Abstract:
An improvement to existing board manufacturing process which utilize lignocellulose particles is described wherein the adhesive to be applied as a binder is at least partly applied before the particles are dried. Using the invention improvement in resin application rates without increase in the water content of the particles fed to a press is achieved. Reduction in edge thickness swelling has been achieved.

Description:
This application claims benefit of Provisional Application 60/240,976, filed Oct. 18, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A method for making particle board having low edge thickness swelling utilizing an adhesive, such as a phenol formaldehyde (PF) resin, is disclosed. The method avoids emissions of ammonia and produces low NO x  emissions by tailoring the adhesive used to the process conditions. Apparatus is also provided such that the application of the resin to lignocellulosic particles is effected in a particular sequence which enables the production of building boards having low edge thickness swelling with no ammonia emissions and low NO x  emissions. The resulting lignocellulosic particle boards have novel and unexpected properties. 
     2. Description of the Related Art 
     The manufacture of building board of particles adhered by an adhesive such as those obtained by PF binders is a well established art, as described, for example, in U.S. Pat. No. 1,358,394 to Redman et al issued in 1920 (incorporated by reference in its entirety). Therein is described the method of producing a phenolic condensation product by combining a phenol substance, such as phenol, with an active methylene substance, such as formaldehyde, and after mixing with a filler, may be molded in hot presses. 
     PF resins had become the adhesives of choice for manufacturing durable heat- and moisture-resistant wood based composites. They are low in cost and provide the high strengths required for structural applications. 
     However, as organic solvents became unacceptable in the building panel production processes, due to health, environmental, and flammability considerations, phenolic wood binders were provided as either aqueous resoles or spray-dried resole powders. The powder form is limited in its ability to provide properties because a secondary binder must be applied to cause the PF powder to adhere to a wood surface until the pressing step. Generally, the secondary binders are capable of retaining only about 3 wt % PF powder on the surface of the wood particles. While this amount may be sufficient for many commodity panels, it is often insufficient for developing the high strength or low moisture responses required of high value speciality applications. 
     On the other hand, liquid resins, such as aqueous resoles can be applied at much higher levels. At these higher-levels, they are much- more capable than powders for developing the high strengths and low moisture responses required of the speciality panel products. Though more flexible than powders, the aqueous resoles are also limited in their abilities due to the effects of the additional moisture that is carried into the system, since as the amount of aqueous resin increases, so does the weight of the aqueous vehicles for the resin. This added moisture slows the cure of the resin and may inhibit development of full cross-linking, thereby adversely diminishing the strength of the adhesive. The moisture also softens the wood substrate reducing pressure between mating wood surfaces. Furthermore, as presses heated above the boiling point of water are commonly used in the board industry to increase production speeds by accelerating the cure of the binder, the existence of additional moisture (&gt;12%) may create high internal steam pressures during the hot pressing, leading to blows and sub-optimal adhesive contributions due to resin migration in response to steam flow. In addition, the heat applied in prior art processes increased the emission of noxious gases, such as ammonia, and if the plant is provided with a Regenative Thermal Oxidizer (RTO), the ammonia may be converted to NO X . If the plant does not have an RTO, or some other heat system that puts resin emissions through a burner, there will be no NO x  formed, although in that case ammonia would be emitted to the atmosphere. Thus, although the increased addition of resin via an aqueous vehicle may lead to better properties, the process is inherently limited as a result of the concurrent moisture additions in the form of the aqueous vehicle for the resin. 
     The lignocellulosic particles commonly utilized in many panel producing method, such as those for making oriented strand board (OSB), typically used in sub-flooring, roof sheathing, siding and wall sheathing, along with other specialty applications, already contains moisture inherently, or introduced during preliminary processing steps. 
     For example, when logs of wood enter the manufacturing facility, they are typically placed in a vat or “hot pond” to-help thaw the wood and/or remove dirt and grit from the logs before debarking the same. Alternatively, the logs may be retained in an outside storage lot before being brought into the manufacturing facility for flaking. Each of these techniques introduces moisture into the logs. 
