WO2023147249A1

WO2023147249A1 - Method for making composite board from methanol exploded depolymerized lignin and composite board made of the same

Info

Publication number: WO2023147249A1
Application number: PCT/US2023/060903
Authority: WO
Inventors: James CARUTHERS
Original assignee: Purdue Research Foundation
Priority date: 2022-01-31
Filing date: 2023-01-19
Publication date: 2023-08-03

Abstract

A method of preparing a composite board, including soaking a first quantity of biomass fibers in methanol to yield a second quantity of methanol infused biomass fibers, placing the second quantity of methanol infused biomass fibers into a first pressure vessel to increase pressure therein, rapidly reducing pressure within the pressure vessel to yield a third quantity of methanol exploded biomass fibers, and placing the third quantity of methanol exploded biomass fibers into a second pressure vessel. The method further includes introducing methanol, hydrogen gas, nitrogen gas, and acid into the second pressure vessel to define a first admixture, heating the first admixture under increased pressure to yield a quantity of unpurified depolymerized lignin, mixing the quantity of unpurified depolymerized lignin with predetermined quantities of fiber, curing agent, paraffin wax, glyoxal, and dispersant to define a second admixture, and bonding the second admixture with cardboard to yield a formaldehydefree composite board.

Description

METHOD FOR MAKING COMPOSITE BOARD FROM METHANOL EXPLODED DEPOLYMERIZED LIGNIN AND COMPOSITE BOARD MADE OF THE SAME

Cross-Reference to Related Applications

This patent application claims priority to co-pending U.S. Provisional Patent Application Serial No. 63/304718, filed on 31 January 2022.

Technical Field

The present novel technology relates generally to chemical engineering and, more particularly, improved methods of depolymerizing lignin.

Background

This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.

Lignin is the most abundant natural aromatic polymer. Lignin has a high storage capacity for phenolic compounds, and as such is a potential source for polymers and biomaterials. However, access to those polymers and biomaterials is difficult, as lignin is both complex and not very reactive. One method of accessing the locked-in polymers and biomaterials is through depolymerization of the lignin. However, commonly used methods of depolymerization of lignin typically involve hazardous and potentially deadly chemicals. Thus, there is a need for a lignin/cellulosic material depolymerization process that does not requires the use or presence of hazardous chemicals. The present novel technology addresses this need.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. i is a process flowsheet for production of clean depolymerized lignin and clean cellulose from biomass.

FIG. 2 schematically illustrates the molecular structure of DHE and DMPP.

FIG. 3 schematically illustrates the molecular structure of a binding agent.

FIG. 4 schematically illustrates the molecular structure of a glyoxal.

FIG. 5 schematically illustrates the molecular structure of a paraffin wax.

FIG. 6 schematically illustrates the molecular structure of a an SMA resin.

FIG. 7 graphically illustrates the relationship between time after soaking and percent thickness change for various composite board compositions.

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.

The present novel technology relates to a process for the explosive separation of lignin from cellulosic material using an organic solvent, such as methanol; the depolymerization of the so-separated lignin; and the extraction of clean lignin from the depolymerization yield.

A process has been developed for the production of depolymerized lignin from various sources of biomass. The process flowsheet is given in Fig. 1. The process can produce both (i) clean cellulose that has the lignin removed and (ii) clean, depolymerized lignin where the sugars and hemicellulose components have been removed. Novel features of the technology include: i. Vapor explosion of biomass. Steam explosion ofbiomass fibers is well known. However, the use of a solvent other than water is novel. The use of an organic solvent such as methanol provides a number of significant advantages. First, water does not have to be removed from the product with an associated energy cost for the subsequent depolymerization reaction step which uses an organic solvent. Further, the boiling point of the organic solvent can be significantly lower than that of water, such that the super-heated conditions required for vapor explosion can be achieved at lower temperature and hence at a lower energy cost. Finally, there is a higher uptake of specific organic solvents, in this example methanol, by biomass so that the subsequent vapor explosion is more effective.

