MXPA01006023A

MXPA01006023A - Extended polymethylene poly(phenylisocyanate) resin binders for the production of wood composite products

Info

Publication number: MXPA01006023A
Application number: MXPA/A/2001/006023A
Authority: MX
Inventors: W Rosthauser James
Original assignee: Bayer Corporation
Priority date: 1998-12-17
Filing date: 2001-06-14
Publication date: 2001-12-13

Abstract

This invention relates to a process for the production of wood composite materials. This process comprises combining wood particles with a mixture comprising a solid compound comprising urea and/or melamine, and a polymethylene poly(phenyl isocyanate), followed by molding or compressing the coated combination of wood particles.

Description

POLY RESIN BINDERS (FENI L I S OC I NATO) OF EXTENDED POLYMETHYLENE FOR THE PRODUCTION OF WOOD COMPOUND PRODUCTS BACKGROUND OF THE INVENTION This invention relates to a process for the production of wood composite products or materials. This process consists of combining wood particles with a mixture of (1) a compound selected from the group consisting of urea, melamine and its mixtures and (2) a poly (phenylisocyanate) of polymethylene, followed by molding or compression of the combination of wood particles and reactive mixture. Composite materials such as oriented strand board, particle board and flake boards are generally produced by mixing or pulverizing crushed lignocellulose materials such as wood flakes, wood fibers, wood particles, wafers, strips or wood strands, pieces of wood. wood or other lignocelu-slab materials crushed with a binder composition, while the crushed materials are mixed by turning them or stirring them in a mixer or similar apparatus. After mixing sufficiently to form a uniform mixture, materials are formed of a loose mat, which is compressed between heated rollers or plates to fix the binder and join the scales, strands, strips, pieces, etc. each other in a densified form. Conventional processes are generally carried out at temperatures of about 150 to 225 ° C in the presence of varying amounts of steam, generated by the release of moisture encased in wood or lignocellulose materials. These methods also generally require that the moisture content of the lignocellulose material be between about 2 and about 20% by weight before it is mixed with the liigante. The production of plywood is achieved by roller coating, knife coating, curtain coating or spraying a clear composition on wood veneer surfaces. A plurality of sheets is then accumulated to form sheets of the required thickness. The mats or sheets are placed in a heated press and compressed to effect the consolidation and curing of the materials on a board. The binder compositions which have been employed in the preparation of such composite wood products include phenol and formaldehyde resins, urea and formaldehyde resins and isocyanates. See, for example, the work of James B. Wilson entitled "Isocyanate Adhesives as Binders for Com-position Board", which was presented at the symposium "Wood Adhesives - Research, Applications and Needs", held in Madison, Wisconsin, on 23 -25 September 1980, where the advantages and disadvantages of each of these different types of binders are discussed. Isocyanate binders are commercially desirable, as they have low water absorption, high adhesive and cohesive strength, flexibility in the formulation, versatility with respect to temperature and curing speed, excellent structural properties, ability to bind lignocellulosic materials which have high aqueous contents and absence of formaldehyde emissions. The drawbacks of isocyanates are the difficulty of processing due to their high reactivity, adhesion to the rollers, lack of cold adhesion, high cost and the need for special storage. U.S. Pat. 3. 870,655 and German Patent Application Publication No. 2,109,686 describe the use of polyisocyanates (and catalysts for these) in the manufacture of plywood, hardboard, compression molded articles, as well as various technical advantages when used as binders. It is known to treat cellulosic materials with poly (phenylisocyanates) of polymethylene (hereinafter, "polymeric DIM") to improve the strength of the product. Typically, said treatment involves applying the isocyanate to the material and allowing the isocyanate to cure, either by application of heat and pressure (see, for example, US Patents 3,666,593, 5,008,359, 5,140,086, 5,143. 768 and 5,204,176) or at room temperature (see, for example, U.S. Patents 4,617,223 and 5,332,458). Although it is possible to allow polymeric DIMs to cure at ambient conditions, the residual isocyanate groups remain on the treated products for weeks or even months in some cases. The use of toluylene diisocyanate for these purposes is also known. The isocyanate prepolymers are among the preferred isocyanate materials that have been used in binder compositions to solve various processing problems, namely adhesion to the press rolls and high reactivity. U.S. Pat. 4,100,328, for example, discloses isocyanate-terminated prepolymers that improve the release of the product from a mold. U.S. Pat. No. 4,609,513 also describes a process in which an isocyanate-terminated prepolymer binder is used to improve the release of the product. In Patent 5,179,143 a binder composition is disclosed in which a particular type of isocyanate prepolymer is used to improve adhesion at room temperature. A major difficulty of the processing encountered with isocyanate binders is the rapid reaction of the isocyanate with the water present in the lignocellulosic material and any water present in the binder composition itself. One method to minimize this difficulty is to use only lignocellulosic materials that have a low moisture content (i.e., a moisture content of about 3 to about 8%). The low moisture content is generally achieved by drying the raw cellulose material to reduce the moisture content. Said drying is, however, expensive and has a significant effect on the economics of the process. The use of materials that have low moisture content is also inconvenient, since panels made with the dried composite material tend to absorb moisture and swell when used in humid environments. In U.S. Pat. 4,546,039 another approach is described to solve the problem of moisture and the reactivity of the isocyanate. In this described process, raw materials containing lignocellulose and having a moisture content of up to 20% are coated with a prepolymer based on a mixture of diphenylmethane diisocyanate (DI-M). This prepolymer has a free isocyanate group content of about 15 to about 33.6% by weight and a viscosity of 120 to 1,000 mPa-s at 25 ° C. This prepolymer is prepared by reaction of (1) about 0.05 to about 0.5 hydroxyl equivalents of a polyol having a functionality of 2 to 8 and a molecular weight of about 62 to about 2,000 with (2) one equivalent of a a polyisocyanate mixture containing (a) from 0 to about 50% by weight of polyphenylene polyisocyanate and (b) from about 50 to about 100% by weight of an isomeric mixture of diphenylmethane diisocyanate containing a 10 to a 75% by weight of 2,4 'isomer and 25 to 90% by weight of 4,4' isomer. U.S. Pat. No. 5,002,713 discloses a method for compression molding articles from lignoceulose materials having moisture contents of at least 15%, generally from 15 to 40%. In this described method, a catalyst is applied