Resole Production

Abstract

Resoles are phenol-formaldehyde condensation products prepared with a molar ratio of F:P of ≥ 1, basic catalysts, and lead to reactive phenolic resins with methylol functional groups. A wide variety of additives can be added to provide the final resin with the desired properties such as flame retardancy, plasticization, pigmentation, or improve processability by using release agents, wetting agents, and other surfactants. Most resoles are waterborne, but in some certain applications, they can be solvent based with either alcohols or ketones as solvents.

A vast majority of resoles are manufactured by batch conditions, with the reactor size dependent upon the end-use application. Reactors of 50 m³ are used for large volume applications, such as mineral wool or wood binders, while lesser volume reactors are used for other lower volume uses.

The convenience of “in-line” monitoring allows the determination of resin reaction to progress and whether the resinous material is ready for the next stage of the process or ready to be discharged. Typical “in-line” process tests include pH, viscosity, water tolerance, and gel time.

Raw materials of most modern phenolic resin manufacturers are charged automatically via closed systems using mass flow meters so that there is no contact of the potentially very harmful chemicals with the operator. To ensure the prevention of run-away reactions that may occur from the exothermic reaction of phenol with formaldehyde under basic conditions, formalin (37–52%) is added continuously over an extended period of time. This allows an adequate temperature control and gives the possibility to interrupt formalin addition if the temperature is increasing to fast. An alternate method is the staged addition of catalyst which reduces energy in the system but is generally less effective in the prevention of run-away reaction than the continuous formalin addition method.