Polymer blends

Halide polymers such as polyvinyl chloride and polyamides melt blended at a polyamide to halide polymer weight ratio of about 1.5:1 to about 2:1 with an effective amount of a carboxyl and/or CO-functional ethylene polymer to compatibilize the halide polymer and polyamide exhibit superior chemical resistance.

This application claims the benefit of U.S. Provisional Application No. 
60/002,851, filed Aug. 28, 1995. 
FIELD OF THE INVENTION 
This invention relates to blends of vinyl halide or vinylidene halide 
polymer and polyamide together with a compatibilizing polymer in such a 
ratio to give tough, flexible, chemically resistance compositions suitable 
for wire and cable jacketing and chemically resistant liners. 
BACKGROUND OF THE INVENTION 
U.S. Pat. No. 5,352,735 (Hofmann), incorporated herein by reference, 
discloses the discovery that vinyl halide or vinylidene halide polymer and 
polyamide can be melt blended under certain conditions that the relatively 
low melting halide polymer does not degrade, and that useful blended 
products are obtained. The process of U.S. Pat. No. 5,352,735 comprises 
melt blending the halide polymer and polyamide together at a temperature 
of less than about 220.degree. C., with the polyamide being melt 
processible at the temperature of the melt blending, in the presence of an 
effective amount of ethylene polymer having carbon monoxide and/or 
carboxyl functionality to compatibilize the halide polymer with the 
polyamide. U.S. Pat. No. 5,352,735 also teaches compositions comprising 
these polymer components, but contains no teaching or suggestion regarding 
the chemical resistance of the resulting compositions. It teaches that the 
halide polymer and the polyamide proportions may vary widely (5 to 95 
weight percent of each based on 100 weight percent of the two polymers). 
All the examples have the polyamide present in a quantity that is 1.3 
times the weight of PVC polymer in the blend. 
SUMMARY OF THE INVENTION 
The present invention involves the discovery of improved compositions of a 
vinyl halide or vinylidene halide polymer, a polyamide, and a 
compatibilizing ethylene polymer having carbon monoxide and/or carboxyl 
functionality. These compositions display an outstanding balance of 
properties which include chemical resistance, toughness and low 
temperature flexibility. 
Particularly, the compositions of this invention comprise those with a 
volume swell of less than about 20% with a retention of tensile strength 
greater than about 60% after seven (7) days of soaking in Fuel C (a 50/50 
mixture of isooctane and toluene) at room temperature. The polyamide of 
this invention is present in the composition an amount 11/2 to 2 times the 
amount of the halide polymer in the blend and the ethylene polymer having 
carbon monoxide and/or carboxyl functionality is present in an amount up 
to 80 weight percent based on halide polymer content. 
DETAILED DESCRIPTION OF THE INVENTION 
Plasticized polyvinyl chloride (PVC) is the single largest volume 
electrical insulating material in use today. It has good electrical 
properties as well as very good abrasion and moisture resistance. Flexible 
PVC insulations are applied in building wires, power cables, appliance 
wiring, automotive wiring, communications wiring, etc. 
A particularly high performance insulation, defined by the Underwriters 
Laboratory as a THHN construction, consists typically of a 15 mil (0.38 
mm) insulation layer of flexible PVC covered with a 4 mil (0.10 mm) sheath 
or jacket of polyamide. The insulation layer must meet minimum electrical 
standards, the major contribution of the polyamide jacketing is chemical 
resistance, abrasion resistance and toughness. 
The production of such a two-component construction requires the use of two 
melt extrusion operations. The first melt extrusion operation coats the 
flexible PVC insulation layer onto the bare wire. This is then followed by 
a second extrusion operation that coats the polyamide onto the previously 
deposited flexible PVC layer. 
Scrap or reclaimed constructions require that the polyamide layer be 
stripped and separated from the flexible PVC insulation layer for 
recycling while the PVC layer is stripped from the wire for recycling. 
Cross-contamination of the incompatible polyamide in the recycled PVC 
material and the PVC in the recycled polyamide material are serious 
problems that often lead to materials that are considered useless and 
subject to landfill waste disposal. 
