22 июля, 2015 
Malyar As with the soybean glues discussed previously, dried blood adhesives must initially be wetted or redissolved in plain water and then be subjected to one or more alkaline dispersing steps. Unlike vegetable proteins, however, high-solubility blood proteins can be dispersed and rendered strongly adhesive by more moderate alkaline agents such as hydrated lime or ammonia [47]. Especially with a denaturing compound added, these glues represented the most water-resistant adhesives available until the advent of phenol-formaldehyde resins [5]. An example is shown in Table 8. This mix is unique in the quantity of denaturant it employs. The aldehyde reaction actually causes the blood protein to gel for a short period before thinning out again to a working viscosity level.
Table 8 Blood Glue: Ingredients and Mixing Procedure
Amount
(kg)
90% Soluble spray-dried animal blood 50.0
Water at 16-21°C: mix 3min or until smooth 40.0
Water at 16-21°C: mix until smooth 30-60
Ammonium hydroxide, sp. gr. 0.90: mix 3min 3.0
Powdered paraformaldehyde (sift in slowly while mixing) 7.5
Amount
_______________________________________________________________________________________________________________________ (kg)
Water at 16-21 °C 150
20% Soluble spray-dried animal blood 37.5a
74-p. m Wood flourb 10.5a
Pine oil or diesel oil defoamer: mix 3 min or until smooth 2.0a
Water at 16-21°C: mix 2min or until smooth 165.0
Fresh hydrated lime (as a slurry in) 5.0
Water at 16-21°C: mix 1 min 10.0
50% Sodium hydroxide solution: mix 10min 8.0
Sodium silicate solution: mix 5 min 17.5c
“Normally dry-blended for easier handling and dust control. b0.074mm (200 mesh) and finer. c8.90% Na2O, 28.70% SiO2, 41° Baume.
Table 10 Hot Water-Coagulated Blood Glue: Ingredients and Mixing Procedure
Amount
_______________________________________________________________________________________________________________________ (kg)_
Water at 63°C 100.0
90% Soluble spray-dried animal blood 40.0a
74-p. m Wood flourb 9.0a
Pine oil or diesel oil defoamer: mix 10 min 1.0a
Water at 10-16°C 175.0
Pine oil or diesel oil defoamer: mix 2min or until smooth 1.0
Fresh hydrated lime (as a slurry in) 3.5
Water at 10-16°C: mix 2min 7.0
50% Sodium hydroxide solution: mix 2min 7.5
Sodium silicate solution: mix 5 min 17.5c
aNormally dry-blended for easier handling and dust control. b0.074 mm (200 mesh) and finer. c8.90% Na2O, 28.70% SiO2, 41° Baume.
The useful life is 6-8 h. This formulation can be cured hot or cold, but hot pressing yields the most durable bonds.
The next resurgence of blood glue technology came during and after World War II. By that time, the highly alkaline multistep dispersing systems of soybean glues had become well established and were employed successfully with blood glues. Two examples utilizing low-solubility blood in typical plywood glue formulations are shown in Tables 9 and 10. The second mix (Table 10) demonstrates the use of hot water to coagulate the blood and lower its solubility during the mixing procedure [48]. Both these glues are excellent adhesives for interior-grade plywood when cured either hot or cold. Preservative or denaturant additions are not normally required to meet plywood performance standards.
As a point of interest, blood glues are not affected by many of the protein denatur — ants used to improve the performance of soybean glues: specifically, sulfur compounds and complexing salts [49]. However, they are very sensitive to aldehyde-acting compounds, and
these have been employed at levels of 0.1-1.0% to yield improved consistency and water resistance. Typical of these are glyoxal, paraformaldehyde, methylol ureas, and formaldehyde addition compounds such as dialdehyde starch and sodium formaldehyde bisulfite.
