SELF-RELEASING BINDER SYSTEM FOR COMPOSITE PRODUCTS

Abstract: A composition is disclosed for a self-releasing binder composition useful for preparing a composite article prepared by contacting at least (1) a polyisocyanate compound, (2) a compound of one of formulae (I), (II), (III) in an amount from about 1 to about 20 parts per 100 parts by weight of the polyisocyanate compound, wherein X is oxygen or sulfur, R is hydrocarbyl or hydrocarbyl containing an ether or ester group, and may be cyclic, and R' is R, H, or an acyl, carbamoyl, phosphoryl or sulfonyl group; and (3) a polyether containing compound, with the following provisos: (i) wherein the polyether containing compound contains no active hydrogen, the polyether containing compound is present in an amount from about 1 to about 2000 parts per 100 parts by weight of the polyisocyanate; and (ii) wherein the polyether containing compound contains at least one active hydrogen, the polyether containing compound is present in an amount such that, for compounds of formula (I) the OH:NCO equivalency ratio is less than about 0.77:1.00; for compounds of formula (II), the OH:NCO equivalency ratio is less than about 0.25:1.00; and for compounds of formula (III), the OH:NCO equivalency ratio is less than about 0.10:1.00; under reaction conditions sufficient to form a binder composition. The components which make up the self-releasing binder composition can be applied to substrate particles, which may be, for example, cellulosic, polymeric, inorganic, or similar particles, or combinations thereof. This composition provides excellent adhesion of the particles while at the same time offering easy and dependable releasability from a wide variety of metal surfaces.

Description: SELF-RELEASING BINDER SYSTEM FOR COMPOSITE PRODUCTS This invention relates *-o binders useful in preparing composite products. More particularly, it relates to composite products prepared from comminuted, preferably lignocellulosic, materials. The use of organic polyisocyanates as adhesive binders in preparing board products from comminuted Woodstock, including wood flakes, chips, strands or fibers, is well-known. References to such use include, for example, U.S. Patents Nos. 3,428,592; 3,440,180; 3,557,263; 3,636,199; 3,870,665; 3,919,017; and 3,930,110. In a typical process the binder resins, optionally in the form of a solution or aqueous suspension or emulsion, are applied to or admixed with the particles of cellulosic material, or other types of substrate material capable of forming composite articles, using a tumbler apparatus, blender or other form of agitator. The mixture of particles and binder is then formed into a mat and subjected to heat and pressure using heated platens. The process can be carried out in a batch operation or continuously. To avoid adhesion of the composite board or other article to the heated platens, it has hitherto been necessary to interpose a sheet, impermeable to isocyanate, between the surface of the board and the platen during the forming process, or to coat the surface of the platen, prior to each molding operation, with an appropriate release agent. Another approach has been to coat the surface of the particles themselves with a material which will not adhere to the platen. Any of these choices, particularly where the process is being operated on a continuous basis, is cumbersome and a drawback to what is otherwise a very satisfactory method of making the composite article with highly attractive structural strength properties. To obtain release it has also been suggested that an acid phosphate be added to the isocyanate compound as an "internal release agent", as described in U.S. Patent 4,257,995. This system appears to provide release from aluminum platens, but has shown extremely poor release from steel. Other mold release systems suffering similar disadvantages include use of a polymerized fatty acid and/or a polycarboxyl compound containing a polymeric fatty radical in conjunction with an isocyanate, as disclosed in U.S. Patent 4,933,232, or a sulfonic acid in conjunction with an isocyanate, as disclosed in U.S. Patent 4,528,153. Thus, it would be desirable to develop a binder system that provides good adhesion of the particles to be adhered, while also exhibiting good release from a wide variety of metal platens. Summary of the Invention Accordingly, the present invention is a self-releasing binder composition prepared by contacting at least (1) a polyisocyanate compound, (2) a compound of one of the following formulae in an amount from about 1 to about 20 parts per 100 parts by weight of the polyisocyanate compound: X 0 o I II II R0 p — OH R — c —OH R — S —OH I II OR' ° (I) (ID (III) wherein X is oxygen or sulfur, R is hydrocarbyl or hydrocarbyl containing an ether or ester group, and may be cyclic, and R 1 is R, H, or an acyl, carbamoyl, phosphoryl or sulfonyl group; and (3) a polyether containing compound, with the following provisos: (i) wherein the polyether containing compound contains no active hydrogen, the polyether containing compound is present in an amount from about 1 to about 2000 parts per 100 parts by weight of the polyisocyanate; and (ii) wherein the polyether containing compound contains at least one active hydrogen, the polyether containing compound is present in an amount such that, for compounds of Formula I, the OH:NCO equivalency ratio is less than about 0.77:1.00; for compounds of Formula II, the OH:NCO equivalency ratio is less than about 0.25:1.00; and for compounds of Formula III, the OH:NCO equivalency ratio is less than about 0.10:1.00; under reaction conditions sufficient to form a binder composition. In another embodiment the present invention is a process for preparing a composite article comprising contacting at least (1) a polyisocyanate compound; (2) a compound of one of the following formulae in an amount from about 1 to about 20 parts per 100 parts by weight of the polyisocyanate: II RO OH • OH 'OH II OR' (i) (II) < **• - wherein X is oxygen or sulfur, R is hydrocarbyl or hydrocarbyl containing an ether or ester group, and may be cyclic, and R' is R, H, or an acyl, carbamoyl, phosphoryl or sulfonyl group; (3) a polyether containing compound, with the following provisos: (i) wherein the polyether containing compound lacks an active hydrogen, the polyether containing compound is present in an amount from about 1 to about 2000 parts per 100 parts by weight of the polyisocyanate; and (ii) wherein the polyether containing compound contains at least one active hydrogen, the polyether containing compound is present in an amount such that, for compounds of Formula I, the OH:NCO equivalency ratio is less than about 0.77:1.00; for compounds of Formula II, the OH:NCO equivalency ratio is less than about 0.25:1.00; and for compounds of Formula III, the OH:NCO equivalency ratio is less than about 0.10:1.00; and (4) substrate particles; under reaction conditions sufficient to form a composite article. The self-releasing binder