Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-07
2002-03-26
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S268000, C524S500000, C524S538000, C524S540000, C525S393000, C525S397000, C525S401000, C525S426000, C525S431000
Reexamination Certificate
active
06362263
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to compositions of impact modified, compatibilized poly(phenylene ether)-polyamide resin blends containing either a polybutene or an organosiloxane mixture. The invention also relates to methods to prepare said compositions and articles formed from the compositions.
Poly(phenylene ether)-polyamide blends may possess properties which are a combination of the beneficial properties of both resins. These include high thermal stability afforded by poly(phenylene ether)s and solvent resistance afforded by polyamides.
For the preparation of blends other than those containing a minimum proportion of one resin, the presence of a compatibilizing agent is necessary since the two polymers are otherwise incompatible. Examples of compatibilized poly(phenylene ether)-polyamide blends can be found in U.S. Pat. No. 4,315,086 (Ueno, et al.); U.S. Pat. No. 4,659,760 (van der Meer); and U.S. Pat. No. 4,732,938 (Grant, et al.). In the absence of compatibilization, morphological examination of poly(phenylene ether)-polyamide blends typically shows a continuous polyamide phase with poly(phenylene ether) forming a second phase poorly dispersed therein, often resulting on a macroscopic scale in the formation of laminar structures with poor physical properties.
At least one impact modifier is usually also present in typical poly(phenylene ether)-polyamide compositions. Suitable impact modifiers include those compatible with polyamides and especially those compatible with poly(phenylene ether)s. The properties of these blends can be further enhanced by the addition of various additives such as light stabilizers, flame retardants, heat stabilizers, antioxidants and fillers.
The physical properties of poly(phenylene ether)-polyamide blends make them attractive for a variety of end-use articles in the automotive market, especially for under-hood and various exterior components. Additional applications in other markets have been somewhat limited by the lack of low temperature impact strength in these blends. The blends must also have outstanding ductility, flow and surface appearance. It is therefore apparent that a need continues to exist for poly(phenylene ether)-polyamide compositions with improved low temperature impact strength in combination with other attractive physical properties.
Poly(diorganosiloxane)s or polybutenes might provide low temperature impact strength due to their low Tg (for example about −129° C. for poly(dimethylsiloxane) and less than about −60° C. for a typical polybutene). In addition, poly(diorganosiloxane)s may also provide superior weatherability, high flow and improved flame retardance as compared to other additives such as butadiene-based rubbers. However, poly(diorganosiloxane)s are immiscible with most thermoplastics. In order to obtain optimum blend physical properties poly(diorganosiloxane)s typically require compatibilization when they are included as blend components. Conventional routes to using poly(diorganosiloxane)s involve their addition to blends in the form of copolymers like block copolymers, core-shell copolymers or graft copolymers with other thermoplastics that are compatible with one or more other polymers in the blend. The copolymer approach also helps in controlling the particle size of the poly(diorganosiloxane)-containing phase which may be critical for tailoring the impact performance of the blend. While these approaches are viable, the added cost of preparing block, core-shell, or graft copolymers from poly(diorganosiloxane)s makes them unpractical.
The use of poly(diorganosiloxane)-containing powders without pre-forming copolymers and without added compatibilizing agent has been reported for improving the flame resistance of thermoplastics. The powders may be prepared by dispersing high molecular weight silicone gums with a filler using methods taught in, for example, U.S. Pat. Nos. 3,824,208 and 5,153,238, which claim that the powders have storage stability and are gel free. U.S. Pat. No. 5,153,238 recommends preparing the powder by mixing in a high intensity mixer at temperatures varying from 100° C. to 200° C. U.S. Pat. Nos. 5,391,594 and 5,508,323 are directed to methods for using poly(diorganosiloxane)-containing powders for improving the burn character of thermoplastic resins, such as poly(phenylene ether) or polyamide, that results in improvements in the rate of smoke release, generation of smoke and evolution of toxic carbon monoxide. U.S. Pat. No. 5,412,014 is directed to the use of a phosphorus flame retardant as a synergist in conjunction with poly(diorganosiloxane)-containing powders for improving the flame retardance of thermoplastic resins. Further, Buch, et al. (“Silicone-Based Additives for Thermoplastic Resins Providing Improved Fire Properties Such as Reduced Heat Release Rate, Reduced Toxic Gases and Smoke as Measured by the Cone Calorimeter”, Dow Coming Corp., Fire Retardant Chem. Assoc., Oct. 26-29, 1993, pp. 1-15) report the use of poly(diorganosiloxane)-containing resin modifier products termed RM 4-7081 and RM 4-7051 for improving the flame retardance of organic resins. That paper also discloses the improvements in impact performance of engineering resins such as poly(phenylene ether) in the absence of other added impact modifiers.
The use of powders prepared from poly(diorganosiloxane)-containing gums containing epoxy and carboxyl functionalities for improving the impact performance of polyamide resins is the subject of U.S. Pat. No. 5,610,223. The polyamide-based blends rely on the reactive epoxy or ester functionalities on the gums to effect a compatibilization reaction with amino or acid end-groups on the polyamide resins. This type of approach depends on the commercial availability of pre-functionalized poly(diorganosiloxane) gums and is limited by the functionality concentrations available on these gums. Moreover, the copolymer-forming compatibilizing reaction between the thermoplastic resin and the functionalized gum may be limited by the mobility of the siloxane chain as the molecular weight of the poly(diorganosiloxane)-containing gum increases.
French patent application FR 2,640,632, assigned to Rhône-Poulenc Chimie, is directed to a method for compatibilizing a poly(diorganosiloxane) with polyester or polyamide said to have improved impact resistance and surface qualities. The thermoplastic resin is blended with a non-reactive poly(diorganosiloxane) gum and a mono- or bi-functional poly(diorganosiloxane) oil. The poly(diorganosiloxane) gum is described as being a high viscosity linear polymer with a molecular weight greater than 300,000 g/mol. In a preferred embodiment, the gum contains 100-1000 ppm vinyl groups. The functionalized poly(diorganosiloxane) oil reacts with polyamide or polyester end-groups to provide a copolymer compatibilizing agent.
U.S. patent application Ser. No. 09/293,915, filed Apr. 19, 1999 now abandoned discloses a method for improving the physical properties of thermoplastic molding compositions. A polyester and/or polyamide is blended with a poly(diorganosiloxane)-containing impact modifier and an epoxy- or orthoester-functionalized compound. The epoxy- or orthoester-functionalized compound is the compatibilizing agent for the polyester and/or polyamide blend and impact modifier. The impact modifier may contain at least one of several silicone-containing components such as a poly(diorganosiloxane) compound, an inorganic filler, and optionally, a silicone additive. The silicone-containing component combined with the compatibilizing agent yields a blend product with high impact strength.
The compounds of the patents described above all provide to some degree a polymer blend composition with certain properties improved, but there still remains a need for compatibilized poly(phenylene ether)-polyamide blends which can be molded to form high-quality parts which display excellent impact strength, and specifically, exceptional notched Izod impact strength at low temperature, while retaining other key physical properties such as flow and
Brown Sterling Bruce
Giammattei Mark Howard
Khouri Farid Fouad
Silvi Norberto
Singh Navjot
Brown S. Bruce
Dawson Robert
Johnson Noreen C.
Zimmer Marc S.
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