Polymer aluminium chloride

Factors affecting laboratory polymerisation of the monomer have been discussed" and these indicate that a Ziegler-Natta catalyst system of violet TiCl3 and diethyl aluminium chloride should be used to react the monomer in a hydrocarbon diluent at atmospheric pressure and at 30-60°C. One of the aims is to get a relatively coarse slurry from which may be washed foreign material such as catalyst residues, using for example methyl alcohol. For commercial materials these washed polymers are then dried and compounded with an antioxidant and if required other additives such as pigments. 

V. A. Blazhevich, D. A. Khisaeva, V. G. Umetbaev, and I. V. Legostaeva. Polymer plugging solution for oil and gas wells—contains urea-formaldehyde resin, and aluminium chloride containing waste of isopropylbenzene production as acid hardener. Patent SU 1763638-A, 1992. 

Polymerisations in n-pentane. Kennedy and Thomas, wishing to study the polymerisation of isobutene by aluminium chloride under homogeneous conditions, i.e., in a solvent in which even the highest polymers remained in solution at low temperatures, chose n-pentane [54]4. The specimen they used was stated to contain approximately 0.1 mole/1 of branched and olefinic impurities which are known to reduce the DP and therefore the DPs obtained must be (slightly) lower than those which would have been obtained in pure n-pentane. 

The limited conversion which is usually obtained when aluminium chloride in low concentrations is used to polymerise isobutene, has been attributed to the catalysts becoming embedded in the polymer which is precipitated. 

Polymerisations in alkyl chlorides. In Figure 3 of Reference 43 it was shown that the DP of the polymers at first increased with monomer concentration, and then fell off steeply to a quite low value characteristic of the polymerisation of undiluted monomer. The exact nature of the diluent ( alkyl halide ) and catalyst were not disclosed, but it is now known that the diluent was methyl chloride and the catalyst aluminium chloride. Kennedy and Thomas have investigated in some detail this interesting phenomenon [56] Experiments were carried out at -78° in a dry-box To 7.1 g of isobutene and the appropriate quantity... 

Propane was selected as solvent for the isobutene for experiments down to -145° the aluminium chloride was dissolved in ethyl chloride, for the work at lower temperatures a mixture of ethyl chloride and vinyl chloride was used. Although these catalyst solutions were made up at -78° they were yellow, and as stated above, they probably contained some hydrogen chloride and other catalytically active decomposition products. The polymerisations were carried out by running the cooled catalyst solution into the monomer solution. Polymer was formed, and came out of solution, almost immediately, and the reaction was very fast even at the lowest temperature (-185°) and lowest monomer concentration (0.6 mole/1). After the reaction was over, propanol at the reaction temperature was added to the reaction mixture to deactivate the catalyst. 

There is no necessary relation between the electrical properties of the polymer cation, its anion, and the corresponding ion-pair, and those of the ions present in the solution before the isobutene is added. In fact, since the planar tertiary carbonium ion at the growing end of the polymer chain is much smaller than any cation (except the improbable A1C12+) derivable from aluminium chloride, the dissociation constant of the carbonium ion - anion pair, whatever the anion, must be much smaller than that of the ion-pairs existing in the catalytic solutions before the addition of the monomer. 

In other words, only those aluminium atoms which are present in the initiator solution as cations at the moment when it enters the monomer solution are effective in starting polymer chains, the rest of the aluminium chloride becomes inactivated by complexing with the monomer ... 

For our idea that initiation is due to the cations present in the initiator solution, there is some very relevant evidence, and once again it has been available for many years although its import was not appreciated. This evidence is the ZAV effect [4], i.e., the antibatic correlation between the conductivity of an initiator solution (containing aluminium chloride and an oxygen compound, e.g., ethanol) and the molecular weight of the polymer resulting from its addition to an isobutene solution [19]. The now evident conclusion... 

The polymers from Experiments R8, R15 and R9 contained ca. 1 tritium atom, and therefore originally 1 aluminium-carbon bond, per molecule. For those experiments in which the polymer remained in solution, the final value of the conductivity suggested a minimum of 1 mol of ions for 1 mol of polymer. When aluminium chloride was used as initiator, the results obtained resembled closely those obtained with the bromide. 

Example 6. Type D. Category 4. Zlamal and Kazda [2g] have reported that, when isobutene was polymerised by aluminium chloride at -78 °C in a mixture of ethyl chloride and benzene, the DP of the polymers went through a minimum when the solvent contained about 5% by weight of benzene. In conformity with the ideas developed in the previous example, we interpret this effect as being due to an impurity, G, in the benzene which reacts with aluminium chloride to form two complexes, thus ... 

