Technical Field

The present novel technology relates generally to chemistry and chemical engineering and, more particularly, improved resin binder systems and methods of manufacturing the same.

Background

Binders are materials used to hold disparate materials together. Resin binders are widely used in construction for to hold together partition walls, restroom dividers, countertops, and the like. Resin binder systems nay be sorted into two grades, HPL (High Pressure Laminate, static press) and CPL (Continuous High-Pressure Laminate) differing in the method of manufacturing. The current choice of binder system is a phenol-formaldehyde mixture in a 1.4 to 2.2 mole ratio of formaldehyde (F) to phenol (P). Both phenol and formaldehyde are chemicals where environmental concerns are going to require reduction in VOC by 50%. The European Union is asking for a significant reduction for phenol and the California Air Research Board (CARB) is requiring these laminate materials to meet CAR.B2 limits with less than 0.7 ppm Formaldehyde in

VOCs. Free phenol amounts in the current industry are 5-10% greater than the guidelines of the US EPA that are then mandated by each state with their own ppm requirement of unreacted phenol.

At the same time, industry demands are driving the development of resins for binder systems to meet increasingly stringent requirements for the reduction of carcinogenic and harmful chemicals. Thus, there is a need for an improved resin binder system that meets environmental standards as well as health and safety standards. The present novel technology addresses this need.

Detailed Description

For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended.

Binder Resin System and Laminate Materials

The present novel technology relates to a process for depolymerizing lignin from a variety of forestry and agricultural waste sources such as wood fibers or rice straw. The depolymerized lignin can be used as partial replacement for phenol, and the formaldehyde-free crosslinkers glyoxal and Polycup are used to reduce and/or eliminate the amount of formaldehyde used in an HPL and/or CPL (POLYCUP is a registered trademark of Solenis Technologies, L.P. LIMITED PARTNERSHIP DELAWARE 3 Beaver Valley Road, Suite 500 Wilmington DELAWARE 19803, registration no. 3427580). The components of the novel binder system include:

1. Eugenol Source - may be unpurified depolymerized lignin monomer where a major component is eugenol; may be made from rice straw, corn stover, and/or from wood fiber; and/or may be sourced as pure dihydroeugenol from petroleum.

2. Urea and/or ethylene urea which is used as additional monomer unit to decrease brittleness in the resin.

3. Glyoxal which is used as a crosslinker agent and as a formaldehyde substitute.

4. Glutaraldhyde which is used a crosslinking agent and as a formaldehyde substitute to reduced stiffness. Polycup 9700. Polycup is a commercial crosslinking resin. Polycup is a water soluble poly(amide epichlorohydrin), or PAE, resin. As sold, the secondary amine in the polyamide and the epichlorohydrin have reacted to form an azetidnium complex. Polycup comes in a variety of different grades, where Polycup 9700 has an amine enriched polymer with the lowest dichloropropanol (DCP) content and the highest pH. Thus, Polycup 9700 is compatible with the pH from thematerial in the depolymerized lignin reaction mixture and has attractive reaction conditions for the various cross linkers. Polycup 9700 is one of the Polycup resins that can be used for composite boards. Potassium hydroxide (KOH) is used to catalyze the reaction between the lignin eugenol and the dialdehyde (i.e. glyoxal and/or glutaraldehyde) as well as change the pH to manufacture recommended reaction conditions for Polycup. Phenol formaldehyde resin; specifically, a resole resin with a molecular weight of 300 to 650 g/mole that is approximately 60% resin by weight in a methanol solvent. Two different commercially available resins were investigated: a. Arclin Continuous Press Laminate PF Resin, having a lower pH of 7.5 with a lower MW of 450 g/mole, 57% solids, and a F:P mole ratio of 1.8 mole percent. b. Georgia Pacific PF Resin, having a higher pH of 8.5, which provides higher water tolerance, 60% solids and a F:P mole ratio of 1.72 mole percent. Kraft Paper. Kraft paper is a major component in the composite material. Typical specification of kraft paper is medium density at 9 to 10 apparent density. Apparent density is defined as the measure of the weight of the paper in lbs/3000 sq.ft, divided by thickness in mils (1/1000 of an inch). The grade of paper is 160 to 280 grams per square meter (GSM). The paper is made predominantly of southern pine and the porosity of the kraft paper is 10 to 20 seconds (porosity is measured by how long it takes lOOcc of air to travel though a 1-inch Gurley Porosity instrument). This paper is saturated with 30+2% by weight of resin, where the resin includes 6% by weight of volatiles before being placed in the press.

9. Waxes are used to improve water tolerance properties. Two waxes were used: (i) an experimental wax from Astro American Chemical Company designated Emulsion 002 Paraffin and Slack Wax and (ii) Michelman Inc. 66035 High Density Polyethylene Wax.

Resin Cook/Mix Process

The resin cook process for the eugenol-based materials involves the following steps:

1. The eugenol from either the degraded wood/rice or the surrogate eugenol is added to glutaraldehyde/glyoxal curing agent with a water as well as the MeOH solvent and KOH catalyst.

