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
1999-01-25
2001-03-27
Woodward, Ana (Department: 1711)
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...
C525S133000, C525S179000
Reexamination Certificate
active
06207745
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to flame retardant polyamide compositions. More particularly, this invention relates to flame retardant polyamide compositions which have excellent anti-drip characteristics when exposed to flames.
The trend toward integration of electronic components has led to an increasing need for plastic materials having much greater heat resistance and flame retardant properties, particularly for use in connectors, circuit boards, semiconductor packages and the like. Where such devices are used continuously, or are used in demanding environments, they may encounter extremely high temperatures. Further improvements in heat resistance and flame retardant properties for such materials are thus continually being sought by the industry.
Partially aromatic polyamides, typified by polymers comprising hexamethylene diamine terephthalamide units, have excellent mechanical strength, rigidity, heat resistance and moisture resistance. These polyamides are finding wide acceptance for use as engineering plastics, particularly in applications where elevated temperatures and severe environments may be encountered, for example, in electrical appliance parts, in connectors and similar parts for electrical and electronic devices and in a variety of automotive applications. Filled compositions comprising such polyamides in combination with reinforcing fillers such as glass fibers are also useful where further improvement in heat resistance and rigidity is required.
Like most other thermoplastic resins, polyamides are subject to burning. When the polyamide is to be used in applications requiring self-extinguishing characteristics and flame retardant properties it is necessary to resort to the addition of a fire retardant. Halogen-containing organic compounds such as a halogenated polystyrene, polydibromostyrene, or a condensation product of brominated phenol to polyamides have been used to impart fire-retarding properties in certain polyamide fomulations. Antimony compounds are also used in combination with the halogen-containing organic compounds to improve flame retarding properties.
In addition to flame retarding for some polyamide applications, it is required that the polyamide composition, when exposed to a flame, have a reduced tendency to drip. A dripping polymer is a hazard and technology has been developed to reduce the dripping by adding a PTFE additive. However, PTFE when used in a polyamide formulation can agglomerate and cause problems in the molding process used to make molded parts from the polyamide composition. The art, therefore, needs a polyamide composition that is flame retardant, has good anti-drip properties and does not agglomerate. This invention provides for such polyamide composition.
SUMMARY OF THE INVENTION
This invention is a flame-retardant, anti-dripping polyamide composition comprising a polyamide, a halogen-containing organic compound, and an anti-drip effective amount of an anti-drip component comprising a polymer formed from at least one ethylenically unsaturated monomer and at least one carboxylic acid containing monomer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The improved flame-retardant, anti-drip polyamide compositions of this invention comprise a polyamide, preferably a high temperature polyamide, and more preferably a fiber-filled high temperature polyamide, flame retarded with a halogen-containing flame retardant compound together with a low level of an anti-drip polymer comprising a polymer formed from at least one ethylenically unsaturated monomer and at least one carboxylic acid containing momomer. The improved flame retarded polyamide composition of this invention will preferably be a glass fiber-filled partially aromatic polyamide containing an organic, bromine-containing flame retardant. The anti-drip properties of the composition of this invention are provided by adding thereto an anti-drip effective amount of the anti-drip polymer to the composition. By partially aromatic polyamide is meant a polymer containing units derived from one or more aliphatic diamines and one or more aromatic dicarboxylic acids, including copolymers containing such units.
Although any polyamide can be used in the practice of this invention such as nylon 6,6 or nylon 4,6, the preferred polyamides suitable for use in the practice of this invention include the various linear, thermoplastic, high temperature, partially aromatic polyamides and copolymer analogs thereof, frequently termed partially aromatic nylons. Polyamides that are crystalline or crystallizable are preferred, and particularly preferred are the crystalline or semi-crystalline, high temperature copolyamides comprising terephthalamides of aliphatic diamines. Such copolyamides will comprise as structural units terephthalamides of one or more C
4
-C
14
aliphatic diamines such as hexamethylene diamine or the like, including diamines having one or more C
1
-C
4
alkyl substituents attached to the hydrocarbon portion. In addition to the terephthalamide units, these copolyamides may further comprise as structural units one or more additional diamides of such aliphatic diamines, for example, diamides derived from aromatic dicarboxylic acids or related compounds such as isophthalic acid, naphthalene dicarboxylic acid or the like, as well as diamides derived from aliphatic diamines and C
4
-C
14
aliphatic dicarboxylic acids or related compounds such as diamide units derived from adipic acid, sebacic acid, cyclohexane dicarboxylic acid and similar dicarboxylic acids.
A variety of polyamides comprising terephthalamide units are known in the art including, for example, copolyamides comprising a combination of hexamethylene terephthalamide units and hexamethylene adipamide units, optionally including hexamethylene isophthalamide units. Particularly suitable for use in the practice of this invention are copolyamides comprising at least 50 mole % hexamethylene terephthalamide units, the balance being hexamethylene adipamide units, either alone or in combination with up to about 30 mole % hexamethylene isophthalamide units. Further examples of polyamides that may be suitable for these purposes are the well known crystallizable polyamides comprising terephthalamides of two or more diamines such as hexamethylene diamine and 2-methyl-pentamethylene diamine.
In greater detail, the polyamide component of the invented compositions may be a crystallizable polyamide comprising at least about 40 mole %, preferably from about 40 to about 100 mole %, recurring aliphatic diamine terephthalamide units which may be further described as represented by the following structural formula:
wherein R comprises at least one aliphatic hydrocarbyl radical.
Preferably, aliphatic radicals R in the above formula will comprise at least one straight chain, branched or cyclic, substituted or unsubstituted aliphatic radical having from about 4 to bout 14 carbon atoms. Polyamides comprising such radicals exhibit good crystallinity and desirable high temperature properties, together with melting and thermal degradation temperatures making them well suited for melt processing and fabricating in injection molding and extrusion operations. Specific examples of suitable aliphatic radicals include tetramethylene, hexamethylene, dodecamethylene and the like, as well as their alkyl-substituted analogs such as 2-methylpentamethylene, 2,4-dimethylhexamethylene and the like, and cyclic analogs such as p-cyclohexyl and the like. Most preferably, R in the formula comprises a hexamethylene radical, either alone or as mixture with additional aliphatic 4 to 14 carbon atom radicals. The preferred polyamide components will have a melting point of at least about 270° C. as a result of the high content of terephthalamide units; still more preferred are polyamide components melting at about 290° C. to about 330° C.
The preferred polyamides may be more particularly described as crystallizable or semi-crystalline partially aromatic polyamides of fast or intermediate crystallization rate comprising recurring units corresponding
Bersted Bruce H.
Reichmann Mark G.
BP Amoco Corporation
Nemo Thomas E.
Schlott Richard J.
Woodward Ana
LandOfFree
Flame retardant anti-drip polyamide compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flame retardant anti-drip polyamide compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flame retardant anti-drip polyamide compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2444946