PROCESS FOR PRODUCING POLYPROPYLENE COMPOSITION

Abstract

The invention relates to a process for producing a polypropylene composition using a first extruder comprising successive zones comprising a first zone, a second zone, a third zone and a fourth zone and a second extruder comprising successive zones comprising a first zone and a second zone, the process comprising the steps of: 1a) introducing a first propylene-based polymer in the first zone of the first extruder, 1b) melt mixing the first propylene-based polymer in the second zone of the first extruder, 1c) adding an additive masterbatch to the mixture of step 1b) in the third zone of the first extruder and 1d) melt-mixing the mixture of step 1c) in the fourth zone of the first extruder to obtain the polypropylene composition, wherein the maximum temperature in the fourth zone of the first extruder is lower than the maximum temperature in the second zone of the first extruder and is lower than 240° C., wherein the additive masterbatch is produced in the second extruder by a process comprising the steps of: 2a) introducing a second propylene-based polymer and organic additives in the first zone of the second extruder and 2b) melt mixing the mixture of step 2a) in the second zone of the second extruder to obtain the additive masterbatch, wherein the maximum temperature in the second zone of the second extruder is lower than the maximum temperature in the second zone of the first extruder and is lower than 240° C.

Claims

1. A process for producing a polypropylene composition using a first extruder comprising successive zones comprising a first zone, a second zone, a third zone and a fourth zone and a second extruder comprising successive zones comprising a first zone and a second zone, the process comprising the steps of: 1a) introducing a first propylene-based polymer in the first zone of the first extruder, 1b) melt mixing the first propylene-based polymer in the second zone of the first extruder, 1c) adding an additive masterbatch to the mixture of step 1b) in the third zone of the first extruder and 1d) melt-mixing the mixture of step 1c) in the fourth zone of the first extruder to obtain the polypropylene composition, wherein the maximum temperature in the fourth zone of the first extruder is lower than the maximum temperature in the second zone of the first extruder and is lower than 240° C., wherein the additive masterbatch is produced in the second extruder by a process comprising the steps of: 2a) introducing a second propylene-based polymer and organic additives in the first zone of the second extruder and 2b) melt mixing the mixture of step 2a) in the second zone of the second extruder to obtain the additive masterbatch, wherein the maximum temperature in the second zone of the second extruder is lower than the maximum temperature in the second zone of the first extruder and is lower than 240° C.

2. The process according to claim 1, wherein maximum temperature in the second zone of the first extruder is 220 to 265° C., for example 240 to 265° C.

3. The process according to claim 1, wherein the melt mixing in step 2b) is performed at temperatures of 170 to 230° C.

4. The process according to claim 1, wherein the melt mixing in step 1d) is performed at temperatures of 180 to 235° C.

5. The process according to claim 1, wherein the amount of the organic additives introduced in step 2a) with respect to the polypropylene composition obtained after step 1d) is 5 to 50 wt %.

6. The process according to claim 1, wherein the weight ratio between the mixture of step 1b) and the additive masterbatch of step 2b) is 90:10 to 10:90.

7. The process according to claim 1, wherein the amount of the organic additives with respect to the additive masterbatch of step 2b) is 10 to 80 wt %.

8. The process according to claim 1, wherein the organic additives comprise an organic flame retardant.

9. The process according to claim 1, wherein degassing is performed in the second extruder.

10. The process according to claim 1, wherein the first propylene-based polymer and/or the second propylene-based polymer is a propylene homopolymer, a random propylene-α-olefin copolymer or a heterophasic propylene copolymer.

11. The process according to claim 1, wherein the first propylene-based polymer and the second propylene-based polymer are of the same type.

12. The polypropylene composition obtained by the process according to claim 1.

13. A process for the production of sheathed continuous multifilament strands, comprising the steps of: i) unwinding continuous glass multifilament strands from a package, ii) applying an impregnating agent to the continuous glass multifilament strands to form the impregnated continuous multifilament strands and iii) applying a sheath of the polypropylene composition according to claim 12 around the impregnated continuous multifilament strands to form the sheathed continuous multifilament strands, preferably wherein the melt of the polypropylene composition obtained by step d) is directly used for step iii) without solidification.

14. The sheathed continuous multifilament strands obtained by the process according to claim 13.

15. A moulded article comprising the polypropylene composition according to claim 12.

16. The moulded article of claim 15, wherein the article is an automotive exterior part or an automotive interior part.

Description

EXPERIMENTS

Example 1

[0134] A main extruder comprising successive zones of a first zone, a second zone, a third zone and a fourth zone was used. The second zone of the main extruder comprises kneading blocks. A side extruder comprising successive zones of a first zone and a second zone is coupled to the third zone of the main extruder. The second zone of the side extruder was equipped with a degassing means.

[0135] The composition of table 1 was fed to the first zone of the side extruder. The composition was melt-mixed in the second zone of the side extruder. The resulting masterbatch was fed to the third zone of the main extruder. The maximum temperature of the melt in the second zone of the side extruder was 200° C. The throughput of the side extruder was 800 kg/h.

[0136] The composition of table 2 (except for the masterbatch from the side extruder) was fed to the first zone of the main extruder at 350 kg/h. The composition was melt-mixed in the second zone of the main extruder. The maximum temperature in the second zone of the main extruder reached 230 to 240° C. The third zone of the main extruder receives the melt of the masterbatch from the side extruder and the melt from the second zone of the main extruder. The mixture was melt-mixed in the fourth zone of the main extruder and was extruded. The temperature of the melt was 210 to 215° C. at the beginning of the fourth zone of the main extruder and reached 235° C. at the end. The throughput of the main extruder was 1150 kg/h.

[0137] Since the flame retardant was never subjected to a temperature above 240° C., a composition comprising a high amount of non-degraded flame retardant was successfully obtained at a high throughput.

TABLE-US-00001 TABLE 1 (in wt %): Side extruder PP block copolymer with MFI of 70 dg/min (230° C., 2.16 kg) 49.75 (commercial name: SABIC ® PP 513MNK10) flame retardant consisting of 64.8 wt % Piperazine pyrophosphate, 49.75 30.5 wt % Melamine phosphate, 4.7 wt % ZnO calcium stearate 0.5

TABLE-US-00002 TABLE 2 (in wt %): Main extruder Masterbatch from side extruder 68.82 PP block copolymer with MFI of 70 dg/min (230° C., 2.16 kg) 28.51 (commercial name: SABIC ® PP 513MNK10) PP block copolymer with MFI of 15 dg/min (230° C., 2.16 kg)  0.18 (commercial name: SABIC ® PP PHC31 MG), milled to be used as carrier for additives stabilizers  2.08 color masterbatch  0.41

Comparative Experiments

[0138] The same main extruder was used to prepare a polypropylene composition, but without the side extruder. At the same throughput as in example 1, the temperature of the melt reached 265° C. at the outlet of the main extruder. At such temperature the flame retardant is completely degraded.

[0139] In order to maintain the temperature of the melt in the main extruder below 240° C., the throughput of the main extruder had to be decreased to 30 to 50%.