Flame retardant high temperature polyphthalamides having improved thermal stability

The thermal stability of flame retardant, high temperature polyamides containing an organohalogen flame-retardant such as brominated polystyrene in combination with an antimony compound such as sodium antimonate during molding and similar melt fabrication operations is markedly improved when further combined with a minor amount of calcium oxide. The thermal stability of these compositions are much improved over analogous flame retardant polyamides formulated with magnesium oxide and/or zinc oxide.

This application claims the benefit of U.S. provisional application No. 
60/017,615, filed May 14, 1996. 
BACKGROUND OF THE INVENTION 
This invention is directed to a flame retardant high temperature polyamide 
composition having good heat resistance, and more particularly to a 
fire-retardant high temperature polyamide composition having markedly 
improved thermal stability, particularly during molding or other melt 
fabrication and to a method for improving the thermal stability of flame 
retardant high temperature polyamide formulations. 
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 circuit boards, 
semiconductor packages and the like. Particularly where such devices are 
used continuously they may encounter extremely high temperatures, and 
hence further improvements in heat resistance and flame retardant 
properties are continually 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, including for example electrical appliance parts, connectors 
and similar parts for electrical and electronic devices and in a variety 
of automotive applications. Where further improvement in heat resistance 
and rigidity is required, filled compositions comprising such polyamides 
in combination with reinforcing fillers such as glass fibers may also be 
useful. Polyamides composed of aromatic dicarboxylic acids such as 
terephthalic acid and aliphatic alkylenediamines have long been known, as 
shown, for example in U.S. Patent RE 34,444. These polyamides have 
excellent mechanical strength, rigidity and moisture and heat resistance, 
and are particularly desirable in these applications. 
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. 
Adding halogen-containing organic compounds such as a halogenated 
polystyrene or a condensation product of brominated phenol to 
thermoplastics for fire-retarding purposes is known in the art. Additional 
components, particularly antimony-containing compounds, are widely used in 
combination with halogen-containing organic compounds, and particularly 
with bromine-containing flame retardants as an aid to further enhance 
their effectiveness. These flame retardant formulations have been widely 
adapted by the art for use in combination with a great variety of 
polyamides. The further addition of reinforcing fillers such as glass 
fibers is also well-known in the art. 
Flame retardants are intended to decompose under combustion conditions, 
hence most have limited thermal stability at elevated temperatures. High 
performance thermoplastics, for example aromatic polyesters and high 
temperature polyamides, are necessarily compounded at elevated 
temperatures, often at temperature well above the decomposition 
temperatures of many fire retardants such as, for example, the combination 
of a halogen-containing organic compound with antimony oxide. The fire 
retardant thus may decompose thermally during compounding or melt 
fabrication operations, resulting in foaming or generation of corrosive 
by-products that may corrode the processing equipment. Strand-foaming and 
significant discoloration of pellets are also among the problems commonly 
encountered when compounding and molding flame retardant high temperature 
polyamide formulations. 
Further problems may occur when the flame-retardant polyamide resin is used 
continuously in an injection molding operation and over a long period of 
time, continually generating decomposition products that become deposited 
on the mold or in vents. The problem, commonly termed "plate-out", may 
cause staining or discoloration in the molded product as well as blocking 
of vents and possible corrosion in the processing equipment. In order to 
avoid these difficulties it then becomes necessary to stop the molding 
operation at regular intervals and clean the mold and associated 
processing equipment. 
The art has thus continued to seek out other solutions for these problems, 
and more particularly to look for ways to prevent or at least minimize 
decomposition during molding. The use of bromine-containing flame 
retardants in combination with sodium antimonates for flame retarding 
polyesters has long been known to provide more stable formulations. 
Similar improvement is seen for polyterephthalamides, particularly when 
used in combination with further adjuvants. A hydrotalcite-type complex 
hydroxide or an oxide of magnesium or zinc may be required for 
formulations comprising polyamides to adequately inhibit decomposition and 
maintain color in molded articles. See U.S. Pat. No. 5,115,010. 
The use of bromine-compounds as flame retardants in combination with 
antimony trioxide and a styrene-maleic anhydride copolymer are disclosed 
for use with aliphatic polyamides including nylon 6,6 in U.S. Pat. No. 
4,788,244. These and other brominated flame retardants have also been 
employed for flame retarding high temperature polyamides, alone and in 
combination with an amine-type stabilizer or a phosphorus-type stabilizer. 
See U.S. Pat. No. 5,256,718. 
The art-recognized flame retardants have not been completely successful in 
avoiding decomposition when used in combination with partially aromatic 
copolyphthalamides. Plate-out, and corrosion of processing equipment when 
melt fabricating these resins, as well as severe discoloration of the 
molded articles remain a serious problem for the molder. Conventional 
adjuvants are found to have a markedly deleterious effect on the melt 
viscosity of these resins, leading to major problems in melt fabrication 
operations. Moreover, many of the prior art flame retardant formulations 
recognized for use with polyamides are found to reduce the crystallinity 
of high temperature partially aromatic copolyphthalamides, particularly 
when the formulation is subjected to repeated melt processing, and this 
deficiency may severely limit their acceptability for use in applications 
where a high degree of dimensional stability at elevated temperatures is 
necessary. 
A method for improving the overall stability of flame retarded 
polyphthalamide resins under the melt processing conditions required for 
their fabrication, thereby minimizing discoloration and accomplishing a 
further reduction in the production of corrosive volatile decomposition 
products, would clearly represent an advance in the art. 
SUMMARY OF THE INVENTION 
This invention is directed to fire-retarded, high temperature polyamides 
comprising conventional fire retardants wherein the thermal stability, 
particularly during melt processing, is improved by the further addition 
of calcium oxide, and to a method for improving the thermal stability of 
flame retarded high temperature polyamides. The invented compositions 
exhibit good melt viscosity characteristics and a significant reduction in 
thermal decomposition when subjected to melt processing as shown by a 
reduced evolution of corrosive volatile byproducts. Molded articles 
comprising the invented formulations are improved in color. 
The invented method may be particularly useful for providing improved heat 
aging characteristics and molding stability in high temperature 
polyphthalamides that are flame retarded with conventional 
bromine-containing flame retardants. The desirable mechanical, chemical 
and physical properties that are typical of polyphthalamides are 
maintained for these improved formulations and retained during thermal 
processing, even after repeated exposure to extreme temperature conditions 
such as, for example, the conditions encountered during injection molding 
or other melt processing operations.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The improved fire retardant polyamide compositions of this invention will 
comprise a high temperature polyamide, preferably a fiber-filled high 
temperature polyamide, flame retarded with a conventional flame retardant 
combination of a halogen-containing organic compound and an 
antimony-containing compound, together with calcium oxide. More 
preferably, the improved flame retarded polyamide composition of this 
invention will be a glass fiber-filled polyphthalamide containing a 
conventional flame retardant, preferably a combination of a 
bromine-containing flame retardant and an antimony-containing compound, 
the thermal stability of the composition being improved according to the 
teachings of this invention by adding thereto from about 0.2 to about 2 wt 
% calcium oxide, based on total weight. 
Polyphthalamides that are particularly desirable for use as the high 
temperature polyamide component in the practice of the invention include 
the various linear, high temperature polyphthalamides that require high 
processing temperatures and are thus difficult to melt process without 
deterioration. Particularly preferred are the crystalline or 
semi-crystalline high temperature partially-aromatic copolyphthalamides 
comprising terephthalamides of aliphatic diamines as well as further 
copolymers thereof containing aliphatic diamide moieties. Particularly 
preferred copolymers include those containing at least 40 mole % of the 
terephthalamide units, together with at least one aliphatic diamide of an 
aliphatic diamine. 
