Wood mass composition for 3D printing of wooden objects, manufacturing process and use

Abstract

Wood mass composition for 3D printing of wooden objects, containing the following components (proportions based on weight): a) 100 ± 10 % Parts wood fiber / wood flour mixture b) 10 ± 10 % Methylcellulose c) 10 ± 10 % parts guar gum d) 10 ± 10 % Parts oil e) 8 ± 10 % parts alcohol f) 2 ± 10 % Parts shellac g) 300 ± 10 % parts of water h) 6 ± 10 % Parts of casein powder i) 6 ± 10 % parts slaked lime

Description

[0001] The invention relates to a wood mass composition for the 3D printing of wooden objects, a method for producing the wood mass composition, a method for producing three-dimensional wooden objects and the use of the wood mass composition for producing three-dimensional wooden objects. Background of the invention

[0002] Printing three-dimensional objects, also known as 3D printing, is a manufacturing process in which layers of material are applied to the preceding layers, thereby iteratively building the object (additive manufacturing). 3D printing allows for the quick and cost-effective production of customized objects in any shape directly on-site.

[0003] Thermoplastics are most commonly used for 3D printing, but various other materials such as metals, concrete, or glass are also employed. The material is typically extruded through a nozzle by an extruder, which is controlled and moved by a computer based on CAD data containing the geometric design data of the object to be printed (CAD / CAM). The material is applied in very thin layers and cured before the next layer is applied. This makes it strong enough to build any shape.

[0004] Therefore, attempts have also been made to utilize the renewable raw material wood as a 3D printing material in order to produce wooden objects.

[0005] In one approach, small wood particles such as sawdust were used as a filler for thermopolymers like polylactic acid (PLA). Binding larger wood particles such as wood chips was attempted using gypsum, cellulose, sodium silicate, and cement. Besides fiber binding, a problem arises from the accumulation and clogging of the extrusion mechanism by the fibers.

[0006] Other approaches use either pure methylcellulose (paste) or conventional glue (cold glue such as "Ponal"®). However, paste offers only limited stability and is highly susceptible to water. Glue, on the other hand, is mostly PVC-based and therefore not sustainable from an ecological and economic perspective.

[0007] Other disadvantages associated with conventional approaches to 3D printing wooden objects include: 1. The wooden objects produced by 3D printing are neither large (only a few millimeters high) nor stable. 2. Most 3D printing materials do not use 100% sustainable (i.e., biodegradable, e.g., through natural decomposition, and / or recyclable) components, but contain inorganic components, e.g., cement, ceramics, plastics, or resins. 3. 3D printing materials are not standardized and have, for example, different moisture levels and particle sizes, making their behavior difficult to control. 4. The shrinkage of the 3D printing material during the drying process jeopardizes the integrity and dimensional stability of the object. 5. Fungal infestation jeopardizes the quality of the 3D printing material. 6. Printing larger objects requires thicker walls, which complicates the drying process. The taller the object, the thicker the walls, and consequently, the more moisture, mold growth, and dimensional instability. Problem and solution of the invention

[0008] The object of the invention arises directly from the disadvantages of the 3D printing materials used in the prior art for 3D printing wooden objects, as described above.

[0009] According to the invention, this problem is solved with a wood mass composition for 3D printing with the features of the main claim.

[0010] The invention further provides a method for producing the wood mass composition according to the invention with the features of claim 5 and a method for producing a three-dimensional wooden object with the features of claim 6. Finally, the invention also provides the use of the wood mass composition according to the invention for producing three-dimensional wooden objects according to claim 7.

[0011] Advantageous and / or preferred embodiments of the invention are the subject of the dependent claims.

