Application Summary

Recycled from waste tires, cryogenically ground rubber is a fine powder that is added as filler to asphalt, concrete, coatings, sealants, plastics and other products.

Mixing ground rubber into a viscous liquid, such as an asphalt emulsion, can sometimes pose a processing challenge if the powders require sufficient shear for complete wet-out but also tend to clump when over-sheared. One proven technique is to inject the free-flowing rubber powders into the viscous liquid as it passes through an inline Ross Solids/Liquid Injection Manifold (SLIM) Mixer. In this device, shear levels are easily fine-tuned by changing out the stator head and adjusting the rotor speed.

Ross Inline SLIM Technology

The Ross Inline Solids/Liquid Injection Manifold (SLIM) Technology is ideal for fast and efficient mixing of ground rubber powders into asphalt emulsions and other liquid vehicles. This technology is based on a rotor/stator mixer specially designed to create negative pressure (vacuum) behind the rotor. This powerful vacuum can be used as a motive force for drawing solid ingredients into the mix chamber and injecting them into a stream of incoming liquid. The resultant solid/liquid mixture is expelled centrifugally through the openings of the fixed stator before exiting the mix chamber. When processing shear-sensitive powders, the stator assembly can be removed. This "stator-less" configuration of the SLIM prevents over-shearing of sensitive materials while still delivering short mixing times. The starting liquid should ideally be less than 10,000 cP during powder injection. After all the solids are added, the product may continue to turnover and gain viscosity until dispersion is complete.

As an external mixer, the Inline SLIM can be piped to the recirculation loop of virtually any size vessel. A portable skid allows it to be rolled up to an agitated tank, operated for only the powder injection portion of the overall cycle, then rolled to another vessel to perform a similar function. Powders are typically pre-weighed and loaded into a hopper right above the mix chamber or drawn directly from a container with the use of a hose & wand attachment.

Batch-style configurations of the SLIM are also available. For instance, Ross Multi-Shaft Mixers with SLIM are well-proven for highly-filled applications with a peak viscosity of several hundred thousand centipoise. Testing is recommended to confirm the best mixing strategy for a particular formulation or raw material.

The Ross SLIM is proven technology for fast and efficient dispersion of different types of solids including:

• Alginates
• Alumina
• Bentonite Clay
• Boric Acid
• Calcium Carbonate
• Carbomers
• Carbon Black
• Carrageenan
• Citric Acid
• Dye Powders
• Guar

• Gum Arabic
• Hydroxyethyl Cellulose
• Magnesium Hydroxide
• Milk
• Pectin
• Starch
• Talc
• Titanium dioxide
• Whey
• Xanthan Gum

Processing advantages of the SLIM Technology

• Simple and straightforward operation. Just turn on the mixer and start inducting powders. No eductors or vacuum pumps to deal with.
• Easier material handling. The inline SLIM mixer is usually installed at floor level so operators no longer have to climb up mezzanines carrying heavy bags of powder. Solids can also be delivered via automatic feeding devices.
• Cleaner and safer mixing. A "hose & wand" attachment is used for dipping into bulk bags or containers to conveniently induct lightweight powders without creating a dusty environment.
• Increased yield and higher quality dispersions. By preventing the formation agglomerates and eliminating floating powders, the SLIM maximizes both yield and functionality of solid raw materials.
• Shorter cycle times. SLIM users report significant reductions in their overall mixing time, often by as much as 80% or more.
• Flexibility. The portable inline SLIM easily serves multiple process lines.