US20060125152A1

US20060125152A1 - Processes for manufacturing engineered composite objects

Info

Publication number: US20060125152A1
Application number: US11/281,655
Authority: US
Inventors: Douglas Gardner; Xuelian Zhang; Christopher Watt; Lech Muszynski
Original assignee: University of Maine System
Current assignee: University of Maine System
Priority date: 2004-11-17
Filing date: 2005-11-17
Publication date: 2006-06-15

Abstract

Methods for forming composite objects, wherein the methods comprise providing a plurality of material particles, applying a liquid adhesive to at least a portion of the plurality of material particles, wherein the adhesive is comprised of droplets, at least about 80% of the droplets having an average droplet diameter of about 50 to about 200 microns, to form a material/adhesive mixture, and forming the material/adhesive mixture into a composite object.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon, and claims priority under 35 U.S.C. § 119(e) of, provisional U.S. Patent Application No. 60/628,628, filed on Nov. 17, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Various types of engineered composites, including wood-based composites such as flakeboard, waferboard, particle board, and strand board, are known and used in many high-strength and stiffness requirement industries, such as, e.g., construction applications. Strand board, particularly oriented strand board, has enjoyed success as a building material since its introduction to market in approximately 1982.
Engineered composites are materials in which two or more different materials are combined to form a single structure with an identifiable interface between the two or more materials. In general, the properties of the composite depend on the constituent materials and the interface. Engineered composites typically contain molecular bonds between the materials at their interface. One type of engineered composite includes objects prepared by combining numerous discrete pieces of a material with a binder, such as a glue or other adhesive-type material, and compressing, curing or otherwise forming the object into a structure. In general, the goal in the engineered composites industry is to produce such composites to have better or more consistent material properties than an object comprised entirely of either material alone.
Oriented strand board, which falls into this general class of composites, can be produced from wood materials that are reduced to generally linear, flat strands, which are then reconsolidated into durable panels of high mechanical properties. Depending on the intended end-use, production of oriented strand board and other engineered wood composites can require the creation of durable bonds between and among the strands or particles using synthetic adhesives, waxes or modifiers as well as a considerable amount of effort and energy to bond the particles together and provide high mechanical properties, strength, dimensional stability, and durability. This is accomplished in conventional practice though mixing of strands and adhesives and application of heat and pressure to form the composite object.
Small variations in the process parameters of the binding protocol may greatly affect properties of engineered composites, e.g., oriented strand board. Additionally, small improvements and innovation in the area of bonding of materials, e.g., wood strands, may lead to significant production cost savings, improved process efficiency and safety, as well as the manufacture of improved products having enhanced mechanical properties.
In conventional practices used in the manufacture of engineered composites, such as oriented strand board, a resin or other adhesive compound is sprayed on strands of material in revolving blenders through conventional nozzles. This method possesses inherent drawbacks, including difficulty in controlling the size of the droplets of resin that are distributed among the strands. Attempts to control droplet size have included atomization through the use of centrifugal or spinning disk sprayers to apply the resin. With centrifugal or spinning disk atomization or spraying, the resin is accelerated to form droplets. Particle size can be controlled to some degree by modification of the wheel speed, feed rate, sprayer design, etc. However, while some degree of control over droplet size may be achieved, it is far from optimum.
Atomized droplets of resin prepared according to prior art processes can have sizes ranging from sub-micron to approximately two hundred micrometers in diameter, with the average being about seventy micrometers to one hundred micrometers in diameter. Additionally, the prior art atomized resins are also characterized by wide droplet size distributions. Moreover, the droplet size distribution can vary dramatically from one batch to another.
