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
2003-05-01
2004-06-01
Niland, Patrick D. (Department: 1714)
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...
C521S056000, C521S060000, C521S139000, C521S180000, C524S136000, C524S502000
Reexamination Certificate
active
06743846
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
This invention relates to the field of expandable poly(arylene ether)/polystyrene compositions and more particularly to the field of flame retardant expandable poly(arylene ether)/polystyrene compositions.
Increasingly plastics are being used to replace metals in a wide variety of applications ranging from car exteriors to aircraft interiors. Flame retardant plastics have been especially useful, particularly in applications such as housings for electronic devices. The use of plastic instead of metal decreases weight, improves sound dampening and makes assembly of the device easier. Flame resistance has been dominantly provided by halogenated flame retardants. However, plastics employing halogenated flame retardants release toxic gas when heated to elevated temperatures and produce non recyclable waste streams. As a result non-halogenated fire resistant materials are in demand for a wide range of applications.
The most widely used process for making expandable poly(arylene ether)/polystyrene is via the styrene suspension polymerization process. Terminally end capped poly(arylene ether) resin is dissolved in the styrene monomer prior to polymerization and polymerization proceeds by the suspension process. During or at the end of polymerization a blowing agent is added. At the end of the process poly(arylene ether)/polystyrene expandable beads are recovered. Terminally endcapped poly(arylene ether) resin is required so the poly(arylene ether) resin does not inhibit the polymerization of the styrene. Unfortunately, the capping agent introduces by products and interferes with polymerization, resulting in low yield. Additionally, the poly(arylene ether) resin has limited solubility in the monostyrene, restricting the amount of poly(arylene ether) resin that can be added to the blend. This, in turn, limits the high temperature properties of the resulting poly(arylene ether)/polystyrene materials. The high viscosity of the composition limits the amount of additives, such as flame retardants and impact modifiers that can be included. Furthermore, only halogenated flame retardants may be used. Thus the styrene polymerization process for making expandable poly(arylene ether)/polystrene has several drawbacks including limited poly(arylene ether) resin solubility, modified poly(arylene ether) resin is required, a halogenated flame retardant is required, and high viscosity. These drawbacks limit the potential to manufacture expandable poly(arylene ether)/polystyrene materials with advanced properties through the suspension process.
BRIEF SUMMARY OF THE INVENTION
Non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blends are produced by the method comprising, in a first step, forming a fire retardant mixture comprising a non-halogenated fire retardant, poly(arylene ether) resin and polystyrene resin by intimately mixing in melt; and in a second step, forming the non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blend by intimately mixing in melt the fire retardant mixture with a blowing agent.
The above discussed and other features and advantages will be appreciated and understood by those skilled in the art from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
Not Applicable
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blend is produced by the method comprising, in a first step, forming a fire retardant mixture comprising a non-halogenated fire retardant, poly(arylene ether) resin polystyrene resin and optional impact modifier by intimately mixing in melt; and, in a second step, forming the non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blend by intimately mixing in melt the fire retardant mixture with a blowing agent. Preferably the first step is performed in a first extruder and the second step is performed in a tandem extruder comprising extruder A and extruder B. Intimate mixing of the fire retardant mixture and blowing agent to form a non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blend occurs in extruder A of the tandem extruder and cooling of the non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blend occurs in extruder B of the tandem extruder. Cooling of the non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blend prevents premature foaming of the blend at the die.
The non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blends exhibit excellent molding performance and excellent fire retardant properties at various thicknesses while maintaining desirable heat dimensional stability. Surprisingly, the non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blends exhibit better fire retardant properties, namely short flame out time and non flaming drip behavior, than conventional halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blends. The non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blends can achieve an HBF rating or better in the UL ASTM D 4986/ISO/DIS 9772.3 flammability test, something not previously seen in an expandable poly(arylene ether)/polystyrene blend. The excellent fire retardant properties are unexpected and are believed to be the result of the thorough distribution of the non-halogenated fire retardant throughout the expandable poly(arylene ether)/polystyrene blend. The non-halogenated, fire retardant, expandable poly (arylene ether)/polystyrene blends do not require specially end capped poly(arylene ether) resin, have on line processability, can be colored to a wide range of colors and have a wide range of thermal properties.
An additional advantage of the method to produce poly(arylene ether)/polystyrene blends herein described is the ability to incorporate significantly larger amounts of poly(arylene ether) into the blend than currently possible using the suspension polymerization process. As previously mentioned poly(arylene ether) has limited solubility in mono styrene thus restricting the amount of poly(arylene ether) present in a poly(arylene ether)/polystyrene blend produced by suspension polymerization. In contrast, the method herein described can incorporate about 25 weight percent (wt %) of poly(arylene ether) or greater, preferably about 40 wt % or greater or even more preferably about 50 wt % or greater, based on the weight of the composition.
All conventional poly(arylene ether)s can be employed. The term poly(arylene ether) includes polyphenylene ether (PPE) and poly(arylene ether) copolymers; graft copolymers; poly(arylene ether) ether ionomers; and block copolymers of alkenyl aromatic compounds, vinyl aromatic compounds, and poly(arylene ether), and the like; and combinations comprising at least one of the foregoing; and the like. Poly(arylene ether)s per se, are known polymers comprising a plurality of structural units of the formula (I):
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, halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms, or the like; and each Q
2
is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl, hydrocarbonoxy, halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms, or the like. 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) 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
Keulen Jan
Landa Adrie
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