Protein-containing adhesives, and manufacture and use thereof   

Abstract: The invention provides protein adhesives and methods of making and using such adhesives. One type of protein adhesive described herein contains lignin and ground plant meal or an isolated polypeptide composition obtained from plant biomass. Other types of protein adhesives described herein contain a plant protein composition and either a hydroxyaromatic/aldehyde, urea/aldehyde, or amine/aldehyde component.

This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 61/532,832, filed Sep. 9, 2011, and to U.S. Provisional Patent Application Ser. No. 61/567,769, filed Dec. 7, 2011, the contents of each of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention relates to protein adhesives, and to methods of making and using such adhesives. The protein adhesives contain ground plant meal or an isolated polypeptide composition obtained from plant biomass, and are useful in the preparation of various wood products.

Adhesive compositions are used extensively in the wood products industry to make composites such as chipboard, fiberboard, and related composite wood products. Adhesive compositions are also used to make engineered lumber composites. Recent environmental concerns emphasize the need for adhesive compositions that are environmentally friendly. Adhesive compositions frequently used in the wood products industry, however, are not environmentally friendly. Thus, the need exists for adhesive compositions that reduce the need for petroleum feedstock, minimize use of toxic chemicals, and are amenable to the cure conditions and performance requirements for wood products.

In response to the need for environmentally friendly adhesive compositions, there has been renewed interest in using certain soy products to form adhesive compositions. However, there are multiple challenges in developing an adhesive composition from soy products. For example, the adhesive composition when cured to form a binder must have sufficient bond strength. The adhesive composition when cured to form a binder should, for certain applications, be sufficiently resistant to moisture. Another challenge is that the adhesive composition must have sufficient pot life so that it does not cure before being applied to components in the wood product. It is also important that the soy product be capable of production on large scale at economically feasible terms, and that it is amenable to cure conditions used to form the wood product.

Various reports describe efforts at developing an adhesive composition using certain soy products. U.S. Patent Application publication 2008/0021187 describes an adhesive composition containing urea-denatured soy flour. U.S. Pat. No. 7,416,598 describes an adhesive composition containing a protein ingredient and a modifying ingredient. Zhong and coworkers describe an adhesive composition containing certain soy protein material that has been modified. Zhong et al. in J. Appl. Polym. Sci. (2007) 103: 2261-2270. Yet, despite these efforts, the need exists for an environmentally friendly adhesive composition that meets the demands for widespread industrial application in the wood products industry.

The present invention addresses this need, and provides other related advantages.

SUMMARY

The invention provides protein adhesive compositions, methods of making and using such adhesives, and articles prepared using such adhesives. The protein adhesive compositions contain a plant protein composition, such as ground plant meal or an isolated polypeptide composition obtained from plant biomass. The adhesive compositions also contain, for example, a lignin, hydroxyaromatic compound and an aldehyde source, a urea compound and an aldehyde source, and/or an amine compound and an aldehyde source. The plant protein composition is advantageous because it is prepared from plant biomass, a renewable feedstock that is generally a waste by-product of the agricultural industry. The adhesive compositions are useful in preparing wood composites, such as particle board.

Accordingly, one type of protein adhesive composition provided by the invention contains lignin and a plant protein composition. Lignin is a biopolymer that can be isolated from wood. It has been unexpectedly discovered that use of lignin in combination with plant protein compositions described herein provide an adhesive that can be applied to wood particles to form a particle board composite. Experiments using lignin alone failed to produce a formulation with sufficient cohesive strength to produce a particle board composite. Accordingly, one aspect of the invention provides an adhesive composition comprising lignin and a plant protein composition.

Another type of protein adhesive composition provided by the invention contains a hydroxyaromatic compound (e.g., phenol), an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. The plant protein composition is contemplated to provide performance benefits to the adhesive composition. The aldehyde source may be an aldehyde or a composition that releases an aldehyde (e.g., formaldehyde) in situ. Accordingly, another aspect of the invention provides a hydroxyaromatic-aldehyde adhesive composition comprising a hydroxyaromatic compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. A more specific embodiment of such protein adhesives relates to a phenol-formaldehyde-plant protein adhesive composition that comprises: (a) phenol; (b) formaldehyde; (c) a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition; and (d) a reactive prepolymer; wherein the ratio of (i) weight percent of reactive prepolymer in the adhesive composition to (ii) the sum of the weight percent of phenol and formaldehyde in the adhesive composition is greater than 1:1. A second more specific embodiment of such protein adhesives relates to a phenol-formaldehyde-plant protein adhesive composition that comprises: (a) phenol and formaldehyde that together constitute from about 0.5% w/w to about 10% w/w of the adhesive composition; (b) ground plant meal in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; (c) polymeric diphenylmethane diisocyanate in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; and (d) water in an amount ranging from about 45% w/w to about 75% w/w of the adhesive composition.

Yet another type of protein adhesive composition provided by the invention contains a urea compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. The plant protein composition is contemplated to provide performance benefits to the adhesive composition. The aldehyde source may be an aldehyde or a composition that releases an aldehyde (e.g., formaldehyde) in situ. Accordingly, another aspect of the invention provides a urea compound-aldehyde adhesive composition comprising a urea compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition.

Yet another type of protein adhesive composition provided by the invention contains an amine compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. The plant protein composition is contemplated to provide performance benefits to the adhesive composition. The aldehyde source may be an aldehyde or a composition that releases an aldehyde (e.g., formaldehyde) in situ. Accordingly, another aspect of the invention provides an amine compound-aldehyde adhesive composition comprising an amine compound selected from the group consisting of a primary amine compound and second amine compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition.

In another aspect, the invention provides a solid binder composition formed by curing an adhesive composition described herein.

In another aspect, the invention provides a method of bonding a first article to a second article. The method comprises the steps of (a) depositing on a surface of the first article any one of the foregoing adhesive compositions thereby to create a binding area; and (b) contacting the binding surface with a surface of the second article thereby to bond the first article to the second article. The method optionally also comprises the step of, after step (b), permitting the adhesive composition to cure, which can be facilitated by the application of pressure, heat or both pressure and heat.

In another aspect, the invention provides a method of producing a composite material. The method comprises the steps of (a) combining a first article and a second article with any one of the foregoing adhesive compositions to produce a mixture; and (b) curing the mixture produced by step (a) to produce the composite material. The curing can comprise applying pressure, heat or both pressure and heat to the mixture.

In certain embodiments, the first article, the second article or both the first and second articles are lignocellulosic materials, or composite materials containing lignocellulosic material. The first article, the second article or both the first and second articles can comprise a metal, a resin, a ceramic, a polymer, a glass or a combination thereof. The first article, the second article, or both the first article and the second article can be a composite. In addition, the invention provides an article produced by each of the foregoing methods of manufacture.

