Note: Descriptions are shown in the official language in which they were submitted.
l~S31~
--1--
COMPATIBILIZED POLYMER BLENDS
This application relates to improved polymer blends
of olefin polymer and nitrile rubber, and in particular,
blends of enhanced compatibility due to the presence of
a block copolymer comprising nitrile rubber compatibilizing
segments and olefin polymer compatibilizing segments.
This application is a divisional of co-pending
application serial number 372,606, filed March 9, 1981.
BACKGROUND OF T~E INVENTION
Blends of olefin polymer and nitrile rubber are known.
For example, see U. S. Patent 3,909,463 and U. S. Patent
4,104,210. Olefin polymers and nitrile rubber are largely
incompatible with one another. Mutual incompatibility
prevents the development of optimum properties in blends
of these materials. Thus, if the compatibility of the blend
components can be increased, improved blends may be obtained.
This is because particles of one or another component in
the blend will be smaller and less likely to act as flaws.
SUMMARY OF THE INVENTION
It has now been discovered that an improved composition
comprising a blend of an olefin polymer and nitrile rubber
can be prepared by the use of a compatibilization enhancing
amount of a block copolymer comprising at least one molecular
,: .
.
. ~ .
llS3~7
43-51-1043A
--2--
segment each of nitrile rubber and olefin polymer. Typi-
cally, improved compatibilized polymer blends comprise
akout 1-99 parts by weight of an olefin polymer, prefer-
ably a thermoplastic crystalline olefin polymer, and
correspondingly, about 99-1 parts by weight of nitrile
rubber having an average molecular weight of 50,000 or
more, and at least about 0.1 weight percent of a block
copolymer comprising nitrile rubber compatibilizing
molecular segments and olefin polymer molecular compati-
bilizing segments. A preferred composition comprises a
blend of about 10-90 parts by weight of olefin polymer,
and correspondingly about 90-10 parts by weight of nitrile
rubber, and 0.5-25 parts by weight of block polymer.
The term "block copolymer" means a material in which
olefin polymer compatibilizing molecular segments and
nitrile rubber compatibilizing molecular segments are
chemically linked to one another. Examples of olefin
compatibilizing segments are polybutadiene, polyisoprene,
and polyalkenamer, as well as the olefin polymers them-
selves. Examples of nitrile rubber compatibilizing
segments are epichlorohydrin polymer, polyamide, polyamine,
acrylic polymer, and polyester, as well as nitrile rubber
itself. Compatibilizing segments have chemical or physical
affinity for olefin polymer or nitrile rubber. The
compatibilizing block copolymer has affinity for both the
olefin polymer and the nitrile rubber and its presence
improves the compatibility between olefin polymer and
nitrile rubber. Any thermoplastic uncross-linked block
copolymer of nitrile rubber and olefin polymer is suitable
for preparing the improved compatibilized blends of the
invention. A block copolymer may be prepared by causing
l~S3147
43-51-1043A
--3--
a reaction to form a bond between the olefin polymer and
nitrile rubber. Preferably, only one bond is formed for
each olefin polymer molecule and nitrile rubber molecule.
Block copolymers containing more than one bond per mole-
cule are satisfactory; but it is preferred that the
number of bonds is not so high that the resulting copolymer
is in the form of a network molecular structure and is no
longer thermoplastic.
One embodiment of the invention relates to an especi-
ally effective class of block copolymers comprising segments
of olefin polymer and nitrile rubber, said block copolymer
being prepared from an olefin polymer containing one or
more graft forming functional groups. More preferred block
copolymers are prepared from olefin polymer and nitrile
rubber each of which contain graft forming functional
groups. Examples of satisfactory functional groups are
carboxy-, halo-(preferably, chloro- or bromo-), amino-,
groups derived from methylol phenolic material, hydroxy
groups, epoxy groups, and sulfonyl, sulfonic acid or salt
groups. Functional olefin polymer and functional nitrile
rubber may be prepared by known techniques and some of
these materials are commonly available. For example,
functional groups may be provided during polymerization by
copolymerizing an olefin and an unsaturated carboxylic acid.
Alternatively, functional groups may be introduced by
direct reaction with the polymer by known grafting reac-
tions. The functional groups may react directly to form
a block copolymer between the olefin polymer and nitrile
rubber. In the absence of graft forming functional groups,
it may be necessary to provide another reactant in order
to form a block copolymer. For example, when the functional
~lS3~4~
43-51-1043A
--4--
groups of the polyolefin and nitrile rubber are carboxy,
a polyfunctional reactant such as a polyamine may react
with the carboxy groups to form a block copolymer.
Functionalized liquid nitrile rubbers having a molecular
weight of about 500 to 50,000, preferably about 800 to
10,000, are especially preferred block copolymer precursors.
Block copolymers which are derived from methylolphenolic
modified olefin polymer or maleic modified olefin polymer
and nitrile rubber containing amino groups are especially
preferred.