These problems are particularly disadvantageous as the mechanical properties of the end products can be linked to the application of the resin in a specific, optimum droplet size. Thus, e.g., even if the average droplet size is within an ideal range, because of the wide size distribution of the droplets, i.e., as produced by spinning disk atomization, most of the spectrum of droplets and the resin of which they are composed do not contribute to the bond and are wasted. Resin droplets from the lower end of the distribution (smaller than, e.g., about eleven micrometers) can easily become aerosolized and may pose a health hazard for personnel. Removal of such aerosolized droplets from work areas is required and often mandates the use of an expensive exhaust system and filter system in the area where the resin is being applied. Additionally, when using a spinning disk atomizer, excessive resin leaving the spinning disk with substantial kinetic energy may build up on the walls of the blender, necessitating costly cleaning procedures that may require use of hazardous cleaning materials. In either instance, large quantities of resin, which can often be rather expensive, can be wasted. Moreover, large quantities of resin droplets which are outside of an ideal range but which neither accumulate on the walls of the equipment or become aerosolized can still provide less than optimum mechanical properties.
Thus, there exists a need in the art for a manufacturing process for the preparation of engineered composite structures, such as, for example, oriented strand board, that includes improved resin droplet size control, thus narrowing the size distribution of applied resin droplets, as well as eliminating hazardous or otherwise unwanted distribution and waste, and unnecessary costs associated with removal and disposal of waste products.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to methods of forming composites and more specifically, methods of forming composites wherein a narrow distribution of resin droplets are applied to material particles. Composites formed in accordance with the methods of the present invention exhibit improved performance properties with respect to strength and durability, including improvement in properties such as internal bond strength (IB), modulus of rupture (MOR), modulus of elasticity (MOE), and/or thickness swelling (TS). Additionally, composites prepared in accordance with the methods of the present invention can achieve suitable performance properties in accordance with known composites with significantly decreased resin usage. Accordingly, economic advantage in process is realized.
One embodiment of the present invention includes methods which comprise: providing a plurality of material particles; applying a liquid adhesive to at least a portion of the plurality of material particles, wherein the adhesive is comprised of droplets, at least about 80% of the droplets having a diameter of about 50 to about 200 microns, to form a material/adhesive mixture; and forming the material/adhesive mixture into a composite object.
Another embodiment of the present invention includes methods of manufacturing wood composite objects comprising: providing a plurality of wood strands; applying a liquid adhesive to at least a portion of the plurality of wood strands, wherein the adhesive is comprised of droplets, at least about 80% of the droplets having a diameter of about 50 to 200 microns, to form a wood/adhesive mixture; and forming the wood/adhesive mixture into a wood composite object.
Another embodiment of the present invention includes methods of manufacturing composites comprising: providing a plurality of material particles; subjecting a liquid adhesive to an ultrasonic field to form a plurality of adhesive droplets; combining the adhesive droplets and the material particles, to form a material/adhesive mixture; and forming the material/adhesive mixture into a composite object.
In various preferred embodiments of the present invention, a material particle, or more preferably a majority of the material particles are comprised of wood, and more preferably wood strands. In various preferred embodiments, the adhesive comprises a component selected from the group consisting of phenolic resins, isocyanate resins and mixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes various methods of forming composite objects. The methods of the present invention include providing a plurality of material particles. Materials which may be used in forming composites in accordance with the present invention include, but are not limited to wood, glass, fibers (natural and/or synthetic), plastics, metals and mixtures thereof. In various preferred embodiments of the present invention, one or more of the material particles is comprised of wood. In those embodiments directed to forming oriented strand board, a majority of the material particles comprise wood strands.
