Primer composition

A primer composition for use in the bonding of asphalts comprising the reaction product of an elastomer and a terpene resin. The primer composition of this invention can be used in the treatment of substrates to which asphalts are bonded to improve the bonding relationship between the substrate and the asphalt, such as in road-paving applications, roofing applications and the like.

This invention relates to primer compositions, and more specifically to 
primer compositions for use in improving the bonding relationship between 
asphalts and substrates to which the asphalts are bonded. 
In copending application Ser. No. 167,986, filed July 14, 1980 now 
abandoned, the disclosure of which is incorporated herein by reference, 
there is disclosed a chemically-modified asphalt composition which is 
suitable for use as an adhesive. The adhesive composition described in the 
foregoing application is prepared by reacting an asphalt with a 
polymerizable vinyl aromatic monomer such as styrene and a depolymerized 
rubber, either alone or in combination with a rubbery polymer, and 
optionally a terpene resin. The resulting composition has been found to be 
highly suitable in bonding a rubberized asphalt composite reinforced with 
glass fibers to a substrate in, for example, road-paving, road repair and 
roofing applications. 
It has now been found that the adhesion between the composites coated with 
the chemically-modified asphalt as described in the foregoing application 
and a substrate can be significantly increased where the substrate is 
treated with a primer composition which is compatible with the asphalt and 
with the substrate. 
It is accordingly an object of the present invention to provide a primer 
composition for use in improving the bonding relationship between asphalt 
adhesives and substrates to which they are bonded. 
It is a more specific object of the present invention to provide a primer 
composition for use in the coating of substrates to deposit on the 
substrate a modified rubber composition to improve the bonding 
relationship between the asphalt and the substrate. 
The concepts of the present invention reside in a primer composition for 
use in improving the bonding of asphalt to substrates wherein the primer 
composition is prepared by reacting an elastomer with a terpene resin. It 
has been found that the primer composition of this invention, when applied 
to a substrate to which a chemically-modified asphalt is to be bonded, 
serves to increase the adhesion between the chemically-modified asphalt 
and the substrate and to decrease the temperature at which adhesion 
between the substrate and the asphalt composite can be effected. 
In the practice of the present invention, an elastomer is reacted with a 
terpene resin, and the resulting composition is then dispersed in a 
suitable solvent, thus permitting the reaction product to be applied as a 
coating on the surface of the substrate to which the rubberized asphalt 
composite is to be bonded. The elastomer employed as one of the reactants 
in the present invention is preferably a depolymerized rubber. The term 
"depolymerized rubber", as used herein, is intended to include and refer 
to a number of commercially available, low molecular weight natural and 
synthetic polymers. Depolymerized rubbers are generally rubbers which have 
been depolymerized to reduce their molecular weight by treatment with a 
depolymerizing agent, such as alkali; the rubbers which can be 
depolymerized include not only natural rubber but also synthetic rubbers, 
such as depolymerized synthetic conjugated diene polymers (e.g., 
depolymerized synthetic polyisoprene, depolymerized synthetic 
polybutadiene and depolymerized synthetic polychloroprene). Generally, 
depolymerized rubbers employed in the practice of this invention have 
average molecular weights ranging from 10,000 to 110,000. Various 
depolymerized rubbers are available commercially, including depolymerized 
rubbers available from Hardman Chemicals under the trademarks "Isolene", 
which are comprised of a series of depolymerized virgin synthetic 
polyisoprene polymers and the various "DPR" rubbers which are 
depolymerized natural rubbers. In general, such depolymerized rubbers are 
in the liquid state at ambient temperatures, and are quite tacky. 
The depolymerized rubbers as described above are reacted with a terpene 
resin which can be any one of a number of synthetic polyterpene resins 
commercially available. Suitable resins include the polyterpene resins 
marketed by Goodyear Chemicals under the trademark "Wingtack", including 
the Wingtack 95 resin, a synthetic polyterpene derived from C.sub.5 
hydrocarbon resins. Another Wingtack resin useful in the practice of this 
invention is Wingtack 115, a resin chemically similar to Wingtack 95, 
except that Wingtack 115 has been polymerized to a higher softening point. 
Another series of terpene resins suitable for use in the practice of this 
invention are the terpene resins manufactured by the Hercules Incorporated 
under the trademark "Piccolyte", including the A100, A115, A125 and A135 
resins. These are derived from the monomer alpha-pinene. Yet another 
series of terpene resins which can be used in the practice of this 
invention are the terpene resins marketed by Neville Chemical Company 
under the trademark "Nevpene", such as Nevpene 9500. 
The reaction is carried out by simply blending the rubber and the 
polyterpene resin at a temperature sufficient to enable the reaction 
between the two to take place. In general, use can be made of reaction 
temperatures ranging from 50.degree.-300.degree. F., with higher 
temperatures being possible to provide reduced reaction times. 
