High modulus toughened polyamide composition

A thermoplastic composition is provided which comprises a polyamide, a grafted polymer of an isomonoolefin and an alkylstyrene, such as a maleic anhydride-grafted copolymer of isobutylene and para-methylstyrene, and optionally a polyolefin polymer.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to polyamide compositions having improved 
impact strength and high flexural modulus. 
2. Description of Information Disclosures 
Toughened thermoplastic polyamide compositions are known. See, for example, 
U.S. Pat. No. 4,174,358 which discloses a polyamide matrix and at least 
one other phase containing particles ranging from 0.01 to 10 microns of at 
least one specified polymer. 
U.S. Pat. No. 4,350,794 discloses a polyamide composition prepared by melt 
blending of a polyamide resin and a halobutyl elastomer. 
There is still a need to improve the impact strength of polyamide 
compositions, without substantial loss of the high flexural modulus of the 
polyamide. 
It has now been found that the incorporation of certain polymers in 
polyamide compositions will produce toughened polyamide compositions 
having improved impact strength without substantial loss of the high 
flexural modulus of the polyamide. 
SUMMARY OF THE INVENTION 
In accordance with the invention, there is provided a thermoplastic 
composition comprising a polymer blend of (1) a polyamide, and (2) a 
grafted polymer derived from 
(A) a copolymer selected from the group consisting of a copolymer of a 
C.sub.4 to C.sub.7 isomonoolefin and an alkylstyrene, a halogen-containing 
copolymer of a C.sub.4 to C.sub.7 isomonoolefin and an alkylstyrene, and 
mixtures thereof, and 
(B) an unsaturated organic compound selected from the group consisting of 
an unsaturated carboxylic acid, an unsaturated carboxylic acid derivative 
and mixtures thereof. 
In accordance with an other embodiment of the invention, the thermoplastic 
composition additionally comprises a polyolefin polymer.

DETAILED DESCRIPTION OF THE INVENTION 
The Polyamide Component 
Suitable thermoplastic polyamides (nylon) comprise crystalline or resinous, 
high molecular weight solid polymers including copolymers and terpolymers 
having recurring amide units within the polymer chain. Polyamides may be 
prepared by polymerization of one or more epsilon lactams such as 
caprolactam, pyrrolidone, lauryllactam and aminoundecanoic lactam, or 
amino acid, or by condensation of dibasic acids and diamines. Both 
fiber-forming and molding grade nylons are suitable. Examples of such 
polyamides are polycaprolactam (nylon-6), polylauryllactam (nylon 12), 
polyhexamethyleneadipamide (nylon-6,6), polyhexamethlene-azelamide 
(nylon-6,9), polyhexamethylenesebacamide (nylon-6, 10), 
polyhexamethylenesophthalamide (nylon-6,IP) and the condensation product 
of 11-aminoundecanoic acid (nylon-11); partially aromatic polyamides made 
by polycondensation of meta xylene diamine and adipic acid such as the 
polyamides having the structural formula: 
##STR1## 
Furthermore, the partially aromatic polyamide may be reinforced, for 
example, by glass fibers. Additional examples of satisfactory polyamides 
are described in Kirk-Othmer, Encyclopedia of Chemical Technology, v. 10, 
page 919, and Encyclopedia of polymer Science and Technology, Vol. 10, 
pages 392-414. Commercially available thermoplastic polyamides may be 
advantageously used in the practice of this invention, those having a 
softening point or melting point between 160.degree. C. to 275.degree. C. 
being preferred. 
The Grafted Polymer Component 
The grafted polymer component is a reaction product of a copolymer 
(Reactant A) and an unsaturated organic compound (Reactant B). 
Reactant A--The Copolymer 
Suitable copolymers of a C.sub.4 to C.sub.7 isomonoolefin and an 
alkylstyrene which may be a mono or a polyalkylstyrene, for use as a 
reactant to produce the polymers of the present invention comprise at 
least 0.5 weight percent of the alkylstyrene moiety. For elastomeric 
copolymer products, the alkylstyrene moiety may range from about 0.5 
weight percent to about 20 weight percent, preferably from about 1 to 
about 20 weight percent, more preferably from about 2 to about 20 weight 
percent of the copolymer. The preferred copolymers are copolymers of a 
C.sub.4 to C.sub.7 isomonoolefin and a para-alkylstyrene. 
The copolymers of the isomonoolefin and para-alkylstyrene copolymers 
suitable as reactant A of the present invention include copolymers of 
isomonoolefin having from 4 to 7 carbon atoms and a para-alkylstyrene, 
such as those described in European patent application 89305395.9 filed 
May 26, 1989, (Publication No. 0344021 published November 29, 1989). The 
copolymers have a substantially homogeneous compositional distribution and 
include the para-alkylstyrene moiety represented by the formula: 
##STR2## 
in which R and R.sup.1 are independently selected from the group 
consisting of hydrogen, alkyl preferably having from 1 to 5 carbon atoms, 
primary haloalkyl, secondary haloalkyl preferably having from 1 to 5 
carbon atoms, and mixtures thereof. 