[0012] Advantages of the wood mass composition according to the invention are: 1. The wood mass composition according to the invention contains only purely sustainable, i.e., biodegradable, e.g., through natural decomposition, and / or recyclable ingredients and consists predominantly of wood (at least 2 / 3, e.g., 70%). Only water needs to be added to the wood mass composition to enable 3D printing with all LDM (Liquid Deposition Modeling) printers. 2. The fibers used can be up to 5 mm long. This ensures optimal dimensional stability of the printed wooden object and a precise 3D printing result. 3. The viscosity of the wood pulp composition can be adjusted for 3D printing as required or desired, thereby increasing, for example, drying stability. This also increases the strength and dimensional stability of the printed wooden object. 4. Larger, taller (e.g. 30 cm high) and dimensionally stable (structurally stronger) wooden objects can be printed, e.g. individualized building elements, architectural elements and modules, furniture. 5. The printed wooden objects are 100% reusable, meaning they can be recycled either as building material or as compost. 6. The wood mass composition provided according to the invention can be stored and distributed like a cake mix. It can be prepared for use by adding water to create a ready-to-print paste optimized for 3D printing. 7. The wood mass composition according to the invention liquefies under pressure (e.g., in the extruder) and then becomes more viscous again due to shear forces (so-called "toothpaste effect"). This facilitates the layer-by-layer application required for 3D printing. Detailed description of the invention Definitions

[0013] The invention will be described in more detail below with reference to the figures, whereby the disclosed specific embodiments of the invention, examples or results are intended only for illustration and are in no way to be interpreted as a limitation of the scope of protection of the invention as defined in the attached claims.

[0014] It is understood that the invention is not limited to the specific methods, protocols, equipment, and reagents described herein, as these may vary. It is also understood that the terminology used herein serves only to describe certain embodiments and is not intended to limit the scope of the invention, which is limited only by the appended claims.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as understood by a person skilled in the art in the field of the invention. The person skilled in the art may also refer in full to the introductory explanations.

[0016] Each of the documents cited in this description (including all patents, patent applications, scientific publications, manufacturer specifications, instructions, etc.) is hereby incorporated in its entirety by express reference into the disclosure content of this invention. In the event of any conflict between the definitions or disclosures of such incorporated references and the definitions or disclosures of this description, the text of this description shall prevail.

[0017] The terms “comprising”, “has”, “contains” (or variations thereof, such as “comprises (encompasses)”), within the meaning of the present invention (particularly in connection with the claims), are to be understood as open terms or not as exclusive terms (i.e. in the sense of “including, but not limited to”), unless otherwise specified.

[0018] The term "comprehensive" is intended to include more restrictive terms such as "essentially consisting of" and "consisting of".

[0019] In the case of chemical compounds or compositions, the term "consisting essentially of" means that certain other components may be present, namely those that do not significantly affect the essential properties of the compound or composition, e.g. unavoidable impurities.

[0020] The use of definite or indefinite articles (“der”, “die”, “das”, “ein”, “eine”) in connection with the description (especially in connection with the claims) is to be read and understood as including at least one element or component (i.e., both singular and plural are to be included), unless otherwise stated in the description or the context clearly indicates otherwise.

[0021] The conjunction “or” is to be understood as an inclusive and not an exclusive “or”, i.e. as “and / or”, unless otherwise stated in the description or the context clearly indicates otherwise.

[0022] All numerical values, whether explicitly stated or not, are to be understood as "approximate" values ​​(at least within the usual margin of error). Furthermore, the specification of value ranges serves only as an abbreviation and, unless otherwise stated in the description or clearly indicated by the context, refers to every single value that falls within the range, even if that value is not individually specified.

[0023] The use of terms such as "for example", "e.g.", "like" or variations thereof is intended solely to better illustrate the invention and must in no way be interpreted as a limitation of the scope of protection of the invention as defined in the attached claims.

[0024] Wood fibers / wood flour, as used according to the invention, are predominantly generated as grinding dust during the sanding of wood, or through the grinding or fiberizing of wood or byproducts in wood processing. Depending on the fineness of the saw blade, sawing wood produces both sawdust and wood chips. The fine wood flour can be separated by sieving. Milling primarily produces chips. The smaller the particle size, the less influence the type of wood has. Important for further processing are the moisture content and the proportion of resins, fats, and waxes. The composition of the wood flours largely corresponds to that of wood and contains alpha-cellulose (up to 55%), hemicellulose (up to 25%), lignin (up to 30%), water (up to 6%), minerals, waxes, and fats.

