Soft and strong elastomeric compositions from semicrystalline-amorphous polyolefin block copolymers

• US 20080319116A1
• Filed: 04/08/2008
• Published: 12/25/2008
• Est. Priority Date: 04/09/2007
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Kramer, Edward J., Fredrickson, Glenn H., Wang, Zhigang
• Granted Patent: US 8,993,672 B2
• Time in Patent Office: Days
• US Class Current: 524/424
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/06 Rod-shaped
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/793 upstream of the plasticising zone, e.g. heating in the hopper
• CPC Class Codes: B29C 48/90 with calibration or sizing, i.e. combined with fixing or setting of the final dimensions of the extruded article
• CPC Class Codes: B29C 48/906 using roller calibration
• CPC Class Codes: C08J 2351/06 grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
• CPC Class Codes: C08J 2353/00 Characterised by the use of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
• CPC Class Codes: C08J 3/075 Macromolecular gels
• CPC Class Codes: C08L 2205/03 containing three or more polymers in a blend
• CPC Class Codes: C08L 2666/24 Graft or block copolymers according to groups C08L51/00, C08L53/00 or C08L55/02; Derivatives thereof
• CPC Class Codes: C08L 51/06 grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
• CPC Class Codes: C08L 53/00 Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers

Abstract

Polyolefin block and graft copolymers comprised of two or more semicrystalline polyolefin blocks or grafts and one or more amorphous polyolefin blocks can be blended with a low molecular weight fluid diluent that preferentially locates within and swells the amorphous domains of the block or graft copolymer, while preserving the crystallinity of the semicrystalline block domains. After mechanical or thermomechanical processing, such compositions combine softness with high strength and high recoverable elasticity. Compositions are also disclosed whereby the diluent species is removed from the composition, either before or after the mechanical or thermomechanical processing, in order to create a strong elastic material with an ultra-low entanglement density within the amorphous domains.

Claims

1. A polymer gel composition comprising a mixture of (a) one or more semicrystalline polyolefin block or graft copolymers and (b) one or more low molecular weight fluid diluents, wherein:

each semicrystalline polyolefin copolymer is an A-B block or graft co-polymeric material comprised of two or more blocks or grafts of a semicrystalline polyolefin A bridged by one or more blocks of an amorphous polyolefin B;

each low molecular weight fluid diluent is miscible or partially miscible with the amorphous B blocks of the semicrystalline block copolymer, and does not dissolve the crystals of the semicrystalline A blocks or grafts of the semicrystalline block or graft copolymer at the use temperature, and whose glass transition temperature is below the use temperature;

the gel composition having been produced by combining the one or more semicrystalline polyolefin block or graft copolymers and one or more low molecular weight fluid diluents has crystals that can be deformed by a mechanical or thermomechanical process to produce a material with an initial elastic modulus at strains less than 1, an elastic tangent modulus at large strains just prior to break, the ratio of the tangent modulus prior to break to the initial modulus exceeding 50, and

those large strains being more than 70% recovered when the stress or restraining force is removed

2. The composition of claim 1, wherein the strain just prior to break is greater than 5.

3. The composition of claim 1 wherein the semicrystalline polyolefin block copolymer is an ABA triblock copolymer, an ABABA pentablock copolymer, or an (AB)n radial block copolymer.

4. The composition of claim 1 wherein the semicrystalline polyolefin block copolymer is a multiblock copolymer with architecture . . . ABABAB . . . , with block sizes and number of blocks per chain determined by a statistical process, and where the number average molecular weight of the A semicrystalline blocks is greater than 500 g/mole and the number average molecular weight of the B amorphous blocks is greater than 1000 g/mole.

5. The composition of claim 1 wherein the semicrystalline polyolefin block copolymer is a graft copolymer comprised of an amorphous B backbone of number average molecular weight greater than 1000 g/mole to which is attached two or more grafts (branches) of semicrystalline polymer A, the grafts having number average molecular weight greater than 500 g/mole.