In greater detail, the polyphthalamide component of the invented 
compositions may be a crystallizable polyamide comprising at least about 
40 mole %, preferably greater than about 50 mole % recurring aliphatic 
diamine terephthalamide units which may be further described as 
represented by the following structural formula: 
##STR1## 
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 2 to about 14 carbon atoms. These 
radicals are preferred because polyphthalamides comprising the same 
exhibit good crystallinity and desirable high temperature properties, 
together with melting and thermal degradation temperatures making them 
well suited for melt processing with the modifying components of the 
invented compositions. 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 2 to 14 carbon atom radicals. 
The polyphthalamide component will have a melting point of at least about 
270.degree. C. as a result of the high content of terephthalamide units. 
Preferred polyphthalamide components are those melting at about 
290.degree. C. to about 330.degree. C. because the same exhibit 
particularly desirable thermal properties and are more easily processed 
than even higher melting polyphthalamides. 
The polyphthalamide component of the invented compositions also may 
comprise a portion of recurring units as described above but wherein 
radicals R are replaced with one or more other types of divalent 
hydrocarbyl radicals, e.g. substituted or unsubstituted aromatic radicals. 
Specific examples of such other radicals include m-phenylene, p-phenylene, 
m-xylylene, p-xylylene, oxybisphenylene and methylene bisphenylene. When 
such other radicals are present, the proportion thereof should not be so 
great as to adversely affect desirable properties of the polyphthalamide 
component, such as strength, thermal properties and melt processability. 
Preferably, not greater than about 30 mole % of the recurring units of the 
polyphthalamide comprises such other radicals. 
The polyphthalamide may further comprise, in addition to the 
terephthalamide units represented by the formula above, one or more other 
recurring carbonamide units including aliphatic diamine aliphatic diamide 
units such as, for example, hexamethylene adipamide, 
2-methylpentamethylene adipamide, hexamethylene sebacamide, hexamethylene 
azeleamide, hexamethylene dodecamethylamide, hexamethylene 
cyclohexanedicarboxylamide, dodecamethylene adipamide, and units derived 
from lactams such as caprolactam; aromatic diamide units such as 
m-xylylene isophthalamide, p-xylylene isophthalamide, oxybisphenylene 
isophthalamide or the like; and aliphatic-aromatic diamide units such as, 
for example, hexamethylene isophthalamide, hexamethylene 2,6-naphthalene 
dicarboxylamide, m-xylylene adipamide, heptamethylene isophthalamide, 
dodecamethylene isophthalamide, m-phenylene adipamide or the like. 
Preferred among such additional carbonamide units are hexamethylene 
adipamide, hexamethylene isophthalamide and caprolactam units and 
combinations thereof. 
Proportions of such other carbonamide units in the polyphthalamide 
compositions should not be such as to adversely affect processability or 
desirable properties of the invented compositions. Generally, at least 
about 40 mole % of the carbonamide moieties of the polyphthalamide 
composition is provided by aliphatic diamine terephthalamide units 
corresponding to the formula above to assure crystallinity and desirable 
strength and thermal properties. More preferably, greater than about 50 
mole %, and still more preferably from about 50 to about 90 mole % of such 
moieties are provided by such units to achieve good properties and ensure 
melt processing compatibility of the polyphthalamide component and the 
modifying component. 
A preferred polyphthalamide for use in the flame-retarded component of the 
invented compositions comprises a semicrystalline polyphthalamide of fast 
or intermediate crystallization rate comprising recurring units 
corresponding to structural formulas A, B and C as shown below in 
proportions of about 40 to about 95 mole % A, 0 to about 35 mole % B and 
about 5 to about 60 mole % C. 
##STR2## 
In the above formulas, R comprises at least one aliphatic hydrocarbyl 
radical as described hereinabove, and may represent a mixture of aliphatic 
2 to 14 carbon atom radicals. 
Particularly preferred among such polyphthalamides are those wherein the 
mole ratio of the units A, B and C ranges from about 55-70:25-0:45-5 
because such compositions exhibit excellent thermal and mechanical 
properties. Such polyphthalamides have melting points of about 300.degree. 
to about 350.degree. C., glass transition temperatures (T.sub.g) of about 
90.degree. to about 130.degree. C. and inherent viscosities generally 
ranging from about 0.75 to about 1.4 dl/g with about 0.9 to about 1.25 
dl/g being preferred from the standpoint of properties of molded parts and 
ease of molding. 
Especially preferred among such polyphthalamides are those wherein R in the 
above formulas comprises hexamethylene. Also highly suitable as the 
polyphthalamide component of the invented compositions are 
polyphthalamides comprising two of the units A, B and C shown above, such 
as those with mole ratios of 45:0:55, 60:0:40 and 55:0:45, while 
terpolymers with minor amounts of the isophthalamide component B, for 
example in mole ratios such as 50:5:45, 40:5:55 and the like, may be found 
particularly desirable for use where lower melt temperatures will be 
encountered. 
Although the molecular weight of the polyphthalamide is not particularly 
important to the practice of the invention, resins having inherent 
viscosities greater than about 0.7, preferably greater than about 0.8, 
when measured at 30.degree. C. in a 60/40 phenol/tetrachloroethylene (TCE) 
mixture at a concentration of 0.4 g/dl will be preferred for most molding 
applications. Although there is no particular upper limit for molecular 
weight of the polyphthalamide component, to be suitable for use in these 
compositions the resin must be melt processable, and very high molecular 
weight polyphthalamides, those with an inherent viscosity much above about 
1.5 to as great as 2.0 or greater, may be extremely difficult to process 
thermally either by injection molding or by extrusion, hence such resins 
will not be preferred. 
A variety of copolyphthalamides including those described herein as 
preferred are readily available from commercial sources, and methods for 
their preparation are also fully described in the art, for example, in 
U.S. Pat. Nos. 4,603,166 and 4,831,108, 5,112,685 and 4,163,101 and in 
European Patent Application 309,095; the teachings of these patents and 
applications are hereby incorporated herein by reference. Polyphthalamides 
comprising hexamethylene diamine terephthalamide units together with one 
or more additional units such as hexamethylene adipamide units, 
hexamethylene isophthalamide units and the like are available from a 
variety of commercial sources, including Arlen.RTM. polyamides from Mitsui 
Corporation and Amodel.RTM. polyphthalamide resins from Amoco Polymers, 
Inc. 
Copolymers and terpolymers comprising terephthalamides of two or more 
aliphatic diamines or terephthalamides of mixed isomeric aliphatic 
diamines such as hexamethylene diamine and 2-methylpentamethylene diamine 
have been described in the art, and copolymers comprising units of 
caprolactam together with units of hexamethylene diamine terephthalamide 
are available commercially as Ultramid polyamides from BASF Corporation. 
However, the addition of calcium oxide according to the teachings of the 
invention to flame-retarded terephthalamide copolymers that do not contain 
aliphatic diamide units such as hexamethylene adipamide units will be seen 
to provide little if any improvement in processing stability or color. 
Such copolymers are therefore not preferred. 
The high temperature polyamides are made flame retardant by further 
compounding with a conventional flame retardant combination of a 
organohalogen compound and an antimony compound. 
Generally, the organohalogen compounds known in the art and conventionally 
described as halogen-containing fire-retardant compounds will be suitable 
for use in the practice of the invention and particularly desirable among 
them will be those generally characterized as bromine-containing flame 
retardants. Such compounds are available from commercial sources and 
include, for example, brominated polystyrene, available as Pyrocheck.RTM. 
from Ferro Corporation, brominated polyphenylene ether, available as PO64P 
from Great Lakes Corporation and polydibromostyrene, available from 
Teijin, Ltd. and as PDBS80 from Great Lakes Corporation. 