composition, comprising components (1) , (2) and (3) as described hereinabove, allows for excellent binding and maintenance of the internal bond strength of the substrate particles to be compacted to form the composite article. These substrate particles may include inorganic, polymeric, or other organic or, particularly, cellulosic particles such as wood flakes, chips, particles, strands or fibers, or other comminuted substrates. Additionally, the binder system provides for easy release of the final composite article from aluminum, steel, or other types of metal molds or platens. It thus is ideally suited for uses such as continuous commercial board production lines, where rapid, easy release is sought. In the practice of the present invention the first required component of the self-releasing binder system, defined as comprising at least components (1), (2) and (3) as described herein, is a polyisocyanate' (1) . As used herein, "polyisocyanate" refers to any isocyanate having an average functionality of 2 or greater, i.e., an average of at least two isocyanate groups per molecule. Thus, diisocyanates are encompassed thereby. Illustrative of organic polyisocyanates are diphenyl-methane diisocyanate, m- and p-phenylene diisocyanates, chlorophenylene diisocyanate, α,α -xylylene diisocyanate, 2,4- and 2, 6-toluene diisocyanate and the mixtures of these two isomers which are available commercially, triphenylmethane triisocyanates, 4, 4 '-diisocyanato-diphenyl ether, and polymethylene polyphenyl polyisocyanates. The latter polyisocyanates are mixtures containing from about 25 to about 90 percent by weight of methylenebis (phenyl isocyanate), the remainder of the mixture being polymethylene polyphenyl polyisocyanates of functionality equal to or greater than about 2.0. Such polyisocyanates and methods for their preparation are well-known in the art; see, for example, U.S. Pat. Nos. 2,683,730; 2,950,263; 3,012,008 and 3,097,191. These polyisocyanates are also available in various modified forms. One such form comprises a polymethylene polyphenyl polyisocyanate. The polymethylene polyphenyl polyisocyanates are the preferred polyisocyanates for use in the binder systems of the invention. Particularly preferred polymethylene polyphenyl polyisocyanates are those which contain from about 35 to about 65 percent by weight of methylene bis (phenylisocyanate) . The organic polyisocyanate can, in one embodiment of the present invention, be employed in the binder system in the form of an aqueous emulsion or dispersion. In this case the aqueous emulsion or dispersion can be prepared using any of the techniques known in the art for the preparation of such, prior to use of the composition in the binder. Illustratively, the polyisocyanate can be dispersed in water in the presence of an emulsifying agent. The latter can be any of the emulsifying agents known in the art, including anionic and nonionic agents. Illustrative of nonionic emulsifying agents are polyoxyethylene and polyoxy-propylene alcohols and block copolymers of two or more of ethylene oxide, propylene oxide, butylene oxide, and styrene; alkoxylated alkylphenols such as nonylphenoxy poly(ethyleneoxy) ethanols; alkoxylated aliphatic alcohols such as ethoxylated and propoxylated aliphatic alcohols containing from about 4 to 18 carbon atoms; glycerides of saturated and unsaturated fatty acids such as stearic, oleic, and ricinoleic acids; polyoxyalkylene esters of fatty acids such as stearic, lauric, and oleic acids; and fatty acid amides such as the dialkanolamides of fatty acids including, for example, stearic, lauric, and oleic acids. A detailed account of such materials is found in Encyclopedia of Chemical Technology, Second Edition, Vol. 19, pp. 531-554, Interscience Publishers, New York. The formation of the emulsion or dispersion can be carried out at any time prior to its use with the binder composition. Any of the methods conventional in the art for the preparation of aqueous emulsions can be employed in preparing the aqueous polyisocyanate emulsions, such as the use of an in-line mixer just prior to application of the polyisocyanate to the selected substrate particles. In addition to the polyisocyanate the present invention utilizes an organic acid compound (2) selected from compounds of the formulae: x o o I II II R0 p — OH — c "~~0H R * —— S —"~OH I II OR' ° (I) (II) ( III) wherein X is oxygen or sulfur, R is hydrocarbyl or hydrocarbyl containing an ether or ester group, and may be cyclic, and R' is R, H, or an acyl, carbamoyl, phosphoryl or sulfonyl group. For simplicity of reference these materials are herein termed "organic acid-containing compounds", but included herein are all compounds adhering to the formulae hereinabove, whether or not such would be termed to be or contain "organic acids" in conventional nomenclature. In the formulae shown above, R and R' are selected from the group consisting of alkyl having at least 3 carbon atoms, alkenyl having at least 3 carbon atoms, aryl, aryl substituted by at least one alkyl, alkyl substituted by from 1 to 2 acyloxy groups wherein the acyl group is the residue of an aliphatic monocarboxylic acid having at least 2 carbon atoms. Each of the groups R and R' in the various formulae set forth above can optionally be substituted by one or more inert substituents, i.e., substituents which do not contain active hydrogen atoms and which are therefore unreactive in the presence of the polyisocyanate. Illustrative of such inert substituents are alkoxy, alkylmercapto, alkenyloxy, alkenylmercapto, chloro, bromo, iodo, fluoro, cyano and the like. The compounds therefore comprehended by the above formulae include, for example, acid phosphates, sulfonic acids and carboxylic acids. Also included are the organic acid anhydrides or mixed anhydrides, for example, o-monoacyl, carbamoyl, phosphoryl and sulfonyl derivatives of either group; polyphosphates including branched polyphosphates and cyclometaphosphates; and mixtures thereof. The term "anhydrides" includes, in part, pyrophosphates and pyrosulfates derived from the phosphorus-containing compound (I) or the sulfur-containing compound (III) . The pyrophosphates and pyrosulfates are obtained from their respective acid phosphates or acid sulfates by reaction of the latter with a dehydrating agent, such as carbonyl chloride, aryl or alkyl monoisocyanates and polyisocyanates, N,N'-dihydrocarbylcarbodiimides, and the like, in accordance with procedures well-known in the art; see, for example, F. Cramer and M. Winter, Chem. Ber. 94, 989 (1961); F. Ramirez, J.F. Marecek and I. Ugi, J. Am. Chem. Soc. 97, 3809 (1975) . Preferred for the phosphorus- or sulfur-containing compound selection are liquid esters, including monoesters, diesters and combinations thereof, which are well-known, commercially available materials. If desired, the acid phosphates of Formula (I) can be readily prepared in the form of mixtures of mono-and-diesters by reaction of an alcohol ROH or thiol RSH, wherein R is