Synthesis of Resole

The final structure of resins produced depends on the reaction condition. Formaldehyde to phenol (F/P) and hydroxyl to phenol (OH/P) molar ratios as well as ruction temperahne were the most important parameters in synthesis of resols. In this study, the effect of F/P and OH/P wt%, and reaction temperature on the chemical structure (mono-, di- and trisubstitution of methyrol group, methylene bridge, phenolic hemiformals, etc.) was studied utilizing a two-level full factorial experimental design. The result obtained may be applied to control the physical and chemical properties of pre-polymer. 

Only a few studies have tackled the problem of deriving a detailed kinetic model of the phenol-formaldehyde reactive system, mainly because of its complexity. In recent years, a generalized procedure has been reported in [11,14] that allows one to build a detailed model for the synthesis of resol-type phenolic resins. This procedure is based on a group contribution method and virtually allows one to estimate the kinetic parameters of every possible reaction taking place in the system. 

Wang, H. Zhao, T. Yan, Y. Yu, Y. Synthesis of resol-layered silicate nanocomposites by reaction exfoliation with acid-modified montmorillonite. J. Appl. Polym. Sci. 2004, 92, 791-797. 

Synthesis of Resole Type Prepolymers 1. Catalysts for the Synthesis of Resoles... 

Rate Constants and Ionic Radius of Hydrated Cations Applied for Synthesis of Resoles by Using a Ratio of Methanal/Phenol = 1.5 at 60°CandapH Valueof 8 (data from ref [73])... 

Resole is produced by reaction of a phenol or a phenol derivative with an excess amount of formaldehyde in the presence of a base catalyst. The reaction in basic medium proceeds through the addition of formaldehyde with the phenoxide ion, leading to the formation of o- or p-monomethylol phenol (along with some di- or trimethylol phenol) as established by complexation via cyclodextrin or crown ether [2]. The reaction scheme for the synthesis of resole is shown in Figure 2.3. 

When unsubstituted phenols are used in the synthesis of resols, the resins formed are a mixture of monomeric and polymeric hydroxymethylphenols, as shown in reactions (25) and (26). Since formaldehyde will react at the ortho and para positions to the phenolic hydroxyl, the composition of resols formed will depend on the P/F ratio and various reaction conditions, such as time and temperature. Resols are generally neutralized or made slightly acidic before the crosslinking reaction is carried out. Heat curing is the most important curing process and is usually performed at... 

As we have already mentioned, the cure of resoles takes place primarily through further extension of the condensation process, though the conditions are usually considerably different from those of synthesis. The changes in conditions normally include exposure to much higher temperatures and higher concentrations of polymer than are seen in resin synthesis. The pH of the medium may also... 

MATERIALS FOR THE SYNTHESIS OF NOVOLAC AND RESOLE PHENOLIC OLIGOMERS... 

Phenol-formaldehyde resins using prepolymers such as novolaks and resols are widely used in industrial fields. These resins show excellent toughness and thermal-resistant properties, but the general concern over the toxicity of formaldehyde has resulted in limitations on their preparation and use. Therefore, an alternative process for the synthesis of phenolic polymers avoiding the use of formaldehyde is strongly desired. 

Reimer-Tiemann reaction 685, 1071 Resole resins 1457, 1458, 1460 model compounds of 1476-1487 synthesis of 1475, 1476 Resol prepolymers 969 Resonance Assisted Hydrogen Bonding (RAHB) 552... 

The cross-linked polymers obtained from the addition-cure approach are often a complex arrangement of atoms bonded in heterocyclic and carbocyclic rings. However, the objective in the preparation of these systems is not simplicity. It is to obtain systems with the desirable properties of phenolic resins retained and the undesirable properties improved or removed. Voids are an undesirable result in the synthesis of both resols and novolacs. Hence, addition-cure phenolic resins are designed to avoid this result. Ease and flexibility of processing are also sought in the addition-cure systems. 

Byun, H.Y. Choi, M.H. Chung, I.J. Synthesis and characterization of resol type phenolic resin/layered silicate nanocomposites. Chem. Mater. 2001, 13, 4221-4226. 

While novolac links may form at elevated temperature during resole synthesis (Scheme 1.12), the preferred synthesis of novolac resins takes place under acid conditions (pH from 1 to 4) and with an excess of phenol. In this case the methylol intermediates cannot be isolated since they react rapidly to give methyene-bridged structures with relative molar mass <2000, as shown in Scheme 1.15. 

Zhao and co-workers have made major advances in the soft-template synthesis of mesoporous carbons. They reported the self-assembly of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) and resol mixtures and successful removal of the templates including F127, F108 and P123 at a series of temperatures to produce mesoporous polymer and carbon materials. " ° Eigure 4.10 illustrates the five-step synthesis procedure reported by Meng et Low-... 

Synthesis of phenol-formaldehyde oligomers uses as the main raw materials phenol and formic aldehyde. Both are used in the form of aqueous solutions of 90% and 40-45% concentration, respectively [1], Since formaldehyde contains small amounts of formic acid, the condensation process can take place in the absence of catalysts, so that phenol-formaldehyde oligomers can be obtained. The reaction rate is, however, quite low when the process takes place at atmospheric pressure and a temperature around 100°C. The use of acid or basic catalysts is compulsory in industry to produce phenol-formaldehyde oligomers of desired characteristics. Novolac type oligomers are obtained in acid catalysis in basic catalysis, resol type oligomers are produced. 

---