     Debarked logs are “flaked” in flakers to provide flakes having certain properties, such as specific length, width and thickness. This results in “green flakes.” Green flakes are undried and typically have moisture contents between 20 and 80 wt % moisture content on an “oven-dried” basis, i.e., the weight of the flakes after oven drying. 
     Typically, the green flakes are stored in a “green bin” or “wet bin” before drying to prespecified specified manufacturing moisture content. The green flakes thereafter are sent to driers to dry the flakes to a typical moisture content of about 2 to about 10 wt %. Dried flakes are stored in “dry bins” or “dry flake bins” until blended. 
     Blending is where adhesive (binders), catalyst, water and wax (emulsion or slack) are typically added to the dried flakes. Such binders are typically PF resole resin or pMDI. PF resin binders are typically applied at rates between 1.7%-8.0% (based on a wt % of solid binder to oven-dry wood). The blended flakes are transferred to forming bins, which are used to meter the flakes onto a forming surface, such as a forming belt. The forming bins contain “orienter rolls or discs” which orient the flakes in either the direction of the forming line or transverse to the direction of forming line travel. The forming bins also control the limit of the amount of flakes falling onto the forming surface, which controls the finished panel density, which is usually between 36 and 50 pounds per cubic foot. 
     The forming surface travels under forming heads creating a continuous mat of oriented flakes. These mats are typically cut to specific lengths and loaded onto a “pre-loader” or loading cage” which is a staging area for a full “press-load” of mats. 
     The mats are pressed to specific thickness and the resin cured to result in a finished panel. The conditions of elevated temperature, pressure, and time can be varied to control the cure time. Catalyst can also be introduced during the processing steps to optimize the pressing times or to shorten the overall pressing time. 
     The finished panels are thereafter usually cut to size, stacked, painted and packaged for delivery to the customer. 
     Attempts have been made to reduce press time by preheating the flakes on the forming surface, such as disclosed in U.S. Pat. Nos. 5,643,376 and 5,733,396 to Gerhardt et al (incorporated by reference in their entirety). Therein, a particle mat is heated by concurrently passing through the mat treatment air coming from an air-conditioning system and having a predetermined moisture content and dew point such that the mat is preheated to a predetermined temperature while liquid in the treatment air is allowed to condense in the mat to, at most, a maximum liquid content. Other attempts to preheat the mat employs the use of microwaves; See, U.S. Pat. No. 5,913,990 to Kramer, or steam; See, U.S. Pat. No. 5,993,709 to Bonomo, or hot-air; See, U.S. Pat. No. 6,054,081 to Bielfeldt, prior to the pressing step (all patents are herein incorporated by reference in their entirety). 
     Other attempts for introducing an adhesive into green flakes can be found in Canadian Patent 1,135,610, issued in 1982. Processes for introducing adhesive into green flakes, as well as into the same flakes after drying, was disclosed in Canadian Patent 989,289, issued in 1976. 
     However, none of these processes teach a method of introducing an adhesive, in the form of either a powder or an aqueous form, to the “green flakes,” i.e., before the flakes are initially dried to a predetermined moisture content, with no ammonia and low NO x  emissions occurring during one of the subsequent drying and/or pressing steps. 
     SUMMARY OF THE INVENTION 
     A method is provided for introducing a powder or aqueous resin adhesive, preferably a PF resole binder, to green flakes before they are dried, with little or no formaldehyde or ammonia emissions and low NO x  emissions. 
     The invention also provides an apparatus suitable for forming building panels, particularly OSB panels from green particles by means of a hot press wherein at least a part of the resin binder is introduced, in aqueous or powder form, prior to the drying of the green particles. 
     Building panels having high strength and low edge swells and formed of lignocellulosic particles and a PF adhesive, having low NO x  emissions and little or no ammonia or formaldehyde emissions when dried and/or pressed under heat and pressure are provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a flow diagram of a typical prior art OSB making process. 
     FIG. 2 is a flow diagram of a building panel manufacturing process according to the invention. 
     FIG. 3 is a flow diagram from the wood yard through a building panel manufacturing process in an alternative embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, is a flow chart of a typical prior art process for making OSB. The flaker  10  forms the flakes, discharging the flakes via a take-away conveyor or drop chute  21  to the “green” or “wet bin”  20 . The discharge from the “green” or “wet bin”  20  to the dryer  30  can be via doffing rolls or drop chutes  22 . The dried flakes exiting dryer  30  can be stored in dry bin  40  or fed directly to blender  50  where they are mixed with other compounds, such as an adhesive  11 , wax  12 , catalyst  13 , etc. After mixing, the mixture is discharged to a forming bin  60 , fed by conveyors, such as forming belt  65  to a staging area  70 . From the staging areas  70  mats of particles, adhesive, water, and other components are fed to press  80  where they are treated, under heat and pressure, to consolidate the particles and cure the adhesive, typically a PF resin. 