Additional suitable halogenated compounds are also disclosed in the art 
such as, for example, polytribromostyrene, polypentabromostyrene, 
polydichlorostyrene, polytrichlorostyrene, polypentachlorostyrene and 
polytribromo-alpha-methylstyrene, as well as polydibromo-p-phenylene 
oxide, polytribromo-p-phenylene oxide, polydichloro-p-phenylene oxide, 
polybromo-p-phenylene oxide, and polybromo-o-phenylene oxide, and a number 
of such compounds may also be available from commercial sources. 
Polybrominated biphenyl, brominated phenoxy resins and the like, as well 
as chlorine-containing flame retardants such as Dechlorane, are also 
available from a variety of commercial sources for use as flame 
retardants, and these may also be found useful in the practice of this 
invention. Bromine-containing flame retardants and particularly brominated 
polystyrene flame retardants will generally be preferred. 
The halogenated flame retardant compounds are generally used in the art in 
combination with an antimony compound. Among the antimony compounds 
conventionally used with brominated polystyrenes and with brominated 
polyphenylene oxides as a fire-retarding aid are antimony trioxide and 
sodium antimonate. A main component of sodium antimonate sold for use as a 
fire-retarding aid has the chemical composition Na.sub.2 Sb.sub.2 O.sub.6. 
Generally, the antimony compound will be used in a finely divided form, 
having particle diameter of preferably not more than 30 microns, more 
preferably not more than 10 microns. 
Conventionally, flame retardant formulations comprise 100 pbw (parts by 
weight) of the polyamide, from about 10 to 100 pbw of the 
bromine-containing organic compound, preferably a bromine-containing 
styrene polymer such as brominated polystyrene or polydibromostyrene, and 
from about 0.5 to about 50 pbw, preferably from about 1 to about 15 pbw of 
the antimony compound, preferably sodium antimonate. 
Optionally, the flame retarded polyamide compositions according to this 
invention may further comprise from about 10 to about 60 wt %, preferably 
from about 10 to about 45 wt %, of a fibrous reinforcing agent. Fibrous 
reinforcing agents are commonly added to such formulations in order to 
impart further improvement in heat resistance and fire-retardant 
properties, as well as to increase rigidity, tensile strength and flexural 
strength. Fibrous reinforcing agents suitable for use in the practice of 
this invention include any of the inorganic fibrous reinforcing agents 
conventionally employed in the art as reinforcing fillers for polyamides 
such as glass fibers, potassium titanate fibers, metal-coated glass 
fibers, ceramic fibers, wollastonite, carbon fibers, metal carbide fibers 
and metal-hardened fibers. The surfaces of such fibrous reinforcing agents 
may be treated as necessary with conventional sizing agents, lubricants 
and the like. Glass fibers are widely known as particularly effective 
reinforcing agents for polyamide resins and these will be preferred. 
Combinations of organohalogen compounds and antimony compounds are 
well-known and widely used commercially for flame retarding a great many 
resins, and have generally been found to be highly acceptable for use with 
aliphatic polyamides such as nylon 6,6 and the like. However, the 
combination of a halogenated polystyrene or halogenated polyphenylene 
oxide with sodium antimonate is generally reasonably stable only at 
processing temperatures of up to about 300.degree. C. Many of the 
commercially available flame retardants such as polybrominated polystyrene 
are described by their suppliers as being not recommended for use at 
temperatures above about 320.degree. C. because of the extensive 
decomposition that occurs at these high temperatures. Because high 
temperature polyamides generally are melt fabricated at temperatures well 
in excess of 300.degree. C., indeed as high as 350.degree. C., 
particularly when filled, thermal decomposition of the flame retardant 
frequently occurs, in turn inevitably causing the molded article to be 
discolored and detrimentally affecting the mechanical properties of the 
resin composition. 
In order to improve the heat stability and thereby eliminate or minimize 
thermal decomposition during molding, the flame retardant high temperature 
polyamide formulations of this invention further comprise finely divided 
calcium oxide. The amount of calcium oxide necessary to effect improvement 
in the heat stability may depend in part upon the particular polyamide 
employed, as well as upon the particular combination of antimony oxide and 
halogen-containing flame retardant selected. Generally, the amount will be 
from about 0.05 to about 50 pbw, preferably 0.1 to about 10 pbw calcium 
oxide per 100 pbw of the polyamide component. The amount of calcium oxide 
may also be characterized as being about 0.2 to about 2 wt %, preferably 
from about 0.2 to about 1 wt %, based on total weight of the composition, 
including such fillers, additives and fiber as may also be present. At 
lower levels of calcium oxide the improvement may be found to be 
vanishingly small. While at high levels of calcium oxide, levels greater 
than about 2 wt %, the improvement in thermal stability may also be 
observed, the presence of unneeded particulate materials can detrimentally 
affect other properties including mechanical properties and hence these 
levels are not preferred. The particle size of the heat stabilizer will 
preferably be small, generally less than about 30 microns, preferably not 
more than 10 microns. For some uses, the presence of extremely fine 
particulates, those with a particle size less than about 1 micron, may be 
found to be ineffective for use with some flame retardant materials, or to 
have a deleterious effect on properties, hence these very small 
particulate calcium oxides will preferably be avoided. 
The polyamide compositions of this invention may further contain 
conventional additives widely known and used in the resin arts provided 
that such additives do not significantly affect the desirable flame 
retardant character of the formulation. For example, thermal stabilizers, 
UV stabilizers, plasticizers, nucleating agents, antistatic agents, 
processing aids including mold release agents, lubricants and the like, as 
well as pigments, dyes, inorganic or organic fillers such as carbon black, 
talc, clay, mica and the like may usefully be included. Conventional 
polymeric impact modifiers may also be desirable for use in these 
formulations, including polyolefins such as polyethylene, polypropylene 
and poly(4-methyl-1-pentene), olefin copolymers such as ethylene/propylene 
copolymer, ethylene/1-butene copolymer, propylene/ethylene copolymer and 
propylene/1-butene copolymer, polyolefm elastomers, and the like. The 
great variety of functionally-modified polymers that are well-known and 
widely used in the art as impact modifiers for polyamides may also be 
employed in the practice of this invention, including maleated 
polyolefins, maleated EPR and EPDM olefin rubbers, maleated block 
copolymers and terpolymers comprising styrene segments and olefinic 
polymeric segments, acrylic rubbers and similar copolymers containing 
acrylic or methacrylic units capable of providing reactive functionality, 
and the like. 
Blends of the high temperature polyphthalamide component with other 
polyamides such as nylon 6 or nylon 6,6 are well-known and widely 
disclosed in the art, as are blends comprising polyarylates, 
polycarbonates, polyacetals, polysulfones, polyphenylene oxides, fluorine 
resins and the like. Such blends may also be found useful in the practice 
of the invention. 
Any of the compounding processes commonly used in the resin compounding 
arts may be usefully employed for mixing the polyamide, organohalogen 
flame retardant and the antimony compound components, together with the 
calcium oxide and, as required, the fibrous reinforcing agent, to provide 
the flame retarded formulations of this invention. For example, the solid 
components may be blended in finely divided form using a Henschel mixer, 
V-blender, ribbon blender or tumbler blender, and then melt processed in 
an extruder. The formulation may be profile-extruded to form the finished 
article, or may be provided as a strand or the like and then chopped, 
granulated or pulverized to provide the flame retarded formulation in a 
form suited to further melt fabrication, for example by injection molding, 
sheet extrusion or the like. 
The invented formulation has excellent fire retardancy, heat resistance, 
rigidity and impact strength and a high heat distortion temperature, and 
can be molded into various articles such as machine parts and electric and 
electronic component parts by various molding methods such as compression 
molding, injection molding, extrusion and thermoforming as in the case of 
molding general-purpose thermoplastic resin. The increased thermal 
stability of the invented formulations, even at high compounding 
temperatures, prevent or substantially reduce the incidence of foaming or 
unacceptable coloration during processing, and may prevent plate out and 
corrosion of molds and molding equipment. The improved thermal stability 
of these formulations may also be important in applications where 
fire-retardant polyamides having excellent heat resistance, particularly 
soldering resistance, and a high heat distortion temperature are needed. 