Olefin polymer molecules are generally functionalized
before they interact with nitrile rubber molecules. This
is because functionalizing agents can generally react far
more rapidly with rubber molecules than with molecules of
olefin polymer. In the presence of comparable amounts of
both olefin polymer and rubber, functionalizing agent could
be depleted without enough reaction with olefin polymer;
it could be used up by reaction with essentially only the
rubber. In addition, some functionalizing agents such as
dimethylol phenolic derivatives are highly active rubber
curatives. Such agents would more likely gel the rubber
than functionalize the olefin polymer; further, gelled
rubber, even though it might become chemically bound to
olefin polymer molecules, may not form a compatibilizing
block polymer.
To insure that reaction occurs between functionalizing
agent and olefin polymer, it is frequently advisable, and
some~imes essential, that the olefin polymer be functional-
ized in the absence of rubber, before admixture with rubber
in a later portion of the procedure. For example, olefin
polymers should be functionalized by dimethylol phenolic
derivatives in the absence of the usual types of high
molecular weight nitrile rubber.
~1531~
43-51-1043A
--5--
However, an olefin polymer can be functionalized in
the presence of a relatively small amount of a preferably
low molecular weight liquid nitrile rubber by the action
of a highly active curative such as a peroxide. Here,
molecules of a high concentration of olefin polymer are
functionalized by a very small amount of free radical
generator which form transient "molecules" of functionalized
olefin polymer in which the functional groups are unpaired
electrons of the so-formed polymeric free radical. The
polymeric free radical (functionalized olefin polymer) then
attacks the preferably low molecular weight nitrile rubber
molecules to form the compatibilizing block copolymer
molecules which contain molecular segments of both nitrile
rubber and olefin polymer. A reduction in either the
molecular weight or concentration of nitrile rubber sup-
presses the formation of rubber gel. Also, low molecularweight rubber molecules are mobile and can diffuse rapidly
to the olefin polymer free radical sites for block polymer
formation; the resulting compatibilizing block polymer
molecules can also diffuse more rapidly to the olefin
polymer-nitrile rubber interface to exert their compati-
bilizing effect.
Any essentially uncross-linked block copolymer of
olefin polymer and nitrile rubber is suitable for preparing
compatibilized blends of the invention. Examples of
suitable block copolymers, methods for preparing them, and
the types of linkages visualized between, for example,
polypropylene (PP) and nitrile rubber (NBR) are shown as
follows:
llS3~4'7
43-51-1043A
--6--
LINKAGE _ SYNTHESIS
Treat molten mixture of
PP containing a small
PP NBR amount of low m.w. NBR
with a small amount of
peroxide.
_
First halogenate poly-
~ R ~ propylene (slightly)
1 ~9 2 ~ ¦ then melt mix it with NBR
which contains amine
~ groups.
First treat molten PP
" with maleic acid or
anhydride (in presence
\ . of peroxide~, then melt
N ¦NBR¦ mix it with NBR contain-
/ ing amine groups (which
'`~ can be introduced into
O NBR by LiAlH4 reduction).
First treat maleic modi-
fied PP with polyethylene-
polyamine (e.g., DETA)
\ then mix it with NBR
I which contains carboxyl
~ N-CH2-CH2NRH2 groups.
" 1~),. _
O O-C - NBR
OH
_ _First treat molten PP
with dimethylolphenolic
CH2- ~ -CH~ ~ derivative (with catalyst)
~ then melt mix it with NBR.
- R -
OH First treat molten PP with
,1~ , . dimethylolphenolic deriva-
CH2 ~ ~ CH2-NR2-tNBRI tive (with catalyst) then
melt mix it with NBR which
contains amine groups.
R
.
~i5;314~7
43-51-1043A
--7--
A block copolymer may be prepared by reacting a
polypropylene with a liquid rubber and maleic anhydride
in a solvent in the presence of a radical generator, for
example, see U. S. Patent 4,078,017, issued March 7, 1978.
Generally, the amount of graft forming functional
group does not exceed 10 weight percent of the olefin
polymer or nitrile rubber. It can, however, be considerably
lower with amounts in the vicinities of 1 percent or less
being enough to cause sufficient block copolymer formation
to enhance the compatibility of a blend of olefin polymer
and nitrile rubber.
The compatibilizing block copolymer can be formed
from compatibilizing segments as long as they are function-
alized to mutually interact to form a link therebetween.
A suitable functionalized olefin polymer may be
conveniently prepared by masticating olefin polymer,
preferably at a temperature above its melting point, for a
period of about 1-20 minutes, and 0.1 to 20 weight percent
methylol phenolic material, in the presence of an activator
(catalyst) which promotes reaction between methylol
phenolic material and the olefin polymer. An example of
a satisfactory activator is a Lewis acid. Another suitably
functionalized olefin polymer may be prepared by causing
an unsaturated carboxylic acid such as acrylic or metha-
crylic acid, maleic acid, anhydride, or ester, or N-substi-
tuted maleamic acid, to react in the presence of a free
radical generator with olefin polymer, by known processes.