The preferred isomonoolefin comprises isobutylene. The preferred 
para-alkylstyrene comprises para-methylstyrene. Suitable copolymers of an 
isomonoolefin and a para-alkylstyrene include copolymers having a number 
average molecular weight (M.sub.n) of at least about 25,000, preferably at 
least about 30,000, more preferably at least about 100,000. The copolymers 
also, preferably, have a ratio of weight average molecular weight 
(M.sub.w) to number average molecular weight (M.sub.n), i.e., M.sub.w 
/M.sub.n of less than about 6, preferably less than about 4, more 
preferably less than about 2.5, most preferably less than about 2. The 
brominated copolymer of the isoolefin and para-alkylstyrene obtained by 
the polymerization of these particular monomers under certain specific 
polymerization conditions now permit one to produce copolymers which 
comprise the direct reaction product (that is, in their as-polymerized 
form), and which have unexpectedly homogeneous uniform compositional 
distributions. Thus, by utilizing the polymerization set forth herein, the 
copolymers suitable for the practice of the present invention can be 
produced. These copolymers, as determined by gel permeation chromatography 
(GPC) demonstrate narrow molecular weight distributions and substantially 
homogeneous compositional distributions, or compositional uniformity over 
the entire range of compositions thereof. At least about 95 weight percent 
of the copolymer product has a para-alkylstyrene content within about 10 
wt. percent, and preferably within about 7 wt. percent, of the average 
para-alkylstyrene content for the overall composition, and preferably at 
least about 97 wt. percent of the copolymer product has a 
para-alkylstyrene content within about 10 wt. percent and preferably 
within about 7 wt. percent, of the average para-alkylstyrene content for 
the overall composition. This substantially homogeneous compositional 
uniformity thus particularly relates to the intercompositional 
distribution. That is, with the specified copolymers, as between any 
selected molecular weight fraction the percentage of para-alkylstyrene 
therein, or the ratio of para-alkylstyrene to isoolefin, will be 
substantially the same, in the manner set forth above. 
In addition, since the relative reactivity of para-alkylstyrene with 
isoolefin such as isobutylene is close to one, the intercompositional 
distribution of these copolymers will also be substantially homogeneous. 
That is, these copolymers are essentially random copolymers, and in any 
particular polymer chain the para-alkylstyrene and isoolefin units will be 
essentially randomly distributed throughout that chain. 
Suitable halogen-containing copolymers of a C.sub.4 to C.sub.7 
isomonoolefin and a para-alkylstyrene for use as reactant A to produce the 
polymers of the present invention include the halogen-containing 
copolymers corresponding to the previously described 
isomonoolefin--alkylstyrene copolymers which may be obtained by 
halogenating the previously described copolymers. The suitable 
halogen-containing copolymers comprise at least 0.5 weight percent of the 
alkylstyrene moiety. For elastomer copolymer products, the alkylstyrene 
moiety may range from about 0.5 weight percent to about 20 weight percent, 
preferably from about 1 to 20 weight percent, more preferably from about 2 
to 20 weight percent of the copolymer. The halogen content of the 
copolymers may range from above zero to about 7.5 weight percent, 
preferably from about 0.1 to about 7.5 weight percent. 
The preferred halogen-containing copolymers useful in the practice of the 
present invention have a substantially homogeneous compositional 
distribution and include the para-alkylstyrene moiety represented by the 
formula: 
##STR3## 
in which R and R.sup.1 are independently selected from the group 
consisting of hydrogen, alkyl preferably having from 1 to 5 carbon atoms, 
primary haloalkyl, secondary haloalkyl preferably having from 1 to 5 
carbon atoms, and mixtures thereof and X is selected from the group 
consisting of bromine, chlorine and mixtures thereof, such as those 
disclosed in European patent application 8930595.9 filed May 26, 1989, 
(Publication No. 0344021 published Nov. 29, 1989). Preferably, the halogen 
is bromine. 
Various methods may be used to produce the copolymers of isomonoolefin and 
para-alkylstyrene, as described in said European publication. Preferably, 
the polymerization is carried out continuously in a typical continuous 
polymerization process using a baffled tank-type reactor fitted with an 
efficient agitation means, such as a turbo mixer or propeller, and draft 
tube, external cooling jacket and internal cooling coils or other means of 
removing the heat of polymerization, inlet pipes for monomers, catalysts 
and diluents, temperature sensing means and an effluent overflow to a 
holding drum or quench tank. The reactor is purged of air and moisture and 
charged with dry, purified solvent or a mixture of solvent prior to 
introducing monomers and catalysts. 
