Process for making dynamically-loaded articles comprising propylene-based elastomers, composition for use in such processes, and article made using such processes

Abstract

The invention relates to a process for making an article subject to dynamic loading, the process comprises: (i) shaping a polymer-containing composition in the green state, the composition comprising (a) a continuous phase of a polymeric component of at least 15 wt %, based on the total weight of the polymer component of a propylene elastomer having a heat of fusion of less than 70 J/g and an isotactic triad tacticity of 50 to 99% and optionally containing units derived from a diene, the polymeric component having a density of less than 0.9 g/cm3 and (b) from 20 to 120 phr, preferably 30 to 100 phr, most preferably 40 to 90 phr based on the total weight of the polymer component of a reinforcing filler component; and (c) a peroxide curative. The composition is combined with a fibrous reinforcement which is then cured to a cure state as determined by ODR @ 170° C., 30 min MH-ML of from 5 to 80 dNm. The invention especially relates to such processes when providing under Demattia testing conditions a crack length of less than 15 mm at room temperature over 90K cycles, preferably 10 mm, more preferably 7 mm, and most preferably 4 mm, and a 10% modulus of 0.7 to 10 MPa, preferably 1.4 to 9 MPa and most preferably 2 to 8 MPa.

Description

DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of a Soxhlet extraction apparatus as is referred to in paragraph [0060];

FIG. 2 is a graph showing variations of the DeMattia Crack Length with the modulus as indicated in the Examples, with “polymer” referring the polymer compositions of the invention; and

FIG. 3 is a graph showing variations of the modulus with cure state in the Examples.

Claims

1. A process for making an article for subjecting to dynamic loading comprising: (i) shaping a polymer-containing composition in the green state, the composition comprising: (a) a continuous phase of a polymeric component comprising at least 15 wt % based on the total weight of the polymer component of a propylene elastomer having a heat of fusion of less than 70 J/g and an isotactic triad tacticity of 50 to 99% and optionally containing units derived from a diene, the polymeric component having a density of less than 0.9 g/cm3;(b) a reinforcing filler component in an amount of from 20 to 120 phr based on the total weight of the polymer component;(c) a peroxide curative and(d) a fibrous reinforcement; and(ii) curing the shaped composition to a cure state as determined by ODR @ 170° C., 30 min. MH-ML of from 5 to 80 dNm.

2. A process according to claim 1 wherein the curative comprises at least one co-agent for forming reversible ionic links or for forming covalent bonds between chains for improving the crack resistance.

3. A process according to claim 1 wherein the composition comprises a polymeric adjuvant, preferably an olefin-based polymer different from the propylene elastomer which may or may not be miscible with the propylene elastomer.

4. A process according to claim 2 wherein the composition comprises a polymeric adjuvant, preferably an olefin-based polymer different from the propylene elastomer which may or may not be miscible with the propylene elastomer.

5. A process according to claim 1 wherein the composition has an overall heat of fusion of from 3 to 75 J/g.

6. A process according to claim 1 further comprising ≦20 wt % based on the total weight of the polymer component of an isotactic semicrystalline polypropylene having a heat of fusion of more than 70 J/g.

7. A process according to claim 6 further comprising ≦10 wt % based on the total weight of the polymer component of an isotactic semicrystalline polypropylene having a heat of fusion of more than 70 J/g.

8. A process according to claim 1 wherein the cured composition has a cure state of from 5 to 60 dNm and a 10% modulus of from 0.7 to 10 MPa.

9. A process according to claim 8 wherein the cured composition has a cure state of from 10 to 30 and a 10% modulus of from 5 to 10 MPa.

10. A process according to claim 1 wherein the peroxide 1 minute half life is less than 185° C.

11. A process according to claim 1 wherein the composition comprises less than 10 wt % of a polypropylene having a heat of fusion of above 90 J/g in the green state and has a Mooney ML(1+4)(125° C. of from 15 to 65.

12. A process according to claim 1 wherein the propylene elastomer comprises from 0.1 to 8 wt % of diene-derived comonomer units for promoting curing and the cure state as determined by ODR @ 170° C., 30 min MH-ML is from 20 to 50 dNm or wherein the polymer comprises substantially no unsaturated moieties and the cure state as determined by ODR @ 170° C., 30 min MH-ML is from 20 to 50 dNm.

13. A process according to claim 1 wherein the reinforcing filler component comprises carbon black, silica, talc or a reinforcing fiber distributed through a continuous polymer phase.

14. A process according to claim 13 wherein the reinforcing fiber is a carbon fiber or nano-clay distributed through a continuous polymer phase.

15. A process according to claim 1 wherein the polymeric component comprises less than 30 phr of the processing oil.

16. A process according to claim 15 wherein the processing oil is a poly-alpha-olefin and/or an adhesion promoter.

17. A process according to claim 1 wherein the propylene elastomer comprises from 5 to 35 wt % of one or more alpha-olefins, the weight percentages being based on the total propylene elastomer weight, and/or has a heat of fusion of from 3 to 40 J/g as measured by DSC, and/or an MFR of from 0.5 to 50 g/10 min.

