Blends of polyesteramides and polyamides

Disclosed are novel blends comprising segmented polyesteramides with minor amounts of aliphatic polyamides. The blends are characterized by good physical properties including improved elongation and solvent resistance over the base polyesteramides. The polymers so obtained find utility in the making of seals, gaskets, bushings, and the like.

FIELD OF THE INVENTION 
This invention relates to modified polyesteramides and is more particularly 
concerned with blends of segmented polyesteramides with aliphatic 
polyamides. 
DESCRIPTION OF THE PRIOR ART 
Segmented polyesteramides of the type disclosed in U.S. Pat. No. 4,129,715 
are characterized by a combination of very useful properties such as good 
high temperature resistance, wide range of hardness values, and excellent 
tensile properties including good elongation. These properties are 
combined in materials which are readily injection moldable into 
complicated shapes. Inconveniently, when one needs to increase the 
hardness of the polyesteramide a whole new polymer must be prepared 
containing a higher proportion of hard segment in the recurring units. 
Increasing the hardness this way also tends to lower the other physical 
properties. 
Zappa et al (U.S. Pat. No. 4,473,688) have modified the low temperature 
impact strengths of nylon polyamides by incorporating in the polymer a 
very small proportion (3 to 10 percent by weight) of a polyesteramide 
which differs markedly from the polyesteramides of U.S. Pat. No. 4,129,715 
by having as the hard segment in the recurring units one which is derived 
from a low molecular weight alpha, omega-dihydroxyalkane. 
We have now found that, by incorporating into the polyesteramides of the 
type set forth in U.S. Pat. No. 4,129,715 minor amounts of aliphatic 
polyamides, it is possible not only to increase their hardness but also in 
many cases to improve their solvent resistance as well as maintaining the 
other good physical properties. 
Surprisingly, the percent elongation of the molded parts made from the 
blends are higher than the virgin polyesteramides. This unexpected result 
occurs in spite of the fact that the polyamide being added has elongation 
values far below the levels of the virgin polyesteramide itself. 
SUMMARY OF THE INVENTION 
The present invention relates to novel polymer blends comprising 
(a) from about 99 to about 50 percent by weight of a segmented 
polyesteramide characterized by a recurring unit of the formula (I) 
##STR1## 
wherein R is selected from the class consisting of arylene of the 
formulae: 
##STR2## 
and mixtures thereof, A is the residue of a polymeric diol HOAOH having a 
molecular weight from about 400 to about 4000, B is the residue of a 
dicarboxylic acid HOOC--B--COOH selected from the class consisting of 
aliphatic dicarboxylic acids having from 6 to 14 carbon atoms, inclusive, 
and isophthalic and terephthalic acids, m has a mean value of not more 
than 1 but greater than 0, D is the residue of a dicarboxylic acid 
HOOC--D--COOH such that the melt temperature of the hard segment is not 
greater than 300.degree. C., and x is a number having an average value 
from zero to 10; and 
(b) from about 1 to about 50 percent by weight of an aliphatic polyamide. 
The term "polymeric diol" which is used herein to characterize residue A in 
formula (I) above is inclusive of polyether and polyester diols having 
molecular weights within the stated range. Illustrative of polyether diols 
are the poly(alkylene ether)diols obtained by polymerizing one or more 
cyclic ethers such as ethylene oxide, propylene oxide, butylene oxide and 
tetrahydrofuran. The poly(alkylene ether)diols are inclusive of 
polyethylene glycol, polypropylene glycol, poly(tetramethylene glycol), 
polypropylene glycols capped with ethylene oxide, random copolymers of 
ethylene oxide and propylene oxide, and adducts of ethylene oxide, 
propylene oxide and like alkylene oxides with homopolymers of conjugated 
alkadienes such as butadiene, isoprene and the like, and copolymers of 
said alkadienes with vinyl monomers such as acrylonitrile, 
methacrylonitrile, styrene, and the like. Preferred polyether diols for 
use in preparing the polyesteramides are poly(tetramethylene glycol) and 
ethylene oxide-capped polypropylene glycols wherein the ethylene oxide 
content is within the range of about 5 percent to about 40 percent. 
