Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-02-27
2004-06-08
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C527S103000, C528S001000, C528S002000, C427S184000, C427S189000, C427S208000, C427S208200, C428S058000, C428S102000, C428S143000, C428S145000
Reexamination Certificate
active
06747076
ABSTRACT:
BACKGROUND OF THE INVENTION
The present disclosure relates to a novel and economical process for preparing bonded wooden substrates using an adhesive formulation based on a by-product obtained from a chemical pulping process. The adhesive formulation, which is novel and also forms part of the present invention, contains two parts, a reactive component and a catalyst component. When the two parts are mixed together and heated under pressure, they produce a strong, persistent bond.
The process of the present disclosure differs from processes commonly known in the arts to produce bonded wooden substrates. The wooded substrates are not pretreated with a chemical prior to bonding. It is not preferred to have a pretreatment step because it is an extra and expensive operation. Also, the chemical pretreatment is often performed with a substance having a low pH. Such acidic substances can cause degradation of the wood and weakening of the adhesive bond. The present process therefore avoids any chemical pretreatment of the wood prior to bonding.
The present process also differs from processes in the prior art in that the adhesive formulation contains a synergistic mixture that allows for spreading and assembly before curing, but cures very quickly upon heating. This allows for the preparation of a strong chemical bond, because the adhesive formulation is prevented from penetrating too deeply into the wood. A strong bond is therefore formed before the glue line is starved.
It is also an advantage of the present invention to employ a by-product from a chemical pulping process which is usually discarded as a waste product. Lignin is the inter-cellular material which binds together wood fibers to make solid wood. Lignin also stiffens the cell wall of the wood. Chemical pulping processes break down the lignin to release the wood fibers, the lignin being solubilized and removed, at least in part. The final product is a useful wood fiber pulp and a waste by-product of lignin in water or an organic solvent. There has been an ongoing search for new uses of lignin because of the large volumes of chemical pulp produced in the world. To this date, there have been limited opportunities for upgrading dissolved lignin.
Lignin is an adhesive in its natural state. Since dissolved lignin has reactive groups that should allow it to react in adhesive formulations, lignin has been employed in various wood adhesive formulations. Usually the lignin is employed simply as an extender in adhesives based on phenol-formaldehyde and the like.
U.S. Pat. No. 5,288,774, issued to Gardziella et al, relates to a refractory molding composition containing a novel binding agent. The binding agent is a lignin-furan resin mixture, the lignin being sulfur-free and having a low molecular weight. The furan resin is preferably a co-condensation resin of furfuryl alcohol and at least one member selected from the group consisting of formaldehyde and urea. The binding agents produced from these resin mixtures split off formaldehyde in the curing process to a greatly reduced extent in comparison to conventional furfuryl alcohol-formaldehyde resins and they are therefore not only more economical but also not harmful to the environment since the formaldehyde content at the workplace can be considerably lowered through the use of the raw material lignin.
U.S. Pat. No. 4,474,636, issued to Bogner, relates to novel binder compositions useful in the fabrication of composite articles such as fiber reinforced composite articles. In a most preferred embodiment, the resin binders for fabricating glass-reinforced laminates are furfuryl alcohol homopolymers, diluted with hydroxymethyl furfural. Also, the binder compositions have excellent strength characteristics and can be used advantageously in the manufacture of pressure molded medium or high density composite articles such as particle board, wafer board, oriented fiberboard, mat board, hardboard, pressboard, fiberglass board, and the like. The binder compositions can also be used in the manufacture of low density non-molded composite articles such as acoustical tile and thermal insulating mats or boards.
U.S. Pat. No. 4,357,194, issued to Stofko, relates to a method of bonding solid lignocellulosic materials with an adhesive-free bonding material comprising at least one sugar, starch or mixture thereof. The method includes the step of using live steam to heat the interior of the solid lignocellulosic material to a temperature of about 320° F. to about 420° F. The live steam activates phenolic material on the surfaces of the solid material, the activated phenolic material then reacting with the sugar, starch or mixture thereof. The phenolic material is preferably a lignin. In a preferred embodiment, the adhesive-free bonding material is a mixture of molasses and sulfonated lignin.
U.S. Pat. No. 4,183,997, issued to Stofko, relates to a method of bonding solid lignocellulosic materials with an adhesive-free bonding composition having a specified pH and containing sugar, starch or mixtures thereof. The adhesive-free composition also contains an alkaline buffering agent and a suitable catalyst. A suitable catalyst is zinc chloride.
U.S. Pat. No. 4,769,434, issued to Van der Klashorst et al, relates to a polymeric material which contains a reaction product from grass plant lignin derivatives. Lignin polymer fragments which have been recovered from black liquor obtained in the pulping of grass plant material are reacted with an electrophilic compound capable of reacting twice at one site or at least once at each of two different sites of the compound. The polymeric material is substantially the result of a cross-linking of the various lignin fragments by the electrophilic reactant. In a preferred embodiment, the electrophilic reactant is an aldehyde. The polymeric material can be employed as an adhesive used in the manufacture of wood products such as particle board, plywood, finger joints and the like. A filler such as nut shell flour can be included in the adhesive.
Canadian Pat. No. 409,226, issued to Marathon Paper Mills Company, relates to a resin product which is prepared by reacting furfuryl alcohol with a partially desulfonated lignin-sulfuric acid.
Canadian Pat. No. 1,128,241, issued to Holmens Bruk A B, Sweden, relates to a method of producing an adhesive for wood products. In the method, a waste product containing sugar and lignin is heated in a strongly acidic environment. This step gives a reaction mixture containing furfural derivatives. The reaction mixture is then further reacted to give a reaction product between the furfural derivatives and the lignin, the reaction product being an adhesive binder containing the condensation products of lignin and furfural derivatives.
DETAILED DESCRIPTION OF THE INVENTION
The preferred process for producing the bonding wooden substrates employs a novel adhesive formulation which is a two-part composition which can be mixed and used as a wood adhesive. The two-part composition comprises: (a) a reactive component comprising furfuryl alcohol monomer and a by-product obtained from a chemical pulping process, and (b) a catalyst component comprising zinc chloride, iron (III) chloride hex hydrate and maleic anhydride. The by-product is a polymer mixture comprising lignin and a liquid solvent. The liquid solvent is selected from water, an organic solvent and mixtures thereof. Typical organic solvents are hydrocarbons, ethers, alcohols and the like.
The lignin can be obtained from the wood of coniferous trees a well as lignin obtained from the wood of deciduous trees. In a preferred embodiment, the lignin can be obtained from the organosolve process under comparatively mild conditions, since its chemical structure has only slightly been changed through the effect of the processing conditions.
The process of the present invention comprises the steps of; obtaining two or more wooden substrates; coating at least one of the wooden substrates with the two-part adhesive formulation disclosed above; contracting the at least one coated substrate with a second
Phillips Jonathan G.
Schneider Marc H.
Jones Tullar & Cooper P.C.
Nutter Nathan M.
The University of New Brunswick
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