Narrow polydispersity resins

More recent process research aimed at anionic PS is that of BASF AG. Unlike the Dow Process, the BASF process utilizes continuous linear-flow reactors (LFR) with no back-mixing to make narrow polydispersity resins. This process consists of a series alternating reactors and heat exchangers (Fig. 22). Inside the reactors, the polymerization exotherm carries the temperature from 30°C at the inlet to 90°C at the outlet. The heat exchangers then take the temperature back down to 30°C. This process, which requires no solvent, results in the formation of narrow polydispersity PS. 

We have demonstrated a new class of effective, recoverable thermormorphic CCT catalysts capable of producing colorless methacrylate oligomers with narrow polydispersity and low molecular weight. For controlled radical polymerization of simple alkyl methacrylates, the use of multiple polyethylene tails of moderate molecular weight (700 Da) gave the best balance of color control and catalyst activity. Porphyrin-derived thermomorphic catalysts met the criteria of easy separation from product resin and low catalyst loss per batch, but were too expensive for commercial implementation. However, the polyethylene-supported cobalt phthalocyanine complex is more economically viable due to its greater ease of synthesis. 

Polymer resins with different loadings and cross-linking were investigated. Lower loadings and cross-linking gave better yields and narrower polydispersities (Table 4.5). Examination of the dry solid support by polar-... 

Angot, S., Ayres, N., Bon, S.A.F., and Haddleton, D.M. 2001. Living radical polymerization immobilized on Wang resins Synthesis and harvest of narrow polydispersity poly(methacrylate)s. Macromolecules 34 768-74. 

The shear viscosity shown in Fig. 3.30 is for a polymer with MJM = 1.5, and it is for the same weight average molecular weight and temperature as in Fig. 3.29. At a temperature of 543 K, the resin shown in Fig. 3.30 has the Newtonian to power law transition beginning at about 10 1/s. By decreasing the polydispersity the transition has moved almost two orders of magnitude higher. The narrow distribu-... 

Commodity high pressure PE-LD grades have a broad polydispersity and they contain small amounts of LCB, which results in excellent melt flow properties. Due to the broad polydispersity (PD), the mechanical properties are inferior, even compared with conventional Ziegler-Natta resins. However, narrow PD metallocene resins have poor processing properties. Recent advances in catalyst technology, have resulted in metallocene polyethenes that contain small amounts of LCB to ease the processability. 

The polydispersity of the resin is fairly high, although it has been shown that a narrow molecular weight distribution improves lithographic performance. ... 

Most LLDPE resins manufactured have a relatively narrow molecular weight distribution as indicated by Melt Flow Ratio values (MFR = FI/MI) of 16-30 or polydispersity values of 2-4. Films produced from this type of polyethylene have higher dart impact and tear properties as shown in the Table 6.5. However, LLDPE resin with a MWD broader than LDPE is used in geomembrane applications such as landfill covers and caps and other heavy-gauge film applications. 

Metallocene catalysts are used to produce a distinctive range of resins that are less polydisperse than those available from traditional catalyst systems. Each catalyst contains only one type of active site, all of them polymerizing the available monomers in an identical fashion. The net result is a uniform polymeric product that has a narrow molecular weight distribution and homogeneous comonomer incorporation. 

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