The relative proportions between the rubber and the terpene resin can be 
varied within wide ranges, and generally are not critical to the practice 
of the invention. In general, best results are usually obtained when the 
composition is formulated of 5-40% by weight of the rubber and 95-60% by 
weight of the polyterpene resin. If desired, suitable solvents for the 
reactants can be employed in carrying out the invention. In general, when 
use is made of a solvent for each of the two reactants, the solvent is a 
hydrocarbon, hexane being frequently preferred. 
It is also possible, and sometimes desirable, to include in the reaction 
mixture, a non-depolymerized elastomer. As the non-depolymerized rubber or 
elastomer, use can be made of a number of elastomeric materials well known 
to those skilled in the art. Included are both natural rubbers and 
synthetic rubbers. Suitable synthetic rubbers are homopolymers of 
conjugated dienes (i.e., butadiene, isoprene, chloroprene, etc.) as well 
as elastomeric materials formed by copolymerization of one or more of the 
foregoing conjugated dienes with one or more ethylenic monomers such as 
styrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, 
etc. Included in the latter category are butadiene-styrene rubbers, 
butadiene-acrylonitrile rubbers and acrylonitrile-butadiene-styrene 
rubbers. Particularly well suited for use in the practice of this 
invention when a non-depolymerized rubber is employed is the 
butadiene-styrene rubber marketed by Philips Petroleum under the trademark 
"Solprene 1205C". 
The amount of the non-depolymerized elastomer is similarly not critical to 
the practice of the invention, and can be varied within relatively wide 
ranges. In general, good results are obtained when the non-depolymerized 
rubber varies from 1 to 30% by weight of the composition based on the 
total weight of the composition. 
As is indicated above, the primer composition of this invention is 
particularly useful as a primer to secure a bonding relationship between a 
glass fiber-asphalt composite of the sort described in the foregoing 
copending application Ser. No. 167,986 now abandoned. As described in that 
application, the composite is formed of a bundle of glass fibers which has 
been coated, or impregnated, with a non-tacky rubber-modified asphalt 
composition of the type described in copending application Ser. No. 
045,047, filed June 4, 1979. In general, the bundle of glass fibers 
serving as reinforcement for the non-tacky rubber-modified asphalt are 
preferably present in the form of a woven roving such that the composite 
has the configuration of a road repair laminant, mat or membrane to be 
laid down over a substrate whereby the mat is then overlaid with, for 
example, a wear surface of, for example, asphalt. To insure adhesion 
between the composite and the substrate there is an adhesive coating on 
one surface of the mat, with the adhesive coating being formed of the 
reaction product of asphalt, a polymerizable vinyl aromatic monomer and 
depolylmerized rubber as described in copending application Ser. No. 
167,986 (now abandoned). As described in that copending application, the 
reaction product may also be blended with a terpene resin to enhance the 
tackiness of the coating as an adhesive. 
The primer composition of this invention is simply applied as a thin 
coating on the substrate, whether it be a concrete, asphalt or brick 
substrate. The primer composition of this invention thus serves to coat 
the substrate and is compatible with the adhesive coating on drying to 
insure that the mat having the adhesive coating on one face thereof is 
securely bonded to the substrate. 
For that purpose, the substrate should be coated with a quantity of the 
primer composition of this invention to establish a secure bonding 
relationship between the substrate and the adhesive coating on the mat. In 
general, the coating has a minimum thickness of 1 mil, and can range up to 
an inch or more, although thick coatings of the primer composition of the 
invention generally afford no greater advantage. 
Preferably the primer compositions of the present invention are applied 
unto a substrate as a solvent solution suitably containing about 5-15% by 
weight of solids. Outstanding results are obtained using 10-12% solids. 
Numerous solvents including aromatics, e.g. xylene, toluene, naptha, 
alkanols including cyclic alkanols like cydohexanol, aliphatics including 
hydrocarbons and chlorinated hydrocarbons are suitable. Hexane is an 
especially outstanding solvent as it has the needed solvation power and 
presents a fine balance between a short drying, or evaporation time, and a 
relatively high flash point. 
In the preferred mode of practicing this invention roads are repaired, or 
even constructed, by applying the primer composition to a road substrate, 
e.g. concrete, asphalt, brick and the like, and after solvent evaporation 
a road repair membrane is positioned in direct contact with the primer. 
If, for example, cracks are also being repaired, a suitable repair binder, 
e.g. asphalt or ROADBOND.TM. binder, a product of the assignee of this 
invention, will be dispensed into the crack and the primer then applied to 
the substrate adjacent the filled crack. The road repair membrane, or 
laminant, preferably comprises a fibrous reinforcement material which has 
been coated, or impregnated, on both sides, as by dipping, with a 
substantially non-tacky chemically-modified asphalt, the membrane also 
being provided, as by coating on one side thereof, with a layer of the 
adhesive which serves to tenaciously enhance the membrane bonding to the 
primer. 