to the lignocellulosic material. A water-resistant binder is then applied to the lignocellulose with catalyst and the coated materials are then formed by compression at a temperature of less than 400 ° F to form the desired composite article. The catalyst is a tertiary amine, an organometallic catalyst or a mixture of these. The binder can be a hydrophobic isocyanate, such as any of the polymeric diphenylmethane diisocyanates, m- and p-phenylene diisocyanates, chlorophenylene diisocyanates, toluene diisocyanates, toluene triisocyanates, triphenylmethane triisocyanates, diphenylether-2, 4'-diisocyanate and polyphenol polyisocyanates. The catalyst is included to ensure that the isocyanate / water reaction is not slowed to such an extent that the pressing time necessary to produce the molded product increases significantly. The pressing of wafer boards, oriented strand boards and parallel strand wood using steam injection and a conventional binder, such as a urea-formaldehyde resin or a polymeric diphenylmethane diisocyanate (DIM) is known. Examples of such known pressing procedures are described in US Pat. 4,684,489, 4,393,019, 4,850,949 and 4,517,147. These processes give a product that has satisfactory physical properties if the binder is completely cured. The completion of the curing of the binder can, of course, be determined by destructive testing of samples that have been allowed to cure for varying amounts of time under the conditions of the process. The curing time to be used during the production process is determined based on the sample that had been completely cured in the minimum amount of time. The drawbacks of that method are easily apparent. A valuable product is destroyed in the test. In addition, any variation in the composition of the wood, in the degree of dispersion of the binder on the wood particles, etc., or in the conditions of the process that will affect the rate of curing of the binder is not taken into consideration in the method described above. U.S. Pat. No. 5,641,819 discloses a process for the preparation of a composition board wherein the fines separated from most of the larger sized wood particles are coated with binder and the mixture is used as a binder so that the larger sized wood particles form the composition board. Here, the fines serve as a vehicle for the urea resin and formaldehyde binder. U.S. Pat. No. 4,944,823 discloses a composition for bonding solid lignocellulosic materials. Suitable binder formulations are based on the reactive mixture of an isocyanate and a carbohydrate material. These are both effective and cheap and eliminate the health risks associated with the use of formaldehyde. The carbohydrate materials include, for example, sugars and starches, in the presence or absence of other active materials. These carbohydrates are mixed with a liquid diisocyanate and applied to the wood, which is then pressed to form a composite product. In U.S. Pat. No. 5,128,407 discloses binder compositions containing urea-extended polyisocyanates derived from a combination of a polyisocyanate and urea which is in solution with water, and the process for preparing the binder compositions. This reference also describes a process for preparing a composite material from crushed particles or sheets of a lignocellulose material, consisting of coating the particles or chapas with these binder compositions. Using the process of this invention, a significant amount of water is added to the wood particles, which must be subsequently removed during the molding operation, with the undesirable result that the press cycle times have to be increased. The large-scale industrial manufacture of composite materials that are exclusively linked with polyisocyanates has previously been limited. The use of some of the polyisocyanates, particularly of the best performance isocyanates, such as polymethylene diisocyanate, has been limited by their cost. Due to the limitations in terms of cost, the level of use of these expensive isocyanates is kept low for a given material. An approach to the use of levels of these isocyanates has involved the prolongation of the isocyanate chain with inexpensive extenders. It is known that organic polyisocyanate resins have excellent adhesion properties and operability as an adhesive for thermocompression molded articles., such as particle boards and medium quality fiber boards produced from a lignocellulosic type material, such as wood chips and wood fibers, and the articles exhibit excellent physical properties. However, the excellent adhesion of the organic polyisocyanate resins causes a drawback, in the sense that the compression molded article adheres firmly to the metal contact surface of the heating plate in a continuous thermocompression or batch process. To overcome the disadvantages of unwanted adhesion to the hot plate, it is required to preliminarily spray a release agent on the surface of the heating plate to form a release layer. Japanese Patent Publication No. 3-21321 discloses a different method of external spraying of release agent, wherein a mixture of an organic polyisocyanate and a mineral wax is sprayed onto the lignocellulose type material before thermocompression molding. . Japanese Patent Application Laid-open No. 4-232004 discloses a method of thermocompression molding of a lignocellulose thi-po material by the addition of a neutral orthophosphate ester as the compatibilizing agent, the wax and the polyisocyanate. U.S. Pat. 5,001,190 and PCT application WO 88/03090 describe a method for filling a space within a structure with a polyurethane compound in the presence of water. Suitable polyurethane compounds consist of (adding) a coarse aggregate to the space of the structure to be refilled, (b) adding a polyurethane binder to the aggregate, where the binder consists of (i) a phenolic resin component consisting of a phenolic resole resin and a hydrophobic solvent system and (ii) a polyisocyanate component consisting of an aromatic polyisocyanate and a hydrophobic solvent and (iii) a urethane promoter catalyst. Isocyanates are known as suitable components for treating cellulosic fiber and wood products. Some methods for this treatment are described, for example, in U.S. Pat. 5,179,143 and 5,674,568. US binders 5,179,143 consist of polyisocyanates, compounds containing at least two hydrogen atoms reactive to isocyanate and alkylene carbonates. Binders for modified cellulose products from the USA No. 5,674,568 consists of a poly (phenylisocyanate) of polymethylene, water and an organic compound having a hydroxy functionality of 2 to 8 and a molecular weight of 60 to 8,000 and which is selected from the group consisting of polyhydric alcohols. free of ester groups, polyether polyols and mixtures thereof. It is the purpose of this invention to provide a thorough process for the production of wood composite products using a reactive polyisocyanate mixture and a co-reactive containing solid deactivated amine as a binder. This improved binder has the advantages of using less of the relatively expensive polyisocyanate to obtain properties comparable to traditional DIM binders. The expanders containing reactive amine act as vehicles for the liquid binder. These expanders do not contain additional water that can increase the press cycle times. The tendency of the resin to adhere to the rollers may also be reduced.