For example, see U. S. Patent 2,973,344. The resulting
functionalized olefin polymer is then caused to react with
a functionaliæed nitrile rubber.
liS3~47
43-51-1043A
--8--
Olefin polymers suitable for functionalization to
give block polymer percursors comprise amorphous or cry-
stalline essentially saturated homopolymers or copolymers
of C2-cg alpha monoolefins. Thermoplastic crystalline
olefin polymers are especially preferred. An important
subgroup of olefin polymers comprise high molecular
weight solid products from the polymerization of one or
more monoolefins by either high pressure or low pressure
processes. Examples of such polymers are the isotatic
or syndiotactic monoolefin polymers, representative
members of which are commercially available. Satisfactory
olefins include ethylene, propylene, i-butene, l-pentene,
l-hexene, 2-methyl-1-propene, 3-methyl-1-pentene,
4-methyl-1-pentene, 5-methyl-1-hexene, and mixtures thereof.
Commercially available thermoplastic polyolefin resins,
such as polyethylene, polybutene-l, and polypropylene, or
mixtures thereof, may be advantageously used in the
practice of the invention with polypropylene being -
preferred. Also suitable for the practice of the invention
are copolymers of two or more olefins with copolymers of
ethylene and propylene being preferred.
Any methylol phenolic material which will form a graft
with olefin polymer may be used in the practice of the
invention. Suitable methylol phenolic material may be
prepared by condensation of unsubstituted phenol, a Cl-Clo
alkyl-~-substituted phenol, or halogen substituted phenol
with an aldehyde, preferably, formaldehyde in an alkaline
medium, or by condensation of phenol dialcohols. Methylol
phenolic material includes polymeric phenols containing
up to 10 benzene rings but preferred materials contain no
more than three benzene rings. Especially preferred are
~LS3147
g
methylol phenolic materials derived from dimethylol phenol
subst;tuted with C5 10 alkyl groups preferably tertiary
alkyl groups in the para posi.tion. Examples of satisfactory
dimethylol phenolic materials are described in U. S. Patents
2,972,600; 3,093,613; 3,287,440; 3,709,840; and 3,211,804,
Column 5, lines 3-67. Halogenated, for example brominated,
methylol phenolic materials are als-o suitable. These
halogenated materials release, at elevated temperatures,
hydrogen halide, which in the presence of a metal oxide
such as zinc oxide, serves as an acidic activator. Suita~le
methylol phenolic materials are commercially available,
for example, they may be purchased under the trade names
of SP-1045, SP-1055, SP-1056, CRJ 352, and certain Arofene~
resins.
Any activator (catalystl w~ich.promotes the graft
formation between olefin polymer and methylol phenolic
material is suitable for the practice of the invention.
Preferred activators are Lewis acids ~hi.ch include the
acid-acting metal halides s:uch.as boron trifloride, stannous
chloride, zinc chloride, titanium tri.- or tetrachloride,
aluminum ch.loride, ferric chloride, ferric bromide, zinc
bromide, aluminum bromide or complexes thereof. Suitable
Lewis acids are described in U.S. Patent 4,121,026, Columns
5-6.
Suitable nitrile rubbers comprise rubbery polymers
of 1,3-butadiene or isoprene and acry-lonitrile. Preferred
nitrile rubbers comprise polymers of 1,3-butadiene and
about 20-50 weight percent acrylonitrile. A "functional-
ized" nitrile rubber containing one or more graft forming
* Trademark
~3~7
43-51-1043A
--10--
functional groups is preferred for preparing block copoly-
mer compatibilizers of the invention. The aforesaid
"graft forming functional groups" are different from and
are in addition to the olefinic and cyano groups normally
present in nitrile rubber. Carboxylic-modified nitrile
rubbers containing carboxy groups and amine-modified
nitrile rubbers containing amino groups are especially
useful for the preparation of block copolymers comprising
segments of nitrile rubber. Any nitrile rubber, regardless
of molecular weight, is suitable for the preparation of
block copolymer, but, as indicated earlier, liquid nitrile
rubbers having a molecular weight of less than 50,000 are
preferred for this purpose. This contrasts with the nitrile
rubber components of the blend which is a "solid" rubber
having an average molecular weight of at least 50,000, and
preferably, between about 100,000-1,000,000. Commercially
available nitrile rubbers suitab~e for the practice of
the invention are described in Rubber World Blue Book,
1975 edition, Materials and Compounding Ingredients for
Rubber, pages 415-430.
The improved blends of the invention may be prepared
by mixing olefin polymer, high molecular weight nitrile
rubber, and block copolymer, preferably above the melting
point of the olefin polymer by the use of conventional
masticating equipment, for example, a rubber mill,
Brabender Mixer, Banbury Mixer, or twin screw continuous
mixer. Mixing times should be sufficient to obtain
homogeneous blends. Satisfactory mixing times depend upon
the types of olefin polymer and nitrile rubber and upon
the type and amount of block copolymer. Typically, mixing
times of about 2-30 minutes are satisfactory. If the
polymer blend is obviously nonhomogeneous, additional
mixing is required. When the blend components are thoro-
ughly mixed, improved properties are obtained.
