Sulphonated phenolic resins

Phenolic resins also find use in varnishes, electrical insulation, and in other protective coatings. Heat-settings adhesives which are based on phenolics find use in producing plywood. These also find use in the production of ionexchange resins having amine, sulphonic acid, hydroxy or phosphoric acid functional groups. 

With one exception [447], only sulphonated resins were used as catalysts in kinetic studies of esterification and transesterification, the resins being almost exclusively styrene—divinylbenzene copolymers in one case, a sulphonated phenol—formaldehyde resin was also used [433]. The main factors determining the catalytic activity are (i) the concentration of functional groups in protonated form (— S03H groups) and (ii) the degree of crosslinking of the copolymer (characterised by the divinylbenzene content). 

The novalac phenolic resins react under weakly acidic and anhydrous conditions using metal catalysts of the divalent state, e.g. Ca, Mg, Zn, Pb, Cd, Co, Ni and Cu acetals, halides or sulphonates. The mechanism of this ortho-hydroxymethylation reaction has been attributed to the formation of chelate complexes as intermediates as proposed occurs at the initial and subsequent condensation reaction of the phenolic alcoholics. It has been shown that electropositive bivalent metals work best when pH is between 4 and 7. This may be described as follows ... 

A wide range of products, including every class and type of surfactant, has been found to exhibit demulsification properties. The most commonly used products in lubricant formulations contain anionic surfactants such as alkyl-naphthalene sulphonates. Nonionic alkoxylated alkyl-phenol resins and block copolymers of ethylene oxide and propylene oxide are also used. 

A variety of poly/dihydric oils are used for the preparation of glyddyl ether-type epoxy resins. These include bisphenols, namely bisphenol-A (BPA), bisphenol-F (BPF), bisphenol-S (BPS) and bisphenol-H (BPH) and so on. Other aromatic diols and polyols such as phenolic resin, MF resins and hyperbranched polyol may also be used in the preparation of vegetable oil-based epoxy resins. Bisphenol-A (2,2-bis(4-hydroxyphenyl)propane) is one of the most widely used aromatic diols for the synthesis of epoxy resin. The resins are commonly used as lacquers for coated metal products such as food cans, bottle tops and water pipes. There are also reports on the use of bisphenol-S (BPS) (bis(4-hydroxyphenyl) sulphone), in the synthesis of epoxy resin. The advantages of resistance to deformation by heat and improvement of thermal stability were observed for such epoxy resins. The presence of sulphone group (BPS-based epoxy resin) in the epoxy resin exhibits better gel time than BPA-based epoxy. Another important diol, namely bis(4-hydroxydiphenyl)methane or bisphenol-F (BPF) is used for the synthesis of low viscosity epoxy resins. BPF generally comprises several isomers such as bis(2-hydroxylphenyl)methane (i.e. ortho-ortho isomer), bis(4-hydroxylphenyl)methane (i.e. para-para isomer) and... 

Other processes include the alkylation of phenol using alkenes, and the manufacture of acrylate and methacrylate esters from alcohols and the corresponding acids. Olefin hydration reactions require more extreme conditions but Deutsche Texaco have developed a resin-catalysed propene hydration process to form isopropyl alcohol [125]. The reaction is run at 130 C near the upper limit for sulphonic acid resins, but a species with sufficient lifetime is available. There is even some evidence that butene hydration is now carried out similarly. Finally, B.P. Chemicals have recently disclosed [126] a new olefin isomerisation process yielding 2,3-dimethylbut-l-ene. Here the conditions required to favour the isomerisation versus rapid oligomerisation had to be identified to establish a viable process. 

Picric acid, the 2 4 6-trinitro derivative of phenol, cannot be prepared in good yield by the action of nitric acid upon phenol since much of the latter is destroyed by oxidation and resinous products are also formed. It is more convenient to heat the phenol with concentrated sulphuric acid whereby a mixture of o- and p-phenolsulphonic acids is obtained upon treatment of the mixture with concentrated nitric acid, nitration occurs at the two positicsis mela to the —SOjH group in each compound, and finally, since sulphonation is reversible, the acid groups are replaced by a third iiitro group yielding picric acid in both cases ... 

