Abstract:
Cationic chemically modified asphalts having utility for road construction, repair and maintenance as well as coating for various substrates, including cementitious substrates, glass and metal are provided. These asphalts are the product produced by reacting an acrylamide, asphalt, a vinyl aromatic monomer and a rubbery polymer.

Description:
CROSS-REFERENCES 
     This case is related to U.S. Ser. No. 329,899 filed concurrently herewith. 
     TECHNICAL FIELD 
     The present invention relates to asphalt compositions, and more particularly it relates to chemically modified asphalt compositions. Even yet more particularly, the present invention relates to acrylamide modified asphalts. 
     BACKGROUND, SUMMARY AND INDUSTRIAL EXPLOITATION 
     Asphalt has been employed for numerous and wide variety of applications for many years. One of the problems encountered with asphalt is that its adhesion to various substrates and especially to aggregate needs to be improved. Such aggregate is represented, for example, by gravel, crushed rock, slag, sand and crushed limestone. Additionally, the adhesion of asphalt needs to be improved with respect to other material such as, for example, cementitious materials, metals, glass and the like. 
     An improved chemical composition is provided in accordance with this invention, which composition is the product produced by reacting an acrylamide with asphalt, and a vinyl aromatic monomer and a rubbery polymer. 
     Some of the desirable properties of the present compositions include improved coatability of negatively charged surfaces, improved adhesion, less stripping, improved emulsifiability, improved flexibility, particularly at low temperatures, improved strength, reduced high temperature flow, increase durability, better compatibility with polymers. 
     These compositions will find utility for a wide variety of purposes. They, for example, will find application in the highway and bridge construction, repair and maintenance areas as, for example, crack and pothole fillers, joint sealers, and water resistant membranes, as well as cut-backs with the compositions being used alone or as blends with conventional asphalts. These compositions can be formed into emulsions with conventional asphalt emulsifiers to form a slow set emulsion, having utility for slurry seal applications, or as a cold overlay. Preferably non-ionic surfactants are used as emulsifiers. The compositions may also be employed as corrosion resistant and/or water resistant coatings for metals and as coatings and/or impregnants for glass, especially glass fibers. Such coated or impregnated glass fibers will show outstanding compatibility with conventional asphalt and consequently will serve as outstanding reinforcements for such asphalts. 
     DESCRIPTION 
     The compositions of the present invention are obtained by heating at an elevated temperature for several hours. Preferably, the reacting is done by heating at a temperature of at least about 120° C. for about 10 hours, and most desirably, at a temperature of about 160° C. to about 180° C. for about 20 hours. 
     The acylamides employed in the present invention may desirably be secondary amides or tertiary amides. Preferably, the acrylamide will be a compound of the formula 
     
         (R.sub.1)(R.sub.2)C═C(R.sub.3)--C(O)N(R.sub.4)(R.sub.5) 
    
     wherein R 1 , R 2  and R 3  are independently selected from hydrogen or an alkyl containing 1 to 3 carbon atoms; R 4  and R5 are independently selected from hydrogen, an alkyl containing 1 to 3 carbon atoms, or preferably a radical of the formula 
     
         --R.sub.6 --N(R.sub.7)(R.sub.8) 
    
     wherein R 7  and R 8  are independently selected from hydrogen or an alkyl having 1 to 3 carbon atoms, and R 6  is an alkylene group containing 1 to 5 carbon atoms. The preferred acrylamide is dimethylaminopropylmethacrylamide, that is a compound of the formula 
     
