Gas phase EPDM

Combining Metallocene Technology with Gas Phase EPDM, PE, Feb. 2003. 

Danbuiy, Ct., c.1998, pp.22. 12ins. 1/10/98. GRANULAR GAS-PHASE EPDM, THE ROUTE TO EFFICIENT MIXING. PAPER PRESENTED AT THE INTERNATIONAL RUBBER CONFERENCE - IRC 96, MANCHESTER, JUNE 17-21,1996 Italiaander T Union Carbide Corp. 

GRANULAR GAS-PHASE EPDM. THE ROUTE TO EFFICIENT MIXING... 

GRANULAR GAS PHASE EPDM CONTINUOUS MIXING BECOMES REALITY... 

EPR and EPDM have been made by either solution or emulsion polymerization processes. More recently a new process involving gas-phase polymerization and metallocene catalysts promises to capture large shares of these markets. These new polymers will be especially attractive in automotive apphcations and wine and cable where theh favorable pricing should be welcome. 

There are five North American manufacturers of EPDM Unhoyal Chemical, Exxon, DuPont, DSM, and Bayer. In addition. Union Carbide and Dow are manufacturing the new gas-phase polymers. A new joint agreement between Dow and DuPont will offer these two companies some competitive advantages in this market. Trade names of commercial ethylene—propylene polymers include Bayer s Epsyn, Exxon s Vistalon, DuPont s Nordel, and Unhoyal s Royalene. 

Specimens of NR ABS/(Octa -I- AO) heat-treated at 350°-400°C developed brittleness of connected pores, whereas VO ABS (Octa -1- AO -I- EPDM), similarly treated, was tougher with large elongated pores about twice the size of the non-treated specimen. Such behavior suggests an intumescent effect of EPDM, i.e. the development of a thick porous surface layer, inhibiting the diffusion of flammable products of plastic degradation towards the gas phase and heat transfer into the plactic mass. 

EPM and EPDM, generally referred to as EPDM are classically produced via Ziegler-Natta catalysis in solution or slurry processes. Over the last decade metallocene catalysis [4, 5] and gas phase technology [6] have been developed. EPDM is produced on a commercial scale in a variety of chemical compositions. Typically, the ethylene content... 

For the polymerization of ethylene and propylene large-scale gas-phase processes are well established. The implementation of gas-phase technology to the production of sticky polymers such as the ethylene/propylene-based rubbers EPM and EPDM was pioneered by UCC [519]. In a series of patents, UCC describes various approaches to overcome the inherent stickiness of rubber granules in the gas-phase polymerization. These approaches include the use of anti-agglomerants such as carbon black, silica, inorganic salts or appropriate catalyst supports and antistatic voltage etc. [520-535]. The addition of fluidization or anti-agglomeration aids is described by Zollner et al., silica is used in particular [536,537]. 

Stakem FG, Paeglis AU, Collins JD (1992) Paper Union Carbide Gas Phase EPM and EPDM Rubber, 142nd Technical Meeting of the ACS Rubber Division, Nashville, TE,... 

Alternative slurry and gas phase processes for the production of EPDM are an improvement with respect to the solvent recovery step [2]. However, in gas phase processes the possibility of incorporating large amounts of heavier monomers is hmited because of the low vapor pressure of these monomers. Furthermore, conventional slurry processes use aliphatic diluents such as iso-butane or, in some processes, supercritical propane, which are highly flammable. 

In 1979, the UNIPOL process for gas-phase production of LLDPE was introduced by the Union Carbide Corp. Since the new resins were difficult to process on the lines designed for LDPE, by 1982 several patents were issued for improvement of LLDPE processability by blending it with other polyolefins, viz., LDPE, PP, and olefinic rubbers. Ethylene copolymers, rubbers, EPDM, EVAc, maleated polypropylene, EPR, etc., have also been used (Cowan 1983 Turtle 1983 Fukui et al. 1983 Haas 1983 Hert 1983). Thus, blends LLDPE/LDPE were found miscible at low LDPE contents, then immiscible at high LDPE. Addition of HDPE as cosolvent resulted in miscible tertiary blends (Lee and Denn 2000). 

In 1979 UNIPOL process for gas-phase production of LLDPE was introduced by the UCC. Since the new resins were difficult to process on the LDPE processing lines, several patents were issued for LLDPE blends with, e.g., LDPE or PP, which had better processability In 1982 a number of patent applications for blends of LLDPE, with other polyolefins, co-polyolefins, and olefinic elastomers, for example, ethylene copolymers and thermoplastic elastomers (e.g., TPO, EPDM, EPR, EVAc, PP-MA,), have been filed... 

EPM and EPDM can be produced by solution polymerization, while suspension and slurry polymerization are viable options. EPDM can be gas-phase 1,-4 hexadiene polymerized using Ziegler-Natta catalysts. Union Carbide produces ethylene propylene rubber (EPR) using modified Unipol low-pressure gas-phase technology. 

The polymerization of olefins with coordination catalysts is performed in a large variety of polymerization processes and reactor configurations that can be classified broadly into solution, gas-phase, or slurry processes. In solution processes, both the catalyst and the polymer are soluble in the reaction medium. These processes are used to produce most of the commercial EPDM rubbers and some polyethylene resins. Solution processes are performed in autoclave, tubular, and loop reactors. In slurry and gas-phase processes, the polymer is formed around heterogeneous catalyst particles in the way described by the multigrain model. Slurry processes can be subdivided into slurry-diluent and slurry-bulk. In slurry-diluent processes, an inert diluent is used to suspend the polymer particles while gaseous (ethylene and propylene) and liquid (higher a-olefins) monomers are fed into the reactor. On the other hand, only liquid monomer is used in the slurry-bulk pro-... 

Solution processes use autoclave, tubular, or loop reactors. As compared to slurry and gas-phase polymerization, solution processes are commonly operated at a much higher temperature to keep the polymer dissolved in the reaction medium, and at much lower average residence times (5-20 min, as opposed to 1-4 h). Since polymerization conditions are more uniform in solutions reactors - there are no inter- and intraparticle heat- and mass-transfer resistances, for instance - this configuration is commonly used for the production of EPDM rubbers with soluble Ziegler-Natta vanadium-based catalysts. Composition homogeneity is a require-... 

Due to cost reduction needs of late, these blends have been substituted by reactor blends using stepwise propylene- and ethylene-propylene copolymerization techniques in the gas phase. Thus the rubber elastifier is introduced in a low-cost one-step process. Rubber contents as high as 50 percent can be provided. It was quickly seen that TPO produced by this manufacturing method gave more problems with paint adhesion than that seen in traditional PP-EPDM compounds. 

Results are presented of studies of the continuous mixing in a twin-screw extrader of granular free-flowing EPDM obtained by gas phase polymerisation. 

EPM and EPDM mbbers are produced in continuous processes. Most widely used are solution processes, in which the polymer produced is in the dissolved state in a hydrocarbon solvent (eg, hexane). These processes can be grouped into those in which the reactor is completely filled with the Hquid phase, and those in which the reactor contents consist pardy of gas and pardy of a Hquid phase. In the first case the heat of reaction, ca 2500 kJ (598 kcal)/kg EPDM, is removed by means of cooling systems, either external cooling of the reactor wall or deep-cooling of the reactor feed. In the second case the evaporation heat from unreacted monomers also removes most of the heat of reaction. In other processes using Hquid propylene as a dispersing agent, the polymer is present in the reactor as a suspension. In this case the heat of polymerisation is removed mainly by monomer evaporation. 

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