6. The compositions of claim 1 wherein the amorphous B polyolefin blocks of the semicrystalline polyolefin block copolymer have a glass transition temperature below the use temperature, and the crystals of the A polyolefin blocks or grafts melt at a temperature above the use temperature, such that the semicrystalline block copolymer alone has the mechanical properties of a thermoplastic elastomer.

7. The compositions of claim 1 wherein the A polymer blocks or grafts are semicrystalline polyolefins selected from the group consisting of polyethylene, syndiotactic polypropylene, isotactic polypropylene, isotactic poly(1-butene), syndiotactic poly(1-butene), isotactic or syndiotactic higher alpha-olefins including poly(1-hexene) or poly(1-octene);

or isotactic or syndiotactic variants of poly(4-methyl-1-pentene), poly(3-methyl-1-butene), poly(4,4-dimethyl-1-pentene), or poly(vinylcyclohexane).

8. The compositions of claim 1 wherein the amorphous B polymer blocks are polyolefins selected from the group consisting of atactic or regio-irregular polypropylenes;

atactic poly(alpha-olefins) including poly(1-butene), poly(1-hexene), or poly(1-octene);

polyolefin random or statistical copolymers selected from the group consisting of poly(ethylene-r-propylene), poly(ethylene-r-butene), poly(ethylene-r-pentene), poly(ethylene-r-hexene), poly(ethylene-r-heptene), poly(ethylene-r-isobutylene), and poly(ethylene-r-octene);

or atactic or regio-irregular random or statistical copolymers formed by copolymerization of propylene with one or more higher alpha-olefins and with or without ethylene.

9. The compositions of claim 1 wherein the amorphous B polymer blocks are polyolefin compounds produced by hydrogenation of polyisoprenes, polybutadienes, or their random copolymers and wherein the semicrystalline A polymer blocks or grafts are polyolefin compounds produced by hydrogenation of polybutadiene.

10. The compositions of claim 1 wherein the low molecular weight fluid diluent is a low molecular weight organic compound with low volatility such as a mineral oil, a paraffin oil, a plasticizer, a low volatility solvent, or a tackifier;

or a low molecular weight organic compound with higher volatility such as decalin.

11. The compositions of claim 1 wherein the low molecular weight fluid diluent is carbon dioxide in liquid, vapor or supercritical fluid form.

12. The polymer gel composition of claim 1, wherein an A-B block or graft copolymer with two or more blocks or grafts of a semicrystalline polyolefin A, bridged by one or more blocks of an amorphous polyolefin B, is mixed with a second polyolefin C-D block or graft co-polymeric material comprised of two or more blocks or grafts of a semicrystalline polyolefin C bridged by one or more blocks of an amorphous polyolefin D, wherein polymers B and D are either the same or different, wherein the low molecular weight fluid diluent is miscible or partially miscible with the amorphous B and D blocks, and does not dissolve the crystals of the semicrystalline A and C blocks or grafts, and wherein the crystals of A and C can be deformed.

13. The composition of claim 12 wherein the semicrystalline polyolefin block copolymers is a mixture of an ABA triblock copolymer and a CDC triblock copolymer.

14. The composition of claim 12 wherein the semicrystalline polyolefin block copolymers is a mixture of a multiblock copolymer of architecture . . . ABABAB . . . having block sizes and number of blocks per chain determined by a statistical process, and where the A semicrystalline polyolefin blocks have a number average molecular weight of greater than 500 g/mole and the B amorphous polyolefin blocks have a number average molecular weight of greater than 1000 g/mole, with a second semicrystalline polyolefin block copolymer of CDC triblock architecture, or architecture . . . CDCDC . . . having block sizes and number of blocks per chain determined by a statistical process, and where the C semicrystalline blocks have a number average molecular weight of greater than 500 g/mole and the D amorphous polyolefin blocks have a number average molecular weight of greater than 1000 g/mole, and including the situation where polymers B and D are the same.