The invention will be better understood by consideration of the following 
examples in which the effectiveness of calcium oxide as an additive to 
flame retarded formulations was evaluated. 
EXAMPLES 
In these examples, blend formulations containing various polyphthalamide 
(PPA) copolymers together with the flame retardant combination of 
bromine-containing organic compound and sodium antimonate and calcium 
oxide were compared with control examples containing no calcium oxide and 
with comparison formulations containing prior art additives, particularly 
magnesium oxide and zinc oxide. 
The following analytical methods were employed to obtain the data necessary 
for making the comparisons. 
Differential Scanning Calorimetry (DSC) 
The thermal stability of these blends was investigated by exposing the 
material to three cycles of heating and cooling by heating from 0.degree. 
C. to 350.degree. C. at 20.degree. C./min and cooling from 350.degree. C. 
to 50.degree. C. at 10.degree. C./min (entire procedure in nitrogen). By 
repeating this heating and cooling three times, three different melting 
temperatures, crystallization temperatures, and heats of fusion and 
crystallization were obtained. 
Kayeness Rheology 
The sample was first dried to a moisture content &lt;500 ppm using a vacuum 
oven at 100.degree. C. The melt viscosity of the dried sample was measured 
in a Kayeness rheometer fitted with a capillary having a diameter of 0.04 
inches, L/D ratio of 15/1 and an entrance angle of 90.degree. C., using 
test weight of 11.0 grams, a melt time of 188 seconds, a delay time of 87 
seconds, and a melt force of 300 lbs; the sample was tested at a shear 
rate of 400 see.sup.-1 and 335.degree. C. Melt viscosity was recorded 
after dwell times of 5 minutes (t5), 10 minutes (t10), and 15 minutes 
(t15). 
Thermogravametric analysis (TGA) 
The sample weight was monitored while heating in dry nitrogen at a rate of 
10.degree. C./min. The data are presented as the temperature at which a 
certain percentage of weight is lost (either 1%, 2%, 5% or 10%). 
Off-gas analysis 
This method provides a measure of the amount of HBr and HCl given off by 
the formulation when heated at a temperature selected to fall in the 
normal processing range for these materials. The analysis is carried out 
by placing a ceramic boat containing approximately 5 g of polymer in a 
quartz tube and heating the tube in a furnace while collecting the 
off-gases by means of a helium stream and absorbing the acid components in 
water. After first thoroughly drying the sample by heating at 250.degree. 
C. for 30 minutes in a stream of helium, the furnace temperature is 
increased to 340.degree. C. and held for 30 minutes while the gases 
exiting the tube are passed through a gas collection tube containing 75 ml 
of deionized water. The tube contents are then diluted to 100 ml and 
analyzed for HCl and HBr concentrations by IC methods. 
The formulations of the following examples were prepared using the 
following components: 
______________________________________ 
Polyamide: 
______________________________________ 
PPA-1 Hexamethylene terephthalamide/hexamethylene adipamide 
65/35 copolymer, obtained as Amodel A-4000 PPA 
polyphthalamide from Amoco Polymers, Inc. 
PPA-2 Hexamethylene terephthalamide/Hexamethylene 
terephthalamide/hexamethylene adipamide 65/25/10 
copolymer, obtained as Amodel A-1000 PPA 
polyphthalamide from Amoco Polymers, Inc. 
PPA-3 Hexamethylene terephthalamide/hexamethylene adipamide 
55/45 copolymer, obtained as Amodel A-6000 PPA 
polyphthalamide from Amoco Polymers, Inc. 
PPA-4 Polymer of terephthalic acid, adipic acid 
(75/25)/Hexamethylene diamine 2- 
methylpentamethylene diamine (77/23). 
PPA-5 Hexamethylene terephthalamide/caprolactam (70/30) 
copolymer. 
PPA-6 Hexamethylene terephthalamide/2-methylpentamethylene 
terephthalamide (50/50) copolymer. 
______________________________________ 
______________________________________ 
Flame Retardant: 
______________________________________ 
FR-1 Brominated polystyrene flame retardant, obtained as 
Pyrochek 68-PB from Ferro Corporation. 
FR-2 Poly(dibromostyrene) flame retardant, obtained as 
PDBS80 from Great Lakes Chemical Company. 
Sodium Obtained as Polybloc .RTM. SAP-2 from Anzon 
Antimonate 
Division of Cookson Specialty Additives. 
______________________________________ 
______________________________________ 
Metal Oxide: 
______________________________________ 
CaO-1 Calcium oxide obtained from Aldrich Chemical Company. 
CaO-2 Calcium oxide obtained from Chemie Limited. 
CaO-3 Calcium oxide having 1-5 micron particle size, obtained as 
CA602 from Atlantic Equipment Engineers. 
CaO-4 Calcium oxide having &lt;1 micron particle size, obtained as 
CA603 from Atlantic Equipment Engineers. 
ZnO Zinc Oxide. 
MgO Magnesium oxide, obtained as KM-3-150 from Kyowa. 
______________________________________ 
______________________________________ 
Additives: 
______________________________________ 
PTFE Polytetrafluoroethylene lubricant, obtained as Algoflon 
DF-11X from Ausimont, U.S.A. 
Talc Obtained as Mistron Vapor Talc from Luzenac America, Inc. 
PEPQ Phosphite thermal stabilizer obtained as SandoStab PEPQ 
from Sandoz Chemical Company. 
______________________________________ 
All formulations contain 33 wt % glass fiber, unless otherwise indicated. 
All formulations are given in wt % based on total weight of the 
formulation, including fiber where present. 
Examples 1-5 
Control Example and Comparative Examples C1-C6 
The compositions of the examples set forth below were prepared by mixing 
the requisite amounts of resin and additives and then melt extruding the 
blend using methods and processing equipment common to the resin 
processing art. Generally, the dry blends were extruded using a Berstorff 
25 mm twin screw extruder, fitted with a #11 screw and vacuum vented at 
approximately 25 inches Hg, using barrel temperatures in the range 
300.degree.-345.degree. C. (set point), melt temperatures of about 
320.degree.-325.degree. C., and nominal screw speeds of about 300 rpm. 
TABLE 1 
______________________________________ 
Flame Retardant, 33 wt % Glass Fiber-filled, 
PPA-1 Polyphthalamide Formulations 
Sodium 
Anti- 
Ex. PPA-1 FR-1 monate 
PTFE Talc Oxide 
No. wt %* wt %* wt %* wt %* wt %* wt %* 
______________________________________ 
control 
43.43 18.68 3.61 1.0 0.28 none 
1 43.17 18.56 3.58 1.0 0.28 0.4% CaO-1 
2 43.17 18.56 3.58 1.0 0.28 0.4% CaO-2 
3 42.91 18.45 3.56 1.0 0.28 0.8% CaO-2 
4 42.91 18.45 3.56 1.0 0.28 0.8% CaO-3 
5 42.91 18.45 3.56 1.0 0.28 0.8% CaO-4 
C1 43.17 18.56 3.58 1.0 0.28 0.4% ZnO 
C2 42.91 18.45 3.56 1.0 0.28 0.8% ZnO 
C3 43.17 18.56 3.58 1.0 0.28 0.4% MgO 
C4 43.17 18.56 3.58 1.0 0.28 0.4% CaCO.sub.3 
C5 42.77 18.39 3.55 1.0 0.28 0.8% CaO-2 
0.2% MgO 
C6 42.77 18.39 3.55 1.0 0.28 0.8% ZnO 
0.2% MgO 
______________________________________ 
Note: *Wt % based on total weight of formulation, including glass fiber 
(33 wt %). For abbreviations, details of components, see text. 
