PROCESS FOR THE PREPARATION OF A HETEROPHASIC PROPYLENE COPOLYMER

Abstract

The invention is directed to a process for the preparation of a heterophasic propylene copolymer comprising mixing 55-95 wt % of a propylene polymer and 5-45 wt % of an ethylene-propylene rubber with 0.01 −1 wt % of an organic peroxide with a decomposition half-life time of 6 minutes at a temperature between 80 and 109° C. and 0.001 −1.5 wt % of a co-agent, wherein all weight percentages are based on the total weight of the polymer composition, wherein the mixing is performed at a temperature which is below the temperature where the organic peroxide has a decomposition half-life time of 6 minutes to obtain a mixed polymer composition, and subsequently melt-mixing the mixed polymer composition. The invention also relates to A heterophasic propylene copolymer having a. Overall ethylene content between 5-20 wt % measured with FTIR b. MFI between 3 and 25 (g/10 min) measured according to ISO 1133-1:2011 at 230° C. and 2.16 kg c. 20° C. xylene soluble fraction (CXS) between 8 and 30 (wt %) d. a BTT according to the formula: BTT≦65-10* (CXS/MFI) wherein the wt % is defined relative to the total of the composition.

Claims

1. Process for the preparation of a heterophasic propylene copolymer comprising mixing a polymer composition comprising 55-95 wt % of a propylene polymer and 5-45 wt % of an ethylene-propylene rubber with 0.01-1 wt % of an organic peroxide with a decomposition half-life time of 6 minutes at a temperature between 80 and 109° C. and 0.001-1.5 wt % of a co-agent, wherein all weight percentages are based on the total weight of the polymer composition, wherein the mixing is performed at a temperature which is below the temperature where the organic peroxide has a decomposition half-life time of 6 minutes to obtain a mixed polymer composition, and subsequently melt-mixing the mixed polymer composition to prepare the heterophasic propylene copolymer.

2. Process according to claim 1, wherein the organic peroxide has a decomposition half-life time of 6 minutes at a temperature between 82 and 105° C.

3. Process according to claim 1, wherein the organic peroxide is chosen from the group consisting of tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate,1,1,3,3-tetramethylbutyl peroxypivalate, tert-butyl peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate and tert-amyl peroxy-2-ethylhexanoate.

4. Process according to claim 1, wherein the organic peroxide has a structure according to formula I
R1—(C═O)—O—O—(C═O)—R2   (I) wherein R1 and R2 are the same or different and are chosen from alkyl, aryl or aralkyl groups, having between 2 and 30 carbon atoms.

5. Process according to claim 1, wherein the peroxide is chosen from the group consisting of di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide and didecanoyl peroxide.

6. Process according to claim 1, wherein the co-agent is chosen from the group consisting of divinyl compounds, allyl compounds, compounds with two (meth)acrylate groups, dienes and mixtures of these unsaturated monomers.

7. Process according to claim 1, wherein the co-agent is ortho- or para-divinylbenzene.

8. Process according to claim 1, wherein the process is performed in an extruder comprising a mixing zone having a temperature below the temperature where the organic peroxide has a decomposition half-life time of 6 minutes for mixing the propylene polymer, the ethylene-propylene rubber, the organic peroxide and the co-agent, and a subsequent reaction zone having a temperature above the melting temperature of the propylene polymer for melt-mixing the mixed polymer composition.

9. Process according to claim 1, wherein the temperature in the mixing zone is between 20 and 104° C.

10. Process according to claim 1, wherein the propylene polymer can be chosen from a propylene homopolymer and/or a propylene copolymer comprising at least 90 wt % of propylene and up to 10 wt % ethylene and/or at least one C.sub.4 to C.sub.10 alpha-olefin.

11. Process according to claim 1, wherein the propylene polymer is a propylene homopolymer.

12. A heterophasic propylene copolymer having a. Overall ethylene content between 5-20 wt % measured with FTIR b. MFI between 3 and 25 (g/10 min) measured according to ISO 1133-1:2011 at 230° C. and 2.16 kg c. 20° C. xylene soluble fraction (CXS) between 8 and 30 (wt %) d. a BTT according to the formula: BTT≦65-10* (CXS/MFT) wherein the wt % is defined relative to the total of the composition.

13. The copolymer according to claim 12, wherein the copolymer gas a gelcontent below 4 wt %.

14. An article comprising the heterophasic propylene copolymer according to claim 1, wherein the article is selected from garden furniture, household items, battery casings, automobile parts, containers, toys, crates and boxes.

15. (canceled)

16. A process for treating a heterophasic propylene polymer composition comprising: first mixing dilauroyl peroxide, a coagent, and the heterophasic propylene polymer composition at a temperature below the temperature where the dilauroyl peroxide has a decomposition half-life time of 6 minutes to obtain a mixed polymer composition, and melt mixing the mixed polymer composition; wherein the heterophasic propylene polymer composition comprises 55-95 wt % of a propylene polymer and 5-45 wt % of an ethylene-propylene rubber; and wherein the coagent is selected from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethylbutadiene and ortho- or para-divinylbenzene.