         CH.sub.2 ═C(CH.sub.3)C(O)N(H)(CH.sub.2).sub.3 N(CH.sub.3).sub.2 
    
     The above-type acrylamides, as will be apparent, contain a double bond. It will be found that the presence of this double bond provides for the ability to chemically incorporate the acrylamide into the composition. Additionally, the amino groups present in the acrylamides provide for highly desirable polarity which serves to greatly enhance the adhesive bonding of the present compositions to various substrates, including, for example, aggregates commonly employed in road repair and maintenance, as well as cementitious and other substrates. Representative acrylamides include 
     N,N-dimethylaminopropylmethacrylamide, N,N-dimethylaminoisopropylmethacrylamide, N,N-dimethylaminoethylmethacrylamide, N-methylaminopropylmethacrylamide, N-methylaminoisopropylmethacrylamide, N-methylaminoethylmethacrylamide, aminopropylmethacrylamide, aminoisopropylmethacrylamide, aminoethylmethacrylamide, N,N-diethylaminopropylmethacrylamide, N,N-diethylaminoisopropylmethacrylamide, N,N-diethylaminoethylmethacrylamide, N-ethylaminopropylmethacrylamide, N-ethylaminoisopropylmethacrylamide, N-ethylaminoethylmethacrylamide, N-ethyl,N-methylaminopropylmethacrylamide, N-ethyl,N-methylaminoisopropylmethacrylamide, N-ethyl,N-methylaminoethylmethacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminoisopropylacrylamide, N,N-dimethylaminoethylacrylamide, N-methylaminopropylacrylamide, N-methylaminoisopropylacrylamide, N-methylaminoethylacrylamide, aminopropylacrylamide, aminoisopropylacrylamide, aminoethylacrylamide, N,N-diethylaminopropylacrylamide, N,N-diethylaminoisopropylacrylamide, N,N-diethylaminoethylacrylamide, N-ethylaminopropylacrylamide, N-ethylaminoisopropylacrylamide, N-ethylaminoethylacrylamide, N-ethyl,N-methylaminopropylacrylamide, N-ethyl,N-methylaminoisopropylacrylamide, N-ethyl,N-methylaminoethylacrylamide. 
     Asphalt materials which are suitable for these purposes preferably include those which are typically used for road paving, repair and maintenance purposes. Thus, asphalt includes natural asphalt, petroleum asphalt and petroleum tar. The natural asphalts include, for example, asphaltite, such as Gilsonite, grahamite and glancepitch, lake asphalt, such as Trinidad asphalt, and rock asphalt. The petroleum asphalt that may be used includes straight asphalt obtained by distillation of a crude oil, blown asphalt, produced by blowing an oxygen-containing gas into straight asphalt, and solvent extracted asphalt. The petroleum tar that may be used includes coal tar and oil gas tar. Tar pitch is equally suitable. Additionally, the asphalts can be those that have been blown with steam, ammonia, or amines of the type set forth in U.S. Pat. No. 4,166,752. Preferably, the asphalt which will be employed is an asphalt cement of the type typically used for road paving, repair and maintenance purposes, such as for example, the AC-5, AC-10, AC-20 grades. Such asphalts typically have penetrations ranging between about 20 to about 200. 
     As the polymerizable vinyl monomer, use is preferably made of a monofunctional vinyl aromatic monomer having a general formula: ##STR1## wherein R 1  is an aromatic group containing 6 to 12 carbon atoms, including a phenyl group, a substituted phenyl group wherein the substituent is any one of an amino group, a cyano group, a halogen group, a C 1  to C 3  alkoxy group, a C 1  to C 3  alkyl group, a hydroxy group, a nitro group, etc. R 2  is preferably hydrogen or lower alkyl e.g., a C 1  to C 5  alkyl and R 3  is hydrogen, lower alkyl or one of the following groups: ##STR2## wherein X is halogen, and preferably chlorine or bromine. Styrene is preferred. In conjunction with the vinyl aromatic monomer as described above, a polyfunctional vinyl aromatic monomer containing 6 to 12 carbon atoms in the aromatic ring and two or more polymerizable vinyl groups chemically bonded to the aromatic ring can optionally be employed. Preferred polyfunctional monomers are those having the general formula: ##STR3## wherein R 4  is a divalent aromatic group containing 6 to 12 carbon atoms, and preferably a phenylene group; and, R 5  and R 6  have the same meaning as is described above with respect to R 2  and R 3 , respectively for the monofunctional vinyl aromatic monomer. Illustrative of a suitable polyfunctional vinyl aromatic monomer is divinyl benzene. When use is made of a polyfunctional vinyl aromatic monomer in combination with a monofunctional vinyl aromatic monomer such as styrene, generally the monofunctional vinyl aromatic is present in a weight ratio of about 1:1 to 40:1 based on the weight of the polyfunctional vinyl aromatic monomer. 
     As the rubbery polymer, use can be made of a number of vulcanizable elastomeric materials well known to those skilled in the art. Included are natural rubbers as well as synthetic rubbers. Suitable are synthetic rubbers which are homopolymers of a conjugated diene (e.g., butadiene, isoprene, chloroprene, etc.) as well as various polymers which are substituted with a functional group containing a labile hydrogen atom. For example, various hydroxy, amino and like substituted homopolymers of conjugated dienes may likewise be used in the practice of this invention. Substituted butadienes are commercially available from, for example, Atlantic-Richfield under the trademark &#34;Poly B-D&#34;, a series of hydroxy-terminated butadiene polymers; for example, use can be made of hydroxy-terminated butadiene homopolymers like Poly B-D R-15M which has a hydroxy number of 42 or Poly B-D R-45M. 
     Preferably, the rubber polymer is an elastomeric material formed by copolymerization of one or more of the conjugated dienes described above with one or more ethylenic monomers such as styrene as well as hydroxy, amino and mercapto-substituted derivatives thereof, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, etc. Included are butadiene-styrene rubbers, butadiene-acrylonitrile rubbers, etc. Hydroxy-terminated copolymers are likewise useful in the practice of this invention, including the hydroxy-terminated butadiene-styrene copolymer designated &#34;Poly B-D CS-15&#34; and hydroxy-terminated butadiene-acrylonitrile copolymers like Poly B-D CN-15 having a hydroxyl number of 39. Preferred are butadiene-styrene rubbers like SOLPRENE 1205C available from Phillips Petroleum. 
     The amount of the various ingredients may vary over a wide range. Preferably, however, the acrylamide will be employed in an amount of about 0.5 to about 15% based on the weight of asphalt, the vinyl aromatic will be used in an amount of about 0.5 to about 35% based on the weight of the asphalt, and the rubbery polymer will be employed in an amount of about 0.5 to about 30% based on the amount by weight of asphalt. 
     While the above describes the invention with sufficient particularlity to enable those skilled in the art to make and use same, nonetheless further examplification follows. 
    
    
     EXAMPLE 
     Using a charge of about 67.5% of AC-20 asphalt, 5% by weight of dimethylaminopropylmethacrylamide, about 15% by weight of styrene, and about 12.5% by weight of Solprene 1205C rubber, a composition is produced as follows. Into a reactor equipped with an agitator and a reflux condenser, the asphalt is charged and heated to approximately 110° C. at which time styrene is charged into the reactor. The reactor is then heated to a temperature of about 150° C. during which time the acrylamide and the rubber is charged into the reactor. The ingredients are then heated at a temperature of about 150° C. with agitation and under reflux for about 24 hours. This product when cooled is suitable for any of the varied utilities previously set forth. 
     While the above describes the present invention, it will, of course, be apparent that modifications are possible which pursuant to the patent statutes and laws do not depart from the spirit and scope thereof.