Illustrative of the polyester diols are those obtained by reacting a 
dicarboxylic acid such as adipic, suberic, azelaic, glutaric acids and the 
like, with an excess, over the stoichiometric amount, of a dihydric 
alcohol such as ethylene glycol, propylene glycol, 1,4-butanediol, 
1,6-hexanediol and the like, including mixtures of two or more such diols. 
The term "aliphatic dicarboxylic acids having from 6 to 14 carbon atoms" 
means the acids represented by the formula HOOC--C.sub.n H.sub.2n --COOH 
wherein the total number of carbon atoms, including those in the 
carboxylic groups, lies within the stated range and CnH.sub.2n represents 
straight or branched chain alkylene having the appropriate carbon atom 
content. Illustrative of such acids are adipic, pimelic, suberic, azelaic, 
sebacic, 1,11-undecandioic, and 1,12-dodecandioic, brassylic, 
.alpha.-methyladipic, .alpha.,.alpha.-dimethyladipic, 
.alpha.-ethylpimelic, .alpha.-ethyl-.alpha.-methylpimelic, 
.beta.,.beta.'-diethyl-.beta.,.beta.'-dimethylsuberic, 
2,2,4-trimethyladipic, 2,4,4-trimethyladipic, 
.alpha.,.alpha.-dimethylazelaic and 
.alpha.,.alpha.,.alpha.',.alpha.'-tetramethylsebacic acids. 
The term "dicarboxylic acid HOOC--D--COOH" is inclusive of straight and 
branched chain aliphatic dicarboxylic acids which do not raise the melt 
temperature of the hard section of the polymer into which they are 
introduced above about 300.degree. C. Illustrative of such acids are 
adipic, azelaic, sebacic, suberic, 1,11-undecandioic, 1,12-dodecandioic, 
brassylic, and trimethyladipic acids. Particularly preferred are azelaic 
and adipic as well as a mixture of approximately equimolar amounts of 
these two acids. 
The term "aliphatic polyamide" means a composition of a linear polymer 
having the carbonamide group --CONH (hereinafter --AB--) linked in either 
--AABB--or --AB--relationship and wherein the divalent radicals within the 
respective monomer units are C.sub.2 to C.sub.12 alkylene such as 
ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, 
nonylene, decylene, undecylene, dodecylene, and isomeric forms thereof. 
DETAILED DESCRIPTION OF THE INVENTION 
The invention is directed broadly to a blend of the segmented 
polyesteramide defined above with a minor amount of an aliphatic 
polyamide. 
The segmented polyesteramide component of the blends of the invention can 
be any of those polyesteramides which are described in U.S. Pat. No. 
4,129,715, the disclosure of which is incorporated herein by reference. 
Detailed procedures for the preparation of the polyesteramides are given 
in the aforesaid patent and will not be repeated herein for the interest 
of brevity. 
The preferred polyesteramides for use in preparing the polymer blends of 
the invention are those having the following limitations in the recurring 
unit of formula (I): R is methylenebis(phenylene) particularly 
4,4'-methylenebis(phenylene); A is the residue of a polyester diol which 
is the hydroxyl terminated product of reaction of adipic, azelaic, or 
1,12-dodecanedioic acid with an excess of 1,4-butanediol, or 
1,6-hexanediol; B and D are the residues of an aliphatic dicarboxylic 
acid, particularly adipic or azelaic acids, and mixtures thereof; it will 
be readily understood that, if, instead of using the excess of the diol 
when preparing the polyester, an excess of the acid is employed then a 
larger segment of the preferred recurring unit is obtained directly which 
would include the residue B of the dicarboxylic acid; and x has a value 
greater than 0. 
