CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 62/122,231 , filed on October 15, 2014, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention is in the technical field of plastic materials. More specifically, the present invention is in the field of plastic filaments.

BACKGROUND OF THE INVENTION

[0003] Plastic filaments, which are generally defined as threads of plastic, are used to manufacture a wide range of products including, but not limited to, stranded ropes, tooth brush bristles, fabric materials and plastic ties. Plastic filaments are also widely used as feedstocks for three dimensional (3D) printers, and the types of plastics most widely used for this application are typically acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). ABS is a synthetic copolymer made by polymerizing styrene and acrylonitrile in the presence of butadiene. PLA is a synthetic biopolymer that is typically manufactured from renewable resources such as corn starch and sugar cane.

[0004] ABS filaments for 3D printing are generally preferred for printing materials intended to have mechanical uses due to its superior strength, flexibility, machinability and temperature resistance. A significant drawback to ABS is that unpleasant and hazardous odors are produced as it is extruded. It has been shown that ultrafine particulate fumes are produced at a level that is ten times higher when ABS filaments are used in 3D printers than for PLA-based filaments (Stephens et al. 2013. Ultrafine particle emissions from desktop 3D printing. Atmospheric Environment. 79:334-339). PLA filaments are generally available in a wider range of colors and translucencies, which makes them attractive for printing materials intended for display purposes or household uses. However, while PLA meets the ASTM D6400 standard for compostability, which requires that 60% conversion of the plastic's carbon is reduced to carbon dioxide within 6 months, it will only biodegrade quickly if composted in an industrial composting facility configured to heat the material above 60 °C with constant feeding of digestive microbes. PLA does not decompose at an effective rate in simple composting systems.

[0005] While past technologies may be effective to a certain degree in providing biodegradable polymer filaments, it remains desirable to provide improved biodegradable polymer filaments with enhanced biodegradability to address the various requirements and improve the safety profile of such filaments.

SUMMARY OF THE INVENTION

[0006] One aspect of the present invention is a process for manufacturing a biodegradable polymer filament product, the process comprising: a. isolating polyhydroxyalkanoate from a bacterial culture; b. optionally bleaching the polyhydroxyalkanoate; c. dispersing the polyhydroxyalkanoate in a surfactant solution to form a dispersion; d. drying the dispersion to obtain dried polyhydroxyalkanoate particles; e. mixing the polyhydroxyalkanoate with a plurality of components including a toughening agent, a plasticizer, a nucleating agent, an antioxidant and an adhesive; f. extruding the mixture as a filament; and g. winding the filament onto a spool.

[0007] In certain embodiments, the polyhydroxyalkanoate is poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), poly(4-hydroxybutyrate), poly-3-hydroxyhexanoate, poly-3- hydroxyoctanoate, poly-3-hydroxyoctanoatepoly(3-hydroxybutyrate)-co-valerate, poly(3- hydroxynonanoate-co-3-hydroxyheptanoate), poly(3-hydroxynonanoate-co-3- hydroxyheptanoate, poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate), poly(3- hydroxynonanoate-co-3-hydroxyheptanoate-co-3-hydroxynonenoat e-co-3- hydroxyundecenoate, poly(3-hydroxynonanoate-co-3-hydroxyheptanoate-co-3- hydroxynonenoate-co-3-hydroxyundecenoate), poly(3-hydroxynonanoate-co-3- hydroxyheptanoate-co-3-hydroxynonenoate-co-3-hydroxyundeceno ate), poly(3- hydroxbutyrate-co-3-hydroxyvalerate), or poly(3-hydroxbuyrate-co-3-hydroxyhexanoate).

[0008] In certain embodiments, the bacterial culture is of a member strain of any one of the genera Alcaligenes, Bacillus, Clostridium, Corynebacterium, Cupriavidus, Cyanobacterium, Erwinia, Legionella, Methanomonas, Methylobacterium, Methylosinus, Methylocystis, Methylomonas, Methylovibrio, Nitrobacter, Protomonas, Pseudomonas, Ralstonia, Rhizobium, Rhodobacter, Rhodospirillum, Spirillum, Spirulina, Staphylococcus, Vibrio and Wautersia.

[0009] In certain embodiments, the bacterial culture is of a methanotrophic bacterium grown using methanol as a carbon source.

