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
2000-02-16
2003-06-17
Mulcahy, Peter D. (Department: 1713)
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...
C524S430000, C524S437000
Reexamination Certificate
active
06579925
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to poly(arylene ether)-polystyrene compositions, and especially relates to poly(arylene ether)-polystyrene compositions having reduced dust formation during pelletizing.
In majority of cases, thermoplastics are processed via compounding and molding operations. A compounded formulation is often isolated in the form of granulate via pelletizing. Pelletizing is the operation during which a plastic string coming out of a die of a compounding machine (e.g., an extruder) is chopped via mechanical forces into granules. These granulation forces can cause the release of small pieces of material from the surface of the string, forming dust. Dust formation is an industrial issue not only during the pelletizing step but also during transportation and further processing such as feeding to a molding machine.
U.S. Pat. No. 5,199,184 to Rosse describes a method of handling plastic granules, especially polyester granules, in which the plastic granules are first crystallized then dried in a fluidized bed such that dust particles are removed from the granules, blown upward and deposited in a cyclone.
U.S. Pat. No. 5,296,563 to Gottschalk et al. describes a process of preparing thermoplastic molding materials whereby the poly(phenylene ether) component, initially present in pulverulent form, is subjected to compacting or sintering under pressure to decrease the proportion of free fine material.
The methods known in the art require special equipment achieve dust reduction. There continues to be a need for thermoplastic compositions that are inherently less susceptible to dust formation.
BRIEF SUMMARY OF THE INVENTION
Reduced dust formation is exhibited by a thermoplastic composition comprising: (a) about 20 to about 80 weight percent of a poly(arylene ether); (b) about 5 to about 80 weight percent of a polystyrene; (c) optionally, about 0.1 to about 15 weight percent of a rubber material; and (d) about 0.1 to about 5 weight percent of a metal hydroxide compound capable of releasing water during a compounding or molding step; wherein all weight percents are based on the weight of the entire composition.
DETAILED DESCRIPTION OF THE INVENTION
A thermoplastic composition exhibiting reduced dust formation comprises: (a) about 20 to about 80 weight percent of a poly(arylene ether); (b) about 5 to about 80 weight percent of a polystyrene; (c) about 0.1 to about 15 weight percent of a rubber material; and (d) about 0.1 to about 5 weight percent of a metal hydroxide compound capable of releasing water during a compounding or molding step; wherein all weight percents are based on the weight of the entire composition.
The composition comprises at least one poly(arylene ether) resin. Although all conventional poly(arylene ether)s can be employed with the present invention, polyphenylene ethers (“PPE”) are preferred. Poly(arylene ether)s per se, 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 (that is, alkyl containing from one to about seven 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 poly(arylene ether)s are included. The preferred homopolymers are those containing 2,6-dimethylphenylene ether units. Suitable copolymers include random copolymers containing, for example, such units in combination with 2,3,6-trimethyl-1,4-phenylene ether units or copolymers derived from copolymerization of 2,6-dimethylphenol with 2,3,6-trimethylphenol. Also included are poly(arylene ether)s containing moieties prepared by grafting vinyl monomers or polymers such as polystyrenes, as well as coupled poly(arylene ether)s 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 poly(arylene ether) chains to produce a higher molecular weight polymer. Poly(arylene ether)s of the present invention further include combinations of any of the above.
The poly(arylene ether)s generally have a number average molecular weight of about 3,000 to about 40,000 and a weight average molecular weight of about 20,000 to about 80,000, as determined by gel permeation chromatography. The poly(arylene ether) generally has an intrinsic viscosity of about 0.10 to about 0.60 deciliters per gram (dL/g), preferably about 0.29 to about 0.48 dL/g, all as measured in chloroform at 25° C. It is also possible to utilize a high intrinsic viscosity poly(arylene ether) and a low intrinsic viscosity poly(arylene ether) in combination. Determining an exact ratio, when two intrinsic viscosities are used, will depend somewhat on the exact intrinsic viscosities of the poly(arylene ether) used and the ultimate physical properties that are desired.
The poly(arylene ether) is typically prepared by the oxidative coupling of at least one monohydroxyaromatic compound such as 2,6-xylenol or 2,3,6-trimethylphenol. Catalyst systems are generally employed for such coupling; they typically contain at least one heavy metal compound such as a copper, manganese or cobalt compound, usually in combination with various other materials.
Particularly useful poly(arylene ether)s for many purposes are those which comprise molecules having at least one aminoalkyl-containing end group. The aminoalkyl radical is typically located in an ortho position to the hydroxy group. Products containing such end groups may be obtained by incorporating an appropriate primary or secondary monoamine such as di-n-butylamine or dimethylamine as one of the constituents of the oxidative coupling reaction mixture. Also frequently present are 4-hydroxybiphenyl end groups, typically obtained from reaction mixtures in which a by-product diphenoquinone is present, especially in a copper-halide-secondary or tertiary amine system. A substantial proportion of the polymer molecules, typically constituting as much as about 90 weight percent of the polymer, may contain at least one of said aminoalkyl-containing and 4-hydroxybiphenyl end groups.
It will be apparent to those skilled in the art from the foregoing that the poly(arylene ether)s include all those presently known, irrespective of variations in structural units or ancillary chemical features.
A suitable amount of poly(arylene ether) in the composition is about 20 to about 80 weight percent, with a preferred amount being about 20 to about 70 weight percent. An amount of about 30 to about 60 weight percent is more preferred.
The composition further comprises at least one polystyrene. The term “polystyrene” as used herein includes polymers prepared by methods known in the art including bulk, suspension and emulsion polymerization, which contain at least 25 weight percent of structural units derived from a monomer of the formula:
wherein R
1
is hydrogen, lower alkyl or halogen; Z
1
is vinyl, halogen or lower alkyl; and p is from 0 to 5. These resins include homopolymers of styrene, chlorostyrene and vinyltoluene; random copolymers of styrene with one or more monomers illustrated by acrylonitrile, butadiene, alpha-methylstyrene, ethylvinylbenzene, divinylbenzene and maleic anhydride; and rubber-modified polystyrenes comprising blends and grafts, wherein the rubber is a polybutadiene or a rubbery copolymer of about 70 to about 98 weight percent styrene and about 2 to about 30 weight percent diene monomer. Polystyrenes are known to be miscible with poly(arylene ether)s in all proportions, and the composition may contain polystyrene in an amount of about 20 to about 80 weight percent and more often about 20 to about 70 weight percent, based on the weight of the entire composition
Fortuyn Johannes E.
Kempers Torben Paul
Liska Juraj
General Electric Company
Mulcahy Peter D.
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