Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant which is a cellular material derived from...
Reexamination Certificate
1999-07-29
2001-10-23
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant which is a cellular material derived from...
C527S103000, C524S013000, C524S014000, C524S015000, C524S025000, C428S411100, C428S528000, C264S109000, C264S125000, C264S239000, C264S241000
Reexamination Certificate
active
06306997
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a soybean-based adhesive resin, composites products made with that adhesive, and a method of manufacturing such adhesives and composites products.
BACKGROUND OF THE INVENTION
Urea-formaldehyde (UF) resins and other formaldehyde-condensed resins, which are toxic petroleum-based adhesives, have been used as wood adhesives for many years. However, the level of formaldehyde gas emission from UF-bonded products is heavily regulated by law, particularly with respect to indoor use. In addition, the high cost of most formaldehyde-condensed resins and the poor moisture resistance of UF resins have resulted in the need for alternative wood adhesives.
There is a growing interest to develop wood adhesives from renewable substances to reduce the dependency on petroleum-based chemicals and to expand the non-food use of agricultural commodities. In particular, uncertainty in future supplies of petroleum-derived chemicals and stringent regulations on toxic emissions from building materials bonded with certain synthetic resins have compelled the forest products industry to reevaluate wood adhesives from renewable substances. The agriculture industry also is eager to invest in researching nonfood industrial uses of agricultural products to expand their markets. A significant challenge is to develop resin adhesives from renewable substances meeting stringent performance requirements at reasonable costs.
As an alternative to petroleum-based adhesives, protein glues, such as casein, blood, and soy glues, reached their peak use in the 1960s and faded out in the 1970s. Most of the important research on formulating wood adhesives with protein occurred before 1960.
U.S. Pat. No. 2,817,639 to Ash et al. disclosed a plywood glue containing high blood solids blended with a commercial phenol-formaldehyde (PF) resin ail sodium silicate. This required a specific mixing procedure to avoid a high viscosity problem. Lambuth, “Blood Glues,” in
Handbook of Adhesives
, I. Skeist, ed., Reinhols Publishing Corp., NY (1962) discloses the interactions between different types of PF resins and blood albumin. PF resins of simple structure behave much the same as aromatic alcohols, causing a change in blood glue consistency from gelatinous to granular, often accompanied by a reduction in viscosity. Alkaline phenolic resins of moderate complexity do not disperse blood proteins to a great extent. Highly complex and reactive PF resins, however, cause gelation of blood proteins, creating a major viscosity problem at any mixing combination. U.S. Pat. No. 2,368,466 to Golick et al. disclosed an exterior phenolic plywood glue containing up to 70% dried blood. This glue was prepared by first reacting cresol and casein with formaldehyde at room temperature to form an emulsion. This reaction was catalyzed by NH
4
OH. Subsequently, this emulsion was mixed with blood albumin at room temperature to form a smooth glue. The casein did not react with PF resins, and the fluid glue contained finely precipitated particles of blood albumin-phenol-aldehyde complex.
U.S. Pat. No. 3,153,597 to Weakley et al. disclosed moisture resistant plywood adhesives by cross-linking casein with dialdehyde starch.
U.S. Pat. No. 5,593,625 to Riebel et al. describes methods of preparing a legume-based thermosetting resin for producing rigid biocomposite materials. This resin was formulated by cross-linking soy flour with methyl diphenyl isocyanate and mixing the resin with paper fibers in a ratio about 4:6. A molded composite product was produced.
U.S. Pat. No. 5,371,194 to Ferretti describes a method of synthesizing a thermosetting resin from a mixture of protein and carbohydrate by ammoniation. This ammoniated resin was developed as a moisture resistant binder for pelletizing coal fines.
Further, the use of soy protein isolates and phenol-resorcinol-formaldehyde (PRF) in combination for lumber finger jointing is currently under mill trial studies. In this finger jointing system, the soy protein isolates and PRF are separately applied onto different fingers, and upon joining these fingers, interactions between soy protein and PRF first immediately cause the adhesive to gel and, eventually, the adhesive is completely cured in several hours.
Although great effort has been undertaken to develop protein glues, such glues were slow curing and had poor moisture resistance. As a result, the art sought to develop synthetic resin adhesives. Detlefsen, “Blood and Casein Adhesives For Bonding Wood,” in
Adhesives from Renewable Resources
, Hemingway et al., eds., ACS Symposium Series 385, Am. Chem. Soc., Washington, D.C. (1989).
The present invention is directed to overcoming the deficiencies in protein glues and their use in manufacturing composite products.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a soybean-based adhesive resin including a soybean flour and a cross-linking agent. The cross-linking agent is reacted with the functional groups in the soybean flour to form an adhesive resin.
The present invention also relates to a method of making a soybean-based adhesive resin. This method involves providing an aqueous solution of soybean flour and adding a cross-linking agent to the solution. The cross-linking agent is added to the solution under conditions effective to cross-link the soybean flour and the cross-linking agent to form an adhesive resin.
Another aspect of the present invention relates to a composite product which includes particulate plant material and the soybean-based adhesive resin. The adhesive is prepared by reacting the cross-linking agent with functional groups in the soybean flour.
The present invention also relates to a method of making a composite product. This method involves providing particulate plant material and applying the soybean-based adhesive resin to the particulate plant material. The adhesive is prepared by reacting the cross-linking agent with the functional groups in the soybean flour.
The soybean-based adhesive resin of the present invention provides a low-cost wood adhesive from a renewable resource as an alternative to petroleum-based adhesives. This resin can be used as an exterior adhesive in the manufacture of wood composite panel products and can replace urea-formaldehyde resins for interior fiberboard, alleviating formaldehyde emissions and poor moisture resistance problems.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a soybean-based adhesive resin including a soybean flour and a cross-linking agent. The cross-linking agent is reacted with the functional groups in the soybean flour to form an adhesive resin.
Preferably, the soybean flour contains more proteins than carbohydrates.
Most preferably, the soybean flour is defatted. Defatted soybean flour is commercially available and is obtained by grinding soy flakes after hexane extraction for soy oil. After hexane extraction, defatted soybean flour typically has the following moisture-free chemical composition:
Protein
50.0% to 55.0%
Fat
1.4% to 2.0%
Fiber
3.0% to 4.5%
Ash
5.0% to 7.0%
Carbohydrates
34.0% to 37.0%
Most preferably, after soy oil extraction, defatted soybean flour has the following moisture-free average chemical composition:
Protein
53.4%
Fat
1.6%
Fiber
3.4%
Ash
6.0%
Carbohydrates
35.6%.
The cross-linking agent reacts with the functional groups in the soybean flour to form an adhesive resin. Suitable cross-ling agents include phenol-formaldehyde resin, melamine-urea-formalde resins, and mixtures thereof.
The preferred cross-linking agent is a phenol-formaldehyde (PF) resin. In this embodiment, the hydroxymethylol groups (—CH
2
OH) of the PF resin react with the functional groups of the soybean protein, such as tyyosine and hydroxyl groups (—OH), to form methylene or ether linkages between the soy protein and the PF resin. In addition, the hydroxymethylol groups of the PF resin react with the hydroxyl groups of the soybean carbohydrates to form ether linkages. These condensation reactions between the PF resin and protein and ca
Adams Daniel O.
Curry Daniel
Heemstra Howard
Kuo Monlin
Myers Deland J.
Hampton-Hightower P.
Iowa State University & Research Foundation, Inc.
Nixon & Peabody LLP
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