A thermoplastic rubber is made from a mixture of between about 10 percent and about 50 percent of asphalt, between about 5 percent and about 30 percent fluxing oil, and between about 35 percent and about 70 percent of a copolymer of polyethylene and vinyl acetate

Hendel, F. J.

English

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*•
Bonnie L. Henderson
(NASA-Case-NPO-88351) THEEMOPLASTIC fiUBBEB
COHPBISING ETHYLENE-VINYL ACETATE COPOLYHEE
ASPHALT AND FLD2ING OIL Patent (NASA) 3 p
CSCL 11G
00/27
N78-33228
Onclas
33587
https://ntrs.nasa.gov/search.jsp?R=19780025285 2020-03-20T13:52:21+00:00Z
United States Patent Office Patented Jp
3,527,724
THERMOPLASTIC RUBBER COMPRISING ETH-
YLENE-VINYL ACETATE COPOLYMER, AS-
PHALT AND FLUXING OIL
Frank J. Hcndcl, South Pasadena, Calif., assignor to Cali-
fornia Institute Research Foundation, Pasadena, Calif.,
a corporation of California
No Drawingl/Continuatiqn-iiupart of. application-SerTNo.
508j864rNov.J9,.i9t5.-This'application Oet..24, 1966,
<}Ser. No.^88.721 *, ~~~"
^ 'Int. Cl. C08f 37/00, 45/2S, 45/52
U.S. Cl. 260—28.5 1 Claim
The invention described herein was made in the per-
formance of work under NASA contract and is subject to
the provisions of the National Aeronautics and Space
Act of 1958, Public Law 85-568 (72 Slat. 426; 42 U.S.C.
2451), as amended, and is a continuation-in-part of my
copending application Ser. No. 508,864 filed Nov. 19,
1965, now abandoned.
This invention relates to a thermoplastic rubber com-
pound which is easily molded or extruded into different
shapes and objects, applied as a lining metal to concrete
water tanks, swimming pools, as a sealant for coating or
filling cracks in asphalt and concrete roads, especially
•where low temperature is a problem, and as a coating
material such as for ships, soil and water tanks.
Briefly, this invention is a mixture of asphalt, a flux-
ing oil, and a copolymer which includes linear chains of
methylene groups and polar side groups. The thermoplas-
tic rubber of this invention has a very low glass-transi-
tion temperature. For example, it does not become brittle
below 0° F. It has a softening point usually above about
160° F., and there is no exudation of blended ingredients
at any temperature. There is good diffusion and evapora-
tion of volatile light hydrocarbon solvents from it with-
out the formation of pores. It is easily prepared and
inexpensive. It can also be easily added to different for-
mulations to enhance their properties.
Linear polymers without polar side groups, such as the
well-known thermoplastic resin, polyethylene, has been
mixed with petroleum products, but by itself it does not
have good compatibility with petroleum oils such as flux-
ing oil or kerosene. The polyethylene is mixable with the
oil at a high temperature, say 350° F., but on cooling,
exudes a large proportion of the oil.
I have found that the addition of bulky side groups to
the linear polymers makes the polymers completely com-
patible with petroleum products such as fluxing oil and
asphalt which contains asphaltenes. Preferably, the bulky
side groups are polar and include sulphur and oxygen.
Examples of copolymers which provide the linear chain
of methylene groups and the polar side groups are ethyl-
ene and vinyl acetate, ethylene and methyl acrylate, ethyl-
ene and methyl methacrylate. Various homologs of ethyl-
enes, such as propylene, butene, pentene, and butadiene
can be substituted for the ethylene. Apparently the polar
groups on the linear chain interlock with the polar groups
naturally occurring in the asphaltene to form a tough
rubber-like compound which sticks tenaciously to all dry
and roughened surfaces except Teflon (nolytetrafluorocth-
ylene). The presence of the fluxing oil gives the material
10
ABSTRACT OF THE DISCLOSURE
 15
A thermoplastic rubber is made from a mixture of
between about 10% and about 50% of asphalt, between
about 5% and about 30% fluxing oil, and between about
35% and about 70% of a copolymer of polyethylene and
vinyl acetate. 20
25
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60
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70
a softening or melting point below about 200° F. so it
can be melted and cast at a reasonably low temperature.
Acetoxy groups are formed when ethylene is copolymer-
ized wilh vinyl acetate forming a copolymer of clhylene
and vinyl acetate. Ester side groups are formed when
elhylenc is copolymerized with methyl acrylate, methyl
melhacrylate, or the like. Methyl groups in the acetoxy
and ester groups can be replaced by homologs such as
ethyl, propyl or butyl groups.