Reactors which are typically used in butyl rubber polymerization are 
generally suitable for use in a polymerization reaction to produce the 
desired para-alkylstyrene copolymers suitable for use in the process of 
the present invention. The polymerization temperature may range from about 
minus 35.degree. C. to about minus 100.degree. C., preferably from about 
minus 40.degree. to about minus 80.degree. C. 
The processes for producing the copolymers can be carried out in the form 
of a slurry of polymer formed in the diluents employed, or as a 
homogeneous solution process. The use of a slurry process is, however, 
preferred, since in that case, lower viscosity mixtures are produced in 
the reactor and slurry concentration of up to 40 wt. percent of polymer 
are possible. 
The copolymers of isomonoolefins and para-alkylstyrene may be produced by 
admixing the isomonoolefin and the para-alkylstyrene in a copolymerization 
reactor under copolymerization conditions in the presence of a diluent and 
a Lewis acid catalyst. 
Typical examples of the diluents which may be used alone or in a mixture 
include propane, butane, pentane, cyclopentane, hexane, toluene, heptane, 
isooctane, etc., and various halohydrocarbon solvents which are 
particularly advantageous herein, including methylene chloride, 
chloroform, carbon tetrachloride, methyl chloride, with methyl chloride 
being particularly preferred. 
An important element in producing the copolymer is the exclusion of 
impurities from the polymerization reactor, namely, impurities which, if 
present, will result in catalyst poisoning or excessive molecular weight 
depression complexing with the catalyst or copolymerization with the 
isomonoolefins or the para-alkylstyrene, which in turn will prevent one 
from producing the para-alkylstyrene copolymer product useful in the 
practice of the present invention. Most particularly, these impurities 
include the catalyst poisoning material, moisture and other 
copolymerizable monomers, such as, for example, meta-alkylstyrenes and the 
like. These impurities should be kept out of the system. 
In producing the suitable copolymers, it is preferred that the 
para-alkylstyrene be at least 95.0 wt. percent pure, preferably 97.5 wt. 
percent pure, most preferably 99.5 wt. percent pure and that the 
isomonoolefin be at least 99.5 wt. percent pure, preferably at least 99.8 
wt. percent pure and that the diluents employed be at least 99 wt. percent 
pure, and preferably at least 99.8 wt. percent pure. 
The most preferred Lewis acid catalysts are ethyl aluminum dichloride and 
preferably mixtures of ethyl aluminum dichloride with diethyl aluminum 
chloride. The amount of such catalysts employed will depend on the desired 
molecular weight and the desired molecular weight distribution of the 
copolymer being produced, but will generally range from about 20 ppm to 1 
wt. percent and preferably from about 0.01 to 0.2 wt. percent, based upon 
the total amount of monomer to be polymerized. 
Halogenation of the polymer can be carried out in the bulk phase (e.g., 
melt phase) or either in solution or in a finely dispersed slurry. Bulk 
halogenation can be effected in an extruder, or other internal mixer, 
suitably modified to provide adequate mixing and for handling the halogen 
and corrosive by-products of the reaction. The details of such bulk 
halogenation processes are set forth in U.S. Pat. No. 4,548,995, which is 
hereby incorporated by reference. 
Suitable solvents for solution halogenation include the low boiling 
hydrocarbons (C.sub.4 to C.sub.7) and halogenated hydrocarbons. Since the 
high boiling point of para-methylstyrene makes its removal by conventional 
distillation impractical, and since it is difficult to completely avoid 
solvent halogenation, it is very important where solution or slurry 
halogenation is to be used that the diluent and halogenation conditions be 
chosen to avoid diluent halogenation, and that residual para-methylstyrene 
has been reduced to an acceptable level. 
With halogenation of para-methylstyrene/isobutylene copolymers, it is 
possible to halogenate the ring carbons, but the products are rather inert 
and of little interest. However, it is possible to introduce halogen 
desired functionality into the para-methylstyrene/isobutylene copolymers 
hereof in high yields and under practical conditions without obtaining 
excessive polymer breakdown, cross-linking or other undesirable side 
reactions. 
It should be noted that radical bromination of the enchained 
para-methylstyryl moiety in the copolymers for the practice of this 
invention can be made highly specific with almost exclusive substitution 
occurring on the para-methyl group, to yield the desired benzylic bromine 
functionality. The high specificity of the bromination reaction can thus 
be maintained over a broad range of reaction conditions, provided, 
however, that factors which would promote the ionic reaction route are 
avoided (i.e., polar diluents, Friedel-Crafts catalysts, etc.). 
Thus, solutions of the suitable para-methylstyrene/isobutylene copolymers 
in hydrocarbon solvents such as pentane, hexane or heptane can be 
selectively brominated using light, heat, or selected radical initiators 
(according to conditions, i.e., a particular radical initiator must be 
selected which has an appropriate half-life for the particular temperature 
conditions being utilized, with generally longer half-lives preferred at 
warmer halogenation temperatures) as promoters of radical halogenation, to 
yield almost exclusively the desired benzylic bromine functionality, via 
substitution on the para-methyl group, and without appreciable chain 
scission and/or cross-linking. 
