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
1998-08-26
2001-09-04
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000, C525S241000, C525S333500, C525S333800, C525S351000
Reexamination Certificate
active
06284842
ABSTRACT:
BACKGROUND OF THE INVENTION
Interpolymers of the class which include &agr;-olefin/hindered vinyl monomer substantially random interpolymers and include materials such as &agr;-olefin/vinyl aromatic monomer interpolymers are known in the art and offer a range of material structures and properties which makes them useful for varied applications, such as compatibilizers for blends of polyethylene and polystyrene as described in U.S. Pat. No. 5,460,818.
As described by D'Anniello et al. (Journal of Applied Polymer Science, Volume 58, pages 1701-1706 (1995)), such interpolymers can show good elastic properties and energy dissipation characteristics. Alternatively, certain of the interpolymers are useful in adhesive systems, as illustrated for instance in U.S. Pat. No. 5,244,996, issued to Mitsui Petrochemical Industries Ltd.
It would be desirable to provide improvements in processability or performance without the addition of additives commonly used to improve properties of the interpolymers or enhance properties that can be achieved by using additives and would be more desirable to achieve combinations of properties not attainable using blends of polymers alone. Alternatively, characteristics of a blend produced to obtain certain desirable characteristics would advantageously be further improved by practice of the present invention. Characteristics which would desirably improve would include at least one of low temperature toughness, mechanical strength, heat resistance and melt processability, preferably heat resistance,
Coupling of polymers results in rheology modification of the polymer. As used herein, the term “rheology modification” means change in melt viscosity of a polymer as determined by dynamic mechanical spectroscopy. Preferably the melt strength increases while maintaining the high shear viscosity (that is viscosity measured at a shear of 100 rad/sec by DMS) so that a polymer exhibits more resistance to stretching during elongation of molten polymer at low shear conditions (that is viscosity measured at a shear of 0.1 rad/sec by DMS) and does not sacrifice the output at high shear conditions.
Use of poly(sulfonyl azide)s to react with polymers is known for instance in The teachings of U.S. Pat. Nos. 3,058,944; 3,336,268; and 3,530,108 include the reaction of certain poly(sulfonyl azide) compounds with isotactic polypropylene or other polyolefins by nitrene insertion into C—H bonds. The product reported in U.S. Pat. No. 3,058,944 is crosslinked. The product reported in U.S. Pat. No. 3,530,108 is foamed and cured with cycloalkane-di(sulfonyl azide) of a given formula. In U.S. Pat. No. 3,336,268 the resulting reaction products are referred to as “bridged polymers” because polymer chains are “bridged” with sulfonamide bridges. The disclosed process includes a mixing step such as milling or mixing of the sulfonylazide and polymer in solution or dispersion then a heating step where the temperature is sufficient to decompose the sulfonylazide (100° C. to 225° depending on the azide decomposition temperature). The starting polypropylene polymer for the claimed process has a molecular weight of at least about 275,000. Blends taught in U.S. Pat. No. 3,336,268 have up to about 25 percent ethylene propylene elastomer.
Similarly, the teachings of Canadian patent 797,917 (family member of NL 6,503,188) include rheology modification using from about 0.001 to 0.075 weight percent polysulfonyl azide to modify homopolymer polyethylene and its blend with polyisobutylene.
It would also be desirable to use a polymer of enhanced melt strength in a foaming process preferably to achieve at least one of smaller cell diameter, homogeneous cell diameter distribution, lower foam density, higher tensile and compressive strength, higher tensile or compressive toughness. Preferably, the polymer would have at most little high shear viscosity increase over a corresponding polymer of the same chemical composition, but not modified to obtain the enhanced melt strength, e.g. the starting material polymer, so that it would have smaller processing characteristics as the unmodified polymer.
SUMMARY OF THE INVENTION
It has been found that blends of interpolymers made from monomer components comprising at least one &agr;-olefin and at least one aromatic vinyl monomer and/or at least one hindered aliphatic vinyl monomer and/or at least one cycloaliphatic vinyl monomer with olefinic polymers, said blends having been heated with at least one poly(sulfonyl azide) at least to the decomposition temperature of the poly(sulfonyl azide), advantageously have improvements in at least one of low temperature toughness, mechanical strength, heat resistance or processability, preferably heat resistance.
This improvement is believed to result from the poly(sulfonyl azide) reacting with more than one polymer chain to connect them, referred to herein as “coupling” and the poly(sulfonyl azide), as a “coupling agent.” Coupling results in and is measured by rheology modification.
Preferably, blends of the invention having their rheology modified by treatment with poly(sulfonyl azide) coupling agents advantageously have increased melt strength useful in foaming.
The invention includes a process of preparing a coupled polymer blend comprising heating an admixture containing (1) a polymer blend containing:
(A) from 1 to 99 weight percent based on entire composition of one or more &agr;-olefin/hindered vinyl monomer substantially random interpolymers, each having been made from monomer components comprising:
(1) from 0.5 to 65 mole percent of either
(a) at least one vinyl aromatic monomer, or
(b) at least one hindered aliphatic vinyl monomer, or
(c) a combination of at least one vinyl aromatic monomer and at least one hindered aliphatic monomer; and
(2) from 35 to 99.5 mole percent of at least one aliphatic &agr;-olefin having from 2 to 20 carbon atoms; and
(B) from 99 to 1 weight percent of one or more homopolymers or copolymers made from monomer components comprising aliphatic &agr;-olefins having from 2 to 20 carbon atoms, or aliphatic &agr;-olefins having from 2 to 20 carbon atoms and containing polar groups; and (2) a coupling amount of at least one poly(sulfonyl azide) to at least the decomposition temperature of the poly(sulfonyl azide) for a period sufficient for decomposition of at least about 80 weight percent of the poly(sulfonyl azide) and sufficient to result in a coupled polymer blend having less than about 2 weight percent gel. Preferably component (A) is a substantially random interpolymer made from styrene and ethylene, or styrene, ethylene and at least one other &agr;-olefin containing from 3 to 8 carbon atoms; and component (B) is a homopolymer made from ethylene or propylene, or a copolymer made from ethylene and/or propylene and at least other &agr;-olefin containing from 4 to 8 carbon atoms; or a terpolymer of ethylene, propylene and at least one of 4-methyl pentene, butene-1, hexene-1 or octene-1. The poly(sulfonyl azide) and blend preferably react at a temperature which is at least greater than the first temperature, at least the decomposition temperature of the poly(sulfonyl azide) and greater than about 150° C. More preferably the poly(sulfonyl azide) and blend are mixed at a first temperature which is at least the melting point of the lowest melting component of the blend and after mixing react at a second temperature which is at least greater than the first temperature, is at least the decomposition temperature of the poly(sulfonyl azide) and is greater than about 185° C.
Further, the invention includes any composition formed by a process of the invention, especially a composition comprising a reaction product obtainable by heating an admixture containing (1) a polymer blend containing:
(A) from 1 to 99 weight percent of one or more &agr;-olefin/hindered vinyl monomer substantially random interpolymers, each having been made from monomer components comprising:
(1) from 0.5 to 65 mole percent of either
(a) at least one vinyl aromatic monomer, or
(b) at least one hindered aliphatic vinyl monomer, or
Cummins Clark H.
Ho Thoi H.
Mullins Michael J.
Silvis H. Craig
Terbrueggen Robert H.
Lipman Bernard
The Dow Chemical Company
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