2. This mixture is heated to 82°C for 15 minutes - (pre-cook).

3. After the pre-cook, urea and Polycup are added to the mixture with additional KOH and heated to 82°C for 10 minutes (second cook). The second addition of KOH ensures more basic conditions which are desired for reaction with Polycup.

4. After the second cook, the new resin is added as an extender to the standard phenol formaldehyde laminating resin.

Resins were made consisting of between 50% to 75% of the traditional phenolformaldehyde with the remainder from the pre-cooked eugenol-based resin, although the resins could contain as little as 25% of the traditional phenol-formaldehyde with the remainder from the pre-cooked eugenol-based resin, or even 100% pre-cooked eugenol- based resin. In addition, resins samples with 100% of the traditional phenolformaldehyde resin currently used in the laminate industry were also produced in order to establish a baseline to which to compare the novel extended resins.

Laminate Manufacturing Process

The process for manufacturing B-staged kraft paper laminates is as follows:

1. Sheets of kraft paper were supplied as rolls of kraft of papers 5-foot wide and 6000 feet long. These were cut into more manageably sized sheets of 24-inch x 24-inch. These sheets were cut into (i) 4-inch by 4-inch squares or (ii) 4-inch by 8- inch strips that were eventually cut into 4-inch by 4-inch squares after B-Stage curing. Three-inch by eight-inch strips were also cut.

2. Using a generic paint brush, the resin was brushed onto the kraft paper making sure that (i) there was no resin rich puddled areas and (ii) there was complete coverage of the paper from edge to edge. The mass of the paper should approximately double after the resin is brushed on both sides of the paper (if the mass of the paper was 10 grams, the mass of the paper after impregnation was about 20 grams). The mass of the paper after impregnation was then measured.

3. The impregnated paper was dried in oven at 138°C. The samples were removed from the oven at one-minute intervals and weighed. When the weight of the impregnated paper was between 13 to 14 g for a wet paper that initially weighed 20 g, the A-stage part of the cure was complete. This typically took 6 minutes. The mass of the paper increased by 28 to 30% at the end of the A-stage; specifically, a 10-gram sheet of dry kraft paper will weight 18 to 20-grams wet, which will decrease to between 13 to 14-grams prior to B-stage cure. At this point approximately 0.8 g of the sheet remain as volatiles (mainly as water and methanol but it also includes excess formaldehyde, phenol, furfural, and some diols). Samples were visually inspected, where a dull sheen indicates that sufficient solvent has been removed during the oven drying process. Two-ply laminates were produced by stacking two sheets of the A-Stage Cured kraft paper together that were then sandwiched between two aluminum foil sheets coated with a mold release agent. The sample assembly was placed in hot press for final B-Stage cure. For the smaller 4-inch by 4-inch samples, a Carver Press with 6-inch by 6-inch heated platens was used with the following conditions: 12500 pounds-force at a temperature between 135 °C to 147°C for 5.5 to 8.5 minutes (except for one sample made in the “quick cycle” with a higher temperature of 175°C and pressed for 0.8 minute). For the 3-inch by 8-inch samples a PHI 70-ton hydraulic press with 12-inch by 12-inch heated platens was used with the following conditions: 50 to 60 tons of force at 144 to!50°C for 11 to!2 minutes. After curing in the press, the samples were removed from the press and immediately cooled between two cold aluminum press platens that act as heat sinks. This ensures the laminates cool down into a flat form. Test Procedure

For proof-of-concept testing, the following tests were performed:

1. Visual Inspection. The laminates manufactured resemble that of what is called a “Backer-Laminate” without the associated decor overlay on top. Visual inspect was performed for smudges, streaks, bubbles, blisters, even distribution of resin and foreign particles. Specific items for examination included: a. Gloss. Dull finish is expected with little to no shiny spots which indicate excess resin. b. Color. Resin should turn clear or light Carmel color. Dark brown spots indicate over-curing. c. Warp and “Squareness”. Laminates immediately come out of the press and are cooled between two cold aluminum press platens. The cured laminate is evaluated for dimensional quality. Specific criteria include: Does the laminate lay flat on a table surface? Uniform thickness as measured with a micrometer. Flatness measured by measuring the lowest point to the highest point of any concavity. Evaluation of corners of laminate to determine if they are broken.

2. Boiling Water Resistance (ISO 4586). Using a heat plate, water is brought to a rolling boil, where samples are then dropped into the water and kept below the surface for 30 minutes. The industry standard is 2 hours, where the Purdue testing thus far has only been for 30 minutes. The surface finish is then examined with ratings from no visible change to surface blistering to delamination of the layers. The laminate thickness is then measured, and the percent increase is the Thickness Swell. The laminate is then weighed, and the percentage increase is the Water

Absorption. Industry standard values are approximately 25% for Thickness Swell and 25% for Water Absorption.