Certain preferred embodiments of the present invention are directed to methods of manufacturing wood composite panels. One preferred embodiment includes providing a plurality of wood particles and applying an adhesive material to at least a portion of the wood particles, wherein the adhesive comprises droplets, at least about 80% of the droplets having a diameter of about 50 microns to about 200 microns.
Another preferred embodiment includes subjecting an adhesive material to an ultrasonic field to form droplets of resin. The droplets of resin are then mixed or applied to a plurality of wood particles. The wood particles and resin droplet mixture are subsequently formed into a wood composite panel. The invention also provides for wood composite panels prepared by this method and an improved wood composite panel containing resin particles that have been ultrasonically atomized.
The manufacture of wood composite panels having mechanical and physical properties that are similar to or better than the end properties of wood composite panels manufactured by conventional methods are provided by this invention. By “wood composite panel,” it is meant any type of structural board or panel of any dimension(s), including beams, such as structural beams, header beams, floor girder beams, columns, rim board and floor and roof joists. It may be formed in one procedure as a panel, or it may be formed by a continuous production of wood composite material that is subsequently cut into panels. The wood composite panel prepared using the method of the invention may be any type of engineered wood composite panel, depending on the nature and type of wood particles used. For example, the wood composite panel may be particle board, strand board, wafer board, oriented strand board or flatboard. In a preferred embodiment, the panel is an oriented strand board panel.
Dimensions of the panel of the invention may vary depending on the end use of the panel and any standards or regulations promulgated in the jurisdiction in which the panel is to be used. Preferred dimensions may include sheets of about 1220 mm by about 2400 mm (about 4 feet by about 8 feet) to sheets of about 2440 mm by 3600 mm (about 8 feet by about 24 feet). The panels may be of any desired thickness; however, thicknesses of about 6.0 mm (about ¼ inches), about 7.5 mm (about ⅚ inches), about 9.5 mm (about ⅜ inches), about 11.0 mm (about 7/16 inches), about 12.0 mm (about 15/32 inches), about 12.5 mm (about ½ inches), about 15.0 mm (about 19/32 inches) about 15.5 mm (about ⅝ inches), about 18.0 mm ( 23/32 inches), and about 18.5 mm (about ¾ inches) may be preferred.
The panels of the invention exhibit improved or similar physical and mechanical properties, such as workability, nailability, glueability, paintability, weight, thermoresistance, permeability, fire performance, and moisture performance, in comparison to conventionally prepared wood composite panels.
The panel may be of one layer or ply, or it may be of multiple layers or plies. Wood composite panels of about one ply or layer to about ten plies or layers are preferred. The layers may be arranged such that they are each oriented differently relative to one another, especially if the end product is to be an oriented strand board. For example, if the panel is an oriented strand board panel, it is preferred that the structure is made up of layers having strands oriented generally perpendicular to the adjacent layer strands. Alternatively, the layers or plies may be sandwiched between or among one or more layers of an additional material(s).
Such additional materials can include any that confer or enhance the physical, chemical, aesthetic and/or mechanical properties of the end product panel, including but not limited to properties of moisture resistance, resistance to molds, mildews, bacteria and/or other infectious agents, fire or flame resistance, and strength, insulating properties. Such materials may include, but are not limited to layers of enamel, plastics, rubbers, resins, fiberglass, glass, carbon fibers, polymer films or coatings, textiles, ceramics, metal films or sheets, and paper. The additional materials can be applied by any means. For example, they may be applied as preformed layers or sheets, or they may be placed between (among) on the surface of the panel in the form of a powdery liquid or gel and subsequently cured, dried.
Panels may be prepared or adapted for any uses known or to be developed in the art, such as use in single layer floors, use as roof sheathing, use as siding, doors, use in soffets, use as subfloors, underlayment, and wall sheathing. Finished panels may be manufactured to have beveled edges, square edges, or tongue in groove on the long edges, or any other modifications as to shape and/or configuration. Additionally, the flat surfaces of the panels may be smooth or may be textured with additional surface treatments, such as those used to improve traction on sloping roofs. Panels may be for example, unsanded or rough (touch) sanded. The panels may be covered in decorative films or papers.
