) contains a measurement point (14) for a melt temperature sensor. Barrel (5) contains a degassing opening (10). Barrels (6) and (7) are closed. Barrel (8) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (13) (round). The flange is followed by a valve (12) for throttling purposes. The internal diameter of valve and line amounts to 15 mm for a valve length of 95 mm and a line length of 120 mm.

(90) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with three double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow five double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (14). Downstream of the bush is located a ZME element with a length of 20 mm and a pitch of 10 mm. The screw is then provided with two double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm.

(91) The screw is then provided with eight double-flighted conveying elements with a pitch of 40 mm and length of 40 mm.

(92) At various rotational speeds of the screws between 150 and 350 rpm and a throughput of 80 kg/h, the increase in temperature was measured with the valve (12) open. The following materials were handled: Ineos Lustran® DN 50, Polypropylen®, Polystyrol®. The temperature (measurement point 14) of the melt in the twin-screw extruder was measured. The temperature was additionally measured with a manual thermometer (15) at the outlet of the tube. The thermometer was held in the melt in the tube. Table 16 shows the increase in temperature from (14) to (15).

(93) TABLE-US-00016 TABLE 16 Increase in temperature in K Rotational speed of screws in rpm Material 350 300 250 200 150 Ineos Lustran ® DN 50 18 18 15 12 11 Basell, Polypropylen Metocene ® 17 — — — — HM 562S BASF, Polystyrol ® 158K — 19 16 — —

Example 19

(94) The twin-screw extruder (FIG. 33) comprises a structure consisting of seven barrels, in which are arranged co-rotating, intermeshing screws. The machine is a ZSK 40Sc with a 40 mm barrel diameter from Coperion Werner & Pfleiderer. The polymer melt is fed into the second barrel (2) by way of a heated pipe (9). Barrel (3) is closed and barrel (4) contains a measurement point (14) for a melt temperature sensor. Barrel (5) contains a degassing opening (10). Barrels (6) and (7) are closed. Barrel (8) is a flange, which converts the cross-section from the figure-of-eight-shaped bore of the twin-screw extruder to a pipe (13) (round). The flange is followed by a valve (12) for throttling purposes. The internal diameter of valve and line amounts to 15 mm for a valve length of 95 mm and a line length of 120 mm.

(95) The two screws (not shown) are provided symmetrically with screw elements. At the start the screws are provided in each case with three double-flighted conveying elements with a pitch of 25 mm and a length of 25 mm. There then follow five double-flighted conveying elements with the pitch 60 mm and length 60 mm. A bush then follows with a length of 30 mm and a diameter of 26 mm, which in the installed state is arranged under the melt temperature sensor (13). Downstream of the bush is located a ZME element with a length of 20 mm and a pitch of 10 mm. The screw is then provided with two double-flighted conveying elements with the pitch 60 mm and length 60 mm and one conveying element with the pitch 60 mm and length 30 mm.

(96) The screw is then provided with 11 screw elements according to the invention with a pitch of 28 mm and length of 28 mm.

(97) At various rotational speeds of the screws between 150 and 350 rpm and a throughput of 80 kg/h, the increase in temperature was measured with the valve (12) open. The following materials were handled: Ineos Lustran® DN 50, Polypropylen®, Polystyrol®. The temperature (measurement point 14) of the melt in the twin-screw extruder was measured. The temperature was additionally measured with a manual thermometer (15) at the outlet of the tube. The thermometer was held in the melt in the tube. Table 17 shows the increase in temperature from (14) to (15). The increase in temperature with the screw elements according to the invention is lower than with the prior art.

(98) TABLE-US-00017 TABLE 17 Increase in temperature in K Rotational speed of screws in rpm Material 350 300 250 200 150 Ineos Lustran ® DN 50 17 15 12 10 9 Basell, Polypropylen Metocene ® 16 — — — — HM 562S BASF, Polystyrol ® 158K — 18 15 — —