Adhesives starch-based

In the manufacture of paper, starch-based adhesives are used either to strengthen the paper base or for coating the surface of the paper. Raw starch is unsuitable for either purpose. To achieve sufficient adhesive power with raw starch would require the application of a solution that was far too thick for practical use. Instead, chemically modified starch, with a much lower viscosity in solution, is used. As an economical alternative to modifying the starch with aggressive oxidizing agents, the starch can be treated with enzymes ( df-amylases) to obtain the same thinning effect... 

Natural-product-based structural adhesives include protein-based adhesives, starch-based adhesives, and cellulosics. 

Turbett, G. T., Barnett, T. C., Dillon, E. K., and Sellner, L. N. 1996. Single-tube protocol for the extraction of DNA or RNA from paraffin-embedded tissues using a starch-based adhesive. Biotechniques 20 846-853. 

Although, as previously pointed out, the many synthetic adhesives developed during the past two decades are replacing the natural adhesives to a large extent in a number of areas, starch-based adhesives are almost impossible to remove from some markets because of specific properties and cost savings. Some of those markets are discussed below. 

Starch is still quite widely used as an adhesive in our modern, high tech world. Its adhesive properties are developed differently for different products, and starch-based adhesive is used in a large variety of applications. From the standpoint of its being a renewable resource, a reliable performer, and a low-cost raw material, starch would seem to be an adhesive ingredient on the market for a long time into the future. 

Poly(vinyl alcohol) is utilized as a component of starch-based adhesives.11121114 Other patents report the use of partially oxidized starch,1115 dextrins,1116 dextrins and urea,1117 borax,1118 boric acid,1119 and vinyl methyl ether-maleic acid copolymers.1120 Other patents indicate the use of poly (vinyl alcohol) with partially hydrolyzed poly(vinyl acetate),1121 nonhy-drolyzed poly(vinyl acetate),1122 and poly(vinyl chloride).1123 A few patents have reported such poly acrylic additives as poly (acrylic acid)1124 and its salts,1125 poly(acrylamide),1126 1127 A-methylacrylamide or poly(A-acryl-amide),1128 and polyethyleneimine.1129 Polystyrene has also been used,1130 as well as more complex copolymers such as a maleic acid monobutyl ester-methyl vinyl ether copolymer, together with dextrin and polyacrylamide),1131 carboxylated ethyl acrylate-styrene zinc salt copolymer,1132 ethylene-methyl acrylate-vinyl acetate copolymer,1133 vinyl acetate-vinyl pyr-rolidone copolymer,1134 and ethylene-vinyl acetate copolymer.1135 Some adhesives are compounded with SBR latex1136 1138 and phenol-formaldehyde resins.1139... 

Hexahydro-1,3,5-triethyl-s-triazine. Industrial preservative, prevents bacterial action in cutting oils, synthetic rubber latex, starch based adhesives, latex paint and aqueous slurries. It is soluble in acetone, ethyl alcohol, ether and water, moderately soluble in hydrocarbon solvents. 

W. Jarowenko, "Starch based adhesives," in I. Skeist ed.. Handbook of Adhesives, 2nd Edition, Van Nostrand Reinhold Co, New York, Chapter 12, pp. 192-211,1977. 

Jarowenko, W., Starch-based adhesives, in Handbook of Adhesives, 2nd ed., Skeist, I., Ed., Van Nostrand Reinhold,... 

Borax (sodium tetraborate) in the presence of small amounts of sodium hydroxide is the most widely used additive to starch-based adhesives. It is commonly used in dextrin adhesives, where it increases the viscosity and acts as a tackifier and viscosity stabilizer. These effects are particularly important in machine application of adhesive to substrate. When used in adhesives, borax is often added in amounts up to 10% based on dry starch before the starch is cooked. Enough sodium hydroxide is added to convert the borax to sodium metaborate, which is the active boron species in thickening. The metaborate is able to hook two starch molecules together, forming a complex (Fig. 5) [10]. If additional sodium hydroxide is added, the complex will dissociate the viscosity of the suspension will begin to decrease with increasing sodium hydroxide [11]. 

