Capping of polyphenylene ether resin

Details Capping of polyphenylene ether resin Capping of polyphenylene ether resin

1999-02-05

2001-10-23

Buttner, David J. (Department: 1712)

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

active

06306978

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
FEDERALLY SPONSORED RESEARCH
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to methods of capping poly(phenylene ether) resin, and more particularly relates to methods of capping poly(phenylene ether) resin having an intrinsic viscosity between 0.05 and 0.35 dl/g, preferably between about 0.09 and 0.15 dl/g.
2. Brief Description of the Related Art
Poly(phenylene ether) resins (referred to hereafter as “PPE”) are commercially attractive materials because of their unique combination of physical, chemical, and electrical properties. Commercially, most PPE are sold as blends with predominantly high impact polystyrene resins. PPE are miscible with polystyrene resins in all proportions and because of the very high glass transition temperatures of PPE, the blends of PPE with polystyrene resins possess higher heat resistance than that of the polystyrene resins alone. Examples of such blends can be found in U.S. Pat. Nos. 3,383,435; 4,097,550; 4,113,800; 4,101,503, 4,101,504; 4,101,505; 4,128,602; 4,139,574; and 4,154,712 among others.
Many commercial poly(phenylene ether) resins posses end groups having an aromatic hydroxyl moiety, generally an alkyl substituted phenol residue. These residues are believed to act as radical scavengers and consequently limit the utility of poly(phenylene ether) resins in applications involving desirable radical reactions. One example of a desirable application is the polymerization of styrene monomer, either alone or with comonomers, in the presence of poly(phenylene ether) resin. Similarly, poly(phenylene ether) resins become dark and embrittled in the presence of oxygen and high temperatures, presumably due to oxidation of these same hydroxyl groups. Capping the hydroxyl moieties present in PPE affords a solution to many of these problems. Moreover, capped PPE would also have utility in many PPE blends such as, for example, blends with other thermoplastic polymers as well as thermoset resins including unsaturated polyurethane resins, allylics, bismaleimides, and the like.
U.S. Pat. No. 4,760,118 describes a method to cap poly(phenylene ether) resins in a melt (i.e. solventless) process. The method described in the aforementioned patent was exemplified using a poly(phenylene ether) resin having an intrinsic viscosity of about 0.48 dl/g and afforded solutions to issues for capping relatively high molecular weight poly(phenylene ether) resin.
Recently, interest has increased in poly(phenylene ether) resins having an intrinsic viscosity between 0.05 and 0.35 dl/g due, in part, to their increased processability and miscibility as compared to commercially available resins having intrinsic viscosities between 0.40 and 0.49 dl/g. With the reduced intrinsic viscosity the number of endgroups increases and aforementioned problems become accentuated.
Capping poly(phenylene ether) resin relatively low molecular weight poly(phenylene ether) resin, e.g., having an intrinsic viscosity between 0.05 and 0.35 dl/g, presents issues that were not previously recognized. For example, relatively low molecular weight poly(phenylene ether) resin has a significantly higher proportion of hydroxyl moieties for capping. Similarly, relatively low molecular weight poly(phenylene ether) resin can not be efficiently isolated after polymerization using conventional solvent precipitation techniques due to the extremely small particle size generated with conventional techniques. The low melt strength of relatively low molecular weight poly(phenylene ether) resin also presents special issues, especially with stranding and chopping the extrudate.
It is therefore apparent that there continues to be a need for improved methods for capping relatively low molecular weight poly(phenylene ether) resin.
SUMMARY OF THE INVENTION
The invention relates to methods of capping poly(phenylene ether) resin having an intrinsic viscosity between 0.05 and 0.35 dl/g, preferably between about 0.09 and 0.15 dl/g. More particularly, the methods comprise capping a poly(phenylene ether) resin having an intrinsic viscosity between 0.05 and 0.35 dl/g, preferably between about 0.09 and 0.15 dl/g, in a solvent to produce a capped poly(phenylene ether) resin having an intrinsic viscosity between 0.05 and 0.35 dl/g,, preferably between about 0.09 and 0.15 dl/g, and isolating the capped poly(phenylene ether) resin by removal of the solvent, preferably in a process other than precipitation. The invention also relates to the capped poly(phenylene ether) resin having an intrinsic viscosity between 0.05 and 0.35 dl/g, preferably between about 0.09 and 0.15 dl/g. These and other embodiments of the invention will become apparent as described herein.
DESCRIPTION OF THE DRAWINGS
Not applicable
DETAILED DESCRIPTION OF THE INVENTION
Poly(phenylene ether) resins, hereinafter referred to as “PPE” are known polymers comprising a plurality of structural units of the formula:
wherein for each structural unit, each Q
1
is independently halogen, primary or secondary lower alkyl (e.g., alkyl containing up to 7 carbon atoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Q
2
is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl, hydrocarbonoxy or halohydrocarbonoxy as defined for Q
1
. Preferably, each Q
1
is alkyl or phenyl, especially C
1-4
alkyl, and each Q
2
is hydrogen.
Both homopolymer and copolymer PPE are known and included in the present invention. The preferred homopolymers are those containing 2,6-dimethyl-1,4-phenylene ether units. Suitable copolymers include random copolymers containing, for example, such units in combination with 2,3,6-trimethyl-1,4-phenylene ether units. Also included are PPE containing moieties prepared by grafting vinyl monomers or polymers such as polystyrenes, as well as coupled PPE in which coupling agents such as low molecular weight polycarbonates, quinones, heterocycles and formals undergo reaction in known manner with the hydroxy groups of two PPE chains albeit to produce a higher molecular weight polymer.
It will be apparent to those skilled in the art from the foregoing that the PE contemplated for use in the present invention include all those presently known, irrespective of variations in structural units or ancillary chemical features.
The PPE generally have an intrinsic viscosity often between about 0.05-35 dl./g., preferably in the range of about 0.07-0.25 dl./g., and most referably in the range of about 0.09-0.15 dl./g., all as measured in hloroform at 25° C. It is also possible to utilize a higher intrinsic viscosity PPE outside these ranges in combination with a lower intrinsic viscosity PPE within these ranges. Determining an exact intrinsic viscosity to be used will depend somewhat on the ultimate physical properties that are desired.
PPE are typically prepared by the oxidative coupling of at least one corresponding monohydroxyaromatic compound. Particularly useful and readily available monohydroxyaromatic compounds are 2,6-xylenol (wherein each Q
1
is methyl and each Q
2
is hydrogen), whereupon the polymer may be characterized as a poly(2,6-dimethyl-1,4phenylene ether), and 2,3,6-trimethylphenol (wherein each Q
1
and one Q
2
is methyl and the other Q
2
is hydrogen).
A variety of catalyst systems are known for the preparation of PPE by oxidative coupling. For the most part, they contain at least one heavy metal compound such as a copper, manganese or cobalt compound, usually in combination with various other materials.
A first class of operative catalyst systems consists of those containing a copper compound. Such catalysts are disclosed, for example, in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,914,266 and 4,028,341. They are usually combinations of cuprous or cupric ions, halide (i.e. chloride, bromide, or iodide) ions and at least one amine.
Catalyst systems containing manganese compounds are also known. They are generally alkaline systems i

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