Phenol formaldehyde binder

Wood Composites—these are resin-bonded composite boards where the particles are wood shavings, flakes, chips, or fibers bonded with thermosetting adhesives that can be urea formaldehyde, melamine formaldehyde, phenol formaldehyde, or diisocyanate. In recent years, the markets for OSB and MDF board have been rapidly increasing. Most particle board production uses urea-formaldehyde as a binder that is acid setting. Hence, sodium borates (alkaline) can interfere with the setting. As a result, boric acid has been the major boron compound used as the flame retardant in particle board.28 29 Typically, a loading of 12%-15% of boric acid in MDF is required to meet the ASTM E-84 Class A rating. If sodium borate is used as a flame retardant, phenol-formaldehyde binder, that is compatible with alkaline chemicals, is commonly used. 

The initial development of polymeric MDI as a particleboard binder predates the above work but it is, we believe, based upon the same chemistry. Exterior or structural particleboard has been manufactured in North America and in Europe for years with predominantly phenol-formaldehyde binders and, in a few cases, with melamine-modified urea-formaldehyde binders. The familiar urea-formaldehyde resins are subject to hydrolysis and are thus suitable for interior board only. 

The purpose of this presentation has been to illustrate some advantages that are possible in the use of polymeric MDI as a binder for exterior grade wood composite panels. The data given have indicated the potential for savings in press time, press temperature, flake moisture content, resin level and panel density (as compared to conventional phenol-formaldehyde binders) in several types of such panels. 

Phenol—formaldehyde resins are used as mol ding compounds (see Phenolic resins). Their thermal and electrical properties allow use in electrical, automotive, and kitchen parts. Other uses for phenol—formaldehyde resins include phenoHc foam insulation, foundry mold binders, decorative and industrial laminates, and binders for insulating materials. 

Glassy, or vitreous, carbon is a black, shiny, dense, brittle material with a vitreous or glasslike appearance (10,11). It is produced by the controUed pyrolysis of thermosetting resins phenol—formaldehyde and polyurethanes are among the most common precursors. Unlike conventional artificial graphites, glassy carbon has no filler material. The Hquid resin itself becomes the binder. 

This includes wire enamels on a base of polyvinyl formal, polyurethane or epoxy resins as well as moulding powder plastics on phenol-formaldehyde and similar binders, with cellulose fillers, laminated plastics on paper and cotton cloth base, triacetate cellulose films, films and fibres of polyethylene terephthalate. 

The route to crosslinked phenol-formaldehyde resins via resoles corresponds to that used by Baekeland in his original commercial technique. They now tend to be used for adhesives, binders, and laminates. The resole... 

The production of moisture resistant particleboard by treatment with a maleic anhydride -glycerol mixture and using phenol formaldehyde as the matrix material has been investigated (Fujimoto etal., 1987). Boards prepared from modified wood showed considerable improvements in modulus of elasticity and internal bond strength when compared to control boards. Composites made from aspen fibres modified with SA, MA or acetic anhydride using phenol-formaldehyde (PF) or polypropylene as binder have also been studied (Clemons etal., 1992 Rowell etal., 1993b). The reaction of wood with MA was found to proceed at a slower rate than with SA. The volume increase due to modification... 

To produce composites, a binder rather than a size is usually required. A variety of high-temperature, high-strength compounds now available facilitate comparability of the fibers with matrix compounds. Insulation fibrous glass has been paired with phenol formaldehyde resins and a mineral oil lubricant. The binder may be up to 12 percent by weight of the final product (Barnhart, 1976). The composite compositions are discretely different from those of textiles in which fiber coatings are usually less than 0.5 percent of the total. 

Iditol. A synthetic resin obtained by the condensation of phenol formaldehyde. It is used as a binder in many Russian pyrotechnics Ref Gorst (1957), 162... 

Ammonia and ammonium persulfate can also be used as reagents (21). However, as pointed out by Nimz (48) and other authors, owing to the non-uniformity of the product, only 15% of urea-formaldehyde and 25% phenol-formaldehyde resin binder may be replaced by calcium base spent sulfite liquors. 

Technological advances continue to be made, several recent patents describe advanced phenol—formaldehyde—furfuryl alcohohol binder systems (68—70). These systems are free of nitrogen compounds that can be detrimental to metal integrity. Systems with extended bench life have also been developed (71). 