[0025] Methylcellulose, as used according to the invention, is the methyl ether of cellulose, produced by the reaction of methyl chloride and alkali cellulose. It contains 27.58%–31.5% methoxy groups. Methylcellulose has a wide range of applications. In pharmaceuticals, for example, it serves as a binder, coating, or thickening agent (to increase the viscosity of liquid formulations). In the construction industry, it is added, for example, to dry mortar mixes to improve the mortar's properties such as workability, setting time, water retention capacity, viscosity, adhesion to surfaces, etc.

[0026] Guar gum (also known as guaran or guar flour), as used according to the invention, is a plant gum that is a very effective, natural thickening and gelling agent capable of binding many times its own weight in water / liquid. It is obtained from the guar bean plant. Guaran consists of D-mannopyranose units linked together in a chain-like fashion via β-1,4-glycosidic bonds. Furthermore, every second mannopyranose unit carries α-D-galactopyranosyl residues via a 1,6-linkage.

[0027] Linseed oil (also known as flaxseed oil or, pharmaceutically, "Oleum Lini"), as used according to the invention, is a vegetable oil obtained from flaxseed, the ripe seeds of the flax plant. Crude linseed oil is linseed oil without the addition of any other oils or substances. Besides common flax (Lex), other flax species (genus Linum) are also used for oil production. The linseed oil is obtained by pressing the flaxseed using a screw press. In this process, the flaxseed is forced through a press cylinder at low pressure by means of a screw roller. During cold pressing, oil temperatures of a maximum of 40 °C are reached. Before use, suspended solids are removed. This can be achieved by allowing the suspended solids to settle during sufficiently long storage and decanting the pure oil.Linseed oil contains mostly (90% and more) unsaturated fatty acids in its triglycerides and has a particularly high proportion of the omega-3 fatty acid α-linolenic acid of 45% to 71% (also about 10% to 22% oleic acid and 12% to 18% linoleic acid).

[0028] Tung oil, as used according to the invention (also called Chinese wood oil or Elaeococca oil), is a vegetable oil from the oil-rich seeds of various South Asian, tree-like species of the genus Vernicia. Tung oil differs from other vegetable oils in its particular chemical composition: It consists of up to 80% glycerides of α-elaeostearic acid, a triply unsaturated fatty acid. It also contains oleic acid residues, palmitic acid residues, and stearic acid residues, each bound as glycerol esters. Furthermore, tung oil exhibits a very characteristic behavior when heated, which is important for its technical properties: When heated strongly, it undergoes a significant increase in viscosity, leading to gelatinization.

[0029] Walnut oil, as used according to the invention, is a high-quality vegetable oil from ripe, sometimes roasted, walnut (Juglans) seeds. It is pale greenish-yellow to straw-yellow in color, relatively thin, has an intense, nutty flavor, and is characterized by a particularly high content of triglycerides of unsaturated fatty acids.

[0030] Owatrol® oil (Owatrol International), as used according to the invention, is a multi-purpose, oil-based product intended for the protection and improvement of the appearance of wood, metal, and other surfaces. It consists mainly of a mixture of aliphatic hydrocarbons, fatty acids, and esters.

[0031] Shellac (also known as chalkboard lacquer, flat lacquer, or gum lacca, gum resin, and lac resin), as used according to the invention, is a resinous substance obtained from the secretions of the lac insect *Kerria lacca* (plant lice, family Kerridae) after it has fed on the leaves of certain plants (hence the occasional name "leaf shellac"). These plants are usually the fig tree (*Ficus religiosa*, *Ficus indica*), the jujube (*Ziziphus jujuba*, *Ziziphus mauritia*), the Malabar lac tree (*Butea frondosa*), the kusum tree (*Schleichera oleosa*), the rain tree (*Samanea saman*), and *Croton lacciferus*. Shellac consists primarily (65-75%) of free and esterified aliphatic and aromatic polyhydroxy acids. The main components are aleuritic acid (up to 32%) and shellolic acid. Since in Since the monomers contain several hydroxyl and carboxyl groups, three-dimensional networks can form, as is typical in thermosets. Other components include dyes (4-8%), bitter substances, and some wax (shellac wax, ceryl cerotinate, ceryl cerotinate, and wax alcohols).

