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(11) | EP 4 464 482 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | COMPOSITE LUMBER AND METHOD OF MAKING THE SAME |
| (57) The present disclosure relates to a wood alternative; composite lumber and method
of making the same. The composite lumber includes a plant fiber strand mat, wherein
the fiber within the strand mat partially separate along a longitudinal direction
and a binder. The method of making a composite material includes slicing the stock
(300) longitudinally; forming a fiber mat (500) by compressing the sliced stock (302)
so that the fiber (502) within the sliced stock partially separates; mixing with a
binder; heating and curing at elevated temperature and pressure. Such wood-alternative
composite lumber provides environmentally friendly and sustainable lumber sources
for regions lacking natural forest resources.
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TECHNICAL FIELD
[0001] The application relates to the field of lumber like composite materials, and more particularly environmentally sustainable wood alternatives for use as lumber for furniture making and construction and method of making the same.
BACKGROUND
[0002] Historically, wood has been the primary material used in furniture making due to its durability, versatility, and aesthetic appeal. Wood is also widely used in construction. However, in regions that lack forests, obtaining wood for furniture making can be challenging.
[0003] In such regions, the demand for lumber products often exceeds the available supply, leading to the depletion of local forests and the destruction of natural habitats. There is a growing need for innovative solutions to address the challenges of obtaining wood for furniture making and construction building materials in regions that lack forests.
[0004] In recent years, the use of composite materials has gained popularity in construction due to their durability, sustainability, and lower costs. One promising solution for obtaining composite lumber materials is through the use of biomass fiber, which includes waste products from other industries like sugarcane bagasse and straw, which can be processed and transformed into composite lumber materials with similar properties to traditional wood lumber.
[0005] Using composite lumber materials sourced from biomass fiber offers several advantages over traditional wood lumber. Firstly, these materials can be produced using byproducts or waste products from other industries, reducing waste and promoting sustainability. Secondly, composite lumber materials can be designed to have specific properties, such as strength, durability, and resistance to moisture and pests, making them ideal for use in furniture making and construction. Thirdly, composite lumber materials are typically less expensive than traditional wood lumber, which can help to reduce construction costs, making it more affordable and accessible to a wider range of consumers. Additionally, since these materials are often produced locally, they can help to support local economies and reduce the environmental impact of transporting materials over long distances.
[0006] At present, products have been developed and utilized such as in the bamboo industry, namely bamboo scrimber and the like, to address the aforementioned issue. However, these products include several undesirable characteristics.
[0007] First, many earlier products are of a higher density, e.g., bamboo scrimber is typically at 1,200 kg/m3. A lower density e.g., 900kg/m3 - 1,100kg/m3 wood-alternative is more useful for furniture carpentry.
[0008] Second, earlier products use less environmentally friendly bonding agents such as phenolic urea resins, which utilize formaldehyde in the manufacturing process. A more environmentally friendly bonding agent prioritizes the sustainable objective underlying the desire for such wood-alternatives.
[0009] Third, earlier products may use materials that present chemical danger on workers or only be available in larger quantities, making the product less suitable for small-to-medium scale local industries. Safer chemicals, like polyester powder, are available in smaller packages and in local markets, making the product more suitable to be implemented in smaller scale local industries.
[0010] It is desired to provide a wood-alternative, and to provide a method of making the wood-alternative, incorporating any or all of the aforementioned qualities.
SUMMARY OF THE INVENTION
[0011] The claimed invention provides a composite material, comprising at least 90% w/w plant fiber strand mat, wherein fiber bundles within the strand mat are partially separate along a longitudinal direction, wherein the fiber bundles within the strand mat are of a width and height of 2-4mm on average; and a binder of about 1-10 w/w, wherein the composite material have a density of (800kg/m3 - 1,100kg/m3).
[0012] According to one aspect of the present invention, the plant fiber strand mat is formed by slicing longitudinally along the length of a stock material and mechanically compressed to partially separate the fiber bundles within the strand mat.
[0013] According to another aspect of the present invention, the stock material is selected at least from palm leaf midrib or stem of Miscanthus.