The linear aliphatic polyamide component defined above of the present 
blends can be any of the well-known crystalline aliphatic polyamides which 
are readily available commercially. Generally speaking, such aliphatic 
polyamides have a number average molecular weight, as determined by known 
end-group analysis, of from about 5,000 to about 50,000. Illustrative of 
the polyamides but not limiting thereof are nylon 6 (polycaprolactam), 
nylon 66 [poly(hexamethyleneadipamide)], nylon 610 
[poly(hexamethylenesebacamide)], nylon 3 [poly(.beta.- alanine)], nylon 4 
(polybutyrolactam), nylon 612 [poly(hexamethylenedodecanamide)], nylon 11 
(polyundecanolactam), and nylon 12 (polylaurolactam). A preferred group of 
polyamides comprises nylon 6 and nylon 66. 
The polyamides generally have an inherent viscosity of at least 0.5 dl/g. 
measured as a 0.5 percent w/w solution in m-cresol. 
The proportions in which the polyesteramide component and polyamide 
component are employed in the blends is generally within the range of 
about 99 to about 50 percent by weight of polyesteramide with the 
complementary 1 to 50 percent comprising the polyamide. 
Preferably, the polyesteramide falls within 95 to 60 percent by weight with 
the polyamide being 5 to 40 percent by weight. 
The blends can be prepared in any convenient manner. For example, by 
bringing together the two components in solid form and dry-blending using 
conventional means such as a barrel mixer, a tumble mixer, and the like, 
followed by fluxing or melt-blending in an appropriate apparatus such as a 
Banbury type internal mixer, rubber mill, twin screw compounder, and the 
like. Preferably, the two components are brought together and processed in 
an appropriate melt extruder from which the blend is extruded in the form 
of strands and the like which are then pelletized for injection molding 
purposes. Standard techniques and apparatus well-known in the art can be 
used for these purposes. 
The compositions of the invention can also incorporate various additives 
such as fillers, antioxidants, pigments, fire retardants, plasticizers, 
reinforcing agents such as glass fiber and the like, which are commcnly 
employed in the art in polyesteramide compositions. The additives are 
readily incorporated into the blends during the formation of the latter 
using any of the procedures described above. 
The blends in accordance with the invention are homogeneous on the 
macromolecular level, that is to say, the two components are completely 
soluble in each other. However, they are incompatible on the thermodynamic 
level as evidenced by the two separate melting events characteristic for 
each component observed in differential scanning calorimetry (DSC) 
experiments. If they were compatible on this level then one would expect 
to observe a new melting event at a value intermediate of the two 
individual components. 
The blends are further characterized by hardness values falling within the 
range of 85 Shore A to 75 Shore D. Generally speaking, this range can be 
attained through the use of just one polyesteramide base polymer along 
with the appropriate amount of polyamide to obtain the desired hardness 
level. Additionally, the increase in hardness can be attained without 
adversely affecting other physical properties. In fact, the high 
temperature resistant properties of the blends are superior to those of 
the base polymer. 
Furthermore, the addition of the polyamide for some unexplainable reason 
results in an improvement in the elastic elongation properties of the base 
polyesteramide. This is even more surprising in view of the fact that the 
percent elongation values of a majority of the aliphatic polyamides are 
less than 100 percent while their addition to a polyesteramide of 
typically 220 percent elongation will raise this latter value above 300 
percent. 
A further benefit to the polyesteramide through the addition of the 
polyamide lies in the improved resistance of the blends to various 
industrial fluids such as Skydrol 500 hydraulic fluid, brake fluid, ASTM 
#3 oil, lithium grease, toluene, and the like. This benefit is more 
evident as the level of the polyamide is increased. 
Another unexpected benefit characterizing the present blends is their 
better release properties from molds compared with the base polymer. 