In addition, the invention provides an article comprising two or more components bonded together using one or more of the adhesive compositions described herein. The bonded components can be selected from the group consisting of paper, wood, glass, metal, fiberglass, wood fiber, ceramic, ceramic powder, plastic (for example, a thermoset plastic), and a combination thereof. In certain other embodiments, the bonded components can be selected from the group consisting of paper, wood, glass, metal, fiberglass, wood fiber, ceramic, ceramic powder, sand, plastic (for example, a thermoset plastic), and a combination thereof. The invention provides an article (for example, a composite material, laminate, or a laminate containing composite material) produced using one or more of the adhesive compositions described herein.

The composite material can be chip board, particle board, fiber board, plywood, laminated veneer lumber, glulam, laminated whole lumber, laminated composite lumber, composite wooden I-beams, medium density fiberboard, high density fiberboard, orientated strand board, extruded wood, or fiberglass. The composite can be a thermosetting composite or a thermoplastic composite.

In certain embodiments, the article is a composite, such as a random non-oriented homogeneous composite, an oriented composite, or a laminated composite. In certain other embodiments, the article comprises a lignocellulosic component. Furthermore, the article can comprise paper, wood, glass, fiberglass, wood fiber, ceramic, ceramic powder, or a combination thereof.

In certain embodiments, the article is a particle board composite. The amount of wood and adhesive composition used to prepare the particle board composite can be adjusted to optimize the performance properties of the particle board for different applications (e.g., outdoor use where increased water resistance is desirable). In certain embodiments, the composite comprises at least about 80% (w/w) wood, at least about 90% (w/w) wood, at least about 95% (w/w) wood, or at least about 98% (w/w) wood.

Depending upon the adhesive used, the resulting article can have one or more of the following features: the article is moisture resistant; the article remains intact after boiling in water for 5 minutes; two or more components of the article remain bonded after boiling in water for 5 minutes; the article, when boiled in water for 5 minutes, displays less than a 20% increase in volume relative to the article prior to exposure to the water; and when the article (for example, a composite material, laminate, or a laminate containing a composite material) contains a lignocellulosic material in the composite material or laminate, the article exhibits no less than 50%, optionally no less than 75%, cohesive failure of the lignocellulosic component when the article is placed under a loading stress sufficient to break the article. In certain embodiments, the article exhibits no less than 50% cohesive failure of the lignocellulosic component when the article is placed under a loading stress sufficient to break the article.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will become apparent from the following description of preferred embodiments, as illustrated in the accompanying drawings. Like-referenced elements identify common features in the corresponding drawings. The drawings are not necessarily to scale, with emphasis instead being placed on illustrating the principles of the present invention, in which:

FIG. 1 is a flow chart showing the steps of an exemplary method for producing isolated polypeptide compositions useful in the practice of the invention;

FIG. 2 shows overlaid solid state FTIR spectra for water-soluble and water-insoluble protein fractions isolated from digested castor lot 5-90;

FIG. 3 shows solid state FTIR spectra of isolated water-soluble and water-insoluble fractions from digested castor, where the carbonyl amide region is expanded;

FIG. 4 shows solid state FTIR spectra of isolated water-soluble and water-insoluble fractions from digested castor where the N—H stretching region is expanded;

FIG. 5 shows overlaid solid state FTIR spectra of isolated fractions from castor protein (lot 5-94), showing an expansion of the carbonyl amide region (water-soluble fraction, and water-insoluble/water-dispersible fraction);

FIG. 6 shows the solid state FTIR spectra of isolated water-soluble and water-insoluble fractions from castor protein (lot 5-94), where the N—H and O—H stretch regions are expanded;

FIG. 7 shows overlaid solid state FTIR spectra of the isolated water-insoluble/water-dispersible fractions from castor protein (lot 5-94) and from enzyme digested castor (lot 5-90);

FIG. 8 shows overlaid solid state FTIR spectra of isolated water-soluble and water-insoluble fractions from digested soy, where the carbonyl amide region is expanded, where the spectra were vertically scaled to achieve equivalent absorbance intensities for the amide-I carbonyl stretch;

FIG. 9 shows overlaid solid state FTIR spectra of isolated water-soluble and water-insoluble fractions from digested soy, where the N—H stretching region is expanded;

FIG. 10 shows overlaid solid state FTIR spectra of isolated water-soluble polypeptide fractions from digested soy and digested castor;

FIG. 11 shows overlaid solid state FTIR spectra of isolated water-insoluble fractions from digested soy and soy flour;

FIG. 12 shows overlaid solid state FTIR surface ATR spectra of the isolated water-insoluble/water-dispersible fractions from multiple protein samples (digested soy lot 5-81, soy flour, castor protein isolate lot 5-94, digested castor lot 5-90) where the carbonyl amide region is expanded;

FIG. 13 is a two-dimensional HSQC 1H—15N NMR spectrum for digested castor (lot 5-83) in d6-DMSO, showing two regions of interest denoted Region A and Region B;

FIG. 14 is a two-dimensional HSQC 1H—15N NMR spectrum for water-insoluble/water-dispersible polypeptide fraction derived from digested castor (lot 5-83) in d6-DMSO, again showing Region A and Region B;

FIG. 15 is a two-dimensional HSQC 1H—15N NMR spectrum, where Region A from FIG. 14 has been magnified;

FIG. 16 shows solid state FTIR spectra of isolated water-soluble and water-insoluble fractions obtained from ground soy meal, where the N—H and O—H stretch regions are expanded;

FIG. 17 shows overlaid solid state FTIR spectra of isolated water-soluble and water-insoluble fractions obtained from ground soy meal, where the carbonyl amide region is expanded and the spectra were vertically scaled to achieve equivalent absorbance intensities for the amide-I carbonyl stretch;

FIG. 18 shows overlaid solid state FTIR spectra of isolated water-soluble and water-insoluble/water-dispersible protein fractions obtained from ground canola meal, where the N—H and O—H stretch regions are expanded, as described further in Example 5;

FIG. 19 shows overlaid solid state FTIR spectra of isolated water-soluble and water-insoluble/water-dispersible protein fractions obtained from ground canola meal, where the carbonyl amide region is expanded and the spectra were vertically scaled to achieve equivalent absorbance intensities for the amide-I carbonyl stretch, as described further in Example 5;

FIG. 20 shows overlaid solid state FTIR spectra of isolated water-soluble and water-insoluble/water-dispersible protein fractions obtained from soy flour, as described further in Example 5;

FIG. 21 shows overlaid solid state FTIR spectra of isolated water-insoluble/water-dispersible protein fractions obtained from soy meal and soy flour, as described further in Example 5; and

FIG. 22 shows particle board composites prepared in Example 6, along with samples TP-12 and TP-13 that cohesively disintegrated upon removing them from the press.

