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
2001-06-04
2002-06-11
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S296000, C525S331100, C525S331300, C525S332700
Reexamination Certificate
active
06403724
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to high damping polymer compositions that have high-temperature stability, mechanical strength and moldability, and excellent tan &dgr; values over a wide temperature range.
Two or more polymers may be blended together to form a wide variety of random or structured morphologies that can be used to provide products with potentially desirable combinations of characteristics. However, it may be difficult or even impossible in practice to achieve many potential combinations through simple blending because of some inherent and fundamental problems. Frequently, the polymers are thermodynamically immiscible, which precludes generating a truly homogeneous product. While immiscibility may not be a problem since it may be desirable to have a two-phase structure, the situation at the interface between these two phases very often leads to problems. The typical case is one of high interfacial tension and poor adhesion between the two phases. This interfacial tension contributes, along with high viscosities, to the inherent difficulty of imparting the desired degree of dispersion to random mixtures and to their subsequent lack of stability, giving rise to gross separation or stratification during later processing or use. Poor adhesion leads, in part, to the very weak and brittle mechanical behavior often observed in dispersed blends and may render some highly structure morphologies impossible.
Not-withstanding their recognized shortcomings, soft polymer compositions of two or more blended polymers are known in the art and have been considered useful in high damping applications. Such polymers are useful as cushions and vibration dampers, as well as other applications in which a degree of softness, heat resistance, elasticity, and good adhesion are desirable. Impeding to the use of soft polymers is their relatively poor high temperature stability and low hysteresis values.
One class of such soft polymers is centipede polymers. Centipede polymers have relatively long backbones with relatively short side chains. They are often formed by grafting the grafting of short polymer chains onto reactive sites in the long polymer chain. Additionally, centipede polymers can be extended to form a gel. Examples of such centipede polymers include polypropylene grafted poly(alkenyl-co-maleimide) polymer compositions. Specifically, this class of centipede polymers includes polypropylene grafted poly(alkenyl benzene-co-maleimide) compositions, polypropylene grafted poly(R
1
R
2
ethylene-co-maleimide) compositions, and polypropylene grafted poly(alkyl vinyl ether-co-maleimide) compositions. Centipede polymers of this type have been used in high damping materials, but still suffer from the aforementioned relatively low hysteresis values.
Dendrimers, also known as cascade polymers, are discrete, highly branched, monodispersed polymers that possess branching patterns reminiscent of trees and are readily described by mathematical progression. Dendrimers have three-dimensional globular structures. The most common class of dendrimers is radial, or starburst, dendrimers, which possess a radially symmetrical star-shaped architecture involving successive cascades of branched polymer structures.
Dendrimers have been used as crosslinkers due to their high functionality. Furthermore, that functionality may be highly controlled, with groupings of desirable functional groups on one or more segments of the dendrimer structure. Moreover, the identity of the functional groups may be varied throughout the molecule. Dendrimers are known for their ability to form gels as they become larger.
Providing a polymer composition that combines the beneficial properties of soft polymers and dendrimers remains desirable. Particularly desirable improved damping abilities.
SUMMARY OF THE INVENTION
The present invention provides a polymer composition including at least a monomer selected from a vinyl-substituted aromatic hydrocarbon, a R
1
R
2
ethylene, an alkyl vinyl ether, and a maleimide; a dendrimer; a maleated polyalkylene; a crosslinking agent; and, optionally, an extender. This composition demonstrates excellent tensile strength, tear strength, damping properties, high-temperature compression set, and hysteresis values.
According to one embodiment of the invention, the polymer composition includes a centipede polymer of (alkenyl-co-maleimide), maleated polyalkylene, and a dendrimer. The alkenyl monomer units in the centipede polymers can be a vinyl-substituted aromatic hydrocarbon, a R
1
R
2
ethylene, and/or an alkyl vinyl ether.
The following definitions apply herein throughout unless a contrary intention is expressly indicated:
“vinyl aromatic hydrocarbon” and “alkenyl benzene” are used interchangeably;
“maleic anhydride” encompasses dicarboxylic acids, including maleic anhydride, which can form a copolymer with an alkenyl benzene, an R
1
R
2
ethylene, or an alkyl vinyl ether, the copolymer having dicarboxylic acid units which are capable of reaction with an amine functional group;
“maleimide” encompasses the reaction product of an amine and the dicarboxylic acids described above;
“R
1
R
2
ethylene” encompasses compounds of the general formula:
where R
1
and R
2
are the same or different substituents and are independently hydrogen or substituted C
1
-C
20
alkyl groups;
“poly(alkenyl-co-maleimide)” includes poly(alkenylbenzene-co-maleimide), poly(R
1
R
2
ethylene-co-maleimide), and poly(alkyl vinyl ether-co-maleimide).
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The polymer composition of the present invention includes a centipede polymer and a dendrimer. Preferably, the centipede polymer contains (a) at least two monomer units such as (i) an alkenyl unit chosen from vinyl-substituted aromatic hydrocarbons, R
1
R
2
ethylenes, and alkyl vinyl ethers, and (ii) a maelemide, and (b) maleated polyalkylenes. The composition preferably further includes a crosslinking agent and an extender.
The centipede polymer can be formed by imidizing a poly(alkenyl-co-maleic anhydride) with a mono-primary amine. The centipede polymer has a high molecular weight spine with many relatively short side chains formed from the amines. The length of the main chain usually is at least as long as the entanglement length, which is herein defined theoretically as an order of magnitude of 100 repeating units, while the length of the side chains is less than the entanglement length.
Poly(alkenyl-co-maleimide) and poly(alkenyl-co-maleic anhydride) encompass random and stereospecific copolymers, including copolymers having a backbone with alkenyl-contributed units (i.e., monomer units derived from an alkenyl benzene such as styrene) and maleimide- or maleic anhydride-contributed units (i.e., monomer units derived from a maleimide or a maleic anhydride). Such structures may be alternating and are typically are described as poly(alkenyl-alt-maleimide) and poly(alkenylalt-maleic anhydride); however, these polymers are encompassed within the terms poly(alkenyl-co-maleimide) and poly(alkenyl-co-maleic anhydride). Exemplary copolymers include copolymers with a ratio of about 50% alkenyl contributed monomer units and about 50% maleimide contributed monomer units. However, copolymers with a ratio of at least about 20% alkenyl contributed monomer units are contemplated for use.
Preferred alkenyl benzene contributed monomer units of the poly(alkenyl benzene-co-maleimide) centipede are derived from one or more of styrene, &agr;-methylstyrene, 1-vinyl-naphthalene, 2-vinyl-naphthalene, 1-&agr;-methyl vinyl naphthalene, 2-&agr;-methyl naphthalene, as well as alkyl, cycloalkyl, aryl, alkaryl, and aralkyl derivatives thereof, in which the total number of carbon atoms in the combined hydrocarbon is not greater than about 18, as well as any di- or tri-vinyl aromatic hydrocarbons. Preferred vinyl aromatic hydrocarbons include styrene and a-methyl styrene.
Preferred R
1
and R
2
groups of R
1
R
2
ethylene contributed monomer units and the alkyl groups of said alkyl vinyl ether contributed monomer units are independently
Asinovsky Olga
Bridgestone Corporation
Burleson David G.
McCollister Scott A.
Seidleck James J.
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