Thermoplastic polymer compositions, methods for making the same, and articles made therefrom
Provided are thermoplastic polymer compositions having a single melting point, articles made therefrom, and methods for elevating the melting point of low melting point polymers. Thermoplastic polymer compositions are composed of one or more high melting point polyolefins and a thermoplastic component that includes a low melting point polypropylene. High melting point polyolefins are composed of a stereoregular polypropylene having a tacticity similar to the low melting point polypropylene. The low melting point polypropylene includes, for example, propylene homopolymers and copolymers composed of propylene and one or more comonomers. Thermoplastic polymer compositions may also optionally contain any of the various additives commonly used in such polymer compositions, such as for example oils, etc. In one embodiment, thermoplastic polymer compositions are thermoplastic elastomer compositions that include an elastomeric component composed of an elastomer or rubber. The elastomeric component may be substantially or partially crosslinked to form a thermoplastic vulcanizate.
1. A thermoplastic polymer composition comprising:
at least 40 weight percent, based on the weight of the thermoplastic polymer composition, of a thermoplastic component comprising low melting point copolymer having a melting temperature of greater than or equal to 107.5° C. and not more than about 150° C. composed of stereoregular polypropylene segments and from about 0.1 to about 5.0 weight percent of ethylene-derived units, based on the weight of the low melting point copolymer, and
at least 20 weight percent, based on the weight of the thermoplastic polymer composition, of a high melting point polyolefin having a melting point of greater than 150° C. and greater than the melting point of the low melting point copolymer,
wherein the thermoplastic polymer composition has a single melting point of at least 161.9° C.; and
wherein the melting point of the thermoplastic polymer composition is within at least about 15% of the melting point of the high melting point polyolefin according to the follow formula:
100
*
[
Tm
[
C
]
high
melting
point
polyolefin
-
Tm
[
C
]
thermoplastic
polymer
composition
]
Tm
[
C
]
high
melting
point
polyolefin
≤
15
%
.
2. The thermoplastic polymer composition of claim 1 , wherein the low melting point copolymer is prepared with a single site catalyst, Ziegler Natta catalyst, or combinations thereof.
3. The thermoplastic polymer composition of claim 1 , wherein the high melting point polyolefin is prepared with a single site catalyst, Ziegler Natta catalyst, or combinations thereof.
4. The thermoplastic polymer composition of claim 1 , wherein the low melting point copolymer is prepared with at least one catalyst selected from the group consisting of vanadium catalysts, Group IV-VI metallocenes, and Brookhart catalysts.
5. The thermoplastic polymer composition of claim 1 , wherein the high melting point polyolefin is prepared with at least one catalyst selected from the group consisting of vanadium catalysts, Group IV-VI metallocenes, and Brookhart catalysts.
6. The thermoplastic polymer composition of claim 1 , wherein the high melting point polyolefin is a substantially stereoregular polypropylene having substantially the same tacticity as the stereoregular polypropylene segments of the copolymer.
7. The thermoplastic polymer composition of claim 1 , wherein the thermoplastic polymer composition is composed of from about 20 to about 60 weight percent of high melting point polyolefin.
8. The thermoplastic polymer composition of claim 1 , further comprising an elastomeric component.
9. The thermoplastic polymer composition of claim 1 , wherein the thermoplastic polymer composition is a thermoplastic vulcanizate.
10. The thermoplastic polymer composition of claim 1 , wherein the single melting point of the thermoplastic polymer composition is greater than about 165° C.
11. An article comprising the thermoplastic polymer composition of claim 1 .
12. A method of elevating the melting point of a thermoplastic polymer composition comprising the steps of:
(a) providing at least 40 weight percent, based on the weight of the thermoplastic polymer composition, of a thermoplastic component comprising a low melting point copolymer having a melting temperature of greater than or equal to 107.5° C. and not more than about 150° C. composed of stereoregular polypropylene segments and from about 0.1 to about 7.0 weight percent, based on the weight of the copolymer, of comonomer, and
(b) combining the thermoplastic component with at least 20 weight percent, based on the weight of the thermoplastic polymer composition, of a high melting point polyolefin having a melting point of greater than 150° C. and greater than the melting point of the low melting point copolymer,
wherein the thermoplastic polymer composition has a single melting point of at least 161.9° C.; and
wherein the melting point of the thermoplastic polymer composition is within at least about 15% of the melting point of the high melting point polyolefin according to the follow formula:
100
*
[
Tm
[
C
]
high
melting
point
polyolefin
-
Tm
[
C
]
thermoplastic
polymer
composition
]
Tm
[
C
]
high
melting
point
polyolefin
≤
15
%
.
13. The method of elevating the melting point of a thermoplastic polymer composition of claim 12 , further comprising the steps of:
providing an elastomeric component, and
combining the thermoplastic component and the elastomeric component either before or after adding the high melting point polyolefin.
14. The method of elevating the melting point of a thermoplastic polymer composition of claim 13 , further comprising the step of curing the elastomeric component.
15. The method of elevating the melting point of a thermoplastic polymer composition of claim 12 , wherein the single melting point of the thermoplastic polymer composition is greater than about 165° C.