Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-10-27
2001-09-18
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S275000, C526S276000, C525S538000, C524S138000, C524S139000, C524S708000, C528S168000
Reexamination Certificate
active
06291618
ABSTRACT:
This invention relates to coupling agents and their use in coupling of polymer chains, more particularly to the coupling of polymer chains with phosphazene azides.
BACKGROUND
Polymers have been reacted with various polyfunctional compounds capable of insertion reactions into C—H bonds. Such polyfunctional compounds having at least two functional groups capable of C—H insertion reactions are referred to herein as C—H insertion compounds. Those skilled in the art are familiar with such reactions and the functional groups associated therewith. For example, carbenes, as generated from diazo compounds, are disclosed in
Tetrahedron
, (1985), 41(8), pages 1509-1516, and nitrenes, as generated from azides, are disclosed in
J. Org. Chem.
, (1977), 42(17), 2920-6, and
J. Org. Chem.
, (1975), 40(7), 883-9. C—H insertion compounds include compounds such as alkyl and aryl azides (R—N3), acyl azides (R—C(O)N3), azidoformates (R—O—C(O)—N3), phosphoryl azides ((RO)2-(PO)—N3), phosphinic azides (R2-P(O)—N3), silyl azides (R3—Si-N3) and sulfonyl azides (R—SO2-N3).
Sulfonyl azides are reported to be useful for a variety of purposes including polymer crosslinking. U.S. Pat. Nos. 3,058,944; 3,336,268; and 3,530,108 disclose the reaction of certain poly(sulfonyl azide) compounds with isotactic polypropylene and other polyolefins by nitrene insertion into C—H bonds. More recently, sulfonyl azides have been found useful in modifying the rheology of certain polyolefins as disclosed in U.S. application Ser. Nos. 60/057,713 and 60/057,677, filed on Aug. 27, 1997; U.S. application Ser. Nos. 09/129,163, 09/129,161 and 09/129155 file on Aug. 5, 1998; U.S. application Ser. No. 09/140,603 fled on Aug. 26, 1998 and U.S. application Ser. No. 09/133,244 filed on Aug. 13, 1998; each of which is hereby incorporated herein by reference in its entirety. The result of reacting a sulfonyl azide with a polyolefin is the coupling of one polymer chain to another via a sulfonamide linkage. When polymer chains are thus coupled or linked, they are referred to as coupled or chain coupled polymers, and as rheology modified polymers.
As used herein, the term “rheology modified” refers to a change in the resistance of the molten polymer to flow. The resistance to flow is indicated by (1) the tensile stress growth coefficient and (2) the dynamic shear viscosity coefficient. The tensile stress growth coefficient is measured during start-up of uniaxial extensional flow as described by J. Meissner in Proc. XIIth International Congress on Rheology, Quebec, Canada, August 1996, pages 7-10 and by J. Meissner and J. Hostettler, Rheol. Acta, 33, 1-21 (1994). The dynamic shear viscosity coefficient is measured with small-amplitude sinusoidal shear flow experiments as described by R. Hingmann and B. L. Marczinke, J. Rheol. 38(3), 573-87, 1994.
Polymer compositions have also been rheology modified using nonselective chemistries involving free radicals generated by peroxides or high energy radiation. Although these techniques are useful for polyethylene, free radical generation at elevated temperatures tend to degrade the molecular weight of polymers such as polypropylene and polystyrene, due to the high rate of chain scission reactions along the polymer backbone.
Therefore, previous coupling technologies have been ineffective at high temperatures, e.g.>250° C., due to the formation of undesirable amounts of free radicals and/or decomposition. There remains a need for successful coupling of polymers which are typically processed at temperatures above 250° C., without degradation or crosslinking of the polymer.
SUMMARY OF THE INVENTION
The present invention is directed to a process for preparing a coupled or rheology modified polymer comprising contacting a polymer with a cyclic phosphazene azide at a temperature which is at least the decomposition temperature of the cyclic phosphazene azide, typically at temperatures above 200° C. Other aspects of the present invention are directed to a composition comprising a rheology modified polymer prepared by coupling the polymer using a cyclic phosphazene azide, blends thereof, and articles produced therefrom.