These test formulations were molded as needed to provide appropriate test 
specimens, and these were analyzed by DSC, TGA and Kayeness rheology 
methods as outlined above. Injection molding was accomplished using a 30 
ton Boy screw injection molding machine at melt temperatures in the range 
305.degree.-335.degree. C. and an oil-heated mold at a temperature of 
about 190.degree. F. 
The molded test specimens were also observed for color and appearance, and 
specimens were subjected to a vertical burning test in accordance with 
UL-94 Standards and to tensile testing in accordance with ASTM-D638. 
TABLE 2 
__________________________________________________________________________ 
Effect of Various Oxides on the DSC Stability of Blends 
Crystallization Temperature (Tc) 
Ex. Additive 
1st Cool 
2nd Cool 
3rd Cool 
.DELTA.Tc 
.DELTA.Hc 
No. wt % .degree.C. 
.degree.C. 
.degree.C. 
(3rd - 1st) 
(3rd/1st) 
__________________________________________________________________________ 
control 
None 284.0 
272.6 
221.2 
62.8 0.19 
1 0.4% CaO-1 
289.6 
283.1 
276.3 
13.3 0.90 
2 0.4% CaO-2 
290.4 
283.2 
275.5 
14.9 0.89 
3 0.8% CaO-2 
290.0 
282.9 
276.2 
13.8 0.88 
4 0.8% CaO-3 
290.3 
284.3 
278.0 
12.2 0.81 
5 0.8% CaO-4 
282.3 
265.1 
241.0 
41.3 0.26 
C1 0.4% ZnO 
286.5 
274.5 
258.4 
28.1 0.83 
C2 0.8% ZnO 
285.7 
272.9 
255.1 
30.7 0.74 
C3 0.4% MgO 
289.9 
269.8 
242.2 
47.7 0.59 
C4 0.4% CaCO.sub.3 
257.1 
-- -- -- -- 
C5 0.8% CaO-2 
289.2 
273.6 
254.5 
34.7 0.74 
0.2% MgO 
C6 0.8% ZnO 
288.4 
277.0 
262.2 
26.3 0.76 
0.2% MgO 
__________________________________________________________________________ 
DSC data for the blends of Table 1 are summarized in Table 2. It will be 
apparent that all of the oxides improved the retention of crystallinity, 
as measured by a lessened shift of the third temperature of 
crystallization compared with the first cycle, .DELTA.Tc (3rd -1st). There 
also is seen an improvement in the retention in crystallinity, as shown by 
ratio of the heat of crystallization for third and first heat, 
.DELTA.Hc(3rd/1st). Calcium oxide is seen to be much more effective at 
maintaining the position of the third crystallization peak and retaining 
the heat of crystallization in the third cooling than either of the prior 
art additives zinc oxide and magnesium oxide. Moreover, a high loading of 
ZnO (0.8% instead of 0.4%) produced a blend with even lower retention of 
crystallinity. CaCO.sub.3 caused a substantial reduction in stability; the 
run was stopped after the first cycle, and no further DSC data were 
obtained. 
While calcium oxide appears to be an effective additive for this purpose, 
for extremely low particle size calcium oxide, less than 1 micron, the 
effectiveness in retention of crystallinity was substantially reduced. 
TABLE 3 
______________________________________ 
Effect of Various Oxides on the Kayeness Stability of Blends 
Ex. Additive Viscosity (poise) After 
t10/t5 
t15/t5 
No. wt % 5 min. 10 min. 
15 min. 
% % 
______________________________________ 
control 
None 2799 1797 1349 64 48 
1 0.4% CaO-1 2382 1793 1350 75 57 
2 0.4% CaO-2 2089 1629 1271 78 61 
3 0.8% CaO-2 2174 1653 1257 76 58 
4 0.8% CaO-3 1849 1369 1013 74 55 
5 0.8% CaO-4 2025 1414 1003 70 50 
C1 0.4% ZnO 1446 507 1092 35 76 
C2 0.8% ZnO 1190 109 88 9 7 
C3 0.4% MgO 1131 354 1087 31 96 
C4 0.4% CaCO.sub.3 
2580 1213 -- 47 -- 
C5 0.8% CaO-2 1558 303 1069 19 69 
0.2% MgO 
C6 0.8% ZnO 1449 184 844 13 58 
0.2% MgO 
______________________________________ 
The Kayeness viscosity data presented in Table 3 demonstrates that addition 
of calcium oxide improved the viscosity profile of this blend. Addition of 
either ZnO or MgO had a dramatically negative effect on the viscosity 
stability of the blend, as did the formulation containing CaCO.sub.3. 
These in turn have an unfavorable affect on processability, causing die 
drool and melt stability problems. The presence of even a small amount of 
magnesium oxide, as in Comparison, Example C5, negatively affects the 
viscosity of the blend. While not wishing to be found by a particular 
theory, loss in melt viscosity over time is generally thought to be 
associated with a reduction in polymer molecular weight resulting from 
shear degradation or thermal decomposition during processing. For some 
polymer formulations a loss in melt viscosity may occur during thermal or 
shear processing, followed by an increase in melt viscosity over time, 
which is believed to be an indication that cross-linking in the melt has 
occured. 
TABLE 4 
______________________________________ 
Effect of Various Oxides on the Thermogravametric 
Analysis of Blends 
Temperature (.degree.C.) at: 
Additive 1% 2% 5% 10% 
Ex. No. 
wt % Wt. Loss Wt. Loss 
Wt. Loss 
Wt. loss 
______________________________________ 
control 
None 353.46 368.63 375.55 381.11 
1 0.4% CaO-1 
353.03 377.29 388.29 393.46 
2 0.4% CaO-2 
369.85 380.48 387.45 392.58 
3 0.8% CaO-2 
368.10 383.72 393.16 398.76 
4 0.8% CaO-3 
369.41 384.98 395.76 401.54 
5 0.8% CaO-4 
356.20 363.36 371.20 378.65 
C1 0.4% ZnO 360.06 374.56 384.81 390.95 
C2 0.8% ZnO 356.83 372.62 387.69 393.35 
C3 0.4% MgO 334.71 361.04 381.23 387.52 
C5 0.8% CaO-2 
355.75 373.92 391.17 397.73 
0.2% MgO 
C6 0.8% ZnO 361.70 378.00 395.18 403.84 
0.2% MgO 
______________________________________ 
The Thermogravametric data are summarized in Table 4. It will be seen that 
adding calcium oxide decreased the rate of volatiles. The source of 
calcium oxide may affect weight loss; at 8% CaO, the smallest particle 
size CaO gave the poorest performance with respect to volatiles. Both ZnO 
decrease the temperature for 1% weight loss, with magnesium oxide given 
the poorest result. This is a significant negative, and may be the reason 
that blends with MgO give more plate-out than those without MgO. 