The methods of the present invention include applying adhesive droplets to the material particles. By “particles,” as used herein, it is meant any type of pieces or fragments that can be used in the formation of engineered composites, including flakes, dusts, chips, wafers, strings, fibers, and/or strands.
In those embodiments wherein the composite object comprises a wood composite panel, such as an oriented strand board, it is preferred that the wood particles are wood strands having a dimension of about three to about seven inches in length and about ⅛ inch to about ½ inch in width.
The wood particles may be obtained from any sources. As is known to a person of skill in the art, renewable wood sources, such as small-diameter rapid growth trees, may be preferred from an ecological and cost perspective. Preferred sources of wood include aspen, southern pine, tulip, and/or yellow poplar. A single type of species may be used and/or a mixture of two or more types of species may be used.
Once timber is obtained, it is debarked, using any process known or to be developed in the art. For example, a Camdio debarker may be used. The debarked wood is then cut into the desired type of wood particle, e.g., chips, wafers, or strands.
The wood particles may be dried or otherwise prepared for use in an engineered wood composite. In some applications, it may be preferred, for example, that the wood particles are dried to a moisture content of about under 15% by weight, preferably about 2 to about 12% by weight or about 3 to about 7% by weight or about 4.5% to about 6% by weight.
The invention provides for application of adhesive droplets to the material particles. The adhesive functions in the composite objects to adhere the particles to one another; therefore, any adhesive known or developed in the art may be used as long as the adhesive(s) selected can serve to bond the particles to one another with sufficient strength. The adhesive(s) may include a thermoset resin, a thermoplastic resin, or a mixture or blend of two or more of the same. Preferred may be phenol-formaldehyde resins and/or urea formaldehyde resin.
More preferred are isocyanate resins or phenolic resins. Such resins include isocyanate resins that are synthesized from one or more isocyanate and/or polyisocyanate compound(s) (functional group —N ═C ═O) and alcohols or water (functional group —OH), joined through a urethane or polyurea linkage. Suitable isocyanates or polyisocyanate components for this synthesis include diphenylmethane diisocyanate, m- and p-phenylene diisocyanates, chlorophenylene diisocyanate, αα-xylenene diisocyanate, 2,4- and 2,6-toluene diisocyanate, triphenylmethane triisocyanates, 4,4′-diisocyanate diphenyl ether, and polymethylene polyphenyl polyisocyanates. Also included are all phenolic resins known or to be developed in the art, such as any that are obtained by the reaction of a phenol(s) and an aldehydes(s). Phenols suitable for such reaction include, but are not limited to, phenol, cresol, xylenol, p-tert-butylphenol, and/or p-resorcinol. Aldehydes suitable for this reaction may include formaldehyde and furfural.
Suitable resins may include, but are not limited to phenol-formaldehyde resin, urea-formaldehyde-resin, melamine-urea-formaldehyde resin, resorcinol-formaldehyde, resorcinol-melamine-formaldehyde resins, phenol-resorcinol-formaldehyde, and polyvinyl acetate.
Regardless of the resin(s) selected, one can prepare the resin him or herself using routine methods. Alternatively, the selected resins(s) may be purchased from a commercial supplier. For example, phenolic and/or isocyanate resins are readily available, e.g., from Huntsman Chemical Company, West Footscray, Australia and/or Dow Chemical Corporation, and Bayer Chemical.
Additionally, if desired, additives can be compounded into the adhesive(s) prior to application onto the material particles. Any and all additives known or to be developed may be used. In those embodiments of the invention wherein the adhesive is subjected to an ultrasonic field, the physical and or chemical properties of the adhesive that permit ultrasonic atomization should not be substantially altered by applying the adhesives. Additives may include those that enhance, confer, alter or modify an end property desirable in the adhesive or the composite object and/or that aids in the processing or atomization of the adhesive. Such materials include plasticizers, viscosity modifiers, flame retardants, surface tension modifiers, biocides, and/or colorants. As used herein, “adhesive” can refer to one or more adhesives alone, or in combination with one or more additives.
