Solution-polymerised

When benzaldehyde is treated with a concentrated caustic alkali solution, polymerisation occurs with the formation of benzyl benzoate, which then... 

Polyquinoxalines are prepared by the solution polymerisation of aromatic bis((9-diamines) such as 3,3, 4,4 -tetraminobiphenyl and aromatic bis(glyoxal hydrates) such as 4,4 -oxybis(phenylglyoxalhydrate) ... 

The technologies suitable for LLDPE manufacture include gas-phase fluidised-bed polymerisation, polymerisation in solution, polymerisation in a polymer melt under high ethylene pressure, and slurry polymerisation. Most catalysts are fine-tuned for each particular process. 

Favorable rates and yields of DAP prepolymer are obtained by solution polymerisation in CCl —bensene mixtures (68). Bulk polymerisation at 80°C with bensoyl peroxide is advanced to a certain viscosity before addition of ethanol to precipitate the prepolymer that is then dried (69). 

The low vinyl acetate ethylene—vinyl acetate copolymers, ie, those containing 10—40 wt % vinyl acetate, are made by processes similar to those used to make low density polyethylene for which pressures are usually > 103 MPa (15,000 psi). A medium, ie, 45 wt % vinyl acetate copolymer with mbber-like properties is made by solution polymerisation in /-butyl alcohol at 34.5 MPa (5000 psi). The 70—95 wt % vinyl acetate emulsion copolymers are made in emulsion processes under ethylene pressures of 2.07—10.4 MPa (300—1500 psi). 

This equation indicates that the reaction rate is proportional to the square root of the initiator concentration and to the monomer concentration. It is found that the relationship with initiator concentration is commonly borne out in practice (see Figure 2.18) but that deviations may occur with respect to monomer concentration. This may in some cases be attributed to the dependency of / on monomer concentration, particularly at low efficiencies, and to the effects of certain solvents in solution polymerisations. 

In the suspension process, which was the first method to be commercially developed, propylene is charged into the polymerisation vessel under pressure whilst the catalyst solution and the reaction diluent (usually naphtha) are metered in separately. In batch processes reaction is carried out at temperatures of about 60°C for approximately 1-4 hours. In a typical process an 80-85% conversion to polymer is obtained. Since the reaction is carried out well below the polymer melting point the process involves a form of suspension rather than solution polymerisation. The polymer molecular weight can be controlled in a variety of... 

By polymerising styrene in solution many problems associated with heat transfer and the physical movement of viscous masses are reduced, these advantages being offset by problems of solvent recovery and the possibility of chain transfer reactions. In 1955 Distrene Ltd started a plant at Barry in South Wales for the production of styrene by such a solution polymerisation process and some details have been made available. The essential details of this process are indicated by Figure 16.7. 

Figure 16.7. Flow diagram for commerical solution polymerisation of styrene...

This technique is very similar to solution polymerisation except that the monomer is suspended rather than dissolved in an inert liquid, often water. Heat transfer and reduction in viscosity are comparable with those of solution... 

For both types of polymerisation mechanisms, different polymerisation processes can be used ranging from simple bulk and solution polymerisation processes to more sophisticated ones such as suspension, emulsion, interfacial, plasma,... polymerisation processes. 

There are three main techniques of polymerisation bulk, solution and emulsion. In bulk or mass polymerisation, the catalyst is added directly to the monomer and heat may be applied to start the reaction. In solution polymerisation, the monomer is dissolved in an organic solvent. In emulsion polymerisation, the monomer or monomers are stirred up with water and an emulsifying agent to form a stable emulsion. Control of the reaction is obviously much easier with either solution or emulsion polymerisation than with bulk polymerisation. 

Polybutadiene is produced by solution polymerisation, and one important feature governing the performance of the resultant polymer is the cis 1,4, and 1, 2 vinyl contents. High cis 1,4 polymers (>90%) have a Tg around -90 °C, and hence exhibit excellent low temperature flexibility only exceeded by the phenyl silicones. They also exhibit excellent resilience and abrasion resistance unfortunately the high resilience gives poor wet grip in tyre treads, and hence this rubber finds limited use as the sole base for such compounds. 

When the USA and Germany were cut off from the supplies of natural rubber during the Second World War both countries sought to produce a synthetic alternative SBR was the result, and at one stage it was the most commonly used synthetic rubber. It can be produced by both emulsion and solution polymerisation techniques, with the emulsion grades being the most widely used. Emulsion polymerisation yields a random copolymer, but the temperature of the polymerisation reaction also controls the resultant properties obtained. Cold polymerisation yields polymers with superior properties to the hot polymerised types. 

Solution polymerisation can yield random, di-block, tri-block or multi-block copolymers. It is important to note that the tri-block, or multi-block copolymers, belong to that class of material termed thermoplastic elastomers and it is only the random copolymer types that are considered here. 

Both random emulsion and solution polymerised SBR contain about 23% styrene. 

In solution polymerisation, the reaction is carried out in presence of a solvent. The monomer is dissolved in a suitable inert solvent along with the chain transfer agent. A large number of initiators can be used in this process. The free radical initiator is also dissolved in the solvent. The ionic and coordination catalysts can either be dissolved or suspended in the medium. The solvent facilitates the contact of monomer and initiator and helps the process of dissipation of exothermic heat of reaction. It also helps to control viscosity increase. 

Solution Polymerisation In solution polymerisation, the reaction is performed in the presence of a solvent such as ethyl benzene or toluene. 

Although solution polymerisation is able to control and retards auto acceleration, the solvent is rarely intent and the product of lower Molecular weight gets obtained by chain transfer with the solvent. 

Expertise in Emulsion Polymerisation, Solution polymerisation, Process, Product development, Molecular Metal Catalyst and Elastomer,... 

Much the most important polycarbonate in commercial terms is made from 2,2-di(4-hydroxyphenyl)propane, commonly known as bisphenol A. This polymer was discovered and developed by Farbenfabriken Bayer [92], The synthesis and properties of this and many other polycarbonates were described by Schnell in 1956 [93], The polymer became available in Germany in 1959, and was given the trade name Makrolon by Bayer (in the USA, Merlon from Mobay). General Electric (GE) independently developed a melt polymerisation route based on transesterification of a bisphenol with DPC [94], Their product, Lexan, entered the US market in 1960. The solution polymerisation route using phosgene has since been displaced by an interfacial polymerisation. 

We [80] have investigated the solution polymerisation of N-vinylcarbazole (NVC) in benzene in the presence and absence of both initiator and high intensity 20 kHz ultrasound (500Wcm 2) (Tab. 5.21). 

Water-in-oil concentrated emulsions have also been utilised in the preparation of polymer latexes, from hydrophilic, water-soluble monomers. Kim and Ruckenstein [178] reported the preparation of polyacrylamide particles from a HIPE of aqueous acrylamide solution in a non-polar organic solvent, such as decane, stabilised by sorbitan monooleate (Span 80). The stability of the emulsion decreased when the weight fraction of acrylamide in the aqueous phase exceeded 0.2, since acrylamide is more hydrophobic than water. Another point of note is that the molecular weights obtained were lower compared to solution polymerisation of acrylamide. This was probably due to a degree of termination by chain transfer from the tertiary hydroxyl groups on the surfactant head group. 

ISO 2303, 1990. Rubber, Isoprene (IR) Non oil-extended, Solution polymerised types -Evaluation procedure. 

ISO 2476, 1996, Rubber, Butadiene (BR) Solution polymerised types - Evaluation procedure. 

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