[0010] In certain embodiments, the bacterial culture is of an engineered or non- engineered bacterium.

[0011] In certain embodiments, the bacterial culture is of a member of the genus Methylobacterium.

[0012] In certain embodiments, the bacterial culture is of Methylobacterium extorquens.

[0013] In certain embodiments, the bleaching of the polyhydroxyalkanoate is not optional and is performed using hydrogen peroxide.

[0014] In certain embodiments, the drying step is performed by spray-drying.

[0015] In certain embodiments, the dried polyhydroxyalkanoate particles have an average diameter from about 150 to about 250 micrometers.

[0016] In certain embodiments, the dried polyhydroxyalkanoate particles are subjected to a cross-linking process before step d). [0017] In certain embodiments, the nucleating agent is talc, mica, boron nitride, crystalline nanocellulose, crystalline microcellulose, sodium benzoate, calcium carbonate, silica, an ionomer, a clay, diacetal, titanium dioxide, dibenzylidene sorbitol, benzophenone, diacetal benzoate, lithium benzoate, sodium benzoate, potassium benzoate, thymine or a sodium organophosphate.

[0018] In certain embodiments, the plurality of components further comprises a filler. [0019] In certain embodiments, the filler conducts electricity.

[0020] In certain embodiments, the filler is a carbon nanotube, a carbon fiber, a steel fiber, or carbon black.

[0021] In certain embodiments, the filler is calcium carbonate, lignin, cellulose or rice husk.

[0022] In certain embodiments, the plasticizer is glycerol, tributyl-O-acetylcitrate, glyceryl triacetate, bis(2-ethylhexyl) adipate, acetyltri-n-butyl citrate polyethylene glycol, sorbitol, mannitol or sodium monoleate.

[0023] In certain embodiments, step f) further comprises providing the filament with a coating polymer.

[0024] In certain embodiments, the coating polymer is selected from the group consisting of: paraffin wax, polyvinyl alcohol, ethylene vinyl acetate, polyvinyl acetate, ethylene acrylic acid, ethylene ethyl acrylate, ethylene methacrylate and ethylene methacrylic acid.

[0025] In certain embodiments, the plurality of components further includes a coagent to improve crystallization kinetics.

[0026] In certain embodiments, the coagent is selected from the group consisting of triallyl trimesate, N,N-m-phenylenedimaleimide, trimethylopropane triacrylate, 1 ,2- polybutadiene, neopentylglycol diacrylate, diallyl isophthalate, N-phenylmaleimide and triallyl phosphate. [0027] In certain embodiments, the plurality of components further includes a coloring agent.

[0028] In certain embodiments, the coloring agent is selected from the group consisting of: an organic pigment, an organometallic pigment, a mineral-based pigment, a carbon pigment, a titanium pigment, an azo compound, a quinacridone compound, a phthalocyanine compound, a cadmium pigment, a chromium pigment, a cobalt pigment, a copper pigment, an iron pigment, a clay earth pigment, a titanium pigment, an aluminum pigment, a manganese pigment, an ultramarine pigment, a zinc pigment, a tin pigment, an iron oxide pigment, an antimony pigment, a barium pigment, a biological pigment, a dye, a photochromic pigment, a conductive and liquid crystal polymer pigment, a piezochromic pigment, a goniochromatic pigment, a silver pigment, a diketopyrrolo-pyrrole compound, a benzimidazolone compound, an isoindoline compound, an isoindolinone compound, and a radio-opacifier.

[0029] In certain embodiments, the organic pigment is selected from the group consisting of: alizarin, anthoxanthin, arylide yellow, bilin, bistre, bone char, caput mortuum, carmine, crimson, diarylide pigment, Dragon's blood, Gamboge, Indian yellow, indigo dye, naphthol red, ommochrome, perinone, phthalocyanine Blue BN, phthalocyanine Green G, Pigment Yellow 10, Pigment yellow 139, Pigment Yellow 16, Pigment yellow 185, Pigment Yellow 81 , Pigment yellow 83, quinacridone, Rose madder, Rylene dye, sepia ink and Tyrian purple.

[0030] Another aspect of the present invention is a biodegradable filament for 3D printing, the filament comprising: a. about 50% to about 80% (m/m) polyhydroxyalkanoate; b. about 10% to about 50% (m/m) of a toughening agent; c. about 0.5% to about 30% of a plasticizer; d. about 0.1 % to about 1 % of a nucleating agent; e. about 0.1 % to about 1 % of an antioxidant; and f. about 0.01 % to about 2% of an adhesive.

