MASTERBATCH

The ultimate purpose of mixing rubber is to disperse filler into the rubber matrix. With carbon black the dispersion process may be stated as, 

The question is whether or not the primary particles can be directly mixed into the rubber. 

The size of latex particles of the emulsion-polymerised rubber is less than 100 nm. This size corresponds to the domain size of rubber after the mixing is completed. It follows that if the primary particles of carbon black are added to rubber latex, satisfactory mixing may be achieved [1]. This is easier said than done. 

The main requirement is to keep the same kind of particles, i.e., carbon black - carbon black and rubber - rubber separate and for the different kinds of particles, i.e., carbon black - rubber to attract each other. For this purpose the carbon black particles may be given an electrostatic charge and the rubber particles given the opposite charge. The charging process may he done simultaneously with atomising (mist formation) particles. 

A similar process can be developed with silica fillers. The solution-polymerised rubber may be also atomised. 

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Black masterbatch Black molybdenum Black pepper... 

Red Phosphorus. This aHotropic form of phosphoms is relatively nontoxic and, unlike white phosphoms, is not spontaneously flammable. Red phosphoms is, however, easily ignited. It is a polymeric form of phosphoms having thermal stabiUty up to ca 450°C. In finely divided form it has been found to be a powerful flame-retardant additive (26,45—47). In Europe, it has found commercial use ia molded nylon electrical parts ia a coated and stabilized form. Handling hazards and color have deterred broad usage. The development of a series of masterbatches by Albright Wilson should facihtate further use. 

Masterbatch = butyl 218-100, GPE black-70, paraffinic oil-25, 2inc oxide-5, and promoter-1. 

Black masterbatch can be made with or without oil-extended SBR. Commercially there are available, worldwide, 11 numbered ESBR cold black masterbatches and 15 ESBR cold oil-black masterbatches (27). These types range in black type and content as well as oil type and amount. Of course, not every listed product is available from every supplier. 

Masterbatches with Carbon Black. Two producers (Zeon Chemicals and Copolymer) offer nitrile mbber—carbon black masterbatches. These grades are prepared by mixing the carbon black with the mbber latex prior to the coagulation and drying process. 

In order to test this concept a series of compounds was prepared in a 5 L Shaw Intermix (rubber internal mixer, Mark IV, Kl) with EPDM (Keltan 720 ex-DSM elastomers an amorphous EPDM containing 4.5 wt% of dicyclopentadiene and having a Mooney viscosity ML(1 +4) 125°C of 64 MU 100 phr), N550 carbon black (50 phr), diisododecyl phthalate (10 phr), stearic acid (2 phr), and l,3-bis(tert-butylperoxy-isopropyl)benzene (Perkadox 14/40 MB ex Akzo Nobel 40% active material 6 or 10 phr). A polar co-agent (15 phr) was admixed to the masterbatch on an open mill and compounds were cured for 20 min at 180°C in a rheometer (MDR2000, Alpha Technologies). The maximum torque difference obtained in the rheometer experiments was used as a measure of... 

Two Pass Mixing—Rotor Configurations and Antidegradant in Masterbatch... 492... 

An enormous amount of work has been reported on the issue of carbon black dispersion improvement. One of the approaches has been to produce carbon black-polymer masterbatches by mixing... 

The concept of the internal mixer is well accepted in the rubber industry, especially for the production of masterbatch compounds. Within a variety of materials the deformation of rubber compounds is relatively difficult due to the very high viscosity. Mixing devices have to be strongly powered and have to be designed in a very robust way in order to withstand the very high forces and momentum acting on the device. The most important benefits of an internal mixer are... 

FIGURE 35.7 Masterbatch mixing procedure (straight mixing). 

FIGURE 35.8 Typical fingerprint of a straight masterbatch mixing process. 

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