as defined above, with phosphorus pentoxide or oxysulfide in accordance with well-established procedures; see, for example, Kosolapoff, Organophosphorus Compounds, pp. 220-221, John Wiley and Sons, Inc., New York, 1950. Also preferred are the pyrophosphates or mixed pyrophosphates derived from mixtures of acid phosphates, and the pyrosulfates or mixed pyrosulfates derived from mixtures of sulfonic acids, readily obtained through methods cited above. Illustrative of the phosphorus-containing compounds of Formula (I) above which can be employed individually or in combination with other acid phosphates in the process of the invention are monoester acid phosphates such as mono-O-octyl, mono-O-nonyl and mono-O-decyl acid phosphate; diester phosphates such as 0,0-di (octyl) , 0,0-di (nonyl) and 0,0-di (decyl) acid phosphate; pyrophosphates such as tetraoctyl, tetranonyl and tetradecyl as well as di(octyl), di(nonyl) and di(decyl) pyrophosphates; and polyphosphates terminated with mono-O-octyl, mono-O-nonyl and mono-O-decyl groups, or 0,0-di (octyl) , 0,0-di (nonyl) and 0,0-di (decyl) groups, or mixed mono-O-octyl, 0,0- di (octyl) groups, or combinations of mono-O-alkyl and 0,0-dialkyl groups of different chain lengths. It is apparent that acid phosphates and thiophosphates in which the esterifying radical is that derived from a monohydric alcohol which has been capped using the appropriate molar proportions of ethylene oxide, propylene oxide, epichlorohydrin or 1, 1, 1-trichlorobutylene oxide, are particularly advantageous in the present invention. Additional phosphate compounds which are useful in this invention include monoacyl acid phosphates such as O-decanoyl, O-dodecanoyl and O-benzoyl derivatives, prepared as described by Kosolapoff, ibid, p. 334, and carbamoyl phosphates such as octenylcarbamoyl, decenylcarbamoyl and dodecenylcarbamoyl phosphates, prepared as described by F. Cramer and M. Winter, Chem. Ber., pp. 92, 2761 (1959). As shown by Formula (II) hereinabove, carboxylic and polycarboxylic acids are also useful in the present invention. These can include, for example, straight and branched chain, poly- and mono-ethylenically unsaturated acids such as 3-octenoic acid, 11-dodecanoic acid and 1, 12-dodecanoic di(acid). The higher molecular weight polycarboxylic acids and polyfunctional carboxylic acids can be formulated to have a low viscosity for convenient spray application, along with the other components of the present invention, to the substrate particles. Particularly suitable sulfonic acids shown by Formula (III) hereinabove, include, for example, decane sulfonic acid, octadecane sulfonic acid, benzene sulfonic acid, toluene sulfonic acid, naphthalene sulfonic acid, cyclohexane sulfonic acid, and aromatic monosulfonic acids of the type which may be obtained in known manner by the sulfonation of alkyl benzenes such as hexyl-benzene, dodecyl-benzene, octadecyl-benzene or mixtures thereof. In the practice of the present invention a polyether containing compound (3) is also employed. The polyether containing compound can contain an active hydrogen, or can have, as its terminal or pendant groups, moieties that are not active hydrogens and are otherwise unreactive, that is, substantially inert, toward the polyisocyanate. As used herein, the "polyether containing compound" therefore includes any compound containing one or more polyether moieties, whether or not such would be classified by standard nomenclature as primarily or essentially a polyether compound. In one embodiment, the polyether compound contains active hydrogens. Determination of whether there is an active hydrogen can be determined by use of the Zerewitinoff Test, as described in J.B. Niederl and V. Niederl, Micromethods of Quanitative Organic Analysis, p. 263 (New York 1946) . In general the active hydrogen in such compounds reacts with polyisocyanates to form polyurethanes and related polymers, including polyureas and polyurethane/polyureas, and therefore, in some embodiments of the present invention the result is a polyurethane, polyurea or polyurethane/polyurea polymer binder. The active hydrogen containing compound is preferably a hydroxy-functional compound such as a polyol or monol. In general any polyether polyol typically employed in the art for preparation of polyurethane and related polymers, including so-called polyester polyols which contain polyether moieties (also called polyether polyester polyols), are suitable, and can have hydroxyl numbers which vary over a relatively wide range, preferably from 10, more preferably 100, to 6,000, more preferably to 600. Preferred alcohols include polyols and monols selected from the following classes of compositions, alone or in admixture: (a) alkylene oxide adducts of poly-or-monohydroxy-alkanes or alkenes; (b) alkylene oxide adducts of non-reducing sugars and sugar derivatives; (c) alkylene oxide adducts of phosphorus and polyphosphorus acids; and (d) alkylene oxide adducts of polyphenols. Polyols of these types are referred to herein as "base polyols". Examples of alkylene oxide adducts of polyhydroxyalkanes useful herein are adducts of ethylene glycol, propylene glycol, 1, 3-dihydroxypropane, 1, 4-dihydroxybutane, and 1, 6-dihydroxyhexane, glycerol, 1,2,4-trihydroxybutane, 1,2, 6-trihydroxyhexane, 1, 1, 1-trimethylolethane, 1, 1, 1-trimethylol-propane, pentaerythritol, polycaprolactone, xylitol, arabitol, sorbitol, mannitol, sucrose, various amines, mixtures thereof, and the like. Also useful are pol (oxypropylene) glycols, triols, tetrols and hexols and any of these that are capped with ethylene oxide. These polyols also include poly(oxypropyleneoxyethylene)polyols. The ethylene oxide, when used, can be incorporated in any way along the polymer chain, for example, as internal blocks, terminal blocks, or randomly distributed blocks, or any combination thereof. Additionally, polyester polyols and thiol compounds which contain polyether moieties are useful in this invention. Other polyether containing compounds such as polyamines, amine-terminated polyols, polymercaptans and other isocyanate-reactive compounds are also suitable in the present invention. Another preferred class of polyols includes the "copolymer polyols", which are base polyols containing stably dispersed polymers such as acrylonitrile-styrene copolymers. Other types of polyether polyols useful in the process of the invention include polyurea polyols, such as are disclosed in U.S. Patents 3,325,421; 4,042, 537; 4,089,835; polyoxamate polyols, such as are disclosed in U.S. Patent 4,407,983; and polyisocyanate- polyaddition products, such as are disclosed in U.S. Patents 4,374,209; 4,324,716; 4,310,448; 4,310,449; 4,350,857; and 4,305,858. Polyether containing compounds which do not possess active hydrogens are also useful for the practice of this invention. Inert reaction products of the polyether polyols, polyamines or polythiols heretofore described constitute an important group of these compounds. The term "inert" means