[0031] In certain embodiments, the filament further comprises about 0.01 % to about 1 % of a coloring agent.

[0032] In certain embodiments, the coloring agent is an organic pigment selected from the group consisting of: alizarin, anthoxanthin, arylide yellow, bilin, bistre, bone char, caput mortuum, carmine, crimson, diarylide pigment, Dragon's blood, Gamboge, Indian yellow, indigo dye, naphthol red, ommochrome, perinone, phthalocyanine Blue BN, phthalocyanine Green G, Pigment Yellow 10, Pigment yellow 139, Pigment Yellow 16, Pigment yellow 185, Pigment Yellow 81 , Pigment yellow 83, quinacridone, Rose madder, Rylene dye, sepia ink and Tyrian purple.

[0033] In certain embodiments, the filament further comprises 0.5% to 20% of a filler. [0034] In certain embodiments, the filler conducts electricity.

[0035] In certain embodiments, the filler is conductive carbon black, a carbon nanotube or a steel fiber.

[0036] In certain embodiments, the filler is calcium carbonate, nanocrystalline cellulose, lignin or rice husk.

[0037] In certain embodiments, the filament further comprises a phosphorescence compound.

[0038] In certain embodiments, the phosphorescence compound is zinc sulfide.

[0039] In certain embodiments, the polyhydroxyalkanoate is poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), poly(4-hydroxybutyrate), poly-3-hydroxyhexanoate, poly-3- hydroxyoctanoate, poly-3-hydroxyoctanoatepoly(3-hydroxybutyrate)-co-valerate, poly(3- hydroxynonanoate-co-3-hydroxyheptanoate), poly(3-hydroxynonanoate-co-3- hydroxyheptanoate, poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate), poly(3- hydroxynonanoate-co-3-hydroxyheptanoate-co-3-hydroxynonenoat e-co-3- hydroxyundecenoate, poly(3-hydroxynonanoate-co-3-hydroxyheptanoate-co-3- hydroxynonenoate-co-3-hydroxyundecenoate), poly(3-hydroxynonanoate-co-3- hydroxyheptanoate-co-3-hydroxynonenoate-co-3-hydroxyundeceno ate), poly(3- hydroxbutyrate-co-3-hydroxyvalerate), or poly(3-hydroxbuyrate-co-3-hydroxyhexanoate).

[0040] In certain embodiments, the polyhydroxyalkanoate is produced from a bacterial culture of a member strain of any one of the genera Alcaligenes, Bacillus, Clostridium, Corynebacterium, Cupriavidus, Cyanobacterium, Erwinia, Legionella, Methanomonas, Methylobacterium, Methylosinus, Methylocystis, Methylomonas, Methylovibrio, Nitrobacter, Protomonas, Pseudomonas, Ralstonia, Rhizobium, Rhodobacter, Rhodospirillum, Spirillum, Spirulina, Staphylococcus, Vibrio and Wautersia.

[0041 ] In certain embodiments, the bacterial culture is of a methanotrophic bacterium grown using methanol as a carbon source.

[0042] In certain embodiments, the bacterial culture is of an engineered or non- engineered bacterium.

[0043] In certain embodiments, the bacterial culture is of a member of the genus Methylobacterium.

[0044] In certain embodiments, the bacterial culture is of Methylobacterium extorquens.

[0045] In certain embodiments, the nucleating agent is talc, mica, boron nitride, crystalline nanocellulose, crystalline microcellulose, sodium benzoate, calcium carbonate, silica, an ionomer, a clay, diacetal, titanium dioxide, dibenzylidene sorbitol, benzophenone, diacetal benzoate, lithium benzoate, sodium benzoate, potassium benzoate, thymine or a sodium organophosphate.

[0046] In certain embodiments, the plasticizer is glycerol, tributyl-O-acetylcitrate, glyceryl triacetate, bis(2-ethylhexyl) adipate, acetyltri-n-butyl citrate polyethylene glycol, sorbitol, mannitol and sodium monoleate.