[0032] Casein (from Latin caseus, "cheese"), as used according to the invention, is the protein component of milk that is processed into cheese and does not end up in the whey. It is a mixture of several proteins (αS1-, αS2-, β-, κ-casein). Casein makes up the majority of the proteins in quark (curd cheese) and cheese, which obtain their firm consistency through the coagulation of the casein. Casein is used not only as a foodstuff but also as a binding agent and pharmaceutical excipient.

[0033] Slaked lime, as used according to the invention, is a suspension of calcium hydroxide (Ca(OH)₂, hydrated lime, quicklime) in water. The name slaked lime comes from the very old technique of slaking the lime in a pit after the quicklime had been slaked with excess water. To produce slaked lime, quicklime (i.e., burnt but unslaked lime) is traditionally mixed with two and a half to three times its volume of water. The quicklime reacts with a significant release of heat to form slaked lime (calcium hydroxide or hydrated lime). Designs

[0034] The wood mass composition according to the invention for the 3D printing of wooden objects contains the following components: a) 100 ± 10 % Parts wood fiber / wood flour mixture b) 10 ± 10 % Methylcellulose c) 10 ± 10 % parts guar gum d) 10 ± 10 % Parts oil e) 8 ± 10 % parts alcohol f) 2 ± 10 % Parts shellac g) 300 10 % parts of water h) 6 ± 10 % Parts of casein powder i) 6 ± 10 % parts slaked lime

[0035] There are no particular restrictions regarding the type of wood; for example, fibers and / or flour from softwood and / or hardwood can be used, such as willow, larch, poplar, walnut, birch, oak, or beech. Mixtures of different wood species can also be used. If fibers are used, they can have a length of 1–15 mm and a diameter of at least 1 mm. For wood flour, a diameter of less than 1 mm is preferred (mill grade ≤ 18 mesh). The fiber / flour mixture is not subject to any particular restrictions regarding the ratio and can vary depending on the type of wood and application, e.g., 90 parts by weight of flour (mill grade ≤ 18 mesh) and 10 parts by weight of fibers (1–4 mm).

[0036] The CAS numbers listed below (CAS = Chemical Abstracts Service) are an international standard for naming chemical substances. Each chemical substance registered in the CAS database has a unique CAS number.

[0037] Methylcellulose, CAS No. 9032-42-2, serves as a stabilizer in the invention and can be used in powder form or as a viscous glue (e.g., Tylose® MH 1000 P2 or Tylose® MH 3000 YP4 from Kremer Pigmente GmbH & Co. KG). Source: https: / / www.kremerpigmente.com / elements / resources / products / files / 63610_SHD.pdf

[0038] Guar gum, or guar flour, has CAS number 9000-30-0 and, according to the invention, serves as a stabilizer. It can be used in powder form or as a viscous suspension (e.g., with a commercially available viscosity of 3,500 cps). Guar gum is available, for example, in the food trade.

[0039] Source: https: / / www.chemicalbook.com / ProductChemicalPropertiesCB5253559_E N.htm

[0040] There are no particular restrictions regarding the type of oil used; for example, linseed oil, tung oil, walnut oil, or Owatrol® oil, or mixtures thereof, can be used. According to the invention, the oil serves as a lubricant to prevent the nozzle of the 3D printer (e.g., extruder) from clogging. 100% natural linseed oil has CAS number 8001-26-1 and is available, for example, from Kremer Pigmente GmbH & Co. KG.

[0041] Source: https: / / www.kremer-pigmente.com / elements / resources / products / files / 73054_SHD.pdf

[0042] Shellac has CAS No. 9000-59-3 and is not limited to a specific type for use in the invention; for example, the Lemon1 leaf shellac from Kremer Pigmente GmbH & Co. KG is suitable.

