 |
Description  |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to asphaltic compositions and, in one of its
aspects, relates more particularly to asphaltic compositions which exhibit
improved elastic properties. Still more particularly, in this aspect, the
invention relates to asphaltic compositions exhibiting improved elastic
properties, durability and resistance to deterioration by oil and grease
and improved adhesion to aggregate particles, and suitable for use in such
applications where criteria of suppleness and high mechanical resistance
must be satisfactorily met.
2. Description of the Prior Art
The use of asphalt binders for road-building and other various industrial
applications, is known. These products have, however, heretofore exhibited
weak elastic properties, thus limiting their use in fields where the
aforementioned criteria of suppleness and high mechanical resistance are a
necessary requirement. In this regard, it has, heretofore, been proposed
to incorporate various additives in the asphaltic composition for
increasing the desired elasticity. For such purposes, copolymers of
ethylene and vinyl acetate have been proposed, for example, as disclosed
in U.S. Pat. No. 3,442,841. It is found, however, that although the
incorporation of copolymers of ethylene and vinyl acetate enables the
elasticity of the asphalt to be increased, it also produces asphaltic
compositions which present insufficient cohesion (i.e., stress necessary
for a given deformation) and also weak adhesiveness. In commonly assigned
U.S. Pat. No. 3,821,144 asphaltic compositions having improved cohesive
properties are disclosed, comprising a major amount of asphalt, a minor
amount of a synthetic terpenic resin and a copolymer of ethylene and vinyl
acetate. In this respect, however, it is found that although such
asphaltic compositions exhibit good elastic and cohesive properties,
improved durability and resistance to deterioration by oil and grease and
improved adhesion to aggregate particles are still to be desired.
SUMMARY OF THE INVENTION
In accordance with the present invention, there are provided new and
improved asphaltic compositions, possessing improved elasticity, good
cohesive properties, durability, improved resistance to deterioration by
oil and grease, and improved adhesiveness, rendering these materials
useful in numerous fields of application, including coatings for various
surfaces, metal-work and particularly on orthotropic steel and concrete
bridge deck surfaces and various types of aggregates.
In general, the improved asphaltic compositions of the present invention
comprise a major amount of asphalt, a minor amount of a synthetic terpenic
resin and a minor amount of an interpolymer of ethylene, vinyl acetate and
an organic acid. In its more specific applications, the improved asphaltic
compositions, in general, comprise, by weight, from about 50 to about 94%
asphalt, from about 1 to about 30% of a synthetic terpenic resin and from
about 5 to about 40% of an interpolymer of ethylene, vinyl acetate and an
organic acid.
The synthetic terpenic resins employed in the novel asphaltic compositions
of the present invention, are resins derived from terpenic raw materials
such as turpentine, pine oil, and related materials. The principal
constituent of turpentine is a terpene or pinene. The principal
constituent of pine oil is a mixture of terpene alcohols (largely
alphaterpineol) with small amounts of terpene hydrocarbons and ethers. The
pine oil, for this purpose, is obtained by steamed-distillation of pine
wood. In addition to the recovery of pine oil and turpentine as employed
in the aforementioned process, other terpene hydrocarbons such as
limonene, dipentene, terpinene and terpinolene are also obtained as
intermediate fractions.
The principal methods for producing resinous materials from the
aforementioned substances are by oxidation or by polymerization. In this
respect, it is found that turpentine tends to resinify during storage,
probably because of oxidation. The evaporation of turpentine and pine oils
in open vessels yields resinous materials as a result of oxidation and
polymerization. A more complete description of the aforementioned
synthetic terpenic resins, as employed in the novel asphaltic compositions
of the present invention can be found in "The Chemistry of Synthetic
Resins," by Carleton Ellis, Vol. I, Rheinhold Publishing Corporation, New
York, N.Y., 1935.
The synthetic terpenic resin, employed in the novel asphaltic compositions
of the present invention, preferably has a softening point (Ring and Ball)
from about 50.degree. to about 200.degree.C. Still more particularly
preferred are synthetic resins having a softening point (Ring and Ball)
from about 95.degree. to about 105.degree.C. and a density at 25.degree.C.
of about 0.93.
The asphalt employed in the novel composition preferably has a softening
point (Ring and Ball) from about 50.degree. to about 200.degree.C. Still
more particularly preferred, are asphalts whose softening point is between
about 43.degree. and 60.degree.C. and whose ASTM penetration index as
25.degree.C. is from about 40 to about 70.
The interpolymers of the asphaltic compositions of the present invention
have a melt index of 0.5 to 500 and contain at least 65%, by weight, of
ethylene, at least 5%, by weight, vinyl acetate and from about 0.01 to
about 3%, by weight, of an organic acid. Any organic acid may be employed.