The cyclic alkylene carbonates have also been applied as the cure-accelerators of phenol-formaldehyde (PF) [262-266] and sodium silicate [267] resin systems, which are widely used in foundry sand and wood binder applications. 

Properties of the HDA boards prepared from the activated substrate may be compared to the phenol-formaldehyde (PF) boards prepared using 6 resin solids. Comparison may also be made to the property requirements from commercial standard CS 236-66, type 2 medium density (below 0.8 g/cc), Class 1 particleboard fabricated using durable and highly moisture resistant and heat resistant binders suitable for interior and certain exterior applications. Specifications of this class of particleboard, generally prepared from PF resins, are MOR, minimum = 2,500 psi M0E, minimum =... 

In a first classification, we can distinguish (i) boards made with an external synthetic binder, such as urea-formaldehyde or phenol-formaldehyde resins for thermosets, and (ii) boards with internal natural binders. The products cited below do not constitute an exhaustive list. 

Urea-formaldehyde resins are used for applications in which the panel is not in contact with water. For applications with high level of humidity, the phenol-formaldehyde resins are required. In all cases, free formaldehyde constitutes a dangerous pollutant that is slowly released and can be particularly toxic in confined rooms. Recent research has been done to substitute this type of resin by natural binders, such as cross-linkable proteins (Silvestre et al., 2000 Yang et al., 2006). 

There have been many attempts to replace these resins with lignin derivatives for wood composite adhesives suitable for plywood, particleboard and waferboard. Most of these studies have been empirical in nature, and few have achieved further consideration for industrial application. As wood binders, technical lignins are variable in quality and poorly reactive in comparison to conventional resin systems such as phenol-formaldehyde (PF) resins. Consequently, they are not utilized on their own. Indeed, if they were, this would adversely affect production quality and times, and necessitate equipment changes. In the wood composite industry, resins having such deleterious effects are not likely to be used even if savings could be made in terms of material costs. 

Figure 21 Modulus of rupture in bending of surface-benzylated and self-bonded boards. BE21% (O) benzylated board with a 21 WPG BE38% (A) benzylated board with a 38 WPG BE51% ( ) benzylated board with a 51 WPG. PF ( ), conventional particleboard bonds using phenol-formaldehyde resin binder acted as a control. (From Ref. 32.)...

Economically the Philippou process appears to be somewhat more expensive than phenol-formaldehyde. In December 1981, the cost of binder raw material for 1000 ft of HNO3 board was estimated to run 22.60, vs. 28.30 for HgOg board, and 21.00 for phenol-formaldehyde board. Further work, particularly on alternative ingredients, can change the situation (103),... 

Nonconventional Bonding with Acid Activation. Concentrated or spray-dried, spent sulfite liquor, with or without previous ultrafiltration, was used as a binder for waferboards. The press temperatures used were between 210 and 230 °C and the press times between 5 and 10 min, with the amount of resin between 4 and 5%. The boards produced were better or comparable to the boards made using phenol-formaldehyde resin according to IB, MOE, MOR, hardness, and linear expansion tests the cost of the binder was twofold or threefold less (187). 

Bonded insulating materials, e.g. sheets or rolls, are manufactured by spraying a binder resin, generally phenol/formaldehyde, onto the fibers and hardening under compaction in a tunnel kiln... 

In the manufacture of bonded insulating materials, the fibers in the fleece shaft or on the conveyor belt are sprayed with an aqueous binder, generally a phenol-formaldehyde resin. The binder content in the bonded insulating material is 3 to 4%. Compaction to the desired density and hardening of the resin binder occurs in a tunnel kiln, through which the fibers are continuously transported on a conveyor belt. The compaction is achieved with a second belt which exerts the required pressure on the upper surface of the continuous sheet. This is often followed by laminating the sheet with e.g. paper, aluminum or plastic foil. Finally the product is rolled up or cut into sheets. 

During the past decade, urea formaldehyde and phenol formaldehyde resin binders have contributed greatly to the progress of wood industries. Formaldehyde is widely used as a major component in the production of building materials, such as particleboard and plywood, and in urea formaldehyde foam insulation. However, the emissions of formaldehyde from these products create considerable concerns not only in the working environments but also in residences, mobile homes, and office buildings. These concerns have also been stimulated by reports on the health effects and carcinogenicity associated with formaldehyde exposure. 

---