COMPENDIUM OF THE INVENTION This invention relates to a process for the production of wood composite materials consisting of: a) combining wood particles with 1 to 25% by weight, based on the total weight of the wood composite, of a mixing, followed by b) molding or compressing the coated combination. Mixtures suitable for coating the wood particles consist essentially of: 1) a solid dry compound selected from the group consisting of urea, melamine and mixtures thereof and 2) a polymethylene poly (phenylisocyanate) having a functionality of about 2.1 at about 3.5, an NCO group content of about 30 to 33% and a monomer content of about 30% to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2'-isomer, from about 1% to about 20% by weight of the 2,4'-isomer and from about 25% to about 65% by weight of the 4,4'-isomer, based on the total weight of the polyisocyanate; wherein the weight ratio of component a) (1) to component a) (2) is from 10: 1 to 2: 1, preferably from 3: 1 to 7: 1. In another embodiment of the present invention, the method consists of a) combining wood particles with (1) a solid dry compound selected from the group consisting of urea, melamine and mixtures thereof; b) coating the combination of a) with (2) a poly (methylene) poly (phenylisocyanate) having a functionality of about 2.1 to about 3.5, a NCO group content of about 30 to 33% and a monomer content of from about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2'-isomer, from about 1% to about 20% by weight of the isomer 2.4 'and from about 25% to about 65% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate, and (c) molding or compressing the coated combination formed in b). In another alternative embodiment of the present invention, the method consists in a) combining the particles with (2) a polymethylene poly (phenylisocyanate) having a functionality of from about 2.1 to about 3.5, a NCO group content of about 30 to 33% and a monomer content of about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2 'isomer, of about 1% by weight. about 20% by weight of the 2,4'-isomer and from about 25% to about 65% by weight of the 4,4'-isomer, based on the total weight of the polyisocyanate; b) coating the combination of a) with (1) a solid dry compound selected from the group consisting of urea, melamine and mixtures thereof, and (c) molding or compressing the coated combination formed in b). In any of these alternative embodiments, where a component is first applied to wood particles, followed by the second component, the weight ratio of component a) (1) to component b) (2) is 10: 1 to 2: 1, preferably from 7: 1 to 3: 1. The amount of the components a) (1) and b) (2) applied to the wood particles is such that there is from 1 to 25% by weight (preferably from 2 to 10% by weight, more preferably from one to one). 3 to 8% by weight) of these two components present, based on the total weight of the wood composite.

