Casein adhesives

The adhesives (qv) used to form tube seams and bag bottoms include unborated dextrin, borated dextrin, casein, latex—casein, latex, poly(vinyl acetate), vinyl acetate copolymers, and hot-melt materials (10,27). Dextrin and casein adhesives are more commonly used in the production of grocery sacks vinyl acetate-type adhesives are commonly used in ah paper multiwah bags. The hot-melt adhesives are typicahy used to tack the phes of the multiwah bag together and to form the seam and bottom joints when polymer film phes or coated paper phes are used in bag constmction. 

Old nat. adhesives old (historic) natural adhesives, e.g. starch, glutin, casein adhesives. 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

Some beer bottle manufacturers have added poly(vinyl alcohol) to the adhesive to ensure resistance to iced water yet retain washability in the bottling operation. Others have used the starch paste to extend the more water-resistant casein adhesives (0). Newer adhesives are being developed based on double treatments of starches such as hydroxyalkyl ethers of oxidized starch, blending these products with other specified polymers (12,13) or adding synthetic resins... 

There is archeological evidence to indicate that early Egyptians used casein adhesives 5,000 years ago (i). Caseins have been used in Germany since about 1880 and in the United States since around 1900 (2). Impetus for the use of blood and caseins in wood gluing was generated by their extensive use in airplane construction during World War I (i-3). This led to broader commercial... 

Despite the many consumer and wood gluing uses mentioned here, an estimated 75% of casein production went into paper coatings until World War II (4). Casein use for adhesives reached its peak in 1973, at about 121 million dry pounds (5). Today, very little casein glue is used by household consumers, paper coaters, and plywood manufacturers. In 1986, nearly all U.S.-casein adhesive production was used by the door manufacturing industry, where the total volume was less than 10 million pounds. 

Casein adhesives experienced similar problems. Once the industry recognized that they were not waterproof, as was originally believed, they were rapidly replaced by resorcinols in most structural, cold-set applications where pressure was easily applied. Crosslinking polyvinyl acetates became preferable in some nonstructural, cold-set applications. Cheaper PF resins took over those exterior applications that allowed the use of heat and pressure. UF resins took over many interior applications on the basis of superior costs and mold resistance. Although the basic raw material cost is not a complete picture of the costs of its adhesive derivatives, it is a fairly good index. Table III shows how casein and blood compare with their competition at the present time. Although the exact prices of these materials fluctuate considerably, the approximate order of their costs has not changed much in the last 15 years. The materials are listed in order of cost. 

The casein adhesives developed for paper labels have proven to be readily soluble when the glass bottles are washed at defined pH levels. This has shortened the washing procedure and the labels have been able to comply with all further... 

Another possibility for adhesives to be classified is the differentiation between organic compounds of natural products, so-called natural adhesives, and products resulting from targeted chemical reactions, so-called synthetic adhesives. Many substances are known from daily life, which show a natural tack, for example, tree resins, plant juices, waxes, proteins, gelatine, casein, starch. In comparison to synthetically produced adhesives they are heavily lagging behind in terms of quantity, however, they partly show excellent properties in special applications, such as casein adhesives for bottle labelling. 

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). 

Casein adhesives are based on milk protein. They are used for labeling reflllable beer bottles because they resist cold water immersion but are readily removed in an alkaline wash when the bottles are returned. Another use is as an ingredient in adhesives for laminating aluminum foil to paper. 

In a totally different area of application, casein adhesives for paper sizing, chipboard laminating, and label gluing are more nearly casein solutions [59,60]. They are simple dispersions with ammonia or borax at moderate pH and low viscosity. They are frequently combined with latexes or soluble rosin derivatives for special performance improvements [59]. 

R. J. Lodge, Casein adhesives, Modem Packaging—Encyclopedia Issue (1959). 

UF, urea-formaldehyde resin MUF, melamine fortified UF resin MF/MUF, melamine and melamine-urea resins (MF resins are only used mixed/coreacted with UF resins MUPF, melamine-urea-phenol-formaldehyde resin PF/PUF, phenol and phenol-urea-formaldehyde resin (P)RF, resoreinol-(phenol-)formaldehyde resin PMDI, polymeric methylenediisocyanate PVAc, polyvinylacetate adhesive old nat.adhesives, old (historic) natural adhesives (e.g., starch, glutin, casein adhesives) nat.adhesives, natural adhesives (e.g., tannins, lignins, carbohydrates) inorg.adhesives, inorganic adhesives (e.g., cement, gypsum) activation activation constituents of wood to function as adhesives (i.e., lignin). 

Polyvinyl acetate Styrene/PVP copolymer adhesive, wood door Ammonium caseinate adhesive, wooden doors Calcium caseinate adhesive/sealant mfg. 

E. Sauer, Tierische Leime und Gelatine, Springer-Verlag, Berlin, 1958. This describes the technology of skin-based and bone-based glues, and also casein adhesives. 

Dry-mixed casein adhesives are simply mixed with water before use. They are used at room temperature and set by the loss of water through a porous substrate and by a certain degree of chemical conversion. Mixed casein adhesives have a finite pot life. They are commonly used for paper labels, woodworking, and other interior applications. They cannot be used outdoors, although they are resistant to dry heat up to 70°C. Resistance to organic solvents is generally good. 

The major suppliers of casein adhesives include American Casein Co., National Casein Co., and Ultra Additives, Inc. 

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