Adhesives plant resin formulations

Plant Resin Formulations, Sometimes compounded with shellac, as in DeKhotinsky cement, these compounds have long been used as hot-melt glues. Likewise, waxes of plant and animal origin have also been used as hot-melt adhesives (22). They all should be reversible by application of heat, possibly in conjunction with solvent action in the more diflScult cases. 

Where does the secret of technical industrial success with tannin adhesives lie It varies for certain adhesives, it is in the formulation of the adhesives only for others, it lies in the application conditions and techniques only for most, success requires a good balance of both. While excellent correspondence between laboratory and plant results can often be obtained in adhesives that depend for success on resin formulation, this is usually not the case when success is more dependent on application techniques and conditions (Table I). 

Isophorone is a solvent for a large number of natural and synthetic polymers, resins, waxes, fats, and oils. Specifically, it is used as a solvent for concentrated vinyl chloride/acetate-based coating systems for metal cans, other metal paints, nitrocellulose finishes, printing inks for plastics, some herbicide and pesticide formulations, and adhesives for plastics, poly(vinyl) chloride and polystyrene materials (Papa and Sherman 1981). Isophorone also is an intermediate in the synthesis of 3, 5-xylenol, 3, 3, 5-trimethylcyclohexanol (Papa and Sherman 1981), and plant growth retardants (Haruta et al. 1974). Of the total production, 45-65% is used in vinyl coatings and inks, 15-25% in agricultural formulations, 15-30% in miscellaneous uses and exports, and 10% as a chemical intermediate (CMA 1981). 

There are more than 35 producers all over the world an exhaustive list was provided in a recent review [82]. World consumption of hydrocarbon resins has been estimated —750 kt in 1994 which corresponds to an increase of 7.8% with respect to 1993. About 65% of the resins were used in adhesive formulations. Production was 350 kt for aromatic (C9 + IC) resins, 274 kt for aliphatic (C5 + DCPD), and 128 kt for the more rapidly developing water-white pure monomer resins, which corresponds on average to about 80% of world plant capacities [95]. Production of polyterpene resins appears limited to 25-30 kt per year. 

The biochemical reaction catalyzed by epoxygenase in plants combines the common oilseed fatty acids, linoleic or linolenic acids, with O2, forming only H2O and epoxy fatty acids as products (CO2 and H2O are utilized to make linoleic or linolenic acids). A considerable market currently exists for epoxy fatty acids, particularly for resins, epoxy coatings, and plasticizers. The U.S. plasticizer market is estimated to be about 2 billion pounds per year (Hammond 1992). Presently, most of this is derived from petroleum. In addition, there is industrial interest in use of epoxy fatty acids in durable paints, resins, adhesives, insecticides and insect repellants, crop oil concentrates, and the formulation of carriers for slow-release pesticides and herbicides (Perdue 1989, Ayorinde et al. 1993). Also, epoxy fatty acids can readily and economically be converted to hydroxy and dihydroxy fatty acids and their derivatives, which are useful starting materials for the production of plastics as well as for detergents, lubricants, and lubricant additives. Such renewable derived lubricant and lubricant additives should facilitate use of plant/biomass-derived fuels. Examples of plastics that can be produced from hydroxy fatty acids are polyurethanes and polyesters (Weber et al. 1994). As commercial oilseeds are developed that accumulate epoxy fatty acids in the seed oil, it is likely that other valuable products would be developed to use this as an industrial chemical feedstock in the future. 

Adhesives of the aminoplastic (see Step polymerization) and phenol formaldehyde (see Phenolic adhesives single-stage resoles and Phenolic adhesives two-stage novolacs) types are most widely used. Although basically similar, an adhesive for plywood manufacture will require a different formulation to one for particle board, or medium-density fibre board (MDF) since methods of application and processing differ. Thus, in plywood, large sheets of veneer must be uniformly coated with adhesive, usually by a roller or curtain coater in particle board, chips or wafers must be coated with very fine adhesive droplets, while small bundles of wet fibres must be sprayed with adhesive in the manufacture of MDF. Hence, formulation and production of resins has become a mixture of art and science, with resin manufacturers able to produce resins tailored for use in a particular board-manufacturing plant, or with a particular species of timber. 

Several large chemical companies manufacture a full line of amino resins. This may require as many as 75 different formulations to meet all application needs. Large particleboard manufacturers may prepare a simple urea-formaldehyde adhesive resin at the plant. 

Tackifiers are used in formulating rubber based on adhesives to improve the tack property. Tackifiers are low molecular weight compounds with high Tg. There are two classes of tackifiers the rosin derivatives and the hydrocarbon resins. The rosin derivatives include the rosins, modified rosins, and rosin ester. The hydrocarbon resins consist of low molecular weight polymers derived from petroleum, coal, and plants. The miscibUity between tackifiers and the adhesives is important to choose a tackifier. The viscoelastic property of adhesives can be modified by blending of a miscible tackifier. 

With regard to starch adhesives, the bulk of development is expected to come from thermoplastic starches that can be used as hot-melt adhesives or transformed into waterborne dispersions. For other plant derivatives such as soy and castor oil, a significant development effort is taking place in the manufacture of polyols for use primarily in polyurethane adhesives and sealants. Similarly, derived waxes are also being used as plasticizers in hot-melt adhesive formulations. For natural adhesives that are based on cellulose derivatives, tree resins and their by-products, as well as natural rubber, low growth rates are envisaged, whereas the market for advanced bio-based adhesives is stiU in the early stages of development. 

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