The present invention eliminates the need for a two layer construction and, 
as a result, the two melt extrusion operations can be reduced to a single 
melt extrusion operation using the compositions of this invention, thus 
greatly simplifying the extrusion process. 
The second benefit is elimination of the necessity of separating the 
polyamide jacket from the flexible PVC insulation layer during the 
recycling operation. 
The third benefit is the elimination of the cross-contamination that can 
occur between the polyamide jacket material and the flexible PVC material 
during recycling which, in turn, reduces the quantities of materials 
subject to disposal as landfill waste. 
It has been determined that a wide range of compositions composed of vinyl 
halide, a polyamide which has a melting point of less than about 
220.degree. C., and an ethylene polymer having carbon monoxide and/or 
carboxyl functionality, the ethylene polymer being added to compatibilize 
the halide polymer with the polyamide, provide most of the physical 
attributes that are required for wire and cable insulation. Across a wide 
range of compositions, they provide toughness as measured by notched izod 
and they provide flexibility, as measured by brittle point. 
It has now been discovered, however, that good chemical resistance, as 
measured by exposure (soaking for 7 days at room temperature) to Fuel C ( 
a 50/50 mixture of isooctane and toluene), is surprisingly only attained 
when the proportions of halide polymer, ethylene polymer and polyamide are 
kept in relatively restricted proportions. Particularly, the composition 
must be relatively polyamide-rich. 
Various constructions comprised of a coating of the composition of the 
present invention can be made. For example the composition may be coated 
onto a wire substrate, it may be made into a sheeting membrane, it may be 
used as a pipe liner, or it may be formed containers. 
The polyamide present in the composition of the present invention should be 
in an amount of about 1.5 to about 2 times, preferably about 1.75 to about 
2 times, (on a weight basis) the halide polymer present. These 
compositions should also contain an ethylene polymer to compatibilize the 
polyamide/halide polymer blend. 
The amount of the ethylene polymer incorporated into the melt blend should 
be an amount effective to compatibilize the halide polymer and the 
polyamide, one with the other. Typically this amount will be within the 
range of up to about 80 weight percent based on the weight of the halide 
polymer. When higher melting polyamides, such as Nylon 6, are included in 
the blend, higher amounts of ethylene polymer preferably should be used to 
achieve an effectively compatibilized blend, say 20 to 80, preferably 40 
to 60, weight percent based on weight of the halide polymer. When lower 
melting point polyamides, such as the MPMD, 6 and MPMD, 12 nylons, are 
included in the blend, lower amounts of the ethylene polymer should be 
effective, say 1 to 40, preferably 1 to 20, weight percent based on weight 
of the halide polymer. Also, preferred compositions can be obtained with 
some polyamides and halide polymers when the ethylene polymer is present 
at a level of about 20 to about 50 weight percent based on the weight of 
the halide polymer. 
Particularly preferred compositions are those of polyamide, halide polymer 
and ethylene copolymer (and stabilizers and other additives used in the 
art) in which the polyamide comprises more than about 45% (on total 
polymer weight basis). These compositions achieve volume swell values of 
less than about 20% with retention of tensile strengths of greater than 
about 60%. Compositions of these three polymers containing less than about 
45% polyamide (on total polymer weight basis) absorb much greater 
quantities of Fuel C, typically greater than 30% and have retention of 
tensile strength of only about 55% or less. Preferred compositions of 
these three polymers (and their stabilizers and additives) will contain up 
to about 65 weight percent (on a polymer weight basis) of the polyamide 
component. 
The vinyl halide or vinylidene halide polymer preferably contains chlorine 
as the halogen moiety. Polyvinyl chloride (PVC) is the most widely 
available chloride polymer used as wire insulation and, hence, is 
preferred in the present invention. The PVC can be a homopolymer of vinyl 
chloride or a copolymer thereof with a small amount, e.g., up to 20 weight 
percent, of another copolymerizable monomer such as vinyl acetate or 
ethylene which does not change the essential character of the homopolymer. 
The PVC will generally have a glass transition temperature (Tg) of about 
80.degree. C. and will normally be melt processed by itself at a 
temperature of 180.degree.-200.degree. C. Polyvinylidene chloride has a 
higher melt processing temperature, but is somewhat less thermally stable 
than PVC. In accordance with the present invention, in which other polymer 
components are present, the halide polymer can withstand higher melt 
processing temperatures for limited periods of time which are nevertheless 
sufficient time to accomplish the melt blending, without appreciable or 
detectable degradation of the halide polymer. 