     We have found that the total application of resin, to the blender  50  as in the prior art, which inherently introduces water, in the form of the aqueous resin component, is deleterious to the formation of building panels for high value uses. After study, we have found that at least a portion of the adhesive can be applied to the lignocellulosic particles before the particles are dried. Convenient sites for application are shown in FIGS. 2-3. For example, in FIG. 2, the flakes being discharged from flaker  10  can have resin applied as they exit the flaker via a take-away conveyor or drop chute  21 . Resin application  14  can be by spray nozzles (air assisted or non-air assisted) (not shown) or through a conventional spinner disc atomizer (not shown). Other methods of applying resin such as falling curtain may be employed so long as the choice of application ensures that the desired amount of resin is applied uniformly to the flakes. Dilution of the resin optimizes resin distribution. It is typical in the wood industry to run resins from 100% solids (powder resole resins) to 15% diluted resin solids. There is significant data to show that powder resins provide excellent distribution when compared to the liquid resins. 
     This application rate at resin application  14  can be 0% (as in the conventional process) to about 30 wt %. 
     However, typical resin application of PF resins can result in at least one of several types of deleterious emissions. Either formaldehyde, ammonia or NO x , or each, can be emitted during such a process during one or both of the drying or pressing steps of the process necessary to transition a mixture of particles and adhesive into a consolidated mat of parties bonded by an adhesive. 
     Even when an additional or alternative resin application is performed upon exit of the green flakes from green or wet bin  20 , there can be the deleterious emission of ammonia, or NO x  gases upon passage through an RTO or other emissions burner. The discharge of green or wet bin  20  is usually via doffing rolls and drop chutes  22 . Application of a resin  15  can conveniently be applied at this point. The application points in the present invention can be varied based on several factors of the process design, including chute design, wood flow over doffing rolls, distance and space availability for the application hardware, etc. 
     The amount applied at application of resin  15  can be the same or different from that applied at other locations in the process, e.g., to that applied at  14 . The type of resin applied can also vary, e.g., powder at  14 , aqueous solution at  15  (or  11 ). 
     In the alternative embodiment of FIG. 3, resin application may commence as early as in the hot pond  105 , or treatment vat  106  by addition of resin into these areas. Alternatively, resin may be applied as the logs are transported from wood yard  107  to flaker  10 , or to hot pond  105 . Alternatively, logs can be sent from the wood yard  107  to special treatment vat  106  for resin application before being fed to flaker  10 . In another alternative, after thawing the logs in hot pond  105 , the logs may be sent to treatment vat  106  (via the route shown in dotted line  108  in FIG. 3) for resin application. 
     Although we have specifically illustrated resin application at one or more points prior to drying, it would be within the skill of the worker in the art, upon reading the disclosure of the invention, to apply resin prior to, during or after flaking, in the green or wet bin, or in multiple points along the process in order to provide the required resin. Still further, it is possible to supplement the present process of resin application after the dryer, by providing additional resin prior to the drier according to the invention. 
     We have found a way in which the emission of free formaldehyde, ammonia and/or NO x  can be reduced whether the resin, used as an adhesive, is applied prior to the drier, subsequent to the drier, but before the pressing step and/or both prior to the drier and subsequent to the drier, but prior to the pressing step. 
     Our discovery lies in our recognition that the prior art processes, during curing of the PF resin, produced an ammonia emission, due to the presence of urea, usually added subsequent to formation of the PF resin, as a component of the adhesive which was thought to eliminate free-formaldehyde emissions. 
     The presence of free urea, added to a PF resin, has been found to release ammonia in both the drying step, as well as in the pressing step when used in prior art processes when resin is added after the drying, but before the pressing step; before the drying step or when resin is added both before and after the drying step. 
     We have found that by adding urea to a PF resin, followed by the addition of formaldehyde, forming methyol urea, which, when used in the present process, is less likely to give ammonia (or NO x  if emissions are fed to an RTO or other burner) than a PF resin to which urea alone has been added. 