~ 43-51-1043A
The compatibilized blends of the invention may be further
improved by vulcanizing the nitrile rubber by conventional
techniques. Vulcanizing agents are incorporated into the
blends and the blends are heated to effect cure. The charac-
teristics of the blends containing cured nitrile rubber
depend upon the relative proportions of olefin polymer and
nitrile rubber and whether the compositions are statically
or dynamically cured. Static curing can give thermoset
compositions when the blend contains more than 30 parts by
weight of cured nitrile rubber per 100 parts by weight of
olefin polymer; whereas, dynamic curing can give thermoplastic
compositions even when the blend contains 80 or more parts
by weight of cured nitrile rubber per 100 parts by weight of
olefin polymer. Generally, compositions comprising 50 parts
or more of cured nitrile rubber per 100 parts by weight of
olefin polymer are elastomeric. The effect of the relative
proportions on blend composition characteristics cannot be
defined with precision because the limits vary depending upon
a number of factors, such as, the kind of olefin polymer and
nitrile rubber, the presence of fillers, plasticizers and
other ingredients, and the extent the rubber is cured. Of
course, it is understood that the properties of the composi-
tions of the invention may be modified by the addition of
ingredients which are conventional in the compounding of
olefin polymer, nitrile rubber, and blends thereof. For
additional information concerning compounding and dynamic
vulcanization, refer to U. S. Patent 4,104,210, issued August
1, 1978. Compositions prepared by dynamic vulcanization
comprising a blend of about 25-65 parts by weight of olefin
polymer, preferably polypropylene, and correspondingly, about
75-35 parts by weight of cured nitrile rubber in the form of
small particles (preferably 50 microns or less) dispersed
throughout the olefin polymer, in which the blend has been
compatibilized, prior to vulcanization, with a block copolymer
comprising ole~in polymer compatibilizing segments and nitrile
rubber compatibilizing segments are especially preferred.
llS31~7
43-51-1043A
-12-
Elastomer compositions generally contain no more than 55
parts of polypropylene per 100 parts of the composition.
Improved blend compositions of the invention can be
usecl to form a variety of molded, extruded, or calendered
articles. The properties of the blend depend upon the
proportions of the components in the blend with a wide range
of properties being available simply by varying the propor-
tions of the blend components.
The stress-strain properties of the composition are
determined in accordance with ASTM tes~t procedures. For the
compositions of Table 2, tests are carried out using a
Microdumbbell tensile test specimen (ASTM D-1708-66) having a
test length of 0.876 inches ~2.23 cm.). An Instron tensile
tester is used to pull the specimens apart during the test
for tensile strength and ultimate elongation. The tester is
designed to measure changes in jaw separation in inches.
Though the initial jaw separation was adjusted to the ASTM
procedure~ to 0.90 inches (2.29 cm.) and the specimen length
and jaw separation are not 1.00 inches (2.54 cm.), the
elongation at break was read as the jaw separation increase,
20 in inches. The percent ultimate elongation or elongation at
break was calculated by multiplying the change in jaw separa-
tion required to break the specimen (measured in inches) by
100. It is true that the original unstrained sample length
was 0.876 inches (not l.00 inch) and one might expect that
the change (in inches) in jaw separation should be divided
by 0.876 inches as well as being multiplied by lO0. However,
it is also true that some flow of the specimen occurs in
the jaws, which flow, in effect, somewhat increases the
initial or unstrained length. Since the effective length
change due to flow of the specimen in the jaws is difficult
to measure in each case, and since the effect of this is in
the opposite direction of not dividing by 0.876, it was found
expedient to estimate the percent ultimate elongation or
elongation at break, merely by multiplying the jaw separation 35 at break (measured in inches) by 100. The actual value may
deviate from this somewhat; however, the method presented
1~5314~
43-51-1043A
-13-
herewith is incorporated into the definition for percent
elongation used herein. Test specimens are pulled to 2.5 cm.
per minute up to 30 percent elongation and 25.4 cm. per
minute to failure. For the rest of ~he compositions (not in
Table 2) ASTM D-638 was used.
DESCRIPTION OF PREFERRED EMBODIMENTS
Polypropylene having methylol phenolic groups grafted
thereto is prepared by masticating polypropylene and methylol
phenolic material at 80 rpm's with an oil bath temperature
of about 180C in a Brabender Mixer. The ingredients are
shown in Table 1.
TABLE 1
(a) (b) (c) (d)
Polypropylene 100 100 100 100
SP 1045 2 2 2 4
15 SnC12.2H20 0.8
MgO ~ ~ 0-07
~ .
All parts are by weight. After the polypropylene (Profax~
67231 is melted, dimethylol-p-octylphenol ~SP-1045) is added
and mixing is continued for 5 minutes. The mixture is then
removed and passed through a mill to form a sheet. In Stocks
(b), (c), and (d), after mixing the SP-1045 for 2 minutes,
the indicated proportions of stannous chloride activator is
then added and mixing is then continued for an additional
3 minutes. In Stock (c), 0.07 parts of magnesium oxide is
added (to neutralize any free acid) and mixed for 1 additional
minute. The stocks designated (b), (c), and (d)
are used in the preparation o~ improved blend compositions of
the invention. It should be noted that, though the oil bath
temperature was about 180C, the melt temperature generally
reaches about 190C after the stannous chloride is added. The
batch sizes are about 56-60 gm. and cam-type rotors are used.