At one time the requirement for phenol (melting point 41°C), eould be met by distillation of eoal tar and subsequent treatment of the middle oil with eaustic soda to extraet the phenols. Such tar acid distillation products, sometimes containing up to 20% o-cresol, are still used in resin manufacture but the bulk of phenol available today is obtained synthetically from benzene or other chemicals by such processes as the sulphonation process, the Raschig process and the cumene process. Synthetic phenol is a purer product and thus has the advantage of giving rise to less variability in the condensation reactions. 

The availability of Nafion on silica has not only lowered the cost of the resin but also has made it versatile (Sun et al., 1997 Harmer et al., 1998). A number of industrially important reactions have been attempted, with considerable success, with these catalysts. Consider the Fries rearrangement of phenyl acetate to p-acetyl phenol (/t-hydroxy acetophenone). This has been accomplished by Hoelderich and co-workers (Heidekum, 1998). In the ca.se of alkylation of benzene with benzyl alcohol, Amberlyst-15 and p-toluene sulphonic acid are ineffective and Nafion on silica works well at 80 °C. 

Kressman, T. R. E., and Kitchener, J. A. (1949). Cation exchange with a synthetic phenol-sulphonate resin, V. Kinetics. Discuss. Faraday Soc. 7, 90-103. 

Resorcinol, 1-3-Di-hydroxy Benzene.—The meta-di-hydroxy benzene is known as resorcinol or resorcin. It is also obtained from plant resins by alkali fusion. Synthetically it is prepared from phenol meta-sulphonic acid and from meta-chlor phenol. In the case of chlor phenol the para compound also yields meta-di-hydroxy benzene due to position rearrangement. 

In contrast to aliphatic alcohols, which are mostly less acidic than phenol, phenol forms salts with aqueous alkali hydroxide solutions. At room temperature, phenol can be liberated from the salts even with carbon dioxide. At temperatures near the boiling point of phenol, it can displace carboxylic acids, e.g. acetic acid, from their salts, and then phenolates are formed. The contribution of ortho- and -quinonoid resonance structures allows electrophilic substitution reactions such as chlorination, sulphonation, nitration, nitrosation and mercuration. The introduction of two or three nitro groups into the benzene ring can only be achieved indirectly because of the sensitivity of phenol towards oxidation. Nitrosation in the para position can be carried out even at ice bath temperature. Phenol readily reacts with carbonyl compounds in the presence of acid or basic catalysts. Formaldehyde reacts with phenol to yield hydroxybenzyl alcohols, and synthetic resins on further reaction. Reaction of acetone with phenol yields bisphenol A [2,2-bis(4-hydroxyphenyl)propane]. 

Table 1.1 (see page 8) shows that polymerization reactions featured in by far the most incidents, followed by nitration, sulphonation and hydrolysis reactions. Of the polymerization reactions, 20% involved phenol-formaldehyde condensations. In view of the number of incidents with phenol-formaldehyde resin production the British Plastics Federation (BPF) came forward with an exemplary approach to the problem in its publication Guidelines for the Safe... 

Later resins of this type, i.e. strongly acidic cation exchangers, have been synthesized directly by condensation of compounds which already contain sulphonic acid groups and phenolic groups, to form polymers, e.g. a mixture of phenol, phenolsulphonic acid and formaldehyde, in the presence of sodium hydroxide as a catalyst. ... 

Similarly, the commercial resins Wofatit K and Wofatit K.S. marketed by I. G. Farben are made by reacting benzaldehyde-2 4-di-sulphonic acid, resorcinol and formaldehyde. Phenol is also present in the production of Wofatit K.S. The final heating stage with formaldehyde is continued until a gel is formed. This is then cooled, washed and dried for several days at 80°C to 90°C, to give a resin which is fairly hard and has an exchange capacity of about 2-8 m-eq/g. ... 

P963 is a liquid phenolic resole designed to be used with catalyst P964 (para tolune sulphonic acid phosphoric acid) for the production of hand-lay or low pressure/low temperature compression moulding. The resin contains 10% acetone to provide a useable mix viscosity, fast binder breakdown and reinforcement wet-out. Principal use is for thin-walled aircraft components. 

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