that the reaction product is substantially unreactive with the polyisocyanate, in accordance with J.B. Niederl and V. Niederl, Micromethods of Quanitative Organic Analysis, p. 263 (New York 1946), in the self-releasing binder composition. These inert reaction products may be formed by addition of a polyether compound containing active hydrogens, epoxides or any group reactive with an isocyanate, to a stoichiometric excess of polyisocyanate, forming what are commonly termed as prepolymers, which contain at least one reactive isocyanate functional group. The prepolymer thus formed may contain polyurethane, polyurea, polythiourea, or other moieties implicit in the prior description of the active hydrogen containing compounds. A second group of inert reaction products of polyether polyols are those formed by esterification of the polyether polyol with organic acids or organic acid anhydrides. Polyethers comprising ethylene oxide, propylene oxide, butylene oxide and tetramethylene oxide, copolymers or mixtures thereof, and possessing mono-or-polyhydroxy functionalities may thus be reacted with common acids or acid anhydrides through known procedures to prepare inert polyether esters. Examples of common acids are acetic, propionic. lauric, and toluene sulfonic acid, while acetic and phthalic anhydride are illustrative of common anhydrides . A third group of inert polyether containing compounds can be prepared by reaction of a polyether polyol with monoisocyanates to form carbamoyl derivatives. Urea, thiourea, epoxide and siloxane derivatives are likewise available through reaction with corresponding polyether containing amine, thiol, epoxy and siloxane compounds, respectively. An example of a monoisocyanate that can be suitably employed is phenyl isocyanate. Other polyether containing compounds which are otherwise unreactive toward isocyanates, that is, which do not contain any active hydrogen, are tresylate, acrylate, aldehyde and succinimidyl derivatives of polyethylene glycol. Further examples of unreactive compounds are polyalkoxy ethers, polyalkoxy epoxides, polyalkoxy siloxanes, polyalkoxy amides, and polyalkoxy ketones wherein the pendant or terminal active hydrogens or functional groups have been reacted as hitherto described. Although this list is not considered comprehensive, it should be evident to those skilled in the art that various functional groups which can be rendered inactive toward polyisocyanates through standard chemistries will function within the scope of this invention, provided sufficient polyether content exists to effect release when used in conjunction with organic acids (2) . It is preferred that the weight ratio between such "inert" polyether containing compound and polyisocyanate be from 1, more preferably from 4, and most preferably from 6, to 2,000, more preferably 20, and most preferably 15, parts per 100 parts of polyisocyanate. Mixtures of active hydrogen polyether containing compounds and inert polyether containing compounds can also be employed in the present invention. Previously described are the constituents of the self- releasing binder system itself. The starting materials for a composite article also comprise substrate particles. These particles are, in one preferred embodiment, cellulosic and capable of being compacted and bonded into the form of boards. Typical such materials are wood particles derived from lumber manufacturing waste such as planar shavings, veneer chips, and the like. Particles of other cellulosic material such as shredded paper, pulp or vegetable fibers such as corn stalks, straw, and bagasse, and of non-cellulosic materials such as scrap metals; polyurethane, polyisocyanurate, polyethylene and similar polymers; glass fibers; and combinations thereof, can also be used. Inorganic materials such as hydrated alumina, gypsum, and chopped mineral fibers can be employed, either alone or in combination with any of the above cellulosic or non-cellulosic materials, in the formation of particleboards or other composite articles in accordance with the present invention. If desired, mixtures of various types of cellulosic particles may also be used. If cellulosic particles are selected as the substrate material, it is generally preferred that the starting moisture content thereof is less than about 25 percent by weight. In the present invention a number of different ways of contacting the starting materials, comprising the polyisocyanate (1), organic acid compound (2), polyether containing compound (3), and substrate particles (4), can be employed. In the first application method, segregated components (1), (2) and (3) may be brought together simultaneously to be applied to the substrate particles. The term "simultaneously" implies the act of bringing together the segregated components (l)-(3) prior to application to the substrate particles, whether it is accomplished through prior combination of (2) and (3) followed by contact with (1), or, the act of bringing together is accomplished in a single stream which is fed by the hitherto segregated components (1), (2), and (3) . In one embodiment the selected organic acid containing compound is pre-blended with an active hydgrogen-containing polyether compound, such as a polyether polyol. Such generally forms a storage-stable composition which can be easily handled. In this case the weight ratio of the organic acid-containing compound to the active hydrogen containing polyether compound is preferably from 1:7600 to 1:0.10, more preferably from 1:275 to 1:0.70, and most preferably from 1:12 to 1:1. Simple blending, using any of a wide variety of methods and equipment well known to those skilled in the art, to ensure homogeneity, at ambient conditions of temperature and pressure, is preferred for reasons of convenience; however, a wide range of conditions from the freezing temperature of a given constituent to its boiling temperature can be used, since it is preferable that each component be a liquid. Thus, preferred temperatures range from 0°C, more preferably 15°C, to 70°C, more preferably 50°C, and preferred pressures range from about 0 to about 3 atmospheres (atm) . (1 atm equals 101,325 Pascals, or about 0.1 MPa.) Increased temperature or pressure can, in one embodiment, be employed to improve flow within the system where relatively viscous materials have been selected. It is preferable that the viscosity of the organic acid-containing compound/active hydrogen polyether containing compound blend be from 10, more preferably 50, to 5,000, more preferably 400, centipoise (cps) . For some selections of component (2) which are solid or not soluble in the polyether containing compound at room temperature, it is desirable to heat to their melting or solubility point in order to produce a homogeneous blend. In general it is preferred to use the higher monoester forms of liquid acid phosphates, such as 2-ethylhexyl- or isodecyl-, due to their greater ease of handling and compatibility with the polyol. Following preparation