Concentrates, Masterbatches

The MFR for the PP resin and the masterbatch colorant were measured to see if the masterbatch material met the criteria defined by Benkreira and Britton [28] and as discussed in Section 8.6. The MFRs were 20 and 116 dg/min (230 °C, 2.16 kg) for the natural PP resin and the masterbatch colorant, respectively. Obviously, the color concentrate masterbatch was not well matched for the natural PP resin according to the guidelines developed by Benkreira and Britton. That is, the carrier resin used to make the masterbatch was too low in viscosity to break up pigment... 

Figure 11.32 Black color streaks on the surface of an injection-molded electronics housing made from HIPS and a gray color concentrate masterbatch...

As discussed in Section 11.12.2, several root causes exist for black streak contamination in molded parts. These root causes include degradation of the resin in the screw channels and nonreturn valve or runner system, degraded material entering with the resin feedstock, and poorly dispersed pigments in the color masterbatch. To determine if the color concentrate masterbatch was the source of the black streaks, the color concentrate was removed from the feedstock and only natural... 

The press was started back up using the high-performance screw and natural HIPS resin with 2 % of a light gray color concentrate masterbatch. For this startup the same 2.69 kg part was produced and the barrel set point temperatures were the same as before. After steady operation was obtained (about 10 parts), the 2.69 kg part and gating were plasticated in 33.5 s at a screw speed of 52 rpm and 9.5 MPa... 

Table 3 Grafting efficiency of 10% concentrates (masterbatches) of bi- and mono-functional HAS antioxidants in PP. Reactions were conducted during reactive processing in the presence of 0.005 molar ratio of dicumyl peroxide (initiatior)...

Figure 7. Loss of impact strength (I ) of ABS during UV exposure. L, latex concentrate (masterbatch) U, unextracted P, mechanochemical concentrate. Numbers on curves are the concentrations of photoantioxidants in the concentrates.

Solid masterbatching consists of a high concentration of pigment in a carrier. The carrier can be the plastic with which it is to be compounded, a similar plastic or low molecular weight carriers. The ideal is a masterbatch which is miscible and dispersible with all types of plastic. The pigment level has conventionally been 10-20%. Recently more concentrated masterbatches with 40-60% pigment, usually in a carrier, have been made for use at an approximately 1% addition level. 

The converting or moulding process may also include the use of processing aids, e.g. lubricants and mould release agents. Masterbatching may contain lubricants, mould release and a carrier or base diluent which assist the manufacture of a concentrated masterbatch containing colourants. 

Color Concentrate (Masterbatch). Expert compounders disperse colorants at 20 to 60 percent concentration in a carrier polymer, using high shear to break down agglomerates and produce uniform dispersion of maximum coloring efficiency. This color concentrate is used by processors, simply blending it with virgin (natural color) resin ( letdown with natural ). Typical ratios of concentrate/natural are 1/20 to 1/100. This technique is low in cosL does not create inventory problems, and is most commonly used with commodity resins. 

The color concentrates (masterbatches) used for ABS are of the universal or of the ABS-based types. A typical let down ratio (concentration) for the universal type is 1 to 2% whereas a ratio of between 3 to 7% is used for the ABS based master-batch. Before using a universal masterbatch it is important to ascertain it s compatibility with ABS. Pastel shades can now be readily achieved due to the availability of polymers with a lighter (i.e. whiter) base color. Back pressure is often used with masterbatches so as to assist in the dispersion of the pigment within the polymer melt. 

As with many fillers, colorants, and additives, CB is frequently compounded with a thermoplastic to form a concentrate or masterbatch that is then let down and dispersed in a chosen polymer to the final desired concentration. Masterbatches are available from a variety of compounders including Americhem, Inc., Ampacet Corp.,... 

These are highly effective external lubricants for PVC, with positive effect on gelation and surface quality of finished products. Polar polyethylene waxes have a pronounced anti-sticking effect and high molecular types are suitable for transparent items. Other waxes improve pigment dispersion and permit production of highly concentrated masterbatches with better colour yield. 

Continuous Production of Pigment and Additive Concentrates (Masterbatch), Brief Report No.15, Werner and Pfleiderer, Stuttgart, Germany (undated). 

The synthesis of thiol-adduct antioxidants by a mechano-chemical procedure in elastomers is described. The yields of polymer-bound antioxidants so formed increase with increasing antioxidant loading and for most unsaturated polymers an optimal yield is observed at 20-30% loading. Bound antioxidant concentrates made by this procediire have been used as additives in a range of elastomers and it has been demonstrated that an adduct concentrate (masterbatch) in one polymer (e.g. EPDM) can be used in a range of other polymers without sacrificing efficiency. 

The masterbatch concentrate procedure has proved to be very important practically because it is a highly economical way of introducing bound antioxidants into polymers. Surprisingly, concentrated masterbatches of bound antioxidants are no less effective when reduced in concentration to normal antioxidant concentrations J- an are bound antioxidants made by modifying the whole of the rubber. This is illustrated in Table 4 for nitrile-butadiene rubber using typical antioxidant thiols. It can be seen that even after exhaustive extraction the bound antioxidants are more... 

Whether an additive is used in concentrated masterbatch form or in its standard form will vary depending on the requirements of particular producers. Masterbatches are routinely used for blow moulding and film blowing in commodity plastics such as polypropylene (PP), LDPE and high-density polyethylene (HOPE). 

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