17. Process according to claim 1, wherein the peroxide is dilauroyl peroxide.

Description

EXAMPLES

[0065] Materials

[0066] The polymer compositions were all Sabic products: blends of homopolymer of propylene with an ethylene propylene copolymer ‘rubber’.

[0067] More detailed information regarding the composition of the polymer compositions can be found in table 1.

TABLE-US-00001 TABLE 1 Propylene copolymers powder mixtures P1 P2 P3 MFI [g/10 min] 1.9 5.3 14.4 CXS [wt %] 18 12 12 overall C2 content [wt %] 14 9 9 BTT [° C.] −4 40 60

Peroxides:

[0068] Laurox® S , dilauroyl peroxide; decomposition half-life time=6 min at a temperature of 99° C. (T(° C.) for t ½ of 0.1 h). [0069] Trigonox® BPIC-C75, t-butylperoxy isopropyl carbonate; decomposition half-life time=6 min at a temperature of 137° C. [0070] Luperox® 802PP40, di(t-butylperoxyisopropyl)benzene; decomposition half-life time=6 min at a temperature of 156° C. [0071] Perkadox 14, Di(tert-butylperoxyisopropyl)benzene, T(° C.) for t ½ of 0.1 h is 156° C. [0072] Trigonox 25, tert butyl peroxy pivalate, T(° C.) for t ½ of 0.1 h is 94° C. [0073] Co-Agent Divinylbenzene (DVB) [0074] Additives: Calcium stearate; Irganox® 8225

Preparation of the Samples

[0075] The samples for the experiments were prepared with a standard additive package of 0.1 wt. % calcium stearate and 0.2 wt. % Irganox 8225. Various ratios peroxide/co-agent were added to each sample. The additives and heterophasic propylene copolymer powders were pre-mixed and the peroxides and the co-agents were dosed per batch, and homogenized by hand just before the extrusion on a ZSK 25 extruder. All experiments have been performed with the same screw, temperature settings (temperature in the mixing zone was 40° C. and temperature in the melt-mixing zone was 240° C.), a screw speed of 200 rpm and a throughput of 8 kg/hour. In table 2 all the samples which were produced are described.

[0076] Test Methods

[0077] The MFI value was determined according to ISO 1133-1:2011 at 230° C. and 2.16 kg.

[0078] The Izod impact was determined according to ISO 180/4A at 23° C. and 3.2 mm or to determine the brittle to tough transition temperature (BTT) at various higher temperatures. The Izod impact was determined parallel (II).

[0079] All compounds analyzed were separated in a CXS (<25° C.) fraction, a CXUS (25° C.-130° C). fraction (respectively called the 25C and the 130C fraction), and a gel fraction (non-soluble in hot xylene). The difference between a recovery of 100 wt. % and the observed recovery was taken as an indicative number for gel content.

[0080] Table 2 also shows the test results for all samples.

TABLE-US-00002 TABLE 2 Test Results Exper- Peroxide DVB MFI Impact iment Powder Type wt % wt % g/10 min kJ/m.sup.2 CE1 P1 — — 1.9 77 CE2 P1 Laurox S 0.62 — 2.3 77 E1 P1 Laurox S 0.62 0.22 0.6 83 E2 P1 Laurox S 0.62 0.44 1 86 CE3 P1 Trig.BPIC 0.36 — 6.4 56 CE4 P1 Trig.BPIC 0.36 0.22 0.9 57 CE5 P1 Trig.BPIC 0.36 0.44 0.1 20 CE6 P1 Luperox 0.36 — 150 6 802PP40 CE7 P1 Luperox 0.36 0.22 35 20 802PP40 CE8 P1 Luperox 0.36 0.44 12 22 802PP40 CE11 P2 — — — 5.3 16 CE12 P2 Laurox S 0.62 — 6.8 13 E11 P2 Laurox S 0.62 0.22 4.6 19 E12 P2 Laurox S 0.62 0.44 4.8 36 CE13 P2 Trig.BPIC 0.36 — 31 10 CE14 P2 Trig.BPIC 0.36 0.22 4.8 17 CE15 P2 Trig.BPIC 0.36 0.44 1 22 CE16 P2 Luperox 0.36 — >150 2.4 802PP40 CE17 P2 Luperox 0.36 0.22 89 10 802PP40 CE18 P2 Luperox 0.36 0.44 24 11 802PP40 CE21 P3 — — — 14.4 8 CE22 P3 Laurox S 0.62 — 17 8 E21 P3 Laurox S 0.62 0.22 15 10 E22 P3 Laurox S 0.62 0.44 14 10 CE23 P3 Trig.BPIC 0.36 — 95 8 CE24 P3 Trig.BPIC 0.36 0.22 12 13 CE25 P3 Trig.BPIC 0.36 0.44 1.8 13 CE26 P3 Luperox 0.36 — >150 1.5 802PP40 CE27 P3 Luperox 0.36 0.22 >150 5.7 802PP40 CE = comparative experiment E = example

[0081] Table 2 shows the effect of Laurox S in examples E1, E2, E11, E12, E21 and E22, which are examples according to the present invention and the effect of 2 other peroxides in comparative experiments CE3-CE8, CE13-CE18 and CE23-CE27, which comparative experiments are not according to the present invention. Furthermore three different polypropylene (PP) resins were tested.