The viscosity of the adhesive(s) used can vary depending on various parameters, including in such the embodiments, the capabilities of the ultrasonic device employed. Viscosity modification of the adhesive(s) can be accomplished, for example, via temperature alteration and/or the addition of rheology modifiers known in the art or to be developed. The viscosity of the adhesive may preferably be about 150 to about 400 centipoise at 25° C., with a dynamic viscosity of about 200 to 300 centipoise at 25° C. being more preferred. Viscosity measurements recited herein were obtained using ASTM D2196-99 Test Method for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield type) Viscometer (1999), the contents of which are incorporated herein by reference.
The amount of applied adhesive relative to the amount of particles and/or other components will vary depending on several factors, including the type and nature of material used, type of adhesive(s) used, environmental conditions in the forming facility and/or the properties desired in the end product. However, in those embodiments wherein wood particles are combined with an adhesive(s), it is preferred that the wood particles are present in the end product in an amount of about 90% to about 99% by weight, preferably an amount of about 95% to about 98% by weight or about 96% by weight to about 97.5% by weight. Adhesive is preferably present in the end product in an amount of about 1% to about 10% by weight, about 2% to about 8% by weight, and about 2.5% to about 9% by weight.
In certain preferred embodiments of the present invention an adhesive is subjected to an ultrasonic field, to form adhesive droplets. In more preferred embodiments of the invention, the ultrasonic field is applied by feeding an adhesive stream through an ultrasonic atomizer. Preferably, the ultrasonic frequency to which the resin is subjected is about 20 kHz to about 60 kHz, with a frequency of about 20 kHz to about 40 kHz being preferred. Generally, the resin stream is fed to the ultrasonic atomizer at any flow rate which is less than the stall rate when the atomizer is at maximum voltage input. Stall flow rate can vary depending on the combination of such factors as the viscosity of the adhesive, size of the adhesive delivery tubing, ultrasonic frequency and power input to the atomizer. Generally, it is preferred that the flow rate is as large as possible, while still below the stall rate. For example, in an embodiment employing a lab scale ultrasonic atomizer having a flow rate of about 3 to 20 liters per hour for a particular viscosity adhesive formulation, the flow rate employed is preferably at least about 10 liters per hour, and more preferably at least about 15 liters per hour. Suitable and preferable flow rates for any combination of adhesive viscosity and atomizer power input at a specific ultrasonic frequency can be readily determined. Thus, for example, a preferred flow rate is at least about 50% of the maximum flow rate for any given atomizer and viscosity combination. More preferably, the flow rate is at least about 75% of the maximum flow rate.
Suitable ultrasonic atomizers can be built using known designs and materials, or may be constructed using designs and materials to be developed in the art, and can also be obtained commercially from, for example, Cole-Parmer, Vernon Hills, Ill. and Sono-Tek, Milton, N.Y.
The adhesive is applied to the plurality of material particles in the form of droplets. The droplets in accordance with the present invention have a size distribution wherein a majority of the droplets are within a relatively narrow range of sizes. In certain embodiments of the present invention the adhesive comprises droplets wherein at least about 80% of the droplets have a diameter of from about 50 microns to about 200 microns. More preferably, the adhesive comprises droplets wherein at least about 90% of the droplets have a diameter of from about 50 microns to about 200 microns. Even more preferably, the adhesive comprises droplets wherein at least about 95% of the droplets have a diameter of from about 50 microns to about 200 microns.
In certain more preferred embodiments of the present invention, the majority of adhesive droplets have a diameter of from about 50 microns to about 175 microns. Preferably, the adhesive comprises droplets wherein at least about 80% of the droplets have a diameter of from about 50 microns to about 175 microns. More preferably, the adhesive comprises droplets wherein at least about 90% of the droplets have a diameter of from about 50 microns to about 175 microns. Even more preferably, the adhesive comprises droplets wherein at least about 95% of the droplets have a diameter of from about 50 microns to about 175 microns.