DETAILED DESCRIPTION

The invention provides protein adhesive compositions and methods of making and using such adhesives. Also, the invention provides articles, such as wood composites, made using the protein adhesive compositions. The protein adhesive compositions described herein contain a plant protein composition. The plant protein composition is obtained from a renewable feedstock and provides multiple advantages in the preparation of adhesive compositions. The protein component is preferably ground plant meal or an isolated polypeptide composition derived from plant meal. The adhesive compositions also contain, for example, a lignin, hydroxyaromatic compound and an aldehyde source, a urea compound and an aldehyde source, and/or an amine compound and an aldehyde source.

One type of protein adhesive composition provided by the invention contains lignin and a plant protein composition. Another type of protein adhesive composition provided by the invention contains a hydroxyaromatic compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. Yet another type of protein adhesive composition provided by the invention contains a urea compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. Yet another type of protein adhesive composition provided by the invention contains an amine compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. Features of these protein adhesive compositions are described in more detail in the sections below.

The adhesives described herein can be used in the production of a variety of wood-based products including composite materials, laminates, and laminates that contain composite materials. For example, the adhesives can be used in the production of consolidated wood composites, for example, chipboard (also known as OSB), fiberboard, and related composite wood products, as well as in the production of engineered lumber composites, for example, I-beams (I-joists), laminated veneer lumber (LVL), and other types of structural lumber composites.

The following sections describe lignin-containing protein adhesives, hydroxyaromatic-aldehyde adhesive composition (e.g., phenol/formaldehyde adhesive compositions), urea compound-aldehyde adhesive composition (e.g., urea/formaldehyde adhesive compositions), amine compound-aldehyde adhesive composition (e.g., melamine/formaldehyde adhesive compositions), additives that may be included in the adhesive compositions, and methods of using such adhesives, and articles formed from such adhesives.

It has been unexpectedly discovered that use of lignin in combination with plant protein compositions described herein provide an adhesive. The adhesive can be applied to wood particles to form, for example, a particle board composite. As explained in Example 6, experiments using lignin alone failed to produce a formulation with sufficient cohesive strength to produce a particle board composite.

Accordingly, one aspect of the invention provides an adhesive composition comprising lignin and a plant protein composition. Further description of lignin and plant protein compositions is described in the sections below. The adhesive composition may be in the form of a liquid. Alternatively, the adhesive composition may be in the form of a dry mixture. The adhesive composition may further comprise one or more additives, such as the additives described in Section VIII below, which include, for example, an intercalated clay, an exfoliated clay, and a partially exfoliated clay.

In certain embodiments, the adhesive composition may further comprise a reactive prepolymer. In certain other embodiments, the adhesive composition may further comprise a hydroxyaromatic compound (e.g., phenol) and an aldehyde source, such as those described in Section II below. In certain other embodiments, the adhesive composition may further comprise a urea compound (e.g., H2NC(O)NH2) and an aldehyde source, such as those described in Section III below. In certain other embodiments, the adhesive composition may further comprise an amine compound (e.g., melamine) and an aldehyde source, such as those described in Section IV below. In yet other embodiments, the adhesive composition further comprises an aldehyde source, such as an aldehyde source described in Section IV below.

In certain embodiments, the adhesive composition further comprises water. For example, in certain embodiments, water is present in an amount of from about 30% w/w to about 65% w/w of the adhesive composition. In certain other embodiments, water is present in an amount of from about 20% w/w to about 50% w/w, about 30% w/w to about 60% w/w, about 40% w/w to about 70% w/w, about 50% w/w to about 80% w/w, or about 10% w/w to about 90% w/w of the adhesive composition.

The amount of lignin in the adhesive composition may be adjusted to achieve certain performance properties. For example, in certain embodiments, the adhesive composition comprises from about 1% w/w to about 50% w/w lignin, from about 1% w/w to about 35% w/w lignin, from about 1% w/w to about 15% w/w lignin, from about 5% w/w to about 35% w/w lignin, from about 15% w/w to about 35% w/w lignin, or from about 20% w/w to about 45% w/w lignin. In certain other embodiments, the adhesive composition comprises from about 5% w/w to about 35% w/w lignin.

The amount of plant protein composition in the adhesive composition may be adjusted to achieve certain performance properties. For example, in certain embodiments, the adhesive composition comprises from about 5% w/w to about 50% w/w plant protein composition, from about 5% w/w to about 35% w/w plant protein composition, from about 5% w/w to about 30% w/w plant protein composition, from about 15% w/w to about 35% w/w plant protein composition, or from about 20% w/w to about 30% w/w plant protein composition. In certain other embodiments, the adhesive composition comprises from about 15% w/w to about 35% w/w plant protein composition.

The amount of plant protein composition may be selected relative to the amount of lignin in the adhesive composition. For example, in certain embodiments, the ratio of weight percent plant protein composition in the adhesive composition to weight percent lignin in the adhesive composition is from (a) 99.9:0.1 to 0.1:99.9, (b) 9:1 to 1:9, (c) 5:1 to 1:5, or (d) 2:1 to 1:2.

A more specific embodiment relates an adhesive composition that comprises: (a) lignin in an amount ranging from about 5% w/w to about 30% w/w of the adhesive composition; (b) ground plant meal in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; and (c) water in an amount ranging from about 45% w/w to about 75% w/w of the adhesive composition. In certain embodiments, the lignin has a weight average molecular weight of about 10,000 g/mol to about 70,000 g/mol.

Another aspect of the invention provides a hydroxyaromatic-aldehyde protein adhesive composition. The adhesive composition comprises a hydroxyaromatic compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition. The adhesive composition may be in the form of a liquid. Alternatively, the adhesive composition may be in the form of a dry mixture.

The adhesive composition may further comprise one or more additives, such as the additives described in Section VIII below, which include, for example, an intercalated clay, an exfoliated clay, and a partially exfoliated clay. Further, the adhesive composition may comprise lignin, such as a lignin described below in Section V. Still further, in certain embodiments, the adhesive composition may further comprise a reactive prepolymer, such as a reactive prepolymer described below in Section VII.

The particular hydroxyaromatic compound may be selected to achieve certain performance properties. Exemplary classes of hydroxyaromatic compounds include alkyl-substituted phenols, aryl-substituted phenols, cycloalkyl-substituted phenols, alkenyl-substituted phenols, alkoxy-substituted phenols, aryloxy-substituted phenols and halogen-substituted phenols. Exemplary specific hydroxyaromatic compounds include phenol, o-cresol, m-cresol, p-cresol, 3,5-xylenol, 3,4-xylenol, 2,3,4-trimethylphenol, 3-ethylphenol, 3,5-diethylphenol, p-butylphenol, 3,5-dibutylphenol, p-amyl phenol, p-cyclohexyl phenol, p-octyl phenol, 3,5 dicyclohexylphenol, p-phenylphenol, p-crotylphenol, 3,5-dimethoxyphenol, 3,4,5-trimethoxyphenol, p-ethoxyphenol, p-butoxyphenol, 3-methyl-4-methoxyphenol, p-phenoxyphenol, resorcinol, and naphthol. In certain embodiments, the hydroxyaromatic compound is phenol.