Preferably, the organic acid is selected from the group consisting of
acrylic, methacrylic, itaconic, maleic and fumaric acids; the alkyl
hydrogen maleates and the alkyl hydrogen fumarates; the monoacrylates and
monomethacrylates of glycols; 2-hydroxy-3-amino-propyl allyl ether, allyl
glycerol ether, divinyl glycol, 2-dimethylaminoethyl acrylate,
2-dimethylaminoethyl methacrylate and N-vinyl pyrrolidone. The preparation
of these interpolymers is more fully disclosed in U.S. Pat. No. 3,215,657.
If so desired, the novel asphaltic compositions of the present invention
may be employed, individually as hereinbefore described, or may include
various filler materials and inert aggregates, for imparting additionally
desired properties to the composition. These fillers or aggregates, in
combination with the aforementioned binder (of asphalt, interpolymer and
resin) may comprise from about 85 to about 95%, by weight, of the total
binder-aggregate mixture.
DESCRIPTION OF SPECIFIC EMBODIMENTS
In order to provide a better understanding of the improved properties
realized in the use of the novel asphaltic compositions of the present
invention, a comparison was made between the asphalt binder blends
comprising an asphalt, a synthetic terpenic resin and a copolymer of
ethylene and vinyl acetate, as disclosed in the aforementioned U.S. Pat.
No. 3,821,144, and an asphalt binder blend comprising an asphalt, a
synthetic terpenic resin and an interpolymer of ethylene, vinyl acetate
and an organic acid.
The asphalt employed in each of the aforementioned comparative tests
comprised a pure asphalt having a 120/150 penetration. The copolymer of
ethylene and vinyl acetate comprised approximately 28%, by weight, of
units derived from the vinyl acetate. The interpolymer comprised an
ethylene-vinyl acetatemethacrylic acid interpolymer having a melt index of
6 and containing 27.5%, by weight, vinyl acetate, 0.7%, by weight,
methacrylic acid and 71.8%, by weight, ethylene. The synthetic terpenic
resin had a softening point of 95.degree.C. to 105.degree.C. and a density
at 25.degree.C. of about 0.93, and was obtained by the catalytic
polymerization of alpha and beta pinenes occurring in turpentine. The
respective paving blends are illustrated below in percent by weight:
Blend A Blend B
______________________________________
Asphalt 75 75
Ethylene-vinyl
acetate copolymer
20 --
Ethylene-vinyl acetate-
methacrylic acid
interpolymer -- 20
Terpenic resin 5 5
______________________________________
The individual blends A and B were prepared in the conventional manner, by
first melting the asphalt, blending in the polymer or interpolymer, and,
finally, adding the synthetic terpenic resin.
In order to evaluate the adhesion properties of the binder blends, each
blend was heated to 400.degree.F. and then used to coat aggregate
particles, previously heated to 275.degree.F. These aggregates comprise
typical asphalt hot-mix crushed river paving aggregate gravel. The
aggregate and binders were quickly and thoroughly mixed to yield a mixture
having a uniform distribution of asphalt binder throughout. All aggregate
particles were effectively coated with the binder employing this
procedure. All aggregate particles, previously washed with water and dried
at 275.degree.F., were graded so that they passed through a 3/8 inch sieve
and were retained on a No. 4 sieve. Each paving mixture sample was
prepared employing 94%, by weight, of hot (275.degree.F.) aggregate and
6%, by weight, of individual hot asphalt binder blend. The coated
aggregate was mixed thoroughly to insure complete coverage by the asphalt
binder.
The coated aggregate asphalt paving mixture binder blends were next
subjected to a severe test to develop comparative results of the two
binders relative to adhesion characteristics. The test simply consisted of
subjecting the coated aggregates to six freeze-thaw cycles in 100 cc.
distilled water containing 2 grams NaCl followed by boiling the respective
paving mixes in distilled water for a period of 45 minutes after which the
coated aggregate mixtures were then visually inspected for degree of
coverage. Due to the complex nature of adhesion, the performance of
asphalt-aggregate-water systems, for evaluation of adhesive properties, is
carried out in laboratory tests, employing visual examination of the
aggregate to evaluate binder quality. A substantial difference in adhesive
properties, by such visual evaluation, was noted between the
aforementioned blends A and B. Aggregate particles coated with the
copolymer-containing blend A, showed about 10% of the stripped stone area,
while particles coated with the interpolymer-containing blend B, showed
less than 1% of the stripped stone area visible.
While preferred embodiments of the novel asphaltic compositions of the
present invention have been described for purposes of illustration, it
will be understood that various modifications and adaptations thereof,
which will be obvious to those skilled in the art, may be made without
departing from the spirit of the invention.
* * * * *
|
|
 |
|
 |
Description |
|
