Propylene copolymerisation

It may be interesting, in connection with the ethylene/propylene copolymers mentioned above, to present here some homogeneous Ziegler-Natta catalysts formed by soluble complexes of titanium and magnesium chlorides with alkyl phosphates as catalyst precursors and alkylaluminium compounds as activators (TiCl4)x.(MgCl2)r [0=P(0Bu)3]3-A1(/-Bu)3 and Cl3TiOMgCl-[0 = P(0Bu)3]3- A1(z -Bu)3 (Al/Ti molar ratio of ca 10 1). These catalysts have been used for random ethylene/propylene copolymerisation [73],... 

Let us recall also that vanadium-based soluble Ziegier-Natta catalysts have found widespread industrial application for the manufacture of elastomeric ethylene/propylene copolymers and ethylene/propylene/diene terpolymers [319-322]. The most commonly used vanadium-based catalysts for random ethylene/propylene copolymerisation are those prepared from VCI4, VOCI3, V(Acac)3, VO(OEt)Cl2, VO(OEt)2Cl or VO(OEt)3 as precursors and AlEt3, AlEt2Cl or Al(z-Bu)2Cl as activators, with an Al/V molar ratio not exceeding 3 1 [37, 72],... 

In agreement with this finding, it has been shown that, in ethylene/propylene copolymerisation with vanadium-based catalysts, propylene insertion after an ethylene insertion is substantially non-stereospecific (both cases (a) and (b) in Figure 3.46 are possible) [1,390]. 

Table 3.5 Monomer relative reactivity ratios, r (ethylene) and r2 (propylene), for ethylene/propylene copolymerisations with various Ziegler-Natta catalysts 1...

Typical values of comonomer relative reactivity ratios in ethylene/propylene copolymerisations run with various heterogeneous and homogeneous Ziegler-Natta catalysts are listed in Table 3.5 [30, 72, 454]. 

A scheme for the alternating copolymerisation of conjugated dienes and a-olefins has been proposed in the case of isoprene/propylene copolymerisation with V-based Ziegler-Natta catalysts [209] ... 

The study of ethylene and propylene copolymerisation, on vanadium and titanium catalysts of various compositions [70], led to the conclusion that studied catalytic systems contain two or three types of AC. This conclusion has been made as a result of the analysis of the MWD curves, carbon nuclear magnetic resonance spectroscopy analysis, and copolymers composition fractionation data. The analysis of a large number of copolymer fractions, produced by their dissolution in several solvents at various temperatures, has indicated the existence of several types of AC different both in stereospecificity and in reactivity. According to the authors of [70], a combination of copolymer fractionation results with gel chromatography data indicates the presence of two or three types of AC. 

Figure 5.8 Different technological schemes for the catalytic complex formation of ethylene and propylene copolymerisation. 1 - polymeriser 2 - mixing device 3 -tubular vessel for preparing the gas-liquid mixture 4 - tubular vessel for preparing the cocatalyst solution 5 - tubular vessel for preparing the catalyst solution and 6 - tubular turbulent sprayer. I - gas-liquid mixture II - polymer solution in -recirculating gas IV - solvent V - cocatalyst and VI- catalyst...

Figure 5.9 Various schemes of tubular sprayers for the formation of homogeneous fine macromolecule growth centres during ethylene and propylene copolymerisation a - coaxial b - uniaxial and c - intersecting...

Table 5.3 Formation of active sites in turbulent mode for ethylene and propylene copolymerisation in the presence of a VOCl3-Al(C2H5)2Cl...

The preparation and introduction of catalytic complex components to the polymeriser, using a tubular turbulent prereactor, enables the synthesis of copolymers (styrene-propylene (SSP) and styrene-ethylene-propylene (SSEPT)) which demonstrate high stability and durability. According to the laboratory results, obtained from the commercial production of ethylene and propylene copolymerisation, during separation of the active site formation and initiation of isoprene polymerisation on a Ti-Al catalytic system, an increase in copolymer yield and its molecular weight, as well as a decrease in catalyst rate were observed. 

A six-sectional tubular turbulent device of optimal construction dj = 150 mm, = 75 mm, and = 500 mm) is used in the production of the ethylene propylene copolymer. It is installed at the stage of catalyst decomposition and washing, after the ethylene and propylene copolymerisation, as well as at the introduction of the stabiliser into the ethylene propylene rubber solution. This intensifies the vanadium salt washing from the polymer and guarantees the production of rubber with a content of vanadium and ash, in the end products, which is within the required limits. 