Various aldehyde source compounds are reported in the literature and are contemplated to be amenable for use in the present invention. For example, in certain embodiments, the aldehyde source is an aldehyde compound or para-formaldehyde. Exemplary classes of aldehyde compounds include an alkyl monoaldehyde, an alkyl dialdehyde, a hydroxyalkyl monoaldehyde, a hydroxyalkyl dialdehyde, an acyl monoaldehyde, and an acyl dialdehyde. Exemplary specific aldehyde compounds include formaldehyde, acetaldehyde, glyoxal, methyl glyoxal, glycoaldehyde, propanedial, propionaldehyde, butyraldehyde, pentanal, hexanal, dodecanal, octadecanal, cinnamaldehyde, furfuraldehyde, benzaldehyde, and glutaraldehyde. In certain embodiments, the aldehyde source is formaldehyde (i.e., HC(O)H), such as in the form of formaldehyde gas. In certain other embodiments, the aldehyde source is para-formaldehyde (“paraform”). Alternatively, chemicals found in wood can serve as a source of formaldehyde, and, as such, wood can be an aldehyde source.

The ratio of aldehyde source to hydroxyaromatic compound in the adhesive composition may be adjusted to achieve certain performance properties. For example, in certain embodiments, the mole ratio of aldehyde source to hydroxyaromatic compound is from about 0.5:1 to about 4:1, about 1.5:1 to about 3.5:1, or about 1.5:1 to about 2.5:1. In certain other embodiments, the mole ratio of aldehyde source to hydroxyaromatic compound is from about 1:2 to about 2:1. In certain other embodiments, the hydroxyaromatic compound is phenol, the aldehyde source is formaldehyde, and the mole ratio of formaldehyde to phenol is from about 1:2 to about 2:1.

In certain embodiments, the hydroxyaromatic compound and aldehyde source together constitute from about 0.5% w/w to about 10% w/w, about 1% w/w to about 8% w/w, about 1% w/w to about 5% w/w, or about 2% w/w to about 5% w/w of the adhesive composition. In certain embodiments, the plant protein composition is present in an amount ranging from about 5% w/w to about 40% w/w, about 10% w/w to about 30% w/w, or about 15% w/w to about 25% w/w of the adhesive composition. In embodiments where the adhesive composition further comprises a reactive prepolymer, the reactive prepolymer may be present in an amount ranging from about 5% w/w to about 40% w/w, about 10% w/w to about 30% w/w, or about 15% w/w to about 25% w/w of the adhesive composition.

The hydroxyaromatic-aldehyde protein adhesive compositions may optionally further comprise a catalyst to facilitate polymerization. Exemplary catalysts include bases such as sodium hydroxide, caustic soda, potassium hydroxide, caustic potash, calcium hydroxide, tetraalkyl ammonium hydroxides, barium hydroxide, and other basic alkaline salts such as alkali metal carbonate. Other exemplary catalysts include (i) mineral acids, such as hydrochloric acid, hydrobromic acid, perchloric acid, sulfuric acid, and nitric acid; (ii) sulfonic acids, such as methanesulfonic acid, ethanesulfonic acid, cyclohexanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethane sulfonic acid, and camphorsulfonic acid; and (iii) organic acids, such as formic acid, acetic acid, propionic acid, cyclohexanecarboxylic acid, oxalic acid, malonic acid, maleic acid, fumaric acid, citric acid, tartaric acid, and 3-mercaptopropionic acid.

In certain embodiments, the adhesive composition further comprises water. For example, in certain embodiments, water is present in an amount of from about 30% w/w to about 65% w/w of the adhesive composition. In certain other embodiments, water is present in an amount of from about 20% w/w to about 50% w/w, about 30% w/w to about 60% w/w, about 40% w/w to about 70% w/w, about 50% w/w to about 80% w/w, or about 10% w/w to about 90% w/w of the adhesive composition.

A more specific embodiment relates to a phenol-formaldehyde-plant protein adhesive composition that comprises: (a) phenol; (b) formaldehyde; (c) a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition; and (d) a reactive prepolymer; wherein the ratio of (i) weight percent of reactive prepolymer in the adhesive composition to (ii) the sum of the weight percent of phenol and formaldehyde in the adhesive composition is greater than 1:1. In certain embodiments, the ratio of (i) weight percent of reactive prepolymer in the adhesive composition to (ii) the sum of the weight percent of phenol and formaldehyde in the adhesive composition is in the range of about 3:1 to about 20:1. In certain embodiments, the ratio of (i) weight percent of reactive prepolymer in the adhesive composition to (ii) weight percent plant protein composition in the adhesive composition is in the range of about 4:1 to about 1:4. In certain embodiments, the composition further comprises water, such as where the water is present in an amount ranging from about 45% w/w to about 75% w/w of the adhesive composition. In certain embodiments, the composition further comprises urea (i.e., H2NC(O)NH2), such as where the urea is present in an amount ranging from about 0.5% w/w to about 5% w/w of the adhesive composition.

Exemplary reactive prepolymers are described in Section VII below. In certain embodiments, the reactive prepolymer is a polyisocyanate-based prepolymer, an epoxy-based prepolymer, a latex-based prepolymer, a latex prepolymer, or a combination thereof. In certain other embodiments, the reactive prepolymer is a polyisocyanate-based prepolymer. In certain other embodiments, the polyisocyanate-based prepolymer is an organic polyisocyanate; or a reaction product between an organic polyisocyanate and a polypeptide, a polyol, an amine based polyol, an amine containing compound, a hydroxy containing compound, or a combination thereof. In certain other embodiments, the reactive prepolymer is polymeric diphenylmethane diisocyanate.

In certain embodiments, the plant protein composition is ground plant meal.

Another more specific embodiment relates phenol-formaldehyde-plant protein adhesive composition that comprises: (a) phenol and formaldehyde that together constitute from about 0.5% w/w to about 10% w/w of the adhesive composition; (b) ground plant meal in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; (c) polymeric diphenylmethane diisocyanate in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; and (d) water in an amount ranging from about 45% w/w to about 75% w/w of the adhesive composition. In certain embodiments, the composition further comprises urea (i.e., H2NC(O)NH2) in an amount ranging from about 0.5% w/w to about 5% w/w of the adhesive composition. In certain embodiments, the ratio of (i) weight percent of polymeric diphenylmethane diisocyanate in the adhesive composition to (ii) the sum of the weight percent of phenol and formaldehyde in the adhesive composition is in the range of about 2:1 to about 5:1. In certain embodiments, the ratio of (i) weight percent of polymeric diphenylmethane diisocyanate in the adhesive composition to (ii) weight percent plant protein composition in the adhesive composition is in the range of about 3:1 to about 1:2.