15. The compositions of claims 12 wherein the amorphous B and D polyolefin blocks of the semicrystalline polyolefin block copolymers have glass transition temperatures below the use temperature, and the crystals of the A and C polyolefin blocks or grafts melt at a temperature above the use temperature, such that the semicrystalline block copolymer mixture alone has the mechanical properties of a thermoplastic elastomer.

16. The compositions of claims 12 wherein the A and C polyolefin blocks or grafts are compounds selected from the group consisting of semicrystalline polyethylene, syndiotactic polypropylene, isotactic polypropylene, isotactic poly(1-butene), syndiotactic poly(1-butene), isotactic or syndiotactic higher alpha-olefins including poly(1-hexene) or poly(1-octene);

or isotactic or syndiotactic variants of poly(4-methyl-1-pentene), poly(3-methyl-1-butene), poly(4,4-dimethyl-1-pentene), or poly(vinylcyclohexane).

17. The compositions of claims 12 wherein the amorphous B and D polyolefin blocks are selected from the group consisting of atactic or regio-irregular polypropylenes;

atactic poly(alpha-olefins) including poly(1-butene), poly(1-hexene), or poly(1-octene);

polyolefin random or statistical copolymers selected from the group consisting of poly(ethylene-r-propylene), poly(ethylene-r-butene), poly(ethylene-r-pentene), poly(ethylene-r-hexene), poly(ethylene-r-heptene), poly(ethylene-r-isobutylene), and poly(ethylene-r-octene);

or atactic or regio-irregular random or statistical copolymers formed by copolymerization of propylene with one or more higher alpha-olefins and with or without ethylene.

18. The compositions of claims 12 wherein the amorphous B polymer blocks are polyolefin compounds produced by hydrogenation of polyisoprenes, polybutadienes, or their random copolymers and wherein the semicrystalline A polymer blocks or grafts are polyolefin compounds produced by hydrogenation of polybutadiene.

19. The compositions of claims 12 wherein the low molecular weight fluid diluent is a low molecular weight liquid organic compound with low volatility such as a mineral oil, a paraffin oil, a plasticizer, a low volatility solvent, or a tackifier;

or a low molecular weight organic compound with higher volatility such as decalin.

20. The compositions of claims 12 wherein the low molecular weight fluid diluent is carbon dioxide in liquid, vapor or supercritical fluid form.

21. The composition of claim 1 wherein the semicrystalline block copolymer is an A-B-C polyolefin triblock copolymer comprised of semicrystalline A and C polyolefin blocks, bridged by an amorphous polyolefin block B, and wherein each low molecular weight fluid diluent is miscible or partially miscible with the amorphous B blocks of the semicrystalline block copolymer, and does not dissolve the crystals of the semicrystalline A and C blocks of the semicrystalline block copolymer at the use temperature, and whose glass transition temperature is below the use temperature.

22. The compositions of claim 1 that result when the low molecular weight fluid diluent is removed from the composition after the A blocks or grafts of the semicrystalline polyolefin block or graft copolymers have crystallized, either before or after the crystals are subsequently deformed by a mechanical or thermomechanical process, to produce a material with an initial elastic modulus at strains less than 1, an elastic tangent modulus at large strains just prior to break, the ratio of the tangent modulus prior to break to the initial modulus exceeding 50, and those large strains being more than 70% recovered when the stress or restraining force is removed.

23. The compositions of claims 12 that result when the low molecular weight fluid diluent is removed from the composition after the A and C blocks or grafts of the semicrystalline polyolefin block or graft copolymers have crystallized, either before or after the crystals are subsequently deformed by a suitable mechanical or thermomechanical process, to produce a material with an initial elastic modulus at strains less than 1, an elastic tangent modulus at large strains just prior to break, the ratio of the tangent modulus prior to break to the initial modulus exceeding 50, and those large strains being more than 70% recovered when the stress or restraining force is removed.