In certain even more preferred embodiments of the present invention, the majority of adhesive droplets have a diameter of from about 60 microns to about 160 microns. Preferably, the adhesive comprises droplets wherein at least about 80% of the droplets have a diameter of from about 60 microns to about 160 microns. More preferably, the adhesive comprises droplets wherein at least about 90% of the droplets have a diameter of from about 60 microns to about 160 microns. Even more preferably, the adhesive comprises droplets wherein at least about 95% of the droplets have a diameter of from about 60 microns to about 160 microns.
The adhesive droplets are applied to the selected material particles. This may be accomplished by any means known or to be developed in the art. In certain preferred embodiments, the adhesive may be atomized into a fine fog of resin droplets which are captured with a rotating or agitating container containing wood particles. As the adhesive droplets are applied, the container containing the wood particles may be rotated or agitated to ensure homogenous blending of the adhesive and the wood particles. Alternatively, the wood particles may be mixed or otherwise agitated by an additional apparatus such as a mixer.
Other components may be added to the material particles, either before, after and/or during the application of the adhesive. For example, one may wish to add a neat wax or a wax emulsion to the material particles. The neat wax or wax emulsion may be added in powder or liquid form and dispersed throughout the particles by any means including mixing and rotation. If introduced in a liquid form, such additional components may be applied in droplet form, for example by conventional techniques, or more preferably in a manner identical to the application of adhesives in accordance with the present invention. Preferred neat waxes or wax emulsions include all known or developed in the art for use in engineered composite products, preferably wood composites, including, for example, montan wax, carnuba wax, beeswax, bayberry and myrtle wax, candellia wax, karenday wax, castor bean wax, espartograss wax, Japan wax, paraffin wax, lanolin, sugar cane wax, ceresin wax, halowax, wurikuri wax, shellac, spermaceti wax, sugarcane wax, wool lanolin wax, slack wax, or emulsions thereof. Cascowax EW Series and Cascowax SW 300 R/S series, available from Borden Chemical, lignosulfonate-stabilized wax emulsions, and/or the wax compositions described in U.S. Pat. Nos. 6,066,201; 5,968,237; 4,468,254; 4,339,276; and 5,695,553.
If desired, other components may be added such as antimicrobial components, borate compounds flame retardants, antimycotic compounds, insecticides, biocides, glues or adhesives, and casein glue. These compounds can be added to the material particles either before, after, or while the adhesive is being applied.
Subsequent to the application of the adhesive and/or any other desired additional components, the adhesive/material particles mixture is formed into a composite object. Generally, composite objects are formed by application of heat and/or pressure. In one embodiment of the invention, adhesive-coated wood particles are formed into panels. For example, panels can be produced by hand laying up the wood particles into a random mat in fixed frame deckle box on a metal caul plate, and compressing the mat using a manually controlled, electronic-heated hot press.
If oriented strand board is being prepared, the coated wood particles may be formed into mats. The wood particles are oriented either by an electrical field, or more commonly, aligned mechanically either manually or by vibrating the particles through fins. The arrangement of the alignment depends on the type of oriented strand board to be prepared. For example, the wood particles may be aligned at the top and bottom layers running the length of the panel and the core particles running across the panel. During this process, a mat of strands is built up, with each layer being laid down separately along the conveyor belt, the final mat with several plies is continuous, and is between 100 and 200 millimeters high. At this point, as is known to those skilled in the art, the resin is not yet cured.
In the press, the mats are heated to approximately 185 to 205° C. and are compressed to a specified thickness, discussed above. The heat and pressure produced by the press cause the resin coating the wood particles to cure. The pressure also causes a tangling of the fibers of the wood particles, increasing the strength of the resultant panels. The panels are allowed to cool until the curing process is complete and equilibrium moisture content is reached.
Subsequently, each panel can be dry conditioned at a relative humidity of 65±2% and at a temperature of about 68° F. for approximately fourteen days.
The present invention will now be illustrated in more detail by reference to the following specific, non-limiting example.

