Propylene polymer with improved processability in thermoforming

Patent metadata

Field	Value
Publication number	US-9701769-B2
Application number	US-201514858846-A
Country	US
Kind code	B2
Filing date	Sep 18, 2015
Priority date	Oct 1, 2009
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

Propylene polymer including at least two propylene polymer fractions of different melt flow index and a minor amount of at least one comonomer may be characterized by specific ranges for melt flow index, xylene solubles content and recovery compliance. The propylene polymer may be particularly suited for thermoforming.

First claim

The invention claimed is:

1. A process comprising:
thermoforming a propylene polymer wherein the propylene polymer comprises at least one comonomer and at least two propylene polymer fractions of different melt flow index, said propylene polymer being characterized by:
a melt flow index ranging from 0.5 dg/min to 8.0 dg/min, determined according to ISO 1133, condition L at 230° C. and 2.16 kg;
a xylene solubles content ranging from 1.0 wt % to 4.0 wt %, relative to a total weight of the propylene polymer;
a total comonomer content of from 0.1 wt % to 1.0 wt %, relative to the total weight of the propylene polymer;

wherein the propylene polymer fraction with the lowest melt flow index has a melt flow index ranging from 0.2 dg/min to 1.0 dg/min, determined according to ISO 1133, condition L at 230° C. and 2.16 kg,
wherein each of the at least two propylene polymer fractions has substantially the same comonomer content and, relative to the comonomer content of the propylene polymer fraction with the lowest melt flow index, the comonomer content of the other propylene polymer fraction is from 70% to 130%, under the provision that each of the at least two propylene polymer fractions comprises comonomer;
and wherein the process is characterized in that a thermoforming window of the process is broadened by at least 0.5° C. as compared to thermoforming a propylene homopolymer with a single propylene homopolymer fraction and thermoformed under the same conditions.

2. The process of claim 1 , wherein the thermoforming the propylene polymer comprises melt-extruding the propylene polymer to produce a sheet, and shaping the sheet.

3. The process of claim 2 , wherein melt-extruding the propylene polymer to produce the sheet comprises:
feeding the propylene polymer to an extruder;
melting the propylene polymer in the extruder;
extruding the molten propylene polymer through a slit die to form the sheet; and
cooling the sheet.

4. The process of claim 3 , wherein the propylene polymer is melted at a temperature ranging from 200 to 280° C.

5. The process of claim 2 , wherein shaping the sheet comprises:
warming the sheet;
draping the sheet over or into a mold to obtain a formed sheet;
cooling the formed sheet; and
removing the formed sheet from the mold.

6. The process of claim 1 , wherein the process is characterized in that the thermoforming window of the process is broadened by at least 0.6° C. as compared to thermoforming a propylene homopolymer with a single propylene homopolymer fraction.

7. The process of claim 1 , wherein the melt flow index ranges from 1.0 dg/min to 5.0 dg/min, determined according to ISO 1133, condition L, at 230° C. and 2.16 kg.

8. The process of claim 1 , wherein the total comonomer content ranges from 0.2 wt % to 0.8 wt %, relative to the total weight of the propylene polymer.

9. The process of claim 1 , wherein the xylene solubles content ranges from 1.3 wt % to 3.5 wt %, relative to the total weight of the propylene polymer.

10. The process of claim 1 , wherein the fraction with the lowest melt flow index has a melt flow index ranging from 0.3 dg/min to 0.9 dg/min, determined according to ISO 1133, condition L, at 230° C. and 2.16 kg.

11. The process of claim 1 , wherein the propylene polymer comprises from 50 wt % to 70 wt %, relative to the total weight of the propylene polymer, of the propylene polymer fraction with the lowest melt flow index.

12. The process of claim 1 , wherein each of the at least two propylene polymer fractions has the same comonomer content.

13. The process of claim 1 , wherein at least 60 mol % of the total amount of comonomer is present as single comonomer units.

Assignees

• Total Res & Technology Feluy

Inventors

• Forgue Thomas
• Gromada Jerome
• Standaert Alain
• De Luca Rita

Classifications

• C08F2410/04

  Dual catalyst, i.e. use of two different catalysts, where none of the catalysts is a metallocene · CPC title

• B29C51/002

  characterised by the choice of material · CPC title

• C08L23/16

  Ethylene-propylene or ethylene-propylene-diene copolymers · CPC title

• C08F110/06

  Propene · CPC title

• C08L23/14

  Copolymers of propene (C08L23/16 takes precedence) · CPC title