24. A method for producing a polymer gel composition comprising:

mixing one or more semicrystalline polyolefin block or graft copolymers and one or more low molecular weight fluid diluents;

heating the mixture;

annealing the mixture; and

cooling the mixture.

25. The method of claim 24, further comprising a mechanical or thermomechanical step that converts the gel composition into crystals isolated by the elastomer or gel fluid matrix in which the crystals are now of a suitable form to produce a large elastic modulus (tangent modulus) at large strain, a strain that can be more than 70% recovered when the strain is removed.

26. The method of claim 25, wherein the mechanical or thermomechanical step is selected from the group consisting of simple extension in tension, repeated simple extension in tension and relaxation to zero stress where a larger maximum strain is reached on every cycle of extension and relaxation, biaxial extension, incremental biaxial extension and relaxation as in the simple tension example, extrusion of the material through a suitably shaped die or into a suitably shaped cavity, extrusion of the material through a die followed by application of stretching along the extrusion direction, extrusion of the material through a die followed by application of stretching along both the extrusion direction and the direction transverse to it;

and deformation leading to a decrease in the thickness of the material by squeezing it between a set of rollers or any sequence of sets of rollers allowing a decrease in thickness, relaxation, a further decrease in thickness, relaxation and so on.

27. The method of claim 26, wherein temperature changes would be imposed during or in between any of the steps of the process.

28. The method of claim 26, further comprising removing the low molecular weight fluid diluent from the composition after the blocks or grafts of the semicrystalline block or graft copolymers have crystallized, either before or after the crystals are subsequently deformed by a suitable mechanical or thermomechanical process, to produce a material with an initial elastic modulus at strains less than 1, an elastic tangent modulus at large strains just prior to break, the ratio of the tangent modulus prior to break to the initial modulus exceeding 50, and those large strains being more than 70% recovered when the stress or restraining force is removed.

29. The polymer gel compositions produced by the method of claim 25.

30. The polymer compositions produced by the method of claim 28.

31. A method for producing a polymer gel composition comprising:

mechanically combining one or more semicrystalline polyolefin block or graft copolymers and one or more low molecular weight fluid diluents at elevated temperature using standard polymer processing equipment such as a compounder, mixer, or extruder; and

cooling the mixture.

32. The method of claim 31, further comprising a mechanical or thermomechanical step that converts the gel composition into crystals isolated by the elastomer or gel fluid matrix in which the crystals are now of a suitable form to produce a very large elastic modulus (tangent modulus) at large strain, a strain that can be more than 70% recovered when the strain is removed.

33. The method of claim 32, wherein the mechanical or thermomechanical step is selected from the group consisting of simple extension in tension, repeated simple extension in tension and relaxation to zero stress where a larger maximum strain is reached on every cycle of extension and relaxation, biaxial extension, incremental biaxial extension and relaxation as in the simple tension example, extrusion of the material through a suitably shaped die or into a suitably shaped cavity, extrusion of the material through a die followed by application of stretching along the extrusion direction, extrusion of the material through a die followed by application of stretching along both the extrusion direction and the direction transverse to it;

and deformation leading to a decrease in the thickness of the material by squeezing it between a set of rollers or any sequence of sets of rollers allowing a decrease in thickness, relaxation, a further decrease in thickness, relaxation and so on.

34. The method of claim 33, wherein temperature changes would be imposed during or in between any of the steps of the process.

35. The method of claim 33, further comprising removing the low molecular weight fluid diluent from the composition after the blocks or grafts of the semicrystalline block or graft copolymers have crystallized, either before or after the crystals are subsequently deformed by a suitable mechanical or thermomechanical process, to produce a material with an initial elastic modulus at strains less than 1, an elastic tangent modulus at large strains just prior to break, the ratio of the tangent modulus prior to break to the initial modulus exceeding 50, and those large strains being more than 70% recovered when the stress or restraining force is removed.

36. The polymer gel compositions produced by the method of claim 32.

37. The polymer compositions produced by the method of claim 35.