Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-02-18
2002-03-19
Szekely, Peter (Department: 2875)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000
Reexamination Certificate
active
06359068
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to compositions comprising blends of polypropylene and thermoplastic block copolymers.
Many polymer blends are known and used in different industries. For example, polymer blends are important in the development of pressure-sensitive adhesives that are used to make tapes and transdermal patches. The characteristics of a pressure sensitive adhesive depends on the amount and the types of polymers used to make the adhesive. Preferred pressure sensitive adhesives include rubber-based adhesives, which consist of blends of natural or synthetic rubber and tackifier resins. Typically the use of thermoplastic block copolymers in adhesive compositions provide strength and shear resistance in the adhesive. Other examples that include polypropylene and thermoplastic block copolymer blends are used to produce compositions amiable to molding processes. The resultant thermoplastic blends having high impact resistance, good oxidative stability, and are used in a variety of applications.
The thermoplastic block copolymers used in polymer blends are a unique class of elastomers. Some block copolymers have hard segments of polystyrene combined with soft segments, such as the commercially available KRATON thermoplastic polymers, sold by the Shell Chemical Company, Houston, Tex. These thermoplastic block copolymers can be blended with many plastics, such as styrenics, polyolefins and engineering thermoplastics to improve their performance, particularly their impact properties. These thermoplastic block copolymers toughen such plastics both at room and low temperatures and can also make dissimilar plastics compatible. And with the right grade of thermoplastic block copolymers, such toughening or compatibilization can be achieved efficiently, while retaining high heat resistance, good processability, good weatherability, and in certain cases, clarity.
Mixing thermoplastic block copolymers with plastics typically produce compositions having measured physical characteristics between the measured physical characteristics of the plastic or the thermoplastic block copolymer used to make the compositions. Specifically, compositions produced by mixing a thermoplastic block copolymer and an isotactic polypropylene having about 100 percent isotactic linkages will usually have toughness and abrasion resistance measurements between the toughness and abrasion resistance measurements of the specified thermoplastic block copolymer and the specified polypropylene used to make the composition.
SUMMARY OF THE INVENTION
The present invention embodies blends including polypropylenes and thermoplastic block copolymers, wherein the blend has specific physical characteristic more desirable than the physical characteristic of the polypropylene and the thermoplastic block copolymer used to make the blend. One embodiment of the invention is a composition comprising a polypropylene including less than 90 percent isotactic linkages, and a thermoplastic block copolymer comprising hard segments of polystyrene combined with soft segments comprising carbon chains including 2 to 8 carbon atoms. The breaking stress measurement of the composition is greater than the breaking stress measurement of the specified polypropylene and the specified thermoplastic block copolymer used to make the composition.
Another embodiment of the invention is a composition comprising a polypropylene comprising about 50 percent to 70 percent isotactic linkages, and a thermoplastic block copolymer comprising hard segments of polystyrene combined with soft segments including ethylene and butylene. This composition contains some physical characteristics that are more desirable than the physical characteristics of the polypropylene and the thermoplastic block copolymer used to make the composition. Such physical characteristics include tensile breaking stress, abrasion resistance, and percent elongation at break.
Another embodiment of the invention is a composition comprising a polypropylene including less than 90 percent isotactic linkages, and a thermoplastic block copolymer comprising hard segments of polystyrene combined with soft segments comprising carbon chains including 2 to 8 carbon atoms. The abrasion resistance measurement (as measured in grams abraded) of the composition is less than the abrasion resistance measurement (as measured in grams abraded) of the specified polypropylene and the specified thermoplastic block copolymer used to make the composition.
DETAILED DESCRIPTION
Embodiments of the invention generally are compositions that include a polypropylene and a thermoplastic block copolymer.
Polypropylene
Suitable polypropylenes for making a composition of this invention have less than 90 percent isotactic linkages. A blend of these polypropylenes and thermoplastic block copolymers provide a composition having specific physical characteristics more desirable than the polypropylene or thermoplastic block copolymer used to make the composition. Isotactic linkages refers to one of the three arrangements that are possible during the polymerization of propylene in which all methyl groups are on one side of an extended chain. The procedure for measuring the percent isotactic linkages of polypropylene is described in the Example Section of this patent application labeled Procedure II For Measuring The Tacticity Of Polypropylene. Examples of polypropylenes with less than 90 percent isotactic linkages include the products sold under the tradename REXFLEX FPO W101, REXFLEX FPO W108, and REXFLEX FPO W104 by the Rexene Products Company of Dallas, Tex. It is even more desirable that the polypropylenes used in the invention have about 50 percent to 70 percent isotactic linkages.
Thermoplastic Block Copolymers
The composition of this invention includes polypropylene having less than 90 percent isotactic linkages and thermoplastic block copolymers. The thermoplastic block copolymers used to make a layer of cover material are selected based on compatibility with the polypropylene and their ability to provide a composition having specific physical characteristics more desirable than the polypropylene or thermoplastic block copolymer used to make the composition. In general terms, block copolymers are macromolecules comprising chemically dissimilar, terminally connected segments. Their sequential arrangement can vary from A—B structures, containing two segments only, to A—B—A block copolymers with three segments, to multiblock —(A—B)
n
— systems possessing many segments. A unique development resulting from block copolymer technology is the concept of thermoplastic elastomeric behavior. Block copolymer systems of this type are characterized by rubbery behavior in the absence of chemical cross-linking. This feature permits the fabrication of these materials by means of conventional thermoplastic processing techniques. The key to this unique behavior is the ability to achieve a network structure by physical rather than chemical means. This, in turn results from finely controlled morphology in A—B—A or —(A—B)
n
— systems containing both flexible and rigid segments.
The simplest arrangement, or architecture, of a block copolymer is the diblock structure, commonly referred to as an A—B block copolymer, which is composed of one segment of “A” repeat units and one segment of “B” repeat units. The second form is the triblock, or A—B—A structure, containing a single segment of B repeat units located between two segments of “A” repeat units. The third basic type is the —(A—B)
n
— multiblock copolymer, are composed of many alternating “A” and “B” blocks. Another, but less common, variation is the radial block copolymer. This structure takes the form of a star-shaped macromolecule in which three or more diblock sequences radiate from a central hub. Suitable thermoplastic block copolymers may have one of the above architectures. It is preferred that the thermoplastic block copolymer in this invention is the triblock, or A—B—A structure.
From a mechanical property point of view, block copolymers may be conveniently d
Moren Louis S.
Welygan Dennis G.
3M Innovative Properties Company
Allen Gregory D.
Szekely Peter
LandOfFree
High-friction polymer blends comprising polypropylene and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High-friction polymer blends comprising polypropylene and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-friction polymer blends comprising polypropylene and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2832887