EXAMPLE 1

Resin Spraying:
Droplet size distribution of three separate materials was evaluated using a Sono-Tek ultrasonic spray nozzle, Model No. S/N 25048, fed by a Cole-Parmer digital pump. Droplet size analysis was carried out using a Malvern Spraytec laser diffraction drop size analyzer. The ultrasonic spray nozzle had an operating frequency of 25 kHz and an atomizing surface diameter of 0.46 inches. The power generator had a maximum input power of 15 watts. The laser wavelength of the drop size analyzer was 760 nm, with a 100 mm lens. The pump was connected with L/S 13 tubing and a pulse dampener. The four materials analyzed were: Material A, a pMDI adhesive resin (“polymeric methylene diphenyl diisocyanate”), obtained from Huntsman; Material B, a Borden “E-wax”; Material C, a lignosulfonate-stabilized wax emulsion; and Material D, a phenol-formaldehyde (PF) resin, Prefere™ 13B024 obtained from Dynea Company.

Both wax materials and the pMDI resin were successfully atomized at room temperature. The droplet sizes were measured using the Malvern Spraytec analyzer. The distance between the nozzle tip and the laser beam was 75 mm, and the nozzle tip temperature was approximately 75.5° F. All droplet size determinations were derived from the stable spray phases based on percent laser transmission. The results of the analyses are set forth below in Table 1.

TABLE 1


		Max Flow Rate	Power
Material	# of Samples	(ml/min)	(Watts)

A	74	36	5.0
B	166	4	11.0
C	71	36	9.0
D	101	36	6.6

	Dv(10.0) Avg.		Dv(90.0) Avg.	Std.	Avg.
Material	(μm)	Std. Dev.	(μm)	Dev.	(μm)

A	61.28	2.51	159.73	8.67	90.77
B	51.38	3.97	181.16	8.36	102.45
C	77.33	2.13	185.06	3.66	113.23
D	62.7	1.75	154.58	10.17	92.14

Dv(10.0) represents the average droplet diameter of all samples measured at the tenth percentile along the size distribution curve and Dv(90.0) represents the average droplet diameter of all samples measured at the ninetieth percentile along the size distribution curve.
Accordingly, from the experimental data, it can be seen that for Material A (pMDI resin), approximately 80% of the droplets (between the tenth and ninetieth percentiles) have diameters between 61.28 μm and 159.73 μm, on average, with an extremely small standard deviation evidencing the significantly improved reproducibility of size distribution from batch to batch. Furthermore, from the experimental data, it can be seen that for Material D (PF resin), approximately 80% of the droplets (between the tenth and ninetieth percentiles) have diameters between 62.7 μm and 154.58 μm, on average, again, with an extremely small standard deviation evidencing the significantly improved reproducibility of size distribution from batch to batch. Additionally, the significantly reduced amount of atomized resin having sizes outside this range is a vast improvement over the prior art in terms of efficient resin utilization. Moreover, as shown by the data concerning Materials B and C, droplet size distribution of wax additives may also be adequately controlled.

EXAMPLE 2

Oriented Strand Board Production:
Oriented strand board is a type of layered particle panel product composed of strand-type flakes that are purposefully aligned in directions (usually perpendicular relative to one another) that make a panel that is stronger, stiffer, and exhibits improved dimensional properties in the alignment directions. Oriented strand board is manufactured from flakes which are cut, dried, and screen classified. After drying, a phenol-formaldehyde resin-adhesive is spray applied to the flakes using an atomizer as described above in Example 1 in conjunction with a tumbling blender. The flakes are conveyed to aligners which orient the board layers. The flake mats are then conveyed on screens to the stacker prior to insertion into a hot press. After pressing, the boards are hot stacked. Final preparation includes trimming, sanding, edge coating, and grade stamping.
The usual products for oriented strand board are manufactured for residential light frame construction including subflooring and wall and roof sheathing. Other products include shelving, crating and miscellaneous applications. For each oriented strand board prepared, it is suggested that determination of physical and mechanical properties of the panels are determined as set forth in ASTM D-1037 (2003), the contents of which are incorporated herein by reference.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A method comprising:

