Resorcinol Formaldehyde Resin Liquid

An RFL dip consists of an aqueous resorcinol formaldehyde resin liquid with a ruhher latex. The RF resin is used to achieve good adhesion to the organic fiber substrate whether it be rayon, nylon, or polyester. The rubber latex portion can be a natural rubber latex or a styrene butadiene vinylpyridine (terpolymer) latex or even a neoprene latex. This rubber latex is present to achieve good adhesion with the rubber matrix itself. So the RFL allows good adhesion between the rubber and the textile cord reinforcement whether it is used in the manufacture of passenger tires, truck tires, off-the-road tires, power transmission belts, V-belts, timing belts, or various hose products. 

The textile cord or fabric is first immersed in the RFL dip suspension and then passed through a vertical oven under tension at a predetermined elevated temperature and time. This process is called heat setting, where the adhesive dries and coats the cord or fabric while under tension. 

Certain textile fabrics, such as polyester or aramid, possess low surface activity and many times require a special isocyanate or epoxy pretreatment under tension, in much the same manner that the RFL is applied afterwards. So with polyester or aramid cord, two successive dipping operations may be necessary in order to achieve good rubber-to-fabric adhesion. 

Resorcinol formaldehyde resin is a vital ingredient in preparing the RFL dips. Without the RF resin, it would be most difficult to achieve acceptable adhesion with the textile cord substrate. 

An aqueous solution of RF resin is used with different rubber latexes to make the RFL dip needed to treat the textile cord to allow it to achieve rubber-to-cord adhesion during the curing process. It is the RF resin portion of the RFL dip that is responsible for the good adhesion with the textile cord. 

---

Significant reductions in resorcinol content have been achieved from pure resorcinol-formaldehyde resins, to today s PRF resins in which the percentage, by mass, of resorcinol on liquid resins is between 15 and 18%. A step forward has also been the development and commercialization of the honeymoon fast-set system, which in certain countries is used to obtain PRFs of 8 to 9% resorcinol content without loss of performance. 

Phenol-formaldehyde novolac resins are formed by the incomplete polymerization of phenol and formaldehyde. Insufficient formaldehyde is present to allow complete cme. Complete crosslinking can be achieved by adding a powdered methylene donor such as hexamethylenetetramine and heat. Resorcinol-formaldehyde novolac liquid resins can be eured by the addition of powdered paraformaldehyde. 

The same chemical mechanisms and driving forces presented for phenol-formaldehyde resins apply to resorcinol resins. Resorcinol reacts readily with formaldehyde to produce resins (Fig. 2) which harden at ambient temperatures if formaldehyde is added. The initial condensation reaction, in which A-stage liquid resins are formed, leads to the formation of linear condensates only when the resorcinol/formaldehyde molar ratio is approximately 1 1 [119]. This reflects the reactivity of the two main reactive sites (positions 4 and 6) of resorcinol [120]. However, reaction with the remaining reactive but sterically hindered site (2-positiori) between the hydroxyl functions also occurs [119]. In relation to the weights of resorcinol-formaldehyde condensates which are isolated and on a molar basis, the proportion of 4- plus 6-linkages relative to 2-linkages is 10.5 1. However, it must be noted that the first-mentioned pair represents two condensa-... 

In the manufacture of pure resorcinol resins, the reaction can be violently exothermic unless controlled by the addition of alcohols. Because the alcohols perform other useful functions in the glue mix, they are left in the liquid adhesive. PRF adhesives are generally prepared firstly by reaction of phenol with formaldehyde to form a PF resol polymer, that has been proved to be in the greatest percentage, and often completely, linear [95], In the reaction step that follows the resorcinol chemical is added in excess to the PF-resol to react it with the PF-resin -CH2OH groups to form PRF polymers in which the resorcinol groups can be resorcinol chemical or any type of resorcinol-formaldehyde polymer. 

Phenolics Phenol and resorcinol formaldehyde adhesives cure by condensation polymerisation with the elimination of water, and therefore require high curing pressures. They are normally available as two-component systems consisting of a paste resin and a liquid hardener. Traditional uses include wood bonding and plywood fabrication, but nowadays phenolics, especially modified phenolics, are also used in structural bonding of metals and plastics. 

The same chemical mechanisms and driving forces presented for phenol-formaldehyde resins apply to resorcinol resins. As regards application and hardening, PRF adhesives are always delivered as a liquid and must be blended with a liquid or powder hardener (generally paraformaldehyde and wood flour fillers) before use. 

In the realm of boat building or repair such a glue would obviously be required, but there are few candidates that fit this specification. Undoubtedly one of the best and relatively easy to use is resorcinol/formaldehyde which is a two-part adhesive consisting of liquid resin and powder hardener. Mixed just before using, it is a dark red colour that shows up the glue line. 

Resorcinol differs from other phenols in that it reacts readily with formaldehyde under neutral conditions at ambient temperature. To make stable adhesives, which can be cured at the point of use, they are prepared with less than a stoichiometric amount of formaldehyde. About two thirds of a mole of formaldehyde for each mole of resorcinol will give a stable resinous condensation product. The resin is formed into a liquid of convenient solids content and viscosity. Such solutions have infinite stability when stored in closed containers. Glue mixes formed at the point of use from these solutions, on addition of paraformaldehyde-containing hardeners, will have a useful life of several hours due to two principal factors (1) the paraformaldehyde depolymerizes to supply monomeric formaldehyde at a slow rate, as determined by the pH (2) the availability of the formaldehyde is also controlled by the kind and amount of alcohol in the solvent. Formaldehyde reacts with the alcohol to form a hemiacetal. This reaction is reversible and forms an equilibrium which exerts further control on the availability of the formaldehyde. 

The reaction of formaldehyde with unsubstituted phenols leads to either soluble or cross-linked resins since condensation occurs at either ortho or para positions. Monosubstituted [35] (ortho or para) phenols give cross-linking with difficulty but phenols doubly substituted in ortho or para positions yield only low molecular weight products. If only one ortho or para position is available on the phenol then the phenol cannot produce resins and reacts with difficulty with aldehydes [33]. Sometimes cresols and phenol are blended together to obtain fully cured resins. In addition to phenol, the other important phenols that are used to give phenolic resins are o-cresol, mixed cresols, / -/e/ r-butylphenol (from isobutylene and phenol), p-phenylphenol (by-product from phenol manufacture), resorcinol, and cardanol (from cashew nutshell liquid). 

Resorcinol reacts with formaldehyde to produce a liquid RF resin, which is used in the preparation of an REE dip to treat textile fabric to achieve good rubber-to-fabric adhesion. 

Sodium sulfite is used to make resorcinol, which is reacted with formaldehyde to produce RF liquid resin to be used in RFL dip (to achieve good rubber-to-fabric adhesion). 

Depending on the molar ratio of the two reactants we can obtain products which range from syrupy liquids at low formaldehyde levels to completely crosslinked thermosetting resins at high levels of formaldehyde. Novolaks used in tire cord adhesive are RF resins of low formaldehyde content (mol ratio of resorcinol to formaldehyde 1.00/.40 to 1.00/.75) and are prepared under acidic conditions. These resins are manufactured and sold commercially as... 

---