DETAILED DESCRIPTION OF THE INVENTION Polymeric DIM, as used herein, refers to the products of three rings and / or of higher rings derived by phosgenation of the condensation products of aniline-formaldehyde. Suitable polyisocyanates for use as component (2) of the binder compositions in the present invention include those mixtures of polymethylene poly (phenylisocyanates) having a functionality of about 2., 1 to about 3.5 and an NCO group content of about 30% to 33% by weight. These typically have a monomer content of about 30 to 90% by weight, the remainder being polymeric DIMs, ie, higher homologs of the DIM series. The polymeric DIM content comprises up to about 5% by weight of the 2,2'-isomer, from about 1% to about 20% by weight of the 2,4'-isomer and from about 25% to about 65% by weight. weight of the 4,4 'isomer, based on the total weight of the polyisocyanate. A preferred mixture of poly (phenylisocyanate) of polymethylene has a functionality of 2.2 to 2.4, a content of NCO groups of about 31.2 to about 32.8% by weight and a monomer content of about 55% to about 80%, where the monomer content includes no more than about 3% by weight of the 2,2'-isomer, from about 15% to about 20% by weight of the 2,4'-isomer and from about 40% to about 55% by weight of the 4,4 'isomer, based on the total weight of the mixture. This polyisocyanate mixture contains from about 20 to about 45% by weight of polymeric DIM. More preferred polyisocyanates include, for example, polymethylene poly (phenylisocyanate) blends having an average functionality of from about 2.5 to about 3.0, preferably from about 2.6 to about 2.8, a group content. NCO of about 30 to 32% by weight and a monomer content of about 40 to 50% by weight, wherein the monomer content includes not more than about 1% by weight of the 2,2'-isomer, about 2% to about 10% by weight of the 2,4'-isomer and from about 35% to about 45% by weight of the 4,4'-isomer, based on the total weight of the mixture. This mixture of isocyanates contains from about 50 to about 60% by weight of polymeric DIM. Suitable polyisocyanates for use as component (2) of the compositions of the present invention also include those compositions and mixtures of poly (phenylisocyanates) of polymethylene having an NCO group content of about 25 to about 33% by weight and which have a viscosity of less than about 2,000 cps at 25 ° C. The polyisocyanates of the present invention have a functionality of from about 2.1 to about 3.5, preferably from 2.3 to 3.0 and, more preferably, from 2.6 to 2.8 and an NCO group content of about 30% to about 33%, preferably from about 30.5% to about 32.5%, and a monomer content of from about 30% to about 90% by weight, preferably from about 40 to about 70%, where the monomer content includes up to about 5% by weight of the 2,2'-isomer, from about 1% to about 20% by weight of the 2,4'-isomer and from about 25% to about 65% by weight of the 4,4 'isomer, based on the total weight of the composition or mixture. The polymeric DIM content of these isocyanates ranges from about 10 to about 70% by weight, preferably from about 30% to about 60% by weight. Suitable polyisocyanates for component (2) of the present invention also include, for example, mixtures of polyisocyanate mixtures as described above with DIM adducts, including, for example, DIM allophanates, as described above. describes, for example, in U.S. Pat. 5,319,053, 5,319,054 and 5,440,003, the descriptions of which are hereby incorporated by reference, and DIM carbodiimides, as described, for example, in US Pat. 2,853,473, 2,941,966, 3,152,162, 4,088,665, 4,294,719 and 4,244,855, the disclosures of which are incorporated herein by reference. When used in the ranges of the present invention, mixtures of solid amines and polyisocyanate have the consistency of a wet powder or that of brown sugar. The powder binding formulations are applied to wood particles in the manufacture of particle boards, wafer boards, fibreboards, etc., by intermixing a stream of wood particles and a stream of the binder powder form in the desired ratio and using mechanical agitation commonly used in the manufacture of composite products, such as particle board. When powder binders are used to make particle boards or the like, the wood can have a wide range of moisture content, i.e. from about 0.5 to about 10% by weight, based on the total weight of the particles. wood particles. However, it is advantageous if the moisture content of the wood particles is relatively low, that is, in the order of approximately 1 to 6%, and, after the initial pressing and before the final compaction in a hot press , spray the preformed particle board with water to increase the moisture content to 10 or 11%. Alternatively, although less preferred, the binders may be added separately and subsequently mixed together with the wood particles. This is less preferred, since, at least in some cases, the two co-reactants do not mix intimately in the appropriate ratios. As soon as the binder according to the invention comes into contact with the wood, it starts to react with the water contained in the wood. The binder and the resulting products are free of formaldehyde and the compound is produced at a competitive cost with the costs of manufacturing wood products using urea-formaldehyde resin, which has the serious problem of formaldehyde emission. The binder formulation can also be applied to the wood at a higher moisture content, which saves energy by reducing the degree of drying normally required before pressing. Suitable solid dry compounds for use as component (1) of the present invention include urea, melamine and mixtures thereof. The urea, melamine and dry and solid mixtures thereof contain, for the purposes of this invention, less than 10% by weight of water and are preferably in the absence of water. Alternatively, similar compounds can be used, including, but not limited to, guanidine or dicyanodiamide, but are preferably added as mixtures with urea and / or melamine because of their inconvenient tendency to release ammonia. As used herein, the term "dry" means that there is less than 10% by weight of water enclosed in the solid. In principle, known catalysts can be used to accelerate the addition reaction of the isocyanate in the formation of these binder compositions. It is preferred that there is no presence of catalysts in the reaction mixture of the present invention. Suitable catalysts for this purpose include tin compounds, such as dibutyl tin dilaurate or tin (II) octoate. Other catalysts are described in "Kunstoff Handbuch", Volume VII, published by Becker and Braun, Cari Hanser Verlag, Munich, 1983, on pages 92-98. The catalysts are used, if they are, in an amount of about 0.001 to 10% by weight, preferably about 0.002 to 0.1% by weight, based on the total amount of the reactants. Other possible additives and / or auxiliary agents that can be included in the binder compositions of the pre-sent invention include, for example, wax and wax emulsions for reduced aqueous absorption, preservatives, surfactant additives, for example emulsifiers and stabilizers, for release of the mold such as, for example, zinc stearate, etc. In the embodiment of the invention where the melamine or urea content is low, a stabilizer can be used in an amount sufficient to obtain a binder composition having a consistency that allows to work with it. By the term "work consistency" it is meant that in the composition it is in a range such that it ranges from a powder of free flow to that of brown sugar. As indicated before, the percentages of the ingredients in the wood binding compositions according to the present invention can vary widely according to the needs and conditions of a particular application. In general, however, amounts have been adequate in the following ranges, taking into account that the other active materials may include one or more of the catalysts, stabilizing agents and release agents.