[0017] According to a further aspect of the present invention, the thermoplastic binder.is selected from at least one of polyester, polyethylene, polypropylene, polycarbonate, polyvinyl chloride, acrylonitrile butadiene styrene, nylon, polystyrene, polyethylene terephthalate, polyurethane, and polylactic acid.
[0019] According to another aspect of the present invention, the thermal setting binder.is selected from at least one of polyvinyl acetate, epoxy resins, phenolic resin, polyester resins, polyurethane resins, acrylic resins, melamine resins, cyanate ester resins, and silicone resins.
[0020] The present invention also provides a method of making a composite material comprising the steps of: slicing a stock material longitudinally; forming a strand mat by compressing the sliced stock material so that fiber bundles within the sliced stock partially separates longitudinally; wherein the fiber bundles within the strand mat are of a width and height of 2-4mm on average; mixing with a binder; compressing the strand mat mixed with binder; and curing at elevated temperature and pressure.
[0021] According to one aspect of the present invention, the stock plant material is selected from at least palm leaf midrib or stem of Miscanthus.
[0022] The method of claim 10, wherein forming the strand mat is by compressing the sliced stock material between a pair of expansion rollers.
[0026] According to another aspect of the present invention, the thermoplastic binder.is selected from at least one of polyester, polyethylene, polypropylene, polycarbonate, polyvinyl chloride, acrylonitrile butadiene styrene, nylon, polystyrene, polyethylene terephthalate, polyurethane, and polylactic acid.
[0028] According to another aspect of the present invention, the thermal setting binder is selected from at least one of polyvinyl acetate, epoxy resins, phenolic resin, polyester resins, polyurethane resins, acrylic resins, melamine resins, cyanate ester resins, and silicone resins.
[0029] According to a further aspect of the present invention, curing is at about 200°C and 30-40Mpa.
BRIEF DESCRIPTION OF DRAWINGS
[0030]
FIG. 1 is an illustration of a frond of a date palm leaf with the midrib;
FIG. 2A is an illustration of a section of a palm leaf midrib with leaflets removed and ends trimmed;
FIG. 2B is a photo showing samples of palm leaf midribs;
FIG. 3 is an illustration of slicing midrib;
FIG. 4A is an illustration of a palm leaf midrib slice;
FIG. 4B is a photo showing samples of palm leaf midrib slices;
FIG. 5A is an illustration of a palm leaf midrib strand mat;
FIG. 5B is a photo showing samples of palm leaf midrib strand mats;
FIG. 5C is a photo showing exemplary strand mats mixed with a binder and assembled in a mold;
FIG. 5D is a photo showing exemplary composite lumber material; and
FIG 6 is a flow chart illustrating a method of making composite lumber material.
DETAILED DESCRIPTION
[0031] In the drawings, like numerals indicates like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The embodiments illustrated below are not intended to be exhaustive or to limit the invention to the precise form disclosed. These embodiments are chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention.
[0032] FIG. 1 an illustration of a frond of a date palm leaf 100 with the midrib 110. Leaflets are attached to the midrib 110. The midrib is generally tapering along the length of the frond. FIG. 2A is an illustration of a section of a palm leaf midrib 200 with leaflets removed and ends trimmed. FIG. 2B is a phot showing processed midribs.
[0033] FIG. 3 is an illustration of a midrib 300 being sliced into multiple thin slices 302. In some embodiments the midrib 300 is sliced 300 to a thickness between about 1mm and 10mm. Typically, the midrib 300 can be sliced with a saw, planer, or a slicer.
[0034] FIG. 4A is an illustration of a sliced midrib 400. In this particular embodiment, the midrib is sliced to a thickness of 3mm. FIG. 4B is a photo showing some exemplary midrib slices. The slices of midrib 400 are then mechanically processed to form strand mats. The mechanical process to produce strand mats typically involves using pressure to partially separate the fiber bundles within the strand mats along the longitudinal direction without cutting the fiber bundles.
[0035] FIG. 5A is an illustration of a palm leaf midrib strand mat 500. In some embodiments, the typical dimension (i.e., width and height) of the partially separated fiber bundles 502 in a range of 1x1 mm to 10x10mm on average, and preferably 2x2mm to 4x4mm on average. In this particular embodiment, the typical dimension of the partially separated fiber bundles 502 are about 3x3mm on average.
