Note: Descriptions are shown in the official language in which they were submitted.
~138608
I
HEAT RESISTANT BUTADIENE/ACRYLONITRILE-POLYVINYL
CHLORIDE BLENDS
Technical Field
An improved butadiene/acrylonitrile blend with
polyvinyl chloride that exhibits superior heat
resistance at temperatures of 125C and higher for
longer times are obt~;n~hle with polymer bound
antioxidants of butadiene/acrylonitrile blended with
ultra high molecular weight polyvinyl chloride. These
antioxidants bound butadiene/acrylonitrile copolymers
are fluxed with high molecular weight polyvinyl
chloride (PVC) at a temperature sufficient to fuse the
PVC to give a blend that has better aging resistance
than obtained with conventional NBR/PVC blend and
better compression set.
Background Art
Fluxed nitrile/PVC blends have been used for a
number of years in oil and fuel resistant applications
requiring tough ozone and abrasion resistant products.
They are easily processed and cured, economical in
cost, and can be used in brightly colored compounds,
as well as black. Unfortunately, they are limited to
100C and lower usage.
The conventional NBR/PVC compounds are used in
hose jackets, wire and cable covers, shoe soles, and
blown closed cell sponge insulation and athletic
padding. They are often used competitively at
temperatures below 100C against polychloroprene,
chlorinated polyethylene, and chlorosulfonated
polyethylene depending upon the application
requirements.
Nitrile/PVC blends have better oil and fuel
resistance than their competitive counterparts, but
are not as good in compression set resistance due to
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the th~rmoplastic nature of PVC. They are equivalent
to chloroprene in heat resistance, but not as good as
chlorinated polyethylene and chlorosulfonated
polyethylene as they have a temperature limit of
essentially 100C which has limited their use to
service where the temperature is less than 100C.
Summary of the Invention
I have discovered that it is possible to step up
from 100C heat resistance to 135C using polymer
bound antioxidant stable butadiene/acrylonitrile, viz.
CHEMIGUM HR terpolymers with high intrinsic viscosity
PVC. Compounding is the same, processing and
versatile cure capability are the same as with
conventional NBR/PVC blends, but heat aging capability
at 135C is improved beyond that of conventional
nitrile rubber/PVC based blends. Therefore, these new
blends are more competitive with the currently used
exotic polymers at service temperatures of 135C.
Compounded physical properties of RCV 7490, a
70/30 blend of antioxidant bound butadiene
acrylonitrile/polyvinyl chloride of high intrinsic
viscosity and commercial Paracril OZ0, a blend of
acrylonitrile/butadiene/polyvinyl chloride of less
than 1.5 intrinsic viscosity in black and white filled
compounds are shown in the Table. RCV 7490 exhibits a
faster cure rate with adequate scorch safety, and
original physical properties are similar.
Both polymer blends exhibit adequate static ozone
resistan-ce, but RCV 7490 demonstrates dynamic ozone
resistance whereas Paracril OZ0 does not; cracking was
observed after 24 hours with Paracril OZ0 blend at
elevated temperatures.
ASTM No. 1 oil embrittles both blends. RCV 7490
is better in ASTM No. 3 oil, Fuel C with water aging,
and Fuel C with ethanol. Low temperature stiffening
-213860~
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iæ similar, but Paracril OZO is slightly better in
impact brittleness, believed to be due to a slightly
lower acrylonitrile content than in RCV 7490 at
temperatures less than 100C.
The real separating characteristics between these
blends is shown in 121C heat age resistance. The
black loaded RCV 7490 compound losses 70~ of its
Elongation in 15 days at 121C, while the Paracril OZO
is brittle. These black loaded compounds may have
extra stabilizing antioxidant added to them and the
plasticizer also adds some synergistic stabilizing
characteristics to them. The white filled compounds
do not contain added stabilizing ingredients, and here
is where a great difference is seen in the blends.
RVC 7490 losses 45~ of its Elongation in 20 days aging
at 121C, whereas Paracril OZO losses 45% Elongation
in 3 days, and is brittle in 10 days. Thus, it is
apparent that blends of polymer bound antioxidant with
high intrinsic viscosity polyvinyl chloride has
greatly stabilized the blend at elevated temperature
and, thus, my invention has useful service at higher
temperatures .
Further, the white filled RCV 7490 compound can
withstand 7 days air oven aging at 135C with 55
Elongation loss and 1.5 days at 150C to 55~
Elongation loss whereas the Paracril OZO blend of the
prior art is brittle and severely cracked.