of the blend including the polyether containing compound (3) and organic acid (2), the blend is then ready to be contacted with the polyisocyanate and applied to the cellulosic or other type of substrate particles. It is preferred that the weight ratio of the organic acid containing compound to the polyisocyanate be from about 4, preferably from about 6, to about 12 parts, more preferably about 8 parts, organic acid-containing compound, to about 100 parts polyisocyanate. Because the polyisocyanate and active hydrogen polyether containing compound react to form a polyurethane and/or polyurea polymer, it is necessary, when the components are all mixed together prior to application to the particles, that such application occur within a relatively short period of time after mixing. In order to mix the polyisocyanate and isocyanate-reactive compound, any means, method, equipment or conditions generally known to or used by those skilled in the art of polyurethane and related polymer production may be used. These include, for example, impingement mixing to a spray head; simple mixing, as by hand or mechanical means on either a small or large scale; or by use of rollers or shakers. Since the reaction between the polyisocyanate and the isocyanate-reactive constituent of the blend is exothermic in nature, it is preferred that such contact be carried out at a temperature from 0°C, more preferably 20°C, to 50°C, more preferably 30°C. In another embodiment of the present invention each of the components of the binder composition can be simultaneously mixed, as, for example, using a three-stream mixhead, without pre-blending of the organic acid compound (2) with the polyether containing compound (3) . In still another embodiment the organic acid compound (2) can be pre-blended with the polyisocyanate (1) . In this case it is preferable that such pre-blending be accomplished just prior to contact with the polyether containing compound, since the polyisocyanate and organic acid compound (2) may in some cases be reactive and therefore may not be sufficiently storage-stable. In yet another embodiment, the components of the binder composition, (1), (2) and (3) are combined and processed into a storage-stable material which is stored in a single container, until needed for application to the substrate particles (4) . It should be evident to those skilled in the art, that means are available for processing organic acid containing compounds (2) through reaction with polyisocyanates such that reaction products are inert and no longer reactive toward polyisocyanates . Examples of this are found in US 4,258,169, US 4,478,738 and US 4,772,442. The polyether containing compound (3) may be combined with the polyisocyanate (1) in a manner consistent with the presence or absence of active hydrogens in the compound. In one embodiment, a prepolymer of an active hydrogen polyether containing compound, such as a polyether polyol, can be formed by means well-established in the art. In a second embodiment, an inert polyether containing compound such as an esterified polyether monol, can be blended with a polyisocyanate. For the polyether containing compound, whether or not it contains active hydrogens, the reaction or blending with the polyisocyanate can occur with a polyisocyanate which has already been reacted with the organic acid containing compound (2) , or, may first be reacted with or blended with the polyisocyanate which subsequently undergoes reaction with the organic acid containing compound, or, in cases wherein there is insignificant reactivity between the polyether containing compound (3) and organic acid containing compound (2), they may be added in concert to the polyisocyanate (1) . In general, it is preferred that (1), (2) and (3) are processed into a liquid storage-stable mixture by heating the polyisocyanate (1) at a temperature from about 60°C to about 190°C; combining therewith, either simultaneously or subsequently, from about 1 to about 20 parts, per 100 parts of polyisocyanate, each of (2) and (3) to form a reaction mixture; maintaining the heating for a time such that no phase separation occurs upon cooling the reaction mixture to ambient temperatures . In a preferred embodiment, an organic acid is combined with a polyisocyanate over a temperature range from about 60 to about 190°C for two hours; then a polyether containing compound which contains no active hydrogens is added. Preferably, the organic acid is an acid phosphate; the polyisocyanate is a polymeric isocyanate, and the polyether containing compound is an esterified polyether monol. The organic acid and the polyether containing compound are preferably used in an amount of 1 to 20 parts, based on 100 parts of polyisocyanate. In a still more preferred embodiment, 4-12 parts of acid phosphate and 6-20 parts of polyether containing compound, based on 100 parts of polyisocyanate, are used. It is also more preferred to use a temperature from 60-100°C. In this case the esterified polyether monol can be added at an elevated temperature to react out minor amounts of active hydrogen containing impurities that may be present, in which case it is preferable to perform the addition at 60-80°C, maintaining this temperature for 0.5-1.5 hours until the impurities are rendered inert. In any case, heating is maintained for a time such that substantially no phase separation occurs upon cooling the reaction mixture to ambient. If no active hydrogen containing impurities are present, the esterified polyether monol can be blended with the polyisocyanate containing the reaction product of the acid phosphate, at ambient temperature. This self- releasing binder composition is a liquid, storage-stable material and may be stored for a considerable period of time until desired for application to substrate particles. In another preferred embodiment, a polyether polyol (3) and an acid phosphate (2) can be added to a stoichiometric excess of polyisocyanate (1) maintained between 60-100°C for 2 to 3 hours. The same proportions of materials as previously described are employed. The preferred polyisocyanate has a relatively high monomeric methylene bis(phenyl) isocyanate content, such that the viscosity of the final reaction product is preferably from 50 to 1000 cps, more preferably to 500 cps . If desired, a relatively low viscosity product can be blended with a higher order polymeric isocyanate to increase viscosity. Alternatively, a relatively high viscosity product, formed from a higher order polymeric isocyanate, can be blended with a polyisocyanate containing a significant proportion of methylene bis(phenyl) isocyanate to achieve a lower viscosity product. In either case, the amounts of reactants are adjusted accordingly such that the final product falls within the preferred weight ranges. Illustratively, a total of from about 2 to 8 percent by weight of the binder system (total constituent weight, excluding any moisture which may be present in the particles) is added, based on the "oven