The polyamide component is one which is melt processible at a temperature 
of less than about 220.degree. C. Some polyamides are melt processible at 
temperatures less than about 200.degree. C. The melt processing 
temperature of the polyamide is the temperature at which the viscosity of 
the polyamide is low enough that it can be deformed and compacted into a 
unitary, essentially void-free mass. This is not a specific melt viscosity 
but is a melt viscosity range at which these results can be obtained, 
which enables the melt processing of the composition of the invention to 
be carried out. In the case of crystalline polyamide, this viscosity is 
reached by the melt processing temperature exceeding the melting point 
(melting point determined by Differential Scanning Calorimetry (DSC) of 
the polyamide). In the case of amorphous polyamide, which may also contain 
a crystalline polyamide phase, this viscosity is reached at temperature 
above the Tg of the polyamide at which the polyamide softens sufficiently 
to provide the viscosity desired for melt blending. The relatively low 
melt processing temperature of the polyamides used in the present 
invention opens the door for the possibility of the halide polymer and 
polyamide being melt blended without degradation of the halide polymer. 
The most popular polyamide, polyhexamethylene adipamide (Nylon 66) melting 
at 255.degree. C., cannot be used because of its high melting point. 
Examples of polyamides having sufficiently low melt processing 
temperatures include polydodecamethylene dodecanoamide (Nylon 1212) which 
has a melting point of 184.degree. C., polycaprolactam (Nylon 6) which has 
a melting point of about 215.degree. C. polydodecanolactam (Nylon 12) 
melting at 180.degree. C., polyhexamethylene dodecanoamide (Nylon 6,12) 
melting at 210.degree. C., polydecamethylene sebacamide (Nylon 10,10) 
melting at 216.degree. C., polyundecanoamide (Nylon 11) melting at 
185.degree. C., poly 2-methylpentamethylene adipamide (MPMD, 6) melting at 
180.degree. C., poly 2-methylpentamethylene dodecanoamide (MPMD, 12) 
melting at 160.degree. C. and polyhexamethylene sebacamide (Nylon 6,10) 
melting at 215.degree. C. and the amorphous polyamides prepared by 
copolymerizing (condensation polymerizing) a mixture of diacids, such as 
adipic and isophthalic acids, with hexamethylene diamine. 
Despite the higher melting point of some of these polyamides as compared to 
halide polymer, it has been found that it is possible to melt blend them 
together at the higher melt processing temperatures that may be required 
by the polyamide without the halide polymer degrading. 
The third component of the melt blend, i.e., the functionalized ethylene 
polymer, promotes this melt blending by its presence in the melt blend, 
which improves the ability of the halide polymer and polyamide to be 
thoroughly dispersed within one another without any appreciable 
degradation of the halide polymer. The ethylene polymer may also aid the 
thorough mixing of the other polymer components by reducing the melt 
viscosity of the melt blend. 
Preferably, the ethylene polymer is miscible with the halide polymer in the 
melt blending process, whereby under magnification, the melt blend (upon 
cooling) has only two phases that are visible, the halide polymer phase 
and the polyamide phase. When about equal amounts of the halide polymer 
and polyamide are present, the melt blend result is an intimate blend of 
co-continuous phases of these polymers, otherwise the melt blend result is 
a fine dispersion of one of the polymers in a matrix of the other polymer 
which is present in the greater amount. The miscibility of the ethylene 
polymer with the halide polymer tends to promote the halide polymer as the 
matrix phase or co-continuous phase, even when the amount of polyamide 
somewhat exceeds the amount of halide polymer, depending on the amount of 
ethylene polymer that is present. 
The compatibilizing effect of the ethylene polymer is manifested by 
intimate, essentially void-free contact between the halide polymer and 
polyamide phases of the melt blend and, thus, of articles fabricated 
therefrom, and by a toughness which is greater than either of the halide 
or polyamide components. 