Starch-based adhesives used in any application that requires water resistance must contain additives that resist water. Commonly used additives of this type are urea-formaldehyde, melamine formaldehyde, and resorcinol-formaldehyde precondensates, poly(vinyl alcohol), and poly(vinyl acetate). The greatest water resistance is imparted by the formaldehyde-based precondensates poly(vinyl alcohol) and poly(vinyl acetate) are used for adhesives that are resistant to cold water but can dissolve in hot water. 

As mentioned previously, one problem encountered in starch-based adhesives is retro-gradation. Colloid stabilizers such as soaps and sodium chloride are used to retard this tendency. Borax, sodium hydroxide, and several common plasticizers also perform this... 

Uses Crosslinking agent for carboxylated SBR latex, carbor methyl cellulose, PVA, and other water-sol. polymers water resist, aid for starch-based adhesives and coalings food-contact paper/paperboard Regulatory FDA 21 CFR 176.170,176.180 Properties Pale amber liq. water-soL sp.gr. 1.03 vise. 50 cps f.p. -3.9 C pH 4.7 cationic 12.5% total solids Storage 100 days shelf life below 32 C Polycup 1884 [Hercules]... 

Schonbohm, D., Blither, A., Banik, G. (2004). Enzymes in solvent conditioned poultices for the removal of starch-based adhesives from iron gall ink corroded manuscripts. Restaurator, 25(4), 267-281. 

Wattle tannins have been used as fortifiers in starch-based adhesives for corrugated carton manufacture in order to improve the moisture resistance of boxes used in shipment of fruit, for example (144, 217). Addition of 4% wattle tannin based on resin solids substantially improved the durability of these cartons. Wattle tannin urethane-based varnishes with excellent durability have been developed by Saayman (214). Other adhesive applications based on reactions of wattle tannins with isocyanates have been developed for specialty applications such as the bonding of aluminum (181). 

Mixed Glues. Starches and dextrins also are used in combination with other raw materials in adhesives. For example, the resistance to water of starch-based adhesives can be improved by the addition of melamine-formaldehyde or urea-formaldehyde resins. Mixtures of starch-based adhesives or dextrin-based adhesives with synthetic resin dispersions are also used. 

Lamination of Paper and Board. Adhesives based on starch, dextrin, glutin and poly(vinyl alcohol), and also emulsion adhesives, mainly polyfvinyl acetate), are used for the lamination of paper and board. Only when high initial tack and a lay-flat effect are required are hot glues based on glutin still in use. Starch-based adhesives modified with silicate, casein-stabilized copolymer dispersions, and rubber latices are used in the lamination of paper to aluminum foils. Modified polyacrylate solutions and reactive polyurethane adhesives are used mainly for paper-to-plastic lamination. 

Bags, Sacks, Pouches, and Boxes. Starch-based adhesives and also emulsions of poly(vinyl acetate) homopolymers and copolymers or mixtures thereof are used in the manufacture of bags, pouches, and carrier bags, depending upon the type of materials (e.g., paper, plastic films, etc.), surface treatment, and the speed of the machine. Machine design factors necessitate the use of pastelike starch-based or emulsion-based adhesives for the bottom gluing of block-bottom or cross-bottom bags. 

In making paper sacks, starch-based adhesives normally are used for the longitudinal seam and also for the bottom and bottom patching. For paper sacks with PE free film or inliner, emulsion-based synthetic resin adhesives are used. For the longitudinal seam of the inliner, hot-melt adhesives are used. 

Modifier for starch-based adhesives United States 3,939,108 1976 National Starch [Pg.578]

Other initiatives being tested are substitution of petroleum-based resins by starch-based adhesives, using polylactides (derived from com) as a renewable input for the production of packaging material, and replacing oil with eco-friendly and less expensive sugar cane. Finally, note that the use of foaming adhesive can cut the amount of adhesive needed, as it has low density. 

Binding and cover attachments use hot melts, emulsion and animal glues. Ethylene vinyl acetate (EVA) and block copolymers are used for these operations. Case making normally uses animal glues to bond the cover materials to the cover boards. Casing in, the attachment of the book block end papers to die eover, involves the use of emulsions or starch based adhesives. Reinforcement involves the attaehment of paper or cheesecloth to the spine of the book. Hot melt adhesives are used for diis operation. 

Starch-based adhesives degrade in humid service environments. 

---