Лако-красочные материалы — производство

As the formulations show, straight blood and soybean-blood blend glues are prepared in generally the same sequence and manner as outlined for soybean glues. Finished glue viscosity ranges are somewhat lower, typically 5000-8000 cP for hot-press formulations and 8000-20,000 cP for the thicker and grainier cold-press glues. Glue life at room tem­perature is 4-8 h: the cooler, the longer.

With respect to application methods, blood glues can be spread on wood surfaces by most conventional means. These include roller, knife, and extrusion but do not include curtain coating or spray, for which the glues must be thinned below practical film retention levels. The major advantage of alkaline-dispersed blood glues over all other wood glues except resorcinol-based synthetic resin adhesives is their sensitivity to heat, resulting in extremely

fast hot-press curing times [54]. This property is of sufficient importance to warrant reproducing an entire plywood hot-pressing schedule for purposes of comparison. The commercial blood glue pressing times shown in Table 14 are literally half those of current phenolic plywood resin adhesives. They are also significantly faster than those listed earlier

Other conditions:

1. Total assembly time limit per press load, 16 min.

2. Veneer temperature not to exceed 43°C.

3. Veneer moisture content not to exceed 8%.

4. On rough or warm veneer, add at least 12 g of extra glue spread.

5. Not less than 12 kg/cm2 uniform hydraulic pressure.

aStand time after assembling last panel before loading press.

for soybean glues. This hot-pressing schedule is suitable for all straight blood adhesive formulations and also for soybean-blood blend glues containing at least half blood as the active protein ingredient.

Blood and soybean-blood blend glues of appropriate high viscosity and granular consistency can be pressed cold according to the schedule shown for soybean glues. For this purpose they must contain a terminal addition of about 5% preservative based on dry glue weight in order to meet product standards for mold resistance [24].