A preferred formulation for composite products, such as particle board, consists of a mixture of melamine and / or urea together with isocyanate (DIMP), with or without stabilizing agent, catalyst or release agent. The formulation for a particular product will depend on the species of the wood, the requirements of the physical properties of the resulting product and the conditions of the pressing. For example, a range of formulation for the commercial requirements of raw materials for Douglas pines, for pressed interior particle boards at a press roll temperature of 350 ° F, for a pressing time of 4.4 minutes, with obj ect of obtaining a high quality commercial product are as follows: This binder formulation can be used in an amount of 1 to 25% by weight, expressed as a percentage of the total weight of the wood, or from about 0.25 to 8.0% of DIMP based on the weight of the wood. Preferably, the amount of binder formulation based on the weight of the wood is from 2 to 10%, depending on the configuration of the particulate wood and the requirements of the products. In addition, if a small amount of isocyanate is used in the binder formulation (eg, about 10 to 20% based on the total binder formulation, assuming a relatively dry powder), then relatively higher proportions of binder formulation will be used ( for example, 8 to 10% binder formulation or 1 to 2% isocyanate based on the weight of the wood). On the other hand, when relatively small amounts of binder formulation are used (eg, 2 to 6% binder formulation), then the amount of isocyanate in. the binder powder should be somewhat larger (eg, 25 to 35%) to obtain a sufficient bond; this provides a minimum percentage of isocyanate based on the amount of wood of about 0.5 to 2%. In general, using a preferred powder binder formulation, the maximum amount of isocyanate present will be about 20% based on the binder, or 2% based on wood when 10% binder is used. Although much less preferred, it is also possible to make liquid binder formulations according to the present invention using small amounts of inert, polar and non-aqueous solvent, such as, for example, methylene chloride, or plasticizers such as, for example, benzyl phthalate. butyl or dioctyl phthalate, or novolac resin solutions can also be used in inert, polar and non-aqueous solvents. Liquid binder formulations can have a limited shelf life. Care must be taken to minimize the aqueous content of these dissolved deactivated amines due to the undesirable reaction between the isocyanate and the water prior to the wood bonding operation. The liquid binding formulations according to the present invention can also be prepared by first mixing a relatively large amount of dry deactivated amine with a relatively small amount of isocyanate, allowing the mixture to react to the point where there is no longer any free isocyanate and then adding inert solvent or plasticizer to form a viscous mass. Thus, said viscous mass can be obtained by first mixing isocyanate with urea or melamine in a proportion of 10 to 50% by weight of isocyanate and 50 to 90% by weight of powdered amine, then allowing the mixture to react for 5 to 60 minutes and finally adding 30 to 70%, based on the weight of the mixture, of inert solvent or plasticizer to obtain a viscous mass suitable for the extension with rollers on wooden sheets in the manufacture of wood trachapada. The viscosity can be controlled by adjusting the ratio of the components in the mixture. The binder formulations according to the present invention are prepared by mixing the various components together in the appropriate sequence as indicated above. By producing the preferred powder binders, said mixture preferably implies a vigorous stirring for several minutes, such as in a suitable mill, to ensure a conscientious mixture of the isocyanate with the other components. It is preferable to first mix the isocyanate with the stabilizing agent, the catalyst (if present) and the release agent (if one or more of these latter components are used) and then add the melamine and / or the urea. Of course, the mixing must be carried out for a sufficient time to produce a homogeneous mixture and under vigorous mixing conditions; this will usually occur after several minutes of vigorous agitation. As discussed herein, the polyisocyanate is mixed with a solid urea, a solid melamine and / or a mixture thereof to produce a stable mixture of the invention. The consistency of the mixture can be from that of a free flowing dry powder to that of brown sugar. In the practice of the claimed invention, the amount of the binder composition will depend on the type of materials being formed in a compound, the moisture content and the like. Typically, the binder composition can be used in an amount of 1 to 25% by weight, preferably 2 to 10% by weight and, more preferably, 3 to 8% by weight, based on the weight total wood composite. The process for preparing the composite material from ground particles of fiber, wood or cellulosic materials consists in coating the particles with the binder composition of the claimed invention, which contains a polyisocyanate extended with urea and / or melamine. The reconstituted composite panels are manufactured by mixing the crushed materials with a binder composition while turning or shaking the materials in a mixer or similar mixing apparatus. In general, the binder system is added in an amount equal to 1 to 25% by weight, based on the total weight of the wood composite. If desired, other materials, such as fire retardants, preservatives, waxes, biocides and the like, can also be added to the materials during the mixing step. Specific examples of suitable raw materials containing lignocellulose and which can be bound to the binder according to the invention include, for example, wood, bark, cork, bagasse, straw, flax, bamboo, alfalfa, rice husks, sisal fibers, fibers of coconut, etc. However, articles pressed according to the invention can also be produced from other organic raw materials (ie pieces of plastic of various types) and / or inorganic (for example, mica or silicate beads). In this case, the materials may be present in the form of granules, chips, fibers, beads or powder and may have a moisture content of, for example, 1 to 20% by weight, based on the total weight of the materials bonuses that contain lignocellulose. The following examples further illustrate the details of the process of this invention. The invention, which has been set forth in the foregoing description, should not be limited in spirit or scope by these examples. Those skilled in the art will readily understand that known variations of the conditions of the following procedures can be used. Unless otherwise noted, all temperatures are degrees Celsius and all parts and percentages are parts by weight and percentages by weight, respectively. EXAMPLES In the examples of this invention, the following components were used: Isocyanate A: a mixture of polymeric DIM (DIMP) with a viscosity of about 200 mPa-s and an isocyanate content of 31.5%. Melamine: This substance was purchased from Aldrich Chemical Company, crushed using a mortar and pestle with its hand and screened through a # 45 US mesh screen. Urea: This substance was purchased from Aldrich Chemical Company, crushed using a mortar and pestle with its hand and screened through a # 45 US mesh screen. Sebacic acid: This substance was purchased from Aldrich Chemical Company, crushed using a mortar and pestle with his hand and screened through a # 45 US mesh screen. In all cases (except for example 6), for the purpose of this invention, the sebacic acid was added at 0.5 percent by weight, based on the total weight (wood + binder) of each individual formulation. Procedure for Isocyanate A / Melamine Binder Preparation Two parts of Isocyanate A were combined with one part sebacic acid in a 32 oz. Jar and mixed well. A part and a half of Isocyanate A / sebacic acid was added to seven parts of melamine. Burundi cylinders were added to the 32 oz jar, which was then rolled on a roller table for 1 to 1.5 hours. The container was periodically opened and the material stuck to the walls of the container was scraped. The binder mixture was then screened through a # 40 US mesh screen and placed in the collection pan. The collection pan containing the binder was placed in a desiccator for 3 to 4 hours.