The ethylene polymer achieves its compatibilizing effect in part by being 
compatible with, preferably miscible with, the halide polymer, and with 
the carboxyl or carbon monoxide functionality of the ethylene polymer 
providing interaction with the polyamide. The carboxyl (coo-) and carbon 
monoxide functionalities are believed to covalently bond and hydrogen 
bond, respectively, with the polyamide. Preferably, the ethylene polymer 
contains both carboxyl and carbon monoxide groups. 
Examples of carboxyl-functionalized ethylene polymer are copolymers of 
ethylene with C.sub.3 -C.sub.12 ethylenically unsaturated monocarboxylic 
acids, C.sub.1 -C.sub.18 alkyl esters of ethylenically unsaturated C.sub.3 
-C.sub.12 monocarboxylic acids, and vinyl esters of C.sub.3 -C.sub.18 
saturated carboxylic acids. More specific examples include ethylene/vinyl 
acetate copolymer ethylene/alkyl (meth)acrylic acid copolymer, wherein the 
alkyl group contains 1 to 8 carbon atoms. Such ethylene polymers include 
copolymer of ethylene with methyl acrylate, propyl acrylate, n-butyl 
acrylate, hexyl acrylate, or n-butyl acrylate and/or the corresponding 
free acids. For these polymers, the proportion of ethylene will generally 
be about 30 to 60 weight percent, with the carboxyl functionality being 
about 40 to 70 weight percent, to total 100 weight percent of the 
copolymer. 
Preferably the ethylene polymer is also functionalized with carbon monoxide 
which enables a small amount of acetate, acrylate, or acrylic acid 
comonomer to be used, to obtain the hydrogen bonding with the polyamide 
necessary for compatibilization. Preferred such polymers are 
ethylene/alkyl (meth)acrylate/carbon monoxide copolymer wherein the alkyl 
group can have the identities described above. Also preferred are 
ethylene/vinyl acetate/carbon copolymers. Generally for these copolymers 
the proportion of ethylene will be about 50 to 70 weight percent, the 
proportion of acid, acrylate, or acetate will be about 24 to 40 weight 
percent, and the proportion of carbon monoxide will be about 5 to 15 
weight percent, to total 100 weight percent of the ethylene polymer. 
The ethylene carboxyl and/or carbon monoxide-functional copolymer 
preferably is also anhydride modified, i.e., it contains carboxylic acid 
anhydride groups pendant from the polymer backbone. Anhydride modification 
typically is obtained by grafting reaction between the preformed copolymer 
with maleic acid or maleic anhydride to form succinic anhydride groups on 
the copolymer by conventional procedures. Typically, the amount of 
anhydride modification will be about 0.1 to 5 weight percent based on the 
weight of the copolymer. The most preferred ethylene polymer is 
ethylene/alkyl acrylate/CO copolymer modified with succinic anhydride, 
wherein the alkyl group has 1 to 4 carbon atoms, and is preferably n-butyl 
acrylate. 
The anhydride modification of the functionalized ethylene polymer provides 
better bonding to the polyamide phase, believed to result from chemical 
reaction between the anhydride groups with the polyamide. 
The melt blending of the three components can be carried out using 
conventional equipment such as extrusion screws in an extruder or 
injection molding machine. Preferably these components are pre-blended 
such as by dry mixing together of the halide polymer, which is in powder 
form, with typical halide polymer stabilizers. Followed by melt blending 
the stabilized halide polymer powder with the polyamide and the ethylene 
polymer. The polyamide and ethylene polymers will typically be in the form 
of molding granules. Conventional additives such as an antioxidant can 
also be present in the melt blend. 
The melt blending is typically carried out in conventional plastics melt 
compounding equipment such as batch mixers, twin screw extruders and 
single screw kneaders. 
The melt blends of compositions of the present invention can be melt 
fabricated into a wide variety of articles by conventional processes such 
as extrusion and injection molding into such forms as wire coatings, 
tubes, pipe liners, sheets, films and molded articles such as containers. 
In the following Examples of the invention, parts and percents are by 
weight unless otherwise indicated.