3. Blister Test via Radiant Heat Strip Element Method. This test was performed to assess the effect of the radiant heat that is used to make a curved countertop surface. The test involved the use of 1600 watt two element radiant electric heater strips placed 10 cm (4-in) from the surface of the test specimen. The 7.5 cm by 20 cm (3-in by 8-in) samples were cut to 5 cm by 20 cm (2-in by 8-in) specimens and conditioned for 48 hours prior at immersion in an environment characterized by a temperature of 23°C and relative humidity of 50%. Calibration strips with thermochromic ink indicated when the temperature had reached 163°C (325°F), which indicates the beginning of the test. The surface is observed as a function of time up to the point of blister or 120 seconds if no blister is observed, where damage such as discoloration, blistering, charring, crazing and/or deformation is observed via mirror at bottom of apparatus. The time at which any damage occurs was observed and recorded.

Additional Tests

Samples were assessed as to whether they met ISO and NEMA standards (NEMA Standards Publication LD 3-2005: High-Pressure Decorative Laminates). These include but are not limited to the following:

1. Bandsaw and Drilling Test. Woodworking or metal blade may be used in the bandsaw. An electric drill with a drill bit of size 0.05 mm is used. Cut or drill laminate and observe for crack propagation and/or feathering of material. Bending Test. This is more of a test of the resin and performed by manufacture specification. No industry standard exists. Tests are conducted on a three-point bend apparatus via Instron or DMA. Internal Bond. A three-ply laminate is produced. Similar to internal bond test used with MDF composite boards, the sample is glued to two metal surfaces and pulled apart in an Instron. Values of the force at break are approximately 120 lb/in ² . This test is rarely conducted in industry, but for a new resin the test may be helpful. Post Forming. Post forming test for laminate requires a two-element heater and a radius forming apparatus. Place the laminate face down onto heating element apparatus. Then heat the laminate to the 163°C forming temperature. Allow forming apparatus to bend laminate into shape and record observations/damage. Failure is defined by the observation of fractures, blisters, and/or crazing. Ball Impact Resistance. Test for the core of the laminate to avoid damage from a falling 3.8 cm (1.5 in) diameter polished stainless-steel ball weighing 224 + 3 grams. The test specimen is 30.5 cm by 30.5 cm (12x12 in) laminate that is no less than 6 mm thick. The ball is dropped from ever increasing heights until visible damage such as fractures is observed, at which point the height is recorded. Dimensional Stability. This test measures the changes in laminate shape for a wide range of temperatures and relative humidity in a humidity chamber. The laminate size is at least 120 mm x 120 mm. Install pin-prick points for the caliper to measure in accordance with NEMA Testing. The midpoint is located between two adjacent corners and 10 mm from the edge and marked. Repeat for the other three sides of the sample. These marks will be used after the test if the sample warped or changes dimensions. Measure initial and final mark points. Two conditions are tested: (i) in an oven at 70°C for 24 hours and (ii) in a humidity chamber at 90% humidity at 40°C for seven days.

Examples

Experimental Test Set 1

Thirteen 10 cm by 10 cm (4”x4”) laminate samples were manufactured using (i) pure GP resin, (ii) pure GPL resin and (iii) GP resin extended with either rice eugenol at 25% by weight or surrogate rice eugenol at 25% by weight. All samples were formed at a pressure of 55600 Newtons (12,500 lbs force) in a Carver press. The detailed composition and manufacturing conditions are given in Table 1. After manufacture, all laminates were then visually inspected, dimensions measured, and subjected to the boiling water test for 30 minutes. The results are shown in Table 2.

All laminates were composed using 2 layers of kraft paper

GP: Georgia Pacific PF Resin; CPL: Arclin Continuous Press Laminate PF Resin; Syn 25%: 25% Sigma Aldrich Eugenol Resin Extender in 75% GP PF Resin; R-Eug 25%: 25% Rice Straw Derived Eugenol Resin Extender in 75% GP PF Resin; * Indicates Quick Cycle Short Press Time with Higher Temperature From the results reported in Table 2, it is observed that the optimal pressure and cure time conditions for the various resin systems are:

1. Pure GP resin: force exerted - 55600 N (12500 lbs); cure time- 7.7 minutes; cure temperature - 145°C

2. Mixture of CPL resin with 25 wt% of surrogate eugenol with crosslinkers from Sigma-Aldrich: force exerted - 55600 N (12500 lbs); cure time- 4.5 minutes; cure temperature - 147°C

3. Mixture of CPL resin with 25 wt% of rice eugenol with crosslinkers: force exerted - 55600 N (12500 lbs); cure time- 7.5 minutes; cure temperature - 147°C

The addition of 25 wt.% of the surrogate eugenol to the PF resin increased the thickness swell and moisture absorption. It is noted that the eugenol extended resins produced a lighter color laminate as that compared to the traditional PF resin allow, which is potentially beneficial when used with a lighter-colored upper decor layer. It is promising that no samples exhibited any signs of delamination after the water boil test. It was also noted that the pure Arclin phenol-formaldehyde resin performed better than the pure GP resin, where the GP resin was glossy and tacky most likely because it is a higher pH, resole resin. A different set of cure conditions and/or combination of resin chemistry, pressure, and volatiles amount in resin at B-Stage should improve the performance of the GP resin. Experimental Test Set 2