[0043] Source: https: / / www.kremer-pigmente.com / elements / resources / products / files / 60400_SHD.pdf

[0044] Shellac has a positive effect on printing behavior and the printed object (improved drying properties, strength, post-processing). The shellac is dissolved, for example, in 95% alcohol by weight (e.g., methanol, ethanol, propanol), which evaporates quickly and thus supports an initial drying process immediately after the printing material leaves the nozzle.

[0045] Casein, for example, can be obtained from Kremer Pigmente GmbH & Co. KG.

[0046] Slaked lime has the CAS number 1305-62-0 and is available, for example, from Kremer Pigmente GmbH & Co. KG.

[0047] Source: https: / / www.kremer-pigmente.com / elements / resources / products / files / 31800.pdf

[0048] According to the invention, the casein-lime mixture serves as a binder. This "bio" adhesive ensures the robust and durable nature of the printed objects. Furthermore, the lime has an antifungal effect due to the change in pH value.

[0049] The wood mass composition according to the invention can be produced by combining the following in the proportions defined above: (a) Wood fiber-wood flour mixture, methylcellulose, guar gum, oil, alcohol and shellac mixed, e.g. in a planetary mixer, (b) adds water, and then (c) Casein powder and slaked lime are added and the total mass is mixed homogeneously.

[0050] The finished wood mixture can be stored in an airtight container until use.

[0051] Alternatively, the solid components of the wood mass composition according to the invention can be stored and distributed like a cake mix. For example, a wood fiber-wood flour mixture, methylcellulose, and guar gum can be packaged in one bag 1, and casein powder and slaked lime in another bag 2. For use, the oil and shellac dissolved in, for example, 95% by weight alcohol are added to the contents of bag 1 and mixed, for example, in a planetary mixer. Then, the contents of bag 2 and water are added, and the entire mass is mixed homogeneously.

[0052] Furthermore, a method for producing a three-dimensional wooden object is proposed, in which: (A) provides a wood mass composition according to any one of claims 1 to 4 and (B) the wood mass composition is applied layer by layer to a substrate to form the wood object using a 3D printer based on a CAD file containing the geometric design data of the wood object to be printed.

[0053] To produce a three-dimensional wooden object, the wood mass composition according to the invention is applied layer by layer to a substrate using a 3D printer, based on a CAD file containing the geometric design data of the wooden object to be printed. All LDM ("Liquid Deposition Modeling") printers are suitable for 3D printing, e.g., commercially available 3D printers such as the Wasp-Delta or Crane, Scara Elite V1 and 2, or corresponding extrusion attachments on robot arms (e.g., Kuka) (similar to concrete or ceramic applications).

[0054] For example, it can be used with a standard pneumatically driven and motor-controlled extrusion unit. The extrusion nozzles can have a diameter of 4, 6, 8, or 10 mm. The extrusion pressure can be, for example, 0.4–0.6 mPa. The pressure can be adapted to other 3D printing systems, such as continuous or direct-feed systems, if necessary. According to the invention, extrusion does not need to take place at elevated temperatures. If desired or necessary, hot air can be used for improved drying (e.g., three hot air guns mounted on the printer arms, each with a temperature of 300 °C and 700 watts). The drying time depends on the object size. Complete drying with good ventilation is possible in 1 to 3 days. Air ventilation and heat (e.g., 25–35 °C) support the process. "Baking" for approximately 2 hours at, for example, 80–120 °C with circulating air is also possible.

[0055] Post-processing of the printed objects is possible with tools and materials commonly used in woodworking (similar to the wood-based material MDF ("Medium Density Fiberboard"), which consists of pressed wood fibers, glue and additives), for example sanding, rasping, drilling, milling, sawing, oiling, varnishing, gluing, bonding.