This process utilizing cyclic phosphazene azides allows for high temperature coupling of polymer chains without significant crosslinking or polymer degradation.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a process for producing a rheology modified polymer comprising contacting a polymer with a cyclic phosphazene azide at a temperature which is at least the decomposition temperature of the cyclic phosphazene azide. When the cyclic phosphazene azide reacts with the polymer, at least two separate polymer chains are advantageously joined and the molecular weight of the polymer chain is increased. In the preferred case when the cyclic phosphazene azide has only two azide groups, two distinct polymer chains are advantageously joined.
Cyclic phosphazene azide compounds useful for the process of the present invention include azides of the formula P
3
N
3
(R)
n
(N
3
)
6−n
, wherein n is an integer from 2 to 4, and R is a C
1
to C
20
alkoxy, a C
6
to C
20
phenoxy, a C
2
to C
20
dialkylamine, or a C
12
to C
20
diarylamine, any of which can be additionally substituted with additional functional groups which do not interfere with the ability of the azide to act as a polymer coupling agent. Such substituents include but are not limited to a halo, nitro, amino, cyano, carbonyl or carboxyl functional group. In a specific preferred embodiment, R is an unsubstituted phenoxy group. Preferably n is 2, more preferably 3 and most preferably 4.
Cyclic phosphazene azides can be conveniently prepared by the reaction of sodium azide with the corresponding chloro-organocyclophosphazene in the presence of a catalytic amount of tetrabutylammonium bromide, in a refluxing solvent such as 2-butanone, toluene or THF, as described in “Synthesis and Reactivity of Alkoxy, Aryloxy, and Dialkylamino Phosphazene Azides,
J. Am. Chem. Soc.
1999, 121, 884-885.
A polymer to be coupled utilizing the process of the present invention is advantageously a thermoplastic polymer, which has at least one C—H bond that can react with an azide. Such polymers include homopolymers or copolymers having narrow or broad (including bimodal) comonomer distribution as well as narrow or broad (including bimodal) molecular weight distribution, which is either a semi-crystalline hydrocarbon polymer having a melting point greater than 200° C., or an amorphous hydrocarbon polymer having a glass transition temperature of greater than 150° C. These polymers are normally processed at temperatures of from 200 to 400° C. without incurring any significant change in polymer chemical structure or weight average molecular weight (Mw).
In one preferred embodiment, the polymer is a syndiotactic vinyl aromatic polymer. As used herein, the term “syndiotactic” refers to polymers having a stereoregular structure of greater than 90 percent syndiotactic, preferably greater than 95 percent syndiotactic, of a racemic triad as determined by 13C nuclear magnetic resonance spectroscopy.
Syndiotactic vinyl aromatic polymers are homopolymers and copolymers of vinyl aromatic monomers, that is, monomers whose chemical structure possess both an unsaturated moiety and an aromatic moiety. The preferred vinyl aromatic monomers have the formula
H2C═CR—Ar;
wherein R is hydrogen or an alkyl group having from 1 to 4 carbon atoms, and Ar is an aromatic radical of from 6 to 10 carbon atoms. Examples of such vinyl aromatic monomers are styrene, alpha-methylstyrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyl toluene, para-t-butylstyrene, vinyl naphthalene, divinylbenzene and the like. syndiotactic polystyrene is the currently preferred syndiotactic vinyl aromatic polymer. Typical polymerization processes for producing syndiotactic vinyl aromatic polymers are well known in the art and are described in U.S. Pat. Nos. 4,680,353, 5,066,741, 5,206,197 and 5,294,685, which are incorporated herein by reference.
In another preferred
McIntosh Michael B.
Silvis H. Craig
Asinovsky Olga
Seidleck James J.
The Dow Chemical Company
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