This reaction can be initiated by formation of a bromine atom, either 
photochemically or thermally (with or without the use of sensitizers), or 
the radical initiator used can be one which preferentially reacts with a 
bromine molecule rather than one which reacts indiscriminately with 
bromine atoms, or with the solvent or polymer (i.e., via hydrogen 
abstraction). The sensitizers referred to are those photochemical 
sensitizers which will themselves absorb lower energy photons and 
disassociate, thus causing, in turn, disassociation of the bromine, 
including materials such as iodine. It is, thus, preferred to utilize an 
initiator which has a half life of between about 0.5 and 2500 minutes 
under the desired reaction conditions, more preferably about 10 to 300 
minutes. The amount of initiator employed will usually vary between 0.02 
and 1 percent by weight on the copolymer, preferably between about 0.02 
and 0.3 percent. The preferred initiators are bis azo compounds, such as 
azo bis isobutyronitrile (AIBN), azo bis (2,4 dimethyl valero) nitrile, 
azo bis (2 methyl butyro) nitrile, and the like. Other radical initiators 
can also be used, but it is preferred to use a radical initiator which is 
relatively poor at hydrogen abstraction, so that it reacts preferentially 
with the bromine molecules to form bromine atoms rather than with the 
copolymer or solvent to form alkyl radicals. In those cases, there would 
then tend to be resultant copolymer molecular weight loss, and promotion 
of undesirable side reactions, such as cross-linking. The radical 
bromination reaction of the copolymers of para-methylstyrene and 
isobutylene can be highly selective, and almost exclusively produces the 
desired benzylic bromine functionality. Indeed, the only major side 
reaction which appears to occur is disubstitution at the para-methyl 
group, to yield the dibromo derivative, but even this does not occur until 
more than about 60 percent of the enchained para-methylstyryl moieties 
have been monosubstituted. Hence, any desired amount of benzylic bromine 
functionality in the monobromo form can be introduced into the above 
stated copolymers, up to about 60 mole percent of the para-methylstyrene 
content. 
It is desirable that the termination reactions be minimized during 
bromination, so that long, rapid radical chain reactions occur, and so 
that many benzylic bromines are introduced for each initiation, with a 
minimum of the side reactions resulting from termination. Hence, system 
purity is important, and steady-state radical concentrations must be kept 
low enough to avoid extensive recombination and possible cross-linking. 
The reaction must also be quenched once the bromine is consumed, so that 
continued radical production with resultant secondary reactions (in the 
absence of bromine) do not then occur. Quenching may be accomplished by 
cooling, turning off the light source, adding dilute caustic, the addition 
of a radical trap, or combinations thereof. 
Since one mole of HBr is produced for each mole of bromine reacted with or 
substituted on the enchained para-methylstyryl moiety, it is also 
desirable to neutralize or otherwise remove this HBr during the reaction, 
or at least during polymer recovery in order to prevent it from becoming 
involved in or catalyzing undesirable side reactions. Such neutralization 
and removal can be accomplished with a post-reaction caustic wash, 
generally using a molar excess of caustic on the HBr. Alternatively, 
neutralization can be accomplished by having a particulate base (which is 
relatively non-reactive with bromine) such as calcium carbonate powder 
present in dispersed form during the bromination reaction to absorb the 
HBr as it is produced. Removal of the HBr can also be accomplished by 
stripping with an inert gas (e.g., N.sub.2) preferably at elevated 
temperatures. 
The brominated, quenched, and neutralized para-methylstyrene/isobutylene 
copolymers can be recovered and finished using conventional means with 
appropriate stabilizers being added to yield highly desirable and 
versatile functional saturated copolymers. 
In summary, halogenation to produce a copolymer useful in the present 
invention is preferably accomplished by halogenating an 
isobutylene-para-methylstyrene copolymer using bromine in a normal alkane 
(e.g., hexane or heptane) solution utilizing a bis azo initiator, e.g., 
AIBN or VAZO.RTM. 52: 2,2'-azobis(2,4-dimethylpentane nitrile), at about 
55.degree. to 80.degree. C. for a time period ranging from about 4.5 to 
about 30 minutes, followed by a caustic quench. The recovered polymer is 
washed in basic water wash and water/isopropanol washes, recovered, 
stabilized and dried. 
Reactant B--The Unsaturated Organic Compound 
Suitable unsaturated organic compound for use as reactant with the 
copolymer include unsaturated carboxylic acids, unsaturated carboxylic 
acid derivatives and mixtures thereof. The carboxylic acid may be a mono 
or polycarboxylic acid, preferably having from 3 to 12 carbon atoms. By 
way of example, the unsaturated carboxylic acid may be maleic acid, 
fumaric acid, citraconic acid, mesaconic acid, itaconic acid, himic acid, 
acetylenedicarboxylic acid and mixtures thereof. The preferred carboxylic 
acid is maleic acid. The unsaturated carboxylic acid derivative may be a 
cyclic acid anhydride, an amide, an imide, an ester and mixtures thereof. 
