Polyethylene-carbon monoxide

Random ethylene-carbon monoxide copolymers have been known for many years and have properties somewhat similar to low density polyethylene. Alternating ECO copolymers were first produced long ago by Reppe of BASF in... 

The blending of polymeric organic carbonyl compounds, e.g., ethylene/carbon monoxide copolymer, with the parent polymer, e.g., polyethylene, gives a plastic film material that degrades within 3 months. 

This industrial process remains essentially unchanged from the 1950s [25], Here, a free-radical initiator is added to the ethylene monomer at supercritical conditions (276 MPa and 200-300 °C). The polyethylene remains in the supercritical solution until the pressure is lowered to around 5 MPa, whereupon it precipitates. A range of other monomers can be copolymerized, including carbon monoxide to give polyketones, as shown in Scheme 10.19 [26],... 

Before we turn to "mechanisms" let us repeat how a catalyst works. We can reflux carboxylic acids and alcohols and nothing happens until we add traces of mineral acid that catalyse esterification. We can store ethene in cylinders for ages (until the cylinders have rusted away) without the formation of polyethylene, although the formation of the latter is exothermic by more than 80 kjoule/mol. We can heat methanol and carbon monoxide at 250 °C and 600 bar without acetic acid being formed. After we have added the catalyst the desired products are obtained at a high rate. 

Due to the chlorine content, oxygen indices are higher than those of the polyethylenes, for example 23 to 25 without fire-retardant additives, but they will act as a combustible material in the event of fire. Combustion products include hydrochloric acid and carbon monoxide, both toxic gases. 

The slurry phase, the traditional route to PP, uses Ziegler-Natta type catalyst, a hydrocarbon solvent like hexane or heptane and polymer grade propylene (99.5%). Like the stringent requirements for polyethylene plant feeds, propylene must be high purity. Water, oxygen, carbon monoxide, or carbon dioxide will poison the catalyst. The reaction takes place in the liquid phase at 150—160°C and 100—400 psi. When the isotactic polymer particles form, they remain suspended in the diluent as slurry. The atactic polymers dissolve in the diluent. 

The third side reaction is formation of a small amount of polyethylene during the growth step. The quantity of polyethylene does not represent a significant yield loss, but does present serious processing problems. The polymer deposits on reactor surfaces, inhibits heat transfer, plugs valves, and must be cleaned out periodically. A Conoco patent (9) indicates this problem can be prevented by addition of small quantities of carbon monoxide to the feed ethylene. 

A polyethylene glycol-conjugated hemoglobin derivative and carbon monoxide carrier, CO-MP4, is able to deliver CO to the circulation and reduces ischemia/ reperfusion injury in rats, providing the first evidence for this drug as a CO therapeutic agent [191, 192]. 

Although rings made of polyethylene work very well, as we have already found, polyethylene degrades extremely slowly in the environment. A small amount of carbon monoxide (CO) can be polymerized with ethylene to produce a copolymer that degrades in sunlight (undergoes photodegradation) ... 

Figure 9-2. Decrease in molar mass for low-density polyethylene and ethylene-carbon monoxide copolymer on exposure to UV radiation (Harlan 1995).

One way in which most polymers do decay is by the action of oxygen in the air and of light You will be familiar with the way that some polymers go yellow after a time and some become brittle. Coloured plastics, in particular, absorb light and oxygen-induced radical reactions follow. The polymer becomes too cross-linked and loses flexibility. One ingenious application of this natural process helps to degrade the polythene rings that hold cans of beer in packs. These are often discarded and decay quite quickly because some carbon monoxide has been incorporated into the polyethylene to make it more sensitive to photolysis. 

The acetic formic anhydride may be stored at 4° in a standard-taper round-bottomed flask fitted with a polyethylene stopper. Moisture catalyzes the decomposition of the product to acetic acid with the evolution of carbon monoxide. The material must not be stored in sealed, containers ... 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

The pyrolysis of polyethylene terephthalate produces a gas consisting mainly of carbon dioxide and carbon monoxide, due to the high oxygen content of the original plastic... 

Braun and Guillet 84) investigated copolymers of ethylene with vinyl acetate and carbon monoxide as well as modified polyethylene waxes. While the crystallinity of such polymers can no longer be derived from their density, it was found that the GC method was equally successful with copolymers or modified K)fymers. Figure 9... 

The oxygen balance is usually calculated on the unwrapped explosive and as Fordham [7] pointed out, only a part of the wrapper (waxed paper, polyethylene or other polymers) — usually a half — takes part in the chemical reaction. As pointed out in Vol. Ill (p. 424) both negative and positive balance can produce toxic gases carbon monoxide and nitrogen oxides respectively. Dubnov et al. [6] pointed out that the explosive can also react with the medium surrounding the shot-hole. 

Rossi, according to Dubnov reported that by replacing paraffin wax paper with polyethylene, the concentration of carbon monoxide was reduced from 39-42 to 12—20 l cg. after the detonation of Ammonit No. 6. 

Polymers from this class can be used for different practical purposes. For example, poly(ethylene-co-carbon monoxide) has better barrier properties for food packaging material than polyethylene, which is permeable for hydrophobic compounds used as flavors. Other copolymers can be used as plasticizers for nitrile rubber. 

A membrane separator using 1 mil thickness low-density polyethylene membrane is to be designed for concentrating hydrogen in a hydrogen-methane-carbon monoxide gas mixture. The separator performance may be approximated by a perfect mixing model. The feed flow rate is 1.0 x 10" cnf (STP)/s, and its composition and component permeabilities in polyethylene membrane are given below ... 

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