Phenol bark resins

Thermogravimetric analysis in conjunction with DSC has been used to measure Tg in phenol bark resins [3]. DTA has been used to measure Tg in bis(trichlorophenolate) di(pyridine) nickel(II) and bis(tribromophenolate) di(pyridine) nickel(II) complexes [12], PS [13], and various other polymers [14]. 

Tg measurements have been performed on many other polymers and copolymers including phenol bark resins [71], PS [72-74], p-nitrobenzene substituted polymethacrylates [75], PC [76], polyimines [77], polyurethanes (PU) [78], Novolac resins [71], polyisoprene, polybutadiene, polychloroprene, nitrile rubber, ethylene-propylene-diene terpolymer and butyl rubber [79], bisphenol-A epoxy diacrylate-trimethylolpropane triacrylate [80], mono and dipolyphosphazenes [81], polyethylene glycol-polylactic acid entrapment polymers [82], polyether nitrile copolymers [83], polyacrylate-polyoxyethylene grafts [84], Novolak type thermosets [71], polyester carbonates [85], polyethylene naphthalene, 2,6, dicarboxylate [86], PET-polyethylene 2,6-naphthalone carboxylate blends [87], a-phenyl substituted aromatic-aliphatic polyamides [88], sodium acrylate-methyl methacrylate multiblock copolymers [89], telechelic sulfonate polyester ionomers [90], aromatic polyamides [91], polyimides [91], 4,4"-bis(4-oxyphenoxy)benzophenone diglycidyl ether - 3,4 epoxycyclohexyl methyl 3,4 epoxy cyclohexane carboxylate blends [92], PET [93], polyhydroxybutyrate [94], polyetherimides [95], macrocyclic aromatic disulfide oligomers [96], acrylics [97], PU urea elastomers [97], glass reinforced epoxy resin composites [98], PVOH [99], polymethyl methacrylate-N-phenyl maleimide, styrene copolymers [100], chiral... 

Currently, existing pilot plants in Canada, Netherlands, UK utilize mainly well defined non contaminated biomass fractions such as wood particles, saw dust, and bark. The performed investigations in this work should broaden the knowledge of the pyrolytic behaviour of various industrial biomass waste. This wilt facilitate the introduction of flash pyrolysis processes into existing industrial processes. Therefore, a new way of biomass exploitation will be demonstrated. In cooperation with several companies different biomass waste such as cocoa shell, wood waste, fibre sludge and panel boards with a high content of phenol-foimaldehyde resin were decomposed by flash pyrolysis into smaller molecules to use them for the production of energy and/or chemicals. 

The first attempts to use wattle tannins in particleboard adhesives (114, 170) followed reports by Dalton (50, 51) on the use of Pinus radiata bark extracts as substitutes for phenol-formaldehyde resins in plywood adhesives. Even though the molecular weight of wattle tannin is comparatively low (208), solutions of bark extracts at solids contents required for adhesives (40%-58%) exhibit excessively high viscosities. High-temperature alkaline treatments reduced their viscosity, and... 

Research directed to the use of bark extracts from various species of pines has continued despite the marked reduction in prices for petroleum in the late 1970s and early 1980s. A number of new plywood adhesive formulations based on extracts of Pinus radiata have been described recently. Weissmann and Ayla (253) used sulfonated tannin extracts at 40% solids and fortified these extracts with a phenol-formaldehyde resin (Kauresin 260 produced by BASF) at levels to 10% to 50% by weight of solids. Both paraformaldehyde and hexamethylenetetramine were examined as aldehyde sources. Exterior grade plywood bonds were obtained at 10% and 30% fortifying levels. 

Chen (46) used sodium hydroxide extracts from southern pine Pinus spp.) bark, peanut Arachis hypogea) hulls, and pecan Carya illinoensis) pith as 20% replacements for phenol-formaldehyde resins in plywood adhesives. Bond quality was highly dependent on veneer moisture content and assembly time. Exterior quality bonds (U.S. Product Standard PS-1-74) in southern pine plywood were obtained if the veneer moisture content was 7.0% with 60-minute assembly times. Phenol-formaldehyde resin replacements could be increased to 40% by peanut hull and pecan pith extracts when the extraction solutions containing 5% of sodium hydroxide were used (45). Southern pine veneer (0.32 cm) was spread at a rate of 41.5 to 42.5 g/lOOOcm of double glue line and the layups were stored in a... 

Hamada R, Ikeda S, Satake Y 1969 Utilization of wood bark of plywood adhesives. I. Effect of addition of bark of Acacia mollissima on the properties of phenol formaldehyde resin. Mokuzai Gakkaishi 15 165-170... 

Attempts have already been made to develop adhesive substitutes for phenol-formaldehyde resin from the bark extract of pine trees. Bark accounts for about 15% by weight of pine trees. The phenolics from bark extracts can be used as substitutes for phenols. The bark phenolics, having a molecular weight of about 1500, may be reacted with formaldehyde under mild conditions to obtain adhesives >. Another approach to the use of bark phenolics is to react the bark extract with low molecular weight methylol phenols. ... 