TABLE 5 
______________________________________ 
Effect of Various Oxides on the Tensile Data 
and Flame Rating of Blends 
Tensile Burn Mold 
Additives Strength 
E Burn Time Sprue 
Ex. No. 
wt % (psi) (%) Rating (sec) 
Color 
______________________________________ 
control 
None 26,220 1.80 V0 16 Gray w/ 
No Drip dark sections 
1 0.4% CaO-1 
26,180 1.73 V0 24 Tan with 
No Drip medium gray 
region 
2 0.4% CaO-2 
26,650 1.74 V0 25 Tan 
No Drips 
3 0.8% CaO-2 
25,320 1.67 V1 31 Tan 
No Drips 
4 0.8% CaO-3 
24,390 1.54 V0 13 Dark Tan 
No Drips 
5 0.8% CaO-4 
25,290 1.61 V0 26 Dark Tan 
2/5 Drips 
C1 0.4% ZnO 25,680 1.66 V0 21 Light Gray 
No Drips 
C2 0.8% ZnO 24,590 1.59 V0 27 Gray 
No Drips 
C3 0.4% MgO 23,100 1.45 V0 12 Tan with 
No Drip medium gray 
region 
C4 0.4% CaCO.sub.3 
28,250 V2 7 Dark Gray 
FI Drip with black 
regions 
C5 0.8% CaO-2 
23,870 1.55 V1 55 Tan 
0.2% MgO 1/5 Drip 
C6 0.8% ZnO 24,070 1.51 V0 26 Gray 
0.2% MgO No Drips 
______________________________________ 
Table 5 summarizes the tensile and flame data for these blends. With 
respect to color, both calcium oxide and magnesium oxide gave moldings 
with improved color, tan for these formulations, compared with gray for 
the control; zinc oxide also gave an undesirable gray color. Magnesium 
oxide reduced tensile strength markedly, by 2,000-3,000 psi at only 0.4%, 
loading of 0.8%, calcium oxide and zinc oxide effected smaller decreases 
in about 1,000-2,000 psi. It was also observed for molded specimens of 
these resins that compositions containing MgO (C3) exhibited considerable 
splay marking on the surfaces, while those with CaO had no such splay 
markings. 
TABLE 6 
______________________________________ 
Effect of Various Oxides on HBr and HCl Evolution 
Ex. Additive HBr HCl 
No. wt % (ppm) (ppm) 
______________________________________ 
control No Additives 391 74 
C3 0.4% MgO 221-457 13-14 
1 0.4% CaO 255-303 35-42 
C6 0.4% CaO + 0.4% PEPQ 
156 38 
2 0.4% CaO-2 129 28 
3 0.8% Chemie Ltd CaO-2 
9 8 
4 0.8% CaO-3 3 4 
5 0.8% CaO-4 321 68 
C1 0.4% ZnO 61 6 
C2 0.8% ZnO 2 3 
______________________________________ 
The off-gases produced in decomposition for several blends were also 
analyzed. The results are summarized in Table 6. Without any oxide, the 
Control example produced a high concentration of both HBr and HCl. 
Addition of 0.4% magnesium oxide, calcium oxide, or zinc oxide does reduce 
both HCl and HBr; however higher levels of CaO may be required for 
effective acid scavenging. 
Thus, it will be seen from the data and comparisons set forth in Tables 2-5 
that adding calcium oxide to the flame retarded polyphthalamide leads to a 
product with an optimum property profile. The addition of calcium oxide 
with particle size of 1-5 micron, preferably at an 0.8% weight loading, 
provided a flame retarded polyphthalamide blend improved in viscosity. In 
contrast, zinc oxide and magnesium oxide, the additives taught by the 
prior art to be useful in combination with brominated flame retardants, 
are seen to cause catastrophic loss of viscosity as measured by the 
Kayeness rheometry when used with high temperature polyamides (see Table 
3). The prior art additives are also less effective than calcium oxide at 
stabilizing crystallinity, as determined by DSC measurement, (see Table 
2). Magnesium oxide is seen to increase the rate of volatilization, as 
measured using TGA, and to cause serious splaying in the molded articles, 
while zinc oxide caused discoloration (see Tables 4 and 5). 
The use of calcium oxide according to the invention in combination with 
other flame retardants and in other polyphthalamides is shown in the 
following examples. 
Example 6 
Control Example and Comparative Examples C7 and C8 
In the following examples, polyphthalamide formulations were prepared and 
tested substantially as in Examples 1-5, but using FR-2 
poly(dibromostyrene) as the flame retardant component. The formulations of 
Example 6, C7 and C8 contained 43.17 wt % PPA-1, 18.56 wt % FR-2 
polydibromostyrene, 3.58 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.28 wt % 
talc and 0.4 wt % of the metal oxide additive, together with 33 wt % glass 
fiber. A control example without metal oxide was similarly prepared having 
43.43 wt % PPA-1, 18.68 wt % FR-2 polydibromostyrene, 3.61 wt % Sodium 
Antimonate, 1.0 wt % PTFE, and 0.27 wt % talc, together with 33 wt % glass 
fiber. The results of testing for these formulations are summarized in 
Table 7. 
TABLE 7 
__________________________________________________________________________ 
Effect of Various Oxides on Glass-filled Polyphthalamides with 
FR-2 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
contr. 
None 76 white 
347.8 
15.2 
0.83 
n.d. 
n.d. 
6 0.4% CaO- 
58 white 
402.0 
12.6 
0.93 
26.8 
V0 
3 no drip 
C7 0.4% ZnO 
32 white 
389.9 
25.9 
0.88 
25.4 
V0 
no drip 
C8 0.4% Mgo 
26 white 
372.3 
32.1 
0.90 
26.4 
V2 
1/5 drip 
__________________________________________________________________________ 
Notes: n.d. = not determined; for tests, see text and Tables 2-5. 
The alternative bromine source, poly(dibromostyrene), improves the color 
stability of the formulation, and the viscosity stability of the control 
formulation with FR-2 is also improved over that of the formulation 
containing FR-1 (see Table 3). However, the further addition of calcium 
oxide to the flame retardant polyphthalamide formulation is again seen to 
be more effective in improving TGA stability and DSC stability than adding 
either zinc oxide or magnesium oxide. 
Examples 7-9 
In the following examples, the effectiveness of calcium oxide at higher 
levels, greater than 0.8 wt %, was evaluated. 
Polyphthalamide formulations with higher levels of calcium oxide were 
prepared and tested substantially as in Examples 1-5, but with the talc 
component omitted. The formulations contained a minor amount of potassium 
acid phosphate, K.sub.2 HPO.sub.4, as an aid in preventing or reducing 
drip during flame testing. The formulations are summarized in Table 8, the 
test data in Table 9. 
TABLE 8 
______________________________________ 
FR-1 Flame Retardant, 33 wt % Glass Fiber-filled, 
PPA-1 Polyphthalamide Formulations 
Sodium 
Anti- 
Ex. PPA-1 FR-1 monate 
PTFE K.sub.2 HPO.sub.4 
Oxide 
No. wt %* wt %* wt %* wt %* wt %* wt %* 
______________________________________ 
7 42.82 18.42 3.56 1.0 0.40 0.8% CaO-3 
8 42.29 18.19 3.52 1.0 0.40 1.6% CaO-3 
9 41.23 17.74 3.43 1.0 0.40 3.2% CaO-3 
______________________________________ 
Note: *Wt % based on total weight of formulation, including glass fiber 
(33 wt %). For abbreviations, details of components, see text. 
TABLE 9 
__________________________________________________________________________ 
Effect of Calcium Oxide Level on Glass-filled PPA-1 
Polyphthalamides with FR-1 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
7 0.8% CaO-3 
65 Dark 
379.3 
15.3 
0.94 
29.5 
V0 
Tan no drip 
8 1.6% CaO-3 
75 Dark 
362.9 
16.1 
0.63 
24.5 
V0 
Tan no drip 
9 3.2% CaO-3 
25 Dark 
364.5 
14.3 
0.0 18.1 
V2 
Tan 1/5 drip 
__________________________________________________________________________ 
High levels of calcium oxide, levels above about 1%, have a detrimental 
affect on the properties of the polyphthalamide formulation. Retention of 
crystallinity (.DELTA.Hc) is negatively affected even at the 1.6% level 
(Example 8), and the effect on tensile strength as well as viscosity 
stability (Kayeness t10/t5) is seen to be quite severe at the 3.2% level, 
and Burn Rating is also lower (Example 9). 
The effectiveness of calcium oxide in improving stability of flame 
retardant polyphthalamides according to the invention will be seen to 
extend to impact-modified formulations, as shown by the following example. 
