Лако-красочные материалы — производство

Reference was made to the historical use of collagen glues derived from the gelatin extracts of animal bones and hides. This does not properly indicate the true importance to the wood industry of these materials. From ancient times to the present, animal glues have in fact remained one of the primary assembly adhesives for wooden […]

Casein glues for wood pass through an early thick-consistency stage that requires fairly strong agitation to reduce them to a uniform and lump-free state. The mixer should be equipped for sidewall scraping to work thickened glue continuously back into the stirred composition. Counterrotating paddle mixers and bread dough mixers have proved ideal for this purpose. […]

For adhesive uses, the particle size of ground casein is normally controlled within the range of about 250-500 pm [56]. Particles coarser than 500 pm (30 mesh) may not dissolve and disperse completely during glue preparation. Those much finer than 250 11 pm (60 mesh) tend to form immediate lumps on wetting, even if oiled. […]

A. Raw Material Source and Preparation As with blood, the adhesive qualities of casein curd from milk were recognized in relatively ancient times. Mixed with a simple alkali such as lime, casein protein became an important adhesive for furniture and paint pigments and the preferred sizing agent for the canvas of Renaissance paintings [6,55]. Medieval […]

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: […]

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 […]

Since soybean-blood blend glues were covered in the preceding section, in this portion of the chapter we deal only with all-blood adhesive compositions. A. Raw Material Source and Preparation Historically, animal blood could be used for adhesives only in reasonably fresh liquid form. These glues performed well on wood. However, the very rapid spoilage rate […]

Blends of soybean flour with ground and screened casein also yield a very useful series of protein adhesives, in this case, mostly cured cold [38]. While alkaline-dispersed casein yields strong, water-resistant cold-cured bonds in wood, its sticky dispersed consistency does not permit the rapid water loss needed for quick-clamping procedures. By combining it with an […]

As mentioned earlier, the single largest commercial use of soybean flour in wood glues during the recent past has been as a blend with other adhesive proteins, mainly blood and casein, for bonding interior-grade plywood, doors, and millwork. These blended formula­tions exploit several unique properties of the soybean glues themselves and incorporate useful adhesive characteristics […]

Soybean glues are very easy to mix, provided that they are wetted with plain water as a first step. (If any form of alkali is present in the first mixing water, the dry soybean flour will form permanent lumps.) As with all protein glues, the first mix is kept thick to break down any lumps […]