EXAMPLE 1 
In the series of experiments covered by this Example the PVC used was VISTA 
5305 having an inherent viscosity of 0.74 (ASTM 1243) and a Tg of about 
80.degree. C. This PVC powder was blended in a powder mixer (WELEX) with 
the following stabilizers: 2.7% butyl tin mercaptin (MARK 1900), 0.9% 
thioester (SEENOX 412S) and 0.9% hindered phenol (IRGANOX 1098). Also 
added to the PVC powder mix was a wax lubricant (HOECHST WAX E) at 2.7% 
and a flame retardant additive (THERMOGUARD CPA) at 4.4%. All values are 
weight percents based on the weight of the total PVC powder blend. The 
polyamide used was nylon 12 available as RILSAN AESNO TL and having a 
melting point of 180.degree. C. The ethylene polymer was 60 weight percent 
ethylene, 30 weight percent n-butyl acrylate, and 10 weight percent carbon 
monoxide grafted with 0.9 weight percent succinic anhydride groups 
available as FUSABOND MG-175D. 
Compositions were prepared on a 46 mm Buss Kneader having an length to 
diameter ratio of 16 to 1. The kneader was equipped with two feed ports; 
one at the upstream end of the machine, as is customary, and a second one 
positioned downstream at a distance of about one-half the length of the 
machine or about 8 diameter lengths from the first feed port. The nylon 
pellets and the ethylene polymer pellets were fed together into the first 
feed port and the PVC powder blend was fed into the second feed port. 
The ingredients were metered so that the rate of production of the final 
composition was about 50 pounds per hour. The temperature of the molten 
polymer ingredients was controlled by the barrel heaters of the kneader 
and the rpm of the screw. The set temperatures between the first feed port 
and the second feed port were set in a downhill temperature profile 
starting at about 275.degree. C. and decreasing to about 170.degree. C. 
This facilitated the rapid melting and homogenization of the nylon and 
ethylene polymers added at the first feed port. 
It also sufficiently cooled this melt to about 180.degree. C. by the time 
it reached the second feed port. This allowed the safe introduction of the 
PVC powder blend at the second feed port without exposing the heat 
sensitive PVC to excessive temperatures. The remainder of the kneader 
length was heated at about 150.degree. C. so that the resulting 
homogeneous three component polymer blend developed a melt temperature in 
a range below or not to excessively exceed 200.degree. C. 
The screw speed was typically 310 RPM and the screw temperature was 
150.degree. C. 
The molten blend, exit the kneader, was fed to a low shear and relatively 
cool (.about.160.degree. C.) single screw extruder which pumped the melt 
through a 4 hole die. The resulting strands of blend were quenched in a 
water bath and then cut into pellets. 
Table I shows the results of increasing levels of polyamide (Nylon 12) in 
blends of PVC with the ethylene copolymer compatibilizer. 
Test specimens were compression molded from the pellets produced on the 
Buss kneader. Tensile strength, elongation and resistance to Fuel C were 
measured (Table 1). 
TABLE 1 
______________________________________ 
A B C D 
______________________________________ 
PVC 56.2 47.0 38.0 27.6 
Nylon 12 18.7 23.5 38.0 55.1 
Ethylene polymer 18.7 23.5 19.1 13.8 
Stabilizers and additives 
6.4 6.0 4.9 3.5 
Fuel C, 7 days 
Volume Swell (%) 39 44 31 6.3 
Retention of Tensile Strength (%) 
56 50 56 92 
Retention of Elongation (%) 
192 87 51 83 
Orig. Tensile Strength (MPa) 
20.8 19.1 26.1 30.7 
Orig. Elongation (%) 
131 274 353 316 
______________________________________ 
It is quite clear that at a polyamide level of about 40% (polymer basis) or 
below (Samples A through C) the volume swell in the chemically aggressive 
Fuel C exceeds 30%. Concurrent with this volume increase is a decrease in 
tensile strength of about 40% or more. To the contrary, at a level of 
polyamide of 57% (total polymer basis), that is, at a polyamide level of 2 
times the weight of PVC, the volume swell is only 6% and the tensile 
strength decreases only 8%, a five-fold improvement in chemical 
resistance. 
