Polyisobutene solution

Viscometric Studies on Polyisobutene Solutions, P.H. Plesch and P.P Rutherford, Polymer, 1960,1, 271-273. 

Data of Broadbent and Lodge (1971) on a polyisobutene solution taken in Couette flow with recessed transducers. Solid curve from cone and plate data of Kaye et al. (1968). 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

Figure 6 The effect of n-butyraldehyde on the specific conductivity of 8.1 x 10"3 mole/1. A1C13 in C2H5C1 at -80° and on the DP of polyisobutenes formed in these solutions [66]...

The effects of the non-polar additives benzene and cyclohexane were compared [69] by studying the effect (at -78.5°) of increasing concentrations of these compounds on the conductivity of solutions of A1C13 and of EtOHAlCl3 in ethyl chloride, and on the DP of the polyisobutenes formed in these solutions. 

Since there is a close correlation between the specific conductivity of the catalytic solutions and the DP of the polymers formed in them, it follows that the electrochemical nature of the solutions must be largely unaffected by the polymerisation. Therefore at most a small fraction of the solute can be involved with the growing chain, and the remainder must be unaffected by the initiation of the polymerisation. This conclusion is strongly supported by the fact that in typical experiments the number of moles of polyisobutene formed was several powers of ten smaller than the number of moles of catalytic complex. 

In the range of concentrations where the inverse correlation between specific conductivity of the catalytic solution and the DP of the polyisobutene formed in it prevails, the principal chain breaking agents must be free ions, the nature and concentration of which are probably very similar to those prevailing before the addition of the monomer. 

The reaction mixtures were clear and colourless at temperatures below about -15° the polymer came out of solution during the reaction. The half-lives of the reactions ranged from 2 to 60 s, the yield, rate, and DP were uninfluenced by the sequence in which the catalyst phial and water phial were broken, the DP of the polyisobutenes ranged from 20 to 2 x 105, and elementary and spectroscopic analyses showed the polymers to contain chlorine, OH-groups and vinyl and tri-substituted double bonds. 

The dependence of the DP on temperature indicates an upper limit of 140° for the ceiling temperature of polyisobutene in about 0.1 base-molar solution". The curvature of this plot at low temperatures indicates that the DP is controlled by different processes at high and low temperatures a similar curvature has been reported by Kennedy and Thomas [52]. 

The high proportion of unsaturated terminal groups found in polyisobutenes prepared in solution at low temperature [18] makes it appear likely that a similar process operates there, although the reaction (V) above might also account for at least some of these under certain conditions. 

Electrical Conductivity. A further topic which needs to be considered is the correlation found by Zlamal, Ambroz, and Vesely [2] between the specific conductivity of solutions (mainly in ethyl chloride) of aluminium chloride containing various quantities of a polar compound (acetonitrile, butyraldehyde, ethanol, etc.) and the DP of the polyisobutenes formed in these solutions. Over a certain range of concentrations there is an inverse correlation between the specific conductivity, which has a sharp minimum when the ratio [AlCl3]/[Additive] = 1, and the DP, which at the same composition shows a sharp maximum. 

Since there is a very close correlation between the specific conductivity of the catalytic solutions, e.g., A1C13, EtOH in ethyl chloride, and the DP of polyisobutenes obtained when isobutene is added to these solutions, it follows that the electrical condition of the solutions before and after the addition of the monomer must be essentially the same. This means that the number of solute molecules involved in the initiation of polymerisation... 

The time-conversion curves do not pass through the origin in spite of all precautions taken, there was always a small dark reaction. This dark reaction is obviously caused by traces of light penetrating into the ampule during the preparation and is not caused by a thermal reaction. The conversion of the dark reaction in experimental times is always so small that it does not have any implications for the size of the radiation-induced reaction. Irradiation of a solution of polyisobutene in carbon tetrachloride in the absence of chlorine showed that only negligible amounts of chlorine (about 2 weight %) were taken up from the solvent. 

