Casein glue from milk

Casein adhesive glue Adhesive on animal basis, made of acid casein accruing from milk processing. Application as wood adhesive and in the packaging industry (label adhesive). 

By-Products From Milk. Milk is a source for numerous by-products resulting from the separation or alteration of the components. These components may be used in other so-called nondairy manufactured foods, dietary foods, pharmaceuticals (qv), and as a feedstock for numerous industries, such as casein for glue. 

In contrast to coatings, which must adhere to one surface only, adhesives are used to join two surfaces together. Resinous adhesives were used by the Egyptians at least 6000 years ago for bonding ceramic vessels. Other adhesives, such as casein from milk, starch, sugar, and glues from animals and fish, were first used at least 3500 years ago. 

Animal (Colla) Impure gelatinous mattet of animal origin, most commonly bone glue made from hides and bones, casein glue made from skimmed milk, and fish glue made from fish skins [Hackh s... 

Commercial casein is usually manufactured from skim milk by precipitating the casein through acidification or rennet coagulation. Casein exists in milk as a calcium caseinate-calcium phosphate complex. When acid is added, the complex is dissociated, and at pH 4.6, the isoelectric point of casein, maximum precipitation occurs. Relatively little commercial casein is produced in the United States, but imports amounted to well over 150 million lb in 1981 (USDA 1981C). Casein is widely used in food products as a protein supplement. Industrial uses include paper coatings, glues, plastics and artificial fibers. Casein is typed according to the process used to precipitate it from milk, such as hydrochloric acid casein, sulfuric acid casein, lactic acid casein, coprecipitated casein, rennet casein, and low-viscosity casein. Differences... 

Animal glues are usually made from bones and hide. Casein from milk and fish glues are also of animal origin. 

Water-Soluble Proteins. Historically, several water-soluble plant and animal proteins have been used as adhesives, both industrially and in conservation work. Currently, only the milk-based casein products are in significant industrial use. Casein glues have also been used in conservation work, but formulations designed for high water resistance could be difficult to reverse. Plant proteins, especially those from legumes such as soybeans and peanuts, have been used industrially, some until fairly recently. Presumably at least some forms of plant protein glues would be reversible enough to be of interest to conservators. 

In the Middle Ages, the first glue-boiling plants came into being and produced protein glues from animal raw materials (glutin from hides and bones, blood albumin, casein from milk) or starch paste from plants. 

About 1750, the first glue patent was issued in Britain for a fish glue. Patents were then rapidly issued for adhesives using natural rubber, animal bones, fish, starch, and milk protein (casein). By 1900, the United States had a number of factories producing glue from the aforementioned bases. 

Casein glue is made from a protein isolated from milk. The extraction process creates an adhesive that is waterproof. Its first use was in bonding the seam of cigarette paper. It provides a fast setting bond that requires very little adhesive 1 g of adhesive can bond 2000 cigarettes. 

Animal glue is a complex colloidal mixture of proteins. The related gelatins are also complex heterogeneous mixtures of proteins. They are strongly hydrophilic and rich in the amino acids glycine, proline, lysine, hydroxyproline and hydroxylysine. Casein is a phosphoprotein obtained from the milk of mammals. 

The proteinaceous binders are one of the main constituents of the wide range of organic materials and are a central component of the artist s palette. In the technique referred to as tempera, artists commonly used proteinaceous binders derived from egg, milk or casein, and collagen glues derived from animal skins or bones. These can be used independently, mixed together, or in a more complex mixture with siccative oils (as in the tempera grassa technique) or plant gums. 

Probably because of the ease with which casein can be produced from skim milk, essentially free of lipids, lactose and salts, by rennet or isoelectric coagulation and washing of the curd, acid and rennet caseins have been produced commercially since the beginning of this century. However, until relatively recently, they were used for industrial applications, e.g. in glues. 

As in the processing of vegetable oils the extraction of fats and oils from animal sources can be regarded as a sequence of unit operations (Figure 9.1.10). In modern economies milk and butter are predominantly used as dairy products (besides e.g. casein paints and glues) whereas tallow and marine oils are used for food as well as for industrial purposes. 

Processes and products developed to produce industrial materials from renewable resources have been too numerous to record here. For competitive reasons — supply of raw materials and technical and economic considerations — some of the products have varied widely in industrial use. Major U.S. industrial consumption of renewable resources have recently included oils and fats (animal and vegetable) industrial alcohol (wheat, corn, grain sorghum) fibers (cotton lint, flax, hides and skins) paper (forest products) isolated proteins (milk casein, animal glues, soybean, corn) turpentine and rosin (naval stores) and other chemicals (monosodiiim glutamate--wheat starch and dextrin—corn lactose—milk molasses and pulp residues --sugarcane and beet tannin lecithin pectin furfural). 

Casein, like gelatin and blood albumen, is essentially a protein. It is obtained as a precipitate from skimmed milk, which bas been treated with sulfuric, hydrochloric or lactic acid. The glue is prepared by blending the preeipitated casein (which also contains several milk-product impurities) and alkaline salts (generally of calcium, sodium or boron) in an aqueous medium. To set - i.e. to achieve a solid state - the adhesive solution pH is adjusted to between 9 and 13. 

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