2. Catalyst free lignin depolymerization. The current technology for depolymerization of biomass employs a catalyst, typically supported nickel. The instant novel technology performs the reaction at supercritical conditions under a hydrogen atmosphere without the need for a metal catalyst, thus, eliminating the cost of the catalyst as well as the need (with associated cost) to remove the catalyst from the final product.

3. Clean lignin production. After the depolymerization reaction, the cellulose fibers are removed. The depolymerized lignin product also contains sugars and hemicellulose which may not be desirable in some uses of the depolymerized lignin. While liquid-liquid extraction is well-known in the chemical industry, no process has been developed where saline is used to extract the hemi-cellulose and sugars from a depolymerized lignin mixture.

The process technology described herein uses biomass feedstock (in this example wood chips and rice straw) as the lignin source. However, the instant novel technology also works with a variety of agricultural and forestry sources of biomass, including wheat straw, corn stover, sugar cane bagasse, combinations thereof, and the like. The only real requirement is that the biomass have a significant amount of lignin.

A description of the various components of the technology follows below.

Vapor Explosion.

Referring to the Vapor Explosion sub-box in Fig. 1, the process may be envisioned as involving three units:

1. A tank where the fibers are soaked in the solvent, where this may be at room temperature (above room temperature) or the process can be accelerated by soaking at an elevated temperature that is below the boiling temperature of the solvent.

2. A high-pressure tank where additional solvent is injected when the tank has been loaded with the soaked fibers containing solvent. The pressure in the tank is raised such that the fiber-solvent mixture remains in the liquid phase as the mixture is super-heated. The heating process can be efficiently accelerated if the additional solvent is heated prior to injection into the high-pressure tank. Once the fiber-solvent mixture is at a temperature well above the boiling point of the solvent at atmospheric pressure (and thus at elevated pressure), the pressure in the tank is quickly reduced and the solvent rapidly boils. The solvent that has swelled the fibers also boils thereby exploding the fibers.

3. The escaping vapor is captured in a knockout tank, where it is condensed back into a liquid at atmospheric pressure and recycled back into the soaking tank.

This process is similar to that used for steam explosion of fibers, but has the advantages that (i) water is not present in any appreciable quantity and thus does not need to be removed for downstream processing, (ii) some organic solvents like methanol are more effective in swelling natural fibers and (iii) the boiling point of many organic solvents is lower than that of water so that similar pressures that drive the explosion process can be achieved at lower temperatures with associated lower energy costs. Lignin Depolymerization.

The vapor-exploded fibers with solvent are then put into the high-pressure reactor as shown in the Lignin Depolymerization sub-box in Fig. 1. The high-pressure reactor may be the same unit as the vapor explosion unit described above, where the decision to use one or two reactors may depend upon such factors as (i) increased cost of two reactors, (ii) the time and energy required to heat the depolymerization reactor from sub-critical conditions, needed for vapor explosion, to the super-critical conditions needed for lignin depolymerization, or simply (hi) throughput demand. Additional ingredients such as catalysts, hydrogen, nitrogen, and acid maybe added to the reactor, which is then heated to temperatures that are super-critical and thus generate high pressures. The super-critical conditions are desirable, because high temperatures increase the rate of the lignin depolymerization reaction.

Methanol is the solvent used in the current example, although any convenient organic solvent maybe selected. Methanol is a good choice for the solvent because it (i) readily swells the fibers, (ii) is low boiling compared to other alcohols but is still a liquid with a relatively low vapor pressure, (hi) is readily available, and (iv) is one of the components in the composite board resin system that has been developed using the depolymerized lignin, thereby alleviating the need to fully remove the methanol. However, any other organic solvent may also be useful, where the associated process would be similar with different temperatures and pressures required for both the vaporexplosion and lignin depolymerization reaction as tailored to the boiling point of the selected organic solvent.

The depolymerization reaction is most commonly accomplished using a metal catalyst, typically supported nickel. However, lignin depolymerization can also be achieved at super-critical temperatures using just high-pressure hydrogen absent metal catalyst. This removes the cost of catalyst preparation as well as the cost of recovery of the catalyst from the reaction products.