The next samples were 7.5 cm by 20 cm (3 in by 8 in), where the composition is shown in Table 3 These specimens were made to test the Arclin CPL resin as a baseline against the CPL resin extended (i) with depolymerized rice lignin with crosslinkers and (ii) depolymerized wood lignin with crosslinkers. Samples were made in the larger PHI 12xl2-inch press. All samples used the same press conditions of 490300 N (50 tons force) at 140°C for 8.5 minutes to ensure complete cure. The amount of depolymerized rice lignin wood used to extend the CPL resin were increased to 50 wt.%.

All specimens exhibit acceptable visual gloss and no warp. 2.5 cm by 2.5 cm (Ixl-in) squares were cut for in house water absorption and thickness swell tests. The results of water adsorption and thickness swell for the CPL resins are shown in Table 4, where employing 30 to 50 wt. % eugenol to extend the CPL resin system increased water absorption, although it is possible that the use of various additives (e.g. fatty acids, diethylene glycol, or glycol ethers) can reduce water absorption. Thickness swell values are still within specifications. Once again, the samples showed no signs of delamination.

The remainder of the samples tested for both water absorption and blister tests on these samples. Water boil test was conducted for 2 hours compared to the in-house method of 30 minutes. The results are shown in Table 5. The key findings in Table 5 are that the addition of the depolymerized rice/wood lignin resin has a minimal effect on the thickness swell and moisture adsorption. In addition, these system with the added rice/wood degraded lignin did not blister after 80 mins in boiling water.

Experimental Test Set 3

The next set of 7.5 cm by 20 cm (3 in x 8 in) laminate specimens were manufactured in the press to ensure more consistent and even pressure with approximately 588400 N (60-tons force) at 144°C for 11 minutes. The composition is given in Table 6. Two samples were 70/30 mixtures of CPL resin with rice eugenol resin. The third sample was a 70/30 mixture of CPL resin with wood eugenol resin.

Both samples formed a solid laminate, but some defects were observed. The depolymerized wood lignin extended sample had a minor warp, but had the best surface finish of the two. The depolymerized rice lignin laminates were flat, but exhibited a splotchy color across the laminate indicating that the press conditions require optimization.

2.5 by 20 cm (1 x 8 in) strips were cut for water boiling tests, where the results are shown in Table 7. The remaining 5x20 cm (2x8-in) samples were used in the radiant heat blister test, performed for 120 seconds on all samples, where all samples passed without any blister. The samples began to char but not burn, which is a preliminary indication of the fire resistance of the laminates. Eugenol is considered a fire retardant; therefore, it is possible that the addition of depolymerized rice lignin (where eugenol is a component) to the phenol-formaldehyde laminating resin aids in fire resistance, where laminates can be sold at a higher margin if they have improved fire resistance capabilities. While our samples passed the NEMA LD3 testing standards, these are part of older US Standards. Samples will have to pass more prevalent ISO Standards as those are what the industry is transitioning to. Experimental Set 4

Four aspects were tested in this set: (1) the interaction of 70/30 mixture of CPL resin with depolymerized lignin resin with what is called a decor paper, (2) the compatibility of the 70/30 mixture of PF resin and the depolymerized lignin cure package with different types of kraft paper, (3) adding wax to improve water absorption and thickness swell, (4) an attempt to manufacture the laminates similar to industry by using a stacked laminate layup. The two different types of paper impregnated with resin are described below: a. Two 30 cm by 30 cm (12”xl2”) test specimens were produced using a traditional kraft paper. The mass ratio of glyoxal to the depolymerized rice lignin iis shown in Table 6 below. The manufacturing protocol for these specimens was: (i) B-Stage cure at 138°C followed by (ii) 588400 N (60 tons pressure) at 140°C for 24 minutes. b. Two 15 cm by 20 cm (6”x8”) test specimens were produced using paper made of 50% Bagasse, which is the pulp residue after the extraction of sugar cane juice. Bagasse Sample 2 had more depolymerized rice lignin as shown in Table 6, thereby decreasing glyoxal to rice lignin ratio which decreases the extent of crosslinking. The manufacturing history for Sample 1 was: (i) a B-stage cure at 138°C (ii) 588400 N (60 tons pressure) at 140°C for 24 minutes. The manufacturing history for Sample 2 was: (i) a B-stage cure at 132°C followed by (ii) curing in a hot press with 60 tons of pressure at 140°C for 24 minutes. The reason for the lower B-stage cure for Sample 2 was an observation made with Sample 1 is that the Bagasse specimens were curing faster than normal, where it was later realized that this is because the pH of the Bagasse material is higher which results in a faster cure.