Example 10 and Comparative Examples C9 and C10 
Impact-modified, glass-filled polyphthalamide formulations were prepared 
and tested substantially as in Examples 1-5, but with FR-2 as the flame 
retardant, and with the further addition of an impact modifier, a styrenic 
block copolymer rubber modifier obtained as Kraton FG1901X modifier from 
Shell Chemical Company. Again, talc was omitted. The formulations 
contained 32.59 wt % PPA-1, 10.86 wt % Kraton FG19O0X modifier, 19.11 wt % 
FR-2 polydibromostyrene, 3.04 wt % Sodium Antimonate, 1.0 wt % PTFE and 
0.4 wt % of the metal oxide additive, together with 33 wt % glass fiber. 
The test results are summarized in Table 10. 
TABLE 10 
______________________________________ 
Effect of Various Oxides on Impact-Modified 33 wt % Glass-filled 
PPA-1 Polyphthalamides with FR-2 Flame Retardant 
Kayeness .DELTA. Tc 
Ex. Additive t10/t5 3rd-1st 
.DELTA. Hc 
No. wt* % % .degree.C. 
3rd/1st 
______________________________________ 
10 0.4 CaO-3 
72 17.9 1.08 
C9 0.4 ZnO 58 31.7 0.30 
C10 0.4 MgO 61 50.9 0.36 
______________________________________ 
Note: 
*Wt % based on total weight of filled; for abbreviations, details of 
components, see text. 
Calcium oxide will be seen to again be more effective in stabilizing the 
viscosity and in maintaining the crystallinity of the impact-modified 
polyphthalamide than either zinc oxide or magnesium oxide. 
Example 11 and Comparative Examples C11 and C12: PPA-2 Polyphthalamide 
Formulations 
In the following examples, polyphthalamide formulations were prepared and 
tested substantially as in Examples 1-5, but using PPA-2 hexamethylene 
terephthalamide/hexamethylene isophthalamide/hexamethylene adipamide 
(65/25/10) copolymer as the polyphthalamide component. Again, talc was 
omitted and potassium acid phosphate was included as an aid in reducing 
drip. The formulations contained 42.82 wt % PPA-2, 18.42 wt % FR-1 
brominated polystyrene, 3.56 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.40 
wt % K.sub.2 HPO.sub.4 and 0.8 wt % metal oxide additive, together with 33 
wt % glass fiber. 
As will be readily understood, the mold temperatures and molding conditions 
were adjusted as required to accommodate the higher melt temperature of 
the terpolymer. 
The test results for the flame retardant terpolymer formulations are 
summarized in Table 11. 
TABLE 11 
__________________________________________________________________________ 
Effect of Various Oxides on Glass-filled PPA-2 
Polyphthalamides with FR-1 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
11 0.8 CaO-3 
59 Dark 
389.6 
5.1 
0.96 
29.0 
V0 
Tan No drip 
C11 
0.8 ZnO 
19 Gray 
294.3 
20.8 
0.79 
26.3 
V2 
4/5 
drips 
C12 
0.8 MgO 
32 Tan 
334.3 
35.2 
0.86 
26.4 
V2 
w/ 4/5 
gray drip 
area 
__________________________________________________________________________ 
Note: *Wt % based on total weight of filled; for abbreviations, details o 
components, see text. 
It will be seen from the data in Table 11 that adding calcium oxide to 
these filled flame-retardant terephthalamide-isophthalamide-adipamide 
terpolymer formulations provides improvement in color and in viscosity 
stability, crystallinity, and strength similar to the improvement seen for 
the filled PPA- 1 terephthalamide-adipamide copolymer formulations of 
Examples 1-5. 
Example 12 and Comparative Examples C13 and C14: PPA-3 Polyphthalamide 
Formulations 
In the following examples, polyphthalamide formulations were prepared and 
tested substantially as in Examples 1-5, but using PPA-3 hexamethylene 
terephthalamide/hexamethylene adipamide (55/45) copolymer as the 
polyphthalamide component. Again, talc was omitted and potassium acid 
phosphate was included as an aid in reducing drip. 
The formulations contained 41.41 wt % PPA-3, 19.60 wt % FR-1 brominated 
polystyrene, 3.79 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.28 wt % K2HPO4 
and 0.8 wt % metal oxide additive, together with 33 wt % glass fiber. The 
results of the testing are summarized in Table 12. 
TABLE 12 
__________________________________________________________________________ 
Effect of Various Oxides on Glass-filled PPA-3 
Polyphthalamides with FR-1 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
contr. 
None 
12 0.8 CaO-3 
70 Dark 
395.4 
14.7 
0.90 
28.0 
V0 
Tan No drip 
C13 
0.8 ZnO 
27 Gray 
361.0 
40.4 
0.76 
25.6 
V2 
4/5 
drips 
C14 
0.8 MgO 
29 Tan 
353.1 
75.1 
0.46 
21.8 
V0 
w/ no drip 
gray 
area 
__________________________________________________________________________ 
Example 13 and Comparative Examples C15 and C16: PPA-4 Polyphthalamide 
Formulations 
In the following examples, polyphthalamide formulations were prepared and 
tested substantially as in Examples 1-5, but using PPA-4, a polymer of 
terephthalic acid, adipic acid (75/25 mole ratio), hexamethylene diamine 
and 2-methylpentamethylene diamine (77/23 mole ratio) as the 
polyphthalamide component. Again, talc was omitted and potassium acid 
phosphate was included as an aid in reducing drip. The formulations of 
Example 13, C15 and C16 contained 41.42 wt % PPA-4, 19.6 wt % FR-1 
brominated polystyrene, 3.79 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.4 wt 
% K.sub.2 HPO.sub.4 and 0.8 wt % of the metal oxide additive, together 
with 33 wt % glass fiber. A control example without metal oxide was 
similarly prepared having 41.93 wt % PPA-4, 19.84 wt % FR-1 brominated 
polystyrene, 3.83 wt % Sodium Antimonate, 1.0 wt % PTFE, and 0.4 wt % 
K.sub.2 HPO.sub.4, together with 33 wt % glass fiber. 
The results of the testing for these formulations are summarized in Table 
13. 
TABLE 13 
__________________________________________________________________________ 
Effect of Various Oxides on Glass-filled PPA-4 
Polyphthalamides with FR-1 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
contr. 
None 76 gray, 
372.2 
NA 0.0 29.8 
V0 
dark 3/5 
drip 
13 0.8 CaO-3 
65 dark 
382.9 
45.6 
0.53 
28.5 
V0 
tan 4/5 
drip 
C15 
0.8 ZnO 
26 gray 
372.9 
68.9 
0.31 
27.1 
V0 
no 
drip 
C16 
0.8 MgO 
22 tan 
368.8 
NA 0.0 26.3 
V0 
w/ no 
gray drip 
__________________________________________________________________________ 
Example 14 and Comparative Examples C17 and C18: PPA-5 Polyphthalamide 
Formulations 
In the following examples, polyphthalamide formulations were prepared and 
tested substantially as in Examples 1-5, but using PPA-5 hexamethylene 
terephthalamide/caprolactam (70/30) copolymer as the polyphthalamide 
component. Again, talc was omitted and potassium acid phosphate was 
included as an aid in reducing drip. The formulations of Example 14, C17 
and C18 contained 41.42 wt % PPA-5, 19.6 wt % FR-1 brominated polystyrene, 
3.79 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.4 wt % K.sub.2 HPO.sub.4 and 
0.8 wt % of the metal oxide additive, together with 33 wt % glass fiber. A 
control example without metal oxide was similarly prepared having 41.93 wt 
% PPA-5, 19.84 wt % FR-1 brominated polystyrene, 3.83 wt % Sodium 
Antimonate, 1.0 wt % PTFE, and 0.4 wt % K.sub.2 HPO.sub.4, together with 
33 wt % glass fiber. 
The results of the testing for these formulations are summarized in Table 
14. 