dry" weight of the particles, but higher or lower amounts of binder system may be used in any given application. Illustratively, where the particles are of large size, such as in strand board and wafer board, it is possible to use amounts of binder less than 1 percent by weight, based on the "oven dry" weight of the particles. Where the particles are very small, that is, have a high surface area to volume ratio as in the case of powdered inorganic materials, it is desirable to use amounts of binder up to about 30 percent by weight, preferably to about 20 percent by weight. If desired, other materials, such as wax sizing agents, fire retardants, pigments, and combinations thereof, may also be added to the particles before or during the application of the binder system to the substrate particles. In a preferred embodiment of the present invention, the coated substrate particles are concurrently or subsequently formed into a loose mat or felt, preferably containing from 4 percent to 20 percent moisture by weight. The mat is then placed in a heated press and compressed to consolidate the substrate particles into a compact composite article. Pressing times, temperatures and pressures vary widely depending on the thickness of the board produced, the desired density of the board, the size of the particles used, and other factors well known in the art. For example, for 0.5 inch thick particle board of medium density, pressures of from about 300 to about 700 psi and temperatures of from about 325°F to about 400°F are typical. Pressing times are typically from about 2 to about 5 minutes. The above-described process can be carried out on a batch basis, that is, individual sheets of particle board can be molded by treating an appropriate amount of particles with the binder resin combination and heating and pressing the treated material. Alternatively, the process can be carried out in a continuous manner by feeding treated particles in the form of a continuous web or mat through a heating and pressing zone defined by upper and lower continuous belts to which, and through which, the necessary heat and pressure are applied. Whether the process of the invention is carried out in a batchwise or continuous manner, it has been found that composite articles produced using the self-releasing binder composition described herein release readily from the metal plates of the press used in their formation and show a significantly reduced tendency to stick or adhere to the platens, even when the platens are made of steel, as well as when the platens are made of other commonly used materials such as aluminum, chromium and nickel. This is in direct contrast to previous experience with the use of polyisocyanates alone, or polyisocyanates with acid phosphates, sulfates or carboxylates alone, on certain types of platens, and particularly on steel. The following preparations and examples are intended to illustrate the present invention and are not intended to be, nor should they be construed as being, limiting of its scope in any way. As used in the examples, the following terms are defined as follows: DOWANOL™ 500 denotes a product available from The Dow Chemical Company which is a 500 molecular weight monol prepared from heterofed ethylene oxide and propylene oxide. P-425, denotes a product available from The Dow Chemical Company which is a 425 molecular weight propylene oxide-based polyether polyol. E-400, denotes a product available from The Dow Chemical Company which is a 400 molecular weight ethylene oxide-based polyether diol. ETHFAC™ PD-0, denotes a product available from Ethox Corporation which is a high mono-ester isodecyl acid phosphate. ETHOX™ 101, denotes a product available from Ethox Corporation which is a monoester/diester blend of isodecyl acid phosphate. BIO-SOFT™ S-100 denotes a product available from Stepan Company which is a linear dodecylbenzene sulfonic acid. STEPANTAN™ H-100, denotes a product available from Stepan Company which is a branched dodecylbenzene sulfonic acid. PRIPO ™ 1009, denotes a product available from Unichema International which is a C^Q dimer carboxylic acid. MPEG 350 AC denotes a product available from The Dow Chemical Company which is an acetate ester of a 350 molecular weight methoxy polyethylene glycol monol. GLY PO AC denotes a product available from The Dow Chemical Company which is a triacetate ester of a 1800 molecular weight propoxylated glycerin. KESSCO™ PEG 200 DL, denotes a product available from Stepan Company which is a dilaurate ester containing four moles of ethylene oxide. PAPI™ 27 denotes a product available from the Dow Chemical Company, which is a polymeric diphenylmethane diisocyanate having a 134 isocyanate equivalent weight. PAPI™ 88 denotes a product available from The Dow Chemical Company, which is a polymeric diphenylmethane diisocyanate having a 136 isocyanate equivalent weight. ISONATE™ 125M denotes a product available from The Dow Chemical Company, which is diphenylmethane diisocyanate having a 125 isocyanate equivalent weight Examples 1- 6 Six different binder compositions (examples 1-6) of the present invention were prepared using the formulations shown in Table 1. Three additional binder compositions (controls 1, 3 and 4) were also prepared and did not contain any polyether containing compounds (3) ; therefore, these do not represent embodiments of the present invention and are included for comparative purposes only. Each formulation was run at a polyisocyanate: polyether:organic acid weight proportion of 100 parts:13.6 parts:9.9 parts, except for controls 1, 3 and 4 which were run at a polyisocyanate:organic acid ratio of 100 parts:9.9 parts. Control 2 contained only polyisocyanate. The polyisocyanate used for each of the examples and controls was PAPI™ 88. For these examples the organic acid containing compound (2) was blended with the polyether containing compound (3) at room temperature prior to contact with the isocyanate (1) . The polyether containing compound (3) was weighed into a beaker, the organic acid (2) was weighed into the same beaker, and the two compounds were then stirred together for several minutes until a clear, homogenous blend was produced. This blend remained as a single phase for several weeks. Using the formulations described in Table 1, at the proportions described previously, composite boards were prepared at 6.2 percent binder content, based upon the dry weight of standard aspen oriented strandboard wood flakes (typically 3 inch by 1 inch by 0.05 inch), in order to test releasability of the formulations. The formulations were metered together and sent through a static mixers just prior to spray application to wood flakes. The wood particles were tumbled in a rotating drum and the spray was introduced at a rate of 1 to 5 grams per second (g/s) through a port in the drum. The spray application lasted for 1 to 3 minutes, and the wood flakes were allowed to tumble an additional 10 minutes. Following application of the blended components, the