18. A process according to claim 1 wherein the polymeric component further comprises an elastomeric ethylene-based copolymer with an alpha-olefin having from 3 to 10 carbon atoms and a density of from 0.85 to 0.91 g/cm3, a chlorinated ethylene-based polymer, and/or an ethylene-based polymer with oxygen-containing moieties having a crystallinity of less than 80 J/g.

19. A process according to claim 1 wherein the uncured composition has a green strength as measured by the 10% modulus of from 0.8 to 10 MPa.

20. A process according to claim 1 wherein the article is a belt and the fibrous reinforcement is the form of a fibrous web, fabric or filament bundle in the green state.

21. A process according to claim 20 wherein the polymer containing composition is applied directly to the fibrous reinforcement.

22. A process according to claim 20 wherein the belt is shaped by forming it around a mandrel with a joint at facing edges; and ribs are formed in the belt in the direction of movement of the belt by a molding step in the uncured condition or by grinding grooves in the cured state.

23. A process according to claim 21 wherein the belt is shaped by forming it around a mandrel with a joint at facing edges; and ribs are formed in the belt in the direction of movement of the belt by a molding step in the uncured condition or by grinding grooves in the cured state.

24. A process according to claim 1 wherein the cured polymer containing composition has, under Demattia testing conditions, a crack length of less than 15 mm at room temperature over 90K cycles.

25. A process according to claim 1 wherein the cured polymer containing composition has a 10% modulus of 0.7 to 10 MPa.

26. A process according to claim 1 wherein the cured polymer containing composition has Tear Resistance at 125° C. of 15 to 60 N/mm.

27. A process according to claim 1 wherein the cured polymer containing composition has an ageing performance as determined the change in Shore A hardness of ≦5 after Heat Aging—168 hr @ 125° C.

28. A process according claim 1 wherein the cured polymer has, under Demattia testing conditions, a Crack Length at 90 k Cycles (CL@90 k) as measured in mm, and the 10% Modulus (10% M) as measured in MPa complying with the inequality CL@90 k<(5×10% M)+10, preferably CL@90 k<(5×10% M)+5 and most preferably CL@90 k<(5×10% M)+3.

29. A polymer composition for use in the manufacture of an belt, the composition comprising: (a) a continuous phase of a polymeric component comprising at least 15 wt % based on the total weight of the polymer component of a propylene elastomer having a heat of fusion of less than 70 J/g, an isotactic triad tacticity of 50 to 99% and optionally containing units derived from a diene and an MFR of from 0.5 to 50 g/10 min, the polymeric component having a density of less than 0.9 g/cm3 and (b) from 20 to 120 phr based on the total weight of the polymer component of a reinforcing filler component; and (c) a peroxide curative and (d) optionally a processing oil and/or adhesion promoter.

30. A polymer composition according to claim 25 wherein the propylene elastomer comprises from 4-35 wt % of one or more alpha olefins.

31. A polymer composition according to claim 30 wherein the one or more alpha olefins are selected from ethylene and/or a C4-C20 alpha olefin.

32. A polymer composition according to claim 31 wherein the propylene elastomer has a melting point ≦105° C.

33. A polymer composition according to claim 32 wherein the propylene elastomer comprises from 5-16 wt % of one or more alpha-olefins.

34. A polymer composition according to claim 31 further comprising an elastomeric ethylene-based copolymer with an alpha-olefin having from 3 to 10 carbon atoms and a density of from 0.85 to 0.91 g/cm3, a chlorinated ethylene-based polymer, and/or an ethylene-based polymer with oxygen-containing moieties having a crystallinity of less than 80 J/g.

35. A belt subjectable to dynamic loading produced by the process of (i) combining an uncured polymer-based composition and a reinforcement, the polymer-based composition comprising (a) a continuous phase of a polymeric component of at least 15 wt % based on the total weight of the polymer component of a propylene elastomer having a heat of fusion of less than 70 J/g, an isotactic triad tacticity of 50 to 99% and optionally containing units derived from a diene and an MFR of from 0.5 to 50 g/10 min, the polymeric component having a density of less than 0.9 and (b) from 20 to 120 phr, based on the total weight of the polymeric component, of a reinforcing filler component; (c) a peroxide curative and (d) optionally a processing oil and/or adhesion promoter, the polymer-based composition having a Demattia crack length of less than 15 mm at room temperature over 90K cycles; and (ii) curing the combination.

36. A belt according to claim 35 wherein the polymer-based composition is cured in the shaped state to a cure state as determined by ODR @ 170° C., 30 min MH-ML of from 5 to 80 dNm.

37. A belt according to claim 35 wherein the propylene-based elastomer has a melting point less than 105° C., comprises from 4-35 wt % of one or more alpha-olefins.

38. A belt according to claim 37 wherein the one or more alpha olefins comprise ethylene, butene, hexene, octene, or a combination thereof.

39. A belt according to claim 37 wherein the reinforcing filler component comprises carbon black, silica, talc or a reinforcing fiber distributed through a continuous polymer phase.

40. A belt according to claim 35 wherein the belt is in the form of a micro-V-belt.