[0056] The wood mass composition according to the invention has a multitude of applications, including, for example, furniture making, interior design, trade fair construction, vehicle conversion, interior architecture, architecture, landscape architecture, pavilions, seating landscapes, erosion control, modules and modular elements in an architectural context, house building components, vertical gardens, planting aids, slope stabilization, bank stabilization (also temporarily for plant penetration), dune protection, avalanche protection, terracing, browsing protection for young trees, acoustic panels, interior cladding, decorations, cat / animal furniture, insect hotels, individualized, bird-specific nesting aids, boat building, canoe / kayak hull construction, formwork and mold making.

[0057] The aforementioned elements or modules can be produced in particular using the method or wood composition proposed here. Character description

[0058] The following figures serve only to illustrate the present invention and are not to be interpreted as limiting the scope of the invention as specified in the accompanying claims in any way. Fig. Figure 1 shows a 3D printed body 5 with the wood mass composition according to the invention. Fig. Figure 2 shows a large-format 3D-printed body 5 using the Liquid (or Fluid) Deposition Modelling method with, for example, a 3D printer 6 called WASP-Delta 40-100. Fig. Figure 3 schematically shows an extruder 1 in the center and a hot air blower 2 next to it. Below are a print layer 3 to be produced and the already printed object 4. The thermal treatment during the printing process using the hot air blower 2 is optional. Fig.Figure 4 shows, as an application example, a 3D-printed object 5 in the form of a stool. The finished printed object can be used, for example, for furniture, design, or architectural objects. In the Fig. Figure 4 illustrates a stress test of physical integrity using the body weight of a person sitting on the stool.

[0059] It is clear to those skilled in the technical field of the invention that the representative embodiments and details of the invention described above are intended only to illustrate the present invention, and that various modifications and alterations can be made without thereby departing from the scope of protection of the invention as defined in the attached claims.

Claims

[1] Wood mass composition for 3D printing of wooden objects, containing the following components (proportions by weight): a) 100 ± 10 % Parts wood fiber / wood flour mixture b) 10 ± 10 % Methylcellulose c) 10 ± 10 % parts guar gum d) 10 ± 10 % Parts oil e) 8 ± 10 % parts alcohol f) 2 ± 10 % Parts shellac g) 300 ± 10 % parts of water h) 6 ± 10 % Parts of casein powder i) 6 ± 10 % parts slaked lime [2] Wood mass composition according to claim 1, wherein the wood fiber / wood flour mixture comprises fibers and / or flour of softwood and / or hardwood. [3] Wood composition according to claim 2, wherein the softwood and / or hardwood is selected from willow, larch, poplar, walnut, birch, oak or beech or mixtures thereof. [4] Wood composition according to any one of claims 1 to 3, wherein the oil is selected from linseed oil, tung oil, walnut oil or Owatrol® oil or mixtures thereof. [5] A method for producing a wood mass composition according to any one of claims 1 to 4, wherein the proportions defined in claim 1 are: (a) Mixture of wood fiber and wood flour, methylcellulose, guar gum, oil, alcohol and shellac, (b) adds water, and then (c) Casein powder and slaked lime are added and the total mass is mixed homogeneously. [6] Method for producing a three-dimensional wooden object, in which: (A) provides a wood mass composition according to any one of claims 1 to 4 and (B) the wood mass composition is applied layer by layer to a substrate to form the wood object using a 3D printer based on a CAD file containing the geometric design data of the wood object to be printed. [7] Use of a wood mass composition according to any one of claims 1 to 4 for the production of a three-dimensional wooden object. [8] Use according to claim 7, wherein the three-dimensional wooden objects are elements or modules of the following list: furniture construction, interior design, exhibition stand construction, vehicle conversion, interior architecture, architecture, landscape architecture, pavilions, seating landscapes, erosion control, house components, vertical gardens, planting aids, slope stabilization, bank stabilization, dune protection, avalanche protection, terracing, browsing protection for young trees, acoustic panels, interior cladding, decorations, animal furniture, insect hotels, bird-specific nesting aids, boat building, canoe hull construction, kayak hull construction, formwork, mold making.

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