[0082] The first PP-resin (P1) had a high rubber content, and therefore showed already a high Izod impact value at 23° C. The Izod impact value was 77 kJ/m2. Treatment with other peroxides (Trigonox and Luperox) resulted in either crosslinking (which gave a lower MFI value) or degradation of the polymer (which gave a higher MR value). At the same time for all comparative samples, the Izod impact values were lower than 77 kJ/m2. When the peroxide and co-agent of the present invention were added, the MFI values could be kept fairly constant and the impact of the polymer increased after the process of the invention. Moreover, the effect of the presence of the co-agent was rather independent from the concentration of co-agent, making the process a stable process.

[0083] The other two PP resins(P2 and P3) had a composition which contained a lower amount of rubber and therefore the impact values of the virgin material were 16 and 8 respectively. The difference in impact resistance resulted from the difference in MFI of both starting polymer compositions; a Product with a lower MFI gives a higher impact value.

[0084] For comparative experiments CE13-CE15 the use of Trigonox resulted first in an increase of MFI (in the absence of co-agent), but later in a strong decrease of MFI due to crosslinking, accompanied with a decrease of the impact. Moreover, the behaviour of the peroxide reaction was strongly dependent on the exact conditions: with only peroxide, an increase of MFI was shown which was due to polymer degradation, while with co-agent the MFI decreased to 4.8 g/10min, and with more co-agent decreased to 1 g/10min which was due to crosslinking. This means that the process with Trigonox as peroxide was very unstable, and slight changes in the process resulted in different polymers.

[0085] Furthermore, even at a significant lower MFI (CE15) the impact resistance obtained by using Trigonox was inferior compared to the impact resistance obtained by using Laurox (E12).

[0086] The use of Luperox showed (CE16-18) degradation of the polymer (increase of MFI) and a strong deterioration of the Impact values.

[0087] Examples E11-E12 with Laurox S (according to the invention) in combination with the co-agent divinylbenzene show a stable MFI and an increase of the Izod impact . The MFI did not depend very much on the level of coagent used, which made the process very stable.

[0088] Similar unstable MFI results were obtained for polymer P3 in comparative experiments C23 to C25 and stable MFI's for example E21-E22

[0089] The brittle to tough transition temperatures (BTT) were determined for the polymers resulting from examples E11, E12, E21 and E22 with the combination of Laurox S and divinylbenzene as co-agent.

[0090] The values of the BTT in parallel direction were compared (see table 3).

TABLE-US-00003 TABLE 3 Brittle to Tough transition Temperatures (BTT) Polymer T½ Gel Experiment composition peroxide 0.1 h DVB MFI BTT CXS wt % CE11 P2 N N 5.3 40 12 0 CE12 P2 Laurox S 99 N 6.8 40 12 0 E11 P2 Laurox S 99 Y 4.6 30 12 E12 P2 Laurox S 99 Y 4.8 20 11 2 CE21 P3 N N 14.4 60 12 CE22 P3 Laurox S 99 N 17 60 12 E21 P3 Laurox S 99 Y 15 38 12 E22 P3 Laurox S 99 Y 14 38 11 CE31 P2 Perkadox 14 156 N 11 4 CE32 P2 Perkadox 14 156 Y 2 9 CE33 P2 Trigonox BPIC 137 N 10 3 CE34 P2 Trigonox BPIC 137 Y 2 10 E31 P2 Trigonox 25 94 N 13 0 E32 P2 Trigonox 25 94 Y 8 3

[0091] Table 3 shows that the brittle to tough transitions of the polymer compositions prepared in the process according to the invention with Laurox S and divinylbenzene have been lowered, which is an improved result compared to the reference polymer compositions.

[0092] In case CE11 where no Laurox S and no DVB is used, the BTT is 40° C. With the use of both Laurox S and DVB, the BTT drops to 30° C. (0.22 wt % DVB) and 20° C. with 0.44 wt % DVB, while the impact increases to 19 and 36 kJ/mm2 respectively.

[0093] The effect of BTT decrease is even stronger at higher MFI levels. In CE21 with or without peroxide, but absent any accelerator, the BTT is 60° C. By using a small amount of DVB (0.22 and 0.44 wt %) the BTT drops to 38° C.

[0094] The amount of gel produced during the process according to the invention in combination with an accelerator also clearly gives an increase of the amount of gel being formed. When a peroxide is used having a decomposition half life time of 6 minutes (0.1 h) at a temperature below 109 celc, low levels of gels are obtained, especially in case Laurox S is being used.