Adhesives starch esters

Throughout the 1990s a large portion of the research and development effort for hot melt adhesives focused on developing adhesives that are either environmentally friendly or functional [69,81,82]. Environmentally friendly attributes include biodegradability, water dispersibility (repulpability), renewability, and water releasability. Biodegradable adhesives have been developed based on starch esters [83-86] and polyesters such as poly (hydroxy butyrate/hydroxy valerate) [87], poly(lactide) [88-91], and poly(hydroxy ether esters) [92-94]. All but the... 

Starch, often in its degraded form dextrin, and starch esters have long found application in general emulsion and dispersion technology, mainly in adhesives, construction materials or in pharmaceuticals for example, as aqueous coating material for controlled-release products [106]. 

Most types of Hot melt adhesives used in the mannfacture of laminates and in rapid Packaging industry applications are mineral oil-derived, hydrophobic and essentially non-dispersible, so they cannot be considered as renewable. However, some basic polymers have been prepared over the last decade from vegetable sources, which are renewable, and are adhesive, although these properties have limitations. These include poly(hydro-xybutyrate/hydroxyvalerate) (PHBV), poly(lactide) (which has poor thermal stability), and starch esters. Adhesives based on sulphonated polyesters with polar petroleum waxes have improved adhesion and adequate water dispersibility. In general, however, the perfect adhesive from renewable resources with satisfactory adhesion properties remains to be discovered. 

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... 

Epichlorohydrin is usually prepared from propene and is mainly used in the manufacture of glycerol and epoxy resins. It is also used in the manufacture of elastomers, glycidyl ethers, cross-linked food starch, surfactants, plasticizers, dyestuffs, pharmaceutical products, oil emulsifiers, lubricants, and adhesives as a solvent for resins, gums, cellulose, esters, paints, and lacquers and as a stabilizer in chlorine-containing substances such as rubber, pesticide formulations, and solvents. 

Chlorinated and/or oxidized starches crosslinked with glyoxal were used to produce a high-strength size for paper.573 Coating adhesives were also prepared by crosslinking glycidyl esters.1385 In addition, esters of starch with inorganic acids (such as starch phosphates) were crosslinked with various aliphatic and aromatic aldehydes in the presence of urea, melamine and similar compounds.1322... 

Mixed esters were proposed for use as petrochemical dispersants2070 and cardboard adhesives.2071 They were also compounded with starch and borax for use in processing corrugated board.2072... 

Seycofilm . [S del-WooUey] Drypoly-ester size f[Pg.333]

Vinyl esters Resorcinol N-methylol acrylamide Woodworking adhesives Mudge et al. V.S. Pat., 5,434,216, 1995 National Starch... 

Useful film-forming resin adhesives include polyvinyl esters and ethers and their copolymers and interpolymers with ethylene and vinyl monomers, acrylic resins and their copolymers, polyvinyl alcohol, water dispersion of polyolefin resins, polystyrene copolymers such as polystyrene butadiene, polyamide resins, natural rubber dispersions, and natural and modified carbohydrates (starch or carboxycellulose). Particularly preferred for use are aqueous dispersions of polyvinyl acetate and vinyl acetate-ethylene copolymers. 

Fillers (calcium carbonate, calcium sulfate, aluminum oxide, bentonites, wood flour) increase the solid content of the dispersion, and they are added up to 50%, based on PVAc. The purpose of their addition is the reduction of the penetration depth, a thixotropic behavior of the adhesive, gap filling properties, and the reduction of the adhesive costs. Disadvantages can be the increase of the white point and possibly the more marked tool wear rate due to greater hardness of the adhesive. Other components in PVAc formulations are defoamers, stabilizers, filler dispersants, preservatives, thickeners (hydro-xyethylcellulose, carboxymethylcellulose), poly(vinyl alcohols), starch, wetting agents, tackifiers, solvents (alcohols, ketones, esters), flame retardants, and others. 

Uses Alkyd resins paints dynamite ester gums perfumery lubricants softener bacteriostat penetrant emollient antifreeze prod, of antibiotics plasticizer for regenerated cellulose film, sodium silicate foundry resins solvent (printing inks) humectant (tobacco, starch adhesives, textile sizes) solvent, humectant, plasticizer, bodying agent for foods, food pkg., cosmetics plasticizer, solvent, solubilizer, preservative for pharmaceuticals PU crosslinker heat costabilizer (PVC) sweetener preservative plasticizer in food-contact coatings Use Level 0.2-65.7% (topicals), 1-50% (liq. orals), 50% (parenterals), 7-10% (dentifrices), 0.5-3.0% (ophthalmics)... 

Starches are modified chemically in various ways. Some acetate and phosphate esters are produced commercially, as well as hydroxyalkyl and tertiary aminoalkyl ethers. Both unmodified and modified starches are used principally in paper making, paper coating, paper adhesives, textile sizes, and as food thickeners. There are many reports in the literature on graft copolymers of starch. The work is often conducted is search of biodegradable materials for packaging and agricultural mulches. Most chemical modifications of starch parallel those of cellulose. 

The development and use of materials from renewable sources is not a new concept. Besides providing food, feed, clothes, shelter, and energy, biomass has been employed since ancient times to extract valuable products such as medicinal drugs, flavors, and fragrances. With the development of civilization of human society, in the nineteenth century various biomass resources were employed for the large-scale industrial production of chemicals and durable materials, such as cellulose esters (nitrate and acetate), oxidized linseed oil (linoleum), vulcanized rubber, adhesives from starches, and so on. However, the widespread use of such renewable materials diminished in the twentieth century since the development of fossil fuel derivatives, leading to the polymer renaissance. Today commodity polymers such as polyolefins are ubiquitous in our societies because they represent the optimal choice based on several factors, including monomer cost and... 

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