~153~7
43-51-1043A
-14-
If the temperature tends to rise above 190C, the mixing
speed is reduced to control the temperature at 190C.
Compatibilized blends (Table 2) are prepared by masti-
cating modified polypropylene and nitrile rubber in a
5 Brabender mixer for 3 minutes after the polypropylene is
melted. Stock 1 is, a control containing unmodified poly-
propylene. Stock 2 is an improved composition of the invention
whe-e 50 Farts by weight of modified polypropylene (Stock (b)
of Table 1) are mixed with 50 parts by weight of nitrile
rubber (Hycar 1092-80). In Stocks 3 and 4, the nitrile rubber
is dynamically cured by melt mixing the blend with dimethylol
phenolic curative. Enough residual cure activator is present
in the modified polypropylene to activate the phenolic
curative. The data show a substantial improvement in tensile
strength and ultimate elongation by use of the modified
polypropylene. This indicates graft formation between poly-
propylene and nitrile rubber. By functionalizing the poly-
propylene, the true stress at break nearly doubles, Stocks
3 and 4 show that curing the nitrile rubber results in further
improvement in ultimate elongation and true stress at break.
TABLE 2
1 2 3 4
25 Polypropylene 50
Modified PP (b) - 50 50 50
~itrile Rubber 50 50 50 50
SP-1045 - - 1.67 5.0
Properties
TS, MPa 7.2 10.1 10.5 11.6
Mloo, MPa - - 10.2 11.5
E, MPa 182 170 157 153
Elong., ~ 24 66 170 130
TS8, MPa 8.9 16.8 28.4 26.7
1~S31~7
43-51-1043A
-15-
In Table 3, compositions of the invention are illustrated
in which the polyolefin-nitrile rubber block copolymer is
derived from methylol phenolic modified polypropylene and
amine-terminated nitrile rubber. The methylol phenolic
5 modified polypropylene of Table 1 (Stocks (a), (b), and (c))
are mixed with a nitrile rubber masterbatch comprising 90
parts nitrile rubber and 10 parts amine-terminated nitrile
rubber. The nitrile rubber is purchased as Hycar~ 1092-80
and the amine-terminated rubber is purchased as Hycar~ ATBN
10 1300X16. The modified polypropylene and the nitrile rubber
masterbatch are mixed in a Brabender mixer at 180C for a
period of about 5 minutes after the modified polypropylene is
melted. In Stock 5, the blend is mixed for 30 minutes before
adding the curative. During mixing, a block copolymer of
15 amine-terminated nitrile rubber and the methylol phenolic
modified polypropylene is formed. The blends are then dynami-
cally vulcanized by the addition of phenolic curative in the
quantities indicated. Mixing is continued until maximum
Brabender consistency is obtained. The compositions are
20 removed from the mixer then returned and mixed for 1
additional minute. The compositions are then cooled in a
press and then compression molded at 210C. Stock 1 is a
control containing unmodified polypropylene. Stock 2
illustrates that very little, if any, block copolymer is
25 formed when polypropylene ~nd dimethylol phenolic material
are masticated without activator. Stocks 3 through 5
ilLustrate compositions of the invention wherein block copoly-
mers are prepared by causing amine-terminated nitrile rubber to
react with polypropylene which had been functionalized with
30 methylol phenolic material in the presence of activator. The
enhanced compatibility (indicated by property improvements)
o~ Stocks 3, 4, and 5, indicates that block copolymer had
formed. For example, the properties of the composition of
Stock 2 are about the same as control Stock 1 except for a
35 slight increase in elongation; whereas, Stocks 3, 4, and 5 show
a substantial increase in both tensile strength and elongation.
,
, ~
~153i~7
43-51-1043A
--16--
-
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11531~7
43-51-1043A
-17-
It is noted that the longer mixing time of Stock 5 results in
a vulcanized blend with extraordinarily high tensile strength.
The extended mixing time probably results in a greater
quantity of block copolymer being formed.
A study of curative levels is illustrated in Table 4.
The compositions are prepared in the same manner as in Table 3,
except the mixing time before curative addition was 10 minutes
and the modified polypropylene, Stock (d) of Table 1, is used.
Also, antidegradants are added and mixed for 1 minute prior
10 to removing the compositions from the mixer. The nitrile
rubber and the amine-terminated nitrile rubber are the same
as used in Table 3. Antidegradant 1 is polymerized 1,~-
dihydro-2,2,4-trimethylquinoline, commercially available as
Flectol~ H antioxidant. Antidegradant 2 is the zinc salt
15 of 2-mercaptotolylimidazole, commercially available as Vanox~
ZMTI. Each of the compositions exhibit an excellent combina-
tion of properties including high tensile strength and a
high ultimate elongation resulting in an excellent true stress
at break. Higher curative levels give better tension set
20 values (lower) but it causes a reduction ir both tensile
strength and elongation.