     The presence of methyol urea, with a PF resin, can then be used as the adhesive which is added before the drying step, after drying, but before pressing, or both, without creating an emission of free-formaldehyde as well as reducing the emission of ammonia (or NO x ) in either the drying or pressing steps. 
     The total amount of resin in the final product includes that added prior to the drier, e.g., at the hot pond  105 , and/or treatment vat  106 , in the flaker  10  and/or green or wet bin  20 , resin application  14 , application of resin  15  and adhesive  11 , and can be adjusted so that the new building panels made by the process of the invention maintains the current commodity board densities of 37 to 43 lb/ft 3 . However, it is possible to increase the total resin content by the present invention to exceed those densities without introducing excessive moisture into the blended particles or increasing formaldehyde, ammonia or NO x  emissions. 
     Current cure times can be maintained even with higher resin contents so that production rates and volumes are not hampered. While press temperatures between 300° and 460° F. can be used, desired targets are still between 380° and 430° F. The lower press temperatures generally do not allow for good mat consolidation and heat transfer within the mat as it is being pressed. However, it is also possible to combine the prior art steps of preheating the mats before pressing with the resin addition prior to heating of the flakes, which occurs prior to mat formation. Generally, temperatures exceeding 430° F. present a fire hazard in the current mill environments. 
     In other embodiments according to the invention, the application of the resin prior to the drying makes it possible to eliminate the blending system completely. This is shown by the dotted line in FIGS. 2-3. 
     Industrialization according to the alternative embodiment could save significant capital and maintenance costs associated with installation and upkeep of the current blending systems. In another alternative, it is also possible to move the blender  50  and its associated adhesive  11 , wax  12  and/or catalyst  13 , to a point upstream of the drier, e.g., between the flaker  10  and the green or wet bin  20  or, alternatively, after the green or wet bin  20 , but before dryer  30 . 
     It is also possible to eliminate the wax  12  from the process altogether. It is apparent that such elimination would achieve significant savings and, furthermore, board density could be reduced to a lower spectrum of from about 28 to about 32 lb/ft 3 . While we have described the particles as lignocellulosic, we do not envision that the form of particles is limited to strands as it is equally suitable for particles in the form of long or short fibers, flakes, chips and/or combinations thereof with veneers. The methods of the invention are suitable over a wide range of wood species and are suitable for all woods currently in use in the panel making industry. 
     Resin optimization could be achieved by changing molecular weight (wt. Avg. MW), viscosity, and resin solids content. Catalysts, both internal and external, can be applied at various times, e.g., resin can be applied before dryer, but catalyst could be applied at blender and vice versa. 
     Suitable adhesives, as substitutes for, or in addition to, the phenol formaldehyde previously mentioned could include other thermosetting resins, so long as reduced ammonia and/or NO x  emissions are achieved. 
     When the lignocellulose particles are in the form of strands, the strands may be up to 12 inches in length and may be oriented to form oriented strandboard (OSB). Other products which may be manufactured according to the invention include high density fiberboard (HDF), medium density fiberboard (MDF), chipboard, laminated veneer lumber (LVL) and plywood. 
     Although we have described a “flaker” to process the logs into smaller pieces, the use of a “peeler” to form discrete layers or plys useful in manufacturing plywood or composite products, such as laminated veneer lumber (LVL) can be substituted for flaker  10  and are within the scope of the invention. 
     In all cases, the resin to be applied to the lignocellulose is applied before the lignocellulose is dried, such as before the drier, after, or in, the green or wet bin, between the green or wet bin and flaker or peeler, at the exit of the flaker or peeler, and even in the hot pond, or treatment vat for treating logs (either debarked or whole), with a preliminary application of resin. Though less effective than applying the resin to lignocellulose whose surface area has already been increased (e.g., by flaking or peeling), the invention is applicable to all phases of board preparation, provided that at least some resin is applied upstream of the drier, or when applied at more than one location is applied at least before the step of applying heat and pressure to a mass of particles and adhesive. 
     The invention has applicability to all known board manufacturing processes, including those using heated press platens, steam injection, catalyst injection, microwave or radio frequency (RF), heating and continuous and semi-batch pressing operations. 
     The invention is further explained by reference to the following examples. 
     EXAMPLE 1 
     Boards were made according to the specifications of Table 1 and tested for properties. 
     
