Fixation process for heat-fixable preservative treated wood

A process for treating wood with heat-fixable preservatives, which comprises:

• (a) placing untreated wood in a treatment vessel adapted for pressure;
• (b) applying a vacuum to said wood within said treatment vessel;
• (c) introducing said heat-fixable preservative into said treatment vessel in an aqueous treatment medium while substantially maintaining said vacuum;
• (d) raising the pressure within said treatment vessel and impregnating said wood with said heat-fixable preservative;
• (e) releasing said pressure and removing said heat-fixable preservative from said treatment vessel;
• (f) applying a vacuum to remove excess preservative;
• (g) releasing said vacuum, recovering said removed excess preservative to avoid spillage, and removing said treated wood from said treatment vessel;
• (h) placing said treated wood in a fixation vessel;
• (i) filling said fixation vessel with an aqueous liquid heating medium supplied from a fixation work tank, and preheated to a temperature of at least about 130.degree. F. and no greater than about 200.degree. F.;
• (j) controlling contamination of said aqueous liquid heating medium (1) by wood extractives, (2) by unfixed preservative from said wood, and (3) by sludge formed from said wood extractives and said unfixed preservative within said aqueous liquid heating medium;
• on an intermittent and/or continuing basis at one or more points in the overall process;
• by employing any one or more of the following procedures, in any combination thereof:
• (1') cooling aqueous liquid heating medium and rinse water from step (n) recited further below, which have been removed together from said fixation vessel, by heat exchange with clean water, thereby producing (i) cooled aqueous liquid heating medium and rinse water which are used for preparing fresh heat-fixable preservative treatment solution, and (ii) heated clean water which is reserved for rinse step (n);
• (2') filtering said aqueous liquid heating medium to remove particulate sludge and other particulate matter therefrom which may compromise the appearance or performance of finished product from said method;
• (3') adding to said aqueous liquid heating medium one or more members selected from the group consisting of agents for adjusting the pH of said aqueous liquid heating medium;
• and
• (4') establishing pressure in said fixation vessel which opposes movement of said wood extractives and unfixed preservative into said aqueous liquid heating medium;
• (k) maintaining contact of said aqueous liquid heating medium for a period of from about thirty minutes to about two hours to effect fixation of said preservative;
• (l) removing said aqueous liquid heating medium from said fixation vessel;
• (m) applying a vacuum in the range of from about 10" to about 20" Hg for a duration of up to about 30 minutes;
• (n) rinsing the thus treated and fixed wood in said fixation vessel with heated clean water, heated to a temperature no greater than about 200.degree. F.;
• and
• (o) releasing said vacuum, removing said rinse water from said fixation vessel, and removing said wood from said fixation vessel.