[0036] The strand mat 500, for example, can be formed by passing the sliced midrib 400 through expansion rollers. The expansion rollers apply pressure to the sliced midrib section 400, and partially separate the fiber of the sliced midrib section 400 along the longitudinal dimension. The fiber within the strand mat 502 retains its longitudinal integrity. FIG. 5B is a photo showing examples of palm leaf midrib strand mats.
[0037] The strand mats 502 may be coated with a binder. A dry process, e.g., using binder in the powdered form is typically preferred. Based on the type of production process employed for the later steps of compression and curing, different binders may be used. An example of such binder can be a thermoplastic binder. Thermoplastic binders are materials that soften and become malleable when heated and then solidify when cooled. Some common examples of thermoplastic binders include polyethylene, polypropylene, polycarbonate, polyvinyl chloride, acrylonitrile butadiene styrene, nylon, polystyrene, polyethylene terephthalate, polyurethane, and polylactic acid. In one embodiment, the thermoplastic powder is a polyester powder. In some embodiments, the weight from the thermoplastic powder is in a range of 1% to 10% w/w. Preferably, the weight from the thermoplastic powder is less than 6%, more preferably in a range of 4% to 6% w/w. In some embodiments, the strand mats may be at 5% to 35% humidity when measuring mass. Higher humidity level may protect the strand mats from browning in the subsequent curing process.
[0038] The strand mats coated with binder may be subsequently cold pressed into desired molds. The mold can be of regular shape to produce lumber like composite, or of specific shape that may be directly used for downstream processing. FIG. 5C is a photo showing exemplary strand mats mixed with a binder and assembled in a mold.
[0039] The molds containing strand mats coated with binder may be then transferred to an oven to activate a curing process. In some embodiments, the curing oven temperature may vary depending on the binder. In one particular embodiment where polyester binder is used, the curing oven may be at 200°C. Optimal temperature need to be found for each specific binder based on the properties of the binder of choice. Typically, curing temperature of 180-200°C is desirable as higher temperature may cause browning of the strand mats.
[0040] The molds may then be cooled after curing. In some embodiments, the product may be demolded to complete the formation of composite lumber. FIG. 5D is a photo showing exemplary composite lumber material.
[0041] The general process discussed above may also be adapted for other fibrous plant stock material. One additional example is Miscanthus. Miscanthus is traditionally not suitable for use as a building material. However, with the inventive process described herein, Miscanthus can be use as the stock fiber material to create composite lumber that suitable for both indoor and outdoor use.
[0042] A specific example suitable as the feed stock for the composite material is Miscanthus Giganteus. Miscanthus Giganteus can grow on marginal land. It is water efficient, non-invasiveness, requires no or low fertilizer, and can offer significant carbon sequestration and high yield. Miscanthus stem is typically tube-like of round cross-section. Miscanthus stem can first be sliced longitudinally, typically in half, and mechanically processed, e.g., pressed or crushed, to form fiber strand mat in a process similar to the above described process for processing palm leaf midribs. The mechanically processed Miscanthus fiber strand mat has fiber bundles of preferred dimensions of 2-4 mm on average, and having partially separated fiber along the longitudinal axis. Miscanthus stem section may vary in diameter and wall thickness along the length of the stem without a noticeable effect on the proprieties of the resulting composite, when processed into the strand mats of preferred dimensions.
[0043] Miscanthus fiber strand mat can then similarly mixed with a binder and compressed and heated to form a composite lumber.
[0044] FIG. 6 provides a flow chart of exemplary steps of manufacturing composite from plant fiber stock materials. First, the stock plant material (e.g., palm leaves or miscanthus) is trimmed of leaves or leaflets, and cut to appropriate length 610. The trimmed and cut stock material is then sliced longitudinally to thin slices 620. Typical thickness of the slices are between 1-10mm, and preferably 2-4mm. In the example for palm midrib shown above, the preferred thickness is about 3mm.
[0045] The sliced stock material is then mechanically processed to form strand mats 630. Typically, the sliced stock material is pressed between a pair of expansion rollers. Other method of partially separating the fibers within the sliced stock material can also be used. The strand mats having the fiber bundles within the stock material partially separated along the longitudinal dimension, but largely maintaining the full length of the fiber. The distance between the expansion rollers can be adjusted to produce the optimal amount of separation of the fiber bundles and preferred dimension.