Once the lignin depolymerization reaction is complete, a filter press or the like is used to separate the lignin free fibers from the solvent phase containing the depolymerized lignin. Any remaining solvent in the fibers is removed by drying, where the solvent is then recaptured and reintroduced into the process. The liquid phase from the filter press is then put into a flash evaporator and/ or a distillation unit to remove some, but not necessarily all, of the solvent thereby concentrating the depolymerized lignin and any other components in the liquid phase. The solvent is recycled back to the process.

The resulting brown liquor contains the depolymerized lignin as well as other components such as sugars, hemi-cellulose, small amounts of small cellulose fibers that made it past the filter press, as well as silica and other inorganic material. Any remaining cellulose fibers and inorganic particulates like silica are removed in a settling tank or by mild centrifugation.

Liquid-liquid Extraction for Production of Clean Lignin.

In some embodiments it is desirable to remove the hemi-cellulose and sugars from the brown liquor, where the process needed for the removal of these components from the brown liquor is shown in the Clean Lignin sub-box in Fig. 1.

An aqueous salt solution with sufficient molarity forms a two-phase mixture at room temperature with organic solvents (for example, 1 M NaCl in methanol at room temperature yields a two-phase mixture). The sugars and hemi-cellulose are primarily in the aqueous phase, while the depolymerized lignin remains primarily in the organic phase. Thus, liquid-liquid extraction can separate the sugars and hemi-cellulose from the brown liquor, resulting in clean depolymerized lignin.

The sugars and hemi-cellulose can be separated from the salt solution using standard membrane technology, where the aqueous salt solution is then recycled to the process. The sugars and hemi-cellulose are a product of the process in addition to the clean depolymerized lignin and the clean cellulose fibers.

Example Depolymerized Lignin Feedstock

Depolymerized lignin feedstock was provided as described above. The lignin monomer feedstock was prepared by 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 has also been removed. However, the remaining reaction mixture was not purified any further. This mixture contains propyl methoxyphenols (see FIG. 2) as the main components, but also includes other minor reaction products including xylose as well as residual methanol solvent.

One attractive feature 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 include:

1. Unpurified depolymerized lignin monomer mixture

2. Polycup 9700 curing agent. POLYCUP is a registered trademark of Solenis Technologies, LP, a Delaware Limited Partnership, 3 Beaver Valley Road, Suite 500, Wilmington, DELAWARE, 19803, reg. no. 0863338. Polycup is a commercial crosslinking resin. Polycup is a water soluble polyamide-epichlorohydrin (PAE) resin curing agent. The secondary amine in the polyamide and the epichlorohydrin have reacted to form an azetidnium complex as shown in FIG. 3. 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.

3. Fiber. Different types of wood fiber are used for different applications, wherein hard-wood and soft-wood fiber from mixed elm, oak, ash, hickory, maple, chestnut, birch, and poplar were selected, the mixture including low amounts of soft wood such as spruce, pine and hemlock. These were sourced from within a 100-mile radius of Clarion, PA. These woods are typically used in the production of medium density fiber (MDF) boards. Characteristics of the fiber product include a soft, fibrillated fluffy texture with a refined, short fibers with 10% moisture. 4. Glyoxal. Glyoxal is a small molecule organic compound that is used in the wood/ paper industries to crosslink cellulosic material in wood/paper products (see FIG.

4).

5. Wax. Two different types of paraffin based waxes were investigated. Chlorez 700 is a powdered solid paraffin based wax that is 70% chlorinated (70% chlorinated alkane), that imparts both water repellency as well as some flame retardancy. CHLOREZ is a registered trademark of the Dover Chemical Corporation, an Ohio corporation, 3676 Davis Road NW, Dover, Ohio, 44646, reg. no. 5584109. During manufacture Chlorez will off-gas HC1 which might play a role in the reaction of the Polycup with the lignin monomer. ULTRALUBE E345 is a paraffin wax used for water repellency that is an anionic water-based paraffin emulsion with 45% solids content. 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. The molecular weight of Chlorez is approximately 35Og/mole while 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 (see FIG. 6). 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 studied and may likewise be selected. Other compounds that have been studied include:

7. Azideine is a potential alternative crosslinker to the Polycup.

8. Cyanuric acid is a potential alternative crosslinker to the Polycup. 9- Carbodiimide is a potential alternative crosslinker to the Polycup.

