Polypropylene composition for HMS PP foam sheet with balanced bending resistance
The present invention relates to a polypropylene composition comprising —10 to 50 wt. % of recycled polypropylene (R-PP) and/or linear polypropylene (L-PP); —40 to 89.95 wt. % of a high melt strength polypropylene (HMS-PP) having an F30 melt strength of more than 25.0 cN and a v30 melt extensibility of more than 205 mm/s, wherein the F30 melt strength and the v30 melt extensibility are determined according to ISO 16790:2005; and —0.05 to 10 wt. % of a nucleating agent (NA); a foamed sheet formed from the polypropylene composition; an article comprising the foamed sheet and a process comprising the step of forming the polypropylene composition. Furthermore, the invention is further directed to the usage of the polypropylene composition for the formation of foamed sheets.
1 . A polypropylene composition comprising:
20.0 to 30.0 wt. % of recycled polypropylene (R-PP);
69.0 to 79.9 wt. % of a high melt strength polypropylene (HMS-PP) having an F 30 melt strength of 25.0 cN to 40.0 cN and a v 30 melt extensibility of 225 to 260 mm/s, wherein the F 30 melt strength and the v 30 melt extensibility are determined according to ISO 16790:2005; and
0.05 to 6.0 wt. % of a nucleating agent (NA);
wherein the recycled polypropylene (R-PP) has an F 30 melt strength of 1.0 to 20.0 cN, determined according to ISO 16790:2005, and a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in a range of 5 to 15 g/10 min; and
wherein the nucleating agent (NA) is talc.
2 . The polypropylene composition according to claim 1 , wherein the recycled polypropylene (R-PP) is a recycled polypropylene (Rec-PP) comprising at least 50 wt. % of recycled high melt strength polypropylene (HMS-PP).
3 . A foamed sheet formed from the polypropylene composition according to claim 1 .
4 . The foamed sheet according to claim 3 , having a thickness of 0.5 to 10 mm and/or a density of 150 to 250 kg/m 3 .
5 . The foamed sheet according to claim 3 , wherein the foamed sheet is covered by a cover layer (CL).
6 . The foamed sheet according to claim 5 , wherein the foamed sheet and the cover layer (CL) are directly adjacent.
7 . An article comprising the foamed sheet according to claim 3 .
8 . A process comprising the following step
a) producing a polypropylene composition comprising
20.0 to 30.0 wt. % of recycled polypropylene (R-PP);
69.0 to 79.9 wt. % of a high melt strength polypropylene (HMS-PP) having an F 30 melt strength of 25.0 cN to 40.0 cN and a v 30 melt extensibility of 225 to 260 mm/s, wherein the F 30 melt strength and the v 30 melt extensibility are determined according to ISO 16790:2005; and
0.05 to 6.0 wt. % of a nucleating agent (NA),
wherein the recycled polypropylene (R-PP) has an F 30 melt strength of 1.0 to 20.0 cN, determined according to ISO 16790:2005, and a melt flow rate MFR 2 (230° C.) measured according to ISO 1133 in a range of 5 to 15 g/10 min; and
wherein the nucleating agent (NA) is talc;
whereby the recycled polypropylene (R-PP), the high melt strength polypropylene (HMS-PP) and the nucleating agent (NA) are simultaneously or consecutively combined and mixed in a mixing device.
9 . The process according to claim 8 , wherein the process further comprises the following step b) subsequent to step a)
b) forming a foamed article comprising the step of foaming the polypropylene composition obtained in step a).
10 . The process according to claim 9 , wherein the process further comprises the following step c) subsequent to step b)
c) forming a cup from the foamed article obtained after step b).
11 . The process according to claim 9 , wherein the recycled polypropylene (R-PP) is a recycled polypropylene (Rec-PP) and the process further comprises the following step d) subsequent to step b):
d) forming the recycled polypropylene (Rec-PP) using polymer remains present after step b).
12 . A method comprising producing foamed sheets from the polypropylene composition according to claim 1 , the foamed sheets fulfilling the following relationship (I):
bending resistance (MD)/bending resistance (CD)≤1.2 (I)
wherein
bending resistance (MD) is the bending resistance in machine direction measured according to SCAN P29:95, in mN; and
bending resistance (CD) is the bending resistance in cross direction measured according to SCAN P29:95, in mN.
13 . A method comprising producing foamed sheets from the polypropylene composition according to claim 1 , the foamed sheets fulfilling the following relationship (II)
thermal conductivity at 100° C./thermal conductivity at 20° C. 1.5 (II)
wherein
thermal conductivity at 100° C. is the thermal conductivity of the foamed sheet at 100° C. determined according to ISO 1856:2000 in m·K; and
thermal conductivity at 20° C. is the thermal conductivity of the foamed sheet at 20° C. determined according to ISO 1856:2000 in m·K.