Phenol-formaldehyde resin solution containing water soluble alkaline earth metal salt

#1. Field of the Invention

#The present invention relates generally to resins for use in preparing binders for products formed from mineral fibers, and more specifically, to processes for preparing water-soluble phenol-formaldehyde resins, binders for glass fiber including such resins, and glass fiber products formed using such binders.

#2. Brief Description of the Prior Art

#The following examples are illustrative of the processes and compositions of the present invention and will be useful to those of ordinary skill in the art in practicing the invention. However, the invention is in no way limited by these examples. Unless otherwise indicated all percentages are given on a weight basis in the following examples.

#100 Kg of commercial grade phenol and 223.4 Kg of a 50% (w/w) aqueous solution of formaldehyde are introduced into a reactor. The reactor is heated and the contents are agitated until the temperature of the mixture stabilizes at 45.degree. C. The temperature is maintained at 45.degree. C., and 3.5 Kg of calcium oxide is added at a steady rate over a 30 minute period. Immediately upon completion of addition of the calcium oxide the temperature of the mixture is adjusted to 70.degree..+-.1.degree. C. within a maximum period of 30 minutes. The temperature is then maintained for about 100 minutes. At a critical time when the free formaldehyde content, evaluated in relation to the weight of the reaction mixture, reaches a value of 10.2.+-.0.1% (w/w), cooling of the reaction mixture is begun. The time when the condition is met is obtained by extrapolation of an experimental measurement of free formaldehyde content at a time of about t+20 minutes ("t" is the time when 70.degree. C. is initially reached). The extrapolation is made using a calibration curve previously determined experimentally for the particular reactor, reaction mixture and reaction conditions used. The calibration curve gives evolution of free formaldehyde as a function of time at 70.degree. C. The contents of the reactor are cooled to 20.degree. C. in 40 minutes or less. The pH of the reactor contents is adjusted by addition of about 9 Kg of 100% sulfamic acid to give a pH of 6.5.+-.0.2, sufficient time being allowed to ensure that the sulfamic acid has completely dissolved before the final pH reading is taken. The resulting aqueous resin solution is stored at 14.degree..+-.2.degree. C., and has a nominal solids content of 52.0% (w/w), a free phenol content of 1.2% (w/w), a maximum free formaldehyde content of 10.0% (w/w) and is infinitely dilutable with water. The calcium oxide reagent employed is to have an actual calcium oxide content of at least 96.3% (w/3w) and a maximum silicon dioxide contents of less than 0.50% (w/w).

#42.4 g of a 46% (w/w) aqueous solution of phenolformaldehyde resole resin prepared according to Example 1 was mixed with 10.5 g urea and 47.1 g water (65/35 resin solids/urea weight ratio). The resulting binder solution remained clear after 24 hours.