wood flakes were handlaid together into either a 2 foot by 2 foot or a 10 inch by 10 inch deckle box which was positioned on a steel caul. The wood mat was then pressed with the steel caul on the bottom, using either a steel caul sheet on top or directly against the top press platen. Typical press parameters were employed, using a time of 3 minutes; a temperature of 190°C; and a pressure of 400-500 psi (2.75 MPa - 3.44 MPa). The press surfaces were initially cleaned thoroughly, but the surface was not otherwise treated before or during the press run. As used herein, "release" is defined to mean that the part being prepared did not need to be pried from surfaces and did not leave behind particles that had to be scraped from the surface before another part could be pressed thereon. Table 1 Example Organic Acid (2) Platen Composition No. of Polyether Number Releases Containing Compound (3) 1 18+ D0WAN0L™ 500 ETHFAC™ PD-0 316 stainless top, carbon steel bottom 2 5+ P 425 ETHFAC™ PD-0 316 stainless top, carbon steel bottom 3 5+ E 400 ETHFAC™ PD-0 316 stainless top, carbon steel bottom 4 2+ DOWANOL™ 500 ETHFAC™ 101 316 stainless 5 4+ DOUANOL™ 500 STEPANTAN™ H- carbon steel top, 100 410 stainless bottom 6 4+ DOWANOL™ 500 PRIPOL™ 1009 carbon steel top, 410 stainless bottom control 1 -- 0 ETHFAC™ PD-0 316 stainless control 2 _- 0 316 stainless control 3 0 -- STEPANTAN™ H- carbon steel top, 100 410 stainless bottom control 4 0 -- PRIPOL™ 1009 carbon steel top, 410 stainless bottom All experiments were performed using aspen wood. - indicates not present. + indicates presumption that additional releases could be achieved, based on easy release of past part; however, experiment was terminated at this particular point. Controls 1-4 are for comparative purposes only and do not represent an embodiment of the present invention. Example 7 A 3000 g (80.6 percent by weight) portion of PAPI™ 27 was charged into a multinecked reactor equipped with mechanical agitator and nitrogen purge. The polyisocyanate was heated to 80-85°C, whereupon a 300 g (8.1 percent by weight) portion of ETHFAC™ 101 was added over about 15 minutes with mild foaming ensuing. After approximately 30 minutes, 420 g (11.3 percent by weight) of MPEG 350 AC was introduced over a 12 minute time period and the reaction was maintained between 80-85°C for an additional 1.5 hour. A single-phase, homogeneous liquid was obtained. A 6 kg portion of pine flakes having an 8 percent moisture content was treated with an aerosol spray of a 300 g (5 percent) aliquot of binder and pressed into 10 inch by 10 inch boards as described in Examples 1-6. Release results are shown in Table 2. Example 8 A 3000 g (80.6 percent by weight) portion of PAPI™ 27 was heated to 82°C; subsequently, 300 g (8.1 percent by weight) of ETHFAC™ 101 was added over a 17 minute period with mechanical agitation and nitrogen purge. Mild foaming ensued. The reaction was maintained for 30 minutes at 82°C, then 420 g (11.3 percent by weight) of GLY-PO AC was added during a 20 minute period. After an additional 1.5 hour at 80-83°C, the reaction mixture was cooled to room temperature, yielding a homogeneous, single-phase liquid. A 431 g aliquot (5.8 percent resin) of this binder was applied to 6957 g of pine flakes at 7 percent moisture content using methods described above. A series of 10 inch by 10 inch composite boards was prepared with release results reported in Table 2. Example 9 A 5.7 g (25 percent by weight) portion of KESSCO™ PEG 200 DL was combined with 1.2 g (5 percent by weight) of ETHFAC™ PD-0. The mixture was added to 16.4 g (70 percent by weight) of PAPI™ 88 and thoroughly mixed prior to application to the aspen wood flakes, which occurred within a few minutes of its preparation. An 803 g portion of aspen flakes was treated with 23.3 g (2.8 percent by weight) of binder as described in Examples 1-6. Data for composite board release is shown in Table 2. Example 10 A mixture of 80 g (8.6 percent by weight) of ETHFAC™ 101 and 110 g (11.8 percent by weight) DOWANOL™ 500 was introduced into a 243 g (26 percent by weight) portion of ISONATE™ 125M which has been heated at 85°C under nitrogen purge. The introduction is carried out over a 45 minute period. The colorless MDI became a golden yellow with foam evident after about 8 minutes into the addition period. The reaction mixture was maintained at 81-89°C for an additional 1.75 hour, then allowed to cool, revealing a turbid yellow, somewhat viscous consistency. The mixture was then blended with 500 g (53.6%) of PAPI™ 88 at ambient temperature. A 340 g (5.4%) aliquot of this mixture was sprayed onto 6000 g of pine flakes at 15 percent moisture content, utilizing apparatus and procedures previously outlined. Composite boards measuring 20 inches by 20 inches were prepared, with release data provided in Table 2. The comparative examples designated as controls 5, 6 and 7 are for comparative purposes only, and are not considered to represent embodiments of the present invention. Comparative Example: Control 5 A 15.1 g (7 percent by weight) amount of ETHFAC™ 101 was added to 200 g of PAPI™ 88, heated to 90°C under nitrogen, during a 10 minute interval. The reaction was continued at 90°C for an additional 2 hours. Boards measuring 6 inches by 6 inches were prepared as previously detailed by treating aspen flakes with binder in a ratio of 164 g wood to 3.3 g (2 percent by weight) of binder. Release results are shown in Table 2. Comparative Example: Control 6 A 28.7 g portion of PAPI™ 88 was combined with 9.6 g (25 percent by weight) of MPEG 350 AC at ambient temperature. This mixture was applied to 1395 g of aspen flakes, representing 2.7 percent by weight. Release data for the composite boards formed is shown in Table 2. Comparative Example: Control 7 A 5.7 g (25.8 percent by weight) amount of KESSCO™ PEG 200 DL was blended with 16.4 g of PAPI™ 88 and applied to 1083 g of aspen flakes, yielding 2 percent by weight. Release data for the composite boards is provided in Table 2. Table 2 Example No. Polyether Organic Acid Platen Composition No. of Compound Releases 7 MPEG 350 AC ETHFAC™ 101 Carbon steel top, 100+ 316 stainless bottom 8 GLY-PO AC ETHFAC™ 101 Carbon steel top, 12+ 316 stainless bottom 9 KESSCO™ 200 DL ETHFAC™ PD-0 Carbon steel top, 4+ 410 stainless bottom 10 DOWANOL™ 500 ETHFAC™ 101 Carbon steel top, 3+ (prepolymer) 316 stainless bottom control ETHFAC™ 102 Carbon steel top, 0 5 316 stainless bottom control MPEG 350 AC Carbon steel top, 0 6 316 stainless bottom control KESSCO™ 200 DL Carbon steel top, 0 7 410 stainless bottom Examples 7, 8, and 10 and controls 5 and 6 were performed using pine wood. Examples 9 and control 7 were performed using aspen wood. - indicates not present. + indicates presumption that additional releases could be achieved, based on easy release of last part; however, experiment was terminated at this particular point. Controls 5-7 are for comparative purposes only and do not represent an embodiment of the present invention.