For the polymerisation of isobutene by aluminium chloride in ethyl chloride at -78 °C in the presence of various polar compounds, Vesely and his collaborators [16] showed that the DP of the polymers was inversely related to the conductivity of the catalyst solutions before addition of the monomer. This suggests very strongly that the propagating species is ionic [17]. 

Watanabe, M., Yamada, S-L, and Ogata, N., Ionic conductivity of polymer electrolytes containing room temperature molten salts based on pyridinium halide and aluminium chloride, Electrochim. Acta, 40,2285,1995. 

Benzene may be polymerized under the action of aluminium chloride and copper chloride into a thermostable structure which retains the chemical reactivity of benzene. Such a polymer may be sulfonated or phosphonated in suspension, and active acidic catalysts are obtained that are stable up to 350 °C and carry the functional groups only at the surface n°) ... 

Recent work on the dimerisation of 1,1-diphenylethylene by aluminium chloride produced conclusive evidence that direct initiation does not lead to the total ctmsump-tion of the catalyst. This excellent piece of research diowed that about 2.5 aluminium atoms are needed to give rise to one carbenium ion. Similar indications were reported by Kennedy and Squires for the low temperature polymerisation of isobutene by aluminium chloride. They underlined the peculiar feature of limited yields obtained in flash polymerisations with small amounts of catalyst. The low conversions could be increased by further or continuous additions of the Lewis acid. Equal catalyst increments produced equal yield increments It was also shown that introductions of small amounts of moisture or hydrogen chloride in the quiescent system did not reactivate the polymerisation. This work was carried out in pentane and different purification procedures for this solvent resulted in the same proportionality between polymer yield and catalyst concentration. Experiments were also performed in which other monomers (styrene, a-methylstyrene, cyclopentadiene) were added to the quiescent isobutene mixture. The polymerisation of these olefins was initiated but limited yields were again obtained. Althou the full implications of these observations must await more precise data, we agree with the authors interpretation that allylic cations formed in the isobutene polymerisation, while incapable of activating that monomer, are initiators for the polymerisation of the more basic monomers added to the quiescent mixture. The low temperature polymerisation of isobutene by aluminium chloride was also studied... 

Kennedy and Squires studied the effect of hydrogen chloride on the course of isobutene polymerisation catalysed by aluminium chloride. They showed that at —78 °C HCl increased the polymer yield if introduced before the catalyst, but had no effect if added to a quiescent mixture obtained by direct initiation giving a limited conversion. These observations are entirely consistent with our interpretation of the phenomenology of direct initiation HCl is a cocatalyst in the presence of free aluminium chloride, i.e. when added at the beginning of the experiment, but is ineffective if the Lewis acid is tied up in conjugation products which, as we have seen, bring the polymerisation to a halt before all the monomer is consumed (cf. Sect. IV-B). 

Volatile metal halides, usually chlorides and fluorides, also form the heart of several processes used to produce surface layers, rich in aluminium, chromium, or silicon, or combinations of these. In these processes, the workpiece to be coated is buried in a powder bed and heated to reaction temperature. The bed consists of a mixture of inert alumina filler, a master alloy powder that contains the aluminium, etc., and an activator such as ammonium chloride. Basically, at about 630°C, the activator volatilizes and the aluminium chloride vapour reacts with the master alloy to produce a volatile aluminium chloride, which then reacts with the workpiece surface to deposit aluminium. The deposited aluminium proceeds to diffuse into the surface layers of the workpiece to produce a diffusion coating. The process is driven basically by the difference in aluminium activity between the master alloy and the worlqtiece. These processes are well documented in principle, but their execution to provide reproducible and reliable results still involves considerable experience, or rule of thumb. These processes will be described in detail in Chapter 10. Finally, a chlorination treatment is used to remove tin from tin-plated steel. This uses a normally deleterious reaction to advantage and profit in the recovery of both tin and steel for recycling. Fluorination is used in the manufacture of polymers and fluorocarbon consequently, materials suitable for construction of these plants must be resistant to fluorine attack. 

In 1953, Karl Ziegler had discovered the polymerisation of ethylene at normal pressure he succeeded in polymerising ethylene to polyethylene in a 5-litre preserving jar with a mixture of titanium tetrachloride and diethyl-aluminium chloride (Fig. 3.43). At the end of the 1950s, Gunther WHke intended to prepare butadiene from acetylene and ethylene with Ziegler catalysts, but preliminary experiments showed that the selected catalysts reacted violently with butadiene, and that the product was not a polymer but cyclododecatriene. Wilke later foimd, by using Ni(0)-com-plexes (which he called naked nickel ), that the isomer ratio was clearly in favour of the zH-trans isomer. 

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