As is seen from the data of the Table polymer
bound antioxidant stabilized
polyacrylonitrile/butadiene i8 different from the
prior art polyacrylonitrile/butadiene in fluxed
polyvinylchloride blends. The fused polyvinyl
chloride bound antioxidant stabilized
polyacrylonitrile/butadiene blend has improved
compression set resistance when the polyvinyl chloride
has intrinsic viscosity of 1.5 preferably 1.7 and
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higher relative to the blends where the intrinsic
viscosity of polyvinyl chloride is less than 1.4. The
fused blends of this invention offer improved heat age
resistance as evidenced by the percent change in
elongation with from 0 to 15 days at 121C and the
change in hardness as the blends tend to resinify.
Selected antioxidants and polyvinyl chloride of
intrinsic viscosity of 1.5 and higher contribute to
improved compression set resistance and heat aging of
the resulting blends.
The necessary cure system are those that cure the
acrylonitrile/butadiene rubber. The resulting
cured/fused blends have satisfactory ozone resistance
when polyvinyl chloride has an intrinsic viscosity of
at least 0.8 to 1.5 and preferably of 1.6 and as high
as 1.7. These pre-defined polyvinyl chlorides are
represented by tradename Oxy 200 PVC to Oxy 400 PVC
products. The well-known bound antioxidant
acrylonitrile butadiene rubbers are especially
preferred in this invention as they offer greatly
improved resistance to degrading by resinification
which has been a problem with exposure to hot fuels
and oils.
These bound antioxidant acrylonitrile/butadiene
rubbers are usually made by dissolving the bound
antioxidant monomer such N(4-anilinophenyl)
methacrylamide in small amount of the acrylonitrile
and the solution is pumped into the usual
polymerization mixture of acrylonitrile and butadiene
as specifically explained in Table 2 of James W.
Horvath's article "Bound Antioxidants Stabilized NBR
in Automobile Applications r on pages 19-62,
Elastomerics, August, 1979. The nature of these
monomers useful for preparing bound antioxidant
acrylonitrile/butadiene polymers are further described
in the article by R. H. Kline, presented at the
2~86~8
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meeting of the Rubber Division, American Chemistry
Society, Toronto, C~n~, May 7-10, 1974.
Specifically these monomers belong to the two classes
of phenolic and amine types polymerizable unsaturated
monomer. The above two references are incorporated
herein to supply the disclosure of these monomers and
their bound antioxidant acrylonitrile/butadiene
rubbers produced therefrom normally about 1 to 6~ by
weight of bound antioxidant in acrylonitrile/butadiene
polymer is satisfactory but 1.5 to 3~ is preferred.
The bound antioxidant monomer can be used with
high molecular weight PVC to produce bound antioxidant
polymer blends of unusual properties when fused.
The nature of this invention and its advantages
are further disclosed and illustrated by the following
- illustrative and exemplar examples as set forth in
attached Table where all parts are by weight unless
otherwise indicated.
St~n~rd ASTM test procedures were used
throughout the testing, except where indicated. ASTM
D 3182 was used for sample preparation, ASTM D 2084
for vulcanization characteristics, ASTM D 412 for
physical properties, ASTM D 295 for Compression Set,
and ASTM D 471 for fluid aging. Ozone testing was
done in an Orec Ozone Chamber at 50 pphm ozone
concentration at 38C. Bent Loop and 20~ Stretched
Samples were studied.
Polymer blends were prepared with high
temperature m; ~; ng of the acrylonitrile/butadiene
bound antioxidant rubber with polyvinylchoride and the
known PVC stabilizer. The polymers were then
compounded in a water cooled Banbury. Curatives were
added in a second Banbury pass. No special mix
precautions or procedures were attempted in mixing the
blends.
21386~8
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The initial screening of polyvinyl chloride and
acrylonitrile/butadiene bound antioxidant terpolymer
blends was done in black loaded compounds. In later
runs white loading was used. These formulations and
associated data are in the following Table.
