Rwe-dea Aktiengesellschaft Fur Mineraloel Und Chemie

Matthias Lattekamp

Adolf Buschfeld

Gerd Ripkens

Hans Schittek

Hans-Jurgen Krezmin

Manfred Gramse

Process for producing urea-modified, highly reactive phenolic resins

The inventive concept is to condense the phenol formaldehyde resins to a higher molecular weight than usual so far. Subsequent addition of urea thereto reduces viscosity to normal levels and increases solid content. The added urea does not take part in condensation reaction but partly reacts in the alkaline medium with formaldehyde to methylol urea (in a so called equilibrium reaction), which is formaldehyde donor for the phenol formaldehyde crosslinking reaction during the pressing of the particle board. The present invention relates to a process for producing modified phenolic resin bonding agents, characterized by preparing as known per se phenol-formaldehyde resins with a viscosity of more than 300 mPa.s (at 20.degree. C.) and with a solids content of from 65 weight percent and adding to the viscous phenolic resin solutions obtained 5 to 50 weight percent urea, based on the weight of the phenolic resin solution, the phenol formaldehyde resins being prepared with as much alkali as is required to secure that the modified resin solution resulting therefrom contains 2 to 12 weight percent total alkali calculated as NaOH. The solids content of the modified resin solutions ranges of from 20 to 65 weight percent, preferably of from 40 to 65 weight percent. The modified resin solutions prepared according to invention are bonding agents for producing particle boards, preferably triple- or multilayer particle boards. The modified resin solutions of the invention containing 2 to 6 weight percent alkali can be used as outer layer bonding agents. The modified resin solutions of the invention containing 2 to 6 weight percent alkali can be used in combination with isocyanate bonding agents as outer layer and particularly as center layer bonding agents, the bonding agents being applied to the particle either separately or jointly, the latter being preferred. The modified resin solutions of the invention containing more than 6 to 12 weight percent alkali can be used as outer layer and particularly as center layer bonding agents.

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Rheinberg, Germany

Matthias Lattekamp