The ratio (U0 — U)f(U — l/L) observed from the solutions of polyisobutene in various hydrocarbons is proportional to the absorbed dose as expected from Eq. 16 [70]. Schnabel et al. found that the LSI decreased with time in the... 

Crude experiments were performed in the laboratory with substances unlikely to show significant weight change by adsorption of water or oxygen and sufficiently volatile for loss to be recorded conveniently on an ordinary balance. Petri dishes (41 sq. cm. area) were used to contain the substances, mostly liquids and used in the pure state. Two solids were included p-dichlorobenzene and naphthalene. These were layered in coarse powder form, and the surface was sprayed with a solution of low molecular weight polyisobutene in petroleum ether until it was sticky enough to prevent blowing of the powder in the wind it was intended to use. 

Bawn, C. E. H. Patel, R. D., "High Polymer Solutions. Part 8. The Vapour Pressure of Solutions of Polyisobutene in Toluene and Cyclohexane," Trans. Faraday Soc., 52, 1664 (1956). 

Polymer additives that can be incorporated in the polymerization process or post-compounded into the HIPS product can add significant enhanced functionality. The use of 2 % polyisobutene (PIB), for instance, in the HIPS process feed solution in place of the usual plasticizer can dramatically increase ESCR by a factor of 10 for both standard- and ESCR-grade HIPS. It is interesting that even in the presence of PIB, RPS still has a significant effect on ESCR, as seen in a comparison of extrusion-grade with ESCR-grade HIPS in Table 12.12. 

J. R. Richards, and J. D. Frbry Viscoelastic prc erties of concentrated solutions of polyisobutene in cetane. II. Creep and viscous flow. J. Ph5rs. Chem. 67, 327 (1963). 

Aromatic hydrocarbons are used as diluents in solutions of cellulose nitrate, cellulose esters, and ethers with true solvents such as esters and ketones. Rubber, polyisobutene, and molten polyethylene also dissolve in them. Poly(vinyl chloride), solid polyethylene, polyamides, and shellac are, however, insoluble or only swell. 

Processes for modifying polyacetylene in a solution of polymers such as rubbers, polyisobutene, etc. have been described in detail in Government Report 03 C 1340 [15] and will not be discussed further here. This also applies to work involving polymerization in high— viscosity media other than silicone oil. Of general interest, however, are stability studies on the new type of polyacetylene N-(CH) t. 

It was noted in the previous chapter (Section 1.4.2.1.) that the polymerization of isobutene could be accomplished only with cationic initiators. Aluminium chloride and boron trifluoride are the preferred initiators for commercial processes the separate addition of a co-catalyst is not generally necessary and adventitious substances possibly fulfil this role. At ordinary temperatures polymerization is extremely rapid and leads to low molecular weight polymers which are viscous oils or sticky solids. However, at low temperature (—80 to — 100°C) high molecular weight material is produced. Even at these low temperatures the reaction is complete in a few seconds and it is necessary to have particularly efficient means of dissipating the heat evolved. Conventional batch processes are unsuitable and continuous processes are used in which only small quantities of reactants are involved at any one moment. In one process (Badische Anilin- Soda-Fabrik A. G.), solutions of isobutene and boron trifluoride in liquid ethylene are mixed on a moving belt so that the polymerizing system is in the form of a thin film and heat is removed by the vaporization of the solvent. The polymer is then mixed with an alkali or ethanol to deactivate the initiator and treated with steam to remove water-soluble contaminants. Another process for polyisobutene (Standard Oil Co. (N.J.) (U.S.A.)) follows closely the procedure outlined in Section 2.10.2. for the manufacture of butyl rubber. 

Polyisobutene is non-crystalline when unstretched and is therefore soluble at room temperature in hydrocarbons and halogenated hydrocarbons. The material is resistant to most acids, alkalis and aqueous solutions, as would be expected... 

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