Method for preparation of stable bitumen polymer compositions

A method for preparing asphalt and polymer compositions comprising:

• heating the asphalt in a stirred tank to a temperature sufficient to allow stirring of the asphalt in the tank, wherein said temperature is at least 330.degree. F.;
• adding an elastomeric polymer to the tank in an amount not greater than twelve percent by weight of the total composition to form a mixture;
• adding a crosslinking composition to the composition;
• continue stirring and maintain the temperature in the tank for at least forty-five minutes, wherein the crosslinking composition consists essentially of at least 0.08 percent by weight based on the asphalt of 2-mercaptobenzothiazole, from 0.08 to 0.3 percent by weight based on the asphalt of elemental sulfur, and at least 0.04 percent by weight based on the asphalt of zinc oxide.

A method for preparing asphalt and polymer compositions comprising:

• heating the asphalt in a stirred tank to a temperature sufficient to allow stirring of the asphalt in the tank, wherein said temperature is at least 330.degree. F.;
• adding an elastomeric polymer to the tank in an amount not greater than twelve percent by weight of the total composition to form a mixture;
• adding a crosslinking composition to the composition;
• continue stirring and maintain the temperature in the tank for at least forty-five minutes, wherein the crosslinking composition consists essentially of at least 0.02 percent by weight based on the asphalt of 2-mercaptobenzothiazole, at least 0.1 percent by weight based on the asphalt of mixed polythiomorpholine and at least 0.03 percent by weight based on the asphalt of zinc oxide.

A method for preparing asphalt and polymer compositions comprising:

• heating the asphalt in a stirred tank to a temperature sufficient to allow stirring of the asphalt in the tank, wherein said temperature is at least 330.degree. F.;
• adding an elastomeric polymer to the tank in an amount not greater than ten percent by weight of the total composition to form a mixture;
• adding a crosslinking composition to the composition;
• continue stirring and maintain the temperature in the tank for at least forty-five minutes;
• wherein the asphalt is heated to a temperature not greater than 380.degree. F. prior to the addition of the crosslinking composition;
• wherein the elastomeric polymer is a styrene-butadiene polymer;
• wherein the crosslinking composition consists essentially of at least 0.08 percent by weight based on the asphalt of 2-mercaptobenzothiazole, from 0.08 to 0.3 percent by weight based on the asphalt of elemental sulfur and at least 0.04 percent by weight based on the asphalt of zinc oxide;
• wherein the ratio of 2-mercaptobenzothiazole to zinc oxide to elemental sulfur is 2.0/1.0/2.0 and;
• with the proviso that 2-mercaptobenzothiazole is present in amounts from 2 percent to 5 percent by weight of elastomeric polymer.