Clearly, propylene is preferentially polymerised at site 1, while at site 2 ethylene and propylene copolymerise to give an approximately random copolymer. 

AH higher a-olefins, in the presence of Ziegler-Natta catalysts, can easily copolymerise both with other a-olefins and with ethylene (51,59). In these reactions, higher a-olefins are all less reactive than ethylene and propylene (41). Their reactivities in the copolymerisation reactions depend on the sise and the branching degree of their alkyl groups (51) (see Olefin polya rs, linear low density polyethylene). 

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

By block copolymerisation so that one component of the block copolymer has a Tg well below the expected service temperature range (e.g polypropylene with small blocks of polyethylene or preferably polypropylene with small amorphous blocks of ethylene-propylene copolymer). 

One unfortunate characteristic property of polypropylene is the dominating transition point which occurs at about 0°C with the result that the polymer becomes brittle as this temperature is approached. Even at room temperature the impact strength of some grades leaves something to be desired. Products of improved strength and lower brittle points may be obtained by block copolymerisation of propylene with small amounts (4-15%) of ethylene. Such materials are widely used (known variously as polyallomers or just as propylene copolymers) and are often preferred to the homopolymer in injection moulding and bottle blowing applications. 

A stereo specific polymer produced by the copolymerisation of ethylene and propylene with Ziegler-type catalysts. 

Ethylene can be copolymerised with several monomers like propylene, 1-butene, vinyl acetate, ethyl acrylate, etc. 

Another way to recover the catalyst from the dormant site is the copolymerisation of ethene, but this is slower and less attractive than the use of hydrogen. Furthermore the use of ethylene inevitably results in the formation of propylene-ethylene copolymers with all the consequent effects on polymer properties. 

Bci dcr Copolymerisation von Athylcn und cis-Buten-2 liefem Katalysa-toren, die bei der Polymerisation von Propylen (76) keine taktischen Polymcren synthctisicren, wic Vanadiumacctylacctonat und Diathyl-aluminiumchlorid, ebenfalls keine kiistallinen Copol5Tnercn. Copol3unere von Athylen und trans-Buten-2 sind mit alien verwendeten Katalysato-ren nicht kristallin crhaltcn worden. 

Coordination polymerisation via re complexes comprises polymerisation and copolymerisation processes with transition metal-based catalysts of unsaturated hydrocarbon monomers such as olefins [11-19], vinylaromatic monomers such as styrene [13, 20, 21], conjugated dienes [22-29], cycloolefins [30-39] and alkynes [39-45]. The coordination polymerisation of olefins concerns mostly ethylene, propylene and higher a-olefins [46], although polymerisation of cumulated diolefins (allenes) [47, 48], isomerisation 2, co-polymerisation of a-olefins [49], isomerisation 1,2-polymerisation of /i-olcfins [50, 51] and cyclopolymerisation of non-conjugated a, eo-diolefins [52, 53] are also included among coordination polymerisations involving re complex formation. 

The use of coordination catalysts, especially homogeneous vanadium-based catalysts, for the copolymerisation of ethylene and propylene, with an ethylene content of 15-75 mol.-% in the feed, made it possible to produce amorphous... 

With the sole exception of the random ethylene-propylene copolymers, for industrial applications heterogeneous catalysts have been used for alkene polymerisations. Ethylene-propylene statistical copolymerisation has been carried out using homogeneous vanadium-based catalysts [28]. 

Although both Phillips and Ziegler Natta catalysts copolymerise ethylene and propylene, the latter catalysts are more widely used because they can be more readily tailored to produce a narrow distribution of compositions and molecular weight [43]. 

The syndiospecific polymerisation of propylene with soluble vanadium-based Ziegler Natta catalysts is not completely regiospecific [389 392], i.e. the monomer unit enchainment is not entirely head-to-tail. In addition to syndiotactic stereoblocks, the polymer also contains sterically irregular stereoblocks. The whole polymerisation can be thus described as a copolymerisation with four head-to-tail and tail-to-tail stages [2,379]. 

Olefin copolymerisations, especially those of ethylene with propylene and/or another a-olefin, lead to copolymers that are of great practical importance the total production volume of such olefin copolymers is comparable with that of olefin homopolymers [30]. 

Random ethylene/propylene copolymers are amorphous and represent an interesting class of synthetic elastomers. The introduction of double bonds, useful for sulphur vulcanisation in the copolymer, can be achieved by copolymerisation of ethylene and propylene with non-conjugated dienes containing only one double bond capable of insertion for instance, 1,4-hexadiene, dicy-clopentadiene and 5-ethylidene-2-norbornene (endocyclic double bond)... 

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