[0046] The strand mats are then mixed with a binder 640. In some embodiments, the weight from the thermoplastic powder is in a range of 1% to 10% w/w. Preferably, the weight from the thermoplastic powder is less than 6%, more preferably in a range of 4% to 6% w/w. The binder may be a thermoplastic powder. A preferred thermoplastic powder is a polyester powder. The mixing step can be conducted in a drum mixer. The binder coated strand mats can then be compressed, such as placing in a mold, 650 and applying pressure. It is preferred that the fiber bundles within the strand mats are generally aligned with the longitudinal dimension of the mold. For a mold longer than the typical length of the stand mats, overlapping of the stand mats within the mold is expected. The mold containing the binder coated strand mats are then cured in a curing oven at an alleviated temperature and pressure 660. The curing oven temperature may vary depending on the thermoplastic powder type. In one particular embodiment where a polyester binder is used, the curing oven may be at about 200°C. Pressure during the curing process is typically 30-40Mpa. The composite lumber material can then be released after a period of cooling 670.
[0047] The present invention may also be produced in a continuous process, where the strand mats may be mixed with a binder, compressed and cured at desired temperature and pressure in a continuous production line and curing oven. The resulting composite lumber may then be cut to desirable sizes.
[0048] A thermal setting binder is preferred in the continuous process. Thermal setting binders are materials that harden or solidify through the application of heat. Some common thermal setting binders include: epoxy resins, phenolic resin, polyester resins, polyurethane resins, acrylic resins, melamine resins, cyanate ester resins, and silicone resins.
[0049] Additional exemplary polymers also can be used in the continuous process include polyvinyl acetate, which is commonly found in wood glue. Liquid or powdered polyvinyl acetate may be used for the continuous manufacturing process.
[0050] There is typically a naturally occurring wax like substance found on the outer skin of the stock material. The wax like material can inhibit adhesion with the binder. For stock material such as bamboo, the outers skin is typically removed before processing the stock material into bamboo scimber. Given the natural dimensions of palm leaf midribs and miscanthus stems, removing the outer skin is impractical. However, processing the stock material to have partially separated fiber bundles of 2-4mm (width and height) on average, eliminates the need to remove the outer skin. The fine fiber bundles admixed with the thin strands of broken down outer skin and binder can adhere satisfactorily with heat and pressure in the curing process.
[0051] Also, typically bamboo fiber bundles are of larger dimensions such as greater than 5x5mm, and more typically greater than 10x10mm. This requires high pressure during the curing process, which is necessary to remove the relatively large void space among the fiber bundles. This also result in a composite material that is of higher density (e.g., greater than 1,200 kg/m3 and not suitable for use in furniture making. The preferred dimensions of the fiber bundle of the present invention (e.g., 2-4mm on average) reduce the void space among the fiber bundles, which requires less pressure during the curing process. This provides a more energy efficient process of manufacturing, and results in a composite material that is of density of 900-1,100 kg/m3, suitable for furniture making.
MECHANICAL PERFORMANCE PROPRIETIES OF MIDRIB COMPOSITE
[0052] Composite is showing clear mechanical resistance advantage over natural wood (e.g., red pine) products. The palm life midrib composite is of higher density and out performs red pine in tensile strength and bending resistance strength.
| Proprieties | Palm Leaf Midrib Composite | Red Pine | Unit |
| Density | 1000 | 550 | Kg/m3 |
| Tensile strength (parallel to fiber) | 69 | 10.5 | N/mm2 |
| Tensile strength (perpendicular to fiber) | 2.5 | 2 | N/mm2 |
| Bending resistance strength | 178 | 37.2 | N/mm2 |
EFFECTS OF HUMIDITY ON COMPOSITE
[0053] In this humidity effect test, the mass variation and thickness variation values of the composites according to certain embodiments of the invention are equal to the values of mass variation and thickness variation of raw fiber samples.
