Long-chain branched polypropylene for foam application

1. A process for producing a long-chain branched propylene homopolymer or copolymer (b-PP), wherein the long-chain branched propylene homopolymer or copolymer (b-PP) has:

a) a comonomer in the copolymer selected from ethylene, C 4 -C 20 -alpha olefin and any combination thereof and a comonomer content in a range of 0.1 to 7.0 wt %,

b) a melt flow rate MFR 2 (230° C.) in a range of 1.5 to 6.0 g/10 min as measured according to ISO 1133,

c) a F30 melt strength in a range of 18.0 to 50.0 cN as measured according to ISO 16790:2005,

d) a xylene hot insoluble (XHU) fraction of less than 2.5 wt % as measured according to EN 579, and

e) wherein the long-chain branched propylene homopolymer or copolymer (b-PP) is free of phthalic compound,

wherein the process comprises:

producing a propylene homopolymer or copolymer powder in a polymerization process in the presence of a catalyst system comprising:

a) a Ziegler-Natta based catalyst with a transition metal of Group 4 to 6 (TM), the catalyst containing an internal donor, wherein the internal donor is a non-phthalic compound,

b) optionally a co-catalyst (Co),

c) optionally an external donor (ED) and wherein if present, the co-catalyst (Co) to external donor (ED) molar ratio [Co/ED] is in a range of 3.0 to 45.0 mol/mol and wherein the cocatalyst (Co) to transition metal of Group 4 to 6 (TM) molar ratio [Co/TM] is in a range of 40.0 to 500 mol/mol; wherein the propylene homopolymer or copolymer has a comonomer in the copolymer selected from ethylene, C 4 -C 20 -alpha olefin and any combination thereof, with a comonomer content in a range of 0.1 to 7.0 wt %, a xylene cold soluble (XCS) fraction in a range of 0.8 to 15.0 wt %, and an MFR 2 in a range of 0.1 to 1.5 g/10 min as measured according to ISO 1133; wherein the propylene homopolymer or copolymer powder has:

a) a porosity of more than 8.0%,

b) a median particle size d50 measured by sieve analysis according to ISO 3310 and evaluated according to ISO 9276-6 in a range of 150 to 1500 μm,

c) a top cut particle size d95 measured by sieve analysis according to ISO 3310 and evaluated according to ISO 9276-6 in a range of 500 to 4000 μm,

said propylene homopolymer or copolymer is free of phthalic compound; and

subjecting said propylene homopolymer or copolymer to a reactive modification to obtain said long-chain branched propylene homopolymer or copolymer (b-PP).

2. The process according to claim 1 , wherein the long-chain branched propylene homopolymer or copolymer (b-PP), has a v30 melt extensibility of equal to or more than 200 mm/s as measured according to ISO 16790:2005.

3. The process according to claim 1 , wherein the non-phthalic compound is selected from (di)esters of non-phthalic carboxylic (di)acids wherein the (di)ester belongs to the group comprising malonates, maleates, succinates, citraconates, glutarates, cyclohexene-1,2-dicarboxylates and benzoates or derivatives or mixtures thereof.

4. The process according to claim 1 , wherein the reactive modification for producing the long-chain branched propylene homopolymer or copolymer (b-PP) comprises the steps:

mixing the propylene homopolymer or copolymer with a thermally decomposing free radical-forming agent and optionally with at least one functionally unsaturated compound at a temperature of 20 to 100° C. for at least 2 minutes to form a pre-mixed material and melt mixing the pre-mixed material in a meltmixing device at a barrel temperature in a range of 180 to 300° C.

5. The process according to claim 1 , further comprising the step:

mixing the long-chain branched propylene homopolymer or copolymer (b-PP) with at least one or more compounds chosen from:

(a) additives,

(b) polymers,

(c) fillers,

(d) reinforcement agents, or

any combination of (a), (b), (c), and (d),

and producing a long-chain branched polypropylene composition (b-PP-c).

6. The process according to claim 5 , wherein the long-chain branched polypropylene composition (b-PP-c) has:

(a) a melt flow rate MFR 2 (230° C.) in a range of 1.5 to 6.0 g/10 min as measured according to ISO 1133,

(b) an F30 melt strength in a range of 18.0 to 50.0 cN, as measured according to ISO 16790:2005,

(c) a xylene hot insoluble (XHU) of less than 2.5 wt % as measured according to EN 579, and

(d) wherein the long-chain branched polypropylene composition (b-PP-c) is free of phthalic compound.