Suitable cyclic acid anhydrides include maleic anhydride, citraconic 
anhydride, itaconic anhydride, and himic anhydride. The preferred 
anhydride is maleic anhydride. 
Suitable esters include mono- and di-esters of diacids specified above, 
e.g. monomethyl maleate, dimethyl maleate, diethyl maleate, diphenyl 
maleate, dibutyl fumarate. 
Suitable amides include mono- and di-amides of diacids specified above, 
e.g. maleamic acid, N-methylmaleamic acid, maleanilic acid. 
Suitable imides include imides of diacids specified above, e.g. maleimide, 
N-methylmaleimide, N-phenylmaleimide. 
The preferred carboxylic acid derivatives are selected from the group 
consisting of maleic anhydride, a dialkyl maleate, itaconic anhydride, 
himic anhydride, an alkylmaleamide, an N-alkylmaleimide, an alkylmaleate 
and mixtures thereof. 
The reactant (B) derived moieties may be present in the grafted polymer 
component of the present invention in an amount ranging from about 0.5 to 
0.001 millimole (mmole) per gram, preferably from about 0.2 to 0.002 mmole 
per gram, more preferably from about 0.1 to 0.005 mmole per gram of the 
grafted polymer product. 
The grafted polymer component of the present invention is prepared by 
reacting a copolymer, Reactant A previously described, with an unsaturated 
organic compound, Reactant B previously described, in the presence of a 
free radical initiator at grafting reaction conditions in a reaction zone. 
When it is desired to graft a derivative of an acid or anhydride onto the 
copolymer (Reactant A), instead of reacting the copolymer with the acid 
derivative, the copolymer (Reactant A) may be reacted with the unsaturated 
carboxylic acid or anhydride and the resulting carboxylic acid grafted or 
carboxylic acid anhydride grafted polymer may subsequently be reacted with 
a desired functional group-containing compound. For example, the maleic 
anhydride grafted copolymer may be reacted with an amine, RNH.sub.2, as 
shown in the following schematic equation wherein --MM-- denotes the 
polymer chain and R is an alkyl group: 
##STR4## 
The copolymer of isobutylene and an alkylstyrene or the corresponding 
halogenated copolymer (Reactant A) is contacted with Reactant B in the 
presence of a free radical initiator which may be a chemical compound or 
radiation. Suitable free radical initiators include (1) thermally 
decomposable compounds which generate radicals such as azo compounds or 
organic peroxides; (2) compounds which generate free radicals by 
non-thermal methods such as photochemical or redox processes; (3) 
compounds which have inherent radical character such as molecular oxygen; 
or (4) electromagnetic radiation such as X-rays, electron beams, visible 
light, ultraviolet-light. 
Suitable organic peroxide compounds include hydroperoxides, dialkyl 
peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, 
peroxyketals, ketone peroxides and organosulfonyl peroxides. 
Preferably, the free radical initiator is an organic peroxide compound 
having a half-life, at the reaction temperature, of less than one tenth of 
the reaction/residence time employed. 
When the free radical initiator is a initiator compound to Reactant B may 
range from 0.001:1 to 1:1, preferably from 0.01:1 to 0.1:1. 
Desirably, the molar amount of Reactant B expressed in mmoles per gram, in 
the contacting zone may be 1 to 10 times the molar amount of these 
components as is desired in the final grafted copolymer. Thus, when the 
molar amount of B in the grafted copolymer is 0.05 mmoles per gram of 
product polymer, the amount of B introduced in the reaction zone is 
suitably from about 0.05 to about 0.5 mmoles per gram of component A plus 
component B present in the reaction mixture. 
The grafting reaction may be conducted in the absence of a diluent or in 
the presence of a diluent. 
When a diluent is present in the reaction zone, suitable diluents include 
saturated aliphatic hydrocarbons, aromatic hydrocarbons, and 
perhalogenated hydrocarbons. 
Preferably, the grafting reaction to produce the grafted polymer component 
of the present invention is conducted in the absence of a diluent and in 
the melt phase, wherein the copolymer (Reactant A) is in the molten phase. 
The reaction temperature is chosen to be appropriate for the initiator 
used. 
Suitable reaction conditions include a temperature ranging from about 
0.degree. C. to about 300.degree. C. The suitable reaction temperature 
will vary according to the free radical initiator used. When an azo 
compound is used as the initiator, suitable temperatures will generally 
range from about 25.degree. to 100.degree. C. When an organic peroxide is 
used as initiator, suitable temperatures range from about 25.degree. to 
about 250.degree. C. Higher temperatures may be used for other types of 
free radical initiators. When the reaction is conducted in the presence of 
a diluent, i.e. solution processes, the reaction temperature will 
generally be below 150.degree. C. For melt phase processes, (i.e., bulk 
phase processes), the reaction temperature may range from about 25.degree. 