The effect of the relative proportions of polypropylene
and nitrile rubber are illustrated in Table 5. The ingredients
and the preparation procedures are the same as for the
25 compositions of Table 4. The curative level is kept constant
at 12.5 parts phenolic curative per 100 parts of nitrile
rubber and the antidegradant levels are kept constant at 1.5
parts each by weight per 100 parts by weight of nitrile rubber.
The data show that increasing the amount of modified poly-
30 propylene results in improved tensile strength and higherelongations. Increasing the amount of rubber results in
improved tension set.
- ~15314'7
43-51-1043A
--18--
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llS31~
43-51-1043A
--19--
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1~53147
43-51-1043A
-20-
Compatibilized blends of the invention comprising poly-
ethylene are illustrated in Table 6. Polyethylene having
methylol phenolic groups grafted thereto (modified PE) is
prepared using the procedure, proportions, and ingredients
of Table 1, Stock (d) except high density polyethylene
(Marlex~ EHM 6006) is s,ubstituted for polypropylene. Cured
blends are prepared via dynamic vulcanization as described
in Table 4. Stock 1 is a control containing no block
copolymer. Stock 2 is a blend in which a block copolymer
is formed ln situ between methylol phenolic grafted poly-
ethylene and nitrile rubber. Stock 3 is a blend in which
block copolymer is formed in situ except 10 percent of the
nitrile rubber is replaced by amine-terminated nitrile rubber.
The nitrile rubber and amine-terminated liquid nitrile rubber
(both the same type as in the compositions of Table 3) are
added in the form of a preformed masterbatch. The data show
that the blends containing the in situ formed copolymer exhibit
substantially improved properties, indicative of improved
compatibility.
~153147
43-51-1043A
-~21-
TABLE 6
1 2 3
Polyethylene 50
Modified PE - 50 50
Nitrile Rubber 50 50 45
ATBN-Nitrile Rubber - - 5
SP-1045 3-75 3 75 3 75
SnC12.2H2O 0.5 0.5 0.5
Properties
TS, MPa 10.6 14.8 15.2
E, MPa 196 164 157
Elong., % 75 330 450
Tension Set, % Broke 40 45
TSB, MPa 19 64 84
A study of the effect of the concentration of amine-
terminated nitrile ru~ber in the in situ preparation of a
block copolymer of maleic acid modified polypropylene and
amine-terminated nitrile rubber (ATBN) and the enhanced
compatibility of the resulting polypropylene-nitrile rubber
blends are shown in Table 7. Maleic acid modified poly-
propylene is prepared by melt-mixing at about 185C and about
100 rpm in a Brabender mixer, 100 parts by weight of poly-
propylene (Profax 6723) and 5 parts by weight of maleic acid.
After they are thoroughly mixed, 0.87 parts by weight of
2,5-dimethyl-2,5-bis(t-butylperoxy)hexane (90% active),
(Lupersol~ 101) is added and the mixing speed is increased to
about 150-200 rpm. Mixing is continued until the consistency
levels off (about 3 minutes) and, thus, indicates that
reaction is complete. A nitrile rubber masterbatch, comprising
90 parts by weight of nitrile rubber (Hycar 1092-80) and 10
parts by weight of amine-terminated nitrile rubber (Hycar
1300X16, m.w. about 3000) is prepared by conventional means.
~1531~ ~
43-51-1043A
-22-
Thermoplastic elastomeric compositions are prepared by
dynamic vulcanization. Polypropylene, modified polypropylene,
nitrile rubber, and nitrile rubber masterbatch are mixed in
a Brabender for 5 minutes (stock temperature about 190C).
The blend is removed, then returned to the mixer and mixed
5 additional minutes. The blend is then vulcanized by the
addition of dimethylol-_-octylphenol, SP-1045, and stannous
chloride cure activator. After adding the curative, the
blend is masticated at about 185C until maximum consistency
is achieved. The composition is removed, then returned and
mixed for 2 additional minutes. The composition is removed,
cooled, and then compression molded at 210C. The amount
of nitrile rubber masterbatch is varied as indicated. All
parts are by weight.
The data show that improved compositions are obtained by
the presence of block copolymer. The data show that the amount
of amine-terminated liquid nitrile rubber can be reduced from
10% of the nitrile rubber to 2.5% thereof with the continued
maintenance of the properties of the composition. The amount
of amine-terminated nitrile rubber can be further reduced to
as little as 0.16~ of the nitrile rubber and still a signi-
ficant improvement due to its presence is observed. A plot,
on a log scale, of amine-terminated rubber concentration
versus the improvement in tensile product, ultimate tensile
strength times ultimate elongation, indicates that as little
as 0.1% of the nitrile rubber needed be grafted to a portion
of the polypropylene to give a noticeable improvement in
mechanical properties.