Another more specific embodiment relates phenol-formaldehyde-plant protein adhesive composition that comprises: (a) phenol and para-formaldehyde that together constitute from about 0.5% w/w to about 10% w/w of the adhesive composition; (b) ground plant meal in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; (c) polymeric diphenylmethane diisocyanate in an amount ranging from about 10% w/w to about 30% w/w of the adhesive composition; and (d) water in an amount ranging from about 45% w/w to about 75% w/w of the adhesive composition. In certain embodiments, the composition further comprises urea (i.e., H2NC(O)NH2) in an amount ranging from about 0.5% w/w to about 5% w/w of the adhesive composition. In certain embodiments, the ratio of (i) weight percent of polymeric diphenylmethane diisocyanate in the adhesive composition to (ii) the sum of the weight percent of phenol and para-formaldehyde in the adhesive composition is in the range of about 2:1 to about 5:1. In certain embodiments, the ratio of (i) weight percent of polymeric diphenylmethane diisocyanate in the adhesive composition to (ii) weight percent plant protein composition in the adhesive composition is in the range of about 3:1 to about 1:2.

Another aspect of the invention provides a urea compound-aldehyde protein adhesive composition. The adhesive composition comprises a urea compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition.

The adhesive composition may further comprise one or more additives, such as the additives described in Section VIII below, which include, for example, an intercalated clay, an exfoliated clay, and a partially exfoliated clay. Further, the adhesive composition may comprise lignin, such as a lignin described below in Section V. Still further, in certain embodiments, the adhesive composition may further comprise a reactive prepolymer, such as a reactive prepolymer described below in Section VII.

The particular urea compound may be selected to achieve certain performance properties. Exemplary classes of urea compounds include alkyl ureas, aralkyl ureas, aryl ureas, mono-methylolurea, a di-methylolurea, a tri-methylolurea, and substituted noncyclic ureas. Exemplary specific urea compounds include H2NC(O)NH2, ethylene urea, propylene urea, tetrahydro-5-(2-hydroxyethyl)-1,3,5-triazin-2-one, 4,5-dihydroxy-2-imidazolidone, 4,5-dimethoxy-2-imidazolidinone, 4-methyl ethylene urea, 4-ethyl ethylene urea, 4-hydroxyethyl ethylene urea, 4,5-dimethyl ethylene urea, 4-hydroxy-5-methyl propylene urea, 4-methoxy-5-methyl propylene urea, 4-hydroxy-5,5-dimethyl propylene urea, 4-methoxy-5,5-dimethyl propylene urea, tetrahydro-5-(ethyl)-1,3,5-triazin-2-one, tetrahydro-5-(propyl)-1,3,5-triazin-2-one, tetrahydro-5-(butyl)-1,3,5-triazin-2-one, dihydro-5-methyl-2(1H, 3H)pyrimidinone, dihydro-5,5-dimethyl-2 (1H)pyrimidinone, tetrahydro-4,5-methyl-2(1H) pyrimidinone, and tetrahydro-4-(2-hydroxyethyl)-5,5-dimethyl-2(1H) pyrimidinone. Additional urea compounds include those represented by RN(H)C(O)NH2, R2NC(O)NH2, or RN(H)C(O)N(H)R, wherein R represents independently for each occurrence H, alkyl, aryl, or aralkyl. In certain embodiments, the urea compound has the formula RN(H)C(O)N(H)R, wherein R represents independently for each occurrence H, alkyl, aryl, or aralkyl. In certain other embodiments, the urea compound is H2NC(O)NH2, H2NC(O)N(H)Me, MeN(H)C(O)N(H)Me, or H2NC(O)N(CH3)2. In certain other embodiments the urea compound is [CH3CH2N(H)]2C(O), [(CH3)2N]2C(O), or CH3CH2N(H)C(O)NH2. In still other embodiments, the urea compound is H2NC(O)NH2.

Various aldehyde source compounds are reported in the literature and are contemplated to be amenable for use in the present invention. For example, in certain embodiments, the aldehyde source is an aldehyde compound or para-formaldehyde. Exemplary classes of aldehyde compounds include an alkyl monoaldehyde, an alkyl dialdehyde, a hydroxyalkyl monoaldehyde, a hydroxyalkyl dialdehyde, an acyl monoaldehyde, and an acyl dialdehyde. Exemplary specific aldehyde compounds include formaldehyde, acetaldehyde, glyoxal, methyl glyoxal, glycoaldehyde, propanedial, propionaldehyde, butyraldehyde, pentanal, hexanal, dodecanal, octadecanal, cinnamaldehyde, furfuraldehyde, benzaldehyde, and glutaraldehyde. In certain embodiments, the aldehyde source is formaldehyde (i.e., HC(O)H), such as in the form of formaldehyde gas. In certain other embodiments, the aldehyde source is para-formaldehyde (“paraform”). Alternatively, chemicals found in wood can serve as a source of formaldehyde, and, as such, wood can be an aldehyde source.

The ratio of aldehyde source to urea compound in the adhesive composition may be adjusted to achieve certain performance properties. For example, in certain embodiments, the mole ratio of aldehyde source to urea compound is from about 0.5:1 to about 4:1, about 1.5:1 to about 3.5:1, or about 1.5:1 to about 2.5:1.

The urea compound-aldehyde protein adhesive compositions may optionally further comprise a catalyst to facilitate polymerization. Exemplary catalysts include Lewis acids, Bronsted acids, ammonium salts, substituted ammonium salts, or a combination thereof. In certain embodiments, the catalyst is AlCl3, AlBr3, Al2(SO4)3, MgCl2, MgBr2, Ca, Sr, Ti, Fe, Zn, Sn, Sb, Zr, Hg, TI, Pb, Bl, HCl, H2SO4, HNO3, H3PO4, or HClO4.

Another aspect of the invention provides an amine compound-aldehyde adhesive composition. The adhesive composition comprises an amine compound selected from the group consisting of a primary amine compound and a secondary amine compound, an aldehyde source, and a plant protein composition selected from the group consisting of ground plant meal and isolated polypeptide composition.

The adhesive composition may further comprise one or more additives, such as the additives described in Section VIII below, which include, for example, an intercalated clay, an exfoliated clay, and a partially exfoliated clay. Further, the adhesive composition may comprise lignin, such as a lignin described below in Section V. Still further, in certain embodiments, the adhesive composition may further comprise a reactive prepolymer, such as a reactive prepolymer described below in Section VII.

The particular amine compound may be selected to achieve certain performance properties. In certain embodiments, the amine compound is a primary amine compound, such as a primary alkyl amine, primary arylamine, primary heteroarylamine, or primary aralkyl amine. In certain embodiments, the amine compound is melamine.

