Stock blender

The application of two roll mills in the downstream of such mixing lines is preferred, especially if the two roll mills are equipped with stock blenders (Figure 35.14). After discharging, the rubber batch will be sheeted on the two roll mill. By putting the sheet through the stock blender, the free surface from which the ethanol and moismre can be evaporated is rather big allowing the chemical reaction to proceed even at somewhat lower temperatures. A smdy by Zuuring et al. has shown... 

FIGURE 35.14 Two-roll mills with stock blender. 

The final quality and reproducibility of rubber compounds mixed from scratch on a two-roll mill, or finalisation of compound batches mixed in an internal mixer, depend to a large degree on the skill of the mill operative. In order to overcome to some extent the reliance on operative skill and to ensure reproducible mix quality many mills are now fitted with stock blender units. These consist of a driven twin roller system, of similar overall length to the mill rolls, fitted above the mill frame. 

To produce a homogeneous mixture, a so-called stock blender can be used to remove the mixture sheet from the roller continuously, push it together and lay it back on the roller gap with an oscillating motion. 

With a two-mill set-up, the first mill will roll out the batch and quickly reduce the temperature. It is usual to have an operator on this mill to do several cuts to allow the stock to pass through the nip and then send the stock on a conveyor to the second mill. This mill can be fitted with a stock blender and a variable speed drive so that the stock can be continuously fed into the rubber strip cooler at a constant speed. For example with a 270-litre internal mixer on a 3-min mixing cycle, the speed of a 800 mm x 10 mm strip would be 9m/min. This continuous lower speed allows for better cooling and drying and avoids too many splices in the strip between batches. 

Sol Preparation. Microcrystalline cellulose (Avicel PH 105) was supplied by the FMC Corporation, Philadelphia, PA., as a white powder. Twenty grams of Avicel PH 105 were mixed with 180 ml of water in a Waring blender for 5 minutes. The thick slurry was then transferred to a Lt. volumetric flask and gradually diluted to It. under constant stirring. The diluted suspension was left undisturbed for 3 days. The supernatant with a volume of about 650 ml was removed. This constituted the microcrystalline cellulose (MCC) stock sol. The solids concentration of the sols were determined by oven dry weighing and was about (1.2g/l). The unadjusted pH was 5.6. All the salts, hydrochloric acid and sodium hydroxide used were certified A.C.S. grade from Fisher Scientific. 

Preparation Heat the pumpkin seed oil in a saucepan. Add the onion and carrots and cook over moderate heat until it softens. Stir in the pumpkin pieces and cook until the pumpkin is soft. Process the mixture in a blender and pour it to the pan. Stir in the vegetable stock and cream and season with the essential oils, salt, and sherry. Ladle into warm soup bowls and garnish each with some fresh coriander leaves. 

Refiners produce base stocks or base oils and lube oil blenders produce finished oils or formulated products. See the American Petroleiun Institute s API-1509. 

To follow mycelial growth (increase in dry weight), C. versicolor was grown at 25°C within 250 ml defined medium. Stock cultures which were employed as inocula contained colonies approximately 30 mm in diameter. The inocula were homogenized for 15 sec. in 25 ml sterile, distilled H2O contained within an Eberbach sterile blender cup (Ann Arbor, MI). Each flask was inoculated with 1 ml of the homogenate and then incubated at 27-29°C. The cells were harvested by vacuum filtration and oven-dried to constant mycelial weight which was recorded as mg oven-dried weight. 

---