[0047] In certain embodiments, the strengthening polymer or fiber is starch, chitin, polybutylene adipate terephthalate, polybutylene succinate, bio-based polyethylene, natural rubber, polylactic acid, nanocrystalline cellulose, microcrystalline cellulose, lignin, flax, hemp, bamboo, rice husk, wood fiber, sawdust, pulp, or peanut hulls. [0048] In certain embodiments, the filament further comprises a coagent to improve crystallization kinetics, wherein the coagent is triallyl trimesate, N,N-m- phenylenedimaleimide, trimethylopropane triacrylate, 1 ,2-polybutadiene, neopentylglycol diacrylate, diallyl isophthalate, N-phenylmaleimide or triallyl phosphate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. Similar reference numerals indicate similar components.

Figure 1 is a process diagram for purification of polyhydroxyalkanoate from cell culture of a methanotrophic bacterium.

Figure 2 is a process diagram for manufacture of a biodegradable polymer filament using an extrusion process.

DETAILED DESCRIPTION OF THE INVENTION

Rationale

[0050] A drawback that is common to both ABS and PLA is that both polymers must be processed at a relatively high temperature (210 - 255° C) due to the higher melting and glass transition temperatures for both polymer types, which increases processing cost. In order to avoid warpage of the plastics, which may be induced due to rapid cooling from these high temperatures, 3D printers generally are required to have a heated bed in order to control the cooling rate, which adds to the cost of manufacturing the 3D printer hardware.

[0051] Three dimensional printing can be achieved by techniques such as fused deposition modelling, which use extruded filaments and granular binding methods such as selective laser sintering and selective heat sintering. Polymeric components are typically printed using fused deposition modelling. [0052] In accordance with the invention, embodiments of the filament compositions described herein are used in all three dimensional printing techniques, subject to certain modifications. For example, it is recognized that compositions used in selective laser sintering and selective heat sintering will benefit from pulverization of the polymer composition blend into a fine powder.

[0053] Polyhydroxyalkanoates are biologically degradable polymers which can be accumulated by microorganisms as sources of carbon and energy (Rai, R. and Roy, I. 201 1 . In: A Handbook of Applied Biopolymer Technology: Synthesis Degradation and Applications, Chapter 3, edited by S.K. Sharma and A. Mudhoo, London, Royal Society of Chemistry). Poly(3-hydroxybutyrate) (PHB) and the copolymer poly(3- hydroxybutyrate)-co-valerate (PHB/HV) are the most known and best studied forms of polyhydroxyalkanoate and are classified as "PHB-type polyhydroxyalkanoates." Like PLA, polyhydroxyalkanoates are biopolymers. However, polyhydroxyalkanoates also possess a number of properties that may make them more suitable for source material for 3D printing than PLA. Polyhydroxyalkanoates are typically more UV stable than PLA. Polyhydroxyalkanoates also demonstrate lower permeability to water than PLA, while the higher crystallinity of polyhydroxyalkanoates makes them stronger than PLA. Finally, while the melting temperature for both PHA and PLA is similar, and while both materials are classified as biodegradable and compostable, the low glass transition temperature for polyhydroxyalkanoates (2 °C in the case of polyhydroxybutyrate) means that they can be printed at lower temperature.

Definitions

[0054] As used herein, the term "filament" refers to a thread-like object or fiber formed of a blend of materials including one or more polymers.

[0055] As used herein, the term "plasticizers" (also known as "dispersants") refers to additives that increase the plasticity or fluidity of a material. The dominant applications are for plastics, especially polyvinyl chloride (PVC). The properties of other materials are also improved when blended with plasticizers including concrete, clays, and related products. Plasticizers are common components of films and cables. [0056] The term "Young's modulus," also known as the "tensile modulus" or "elastic modulus," is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the stress (force per unit area) along an axis to the strain (ratio of deformation over initial length) along that axis in the range of stress in which Hooke's law holds. Young's modulus is the most common elastic modulus, sometimes called the modulus of elasticity, but there are other elastic moduli such as the bulk modulus and the shear modulus. Young's modulus is the ratio of stress (which has units of pressure) to strain (which is dimensionless), and so Young's modulus has units of pressure. Its SI unit is therefore the Pascal (Pa or N/m ² or m ^"1 -kg-s ^"2 ). The practical units used are megaPascals (MPa or N/mm ² ) or gigaPascals (GPa or kN/mm ² ). In United States customary units, it is expressed as pounds (force) per square inch (psi). The abbreviation ksi refers to "kips per square inch", or thousands of psi. As examples, polypropylene has a Young's modulus of 1 .5-2 GPa and diamond has a Young's modulus of 1 ,050 - 1210 GPa. Tensile tests measure the force required to break a plastic sample specimen and the extent to which the specimen stretches or elongates to that breaking point. Tensile tests produce stress-strain diagrams used to determine tensile modulus, tensile strength (at yield and at break), tensile strain, elongation and percent elongation at yield, and elongation and percent elongation at break.