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                   
                   
                   
                   
                 pre-treat resin 
                 % pre-treat 
                   
                 % 
                   
                 % 
               
               
                   
                   
                 Density 
                 pre-treated 
                 diluted 50:50 w/ 
                 RT solids 
                 Face 
                 Face 
                 Core 
                 Core 
               
               
                 Board 
                 Furnish 
                 pcf 
                 moisture 
                 water 
                 basis 
                 Resin 
                 RT 
                 Resin 
                 RT 
               
               
                   
               
               
                 Control 1 
                 Aspen 
                 43.0 
                 --- 
                 --- 
                 ---   
                 OS-745E 
                  3.5 
                 OS-408 
                 3.5 
               
               
                 23/32 
               
               
                 Test 1 - 23/32 
                 Aspen 
                 43.0 
                 dry - 11% 
                 OS-707 
                 20.0   
                 OS-745E 
                  3.5 
                 OS-408 
                 3.5 
               
               
                 Control 2 - 
                 Aspen 
                 38.0 
                 --- 
                 --- 
                 ---   
                 OS-745E 
                  4.0 
                 OS-408 
                 5.0 
               
               
                 23/32 
               
               
                 Test 2 - 23/32 
                 Aspen 
                 38.0 
                 dry - 11% 
                 OS-707 
                 15.0   
                 OS-745E 
                  4.0 
                 OS-408 
                 5.0 
               
               
                 Control 3 - 
                 Aspen 
                 38.0 
                 --- 
                 --- 
                 ---   
                 OS-745E 
                  4.0 
                 OS-406 
                 5.0 
               
               
                 23/32 
               
               
                 Test 3 - 23/32 
                 Aspen 
                 38.0 
                 dry - 11% 
                 OS-703A 
                 10.0   
                 OS-745E 
                  4 0 
                 OS-406 
                 5.0 
               
               
                 Test 4 - 23/32 
                 Aspen 
                 38.0 
                 dry - 11% 
                 OS-803 
                 10.0   
                 OS-745E 
                  4.0 
                 OS-406 
                 5.0 
               
               
                 Control 4 - 
                 Pine 
                 38.0 
                 green - 45% 
                 OS-703A 
                 15.0   
                 OS-745E 
                  4.0 
                 OS-406 
                 5.0 
               
               
                 23/32 
               
               
                 Test 5 - 23/32 
                 Pine 
                 38.0 
                 green - 45% 
                 OS-35D 
                 15.0   
                 OS-745E 
                  4.0 
                 OS-406 
                 5.0 
               
               
                 Test 6 - 23/32 
                 Pine 
                 38.0 
                 green - 45% 
                 OS-35D 
                 15.0   
                 OS-745SE 
                  4.0 
                 OS-406 
                 5.0 
               
               
                 Test 7 - 23/32 
                 Pine 
                 42.0 
                 green - 45% 
                 OS-703A 
                 20.0   
                 OS-745E 
                  4.0 
                 --- 
                 ---  
               
               
                 Test 8 - 7/16 
                 Pine 
                 42.0 
                 green - 45% 
                 OS-703A 
                 20.0   
                 --- 
                 ---  
                 --- 
                 ---  
               