The combination of properties inherent in the present blends provide for 
all of the benefits to be found in the polyesteramides of U.S. Pat. No. 
4,129,715 plus the additional ones noted above. Accordingly, the blends 
can be compression molded, extruded into any type of profile 
configuration, or injection molded into complicated shapes which release 
easily from the mold. The molded articles so obtained have good elastic 
and high temperature resistance and find utility in such applications as 
seals, gaskets, bushings, and the like. 
The following preparations and examples describe the manner and process of 
making and using the invention and set forth the best mode contemplated by 
the inventors of carrying out the invention but are not to be construed as 
limiting. 
Preparation of ester-amides 
The polyesteramides A, B, and C in accordance with U.S. Pat. No. 4,129,715 
and used in the following examples were prepared as follows. 
Polyesteramide A 
A carboxylic acid terminated prepolymer was prepared from 63 parts by 
weight (1.40 eq.) of 1,4-butanediol and 171.5 parts by weight (1.82 eq.) 
of azelaic acid in the presence of 0.23 part by weight of 
p-toluenesulfonic acid in 191.1 parts by weight of xylene as solvent. The 
water of condensation was azeotropically removed and when reaction was 
completed the solvent was removed in vacuo. A portion of the prepolymer 
(eq. wt.=508) so obtained (60.95 parts by weight or 0.12 eq.) was then 
reacted with 11.29 parts by weight (0.12 eq.) of azelaic acid, 8.65 parts 
by weight (0.12 eq.) of adipic acid, and 45.86 parts by weight (0.36 eq.) 
of 4,4'-methylenebis(phenyl isocyanate) in the presence of 0.23 part by 
weight (1.8.times.10.sup.-3 moles) of 1,3-dimethylphospholene-1-oxide and 
440 parts of anhydrous tetramethylene sulfone using the procedure 
described in U.S. Pat. No. 4,129,715 cited supra. The resulting segmented 
Polyesteramide A had an inherent viscosity (0.5 g/100 ml.) in 
N-methylpyrrolidinone (NMP) at 30.degree. C. of 0.77 dl/g. and was 
characterized by a recurring unit of formula (I) above wherein A is the 
residue of poly(tetramethylene azelate)glycol, B is the residue of azelaic 
acid, D in 50 percent of the recurring units is --CH.sub.2 4 and in the 
remaining 50 percent is --CH.sub.2 7, and R is 
4,4'-methylenebis(phenylene). 
Polyesteramide B 
Using the same procedure as described and referenced for Polyesteramide A 
above 4529 parts by weight (8.29 eq.) of a similar carboxylic acid 
terminated prepolymer (eq. wt. 546) were reacted with 978 parts by weight 
(10.4 eq.) of azelaic acid, and 2356 parts by weight (18.7 eq.) of 
4,4'-methylenebis(phenyl isocyanate) in the presence of 16.5 parts by 
weight (0.127 moles) of 1,3-dimethylphospholene-1-oxide and 28,600 parts 
by weight of anhydrous tetramethylene sulfone. The polyesteramide so 
obtained had an inherent viscosity of 0.80 dl/g. (0.5 percent w/w in NMP 
at 30.degree. C.) and was characterized by a recurring unit of formula (I) 
above wherein A is the residue of poly(tetramethylene azelate)glycol, B 
and D are residues of azelaic acid and R is 4,4'-methylenebis(phenylene). 
Polyesteramide C 
Using the same procedure as described above, the following reactants in the 
proportions by equivalents were reacted together: 1 equivalent of the 
carboxylic acid terminated poly(tetramethylene azelate) (eq. wt.=about 
510), 0.75 equivalent of adipic acid, 2.25 equivalents of azelaic acid, 
and 4 equivalents of 4,4'-methylenebis(phenyl isocyanate). The 
polyesteramide so obtained had an inherent viscosity of 1.4 dl/g. (0.5 
percent w/w in NMP at 30.degree. C.).