Polypropylene tlOO parts by weight) is modified by 4
parts by weight of a substituted maleic acid, namely,
N-carboxymethyl maleamic acid (CMMA) or N-carbamoyl maleamic
acid (CMA). Lupersol~ 101 peroxide was used to promote
modification, 0.087 parts by weight for CMMA and 0.174 parts
by weight for CMA. $hermoplastic elastomeric compositions are
prepared by dynamic vulcanization following the procedure
and using the nitrile rubber masterbatch of Table 7. The data
are shown in Table 8.
11~3~4~
43-51-1043A
--23--
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115314';J
43-51-1043A
-24-
~ABLE 8
1 2 3
Polypropylene 50 25 25
CMA-modified PP - 25
5 CMMA-modified PP - - 25
NBR-masterbatch 50 50 50
Mixing time before 5 10 5
curative addition, min.
SP-1045 5 5 5
SnC12.2H2O 0.5 0.5 0.5
10 Properties
TS, MPa 9.6 15.6 19.3
Mloo, MPa _ 12.3 12.8
E, MPa 149 147 209
Elong., % 36 270 420
Tension Set, % - 38 43
TSB, MPa 13 58 100
The data show that blends containing block copolymer
derived from amine-terminated nitrile rubber and polypropylene
modified with substituted maleamic acid exhibit improved
properties. The data also indicate that block copolymer from
N-carboxymethyl maleamic acid modified polypropylene gives
superior blends.
The i~portanc~ of first functionalizing the polyolefin
before causing it to react with the nitrile rubber to form
a block copolymer is illustrated in Table 9. Improved
compositions obtained from a block copolymer derived from a
functionalized liquid nitrile rubber are also illustrated.
Stocks 1-4 contain high molecular weight nitrile rubber and
in Stocks 5-8 the nitrile rubber contains ten weight percent
of liquid nitrile rubber, i.e., 45 parts of high m.w. nitrile
rubber and 5 parts of liquid nitrile rubber containing amino
groups. Stocks 1 and 5 are control blends prepared by melt
mixing polypropylene and rubber. Stocks 2 and 6 are also
llS~
- 43-51~1043A
-25-
control blends prepared by treating the blends of Stocks 1
and 4 with the indicated quantities of dimethylolphenolic
material and activator. Stocks 3 and 7 illustrate improved
blends are obtained by first introducing dimethylolphenolic
groups in the polypropylene which subsequently forms a
block copolymer with the nitrile rubber. Stocks 4 and 8
illustrate the additional improvement obtained by dynamic
vulcanization or Stocks 3 and 7. The data show that superior
blends result from the presence of a compatibilizing amount
of block copolymer.
Compatibilized blends containing block copolymer pre-
pared from amorphous polypropylene are shown in Table 10.
A block copolymer is prepared by mixing at 190C, 100 parts
by weight of amorphous polypropylene (Afax~ 900D), 2 parts
by weight of maleic acid and 0.2 parts by weight of an
organic peroxide (L-101). Aftex 5 minutes, 25 parts by
weight of an amine-terminated nitrile rubber (Hycar 1300X16)
are added and mixing is continued for 3 additional minutes.
Compatibilized blends of polypropylene, nitrile rubber, and
block copolymer are prepared and subsequently cured by dyna-
mic vulcanization. Stocks 1 and 3 are controls with the
same quantities of amorphous polypropylene and amine-termin-
ated nitrile rubber as in the block copolymer. The data
show a substantial improvement in properties for Stocks 2
and 4 which contain the block copolymer.
Block copolymers prepared from chlorinated polypropy-
lene and nitrile rubber, and maleic acid modified polypropy-
lene and nitrile rubber containing carboxy groups are
illustrated in Table 11. Polypropylene powder (Profax 6523)
is chlorinated by passing chlorine through it at room
temperature. It is then devolatilized to constant weight
- ~153147
-26- 43-51-1043A
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-27- 43-51-1043A
TABLE 10
L 2 3 4
Polypropylene 46 46 42 42
Amorphous PP 4 - 8
5 Block Copolymer - 5 - 10
Nitrile Rubber 49 49 48 48
ATBN-Nitrile Rubber 1 - 2
SP-1045 3.75 3.75 3.753.75
SnC12 2H2 0.5 0.5 0.50.5
10 Properties
TS, MPa 9.7 11.7 6.711.9
Mloo, MPa - 11.7 - 10.8
E, MPa 175 158 116139
Elong., ~ 30 120 44 160
15 TSB, MPa 13 26 10 31
~lS3147
43-51-1043A
--28--
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~S314~
43-51-1043A
-29-
in an oven at 100C. The treated polypxopylene contains
about 1/2 weight percent chlorine. A 50/50 blend of
c~lorinated-polypropylene and the nitrile rubber master-
batch containing 10~ amine-terminated liquid nitrile
rubber is prepared by melt mixing. During melt mixing,
block copolymer is formed. A thermoplastic-elastomeric
composition is prepared by dynamic vulcanization with
phenolic curative, Stock 2. A similar blend is prepared
with untreated polypropylene, Stock 1. The data show the
blend containing block copolymer exhibits superior
~properties.