TABLE 14 
__________________________________________________________________________ 
Effect of Various Oxides on Glass-filled PPA-5 
Polyphthalamides with FR-1 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
contr. 
None 87 Tan 
379.6 
NA 0.0 29.7 
V0 
w/ no drip 
gray 
14 0.8 CaO-3 
76 Tan 
379.0 
18.8 
0.94 
27.5 
V0 
w/ no drip 
gray 
C17 
0.8 ZnO 
59 Tan 
363.6 
12.6 
0.76 
29.4 
V0 
w/ no drip 
gray 
C18 
0.8 MgO 
75 Dark 
372.3 
14.9 
0.90 
26.9 
V0 
Tan no drip 
__________________________________________________________________________ 
Example 15 and Comparative Examples C19 and C20: PPA-6 Polyphthalamide 
Formulations 
In the following examples, polyphthalamide formulations were prepared and 
tested substantially as in Examples 1-5, but using PPA-6 hexamethylene 
terephthalamide/2-methyl pentamethylene terephthalamide (50/50) copolymer 
as the polyphthalamide component. Again, talc was omitted and potassium 
acid phosphate was included as an aid in reducing drip. The formulations 
of Example 15, C19 and C20 contained 41.42 wt % PPA-6, 19.6 wt % FR-1 
brominated polystyrene, 3.79 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.4 wt 
% K.sub.2 HPO.sub.4 and 0.8 wt % of the metal oxide additive, together 
with 33 wt % glass fiber. A control example without metal oxide was 
similarly prepared having 41.93 wt % PPA-4, 19.84 wt % FR-1 brominated 
polystyrene, 3.83 wt % Sodium Antimonate, 1.0 wt % PTFE, and 0.4 w5% 
K.sub.2 HPO.sub.4, together with 33 wt % glass fiber. 
The results of the testing for these formulations are summarized in Table 
15. 
TABLE 15 
__________________________________________________________________________ 
Effect of Various Oxides on Glass-filled PPA-6 
Polyphthalamides with FR-1 Flame Retardant 
Kayeness 
T (.degree.C.) 
.DELTA.Tc 
Tensile 
Ex. 
Additive 
t10/t5 1% Wt. 
3rd - 1st 
.DELTA.Hc 
Strength 
Burn 
No. 
wt % % Color 
Loss 
.degree.C. 
3rd/1st 
Kpsi 
Rating 
__________________________________________________________________________ 
contr. 
None 63 Gray 
377.8 
NA NA 30.2 
V0 
w/ 5/5 
dark drip 
15 0.8 CaO-3 
82 Gray 
383.4 
NA 0.0 29.6 
V0 
w/ 3/5 
dark drip 
C19 
0.8 ZnO 
72 Tan 
377.1 
58.1 
0.50 
28.7 
V2 
w/ 1/5 
gray drip 
area 
C20 
0.8 MgO 
87 Dark 
380.7 
6.5 
0.90 
28.7 
V0 
Tan no 
drip 
__________________________________________________________________________ 
Example 16 and Comparative Examples C21 and C22: Unfilled PPA-1 
Polyphthalamide Formulations 
In the following examples, neat resin polyphthalamide formulations were 
prepared and tested substantially following the procedures set forth in 
Examples 1-5, but omitting the glass fiber and the talc; potassium acid 
phosphate was included as an aid in reducing drip. The formulations of 
Example 16, C21 and C22 contained 64.63 wt % PPA-1, 27.8 wt % FR-1 
brominated polystyrene, 5.37 wt % Sodium Antimonate, 1.0 wt % PTFE, 0.4 wt 
% K.sub.2 HPO.sub.4 and 0.8 wt % of the metal oxide additive. 
The results of the testing for these formulations are summarized in Table 
16. 
TABLE 16 
______________________________________ 
Effect of Various Oxides on Unfilled PPA-1 Polyphthalamide 
with FR-1 Flame Retardant 
Kayeness .DELTA. Tc 
Ex. Additive t10/t5 3rd-1st 
.DELTA. Hc 
No. wt % % .degree.C. 
3rd/1st 
______________________________________ 
16 0.8 CaO-3 
67 20.4 0.84 
C21 0.8 ZnO 17 67.4 0.26 
C22 0.8 MgO 23 N.D.* 0.00 
______________________________________ 
Note: 
*N.D. not determinedno third peak developed. 
The addition of calcium oxide to the neat polyphthalamide resin formulation 
will be seen to be substantially more effective than either zinc oxide or 
calcium oxide in improving melt stability. Indeed, catastrophic loss in 
viscosity (Kayeness t10/t5) occured for formulations containing zinc oxide 
or magnesium oxide. The calcium oxide formulations also were better able 
to develop and retain crystallinity during fabrication, as shown by the 
DSC data. 
The invention set forth herein will thus be seen to be an improved 
flame-retardant polyamide formulation containing a polyphthalamide and a 
flame-retardant combination of a bromine-containing organic compound such 
as brominated polystyrene, polydibromostyrene or the like and an 
antimony-containing compound, preferably sodium antimonate, the 
improvement being adding calcium oxide in an amount effective to improve 
the thermal stability of the flame retardant polyamide formulation. The 
compositions according to the invention may be further characterized as 
containing, per 100 parts by weight of polyamide, from about 10 to 100 pbw 
of the bromine-containing organic compound, preferably a 
bromine-containing styrene polymer such as brominated polystyrene or 
polydibromostyrene, and from about 0.5 to about 50 pbw, preferably from 
about 1 to about 15 pbw of the antimony compound, preferably sodium 
antimonate, and from about 0.05 to about 50 pbw, preferably from about 0.1 
to about 10 pbw calcium oxide. The compositions of this invention may 
further contain from about 10 to about 60 wt % glass fiber, together with 
such other additives as are commonly employed in the art for compounding 
flame retardant polyamides. The polyphthalamide component of the 
composition may be further characterized as a copolyphthalamide comprising 
aliphatic diamine terephthalamide units and one or more additional 
carbonamide units, and preferably will be a copolyphthalamide containing 
aliphatic diamine terephthalamide units and aliphatic diamide units such 
as hexamethylene adipamide or the like. Particularly preferred are 
crystallizable copolyamides comprising at least 40 mole % terephthalamide 
units, still more preferably from about 50 to about 95 wt % 
terephthalamide units, together with one or more additional carbonamide 
units, preferably including units of at least one aliphatic diamide. As is 
well known, blends of aliphatic polyamides such as nylon 6,6 and 
polyphthalamides, including polyterephthalamides having no aliphatic 
diamide component, may also be crystalline, and such blends may also be 
found useful as the polyamide component for use in providing the improved 
flame-retardant formulations according to the invention. 
The invention may also be described as a method for improving the thermal 
stability of conventionally flame-retarded polyphthalamides comprising a 
polyphthalamide, a bromine-containing organic compound and a sodium 
antimonate whereby the flame retardant polyphthalamide is compounded with 
from about 0.2 to about 2 wt % calcium oxide. 
Inasmuch as the method of this invention is also directed to eliminating 
corrosive by-products created by the thermal decomposition of the flame 
retardant component of these formulations during processing at elevated 
temperatures, the method may be adapted for use with a variety of other 
high temperature resins. For example, a great many other high temperature 
polyamides are known in the art and commercially available including 
polytetramethylene adipamide which is available commercially under the 
trade designation Stanyl polyamide from the DSM Company, and the process 
of this invention may also be useful in providing improved fire-retarded 
resin formulations comprising such resins. The method of this invention 
may also be found useful for improving the stability of flame retardant 
formulations comprising other well-known high temperature polymers and 
copolymers such as polyphenylene oxide or the like. 
Although the invention has been set forth herein and illustrated by 
particular embodiments and examples, those skilled in the flame retardant 
arts will readily understand that further modifications may be made 
without departing from the scope and spirit of the invention, which is 
solely defined by the appended claims.