Polyethylene containing some polyvinylacetate as a co-
polymer shows excellent compatibility with oil and as-
phalt at 250° F. to 350° F. in various proportions. More-
over, on cooling, the result is a tough thermoplastic
elastomer which does not exude oil or asphalt; under
certain circumstances, however, traces of oil and/or as-
phalt may be exuded. The elastomer also retains good
tensile strength and elongation in the temperature rapge
from —50° F. to 150° F. At temperatures below —50°lF.,
the elastomer becomes hard but not brittle. In the pre-
ferred form of the invention, the polyethylene contains
between about 20% and about 30% by weight of vinyl
acetate as a copolymer, and the copolymer is present in
the amount of about 30% to about 70% by weight. The
fluxing oil is present in the amount between about 4%
and about 50% by weight, and the asphalt between
about 10% and about 65% by weight.
These and other aspects of the invention will be more
fully understood from the following examples and de-
tailed description.
EXAMPLE 1
A typical composition of the thermoplastic rubber was
made by mixing 2.7 pounds of ethylene-vinylacetate co-
polymer containing 23.8% polyvinylacetate with .9
pound of steam-refined asphalt of ductility at 77° F. at
150 centimeters, and 1.5 pounds of kerosene having a
specific gravity of 0.79. The copolymer of ethylene and
vinyl acetate was blended with the kerosene and asphalt
at approximately 250° F. until thoroughly mixed. The
mixture was then cooled and cast into open containers.
The cast product had a glass-transition temperature be-
low — 60° F. and a softening point about 200° F. There
was no exudation of blended ingredients at any tempera-
ture.
EXAMPLE 2
A thermoplastic rubber was prepared by mixing the
same ingredients in the same proportions as given in Ex-
ample 1 but adding to it 4.5 parts by weight of normal
hexane. All of the ingredients of Example 1 were heated
with the solvent in a reflux condenser for two to three
hours un t i l a homogenized mixture was obtained. The
mixture was then cooled and sprayed with air on to
wooden and metallic surfaces. Addition of the solvent fa-
cilitates using the elastomer in various coating applica-
tions.
EXAMPLE 3
Another typical composition of the thermoplastic rub-
ber was made by mixing 0.9 pound of semisolid steam-
refined asphalt of ductility at 77° F. greater than 150
centimeters, and 0.1 pound of fluxing oil, which was a
heavy hydrocarbon oil of 0.945 specific gravity and vis-
cosity at 210° F.—70 S.S.U. obtained from the distilla-
tion of crude oil. To the above mix 1.0 pound of co-
polymer of 72% by weight of ethylene and 28% by
weight of vinyl acetate. The copolymer was in the form
of pellets 3/B to Vs inch in size. Blending was achieved
by leaving the entire mix in a 250° F. electric oven over-
night and mixing it vigorously next morning. After cool-
ing to room temperature a thermoplastic rubber was
achieved.
3
EXAMPLE
3,527,724
Ajhermoplastic rubber composition was made by mix-
ing 10 pounds of steam-refined asphalt with 1.5 pounds of
fluxing oil, both as in Example 3, and 11.5 pounds of a
copolymer of ethylenc and propylene. blending was
achieved by leaving the entire mix in a 275° F. electric
oven over night and mixing it vigorously next day at the
same temperature. After cooling to room temperature a
a thermoplastic rubber was achieved.
EXAMPLE 5
A thermoplastic rubber composition was made by mix-
ing 12 pounds of steam-refined asphalt of ducti l i ty at 77°
F. of 100 centimeters, 1 pound of fluxing oil, as in Ex-
ample 3, and 7 pounds of linear polyethylene, containing
25% by weight of pendent vinyl acetate groups. Blending
was achieved by preheating the mix to 250° F. and mixing
it vigorously at the same temperature. After cooling to
room temperature a thermoplastic rubber was achieved,
which was, however, softer than the one in Example 4.
EXAMPLE 6
A thermoplastic rubber composition was made by blend-
ing 5 pounds of steam-refined asphalt wi!h 0.5 pound of
fluxing oil, and with 10 pounds of a copolymer of ethylene
and vinyl acetate at 275° F. and afterwards cooling the
blend to room temperature. All raw materials were the
same as in Example 4. The thermoplastic rubber was
much stronger and harder than the product of Exam-
ple 4.
EXAMPLE 7 .
A thermoplastic rubber composition was as in Exam-
ple 5, except kerosene was substituted for the fluxing oil.
The product had good physical properties at low tcm-
peratures.
EXAMPLE 8
Thermoplastic tiles were made.by casting at 270° F.
the molten thermoplastic rubber prepared in Examples 1
through 5 into a horizontal mold 6 inches x 6 inches x !/6
inch lined with Teflon. The mold and the thermoplastic
rubber were held over night in an electric oven kept at
270° F. Next day the mold was removed and submerged
in cold water to cool quickly the mold and the product.