EXAMPLE2 
In the series of experiments covered by this Example the PVC used was VISTA 
5265 having an inherent viscosity of 0.68 (ASTM 1243) and a Tg of about 
80.degree. C. This PVC powder was blended in a powder mixer (WELEX) with 
the following stabilizers: 3.7% butyl tin mercaptin (MARK 1900), 1.0% 
thioester (SEENOX 412S) and 1.0% hindered phenol (IRGANOX 1098). Also 
added to the PVC powder mix was a wax lubricant (HOECHST WAX E) at 2.8%. 
All values are weight percents based on the weight of the total PVC powder 
blend. 
Compositions were prepared by adding the ethylene copolymer, polyamide 
(dried) to a Haake 90 mixer. The mixer set temperature was 180.degree. C. 
and the rpm was set at 50. After all of the ingredients were added (less 
than one minute), the mixer temperature was set at 205.degree. C. and the 
rpm raised to 200. Mixing was continued until the mixture became uniformly 
molten which occurred at about 200.degree. C. in about 8 minutes. The set 
temperature was then decreased to 185.degree. C. and the rpm lowered to 
75. The mixture temperature decreased to about 205.degree. C. (in about 3 
minutes). The PVC was then added and the composition was mixed for about 5 
minutes or until homogeneity became evident. During this time the 
temperature was kept below 205.degree. C. by adjustment of the rpm. The 
sample was then discharged and quenched in dry ice. Test specimens were 
compression molded from the compositions prepared in the Haake mixer for 
testing notched Izod impact strength, elongation, tensile strength and 
resistance to Fuel C. 
TABLE 2 
______________________________________ 
E F G H 
______________________________________ 
PVC 27.9 32.4 27.9 32.4 
Nylon 12 55.7 48.5 
Nylon MPMD, 6 55.7 48.5 
Ethylene polymer 13.9 16.2 13.9 16.2 
Stabilizers & additives 
2.5 2.9 2.5 2.9 
Fuel C, 7 days 
Volume Swell (%) 12 18 6.2 16 
Retention of Tensile Strength (%) 
79 65 84 75 
Retention of Elongation (%) 
114 106 125 112 
Orig. Tensile Strength (MPa) 
47.2 46.6 42.3 39.9 
Orig. Elongation (%) 
262 273 275 298 
Notched Izod (J/m) 
no bk. no bk. no bk. 
no bk. 
______________________________________ 
It is evident from the samples G and H (Table 2) the nylon MPMD, 6 is also 
very resistant to Fuel C and even matches or even exceeds comparable 
blends of nylon 12 (Samples E and F). These blends composed of polyamide 
of about 50% (or more), have Fuel C volume swell values of below 20% and 
retain tensile strengths of greater than about 65%. These compositions 
prove to be very tough as indicated by the lack of breakage as measured by 
the Notch Izod test. 
EXAMPLE 3 
In this example, the PVC (VISTA 5305) was blended with 3.7% butyl tin 
mercaptin (MARK 1900), 0.9% hindered phenol (IRGANOX 1098), 0.9% thioester 
(SEENOX 412S) and 2.8% wax lubricant (HOECHST WAX E). 
The polyamide used was nylon MPMD, 12. The ethylene polymer was 60 weight 
percent ethylene, 30 weight percent n-butyl acrylate and 10 weight percent 
carbon monoxide grafted with 0.9 weight percent succinic anhydride groups 
available as FUSABOND MG-233D. 
Compositions were prepared in a manner similar to Example 1. Tensile 
strength, elongation and notched Izod impact strength were measured and 
are reported in Table 3. 
TABLE 3 
______________________________________ 
I J 
______________________________________ 
PVC 27.9% 21.7% 
Nylon MPMD, 12 55.7% 65.4% 
EnBACO-g-MAH 13.9% 10.9% 
Stabilizers and 2.5% 2.0% 
additives 
Tensile Strength 39.3 29.6 
at break, Mpa 
Elongation, at 312 250 
at break, % 
Notched Izod, No break 320 
J/m 
______________________________________ 
Table 3 shows that the tensile strength at break, elongation and notched 
Izod impact strength were superior in sample I, where the polyamide is 
present in a weight amount of 2.0 times the weight amount of the halide 
polymer. In sample J, the polyamide is present in a weight amount of 3.0 
times the weight amount of the halide polymer.