Claims: What is claimed is: 1. A self-releasing binder composition prepared by contacting at least (1) a polyisocyanate compound, (2) a compound of one of the following formulae in an amount from about 1 to about 20 parts per 100 parts by weight of the polyisocyanate compound: II II OH 'OH s 'OH II OR' (I) (I,) (III) wherein X is oxygen or sulfur, R is hydrocarbyl or hydrocarbyl containing an ether or ester group, and may be cyclic, R' is R, H, or an acyl, carbamoyl, phosphoryl or sulfonyl group; and (3) a polyether containing compound, with the following provisos: (i) wherein the polyether containing compound lacks an active hydrogen, the polyether containing compound is present in an amount from about 1 to about 2000 parts per 100 parts by weight of the polyisocyanate; and (ii) wherein the polyether containing compound contains at least one active hydrogen, the polyether containing compound is present in an amount such that, for compounds of Formula I, the OH:NCO equivalency ratio is less than about 0.77:1.00; for compounds of Formula II, the OH:NCO equivalency ratio is less than about 0.25:1.00; and for compounds of Formula III, the OH:NCO equivalency ratio is less than about 0.10:1.00; under reaction conditions sufficient to form a binder composition. 2. A process for preparing a composite article comprising contacting substrate particles and a self-releasing binder composition prepared by contacting at least (1) a polyisocyanate compound, (2) a compound of one of the following formulae in an amount from about 1 to about 20 parts per 100 parts by weight of the polyisocyanate compound: II RO OH • OH 'OH II OR' (I) (ID (III) wherein X is oxygen or sulfur, R is hydrocarbyl or hydrocarbyl containing an ether or ester group, and may be cyclic, R' is R, H, or an acyl, carbamoyl, phosphoryl or sulfonyl group; (3) a polyether containing compound, with the following provisos: (i) wherein the polyether containing compound lacks an active hydrogen, the polyether containing compound is present in an amount from about 1 to about 2000 parts per 100 parts by weight of the polyisocyanate; and (ii) wherein the polyether containing compound contains at least one active hydrogen, the polyether containing compound is present in an amount such that, for compounds of Formula I, the OH:NCO equivalency ratio is less than about 0.77:1.00; for compounds of Formula II, the OH:NCO equivalency ratio is less than about 0.25:1.00; and for compounds of Formula III, the OH:NCO equivalency ratio is less than about 0.10:1.00; and (4) substrate particles; under reaction conditions sufficient to form a composite article. 3. The process of Claim 2 wherein (1), (2) and (3) are contacted first to form a reactive mixture, and then the reactive mixture is contacted with the substrate particles (4) . 4. The process of Claim 2 wherein (1), (2) and (3) are processed into a liquid, storage-stable mixture by heating the polyisocyanate (1) at a temperature from about 60°C to about 190°C; combining therewith, either simultaneously or subsequently, from about 1 to about 20 parts, per 100 parts of polyisocyanate, each of (2) and (3) to form a reaction mixture; and maintaining the heating for a time such that substantially no phase separation occurs upon cooling the reaction mixture to ambient temperature. 5. The process of Claim 2 wherein the Formula I compound is selected from the group consisting of acid phosphates; acid phosphate anhydrides; acid polyphosphates; and mixtures thereof. 6. The process of Claim 5 wherein the acid phosphate anhydrides are selected from the group consisting of o-monoacyl, carbamoyl, phosphoryl and sulfonyl derivatives of acid anhydrides, and mixtures thereof, and the acid polyphosphates are selected from the group consisting of branched polyphosphates, cyclometaphosphates and mixtures thereof. 7. The process of Claim 2 wherein the polyether containing compound is selected from the group consisting of (1) an active hydrogen polyether containing compound selected from the group consisting of polyether polyols, polyether thiols, polyether amines, polyether polyester polyols, hydroxy polyether siloxanes, amino polyether siloxanes and mixtures thereof; (2) an inert polyether containing compound selected from the group consisting of polyether esters, polyether ethers, polyether isocyanate prepolymers, polyether ketones, polyether aldehydes, polyether polyesters, polyether thiolates, polyether amides, polyether epoxides, polyether siloxanes and mixtures thereof; and (3) mixtures thereof. 8. The process of Claim 2 wherein the polyisocyanate is selected from the group consisting of diphenylmethane diisocyanate, m- and p-phenylene diisocyanates, chlorophenylene diisocyanate, , -χylylene diisocyanate, 2,4- and 2,6-toluene diisocyanate and mixtures thereof, polymeric toluene diisocyanate, triphenylmethane triisocyanates, 4,4 '-diisocyanato-diphenyl ether, polymethylene polyphenyl polyisocyanates, and mixtures thereof. 9. The process of Claim 2 wherein the substrate particles are selected from the group consisting of cellulosics, lignocellulosics, polymers, metals, inorganic materials, and mixtures thereof. 10. The process of Claim 2 wherein the Formula II compound is selected from carboxylic acids, dirtier carboxylic acids, polycarboxylic acids and mixtures thereof, and the Formula III compound is selected from sulfonic acids, polysulfonic acids and mixtures thereof.

Inventors: MARTONE DANIEL P, NELSON GILBERT LIDDELL, MARTONE, DANIEL, P., NELSON, GILBERT, LIDDELL
Applicants: DOW CHEMICAL CO, MARTONE DANIEL P, NELSON GILBERT LIDDELL, MARTONE, DANIEL, P., NELSON, GILBERT, LIDDELL, THE DOW CHEMICAL COMPANY
Application year: 1995
Main classification: C08L97
IPC codes: C08G18, C08L75, C08L97, C09J175