C. such as in conventional electron beam irradiation equipment to about 
250.degree. C. such as in polymer mixing equipment. The process for 
producing the grafted polymers of the present invention may be conducted 
as a batch process or as a continuous process. 
The reaction is performed in a suitable reaction zone which may be a 
polymer mixing device such as a Banbury mixer, a single or multiple screw 
extruder and the like for melt phase polymers or a glass flask, metal tank 
or tube when the process is conducted in the presence of a diluent. 
When the molten copolymer itself is the reaction medium, uniform dispersion 
of the grafting agent and of the initiator is preferably performed by 
predispersion or by the incorporation of suitable mixing elements into the 
reactor (e.g., incorporation of mixing screw sections in an extruder). 
When electromagnetic radiation is used, dispersion of the initiator will 
include uniform exposure of all parts of the copolymer or copolymer 
solution to the beam. 
In a preferred embodiment, the grafting process to produce the grafted 
polymer of the invention is carried out in a twin screw extruder having, 
in sequence, screw elements, which will (i) heat the polymer by shear and 
compression to or close to the desired reaction temperature, (ii) mix the 
copolymer at or close to reaction temperature with the grafting agent, 
(iii) mix the copolymer containing the grafting agent with the initiator, 
(iv) allow appropriate residence time for the grafting reaction, (v) allow 
venting of unreacted grafting agent and initiator coproducts, (vi) allow 
mixing of any desired stabilizers or additives and (vii) forward the 
reacted, vented stabilized polymer to an appropriate finishing device 
(e.g. drumming device, baler, pelletizer, etc.). 
In the composition of the present invention, the polyamide component may 
suitably be present in an amount ranging from about 15 to about 95 weight 
percent, preferably from about 65 to about 85 weight percent, and the 
grafted polymer component may be present from about 5 to about 85 weight 
percent, preferably from about 15 to about 35 weight percent, based on the 
weight percent of the polymer blend. 
The term "polymer blend" is used herein to denote the blend of at least one 
polyamide, at least one grafted polymer and any other optional polymers 
(elastomer or non-elastomer) that may be a component of the composition. 
The compositions of the present invention may comprise an additional 
optional polyolefin polymer component. 
The Optional Polyolefin Polymer Component 
Suitable optional polyolefin components include: 
(i) Reactant (A) of the grafted polymer component, that is, the copolymer 
of a C.sub.4 to C.sub.7 isomonoolefin and an alkylstyrene previously 
described, preferably a copolymer of a C.sub.4 to C.sub.7 isomonoolefin 
and a para-alkylstyrene, more preferably a copolymer of isobutylene and 
para-methylstyrene; 
(ii) a polyolefin polymer which may be a homopolymer such as polyethylene 
and polypropylene, or a heteropolymer such as ethylene and at least one 
higher alpha olefin such as C.sub.2 to C.sub.16 alpha olefins, for 
example, propylene, butene, 1-pentene, 1-hexene, 1-octene, 1-dodecene and 
mixtures thereof. The preferred heteropolymer is a copolymer of ethylene 
and propylene. 
(iii) mixtures of (i) and (ii). 
The optional polyolefin may be a high density polyolefin, such as high 
density polyethylene. 
The preferred optional polyolefin polymers include reactant (A) of the 
grafted polymer component, described above, and polyethylene, 
polypropylene and ethylene propylene copolymers, and mixtures thereof. 
The more preferred optional polyolefin polymer is a copolymer of 
isobutylene and para-methylstyrene. 
Suitable compositional ranges of the polymer blend for a composition 
comprising at least 3 polymer components include: 
1. The polyamide component ranging from about 60 to about 99 percent by 
weight. 
2. The grafted polymer component ranging from about 1 to about 40 percent 
by weight. 
3. The polyolefin polymer component ranging from about above 0 to about 39 
percent by weight. 
Preferred compositional ranges for the 3-polymer component blend include: 
1. The polyamide component ranging from about 70 to about 95 percent by 
weight. 
2. The grafted polymer component ranging from about 5 to about 30 percent 
by weight. 
3. The polyolefin polymer component ranging from about 0 to about 25 
percent by weight. 
More preferred compositional ranges for the polymer blend include: 
1. The polyamide component ranging from about 80 to about 90 percent by 
weight. 
2. The grafted polymer component ranging from about 10 to about 20 percent 
by weight. 
3. The polyolefin polymer component ranging from above 0 to about 15 
percent by weight. 
The polymer blend of the present invention may comprise from about 25 to 
about 100 weight percent of the overall composition. 