The product, a flexible, black l i lc , was easily removed
from the mold because the thermoplastic rubber does not
adhere to Teflon.
EXAMPLE 9
Another thermoplastic rubber tile was prepared as in
Example 8 except a steel-wire screen 18 mesh (m;ule of
0.025 inch wire) with 0.03 inch openings was embedded
in the molten rubber. The product was much less flexible
but of much greater tensile strength.
EXAMPLE 10
A thermoplastic rubber rod of % inch diameter was
prepared by extrusion at 250° F. of the molten thermo-
plastic rubber of Example 3 under pressure into cold
water where it congealed.
EXAMPLE 11
Thermoplastic rubber Va inch pellets were prepared
by extruding molten thermoplastic rubber of Example 3
at 240° F. under pressure through a Vs inch opening and
cutting the congealed, continuous, thin rod into Ys incn
lengths.
EXAMPLE 12
A thermoplastic ruber strip 5 inches wide x % inch
thick was prepared by extruding the molten thermoplastic
rubber of Example 3 at 250° F. under pressure into cold
water where it congealed. The above strip was reheated
on the lop surface with infrared heat so that it became
tacky. The tacky surface was then covered with crushed
while stone to form-a white surface..The bottom surface
i
JO
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40
(JO
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was then reheated and in a tacky condition was applied
to a concrete road and an asphalt road to form a divid-
ing white line on each road.
EXAMPLE 13
A strip as in Example 12 was made tacky by heat and
covered with ground glass to form a white road line which
reflects car l ights at night.
EXAMPLE 14
A strip as in Example 12 was laid cold on a preheated
concrete and an asphalt road. After rolling the strip ad-
hered to the roads, the strips were then sprinkled with
•liot white sand or white crushed stone, which was then
rolled so it adhered very strongly to the thermoplastic
strip. Other colors, such as yellow, can be used. An anti-
skid highway or runway can be prepared the same way.
EXAMPLE 15
Thermoplastic pellets from Example 11 were mixed
with crushed stones (aggregates) and spread on an even
surface, simulating a road substratum. Heat was then
applied from top in order to melt the thermoplastic pellets.
A cold asphalt-water emulsion was then placed on top
of the thermoplastic-aggregate layer to provide a leveling
medium (after the evaporation or running off the water).
A simulated durable road surface was then achieved.
EXAMPLE 16
Cracks in an asphalt road, a concrete road, and in a
tennis court were filled with finely divided dense-grade
aggregates, followed by the molten thermoplastic rubber
of Example 3, and topped with sand. Effective and durable
patching wilh this combination was achieved.
EXAMPLE 17
A strip prepared like in Example 12 but only V4 inch
thick was first made tacky on the bottom and laid on top
of a leaky roof. Then the top of the strip was made
tacky and covered with dense-grade aggregate to provide
an effective and durable roof patching with this sealant.
EXAMPLE 18
Holes at the apex of a leaky roof were covered as in
Example 17 with the exception that the thermoplastic
slrip was prc-hcatcd and bent to make it fit the V-shaped
apex.
EXAMPLE 19
A cubical water tank was made by taking five Va, inch
square strips of the thermoplastic rubber of Example 3
and joining their ends simply by heating these ends with
an infrared heater. The tank was impervious to water and
algae which did not grow on the walls.
EXAMPLE 20
The water tank of Example 19 was painted with ordi-
nary paints to the desired color. Small ceramic tiles were
embedded two inches from the top on all sides simply by
warming the thermoplastic rubber walls with an infrared
heater to make them tacky and sticking the ceramic
tiles on,
EXAMPLE 21
A letter was sealed by taking a chunk of thermoplastic
rubber and heating it over a match (or candle) until the
end of the thermoplastic rubber melted (and was slightly
burning) and was dripping on the letter. A metallic seal
was then wetted with water (or saliva) and impressed on
the tacky or semi-liquid rubber.
EXAMPLE 22
A thermoplastic rubber strip was prepared, as in Ex-
ample 12, except that the top tacky surface was covered
with sawdust and that the bottom surface was not made
tacky. Several of such strips were heated (by infrared)
at the ends and joined to make a wider and longer portable
3,527,724
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15
surface for children's playground and for sport events
(like tennis courts, running tracks, etc.).
EXAMPLE 23
A weather proof highway is built by sandwiching a
thermoplastic rubber sheet about Va, inch thick made in
accordance with Example 3 .and reinforced with a metal
screen of about 18 mesh (1 millimeter openings) between
layers of a conventional asphalt highway or street.