Various aldehyde source compounds are reported in the literature and are contemplated to be amenable for use in the present invention. For example, in certain embodiments, the aldehyde source is an aldehyde compound or para-formaldehyde. Exemplary classes of aldehyde compounds include an alkyl monoaldehyde, an alkyl dialdehyde, a hydroxyalkyl monoaldehyde, a hydroxyalkyl dialdehyde, an acyl monoaldehyde, and an acyl dialdehyde. Exemplary specific aldehyde compounds include formaldehyde, acetaldehyde, glyoxal, methyl glyoxal, glycoaldehyde, propanedial, propionaldehyde, butyraldehyde, pentanal, hexanal, dodecanal, octadecanal, cinnamaldehyde, furfuraldehyde, benzaldehyde, and glutaraldehyde. In certain embodiments, the aldehyde source is formaldehyde (i.e., HC(O)H), such as in the form of formaldehyde gas. In certain other embodiments, the aldehyde source is para-formaldehyde (“paraform”). Alternatively, chemicals found in wood can serve as a source of formaldehyde, and, as such, wood can be an aldehyde source.

The ratio of aldehyde source to amine compound in the adhesive composition may be adjusted to achieve certain performance properties. For example, in certain embodiments, the mole ratio of aldehyde source to amine compound is from about 0.5:1 to about 4:1, about 1.5:1 to about 3.5:1, or about 1.5:1 to about 2.5:1.

Lignin is a polyphenolic polymer that can be isolated from wood. Lignin can be characterized according to the natural source from which it is obtained. In addition, lignin can be characterized according to physical properties such as solubility, molecular weight, temperature stability, salt tolerance, surface tension, sulphonic sulphur content, presence of cations, quantity of calcitrant, its phenoxy radical signal, and amount of p-hydroxyphenyl, guaiacyl, and/or synringal moieties in its structure.

One type of lignin contemplated to be amenable for use in the adhesive compositions described herein is lignin obtained from hardwood trees, such as Acacia, Afzelia, Synsepalum duloificum, Albizia, Alder, Applewood, Arbutus, Ash, Aspen, Australian Red Cedar, Ayna, Balsa, Basswood, Beech, Birch, Blackbean, Blackwood, Bocote, Boxelder, Boxwood, Brazilwood, Bubing a, Buckeye, Butternut, Catalpa, Chemy, Crabwood, Chestnut, Coachwood, Cocobolo, Corkwood, Cottonwood, Cucumbertree, Dogwood, Ebony, Elm, Eucalyptus, Greenheart, Grenadilla, Gum, Hickory, Hornbeam, Hophombeam, Ipe, Iroko, Ironwood, Jacaranda, Jotoba, Lacewood, Laurel, Limba, Lignum vitae, Locust, Mahogany, Maple, Meranti, Mpingo, Oak, Obeche, Okoume, Oregon Myrtle, California Bay Laurel, Pear, Poplar, Ramin, Red cedar, Rosewood, Sal, Sandalwood, Sassafras, Satinwood, Silky Oak, Silver Watde, Snakewood, Sourwood, Spanish cedar, American sycamore, Teak, Walnut, Willow, Yellow poplar, Bamboo, and Palmwood.

Another type of lignin contemplated to be amenable for use in the adhesive compositions described herein is lignin obtained from softwood trees, such as Araucaria, softwood Cedar, Cypress, Rocky Mountain Douglas fir, European Yew, Fir, Hemlock, Kauri, Kaya, Larch, Pine, Redwood, Rimu, Spruce, and Sugi.

Another type of lignin contemplated to be amenable for use in the adhesive compositions described herein is lignin obtained from annual fibre, such as flax, wheat, barley, oats, sugarcane bagasse, rice straw, corn stover, hemp, fruit pulp, alfa grass, switchgrass, corn cobs, and fruit peals.

Another type of lignin contemplated to be amenable for use in the adhesive compositions described herein is lignin having one or more of the following physical properties: (i) a weight average molecular weight of about 1,000 g/mol to about 100,000 g/mol, about 10,000 g/mol to about 70,000 g/mol, or about 5,000 to about 50,000; (ii) a temperature stability of about 50° C. to about 400° C., about 70° C. to about 250° C., or about 90° C. to about 200° C.; (iii) a salt tolerance of less than 0.1% precipitate in a salt solution containing sodium chloride, magnesium chloride, and/or calcium chloride with concentrations of about 70 ppm to about 270 ppm total dissolved solids; (iv) when mixed with water to produce a 1% aqueous solution, the aqueous solution has a surface tension of 35 to 75 dynes/cm; and (v) has a phenoxy radical signal of about 500 gauss to about 5,000 gauss, about 1000 gauss to about 3000 gauss, or about 2000 gauss to about 4000 gauss. In certain embodiments, the lignin has one or more of the following physical properties: (i) at least 20% by weight p-hydroxyphenyl, (ii) at least 40% by weight p-hydroxyphenyl, (iii) at least 20% by weight guaiacyl, (iv) at least 40% by weight guaiacyl, (v) at least 20% by weight synringal, and (vi) at least 40% by weight synringal.

Lignin can be isolated from wood and annual fibre using procedures reported in the literature. Exemplary isolation procedures include sulfite pulping, the Kraft process, organosolv pulping (e.g., ASAM organosolv pulping), acid hydrolysis, soda pulping, steam explosion, Alcell® pulping, Organocell pulping, and Acetosolv pulping. In particular, the sulphate, sulphite, ORGANOSOLV and MILOX processes can be used to isolate lignin. Isolation procedures described in the literature can also be used to obtain lignin sulfonates (also known as lignosulphonates and sulfite lignins), kraft lignins (also called sulfate lignins), alkali lignins, and oxylignins.

The plant protein composition is derived from plant biomass and, as such, provides the benefit that it is a renewable feedstock. The plant protein composition may be ground plant meal or an isolated polypeptide composition as described in more detail below.

A. Ground Plant Meal

Plant meal can be obtained from commercial sources or derived from corn, wheat, sunflower, cotton, rapeseed, canola, castor, soy, camelina, flax, jatropha, mallow, peanuts, algae, sugarcane bagasse, tobacco, whey, or a combination thereof. Plant meal can be ground using techniques known in the art, such as hammer mill (cryogenic or ambient) or ball mill. In certain embodiments, the plant meal is ground and screened to isolate plant meal particles having a particle size in the range of from about 1 μm to about 400 μm, from about 1 μm to about 350 μm, from about 1 μm to about 300 μm, from about 1 μm to about 250 μm, from about 1 μm to about 200 μm, from about 1 μm to about 100 μm, from about 1 μm to about 50 μm, from about 5 μm to about 250 μm, from about 5 μm to about 200 μm, from about 5 μm to about 150 μm, from about 5 μm to about 100 μm, from about 5 μm to about 50 μm, from about 10 μm to about 250 μm, from about 10 μm to about 100 μm, from about 10 μm to about 90 μm, from about 10 μm to about 70 μm, from about 10 μm to about 50 μm, from about 20 μm to about 150 μm, from about 20 μm to about 100 μm, from about 20 μm to about 80 μm, from about 20 μm to about 70 μm, from about 20 μm to about 60 μm, from about 25 μm to about 150 μm, from about 25 μm to about 100 μm, from about 25 μm to about 50 μm, from about 50 μm to about 150 μm, or from about 50 μm to about 100 μm. In certain embodiments, the plant meal is ground and has a particle size in the range of from about 1 μm to about 200 μm. In certain other embodiments, the plant meal is ground and has a particle size in the range of from about 1 μm to about 100 μm,