providing a plurality of material particles;

applying a liquid adhesive to at least a portion of the plurality of material particles, wherein the adhesive is comprised of droplets, at least about 80% of the droplets having a droplet diameter of about 50 to about 200 microns, to form a material/adhesive mixture; and

forming the material/adhesive mixture into a composite object.

2. The method according to claim 1, wherein one or more of the material particles is comprised of wood.

3. The method according to claim 1, wherein a majority of the material particles are comprised of wood.

4. The method according to claim 1, wherein at least about 90% of the droplets have a droplet diameter of about 50 to about 200 microns.

5. The method according to claim 1, wherein at least about 80% of the droplets have a droplet diameter of about 50 to about 175 microns.

6. The method according to claim 1, wherein at least about 90% of the droplets have a droplet diameter of about 50 to about 175 microns.

7. The method according to claim 1, wherein at least about 80% of the droplets have a droplet diameter of about 60 to about 160 microns.

8. The method according to claim 1, wherein the adhesive comprises a resin.

9. The method according to claim 1, wherein the adhesive comprises a component selected from the group consisting of phenolic resins, amino resins, melamine resins, urea-formaldehydes, isocyanate resins and mixtures thereof.

10. The method according to claim 1, wherein the adhesive comprises an isocyanate resin.

11. The method according to claim 1, wherein the adhesive comprises a phenolic resin comprising at least one phenol moiety selected from the group consisting of phenol, cresol, xylenol, p-tert-butylphenol and p-resorcinol, and at least one aldehyde selected from the group consisting of formaldehyde and furfural.

12. The method according to claim 1, further comprising adding a wax component prior to the forming of the material/adhesive mixture into a composite object.

13. The method according to claim 12, wherein the wax component is a liquid wax contained in one or more of the droplets.

14. The method according to claim 12, wherein the wax component comprises a lignosulfonate-stabilized wax emulsion.

15. The method according to claim 1, wherein forming the material/adhesive mixture into a composite object comprises applying heat, pressure or a combination thereof to the mixture.

16. The method according to claim 1, wherein forming the material/adhesive mixture into a composite object comprises subjecting the mixture to heat sufficient to cure the liquid adhesive.

17. A method of manufacturing a wood composite object comprising:

providing a plurality of wood strands;

applying a liquid adhesive to at least a portion of the plurality of wood strands, wherein the adhesive is comprised of droplets, at least about 80% of the droplets having a droplet diameter of about 50 to 200 microns, to form a wood/adhesive mixture; and

forming the wood/adhesive mixture into a wood composite object.

18. A method of manufacturing a composite comprising:

providing a plurality of material particles;

subjecting a liquid adhesive to an ultrasonic field to form a plurality of adhesive droplets;

combining the adhesive droplets and the material particles, to form a material/adhesive mixture; and

forming the material/adhesive mixture into a composite object.

19. The method according to claim 18, wherein subjecting the liquid adhesive to the ultrasonic field comprises feeding the liquid adhesive through an ultrasonic atomizer.

20. The method according to claim 18, wherein the ultrasonic atomizer has an operating frequency of about 20 to about 40 kHz.

21. The method according to claim 18, wherein one or more of the material particles is comprised of wood.

22. The method according to claim 18, wherein a majority of the material particles are comprised of wood.

23. The method according to claim 18, wherein the adhesive comprises a component selected from the group consisting of phenolic resins, amino resins, melamine resins, urea-fromaldehydes, isocyanate resins and mixtures thereof.

24. The method according to claim 18, further comprising adding a wax component prior to the forming of the material/adhesive mixture into a composite object.