A special class of blood protein denaturants, used primarily with higher levels of blood solubility, are the alkaline phenol-formaldehyde (PF) resins. Low-molecular- weight, low-alkali PF resins cause granulation of dispersed blood protein without much effect on viscosity, usually a reduction [50]. Highly advanced, high-alkali PF resins such as those used as plywood adhesives generally cause rapid thickening and gelation of dispersed blood glues if not employed with care [33,51]. Resins of intermediate advancement and alkalinity are almost passive to dispersed blood. These interactions have been exploited to formulate blood-resin glues for different hot-press applications at almost every level of combination. Two examples at the extremes of the range will suffice (Tables 11 and 12). In the case of the low-resin-content formulation (Table 11), PF resin addition also functions as a preservative agent and was used widely for the purpose. This formulation is for hot pressing only. The bond-durability level can be characterized as ‘‘mid-exterior’’.
For the high-resin-content formulation (Table 12), a partial addition of the PF resin can be made just after the initial mix and before sodium hydroxide addition if more fluidity is needed for propeller-type stirring. This formulation is more properly termed a blood-fortified exterior PF resin adhesive for hot-pressing plywood or laminated veneer lumber [52]. Even in quantities this small, the effect of the animal blood is to reduce the hot-press curing time by 20-30% over that of phenolic resins used alone. For purposes of adhesive solid, calculation, the blood content can legitimately be included with the phenolic resin solids.
A special application for which 80% soluble blood is particularly suited is its use in phenolic resin glues as a foaming agent to produce ‘‘air-extended’’ PF adhesives [53]. These are currently used to manufacture plywood on automated production lines. For this purpose, the mixed adhesive containing blood is put through a special high-speed stirring and air-injection system that lowers the specific gravity of the adhesive from about
Table 11 Low-Resin Blood Glue: Ingredients and Mixing Procedure
Amount
_______________________________________________________________________________________________________________________ (kg)
Water at 16-21°C 87.5
20% Soluble spray-dried animal blood 25.0a
90% Soluble spray-dried animal blood 12.5a
74-p. m Wood flourb 11.0a
Pine oil or diesel oil defoamer: mix 3min or until smooth 1.5a
Water at 16-21°C: mix 2min or until smooth 200.0
Fresh hydrated lime (as a slurry in) 3.0
Water at 16-21°C: mix 1 min 6.0
Sodium silicate solution: mix 1 min 22.5c
45-50% Solids low to intermediate advancement PF resin: mix 3min 13.5d
aNormally dry-blended for easier handling and dust control. b0.074mm (200 mesh) and finer. c8.90% Na2O, 28.70% SiO2, 41° Baume. dGeorgia-Pacific 3195, Borden Cascophen 335-1, Neste CB 118.
Amount
_________________________________________________________________________________________________________________________ (kg)
Water at 16-21°C 250.0
74-p. m Nutshell floura 75.0
Winter wheat flour 25.0
90% Soluble spray-dried animal blood 17.5
Diesel oil defoamer: mix 5 min or until smooth 2.5
50% Sodium hydroxide solution: mix 2min 28.0
Granular sodium carbonate: mix 15 min 10.5
43% Solids highly advanced PF resin: mix 5min while cooling the glue at 21-27°C 610.0b a0.074mm (200 mesh) and finer.
bGeorgia-Pacific 5763, Borden Cascophen 318-G, Dynea CB 303.
Table 13 Foamable Glue: Ingredients and Mixing Procedure
Amount
_________________________________________________________________________________________________________________________ (kg)
Water at 16-21°C 170
Industrial wheat flour 50
80% Soluble spray-dried animal blood: mix 7 min 20
PF plywood resin 110a
50% Sodium hydroxide solution: mix 15 min 12
PF plywood resin 275a
50% Sodium hydroxide solution: mix 2 min 5
Surfactant: mix 2 min or until smooth 1b
a43% solids phenolic resin; Borden Cascophen 3136, Dynea CB 305, Georgia-Pacific 4922. bEmersol or equivalent.
1.0 to 0.2 with very fine air bubbles. The low-density adhesive foam is then extruded onto passing veneer surfaces, which are assembled and hot pressed to produce exterior grades of plywood. (Recycled glue is deformed and recirculated.) The primary advantage of this kind of adhesive is lowered cost: for example, savings up to 25% over that of conventionally applied phenolic adhesives. A typical foamable glue mix is described in Table 13.
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