A series of studies were carried out aimed at investigating the practicability for industrial practice of using bark and agricultural residue components as substitutes for at least portions of phenol in phenol-formaldehyde resins. This research was designed both to study the opportunities for waste material utilization and to explore possible new sources of raw materials for resins and glue mixes. 

Section three contains six chapters dealing with the noncellu-losic components of plant life including tall oil, wood and gum rosins, lignan, bark extracts, tannin, wood flour, and rice hull flour for use in the preparation of composites, resins, adhesives, and fillers. Filler properties are described in some detail. Substitutes for phenol-formaldehyde resins are described as well as the generation of the industrially important trimellitic anhydride from natural sources. A problem in the rubber elasticity of gutta percha networks is discussed. 

More recently, a modification of the system described by Kreibich has been used extensively in industry with good success. Part A of the adhesive is again a standard phenol-resorcinol-formaldehyde (PRF) cold-setting adhesive, with powder hardener added at its standard pH. Part B can be either the same PRF adhesive with no hardener and the pH adjusted to 12, or a 50 to 55% tannin extract solution at a pH of 12-13, provided that the tannin is of the condensed or flavonoid type, such as mimosa, quebracho, or pine bark extract, with no hardener [118,135-137], The results obtained with these two systems are good and the resin not only has all the advantages desired but also the use of vegetable tannins and the halving of the resorcinol content makes the system considerably cheaper [118,135-137]. 

As indicated by the structures of these molecules, the A ring contains resorcinol phenolic hydroxyls, while the B ring contains the catechol or adjacent phenolic hydroxy groups, both of which would be expected to be highly reactive in resin formation. This high reactivity would also hold for the condensed tannins present in the bark extract, since they are polymeric flavonoids (14). 

The bark extract bonded particleboards met specifications requiring the inherent durability provided by phenolic adhesives. These products are used for floor decking for modular homes, specialized furniture uses, home siding, garage door panels and more recently, as a wall and roof sheathing and single layer floor decking in conventional home construction. Thus, phenol and phenol-resorcinol modified resins can be replaced by a low-cost bark product. This use of bark would be a profitable outlet for bark residues and could lead to virtual independence of the wood particleboard industry from the petrochemical industry. 

There is also the possibility that pollutants alter susceptibility of the plant to pathogens (36) or insect attack. Of the latter there is the decreased resistance of ponderosa pine to bark beetle attack caused by ambient oxidant exposure (37). The investigations of others with respect to the effects of fluoride on ponderosa pine indicated that although foliar injury was associated with increased resin exudation pressure, which could be interpreted as an increased capacity of the tree to overcome bark beetle attack, degree of insect infestation was not associated with amount of foliar injury (38). As more is known about pheromones, the botanical investigation of the secondary products of metabolism, such as terpenes and phenolics, may become more important in investigating the mode of action of pollutants in the entire plant. The switch to alternate pathways, while resulting in the same products, may reduce the intermediates needed in biosynthesis and thereby affect the plants resistance to disease or attractiveness to insects. 

Attempts to make adhesive formulations by direct reaction of formaldehyde or its equivalent resulted in products that were excessively viscous, and the working time was too short for commercial application (57). It was concluded that formaldehyde, although readily reactive with the tannin molecule, provided much too short linkages to connect the bulky tannin molecules. This problem was circumvented by the preparation of a polymethylolphenol reagent that, when put in solution with the bark extract, formed a combination that was stable for several weeks at room temperature. When heated, the polymethylolphenol and bark extract reacted rapidly to form an infusible resin. Commercial trials were made to produce exterior-grade Douglas-fir plywood. Widespread use of the extracts for this purpose, however, was inhibited by a drop in the price of phenol below what the bark extracts could be manufactured for. (The best extract for adhesive purposes was an ammonia extract of hemlock bark converted to a sodium derivative prior to spray drying, a more costly extraction procedure than simple sodium hydroxide extraction of bark.)... 

The only tannins in the world currently being commercially exploited for adhesive applications are those isolated by hot- (or cold-) water extraction of Acacia meamsii bark in the province of Natal, South Africa. Approximately 100,000 tons of mimosa tannin were being produced annually as reported in 1980, the latest year for which production figures were available (41)- Of this amount, about 10,000 tons were used in adhesive applications mainly in South Africa, Australia, and New Zealand. While this number is not large in light of the 300,000 to 400,000 tons of phenol used annually in resins, it does provide evidence that bark tannins can be economically used for adhesives. This application is facilitated by the relatively high cost of phenol and resorcinol in... 

Interest in pine bark as a source of adhesive components began to accelerate following the oil crisis of 1973. Sodium hydroxide extracts of southern pine bark were successfully used in replacing up to 40% of the phenolic resin for bonding of particleboards, oriented strandboards, and composites with a flakeboard core and veneer facing (50f51). Similar results were obtained with extracts from patula pine (52). Encouraged by results of this type, the New Zealand Forest Products Ltd. Corporation expanded their radiata pine bark tannin pilot plant to full-scale operation in 1981 to produce an extract trademarked Tannaphen. This material was crosslinked with paraformaldehyde and used as an adhesive... 

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