Polypropylene is functionalized with maleic acid by
melt mixing 100 parts by weight polypropylene (Profax 6723)
and 5 parts by weight of maleic acid. After a homogeneous
mixture is obtained, one part by weight of organic
peroxide (Lupersol~ 101) is added and mixing is continued
until a constant consistency is obtained. A masterbatch
is prepared by melt mixing 90 parts by weight of virgin
polypropylene, 10 parts by weight of the above maleic acid
modified polypropylene, and 0.15 parts by weight of tri-
ethylenetetramine. A blend of 50 parts by weight oftriethylenetetramine treated, maleic acid modified poly-
propylene masterbatch and 50 parts by weight of carboxy-
nitrile rubber (Hycar~ 1072 CG) were melt mixed during
which time the triethylenetetramine derived moiety forms a
bridge between carboxy groups of the nitrile rubber. The
compatibilized mixture is then dynamically vulcanized with
phenolic curative. Stock 3 is a control with unmodified
polypropylene. The data shows that the compatibilized
composition exhibits substantially improved properties.
llS314~
43-51-1043A
-30-
A block copolymer is prepared by boiling for 15
minutes, one part by weight of maleic acid modified poly-
propylene (same as in Table 7), and one part by weight
of amine-terminated nitrile rubber (Hycar 1300X16) in 86
parts by weight of xylene. After cooling, and by the
addition of an equal volume of acetone, the block copolymer
is precipitated. A compatibilized blend is prepared by
melt mixing and dynamic vulcanization of 49 parts by
weight of polypropylene, one part by weight of the block
copolymer (prepared above), 50 parts by weight of nitrile
rubber, and the indicated amount of phenolic curative.
The properties are shown in Table 11, Stock 6. Stock 5
is a control withou~ block copolymer. The data show a
substantial improvement in properties as the result of the
addition of a small quantity of block copolymer.
An improved compatibilized blend can contain a block
copolymer having a nitrile rubber compatibilizing segment
derived from low molecular weight polyamide. A composi-
tion of the invention is prepared by melt mixing at 190C,
50 parts by weight of phenolic modified polypropylene
(Stock (d) of Table 1), 50 parts by weight of nitrile
rubber (Hycar 1092-80) and one part by weight of low molecu-
lar weight polyamide (Versamid PA 140, amine number 370-
400). The mixture is masticated for ten minutes.
Phenolic curative is then added and the mixture is dynami-
cally vulcanized. Another composition is prepared in a
similar manner except without any polyamide. The properties
are shown in Table 12. The data show a substantial
improvement in tensile strength and elongation indicating
enhanced compatibilization for the composition containing
a block copolymer derived from polyamide.
~S;~
43-51-1043A
-31-
TABLE 12
Modified PP(d) 50 50
Nitrile Rubber 50 50
Versamid*PA 140
SP-1045 2.5 2.5
SnC12 2H20 O . S
Properties
TS, MPa 10.6 14.9
Mlo0, MPa 10.5 11.7
E, NPa 191 204
Elong., % 190 360
TSB, MPa 31 69
Compatibilized blends containing block copolymers
containing various compatibilizing segments are illustrated
in Table 13. A modified nylon block copolymer is prepared
by melt mixing in a Brabender mixer at 230C under nitrogen,
100 parts by weight of nylon 6,6-6, 6-10 copolymer lZytel
_ 63) and 100 parts by weight of a liquid carboxylated
butadiene rubber (Hycar 2000X162). After ~ixing 3 minutes,
ten parts by weight of an epoxy resin (Epon 1007, epoxide
equivalent=2000-2500) are added and mixing is continued
for 5 additional minutes. The nylon block copolymer is
removed, cooled, and used as an additive in Stock 2. Other
block copolymers are prepared in situ by melt mixing the
reactants in a Brabender mixer. The blends are prepared
by melt mixing and dynamic vulcanization as before. The
polypropylene, nitrile rubber, and NBR masterbatch are the
same as in Table 7. Versamid~PA 140 is a liquid polyamide
having an amine value of 370-400 prepared from dimerized
fatty acid and polyamine. Unirez*2641-D is a polyamide,
m.p. 133-143C prepared from dimer acids. CTB rubber is a
liquid carboxylated butadiene rubber (Hycar 2000X162).
* Trademarks
.
~ '
1153147
43-51-1043A
--32--
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~153147
43-51-1043A
-33-
Polycure*1001 is a thermoplastic propylene-acrylic acid
copolymer, m.p. 168C. EEA Resin 455 is an ethylene-
acrylic acid (8~) copolymer, melt index 5.5. Stock 1 is
a control without any block copolymer. The data
(especially the higher elongations) show that the presence
of block copolymer enhances the compatibility between
nitrile rubber and polypropylene.
Although the invention has been illustrated by typical
examples, it is not limited thereto. Changes and modifica-
tions of the examples of the invention herein chosen for
purposes of disclosures can be made which do not constitute
departure from the spirit and scope of the invention.
* Trademark
-
