Method of making molding compounds and products produced thereby

#The present invention relates to a controllable and improved method of producing molding compounds of aldehyde condensates directly from the monomers and to the materials produced thereby.

#The condensation reactions of aldehydes, and particularly the condensation reactions of phenols and aldehydes are, or can be, quite violent, inasmuch as they generate a considerable amount of heat. Aldehyde condensate resins are relatively cheap and have been used as binders for molded articles, and foundry molds, for a long time. Aldehydes can be reacted with donors of hydrogen atoms, as for example, benzene rings containing hydroxyl groups, amines including urea, dicyandiamide, and melamine, etc., to form alkanol groups which then react with other hydrogen donors by splitting off water. These reactions liberate a considerable amount of heat and because water is also liberated, the aldehyde condensate resins are usually made in water solutions. Some control of the reaction is usually achieved by flashing water from the solutions. In addition the reactions are usually carried out in kettles containing cooling coils or jackets, so that the reactions can be stopped before the condensate resins reach a completely crosslinked and infusible state. The fusible partial condensates at this point are usually solids at room temperature and are used as binder forming materials for porous articles and electrical applicators.

#The fusible B staged aldehyde condensates give off water when they react with further aldehyde to produce the infusible C-stage. When such aldehyde condensates are to be used as molding compounds, they are mixed with fillers, and are compressed between heated surfaces to cross-link the partial condensates. One of the problems with such molding compounds is that the water liberated tends to decrease the bond strength that is produced with the fillers and/or it produces porosity in the finished molded article.

#According to the present invention, the reaction between a phenol and an aldehyde to form the binder of a molding compound is carried out in the presence of a base. Any relatively strong base can be used and the preferred bases are Ca(OH).sub.2, Ba(OH).sub.2 and Mg(OH).sub.2. This base is first reacted with the phenol material to form the phenolic salt. When portland cement is used as a filler, sufficient free calcium hydroxide exists throughout the portland cement to act as the catalyst for the reaction. In this case, the portland cement is reacted with the phenol, preferably after the portland cement has been partially hydrated, but is in a dry state. Phenol inhibits the hydration of portland cement and so by first hydrating the cement, water can be incorporated in a manner providing a dry material. The mixture of the filler, and calcium phenolate salt is then mixed with an aldehyde, preferably in the solid state, and is thoroughly mixed. A reaction proceeds without the further addition of water in a very controlled manner to a B-stage to form a molding compound. If the molding compound is in the form of thin sheets or has sufficient surface to volume ratio, the reaction will slow down after it reaches the B-stage, so that very little, if any, additional cooling is necessary to stop the reaction, when the resin is in a proper state for molding.

#The following materials in parts by weight were mixed according to procedures which will hereinafter be designated "A" and "B" respectfully.

#In this procedure 52.83 parts of portland cement was mixed with 7.89 parts of water and was aged 5 days to hydrate the cement. The resulting mixture was ground into a fine powder, and 8.79 parts of water was mixed therewith. This wet mixture was then introduced into 69.51 parts of melted phenol at 60.degree. C and reacted for 30 minutes. The reaction proceeded to a dry state and the phenol cement reaction product was then ground into a fine powder and was mixed with 24 parts of paraformaldehyde. The mixture was spread out on a surface to a thickness of approximately 1/8-inch; and after a period of time, a reaction was self-initiated and a temperature of approximately 200.degree. F developed. Thereafter, the temperature started to decrease. Portions of the molding compound so produced were then molded at 300.degree. F and 1,000 psi for 3 minutes. The molded parts had a strength comparable to those made from the same materials, but in which a resin was first made of the phenol and paraformaldehyde to form a resole, as is done in conventional processes.