Preferred types of ground plant meal are characterized by their ability to suspend or emulsify oil in water or water in oil to produce a homogeneous suspension or emulsion stable, by visual inspection, for least 5 minutes. In certain embodiments, the dispersion or emulsion exhibits substantially no phase separation by visual inspection for at least 10, 15, 20, 25, or 30 minutes, or even 1, 2, 3, 4, 5, 6, 9, 12, 18, or 24 hours after mixing the ground plant meal with the oil. One assay that can be used to identify such preferred ground plant meals involves mixing 26 parts (by weight) of a ground plant meal sample with 74 parts (by weight) of water. The resulting solution or dispersion is mixed with 26 parts (by weight) of oil, for example, PMDI. Under these conditions, the ground plant meal produces a dispersion or emulsion that exhibits substantially no phase separation by visual inspection for at least 5 minutes after mixing the ground plant meal with the oil. This assay can be performed with oils other than PMDI, such as mineral oil, soybean oil, derivatized soybean oil, motor oil, castor oil, derivatized castor oil, dibutyl phthalate, epoxidized soybean oil, corn oil, vegetable oil, caprylic triglyceride, Eucalyptus oil, tributyl o-acetylcitrate, or an organic polyisocyanate other than PMDI.

An additive may be added to the plant meal prior to grinding to aid in the grinding process or produce a ground plant meal with superior physical properties for use in manufacturing an adhesive composition, e.g., providing a ground plant meal with improved flow properties, superior packing density, reduced tendency to cake, reduced tendency to bridge, superior particle dispersibility in aqueous mixtures, modulation of particle coupling and/or wetting characteristics with other materials in the adhesive composition, and the like. Alternatively, the additive may be added to the plant meal during the grinding process used to produce ground plant meal.

Additives that impart superior performance properties to the adhesive composition or the wood composite formed from the adhesive composition may be added to the plant meal before or during grinding or may be added to the ground plant meal produced from the grinding process. Exemplary additives include those described in sections below, and, in particular, include agents that improve moisture resistance of the wood composite, formaldehyde scavenging agents, and composite-release promoting agents. The additive may be in solid or liquid form, and the additive may be characterized according to whether it reacts with materials in the adhesive composition or does not react with materials in the adhesive composition.

Exemplary solid additives include (i) inorganic additives such as silica, pigments, catalysts, clays (including intercalated clays, exfoliated clays, and partially exfoliated clays), and the like, and (ii) organic compounds such as fatty acids (e.g., stearic acid, lauric acid) lignin, tannins, amine-containing compounds, urea, hydrocarbon waxes/liquids, and fluorocarbon waxes/liquids. Solid additives may be used in amounts ranging, for example, from about 0.001% w/w to 40% w/w of the ground plant meal mixture, from about 0.1% w/w to about 20% w/w of the ground plant meal mixture, or from about 0.5% w/w to about 15% w/w of the ground plant meal mixture.

Liquid additives may be dry blended with ground plant meal. The amount of liquid additive should be less than that which causes the ground plant meal to cake or bridge during a manufacturing process. Accordingly, in certain embodiments, the amount of liquid additive(s) is less than about 10% by weight of the ground plant meal mixture containing the additive(s). In certain other embodiments, the amount of liquid additive(s) is less than about 5% by weight, or even less than about 2% by weight, of the ground plant meal mixture containing the additive. The liquid additive may be characterized as reactive or non-reactive. Reactive liquid additives may include organosilanes, low molecular weight alcohols such as glycerin or propylene glycol, liquid polyol oligomers, liquid polyurethane oligomers, addition-polymerizable monomers, condensation-polymerizable monomers, and reactive oils such as epoxidized soy oil or castor oil. Other liquid additives include amalgams of a carrier oil and a partially exfoliated clay as described herein.

B. Isolated Polypeptide Composition

The isolated polypeptide composition can be derived from renewable plant biomass, such as corn, wheat, sunflower, cotton, rapeseed, canola, castor, soy, camelina, flax, jatropha, mallow, peanuts, algae, sugarcane bagasse, tobacco, whey, or a combination thereof, using procedures described herein. The isolated polypeptide composition contains water-insoluble/water-dispersible protein fraction, optionally in combination with a water-soluble protein fraction. It is understood that the water-insoluble/water-dispersible protein fraction can disperse oils (for example, reactive oils, or an organic polyisocyanate, which is a reactive prepolymer). Thus, in embodiments where the isolated polypeptide composition contains a mixture of i) water-insoluble/water-dispersible protein fraction and ii) water-soluble protein fraction, the ratio of i) water-insoluble/water-dispersible protein fraction to ii) water-soluble protein fraction is such that the isolated polypeptide composition is able to disperse a prepolymer in an aqueous medium.

The terms “protein” and “polypeptide” are used synonymously and refer to polymers containing amino acids that are joined together, for example, via peptide bonds or other bonds, and may contain naturally occurring amino acids or modified amino acids. The polypeptides can be isolated from natural sources or synthesized using standard chemistries. The polypeptides may be modified or derivatized by either natural processes, such as post-translational processing, or by chemical modification techniques well known in the art. Modifications or derivatizations may occur anywhere in the polypeptide, including, for example, the peptide backbone, the amino acid side-chains and the amino or carboxyl termini. Modifications include, for example, cyclization, disulfide bond formation, demethylation, deamination, formation of covalent cross-links, formation of pyroglutamate, formylation, gamma-carboxylation, glycosylation, GPI anchor formation, hydroxylation, iodination, methylation, myristolyation, oxidation, pegylation, proteolytic digestion, phosphorylation, etc. As used throughout, the term “isolated” refers to material that is removed from its original environment (e.g., the natural environment if it is naturally occurring).

1. Preparation of Isolated Polypeptide Composition

The starting material for producing an isolated polypeptide composition can be derived from one or more of corn, wheat, sunflower, cotton, rapeseed, canola, castor, soy, camelina, flax, jatropha, mallow, peanuts, algae, sugarcane bagasse, tobacco, or whey. For example, the starting material for producing an isolated polypeptide composition can be plant meal or a protein isolate. Depending on the properties desired for the adhesive, the isolated polypeptide composition may contain a mixture of i) water-insoluble/water-dispersible protein fraction and ii) water-soluble protein fraction. The water-insoluble/water-dispersible protein fraction and the water-soluble protein fraction can be obtained from plant material using a Water Washing Method or an Acid Precipitation Method, such as those described in more detail below. In certain instances, the composition obtained from the Water Washing Method and or Acid Precipitation Method may be further modified by enzymatic digestion and/or chemical modification.

