Moore & Munger
Asphalt Modifiers

Sasobit is excellent for high temperature stiffness in both pavement and roofing applications. Also, Sasobit makes it possible to upgrade softer grades of asphalt to harder grades whilst at the same time working to overcome deformation and "bleeding" at high performance temperatures. Sasobit dissolves within minutes in asphalt at temperatures above 248° F (120° C) and will not separate out on storage. The dramatic reduction in viscosity at working temperatures makes the asphalt easier to process, provides the option of reducing working/mixing temperatures and thereby reducing fume emissions, saving energy and reducing production cycle times.

A more recent successful application of Sasobit (updated June 10, 2002) is as a milling aid and anti-block agent in the milling of "sticky" polymers such as SBR, SB, etc. for use as asphalt modifiers. Such polymers are difficult to mill, store and transport because of the problems of re-agglomeration. It was found that when Sasobit is melted at 115°C or higher (but below flash point of 290°C ) and sprayed over the freshly shredded polymer and cooled (eg. over a cooling belt or just by ambient mixing) the polymer becomes friable and hard enough to be milled without difficulty and the milled particles stay separate as a free flowing powder. This new application opens the prospects of new formulations and applications of Sasobit in asphalt modification since the problems of processibility, formulation and transportation without blocking are all solved.

Another anti-blocking technique is the use of finely powdered Sasobit directly at the polymer vale shredding/milling stage as an agent to keep the granules apart and free flowing during packaging, storage, transportation and final use.

Sasoflex is a novel Sasol Wax International AG development comprising Sasobit plus Polymer plus a cross-linking agent. In addition to the benefits of Sasobit outlined above in improving high temperature stiffness (DSR), the Polymer contributes to elasticity at low temperatures in meeting the desired flexibility (BBR). The proprietary cross-linking agent (Sasolink) establishes a Polymer network system thereby working more effectively and providing opportunity for reduced Polymer loading in meeting target PG specifications. The Polymer selected may be SBS, SBR, Crumbed Rubber, Polyethylene, etc. This menu driven option provided by Sasoflex provides the Customer with freedom to select the best technical solution that will also be most cost effective. For example, the ratio of Sasobit to any selected Polymer can be varied to suit a particular asphalt type and target specification.

• More about Sasoflex

• More about Sasolink

Some polymers such as SB and SBR whilst most useful in enhancing the performance properties of asphalt, are difficult to package and transport to the final point of usage in a form such that they can be handled with convenience and ease. The major difficulty is that even if the bales of material are shredded or granulated, the particles readily re-agglomerate and often arrive at the Customer as a solid mass in the package making it impossible to work with.

Inorganic anti-block agents such as colloidal silica and talcum powder suffer the disadvantages that they separate out of the modified asphalt on storage in addition to interfering with the test properties during Performance Grading. We have developed a new system comprising the following:

(a) A powder form anti-blocking agent
(b) One that is completely soluble in asphalt such that separation stability in the modified asphalt is absolutely no problem whatsoever.
(c) That contributes towards enhancing the high temperature performance of the asphalt.
(d) Which is easy to incorporate into the shredding/milling stage of the polymer and which will enhance production throughput rates.

Depending on the polymer type (i.e. extent of "stickiness" and re-agglomeration) the level used can be varied to give good anti-block properties and typically the level used is 5% to 10% by mass on polymer.