Question

Give the raw materials, process description,flow sheet, engineering problems faced in the manufacture of GLUE

Answer 1

Solution:

Raw materials: Glue manufacturers obtain bones and tissues of animals from slaughterhouses, tanneries, and meat packing companies; it is no coincidence that the world's largest glue manufacturer is the dairy called Borden Company. The animal remains that are the raw materials for glue may include ears, tails, scraps of hide or skin, scrapings from the fleshy sides of hides, tendons, bones, and feet. Similarly, manufacturers of fish glue obtain bones, heads, scales, and skins of fish from canneries and other processing plant.

Process description:

• With only minor variations, the same basic processes are used to make bone glue, hide or skin glue, and fish glue. The hides and other scraps are washed so that dirt is removed, and they are soaked to soften them. This material is called stock, and it is passed through a series of water baths in which more and more lime is added to make the hides and skins swell and break them down. The swollen hides are rinsed in a large washing machine to remove the lime. The last traces of lime are eliminated by treating the stock with weak acids like acetic or hydrochloric acid. Finally, the stock is cooked either by boiling, it in open tanks or cooking it under pressure in autoclaves.
• Cooking at the correct temperature and for the right length of time breaks down the collagen and converts it into glue. If the temperature or timing is off, the quality of the glue will be ruined. Large steam coils in the open tanks heat the water and product to 160°F (70°C). Three or four treatments with clean water are performed at increasing temperatures (or pressures if a pressurized system is used). The resulting liquid, called "glue liquor" is extracted and reheated again to thicken the glue.
• When cooled, this material looks like jelly and is solid; although it looks like the kind of gelatin used in food, it contains impurities. To remove the impurities and make the glue clear, chemicals like alum or acid followed by egg albumin may be added. These chemicals cause the impurities to precipitate, or fall out, of the glue. Mechanical methods can also be used to clean the glue. These include passing the glue through a series of mechanical filters or through paper filters or ground bone called bone char.
• Different additives are mixed with the glue liquor to make brown, clear, or white glue. Sulfurous acid, phosphoric acid, or alum are among these additives. Zinc oxide is added to produce white "school glue."
• To this point, the glue is a weak, runny liquid. It is made more concentrated in vacuum evaporators and dried in one of several methods. The glue can be chilled into either sheets or blocks then suspended on nets to dry and become still more concentrated. The glue can also be dropped as beads or "pearls" into a non-water bearing liquor that further dries the concentrated beads. The pearls, blocks, or sheets are then mixed to the right consistency and pumped into bottles or jars for sale.

Process flow sheet :

Engineering problem :

1.  Volatility in raw materials

2. Raw material supply

3. An important challenge facing adhesive manufacturers and users is the replacement of adhesive systems based on organic solvents with systems based on water.

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