Water-insoluble/water-dispersible protein fraction can be isolated from plant meal (e.g., castor meal, soy meal, or canola meal) by washing with water to remove water-soluble proteins and water-soluble components. The residue left after the water wash is the water-insoluble/water-dispersible protein fraction. A water-soluble protein fraction can be isolated by concentrating aqueous extracts from the water washing. Plant meal used in the process can be ground to reduce particle size, which may, in certain instances, provide processing advantages.

Water-insoluble/water-dispersible protein fraction can also be isolated from, for example, soy protein isolate or from soy flour. The procedure involves washing the soy protein isolate or soy flour with water to remove water-soluble proteins and water-soluble components from the respective soy protein isolate or the water-flour mixture.

The water-insoluble/water-dispersible protein fraction described above may be used directly as a wet slurry in an adhesive composition, or it may be dried and optionally ground to form a particulate mixture.

In certain embodiments, the pH of the water used to wash the plant meal is about 7. In certain other embodiments, the pH of the water used to perform one or more of the washes may be alkaline. Conditions (e.g., number of water washes) for the Water Washing Method may be adjusted in order to maximize the performance properties of the water-insoluble/water-dispersible protein fraction, such as its ability to disperse an oil in water or water in oil.

The Water Washing Method is a simple and economical procedure for obtaining water-insoluble/water-dispersible protein fraction. Due to the simplicity of the method, it is contemplated that the Water Washing Method can be used to provide large quantities of water-insoluble/water-dispersible protein fraction for manufacture of adhesive compositions.

It is appreciated that the water-insoluble/water-dispersible protein fraction obtained using the Water Washing Method may, in certain instances, contain water-insoluble components in addition to water-insoluble protein. If the performance requirements of an adhesive require a water-insoluble/water-dispersible protein fraction having a larger amount of water-insoluble protein, then the Acid Precipitation Method can be used to prepare the water-insoluble/water-dispersible protein fraction.

Water-insoluble/water-dispersible protein fraction comprising a relatively higher quantity of water-insoluble protein can be prepared using the Acid Precipitation Method. The Acid Precipitation Method is shown schematically in FIG. 1. This method can also be used to obtain water-soluble protein fraction.

As shown in FIG. 1, the starting material (for example, ground meal) is dispersed in alkaline, aqueous media at pH 6.5-13 for at least 5 minutes, at least 20 minutes, at least 40 minutes or at least 1 hour, to form a mixture. Starting materials include, for example, canola meal, canola protein isolate, castor meal, castor protein isolate, soy meal, or soy protein isolate, or a combination thereof. Then, the pH of the mixture is lowered by the addition of acid (to provide a mixture with a pH in the range of, for example, 4.0-5.0) to precipitate both a portion of water-soluble proteins and water-insoluble proteins. Then, the water-insoluble material (i.e., the precipitate) is harvested. The harvested material is washed with water and the remaining water-insoluble/water-dispersible material is harvested. The resulting water-insoluble/water-dispersible material can be used as is or dried using drying techniques known in the art.

Further, as shown in FIG. 1, the water-soluble proteins can be harvested at a number of places. For example, water-soluble proteins can be harvested after the starting material is mixed in aqueous media, after neutralization, and as a supernatant from the washing steps. The resulting protein can be used as is or dried using drying techniques known in the art.

The water-insoluble/water-dispersible material produced according to the method in FIG. 1 can disperse or emulsify oil in water or water in oil. The physical and chemical properties of the water-soluble/water-dispersible fraction are described in more detail below. In addition, the physical and chemical properties of the water-soluble protein fraction are described in more detail below.

The Water Washing Method and Acid Precipitation Method can include one or more enzyme digestion and/or chemical hydrolysis steps. Digestion can be facilitated using one or more enzymes, and hydrolysis can be facilitated using one or more chemicals, for example, acid- or alkali-based hydrolysis. For example, in the Acid Precipitation Method, the starting material (for example, the ground meal) can be exposed to enzymatic digestion before or after, or both before and after the incubation of the starting material in the alkaline aqueous media. Alternatively, or in addition, an enzymatic digestion step can be performed on the material following addition of acid to provide a mixture with a pH in the range of 4.0 to 5.0. Alternatively, or in addition, the harvested water-insoluble/water-dispersible material can be exposed to enzymatic digestion prior to washing. Alternatively, or in addition, the material harvested after washing can be exposed to enzymatic digestion. Chemical hydrolysis, however, can occur with or replace the enzymatic digestion steps noted above.

Under certain circumstances residual basic species and alkali metals present in chemically digested proteins are not compatible with polyisocyanates and can cause trimerization of the isocyanate groups, leading to stability problems in the final polyisocyanate compositions. Enzymatic digestion, however, can be used to avoid or reduce isocyanate stability problems associated with some chemical hydrolysis steps.

It is understood that enzymes useful in the digestion of the protein fractions include endo- or exo-protease of bacterial, fungal, animal or vegetable origin or a mixture of thereof. Useful enzymes include, for example, a serine-, leucine-, lysine-, or arginine-specific protease. Exemplary enzymes include trypsin, chymotrypsins A, B and C, pepsin, rennin, microbial alkaline proteases, papain, ficin, bromelain, cathepsin B, collagenase, microbial neutral proteases, carboxypeptidases A, B and C, camosinase, anserinase, V8 protease from Staphylococcus aureus and many more known in the art. Also combinations of these proteases may be used.

Also commercially available enzyme preparations such as, for example, Alcalase®, Chymotrypsine 800s, Savinase®, Kannase®, Everlase®, Neutrase®, Flavourzyme® (all available from Novo Nordisk, Denmark), Protex 6.0L, Peptidase FP, Purafect®, Purastar OxAm®, Properase® (available from Genencor, USA), Corolase L10 (Rohm, Germany), Pepsin (Merck, Germany), papain, pancreatin, proleather N and Protease N (Amano, Japan), BLAP and BLAP variants available from Henkel, K-16-like proteases available from KAO, or combinations thereof. Table 1 describes the amino acid specificity of certain useful endonucleases.

TABLE 1 No. Amino Acid Notation Commercial Endopeptidase(s) 1 Alanine A Pronase ®; Neutrase ®: 2 Cysteine C Papain 3 Aspartic D Fromase ®; 4 Glutamic E Alcalase ®; 5 Phenylalanine F Neutrase ®: Fromase ® 6 Glycine G Flavorzyme ®; Neutrase ®: 7 Histidine H Properase ®; 8 Isoleucine I Neutrase ®: 9 Lysine K Alcalase ®; Trypsin ®; Properase ® 10 Leucine L Alcalase ®; Esperase ®; Neutrase ®: 11 Methionine M

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