Desirably the membrane will be sufficiently flexible to allow it to be 
formed into rolls and in order to protect the adhesive layer and prevent 
membrane adherence in the rolled form prior to the time of use, the 
adhesive layer will be covered with a suitable removable, or releaseable, 
skin as in the form of a tear-away strip. Reference herein to 
substantially non-tacky means that at room temperature the 
chemically-modified asphalt has significantly less tack than the adhesive. 
Exemplary fibrous reinforcement materials are various mats including 
chopped strand mats, continuous strand mats, swirl mats, woven and 
non-woven fabrics, e.g., woven rovings, insect screening, scrim and the 
like. Preferably the fibrous materials are glass but they may also be 
organic polymeric materials or combinations of glass and organic polymers. 
Outstanding results are obtained when the non-tacky chemically-modified 
asphalt is the reaction product of asphalt, non-depolymerized rubber and a 
polymerizable vinyl aromatic monomer; the latter may be an admixture of 
monofunctional and polyfunctional vinyl monomers. Further details may be 
found in copending applications Ser. No. 045,047 (now U.S. Pat. No. 
4,273,685) and Ser. No. 144,711 (now U.S. Pat. No. 4,332,705) both of 
which are hereby incorporated by reference. Suitably the non-tacky 
chemically-modified asphalt coating is applied to the reinforcement 
material by dipping the latter into a hot melt of the former. The coated 
membrane may then be cooled and the adhesive applied to one side. The 
releaseable skin is then applied to the adhesive layer. The adhesive may 
likewise be applied as a hot melt. One suitable releaseable skin is a 
polyethylene coated kraft paper which has a silicone overcoat which is 
available from Daubert Paper Co. as their product 1-60-EKPL-164. The 
membrane is then preferably rolled upon itself to form a roll for on site 
use in road repairs by applying it to the primer.

Having described the basic concepts of the invention, reference is now made 
to the following examples, which are provided by way of illustration, and 
not by way of limitation, of the practice of the present invention in 
formulating a primer composition and its use in promoting a secure bonding 
relationship between an adhesive coating mat and a substrate over which 
the mat is laid down. 
EXAMPLE 1 
This example illustrates the preparation of a primer composition embodying 
the concepts of this invention. 
A primer batch is formulated as follows: 
______________________________________ 
Parts by weight 
______________________________________ 
Depolymerized natural rubber 
60 
(DPR-400) 
Depolymerized natural rubber 
(XL-01) (From Hardman Chemicals) 
6 
Terpene resin (Piccolyte A-115 
229 
resin) 
______________________________________ 
The above batch is cooked at 165.degree. F. for 4 hours. Thereafter, the 
reaction product is blended with hexane to form a primer formulation of 
about 10%-12% by weight of solids, which is then applied to a road 
surface. Thereafter, glass fibers (in the form of a woven roving coated on 
both sides by dipping in a chemically-modified asphalt and then coated on 
one side with an adhesive formed by the reaction of asphalt, styrene, a 
rubbery polymer, a depolymerized rubber and a terpene resin) is laid down 
over the primed surface with the adhesive in direct contact with the 
primer. It is found that the adhesion is improved by 15-30% as compared to 
the same surface which has not been coated with a primer. In addition, 
adhesion is achieved at temperatures 10.degree. F. to 15.degree. F. lower 
than the temperatures required to secure adhesion to the same surface 
which had not been coated with a primer 
EXAMPLE 2 
This example illustrates the preparation of a primer composition of the 
invention which has been formulated to include a non-depolymerized rubber, 
namely Solprene 1205C, a butadiene-styrene rubber. 
A primer batch is formulated as follows: 
______________________________________ 
Parts by weight 
______________________________________ 
Depolymerized natural rubber 
1 
(XL-01) 
Butadiene-styrene rubber 
10 
(Solprene 1205C) 
Nevpene (9500) 20 
Naphtha (55.degree. F.) 
100 
______________________________________ 
The above formulation was made at room temperature and was allowed to stand 
for 24 hours. Mixing is used to cause the depolymerized rubber to go into 
solution. 
The resulting primer composition is then applied to a stainless steel sheet 
at a thickness of 0.006 in., and a glass-reinforced mat of treated asphalt 
applied to it. The adhesion between the mat and the stainless steel 
substrate is improved as compared to a stainless steel substrate which had 
not been coated with the primer. 
It will be understood that various modifications can be made in the details 
of procedure, formulation and use without departing from the spirit of the 
invention, especially as defined in the following claims.