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
2000-04-13
2002-07-02
Short, Patricia A. (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...
C525S068000, C525S09200D, C525S132000, C525S133000, C525S391000, C525S397000
Reexamination Certificate
active
06414084
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to polyphenylene ether resins, and more particularly polyphenylene ether formulations with improved flow.
2. Brief Description of Related Art
Polyphenylene ether resins (PPE) are an extremely useful class of high performance engineering thermoplastics by reason of their hydrolytic stability, high dimensional stability, toughness, heat resistance and dielectric properties. They also exhibit high glass transition temperature values, typically in the range of 150° to 210° C., and good mechanical performance. This unique combination of properties renders polyphenylene ether based formulations suitable for a broad range of applications which are well known in the art. One example is injection molded products which are used for high heat applications. Polyphenylene ether polymers typically have relatively high molecular weights and possess high melt viscosity with intrinsic viscosity values typically greater than about 0.4 dl/g as measured in chloroform at 25° C.
One area in which polyphenylene ether based compositions have required an improvement is melt flow capability, i.e. the ability to flow freely at elevated temperatures during various processing stages such as extrusion and molding. Poor melt flow can impact the size and type of the part which can be prepared with the composition and influence the type of equipment in which the composition is processed. In U.S. Pat. No. 4,154,712 to G. Lee Jr. teaches that processability can be improved by decreasing the molecular weight of the polyphenylene ether polymers; however, lower molecular weight sometimes adversely affects other properties such as impact strength. To aid processing, polyphenylene ether resins are often prepared with flow promoters, such as polystyrene, saturated polyalicyclic resins and terpene phenol to reduce viscosity and impart high flow to the resulting composition. Polystyrene, terpene phenol and other such flow promoters reduce the heat deflection temperature (HDT) of the product and typically increase the flammability of the PPE resin, as measured under UL94 standard protocol.
Efforts to improve the flow characteristics of PPE resins with minimal or no loss of HDT values and impact other properties have been made. For example, U.S. Pat. No. 5,081,185 to Haaf et al. describes compositions comprising a blend of two or more polyphenylene ether resins with one resin having high intrinsic viscosity values of at least about 3.8 dl/g and the other having low intrinsic viscosity values of no greater than 0.33 dl/g. The blend of the two PPE resins exhibits higher melt flow with no substantial decrease in heat deflection temperature (HDT) when compared to the high intrinsic viscosity PPE resin of the blend. In addition, U.S. Pat. No. 5,376,724 to Bailey et al. discloses polyphenylene ether compositions which contain a resinous additive that improves flow with only minor reductions in HDT values and impact strength. The resinous additive is said to comprise vinyl aromatic monomers such as sytrene monomers or a hydrocarbon compound containing at least 35 wt % aromatic units.
It is desirable to provide a PPE resin formulation with high flow characteristics with reduced loadings of flow modifier to minimize the impact on HDT values, impact properties and flame retardance.
SUMMARY OF THE INVENTION
The present invention provides blends of polyphenylene ether resin, and dendritic polymers. It has been discovered that substantially equivalent improvements in the flow properties of compositions containing polyphenylene ether resins can be obtained with smaller amounts of dendritic polymers when compared to conventional flow modifying additives. The polyphenylene ether resin preferably has an intrinsic viscosity of at least about 0.35 dl/g, most often in the range of about 0.4-0.6 dl/g, as measured in chloroform at 25° C. This polyphenylene ether resin can comprise one or more different polyphenylene ether polymers. The dendritic polymers preferably have a melt viscosity in the range of 1 to 250 Pa at a temperature of 110° C. and shear rate of 30 sec
−1
. Preferably, the dendritic polymers are based on polyesters or polyolefins. The compositions of this invention preferably contain at most 15% by weight of the dendritic polymers. The weight ratio of polyphenylene ether resin to the dendritic polymer is preferably greater than 4:1.
The polyphenylene ether polymers of the polyphenylene ether resins used in compositions of the present invention are known polymers comprising a plurality of aryloxy repeating units preferably with at least 50 repeating units of Formula I
wherein in each of said units independently, each Q
1
is independently halogen, alkyl (preferably primary or secondary lower alkyl containing up to 7 carbon atoms), aryl (preferably phenyl), halohydrocarbon groups (preferably haloalkyl) having at least two carbons between the halogen atoms and the phenyl nucleus of Formula I, aminoalkyl, hydrocarbonoxy or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms and at least two carbon atoms separate the halogen atoms and the phenyl nucleus of Formula I.
Each Q
2
is independently hydrogen, halogen, alkyl (preferably primary or secondary lower alkyl up to 7 carbon atoms), aryl (preferably phenyl), halohydrocarbon (preferably haloalkyl) having at least two carbon atoms between the halogen atoms and the phenyl nucleus of Formula I, hydrocarbonoxy groups or halohydrocarbonoxy groups wherein at least two carbon atoms separate the halogen and oxygen atoms and at least two carbon atoms separate the halogen atoms from the phenyl nucleus of Formula I. Each Q
1
and Q
2
suitably contain up to about 12 carbon atoms and most often, each Q
1
is an alkyl or phenyl, especially C
1
-C
4
alkyl and each Q
2
is hydrogen.
The term “polyphenylene ether resin,” as used in the specification and claims herein, includes unsubstituted polyphenylene ether polymers, substituted polyphenylene ether polymers wherein the aromatic ring is substituted, polyphenylene ether copolymers and blends thereof. Also included are polyphenylene ether polymers containing moieties prepared by grafting onto the polyphenylene ether in a known manner such materials as vinyl monomers or polymers such a polystyrenes and elastomers, as described in U.S. Pat. No. 5,089,566 issued to S. Bruce Brown. Coupled polyphenylene ether polymers in which coupling agents such as low molecular weight polycarbonates, quinones, heterocycles and formals undergo reaction in the known manner with the hydroxy groups of two phenyl ether chains to produce a high molecular weight polymer are also included.
The polyphenylene ether polymers used in the compositions of this invention may also have various end groups such as amino alkyl containing end groups and 4-hydroxy biphenyl end groups, typically incorporated during synthesis by the oxidative coupling reaction. The polyphenylene ether polymers may be functionalized or “capped” with end groups which add further reactivity to the polymer and in some instances provide additional compatibility with other polymer systems which may be used in conjunction with the polyphenylene ether polymers to produce an alloy or blend. For instance, the polyphenylene ether polymer may be functionalized with an epoxy end group, a phosphate end group or ortho ester end group by reacting a functionalizing agent such as 2-chloro-4(2-diethylphosphato epoxy)6-(2,4,6-trimethyl-phenoxy)-1,3,5-trizene, with one of the end groups of the polyphenylene ether polymer, i.e., one of the terminal hydroxyl groups.
It will be apparent to those skilled in the art from the foregoing that the polyphenylene ether polymers contemplated for use in the present invention include all of those presently known, irrespective of the variations in structural units.
Specific polyphenylene ether polymers useful in the present invention include but are not limited to
poly(2,6-dimethyl-1,4-phenylene ether);
poly(2,3,6-trimethyl-1,4-phenylene)ether;
poly(2,6-diethyl-1,4-ph
General Electric Company
Short Patricia A.
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