In addition to its polymer components, the composition of the present 
invention may comprise fillers and additives such as antioxidants, 
antiozonants, stabilizers, rubber processing oils, lubricants, waxes, 
foaming agents, flame retardants, pigments, and other known processing 
aids. The pigments and fillers may comprise up to 30 weight percent of the 
total composition based on the polymer components plus additives. 
The composition of the present invention is prepared by mixing the 
polyamide component, the grafted polymer and optional other polymers at a 
temperature sufficient to soften the polyamide component and any other 
optional polymer, for example, at a temperature of at least about the 
melting point of the polyamide, in conventional mixing equipment such as a 
Brabender.RTM. mixer or an extruder. Preferably, the blending of the 
components is performed in an extruder under shearing conditions. The 
non-polymeric components may be added at any stage of the mixing step, 
that is, before, during or after mixing the polymers. 
The secant flexural modulus of the thermoplastic composition may range from 
about 15,000 kg/cm.sup.2 to about 60,000 kg/cm.sup.2, preferably from 
about 20,000 kg/cm.sup.2 to about 30,000 kg/cm.sup.2, measured according 
to ASTM D790 at 1% strain. 
Preferred Embodiments 
The following examples are presented to illustrate the invention. All parts 
and percentages herein are by weight unless specifically stated otherwise. 
In examples 1 and 2, the compositions in accordance with the present 
invention and the comparative compositions were mixed in a 0.8" Welding 
Engineers counter-rotating twin screw extruder fitted with a strand die at 
the extruder exit. The extruder strands were then cooled in a water bath 
before being reduced by a pelletizer into approximately 1/8" by 1/8" 
pellets. The polyamide resins were dried at 150.degree. F. under vacuum 
for at least four hours before compounding. All pelletized compositions 
were again dried in the same drier under the same conditions for at least 
four hours to remove surface moisture before being molded into various 
test specimens on a 15 ton Boy.RTM. injection molding machine. 
The abbreviations and/or trademarks used in the following examples are 
shown in Table III. The test methods used to measure the properties are 
shown in Table IV. 
EXAMPLE 1 
Table I shows four compositions of polyamide 6,6. Composition A was a 80/20 
blend of Celanese Nylon 1001 and a maleated copolymer of isobutylene and 
para-methylstyrene herein designated Copolymer T, and Composition B was an 
identical blend in which the Celanese Nylon 1001 was replaced by another 
brand of PA 6,6 Zytel 101. Composition C was an 80/20 blend of Celanese 
Nylon 1001 and a copolymer of isobutylene and para-methylstyrene herein 
designated Copolymer Y, and Composition D was the unmodified Celanese 
Nylon 1001 control. A small amount of thermal stabilizer, Irganox B-215 
was added to each blend to minimize degradation. Comparison of 
Compositions C and D indicates that impact improvement. In Compositions A 
and B, the addition of 20% of Copolymer T caused the room temperature 
notched Izod to increase ten fold, while still maintaining a high flexural 
modulus in the 280,000 psi range (i.e. 19,700 kg/cm.sup.2) or about 70% of 
the flexural modulus of the polyamide component. 
Copolymer T comprised 0.10 millimole (mmole) per gram or 1.0 weight percent 
of moieties derived from maleic anhydride and 10 weight percent of 
moieties derived from para-methylstyrene. 
Copolymer Y comprised 2.4 mole percent of moieties derived from 
para-methylstyrene and had a Mooney viscosity (1+8) of 31 at 125.degree. 
C. 
Compositions A and B are compositions in accordance with the present 
invention. 
EXAMPLE 2 
Table II shows five compositions of polyamide 6. Composition E was an 80/20 
blend of Capron brand of PA 6 with Copolymer T. In Composition F, 5% of 
Copolymer T was replaced with equal amount of Copolymer Y, and in 
Composition G, 10% Copolymer T was replaced with Copolymer Y. Composition 
H shows that all 20% of Copolymer T was replaced by Copolymer Y. Finally, 
Composition I was the unmodified PA 6. A small amount of thermal 
stabilizer, Irganox B-215, was added to each blend to minimize 
degradation. Compositions H and I a gains showed that Copolymer Y alone 
was not suitable as an impact modifier. On the other hand, Copolymer T and 
a combination of Copolymer T and Copolymer Y were very good impact 
modifiers for PA 6. It should be noted that in Compositions E, F, and G, 
impact improvement was not at the expense of corresponding reduction of 
flexural modulus. Addition of 20% Copolymer T or a mixture of Copolymer T 
and Copolymer Y only slightly reduced the flexural modulus from 380,000 
psi (i.e. 26,700 kg/cm.sup.2) to about 310,000 psi (i.e. 21,800 
kg/cm.sup.2) or over about 80 percent of the flexural modulus of the 
polyamide component. 