               
                   
               
             
          
           
               
                   
                   
                 % 50S 
                 % 50S 
                   
                   
                   
                   
                   
                   
               
               
                   
                   
                 wax 
                 wax 
                 Press 
                 Total 
                 IB 
                 % 
                 % 
                 % 
               
               
                   
                 Board 
                 Face 
                 Core 
                 Temp 
                 Cycle 
                 psi 
                 WA 
                 TS 
                 CS 
               
               
                   
                   
               
               
                   
                 Control 1 
                  1.0 
                 1.0 
                 420° F. 
                 300 sec 
                 NT 
                 40.8  
                 14.6  
                 5.9 
               
               
                   
                 23/32 
               
               
                   
                 Test 1 - 23/32 
                 10  
                 10    
                 420° F. 
                 300 sec 
                 NT 
                 21.8  
                 1.7 
                 0.4 
               
               
                   
                 Control 2 - 
                 ---  
                 1.0 
                 420° F. 
                 300 sec 
                 31.1  
                 52.7  
                 15.7  
                 6.3 
               
               
                   
                 23/32 
               
               
                   
                 Test 2 - 23/32 
                 ---  
                 1.0 
                 420° F. 
                 300 sec 
                 55.0  
                 34.6  
                 5.0 
                 2.5 
               
               
                   
                 Control 3 - 
                 ---  
                 1.0 
                 420° F. 
                 300 sec 
                 44.6  
                 33.3  
                 10.6  
                 6.4 
               
               
                   
                 23/32 
               
               
                   
                 Test 3 - 23/32 
                 ---  
                 1.0 
                 420° F. 
                 300 sec 
                 102.3   
                 25.7  
                 5.6 
                 2.9 
               
               
                   
                 Test 4 - 23/32 
                 ---  
                 1.0 
                 420° F. 
                 300 sec 
                 64.8  
                 25.7  
                 5.6 
                 1.9 
               
               
                   
                 Control 4 - 
                 ---  
                 1.0 
                 420° F 
                 300 sec 
                 82.0  
                 55.9  
                 18.4  
                 10.3  
               
               
                   
                 23/32 
               
               
                   
                 Test 5 - 23/32 
                 ---  
                 1 0 
                 420° F. 
                 300 sec 
                 159.6   
                 46.5  
                 7.5 
                 5.8 
               
               
                   
                 Test 6 - 23/32 
                 ---  
                 1.0 
                 420° F. 
                 300 sec 
                 139.6   
                 53.4  
                 7.4 
                 6.7 
               
               
                   
                 Test 7 - 23/32 
                 ---  
                 --- 
                 420° F. 
                 360 sec 
                 124.5   
                 65.8  
                 13.1  
                 5.5 
               
               
                   
                 Test 8 - 7/16 
                 ---  
                 --- 
                 420° F. 
                 180 sec 
                 113.5   
                 60.1  
                 10.3  
                 6.2 
               
               
                   
                   
               
               
                   
                 Notes:  
               
               
                   
                 1) NT = Not tested  
               
               
                   
                 2) Dashed Lines (---) = No resin added  
               
               
                   
                 3) OS-803 in test #4 is the light colored face resin  
               
               
                   
                 4) Tests 1-4 all used aspen furnish that was already dried to 11% MC. This was then pre-treated and brought back up to −40% MC.  
               
               
                   
                 5) Tests 5-8 all used “fresh” green pine furnish at 45% MC that was pre-treated and brought to 50+% MC.  
               
               
                   
                 6) Note the center swell vs. edge swell in Test #6.  
               
               
                   
                 7) Test #7 was pre-treated with 50:50 703A:water and then only face layers were sprayed after drying - no core resin added.  
               
               
                   
                 8) Test #8 was a 7/16th board pre-treated and had no additional core or face resin added.  
               
               
                   
                 IB—Internal Bond. % WA = Water absorption. % TS = Thickness Swell. % CS = % Center Swell.  
               