[0057] As used herein, the term "impact strength" refers to the ability of a material to absorb energy and plastically deform without fracturing. One definition of material impact strength is the amount of energy per unit volume that a material can absorb before rupturing. It is also defined as a material's resistance to fracture when stressed. Impact strength is measured in units of joule per cubic meter (J-rrr ³ ) in the SI system and inch- pound-force per cubic inch (in- Ibf ^■ in ^-3 ) in US customary units. Izod impact testing is an ASTM standard method of determining the impact resistance of materials. An arm held at a specific height (constant potential energy) is released. The arm hits the sample and the specimen being tested either breaks or the weight rests on the specimen. From the energy absorbed by the sample, its impact energy is determined.

[0058] As used herein, the term "toughness" refers to the ability of a material to absorb energy and plastically deform without fracturing. One definition of material toughness is the amount of energy per unit volume that a material can absorb before rupturing. It is also defined as a material's resistance to fracture when stressed.

[0059] As used herein, the term "glass transition" refers to the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or rubber-like state. An amorphous solid that exhibits a glass transition is called a glass.

[0060] As used herein, the term "crystallinity" refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion.

[0061 ] As used herein, the term "strain hardening" (also known as "work hardening and "cold working" refers to the strengthening of a material by plastic deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material.

[0062] As used herein, the term "extrusion" refers to a process for generation of objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross- section. A polymer extrusion process involves heating to melt the polymer. Typically a single or twin screw system is used to convey molten plastic material through the extruder. Apart from melting and conveying extruder also mixes two or more plastics or other materials. The material exits the extruder at the die and it takes shape of the die. Molten plastics leave the die at temperatures at or above the melting temperature of the material. The object emerging from the extruder is typically passed through a water tank to cool it down before it is cut into pellets or wound upon a spool. The purpose of the die is to reorient and guide the flow of polymer melt from a single round output from the extruder to a thin, flat planar flow. It provides a constant, uniform flow across the entire cross sectional area of the die. Cooling is typically by pulling through a set of cooling rolls.

[0063] As used herein, the term "spray drying" refers to a method of producing a dry powder from a liquid or slurry by rapidly drying with a hot gas. This method is used for drying of many thermally-sensitive materials such as foods and pharmaceuticals. A consistent particle size distribution is a reason for spray drying of industrial products such as catalysts. Air is the heated drying medium; however, if the liquid is a flammable solvent such as ethanol or the product is oxygen-sensitive then nitrogen is used. All spray dryers use some type of atomizer or spray nozzle to disperse the liquid or slurry into a controlled drop size spray. The most common of these are rotary disks and single- fluid high pressure swirl nozzles. Atomizer wheels are known to provide broader particle size distribution, but both methods allow for consistent distribution of particle size. Alternatively, for some applications, two-fluid or ultrasonic nozzles are used. Depending on the process needs, drop sizes from 10 to 500 μηι can be achieved with the appropriate choices. The most common applications are in the 100 to 200 μηι diameter range. The dry powder is often free-flowing. The most common spray dryers are called "single effect" spray dryers as there is only one stream of drying air at the top of the drying chamber. In most cases the air is blown in co-current of the sprayed liquid. The powders obtained with such type of dryers are fine with a lot of dusts and a poor flowability. In order to reduce dust and increase the flowability of the powders, a new generation of spray dryers known as "multiple effect" spray dryers have been developed. Instead of drying the liquid in one stage, the drying is done in two steps: one at the top (as per single effect) and one for an integrated static bed at the bottom of the chamber. The integration of this fluidized bed allows, by fluidizing the powder inside a humid atmosphere, to agglomerate the fine particles and to obtain granules having commonly a medium particle size within a range of 100 to 300 μηι. Because of this large particle size, these powders are free-flowing. The fine powders generated by the first stage drying can be recycled in continuous flow either at the top of the chamber (around the sprayed liquid) or at the bottom inside the integrated fluidized bed. The drying of the powder can be finalized on an external vibrating fluidized bed. The hot drying gas is passed as a co- current or counter-current flow to the atomizer direction. The co-current flow enables the particles to have a lower residence time within the system and the particle separator (typically a cyclone device) operates more efficiently. The counter-current flow method enables a greater residence time of the particles in the chamber and usually is paired with a fluidized bed system. Alternatives to spray dryers include freeze dryers, drum dryers, and pulse combustion dryers. [0064] As used herein, the term "nucleating agent" refers to any agent used to modify the rate of crystallization of a polymer.