Due to the higher water adsorption and thickness swell results seen in previous experiments, wax was added. Waxes were added to the resin mixture before brushing the resin onto the paper for the B-Stage cure. Waxes tested include (i) an experimental wax from Astro American Chemical Co. designated Emulsion 002 Paraffin and Slack Wax and (ii) Michelman Inc. 66035 High Density Polyethylene Wax. DOSS (dioctyl sulfosuccinate) was added into the resin as well to aid with penetration into the kraft paper. Michelman Wax was found to mix better with our resin mixture. The resin composition of the three laminates is given in Table 8.

The core of each laminate sample consisted of two resin impregnated kraft paper sheets. Above these sheets, a decor paper was placed. The decor print paper used was a typical decor print paper with wood print. Above the decor paper, a clear overlay sheet made of melamine formaldehyde high flow resin mixed with aluminum oxide particles (size 220F) was placed as the top layer of each sample. This overlay is a fast cure overlay and is used in the flooring industry. The primary task of an overlay is as a protective wear layer with a secondary objective of stain resistance. The laminates were manufactured using the standard industry method of stacking multiple laminates within the press. On the top and bottom of each laminate with overlay sheet was a thin sheet of aluminum foil coated with 7991 polyethylene with siloxane mold release. Press pads were used to separate the laminates and the aluminum foil release layer, where the press pads are pieces of plain kraft paper wrapped in aluminum foil. The detailed arrangement of the stack of materials in the press is given in Table 9. The laminate assembly detailed in Table 9 was placed in a PHI press under 588400 N (60 tons) (corresponding to 833 psi for the 930 cm ² (144 in ² ) laminate assembly) for 24 mins at 140°C. The manufacturing process did not function fully as intended, where the second hood kraft paper laminate that was sandwiched in the middle of the layup did not form a laminate. Specifically, the hood kraft paper laminate delaminated upon removal from the layup, which is likely due to heat transfer limitation to the center of the layup where this hood kraft paper laminate was located. Notwithstanding the difficulties with the centermost laminate material, we believe the thermal history of the outer laminates was able to cure the resin.

The laminates were tested for water absorption and thickness swell, where the results are shown in Table 10. The added wax added substantially in the reduction of water absorption as compared to data in the previous sets of experiments. The addition of wax had a minimal effect on thickness swell. The values of 15% water adsorption and 15% thickness swell are well in line with industry standards. In the boiling water test, only Sample 1 of the Bagasse laminate delaminated, which we ascribe to over-curing during the B-Stage process that was indicated by the color of the B-Stage kraft paper after the B-Stage cure process. Specifically, over-cured samples look lighter in color and have a golden sheen whereas properly B-Staged kraft paper still has a darker brown hue.

Experimental Set 5

Repeats of the previous hood kraft paper laminate with wax were conducted to achieve better Water Absorption and Thickness Swell. It was discovered that Michelman’s wax mixed better with the resin in the previous Experimental Set 4 and therefore, more was added. The resin composition is shown in Table 11. The B-stage cure temperature for these laminates was 132°C. Press conditions were 588400 N (60 tons) at 124°C for 24 minutes. Water absorption and thickness swell was measured as reported in Table 12. After manufacturing, the laminates exhibited warp due to the overlay being over-cured, which is probably due to the fact that this overlay is a highly catalyzed, fast cure overlay and therefore not well-suited for use in a static press. However, the added wax amounts did improve water absorption and thickness swell, yielding results better than the industry standard shown in Table 5. Experimental Set 6

An important aspect of manufacturing laminates is the temperature at which samples are cured during the B-Stage cure process. All hood kraft laminate samples until Experiment Set 6 had used kraft paper B-Stage cured at 138°C. For this new set of experiments, the kraft paper cure temperature was increased to 142°C for Sample 3 and decreased to 132°C for Sample 4. The composition of the resin system is given in Table 13. The manufacturing conditions in the press were 60 tons of pressure at 126°C for 24 minutes. The resin composition is as show in Table 11, where the wax was Michelman. A new overlay was used to reduce the amount of warping. It has no aluminum oxide, less catalyst and a sugar plasticizer in the resin. The laminate were cured in the PHI pressure with a pressure of 60 tons at 126 °C for 24 mins.

Water absorption and thickness swell were measured and are reported in Table

14. When the B-Stage cure was 142°C, a large bubble sandwiched between the kraft paper plies appeared so that a laminate was not formed; specifically, the higher temperature B-Stage cure resulted in the resin to become over-cured in the B-Stage process which resulted in less flow and adhesion during the final pressing process. When the B-Stage cure was 132°C, the resulting laminate had a blister, indicating excess volatiles in the resin that failed to escape in the B-Stage cure. Thus, temperatures near 138°C are optimal for the CPL/Depolymerized rice lignin resin mixture. The water absorption and thickness swell for the Sample 4 which was not delaminated are excellent. Finally, the new overlay significantly reduced the amount of warping, which support the hypothesis that the over-cure of the overlay was the source of the warping of the cured panels in Experiment 5.