             
          
         
       
     
     All parts or percentages used throughout this specification is by weight or weight percent unless otherwise indicated. 
     EXAMPLE 2 
     The following data demonstrate the effect of post addition of formaldehyde to a PF resin to which urea has been added on the ammonia emissions when the resulting adhesive was subjected to a temperature increase. 
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                  Effect of Post Additions of Formaldehyde on Ammonia Emissions of 
               
             
          
           
               
                   
                   
                   
                 (NH 4  Imp. Soln 
                   
                 NH 3  Total 
                   
               
               
                 Sample 
                 MR F/U 
                 Resin Wt, g 
                 Wt, g 
                 Conc. Ug/ml 
                 ug 
                 % X E-3 
               
               
                   
               
             
          
           
               
                 1 
                 0.5 
                 5.1196 
                 70.8327 
                 2.1 
                 148.75 
                 2.9 
               
               
                 1A 
                 0.5 
                 5.0560 
                 75.5086 
                 2.4 
                 181.22 
                 3.6 
               
               
                   
                   
                   
                   
                   
                 Avg 
                 3.2 
               
               
                 2 
                 0.75 
                 5.0961 
                 73.6180 
                 0.9 
                 66.26 
                 1.3 
               
               
                 2A 
                 0.75 
                 5.0739 
                 70.7759 
                 0.5 
                 35.39 
                 0.7 
               
               
                   
                   
                   
                   
                   
                 Avg 
                 1.0 
               
               
                 3 
                 0.85 
                 5.0591 
                 73.8229 
                 0.5 
                 36.91 
                 0.7 
               
               
                 3A 
                 0.85 
                 5.0621 
                 71.1275 
                 0.3 
                 21.34 
                 0.4 
               
               
                   
                   
                   
                   
                   
                 Avg 
                 0.6 
               
               
                 4 
                 1 
                 5.0481 
                 71.7689 
                 0.4 
                 28.71 
                 0.6 
               
               
                 4A 
                 1 
                 5.0922 
                 73.5366 
                 0.2 
                 14.71 
                 0.3 
               
               
                   
                   
                   
                   
                   
                 Avg 
                 0.4 
               
               
                 5 
                 0, Control 
                 5.0874 
                 72.1673 
                 17.5 
                 1262.93 
                 24.8 
               
               
                 5A 
                 0, Control 
                 5.0590 
                 76.6947 
                 12.3 
                 943.34 
                 18.6 
               
               
                   
                   
                   
                   
                   
                 Avg 
                 21.7 
               
               
                   
               
               
                 Procedure:  
               
               
                 1. PD-112 was heated to 50° C. and urea was added at 50° C.  
               
               
                 2. Formaldehyde was added to the resin at 35-37° C.  
               
               
                 3. After standing overnight at room temperature, the resin samples were adjusted to 35% solids.  
               
               
                 4. The 35% solids reins samples were tested for ammonia evolution by heating at 151° C. for 15 minutes. Each sample was tested in duplicate.  
               
             
          
         
       
     
     wherein MR is the “molar ratio” and the units of “%XE-3” are representative of the value, e.g., 2.9×10 −3  or 0.0029%. Sample number 5 is a control with no formaldehyde added to the PF resin to which urea has been added. 
     We have also evaluated the effect of delayed pressing on resin applied to lignocellulosic particles. Such a delay in pressing can occur due to mechanical breakdown of one or more components of the manufacturing process, e.g., a breakdown of the conveying system on the press. In such cases, the resin and particles may be in contact for an extended period, e.g., up to three days, as over a weekend when the breakdown occurred Friday and production did not recommence until the following Monday. The following examples simulate what may happen if pre-treatment resin was applied to furnish, then dried and the plant shut down for several days before that furnish was utilized. Combinations of a pretreat resin and traditional blender resin are also shown. 
     EXAMPLE 3 
     Board Study Parameters 
     1-23/32nd, 38 pcfOSB boardwas made per condition using re-humidifed aspen furnish (˜35% mc). 
     Press temperature was set at 420° F. 
     Press cycle of 300 seconds, button to button was used on all boards. 
     Cascophen EW-45LV wax emulsion was applied to all surface layers at 1.7% and all core layers at 1.0% based on solids. 
     Furnish Treatment 
     Boards 1 and 2 were pre-treated with an adhesive according to the invention only (12 and 8% respectively), then dried and allowed to sit for three days in a sealed container. These flakes were then treated with the specified amount of surface and core wax in the blender and then formed and pressed. 
     The remaining boards were subjected to the same as above, with the exception that after the three day waiting period they were treated in the blender with additional resin and wax, then formed and pressed into board. Table 3 summaries the treatment. 
     Resin Treatments 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 % Blender 
                 % Blender 
                 % Blender 
                 % Blender 
               