Procedure for the preparation of Isocyanate A / Urea binder Two parts of Isocyanate A (with the exception of Example 6, where four parts were added) were combined with one part of sebacic acid in a 32-ounce jar and mixed well. Isocyanate A / sebacic acid was added to the urea (in the ranges described in the following table) and burundo cylinders were added to the 32 ounce jar. The jug was then rolled on a roller table for 1 to 1.5 hours. The container was periodically opened and the material stuck to the walls of the container was scraped. The binder mixture was then screened through a # 40 US mesh screen and placed in the collection pan. The collection pan containing the binder was placed in a desiccator for 3 to 4 hours. Procedure for the preparation of boards (melamine or urea binders): Particle board raw material was placed in a stainless steel bowl (for use in a Kit-chenAid KSM90 mixer). The binder mixture, now semi-dry, was added in increments of 5 to 10 grams, in the amounts listed in the table. The amount of wood raw material in each example was sufficient to provide a total of 100 parts by weight of wood raw material and binder mixture. Thus, Examples 1-6 used 92 parts by weight of wood raw material, Example 7 used 96 parts by weight of wood raw material and Example 8 used 95 parts by weight of wood raw material. Initially, the raw material was mixed by hand to promote the uniform dispersion of the binder / raw material mixture. The stainless bowl was transferred to the KitchenAid mixer and mixed at the lowest speed for 5 minutes. The resin-coated raw material was then placed in a mold of eight inches by eight inches and pre-pressed by hand. The mold was then placed in a Carver Press (Model M) and pressed to approximately% inch thickness using a pressure of 625 psi at 350 ° F or 400 ° F (see specific examples below) for four and a half minutes. The resulting boards were studied in terms of Internal Bonding Resistance and Thickness Swelling according to ASTM D1037 method: Evaluation of the Properties of the Base Fiber of Wood and of the Materials for Particle Panels.