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

In general, the curing agent maybe selected from the group consisting of Polycup (specifically Polycup 9700, although other Polycup formulations maybe elected), azideine, cyanuric acid, carbodiimide, gamma-aminopropyltriethoxysilane, and combinations thereof.

The ten components above were explored to determine which components would provide an alternative to the current formaldehyde based thermoset resins. In addition, a traditional phenol-formaldehdye resin system was prepared as a reference standard, serving as the target material with which to compare the properties of the instant novel binder systems.

Composite Manufacturing Process

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 vessel

4. Add in processes cellulose material if desired

5. If powdered solid wax, such as Chlorez 700, is used, add the wax to the cellulose fibers and mix until a homogeneous admixture is yielded

6. Measure the specified amount of water, methanol, and lignin monomer, and glyoxal; water is about 25 weight percent of this mixture and methanol is about 15 weight percent of this mixture 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; add the SMA dispersant and mix until homogeneous Spread the lignin monomer/ glyoxal mixture from a pipette over the fibers and mix the resulting wet fiber mixture well Spread the wax and SMA mixture from a pipette over the fibers and mix the resulting wet fiber mixture well A cardboard template (about 2mm thick) with a cutout approximately 3” x 2” is covered with aluminum foil; release agent is applied between the foil and an aluminum plate on a hot press to prevent any curing of the template to the plates of the hot press The mixture of fiber, crosslinker, lignin, and wax is placed into a mound in the center of the cardboard template, where the template is already at the cure temperature (in this example 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 The press is closed and 1400 pounds force is applied; the mixture is cured at 192°C for 6 minutes; the force from the press is used to make sure that fiberbinder 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; 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 not homogeneous

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 to screen for gross mechanical behavior. Specifically, the samples were bent 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 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. 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, 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).

3. 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 D1037-99: 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 desirable application feature, where if composite flooring or furniture get wet it returns to its original state upon drying, that has insurance implications.

4. 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 binary epoxy adhesive, and then the pull rod with composite samples was subjected axial deformation in a 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 (see 3 above), (b) the strength from a pull test (see 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 D1037-99. Tests (c) through (f) are all related to (a) and (b), where the simple 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 are 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. 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% formaldehydemrea) 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. Test panels for the PMDI system were produced 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 should 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 deligninization 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, carbodiimide and gammaaminopropyltriethoxysilane were not considered further, although it is possible with additional work the amounts and cure cycle could be modified to increase the efficacy of these systems.

Investigation of Binder Systems for Crosslinking Resin System and Water Absorption The second experimental tranche was to focus in on the Polycup and azideine cure packages, where we now added to additional components to the formulation: (i) glyoxal and SMA to bind the sugars and hemi-cellulose that are also part of depolymerized lignin monomer mixture and (2) various waxes to improve the water adsorption properties of the composite material.

Examining the data in Table 2 we observe:

1. With the addition of waxes it is possible to decrease the amount of lignin in order to achieve the same water absorption behavior (although composite strength may require the same, or even more, lignin upon addition of the wax). Notice, that all ‘green’ thickness swell samples in Table 2 are superior to the current ureaformaldehyde system with a thickness swell of 8% or greater. The no-wax Sample P has 26 wt% lignin monomer with a 2% thickness swell; in contrast, Samples U, V, AA, AB and AC use between 19 to 22 wt% of lignin monomer and still obtain acceptable water adsorption behavior. A potential mechanism is that the more tightly crosslinked binder system that occurs for high lignin monomer content reduces water adsorption, where if wax is present and coats the fiber then the network does not have to be as tightly crosslinked to achieve similar water adsorption characteristics. Note: the phenolated species in lignin is about 45 wt% of the depolymerized-lignin, where the remaining material is 45 wt% disaccharides and 10% other components.

*Sample C broke in press

2. In addition to wax being able to reduce the amount of lignin monomer from upper 26 to 31 weight percent to between 19 to 22 weight percent, less glyoxal is required needed (see P through T as compared with Z through AC).