               
                 Board # 
                 % Pre-treat 
                 face resin 
                 core resin 
                 face wax 
                 core wax 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 12 
                 0 
                 0 
                 1.7 
                 1.0 
               
               
                 2 
                 8 
                 0 
                 0 
                 1.7 
                 1.0 
               
               
                 3 
                 12 
                 4 
                 4 
                 1.7 
                 1.0 
               
               
                 4 
                 8 
                 4 
                 4 
                 1.7 
                 1.0 
               
               
                 5 
                 6 
                 4 
                 4 
                 1.7 
                 1.0 
               
               
                 6 
                 4 
                 5 
                 5 
                 1.7 
                 1.0 
               
               
                 7 
                 6 
                 2 
                 2 
                 1.7 
                 1.0 
               
               
                 8 
                 4 
                 2 
                 2 
                 1.7 
                 1.0 
               
               
                   
               
               
                 Results:  
               
               
                 ***Note: Board 1 delaminated - we were unable to obtain test specimens for this board.  
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                  All Data 
               
             
          
           
               
                   
                 % 
                   
                 24 Hr. 
               
             
          
           
               
                   
                 % Pre-Treat 
                 Blender 
                   
                 Non-Oriented 
                 % 
                 % 
                 % 
               
             
          
           
               
                 Board 
                 PD-112 resin 
                 Resin 
                 IB 
                 MOR 
                 MOE 
                 EI 
                 MM 
                 WA 
                 TS 
                 CS 
               
               
                   
               
             
          
           
               
                 1 
                 12 
                 0 
                 *** 
                 *** 
                 *** 
                 *** 
                 *** 
                 *** 
                 *** 
                 *** 
               
               
                 2 
                 8 
                 0 
                  2.9 
                 1,076 
                 341,109 
                 125,975 
                 1,108 
                 36.9 
                 23.3  
                 18.1  
               
               
                 3 
                 12 
                 4 
                 42.9 
                 4,142 
                 596,782 
                 211,092 
                 4,141 
                 27.0 
                 5.9 
                 3.9 
               
               
                 4 
                 8 
                 4 
                 46.1 
                 3,385 
                 515,605 
                 192,899 
                 3,516 
                 27.9 
                 8.0 
                 4.6 
               
               
                 5 
                 6 
                 4 
                 40.1 
                 3,173 
                 543,842 
                 185,644 
                 3,101 
                 26.3 
                 6.6 
                 3.0 
               
               
                 6 
                 4 
                 4 
                 21.1 
                 3,909 
                 622,372 
                 215,654 
                 3,853 
                 32.3 
                 9.3 
                 5.1 
               
               
                 7 
                 6 
                 2 
                 32.6 
                 3,940 
                 558,222 
                 195,356 
                 3,914 
                 38.8 
                 13.1  
                 5.1 
               
               
                 8 
                 4 
                 2 
                 22.0 
                 2,688 
                 478,181 
                 178,429 
                 2,785 
                 72.2 
                 31.5  
                 28.2  
               
               
                   
               
               
                 *** = Delamination.  
               
             
          
         
       
     
     As is apparent from the foregoing, the multi-resin addition both prior to and subsequent to drying achieves acceptable quality even if the plant is subject to unanticipated shutdown for three days. 
     Although we have described our invention in relation to specific embodiments, it will be apparent that our invention is not limited and may be capable of modification by those skilled in the art without departing from the scope of the appended claims.