The investigation detailed above indicates the potential of using depolymerized lignin from rice or corn stover or wood as an extender to reduce the amount of the phenol and formaldehyde in binder resin used in traditional kraft paper laminates. Two tests for laminating resins are water absorption and thickness swell, where the depolymerized lignin were within industry standards when wax was included in the formulation. The majority of the studies replaced 30 % by weight of the phenolformaldehyde resin with depolymerized lignin resin, where there is evidence (from Experimental Set 2) that the depolymerized lignin extended resins may be compatible with PF resins up to a 50/50 mixture. With proper formulation it may be possible to improve the water absorption, thereby potentially reducing even further the amount of phenol and formaldehyde in kraft paper laminate composites. The next step is to produce larger, 5 -ply test specimens so that the specimens can be tested using the full suite of NEMA and ISO Standards in order to prove the commercial viability of this system.

Alternate Embodiment

A binder system (the glue that holds the composite together) for wood-based composite board products has been developed that uses depolymerized lignin as the major component in the binder system. One attractive feature of this new binder system is that it does not employ formaldehyde, a known carcinogen, where there is significant regulatory pressure to remove formaldehyde from all composite products used in the home. The depolymerized lignin was used just as it comes out of the bioreactor, where both the clean cellulose and majority of the methanol solvent were removed which are easy separation process. However, the remaining reaction mass that contains lignin monomers, residual solvent and sugars was used as received, without any additional purification. Preparation of Depolymerized Lignin Feedstock

Depolymerized lignin feedstock was provided. The lignin monomer feedstock was prepared by catalytic depolymerization of poplar wood chips. Specifically, 100 to 200 g of 70 mesh dried wood biomass was reacted under batch conditions with 10% by weight catalyst in 1-2 L methanol solvent under hydrogen pressure (30-50 bar) at 200- 225 °C for several hours. Solid filtration followed by solvent concentration under rotary evaporation provided the lignin methoxyphenols feedstock used in resin preparations.

The depolymerized lignin resin was used as received. Specifically, the cellulosic fraction of the wood chips had been removed (except for a limited number of tests) and greater than 95% of the methanol solvent was also removed. However, the remaining reaction mixture was not purified any further. This mixture contains propyl methoxyphenols (see structures above) as the main components, but also includes other minor reaction products including xylose as well as a residual methanol solvent.

One interesting aspect of the binder technology described herein is that it works with the unpurified reaction mixture after the relatively easy removal of the lignin free cellulose solid byproduct and most of the methanol solvent, thereby avoiding the need for costly separation processes. The ability to avoid costly separation operations significantly affects the overall economics of the lignin monomer binder system.

Production of Binder Resin

Using the depolymerized lignin mixture as the main component in the binder system, a formulated binder system for composite board use was produced. The components in the formulation included:

1. The unpurified depolymerized lignin monomer mixture

2. Polycup 9700 curing agent. Polycup is a commercial crosslinking resin sold by Solenis and originally developed by Ashland Chemical. Polycup is a water soluable polyamide-epichlorohydrin (PAE) resin. As sold, the secondary amine in the polyamide and the epichlorohydrin have reacted to form a azetidnium complex as shown below. Polycup comes in a variety of different grades, where Polycup 9700 has an amine enriched polymer with the lowest DCP content and high pH so that it is compatible with both the extractables in the lignin reaction mixture and the various cross linkers. Fiber. Different types of wood fiber are used for different applications, herein hard-wood and soft-wood fiber from mixed elm, oak, ash, hickory, maple, chestnut, birch, and poplar, and low amount of soft wood such as spruce, pine and hemlock were used. These woods are typically used in the production of medium density fiber (MDF) boards. Characteristics of the fiber product are: soft, fibrillated fluffy texture with a refined, short fibers with 10% moisture. Glyoxal. Glyoxal is a small molecule organic compound that is used in the wood/paper industries to crosslink cellulosic material in wood/paper products. Wax. Two different types of paraffin based waxes were used. Chlorez 700 is a powdered solid paraffin based wax that is 70% chlorinated, that imparts both water repellency as well as some flame retardancy. During manufacture Chlorez will off-gas HCI which might play a role in the reaction of the Polycup with the lignin monomer. Also used was ULTRALUBE E345. ULTRALUBE is a registered trademark of Keim-Additec GmbH, a Federal Republic of Germany corporation, Hugo-Wagner-Strasse D-55481, Kirchberg, Germany, reg. No. 2389258.

ULTRALUBE E345 is a paraffin wax used for water repellency that is an emulsion with 45% solids content. The molecular weight of Chlorez is approximately

350g/mole; the molecular weight of ULTRALUBE is between 280 to 420 g/mole.

6. Styrene-Maleic Anhydride (SMA). SMA is a random copolymer produced from a monomer mixture of styrene and maleic anhydride. SMA is traditionally used in the wood/paper industries as a dispersant for the paraffinic wax and to aid in better wetting of the wood fibers. The molecular weight is 3500 g/mole.