Table 1
Comparison of RCV 7490 wit~ Commercial NBR/PVC (Paracr_l OZO)
BX9J 34240332401342303342301
RCV 7490, HR 662/PVC 158.0 158.0
Paracril OZO 150.0 150.0
Zinc Oxide 4.0 4.0 5.0 5.0
Stearic Acid 0.5 0.5 0.5 0.5
SRF Black 50.0 50.0
Hi-Sil 243 LD 50.0 50.0
Paraplex G62 5.0 5.0 5.0 5.0
Vulkanol OT 10.0 10.0
Vanfre AP-2 2.0 2.0
Paraplex G-57 10.0 10.0
Rutile TiC~ 1.0 1.0
AC-629 A polyethylene 1.0 1.0
Carbowax 3350 1.0 1.0
HVA-2 2.0 2.0
Ultranox 626 0.5 0.5
Ultranox 276 0.5 0.5
Spider Brand Sulfur 0.5 0.5 0.5 0.5
Methyl Tuads 2.0 2.0 2.0 2.0
Altax 1.0 1.0 1.0 1.0
1234.0 1226.0 1249.4 241.4
~138~0~
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Table 1
Comparison of RCV 7490 with Commercial NBR/PVC (Paracril 020)
Oriqinal Pro~erties
Tensile, NPa (pBi)18.6816.9417.017.41
(2708)(2456)(2466)(2525)
Elongation 593 584 702 744
100~ Nodulus 3.1 3.3 2.1 2.3
(443) (482) (306)(338)
200~ Modulus 5.9 6.3 3.2 3.4
(856) (908) (464)(496)
300~ Nodulu8 8.5 8.7 4.3 4.5
(1231)(1261) (618)(657)
Shore A Hardness 64 66 70 74
Tear Strength, die C, 42.6 38.0 48.9 48.0
kN/m
Compression Set B, 22 hrs33.229.650.0 54.3
~ 100C
BX9J 342403342401342303342301
Static Ozone Resistancepass pass pass pass
20~ stretch, 50 pphm,
40C, 7 days
Static Ozone Resistance,passpass pass pass
Bent Loop, 50 pphm, 40C,
7 days
Dynamic Ozone Resistance, pass 24 hrs pass 24 hrs
50 pphm, 40C, 7 days
ASTN No 1 Oil, 70 hrs ~ 150C
Tensile, NPa (p6i) ~ 178 87 103 6
change
Elongation 3 21 9 28
Shore A Hardness 97 97 98 97
points change 33 31 28 23
~ Volume Swell -16.9 -10.4 -13.6 -7.0
ASTN No. 3 Oil, 70 hrs ~ 150C
Tensile, NPa (psi)23.931.8 11.2 7.4
Elongation 123 11 428 456
Shore A Hardness 92 95 78 70
points change 28 29 8 -4
~ Volume Swell 1.4 3.9 7.6 18.7
~8~
~ - 8 -
Table 1
Comparison of RCV 7490 with Commercial NBR/PVC (Paracril OZO)
ASTM Ref. Fuel C, 70 hrs ~ 23C
Tensile, MPa (psi) -65 -68 -63 -75
~ change
Shore A Hardness 46 45 40 36
points change -18 -21 -30 -38
~ Volume Swell 43.2 55.0 41.5 59.6
ASTM Ref. Fuel C + 15~ Bth nol, 70 hrs ~ 23C
Tensile, MPa ~ change -69 -71 -80 -80
Shore A Hardness 42 42 34 30
points change -22 -24 -36 -44
~ Volume Swell 54.7 69.5 59.4 84.5
Distilled Water, 70 hrs. ~ :80F
Tensile, MPa (psi) -3 -5 -14 -22
~-change
Shore A Hardness 62 63 61 65
points change -2 -3 -9 -9
~ Volume Swell 6.3 9.1 11.2 16.2
BX9J 342403342401342303342301
Solenoid Brittleness, C-37.9 -49.9 -17.5 -28.9
21386~8
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LIST OF INGREDIENTS AND THEIR NATURE USED IN THE TABLE
RCV 7490 70/30 CHEMIGUM HR662 antioxidant bound
acrylonitrile/butadiene PVC, The
Goodyear Chemical Division
Paracril OZO 70/30 NBR/PVC blend no bound
antioxidant, Uniroyal Chemical Co.
Zinc oxide
Stearic acid
ASTM N-762 black
Hi-Sil, 243LD hydrated amorphous silica
HVA-2 N,N'-m-phenylenediamaleimide
Paraplex G-62 epoxy soya oil
Vulkanol OT ether-thio-ether plasticizer
Paraplex G-57 polyester plasticizer
Rutile TiO2 titanium oxide
AC-629A polyethylene, Allied Chemical
Carbowax 3350 polyethylene glycol
Vanfre AP-2 85 Cm.p. proprietary process aid, R. T.
Vanderbilt
Ultranox 626 bis(2,4-di-t-
butylphenyl)Pentaerythritol Diphosphite
Ultranox 276 Octadecyl3,5di-tert-butyl-4-
hydroxyhydroc;nn~m~te
Spider Brand magnesium oxide treated sulfur,
Sulfur Co. Stauffer Chemical Co.
Methyl Tuads Tetramethylthiuram disulfide
Altax Benzothiazyl disulfide
2138608
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. While certain representative embodiments and
details have been shown for the purpose of
illustrating the invention, it will be apparent to
those skilled in this art that various changes and
modifications may be made therein without departing
from the spirit or scope of the invention.
