Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
C528S129000, C528S230000, C525S480000, C525S507000
This invention relates to bonding resins and particularly to the use of renewable resources in or as substitutes for formaldehyde-based resins.
The wood products industry is still almost entirely dependent on chemicals derived from petroleum and natural gas for producing the necessary bonding agents. The application of bonding agents enables the use of smaller trees, wood chips, fibers and mill residues to produce various products that meet the consumer needs. As the quality of harvested timber declines due to the shrinking commercial forest land base, the future of wood utilization will require an even higher dependence on bonding agents to convert the limited timber resources into needed products. In view of the environmental strains caused by fossil fuels and chemicals and their inherent vulnerable and limited supply, the efforts to identify other available resources for bonding raw materials have accelerated in the latest decades. Renewable resources are he most promising in this field and much research and development have been devoted in this area.
Formaldehyde-based resins (urea-formaldehyde (UF), phenol-formaldehyde (PF), melanine-formaldehyde (MF), melamine-urea-formaldehyde (MUF), resorcinol-formaldehyde (RF), tannin-formaldehyde (TF) and mixtures thereof) are most commonly applied in composite wood panel manufacture. The components of these resins are mainly derived from oil and/or natural gas. It is the aim of the present application to provide effective resin substitutes derived from natural products such as renewable forest biomass and agricultural residues.
Numerous studies were based on the role of products of natural origin in providing alternative feedstocks for wood adhesives. Chen, C. M., “Gluability of Copolymer Resins Having Higher Replacement of Phenol by Southern Pine Foliage Extracts for Flakeboards and Composite Panels”, Holzforschung, 1993, 47 (1), 72-75, “State of the Art Report: Adhesives from Renewable Resources”,
Holzforschung und Holzverwertung
, 1996, 4, 58-60, “A Hulluva Switch: Inventor Finds Value in Peanut Hulls”, The University of Georgia, Research Reporter, 12-13, reported that extracts of peanut hulls, pecan nut pith or pine bark and foliage can be used to replace up to 80% of the phenol used for phenol-formaldehyde resins. The extraction process involved several stages and was time-consuming.
Efforts have been made also to utilize the oil obtained by the pyrolysis of biomass or its phenolic fraction to substitute phenol in the production of phenol-formaldehyde resins, Gallivan, R. M., Matschei, P. K., “Fractionation of Oil obtained by Pyrolysis of Lignocellulosic Materials to recover a Phenolic Fraction for use in making Phenol-Formaldehyde Resins”, U.S. Pat. No. 4,209,647, 1980; Diebold, J., Power, A., “Engineering Aspects of the cortex Pyrolysis Reactor to Produce Primary Pyrolysis Oil Vapors or Use in Resins and Adhesives”,
Research in Thermochemical Biomass conversion
, Bridgwater, A. V., Kuester, J. L., Elsevier Applied Science, London, 1988, 609-628; Chum, H. L., Diebold, J. P., Scahill, J. W., Johnson, D. K., Black, S., Schroeder, H. A., Kreibich, R. E., “Biomass Pyrolysis Oil Feedstocks for Phenolic Adhesives”, Adhesives from Renewable Resources, R. Hemingway and A. Conner, Eds., ACS Symp. Series, No. 385, 1989, 135-151; Chum, H. L., Black, S. K., “Process for Fractionating Fast-Pyrolysis Oils, and Products derived therefrom”, U.S. Pat. No. 4,942,269, 1990; Chum, H. L., et alk. “Inexpensive Phenol Replacements from Biomass”,
Energy from Biomass and Wastes XV
, Eds. Klass, D. L., 1991, 531-540. Substitution levels of up to 75% have been reported, however the low amount of phenolic compounds present in the oil necessitates a factionation step, which raises the final product cost.
The spent liquor obtained from the paper manufacturing process, comprising mainly the degradation products of lignin, has been the subject of a large number of studies relating to its applicability in formaldehyde-based adhesive systems (mainly PF-adhesives), Forss, K. J., Fuhrmann, A., “Finnish Plywood, Particleboard, And Fibreboard Made With a Lignin-Base Adhesive”, Forest Prod. J., 1979, 29 (7), 36-43; Doering, G. A., Harbor, G., “Lignin Modified Phenol-Formaldehyde Resins”, U.S. Pat. No. 5,202,403; Chen, C. M., “Gluability of raft Lignin Copolymer Resins on Bonding Southern Pine Plywood”,
, 1995, 49 (2), 153-157; Senyo, W. C., Creamer, A. W., Wu, C. F., Lora, J. H., “The Use of Organosolv Lignin to Reduce Press Vent Formaldehyde Emissions in the Manufacture of Wood Composites”, Forest Prod. J., 1996, 46 (6), 73-77. Various replacement scenarios have been tested, yet the low reactivity of this Liquor cannot justify its use without including any additional modification steps.
In the use of these materials single products have been employed and attempts to improve performance have been made by modification of the material usually to try and increase the phenolic content.
According to the present invention there is provided a phenol/aldehyde resin system in which a significant proportion of the phenol component conventionally employed in such resin is replaced by a mixture of at least two different natural phenolic materials.
The invention also provides a method of forming composite materials in which a proportion of the phenol/aldehyde resin component is replaced by a phenol/aldehyde resin system of the invention.
An advantage of the invention is that it permits lowering of resin toxicity by use of the natural substitutes now specified instead of toxic petroleum derived phenolic products. Thus the phenol/aldehyde resin system of the invention provides an advantage in that it enables replacement of conventional phenol materials even though the properties of the resin system are not superior to those achieved by normal phenol materials.
The phenol/aldehyde resin systems which can be modified in accordance with this invention are those which are conventional in the manufacture of bonding agents and adhesives. The term “bonding agent” is used generically to include adhesive materials. The most common of these resins is, of course, phenol/formaldehyde but phenol can be replaced by other materials within the generic term phenol for example cresol or resorcinol to the extent that this is conventional in the phenol/aldehyde resin art and formaldehyde can be replaced by certain other aldehydes although this is not so common In the art. Those skilled in the art of using phenol/aldehyde resins will be well aware of the alternatives and combinations available. The choice of phenois and aldehydes will normally be related to the types of resins employed for the bonding of composite products but he invention is also applicable to phenol/aldehyde resins employed in other bonding and adhesive functions.
Each of the natural phenolic materials which are used in part substitution of the phenol component of the conventional phenol/aldehyde resin will be derived from a natural source. The difference between these materials can arise from the nature of the source or from a variation in treatment of the same natural source so as to provide materials with different properties for example the nature of the phenolic compounds or their proportion. Each of the materials will have, however, a significant content of phenolic components. The phenolic content can be free phenols or phenolic groupings in molecules forming part of the material. By phenolic content is meant the presence in the molecular structure of one or more components (eg. polymeric components) of phenol structures, i.e. hydroxy substituted aromatic groupings or molecular groupings exhibiting the characteristic properties of phenols. Phenol may be present but usually the component is a compound with a phenolic grouping. Since the natural materials employed in forming the combinations of the invention are often derived from lignin, a natural polymer containing phenolic groups in the structure, extracts, or modifications of such materials will contain phenolic content. The material can be a natural pla
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