The components above make the main mixture used in the binder resin formulation; however, other types of curing agents, additives, and the like have also been investigated. Other compounds that have been studied include: 7. Azideine is a potential alternative crosslinker to the Polycup.

8. Cyanuric is a potential alternative crosslinker to the Polycup.

9. Carbodimide is a potential alternative crosslinker to the Polycup.

10. An aminosilane, specifically gamma-aminopropyltriethoxysilane, which is a potential alternative crosslinker to the Polycup.

The 10 components above were investigated to determine which components could provide an alternative to the current formaldehyde based thermoset resins. In addition, a traditional phenol-formaldehyde resin system was investigated, which will serve as the target material with which to compare the properties of alternative binder systems.

Composite Manufacturing Process

Small test samples of fiber filled composite were produced using the following procedure:

1. Select the composition for the composite sample

2. Preheat both platens on press to 192°C.

3. Measure the fiber amount in grams and place into a cup or beaker.

4. Add in processes cellulose material if desired

5. If the powdered solid wax (i.e. Chlorez 700) is used, add the wax to the cellulose fibers and mix with a spatula by hand.

6. Measure the specified amount of water, methanol, and lignin monomer, and glyoxal. Water should be 25 weight percent of this mixture and methanol should be 15 weight percent of this mixture. Mix with spatula by hand. If the E-345 wax is used, mix with water along with SMA dispersant. Premix the E- 345 wax with water to form an emulsion at a 1:3 ratio of wax to water. Then add the SMA dispersant and mix with a spatula by hand. Spread the lignin monomer/glyoxal mixture from a pipette over the fibers and mix the resulting wet fiber mixture well with spatula by hand. Spread the wax and SMA mixture from a pipette over the fibers and mix the resulting wet fiber mixture well with spatula by hand. A cardboard template that is 2mm thick with a cutout that is approximately 3 in x 2in is covered with aluminum foil. A release agent is applied between the foil and an aluminum plate on the hot press to prevent any curing of the template to the plates of the hot press. The mixture of fiber, crosslinker, liginin, and wax is placed into a mound in the center of the cardboard template, where the template is already at the cure temperature (which for these experiments is 192°C). A piece of aluminum foil is placed over the “mound” of fibers, the release agent is wiped on the top surface of the aluminum foil to prevent bonding with the platens of the hot press and the aluminum foil on the template. Close the press and apply 1400 pounds force. Cure mixture at 192°C for 6 minutes. Note: the force from the press is used to make sure that fiber-binder mass is consolidated, but because the template is only made from cardboard there will be no significant internal pressure curing the cure cycle. This cure cycle mimics the thermal/pressure history in a continuous belt press used in a modern composite board manufacturing facility. 14. Open press, remove mold with sample from press and carefully remove composite sample from template. The cured specimen does not stick to the aluminum foil and the release agent prevents the various aluminum parts for sticking together.

15. Trim edges of the cured composite sample with scissors for uniformity. It was important to remove the edges, especially for moisture adsorption tests, because the pressure at the edges is less than at the center and thus the fiber compaction is different.

Testing Procedure for Composite Samples

Various tests were performed to evaluate the basic cure chemistry of the various compositions. These tests included:

1. Brittle Failure. The samples produced after curing in the press were tested by hand to screen for gross mechanical behavior. Specifically, the samples were bent by hand with modest force. If the samples snapped during this hand test, they were classified as brittle. Compositions that exhibited extreme brittle behavior were eliminated from the next test matrix.

2. Extraction. Material that was not immobilized by the curing reaction was determined via water extraction using a modified version of TAPPI (Technical Association of the Pulp and Paper Industry) method T204 om88 based upon the ASTM T204: Solvent Extractives of Wood and Pulp) procedure (see Appendix B). The samples are placed onto cups and soaked in approximately 500 mL of water for 24-hours for the water adsorption test. Once the 72-hour period is complete, the samples are removed from the cups and the color of the remaining water is observed. Yellow water indicates “leaching” of unreacted lignin monomer material. This indicates a poor crosslinking. The clearer the water is; the more lignin material was crosslinked. A qualitative ranking scale was employed: Poor (or 3) samples exhibited a strong yellow color in the liquid in the container; Moderate (or 2) samples showed a yellow tinted liquid; Good (or 1) samples showed little to no yellow tint in the extraction liquid. The best samples remained visually clear, indicating no leaching of unreacted material by water, which were also rated Good (or 1). Water Absorption. The industry standard test requires that boards be subjected to a 24-hour period of water submersion and then dried at room humidity and temperature. The ASTM D1O37-99: Standard Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials (Sections 100-103 and Sections 105-107) was employed. The thickness swell and water mass absorption is observed in 24-hour intervals after the initial 24-hour submersion period. Samples that perform very well absorb the least amount of water and return to original thickness and mass after a 72-hour drying period. Note: the water adsorption test is not really concerned with how much water is absorbed, but rather how fast the water de-absorbs - this is a critical application feature, where if composite flooring or furniture get wet it returns to its original state upon drying, that has insurance implications. Pull Test. The mechanical properties of selected specimens were determined using the ASTM D952: Standard Test Method for Bond or Cohesive Strength of Sheet Plastics and Electrical Insulating Materials. Specifically, the composite sample based were first bonded to pull rods using 160 grams per square meter of Huntsman Araldite 2-Part epoxy adhesive, and then the pull rod with composite samples was subjected axial deformation in an Instron tensile testing instrument with 500 psi load cell. Both the initial modulus and tensile failure were recorded. Only measurements that resulted in cohesive failure in the center of the composite material were recorded. Typical examples of composite board failure are shown in the attached figure, where it is clear that the failure is cohesive.

