HDPE , production

Slurry (Suspension) Polymerization. This polymerization technology is the oldest used for HDPE production and is widely employed because of process engineering refinement and flexibHity. In a slurry process, catalyst and polymer particles are suspended in an inert solvent, ie, a light or a... 

HDPE is one of the largest commodity plastics manufactured worldwide. Dynamics of HDPE production is represented by the following data indicating both the existing and projected demand (t/yr) (114) ... 

Single-screw extruders, 23 398, 16 723 Single-site catalyst, 16 82, 26 545 in HDPE production, 20 154-155 Single-site polyethylene catalyst systems, 17 725... 

DuPont and Dow use solution polymerization technology to produce LLDPE resins. The process is based on continuous polymerization of ethylene with 1-octene in cyclohexane at about 250°C and 1200 psi. The catalyst is again Ziegler type. Residence time is of the order of several minutes. The catalyst is deactivated by treatment with an alcohol or complexing agent such as acetyl-acetone, and adsorbed on a silaceous adsorbent before stripping the solvent. The Stamicarbon (Dutch State mines) process is similar to the DuPont process, and it uses a short-residence-time solution process for HDPE production. 

Products A wide range of LLDPE and HDPE products can be produced. LLDPE is used in film, injection molding, rotational molding and extrusion applications and can be made using either butene or hexene as the comonomer. 

Products A broad range of LLDPE, MDPE and HDPE products can be produced using butene or hexene comonomer with a density range of... 

Polyethylene is an inexpensive and versatile polymer with numerous applications. Control of the molecular structure leads to low density (LDPE), linear low density (LLDPE) and high density (HDPE) products with corresponding differences in the balance of properties. Some typical properties are Glass Transition Temperature, Tg = -78° C Melting Temperature, Tm = 100° C Amorphous density at 25° C = 0.855 g/cc Crystallinity at 25° C = 1.00 g/cc Molecular weight of repeat unit = 28.05 g/mole. The basic structure of PE is as follows ... 

The Mitsui CX process is typical of a modem slurry process for HDPE production (Figure 2.37). It consists of two CSTRs (hexane is used as diluent), a centrifuge to separate the diluent from the polymer, a dryer to remove the residual diluent, and a diluent recovery system to separate the low molecular weight polymer or wax that is dissolved in the diluent. The two polymerization reactors can be operated in series or in parallel. When run in... 

Chromium Catalysts. The Phillips chromium catalyst, which perhaps accoimts for about half of the total HDPE production, is usually made by impregnating a chromium compoimd onto a porous, high surface area oxide carrier, such as silica, and then calcining it in dry air at 500-900°C (25). This latter activation step converts the chromium into a hexavalent surface chromate, or perhaps dichromate, ester. Because each Cr atom is individually attached to the surface, the support is not inert but exerts a strong influence on the polsrmerization behavior of the site. 

Traditionally, chromium catalysts have been used in single loop and gas phase reactor processes to produce type 2 HDPE products (broad molecular weight distribution), while Ziegler catalysts have been used for products with a narrow molecular weight distribution (type 1 HDPE). 

Average analysis of the PET flake and HDPE product is shown in Table 3.4. The wastewater from the process should not be much different from a large cafeteria and generally does not require pretreatment. Byproducts are reported to be wet sludge (mainly paper fibers), dirty rinse water (dishwater) and dirty wash solution (concentrated dishwater). Rutgers has installed a 5 million pound per year pilot plant to demonstrate the operation. 

Comoonem Mean PET Product Mean HDPE Product... 

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