LLDPE, additives

SASOL. SASOL, South Africa, has constmcted a plant to recover 50,000 tons each of 1-pentene and 1-hexene by extractive distillation from Fischer-Tropsch hydrocarbons produced from coal-based synthesis gas. The company is marketing both products primarily as comonomers for LLDPE and HDPE (see Olefin polymers). Although there is still no developed market for 1-pentene in the mid-1990s, the 1-hexene market is well estabhshed. The Fischer-Tropsch technology produces a geometric carbon-number distribution of various odd and even, linear, branched, and alpha and internal olefins however, with additional investment, other odd and even carbon numbers can also be recovered. The Fischer-Tropsch plants were originally constmcted to produce gasoline and other hydrocarbon fuels to fill the lack of petroleum resources in South Africa. 

Reaction conditions are generally mild, but they differ from one process to another. In the newer Unipol process (Eigure 12-1) used to produce both HDPE and LLDPE, the reaction occurs in the gas phase. Ethylene and the comonomers (propene, 1-butene, etc.) are fed to the reactor containing a fluidized bed of growing polymer particles. Operation temperature and pressure are approximately 100°C and 20 atmospheres. A single-stage centrifugal compressor circulates unreacted ethylene. The circulated gas fluidizes the bed and removes some of the exothermic reaction heat. The product from the reactor is mixed with additives and then pelletized. New modifications for gas-phase processes have been reviewed by Sinclair. ... 

In addition to the two-phase TPEs, two new technologies have emerged. They are the metallocene-catalyzed polyolefin plastomers (POPs, the name given to Exxon s EXACT product line) and polyolefin elastomers (POEs, DuPont Dow Elastomer s ENGAGE), and reactor-made thermoplastic polyolefin elastomers (R-TPOs). These new types of TPEs are often called metallocene elastomers-TPEs (MEs-TPEs) [87]. The new POPs and POEs are essentially very low-molecular-weight-Unear low-density PEs (VLMW-LLDPE). These new-generation TPEs exhibit mbber-like properties and can be processed on... 

Table 3.28 Comparison of microwave and reflux extraction solvent efficiencies for additives in LLDPE...

Also, direct determination of additives by means of laser desorption in solid polymeric materials rather than in polymer extracts has been reported [266], Takayama et al. [267] have described the direct detection of additives on the surface of LLDPE/(Chimassorb 944 LD and Irgafos P-EPQ) after matrix (THAP)-coating. As shown in Scheme 7.13, direct inlet mass spectrometry is also applicable to transfer TLC-MS and TLC-MS/MS analyses without the need for prior analysis. For direct sample introduction a small amount of the selected... 

Additive-free film samples of isotactic polypropylene (iPP, 30pm Himont Profax resin) and polyethylenes (LLDPE, 120ym, linear low density DuPont Sclair resin, and UHMW-PE, 120wm, ultra high molecular weight, high density Himont LSR 5641-1B resin) were oxidized by exposure in air to y-radiation (AECL Gamma Cell 220, 1.0... 

As discussed earlier under Section 2.3, Carbonyl index, in one relatively recent comparison of the photo-oxidative and thermal (oven-aged) degradation behaviour of different polyethylenes, additive free grades of a metallocene (mPE), an HDPE and a linear low-density PE (LLDPE) were analysed by a combination of mid-IR spectroscopy, TGA and CL [13]. The mid-IR... 

Gas phase process. This most widely used process yields both HDPE and LLDPE with a wide range of copolymers. Its simplicity begets its popularity. In addition, it accommodates a broad range of interesting property combinations used in both HDPE and LLDPE markets. 

Hoang, E.M., Liauw, C.M., AUen, N.S., Fontan, E., and Lafuente, P, Effect of Metal Stearate Antacid on the Melt StahiUzation Performance of Phenolic/Phosphite Antioxidants in Metallocene LLDPE. Part 1 Melt Processing Stahility /. Vinyl Addit. Technol., 10, 3, 137 (2004)... 

LAOs are copolymerized with polyethylene to form linear low density polyethylene (LLDPE). 1-Hexene and 1-octene are especially useful for this purpose. LLDPE accounts for the largest use (31%) of LAOs, while detergent alcohols (23%), lubricants and lube oil additives (17%), and 0x0 alcohols for plasticizers (10%) are other important uses. 

Sometimes a lower density polyethylene is made with both this type of catalysis or Ziegler-Natta. Branching is controlled by the addition of small amounts of 1-alkenes added to the ethylene. 1-Hexene would give a C4 branch, 1-octene a Ce branch, etc. If enough 1-alkene is used the polymer is called linear low-density polyethylene (LLDPE). It is made by a high-density polyethylene process but branching gives a lower density. 

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