There are a number of tests that are used by the composite board industry including: (a) water adsorption, i.e. 3 above, (b) the strength from a pull test, i.e. 4 above, (c) screw holding test, (d) lap shear, (e) rupture test (MOR) and f) damage and stability - all of which are defined in ASTM D1O37-99. Tests c through f are all related to (a) and (b), where the simple hand screening test in (a) serves as a surrogate for (b) that can eliminate compositions that are too brittle. Thus, after initial screening using the brittle test, extraction and water adsorption, the more involved pull test was performed on candidate specimens that looked the most promising.

Effect of Composition on Material Properties

The properties of the new lignin binder system were compared to (i) the traditional urea-formaldehdye system and (ii) for a polymeric methylene di-phenyl di- isocynante (PMDI) used in the wood composite board industry.

1. These For the urea-formaldehyde system, the composition (all by weight percent) used in industry for this system is: 77 to 84% fiber, 7% water, 8 to 15% of ureaformaldehyde (in the ratio of 1.2% formaldehyde:urea) and 0.5 to 1.5% wax. We produced test panels for the urea-formaldehdye systems using: exact composition numbers. The physical properties for panels with the urea-formaldehdye system are: water adsorption = 8 to 20% increase in thickness, 10% increase in weight, modulus = 0.10 kpsi and strength = 35 psi.

2. For the PMDI binder system the composition (all by weight percent) used in industry for this system is: 61% fiber, 15% polyethylene fiber, 12% Acurdor (BASF water-based acrylic resin), 12% Wollastonite calcium. The polyethylene fibers have been added to PMDI in order to make a wood-plastic composite which is a very high end system, where the polyethylene fibers give both added strength as well as improved moisture absorption characteristics. We produced test panels for the PMDI system using the exact above composition. The physical properties for the panels are water adsorption = 7.3% increase in thickness and 21% increase in weight, initial modulus = 15.5 kpsi and strength = 41.2 psi.

These properties provide a target that the new lignin based system needs to meet or exceed. Based upon these numbers we have described a qualitative metric for performance of new resin systems:

1. Brittle failure: 1, Good - Samples remained stiff to the hand and had little give when a small force is applied; 2, Moderate- These samples bent or cracked under a small bending force applied by hand; 3, Poor- These samples would immediately crack with a small bending force OR did not form a cohesive panel after leaving the press.

2. Extraction: 1, Good- Clear solution; 2, Moderate- Pale yellow solution; 3, Poor - Heavily yellow solution-poorer cross-linking 3. Water Absorption: The thickness swell here is measured 48-hours after the 24- hour soak period. Poor - Thickness swell more than 10%; Moderate - Thickness Swell between 7% and 10%, Good - Thickness Swell less than 7%.

4. Pull Test: Poor - modulus < 15 KPSI units and strength less than 25 psia;

Moderate - modulus between 15 to 25 kpsi and strength modulus between 25 to 70 psia; Good - modulus greater than 25 kpsi and strength greater than psia.

The specification of poor/OK/good is consistent with the assessment of experts in composite boards.

Initial Screening of Crosslinking Chemistry for Lignin Monomer Binder

Screening tests on the effects of composition of the new binder system on the physical properties of the composite test specimens is shown in Table 1. The objective of this initial study is to determine the components of the cure package needed to polymerize the lignin monomer.

The deligninzation reaction produces a reaction mixture that includes (i) cellulose chips from the original wood used to produce the lignin monomer and (ii) a mixture of the depolymerized lignin with some hemi-cellulose, sugars and residual methanol solvent. The ‘process cellulose chips’ in Tables 1 through 4 is the cellulose from the deligninization reaction.

Examining the initial screening data in Table 1, one sees that when Polycup is used as the main component in the cure reaction (samples B, F, G and M) that samples with acceptable properties are produced, although if only a small amount of Polycup is used (samples A and B) the extraction test indicates that not all of the material is fully incorporated in the thermoset. Examining samples F and G, one sees that incorporating the process cellulose chips did not adversely affect the physical properties, at least as measured in these screening tests. The only other formulation that produced acceptable properties was the cure package that used azideine. As a result of these tests, cure system involving polyamine, cyanuric, carbodimide and gamma-aminopropyltriethoxysilane were not considered further, although it is possible with additional work the amounts and cure cycle could be modified to make these systems work.

While the novel technology has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the novel technology are desired to be protected.