3. Examining the data for Samples S and W, it is clear that simply removing polycup (Sample S) or removing ligin material (Sample W) will result in poor board properties. However, the extraction test for Sample S is interesting as it shows increasing glyoxal with decreased leaching.

4. The cationic wax caused the samples to fail prematurely and not form a cohesive board. The data may indicate that increasing the ionic character of the reaction mass affects the cure chemistry of Polycup with the depolymerized lignin. 5. In using Epoline wax, the amount of water adsorbed decreased as the amount of Epoline was increased, but the mechanical properties were significantly decreased.

6. Both Chlorez and ULTRALUBE E345 showed the promising results. Sample V with PE 668 (polyethylene wax) was promising as well but required that the powdered PE 668 wax be heated and “melted” to the fibers before being placed into the press.

Based upon the analysis above, only Chlorez 700 and ULTRALUBE 345 passed onto the subsequent tranche.

* Samples W and X broke in press

Refinement of Binder Systems for Water Adsorption

In the third experimental tranche, the focus was tightened to the most promising formulations. Specifically, (i) only two wax systems were considered - Chlorex and ULTRALUBE 345 and (ii) the amounts of Polycup, glyoxal and SMA were optimized to provide optimal water adsorption behavior. The results of the brittle test and water adsorption are shown in Table 3. For these systems the time dependent water adsorption was also measured and is plotted in Fig. 7.

Examining the data in Table 3 and Fig. 7 we observe:

1. The thickness of the sample immediately increases upon immersion in water and then decreases (note: the zero time in Fig. 7 is after first soaking in water for 24 hours). This decrease is because the moisture is leaving the sample, as compared to the industry standard urea-formaldehyde system where the thickness increase after drying for 48 hours following the 24 hour soaking period range from 8 to 20%.

2. Samples below show that the optimal results for water adsorption were achieved using a combination of ULTRALUBE E345 and Chlorezyoo. With the appropriate ratio of these two waxes it is possible that adsorbed water evolves into the atmosphere as shown in samples AJ and AK.

3. The addition of process cellulose chips (Sample AK) made the board too pliable in the mechanical test. This is probably a result of the small length and particle size of the process cellulose material.

4. The moisture adsorption results for samples AD through AL are significantly better than the current industry standard of 7 to 20% thickness swell.

5. The data in Fig. 1 shows the rate of drying. Samples AD, AK, AL show a higher rate of drying, but have a larger initial thickness swell. Samples AE and AF exhibit permanent deformation after the 24-hour water soak with surface fibers becoming “fluffier”.

The tranche summarized in Table 3 shows that with the appropriate choice of waxes a binder system based upon the depolymerized lignin can be developed that has superior moisture adsorption properties that the current urea-formaldehyde systems.

Evaluation of Binder Systems for Combined Water Adsorption and Mechanical Strength

The results of final experimental tranche are shown in Table 4, where now for the first time obtained quantitative measurements of the initial modulus and strength were obtained. Examining the data in Table 4 it is observed:

1. Water adsorption is far superior in composite boards made from the depolymerized ligin as compared to industry standard. Specifically, the current materials standard for thickness swell is between 8 to 20 percent; in contrast, composite boards made with the depolymerized lignin monomer only exhibit swelling of o to 4%.

2. The sample Al exhibited a modulus of 37.5 kpsia. The composite made from the urea-formaldehyde samples only had a modulus of 0.010 kpsia modulus, where this low modulus was a consequence of using a small amount of formaldehyde to control emissions. The 15% polyethelyene enriched PDMI sample was able to achieve 15.5 kpsia, which is considered acceptable for many composite board applications.

3. Tensile strength of sample Al is excellent with a value of 87 psia as compared to 35 psia for the standard urea-formaldehyde composite. In addition the water absorption is also excellent where the specimen returned to its original thickness after 48 hrs of drying following 24 hrs of emersion in water.

Based upon the data in Table 4, sample Al has the best combination of properties, although future improvement in properties and or reduction of material costs is possible.