In a typical highway, a subgrade material is disposed on
the earth and covered by a coarse aggregate base, which
is in turn covered by an asphalt concrete binder with a
coarse aggregate base, which is in turn covered by an
asphalt concrete binder with a coarse aggregate in it.
The reinforced thermoplastic rubber sheet.of this inven-
tion is placed on top of the asphaltic concrete binder,
and then covered with the conventional asphultic cement
surface to a depth of about l'/i inches. In the past, the
asphaltic surface has tended to crack so that water pene- 20
trates it. The water freezes, expands, and opens the
cracks so that water can percolate down through the sur-
face and wash out the underlying support. The layer of
thermoplastic rubber in accordance with this invention
prevents the penetration of water to the road base, and 25
preserves the road even though the surface is open by
cracks.
For the purpose of this invention, the term "fluxing
oil" is used to mean a heavy hydrocarbon petroleum dis-
til lation product generally having a boiling point between
about 150° F. and about 500° F., and having between
about six and about thir ty carbon atoms per molecule. The
asphalt which can be used with the f lux ing oil is the con-
ventional asphaltic residue in a petroleum still.
The volatile solvent used in diluting the thermoplastic
rubber includes compounds such as pentane, hexane, and
heptane, and generally has a boiling point between about
96° F. and about 212° F.
The copolymer of ethylene and vinyl acetate is prefer-
ably present in the thermoplastic rubber in the amount of 40
about 53%, but can vary between about 30% and about
70%. The product loses its strength if the copolymer is
much less than 30%, and does not have the desired re-
siliency if the copolymer is more than about 70%. Prefer-
ably the copolymer has a molecular weight greater than 4*>
about 2000, and a crystallinity less than about 40%.
Between about 20% and about 30% polyvinylacetate
in the copolymer is required for the desired properties. If
the vinyl acetate is much below this range, the product
does not have the desired resiliency. If the vinyl acetate is
much more than about 30% of the copolymer, the product
has less than the desired strength.
The fluxing oil or kerosene can be varied between about
5% and about 50%. If it is less than about 5%, the
product does not have the desired resiliency, and if it is
more than about 50%, the product is lacking in the de-
sired strength. Asphalt is added to the thermoplastic rub-
ber composition in the amount between about 10% up
to about 60% by weight to combine with the resin and
produce the tough rubber-like composition of this inven-
tion.
30
35
^J
Tlic advantageous characteristics of the thermoplastic
elastomer of this invention are:
(1) It has a very low glass-transition temperature below
(0° -R);
(2) It has a softening point above 200° F.;
(3) It has no exudation of blended ingredients at any
temperature;
(4) It has good diffusion and evaporation of light volatile
hydrocarbon solvents from the elastomer without the
formation of pores;
(5) It has low cost;
(6) It has ease of preparation of different formulations;
(7) It has ease of addition of various fillers;
(8) It has ease of molding and extrusion of different
objects;
(9) It is easily applied as a liner or coating to con-
crete Umks and swimming pools, and as a sealant for
filling cracks in asphalt and concrete roads, especially,
where low temperature is a problem; and
(10) It can be sprayed with or without volatile solvents
by a stream of hot or cold pressurized air or other
gases or vapors. Thus a soil may be stabilized to prevent
dust and mud, and the hulls of boats and ships may be
covered wi th a protective layer of this material to
prevent corrosion and organic growth.
I claim:
1. A thermoplastic rubber comprising a mixture of a
copolymer of ethylene and vinyl acetate in which the vinyl
acetate is present in the amount between about 20%
and about 30% by weight of the copolymer, asphaltic
residue from a petroleum still, and hydrocarbon petroleum
dist i l la t ion product having a boiling point between about
150° F. and about 500° F. and having between about
six and* about thirty carbon atoms per molecule, the
copolymer being present between about 35% and about
70% by weight of the mixture, the copolymer having a
molecular weight greater than about 2000, and a crystalli-
nity less than about 40%, the asphaltic residue being
present between about 10% and about 50% by weight of
the mixture, and the petroleum product being present
in the amount between about 5% and about 30% by
weight of the mixture.
50
60
References Cited
UNITED STATES PATENTS
2,783,162 2/1957 Mollring 106—278
3,010,899 11/1961 Boyer.
3,249,567 5/1966 Vigneault.
3,291,767 12/1966 Zaayenga 106—279
3,414,533 12/1968 Trieschmann et al 260—28.5
FOREIGN PATENTS
642,091 7/1964 Belgium.
969,169 9/1964 Great Britain.
6,413,985 6/1965 Netherlands.
ALLAN LIEBERMAN, Primary Examiner
U.S. Cl. X.R.
260—33.6


Thermoplastic rubber comprising ethylene-vinyl acetate copolymer, asphalt and fluxing oil

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