MISCANTHUS COMPOSITE (MISCANTHUS GIGANTUS):
[0054] The table below illustrates the average result values of tests conducted on composite samples. According to norm NT 27.38 (test samples submerged in water for 24 hours). The data shown below demonstrate that composite of Miscanthus does not absorb significant amount of water and minimal dimension change when submerged in water for 24 hours.
| Sample mass variation | Sample cross grain thickness variation |
| +15% | +4% |
PALM MIDRIB COMPOSITE:
[0055] The table below illustrates the average result values of tests conducted on composite samples (made from thin and thick part of midrib). According to norm NT 27.38 (test samples submerged in water for 24 hours).
| Sample mass variation | Sample cross grain thickness variation | |
| Thin half | +100% | +25% |
| Thick half | +27% | 8% |
[0056] From the water absorption data shown above, the composite made from Miscanthus shown superior water resistance.
[0057] Although exemplary implementations of the invention have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.
[0058] It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting, but are instead exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the terms "comprising" and "wherein." Moreover, in the following claims, the terms "first," "second," and "third," are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112, sixth paragraph, unless and until such claim limitations expressly use the phrase "means for" followed by a statement of function void of further structure.
1. A composite material, comprising:
at least 90% w/w plant fiber strand mat,
wherein fiber bundles within the strand mat are partially separate along a longitudinal direction,
wherein the fiber bundles within the strand mat are of a width and height of 2-4mm on average; and
a binder of about 1-10 w/w, wherein the composite material have a density of (800kg/m3 - 1,100kg/m3).
2. The composite material of claim 1, wherein the plant fiber strand mat is formed by
slicing longitudinally along the length of a stock material and mechanically compressed
to partially separate the fiber bundles within the strand mat.
3. The composite material of claims 1-2, wherein the stock material is selected at least
from palm leaf midrib or stem of Miscanthus.
4. The composite material of claims 1-3, wherein the binder is less than 6% w/w.
5. The composite material of claims 1-4, wherein the binder is 4- 6% w/w.
6. The composite material of claims 1-5, wherein the binder is a thermoplastic binder.
7. The composite material of claim 6, wherein the thermoplastic binder is selected from
at least one of polyester, polyethylene, polypropylene, polycarbonate, polyvinyl chloride,
acrylonitrile butadiene styrene, nylon, polystyrene, polyethylene terephthalate, polyurethane,
and polylactic acid.
8. The composite material of claims 1-5, wherein the binder is a thermal setting binder.
9. The composite material of claim 8, wherein the thermal setting binder is selected
from at least one of polyvinyl acetate, epoxy resins, phenolic resin, polyester resins,
polyurethane resins, acrylic resins, melamine resins, cyanate ester resins, and silicone
resins.
10. A method of making a composite material comprising the steps of:
slicing a stock material longitudinally;
forming a strand mat by compressing the sliced stock material so that fiber bundles
within the sliced stock partially separates longitudinally;
wherein the fiber bundles within the strand mat are of a width and height of 2-4mm
on average;
mixing with a binder;
compressing the strand mat mixed with binder; and
curing at elevated temperature and pressure.
11. The method of claim 10, wherein the stock plant material is selected from at least
palm leaf midrib or stem of Miscanthus.
12. The method of claim 10, wherein forming the strand mat is by compressing the sliced
stock material between a pair of expansion rollers.
13. The method of claim 10-12, wherein the binder is 1-10% w/w.
14. The method of claim 10-13, wherein the binder is 4-6% w/w.
15. The method of claims 10-14, wherein the binder is a thermoplastic binder.
16. The method of claim 15, wherein the thermoplastic binder is selected from at least
one of polyester, polyethylene, polypropylene, polycarbonate, polyvinyl chloride,
acrylonitrile butadiene styrene, nylon, polystyrene, polyethylene terephthalate, polyurethane,
and polylactic acid.
17. The method of claims 10-14, wherein the binder is a thermal setting binder.
18. The method of claim 17, wherein the thermal setting binder is selected from at least
one of polyvinyl acetate, epoxy resins, phenolic resin, polyester resins, polyurethane
resins, acrylic resins, melamine resins, cyanate ester resins, and silicone resins.
19. The method of claims 10 - 18, wherein curing is at about 200°C and 30-40Mpa.