TABLE I 
______________________________________ 
COPOLYMER T/PA 6,6 BLENDS 
(DRY-AS-MOLDED TEST SPECIMENS) 
Composition A B C D 
______________________________________ 
Celanese 1001 80 80 100 
Zytel 101 80 
Copolymer T 20 20 
Copolymer Y 20 
Irganox B215 0.1 0.1 0.1 
Property 
Tensile 
Tensile Stress @ Y, Kpsi 
7.5 7.6 8.2 11.5 
Tensile Stress @ B, Kpsi 
7.3 7.2 8 12 
Elong. @ Y, % 6.6 7.3 8.2 8 
Elong. @ B, % 23 31 19.3 50 
Flexural Modulus, Kpsi 
284 294 335 420 
Notched Izod, 1/8", ft-lb/in 
R.T. 12.9 9.5 1.2 1 
0.degree. C. 2.7 2.7 
-20.degree. C. 1.9 1.9 0.6 0.6 
______________________________________ 
TABLE II 
______________________________________ 
COPOLYMER T/PA 6 BLENDS 
(DRY-AS-MOLDED TEST SPECIMENS) 
Composition E F G H I 
______________________________________ 
CAPRON 8209F 80 80 80 80 100 
Copolymer T 20 15 10 
Copolymer Y 5 10 20 
IRGANOX B-215 
0.1 0.1 0.1 0.1 
Property 
Tensile 
Tensile Stress @ Y, 
7.7 7.5 7.7 7.6 10.5 
Kpsi 
Tensile Stress @ B, 
6.3 6.1 6.3 6.9 7.4 
Kpsi 
Elong. @ Y, % 
7.3 7.3 7.3 7.3 8.5 
Elong. @ B, % 
49 107 78 16 480 
Flexural Modulus, 
323 322 311 255 380 
Kpsi 
Notched Izod, 1/8", 
ft-lb/in 
R.T. 14.4 16 15.1 2 1.1 
0.degree. C. 2.8 3.1 3 1.6 1.6 
-10.degree. C. 
2.3 2.5 2.3 
-20.degree. C. 
1.7 2.3 1.9 1.3 0.7 
-30.degree. C. 
1.6 1.9 1.6 
______________________________________ 
TABLE III 
______________________________________ 
ABBREVIATIONS AND TRADEMARKS 
Ingredient Description 
______________________________________ 
Celanese Nylon 1001 
Polyamide 6,6 (PA 6,6) 
Hoechst-Celanese 
Zytel 101 Polyamide 6,6 (PA 6,6) 
E. I. DuPont 
Capron 8209F Polyamide 6 (PA 6) 
Allied Signal 
Irganox B-215 33/67 Blend of Irganox 1010 
Ciba Geigy and Irgafos 168 
Irganox 1010 Tetrakis (methylene (3,5-di- 
Ciba Geigy tert-butyl-4-hydroxy- 
hydrocinnamate) methane 
Irgafos 168 Tris (2,4-di-tert-butyl- 
Ciba Geigy phenyl) phosphate 
______________________________________ 
TABLE IV 
______________________________________ 
TEST METHOD 
Test Test Method 
______________________________________ 
Tensile Strength, psi 
ASTM D-638 
Elongation, % ASTM D-638 
Flexural Modulus, psi 
ASTM D-790 
Notched Izod ASTM D-256 
Impact, ft-lb/in 
Mooney Viscosity ASTM D-1646 
______________________________________ 
EXAMPLE 3 
Polyamide 6 (Allied Capron 8209F) was dried in an oven at 100.degree. C. 
overnight. The dried polyamide (200 g) was charged to a 300 ml Brabender 
mixer and brought to about 250.degree. C. by a combination of internal 
mixing and external heating. Copolymer T (50 g) was added and mixing 
continued for 3 minutes at 250.degree. C. The discharged blend was allowed 
to cool to room temperature in a desiccator and then ground. Test 
specimens were made using a Boy.RTM. injection molding machine. The blend 
had an Izod impact strength at room temperature of 10.7 ft.lbs/in. and at 
0.degree. C. of 2.5 ft.lbs/in. Its flexural modulus was 295 kpsi (i.e. 
20,700 kg/cm.sup.2). This composition (J) is in accordance with the 
present invention. 
EXAMPLE 4 
The following composition was mixed in the 0.8" Welding Engineers twin 
screw extruder after the manner of example 1: polyamide 6, Capron 8209F, 
(80%), Copolymer T (15%), high density polyethylene, grade HD 6705.39 from 
Exxon Chemicals, USA, (5) and Irganox B-215 (0.1 phr). 
Test specimens were made using a Boy.RTM. injection molding machine. The 
blend, herein designated Composition K, had a notched Izod impact strength 
of 15.5 ft. lbs/inch. Comparison with the data for compositions E and F 
above indicates that high density polyethylene was effective as the 
optional polyolefin polymer of the present invention and comparable in its 
effect to Copolymer Y. Composition K, which is a composition in accordance 
with the present invention, had a flexural modulus of 293 kpsi (i.e., 
20,600 kg/cm.sup.2).