Summary

Based upon the data in Table 4 we have been able to develop a formaldehyde free binder system using the depolymerized lignin monomer (including additional sugars, hemi-cellulose and residual methanol solvent) that has water adsorption, modulus and tensile strength that are superior to that of the current binder systems used for woodbased composite board products. As shown in Table 5, the Al system is substantially better than the current urea-formaldehyde and PDMI with polyethylene systems, where (i) the water absorption after 48 hrs of drying is essentially zero as compared to thickness changes of between 7 and 8% for the two industry standards and (ii) both the modulus and tensile strength for the lignin monomer system is more than twice that of the two current materials. Thus, the formulated lignin monomer system exhibits significantly better physical properties that the current binder systems for composite boards and is formaldehyde free.

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.

Claims

Claims I claim:

1. A method of making composite board, comprising: a) providing a first quantity of methanol exploded biomass fibers; b) placing the first quantity of methanol exploded biomass fibers into pressure vessel; c) introducing an organic solvent, hydrogen gas, nitrogen gas, and acid into the pressure vessel to define a first admixture; d) heating the first admixture under increased pressure to yield a quantity of unpurified depolymerized lignin; e) mixing the quantity of unpurified depolymerized lignin with predetermined quantities of fiber, curing agent, paraffin wax, glyoxal, and dispersant to define a second admixture; and f) bonding the second admixture with cardboard to yield a composite board.

2. The method of claim 1 wherein during f), the second admixture is hot pressed into the cardboard.

3. The method of claim 2 wherein during f), hot pressing is accomplished at about 192 degrees Fahrenheit.

4. The method of claim 1 wherein the organic solvent is methanol.

5- The method of claim i wherein during e), cellulose is added to the second admixture.

6. The method of claim 1 wherein the curing agent is selected from the group consisting of Polycup 9700, azideine, cyanuric acid, carbodiimide, gammaaminopropyltriethoxysilane, and combinations thereof; wherein the paraffin is selected from the group consisting of seventy percent chlorinated alkane, anionic water-based paraffin wax emulsion with a solid content of about forty-five percent, polyethylene wax, and combinations thereof; and wherein the dispersant is styrene-maleic anhydride.

7. The method of claim 1 wherein the composite board is formaldehyde-free.

8. The method of claim 7 wherein the composite board exhibits no more than four percent swelling upon exposure to water; wherein the composite board has a modulus of at least 30 kpsia; wherein the composite board has a tensile strength of at least 70 psia; and wherein the composite board returns to its original thickness after forty-eight hours of drying following a twenty-four hour immersion in water.

9. A method of preparing a composite board, comprising: g) soaking a first quantity of biomass fibers in methanol to yield a second quantity of methanol infused biomass fibers; h) placing the second quantity of methanol infused biomass fibers into a first pressure vessel to increase pressure therein; i) rapidly reducing pressure within the pressure vessel to yield a third quantity of methanol exploded biomass fibers; j) placing the third quantity of methanol exploded biomass fibers into a second pressure vessel; k) introducing methanol, hydrogen gas, nitrogen gas, and acid into the second pressure vessel to define a first admixture; l) heating the first admixture under increased pressure to yield a quantity of unpurified depolymerized lignin; m) mixing the quantity of unpurified depolymerized lignin with predetermined quantities of fiber, curing agent, paraffin wax, glyoxal, and dispersant to define a second admixture; and n) bonding the second admixture with cardboard to yield a formaldehyde- free composite board; wherein the composite board exhibits no more than four percent swelling upon exposure to water; wherein the composite board has a modulus of at least 30 kpsia; wherein the composite board has a tensile strength of at least 70 psia; wherein the composite board returns to its original thickness after forty-eight hours of drying following a twenty-four hour immersion in water; wherein the curing agent is selected from the group consisting of Polycup 9700, azideine, cyanuric acid, carbodiimide, gamma-aminopropyltriethoxysilane, and combinations thereof; wherein the paraffin is selected from the group consisting of seventy percent chlorinated alkane, anionic water-based paraffin wax emulsion with a solid content of about forty-five percent, polyethylene wax, and combinations thereof; and wherein the dispersant is styrene-maleic anhydride.