Table 1. Comparison of extended polyisocyanate binders with urea and melamine Notes: 1 The sucrose sample collapsed after the required exposure to water for water absorption analysis. 2 No analysis was done for this property. A comparison of Examples 2 and 3 (which are representative of the present invention) with Comparative Example 1 illustrates the advantage of using urea or melamine over the use of the carbohydrates used in the closest prior art (see US Pat. 4,944,823). It is difficult to make comparisons where the same pressing temperature and / or board density are not used. Examples 2 and 4 can be purchased directly from each other, since they have the same binder formulation and the same pressing temperature, but different densities. Examples 4 and 5 can be directly compared to each other, since they have the same binder formulation and similar densities, but different pressing temperatures. Example 5 is included to show that the resin completes curing even in the lower temperature range and Example 4 is included to allow to consider the effect of a higher board density. The comparison of Example 2 with Example 7 shows the effect that the addition of more urea has on the effectiveness of the binder. Example 6 shows that the addition of more isocyanate than that used in Example 2 allows an approximation to the level of properties of the much more expensive binder to be made using a larger amount of isocyanate without expander, as illustrated in Comparative Example 8. Although the invention has been described in detail in the foregoing for illustrative purposes, it should be understood that said detail has only that purpose and that those skilled in the art can make variations therein without deviating from the spirit and scope of the invention, except as may be limited by the claims

Claims

1. A process for the production of wood composite materials consisting of: a) combining wood particles with 1 to 25% by weight, based on the total weight of the wood composite, of a mixture consisting of: 1) a dry compound solid selected from the group consisting of: urea, melamine and mixtures thereof and (2) a polymethylene poly (phenylisocyanate) having a functionality of from about 2.1 to about 3.5, an NCO group content of about 30 to 33% and a monomer content of about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2'-isomer, from about 1 to about 20% by weight. weight of the 2,4 'isomer and from about 25% to about 65% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate; where the weight ratio of component a) (1) to component a) (2) is from 10: 1 to 2: 1. and (b) molding or compressing the coated combination formed in a).

2. The method of Claim 1, wherein the wood particles are combined with 2 to 10% by weight, based on the total weight of the wood composite, of a mixture consisting of: 1) a solid dry compound selected from the group consisting of: urea, melamine and mixtures thereof and (2) a polymethylene poly (phenylisocyanate) having a functionality of from about 2.1 to about 3.5, an NCO group content of about 30 to 33% and a monomer content of about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2 'isomer, from about 1 to about 20% by weight of the 2-isomer, 4 'and from about 25% to about 65% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate; where the weight ratio of component a) (1) to component a) (2) is from 10: 1 to 2: 1.

3. The method of Claim 1, wherein the wood particles are combined with 3 to 8% by weight, based on the total weight of the wood composite, of a mixture consisting of: 1) a solid dry compound selected from the group consisting of: urea, melamine and mixtures thereof and (2) a polymethylene poly (phenylisocyanate) having a functionality of from about 2.1 to about 3.5, an NCO group content of about 30 to 33% and a monomer content of about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2 'isomer, from about 1 to about 20% by weight of the 2-isomer, 4 'and from about 25% to about 65% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate; where the weight ratio of component a) (1) to component a) (2) is from 3: 1 to 7: 1.

4. The method of Claim 1, wherein (2) said polymethylene poly (phenylisocyanate) has a functionality of 2.2 to 2.4, a NCO group content of about 31.2 to about 32.8% by weight and a monomer content of about 55% to about 80%, wherein the monomer content comprises no more than about 3% by weight of the 2,2 'isomer, from about 15 to about 20% by weight of the 2.4 'isomer and from about 40 to about 55% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate.

5. The method of Claim 1, wherein (2) said polymethylene poly (phenylisocyanate) has a functionality of from 2.5 to 3.0, a NCO group content of from about 30 to about 32% by weight and a monomer content of about 40% to about 50%, wherein the monomer content comprises no more than about 1% by weight of the 2,2'-isomer, from about 2 to about 10% by weight of the 2.4 'isomer and from about 35 to about 45% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate.

6. A process for the production of wood composite materials consisting of: a) combining wood particles with (1) a solid dry compound selected from the group consisting of urea, melamine and mixtures thereof; b) coating the combination formed in a) with (2) a polymethylene poly (phenylisocyanate) having a functionality of from about 2.1 to about 3.5, a NCO group content of about 30 to 33% and a monomer content of about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2 'isomer, from about 1 to about 20% by weight of the 2-isomer, 4 'and from about 25% to about 65% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate; and c) molding or compressing the coated combination formed in b), wherein the components (1) and (2) are present in such amounts as to have from 1 to 25% by weight, based on the total weight of the wood composite, of components (1) and (2) and the weight ratio of component (1) to component (2) is from 10: 1 to 2: 1.

7. The process of Claim 6, wherein the components (1) and (2) are present in amounts such that there is from 2 to 10% by weight, based on the total weight of the wood compound, of components (1) and (2) .

8. The method of Claim 6, wherein the components (1) and (2) are present in amounts such that there is from 3 to 8% by weight, based on the total weight of the wood compound, of components (1) and (2) and the weight ratio of component (1) to -component (2) is from 7: 1 to 3: 1.

9. The method of Claim 6, wherein (2) said polymethylene poly (phenylisocyanate) has a functionality of 2.2 to 2.4, a NCO group content of about 31.2 to about 32.8% by weight and a monomer content of about 55% to about 80%, wherein the monomer content comprises no more than about 3% by weight of the 2,2 'isomer, from about 15 to about 20% by weight. weight of the 2,4 'isomer and from about 40 to about 55% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate.

10. The process of Claim 6, wherein (2) said polymethylene poly (phenylisocyanate) has a functionality of 2.5 to 3.0, a NCO group content of about 30 to about 32% by weight and a monomer content of about 40% to about 50%, where the monomer content comprises no more than about 1% by weight of the 2,2 'isomer, from about 2 to about 10% by weight of the 2-isomer , 4 'and from about 35 to about 45% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate.

11. A process for the production of wood composite materials consisting of: a) combining wood particles with (2) a polymethylene poly (phenylisocyanate) having a functionality of about 2.1 to about 3.5, a content of NCO groups from about 30 to 33% and a monomer content of from about 30 to about 90% by weight, wherein the monomer content comprises up to about 5% by weight of the 2,2'-isomer, from about 1 to about about 20% by weight of the 2,4'-isomer and from about 25% to about 65% by weight of the 4,4'-isomer, based on the total weight of the polyisocyanate; b) coating the combination formed in a) with (1) a solid dry compound selected from the group consisting of urea, melamine and mixtures thereof; and c) molding or compressing the coated combination formed in b), wherein the components (1) and (2) are present in such amounts as to have from 1 to 25% by weight, based on the total weight of the wood composite, of components (1) and (2) and the weight ratio of component (1) to component (2) is from 10: 1 to 2: 1.

12. The process of Claim 11, wherein the components (1) and (2) are present in amounts such that there is from 2 to 10% by weight, based on the total weight of the wood compound, of components (1) and (2) .

13. The method of Claim 11, wherein the components (1) and (2) are present in amounts such that there is from 3 to 8% by weight, based on the total weight of the wood compound, of components (1) and (2) and the weight ratio of component (1) to component (2) is from 7: 1 to 3: 1.

14. The method of Claim 11, wherein (2) said polymethylene poly (phenylisocyanate) has a functionality of 2.2 to 2.4, a NCO group content of about 31.2 to about 32.8%. by weight and a monomer content of about 55% to about 80%, where the monomer content comprises no more than about 3% by weight of the 2,2 'isomer, from about 15 to about 20% by weight. weight of the 2,4 'isomer and from about 40 to about 55% by weight of the 4,4' isomer, based on the total weight of the polyisocyanate.

15. The method of Claim 11, wherein (2) said polymethylene poly (phenylisocyanate) has a functionality of 2.5 to 3.0, an NCO group content of about 30 to about 32% by weight and a content of monomers from about 40% to about 50%, wherein the monomer content comprises no more than about 1% by weight of the 2,2'-isomer, from about 2 to about 10% by weight of the 2,4-isomer and from about 35 to about 45% by weight of the 4,4 'isomer, based on the total weight of the polyisocyanate.