[0065] As used herein, the term "copolymer" refers to a polymer chain formed of two different types of monomers joined to each other.

[0066] As used herein, the term "biodegradable" and the related term "biodegradability" refer to the susceptibility of a given material to be decomposed by bacteria or other organisms. A Micro-Oxymax Respirometer System (Columbus Instruments Inc., Columbus, OH, USA) is appropriate for testing of biodegradation of bioactive polyhydroxyalkanoate filaments.

[0067] As used herein, the term "medium chain length polyhydroxyalkanoate" refers to a polyhydroxyalkanoate chain having 6 to 14 carbon atoms. As used herein the term "short chain length polyhydroxyalkanoate" refers to a polyhydroxyalkanoate chain having 2 to 5 carbon atoms.

[0068] As used herein, the terms "electric conductivity" and the related terms "electrically conductive" and "electrically conducting" refer to the ability of a material to conduct an electric current. Electric conductivity of polymer sample can be measured using a standard four point measurement process. The current source is connected to both ends of the sample. The voltmeter leads are placed a known distance apart. The resistivity is calculated from the cross- sectional area of the sample and distance between the voltage leads as follows: where: p- Resistivity in Ω m

V - Applied voltage (V)

I - Measured current (A)

A - Cross sectional area of sample (W x t) in cm ² L - Length of distance to voltmeter in cm

[0069] As used herein, the term "polymer morphology" refers to the arrangement and microscale ordering of polymer chains. Morphology of polymer blends involves measurements of dispersion of a dispersed phase or fillers into a polymer matrix. Blend morphology has a substantial effect on mechanical properties and is an important property of polymer blends and composites. Microscopic techniques such as transition electron microscopy and scanning electron microscopy are used to investigate polymer morphology.

[0070] A number of possible alternative features are introduced during the course of this description. It is to be understood that, according to the knowledge and judgment of persons skilled in the art, such alternative features may be substituted in various combinations to arrive at different embodiments of the present invention.

Examples

Example 1 : Process of Extraction of Polyhvdroxyalkanoate from Microbial Cell Culture

[0071] Methylotrophic bacteria are capable of utilizing simple one carbon substrates, such as methanol, as their sole carbon and energy source. Methanol is a relatively inexpensive substrate, and has the added advantages of high solubility in water and low toxicity. Therefore, bacteria that can utilize methanol are of interest for a variety of applications involving methanol as a biofeedstock, including the biological production of fine chemicals and industrially important proteins. In certain embodiments of the present invention, the polyhydroxyalkanoates used for production of the biodegradable filaments are produced by non-engineered strains of methylotrophic bacteria, such as bacteria from the genus Methylobacterium. Methylobacterium extorquens strain AM1 is a non- engineered representative strain capable of overproduction of polyhydroxyalkanoates in its native form. Other native or engineered strains deemed to be effective at overproduction of polyhydroxyalkanoates may be used in alternative embodiments.

[0072] In one example embodiment of the inventive process, illustrated in Figure 1 , the polyhydroxyalkanoates used in production of biodegradable filaments are produced by high density fermentation of a polyhydroxyalkanoate-producing microbial culture 10. The skilled person will understand that the treatment steps described below will include water washing steps at between the steps described below, to remove reagents from the cells and the desired polyhydroxyalkanoate material. The skilled person can determine the extent of water washing needed without undue experimentation and thus, specific water washing steps are not described in detail.

[0073] The culture 10 is centrifuged to separate the cells from the culture medium, followed by preparation of a suspension of the cells in water 12. In this particular embodiment, the suspended and washed cell mixture has an optical density between about 90 to about 1 10. The cells are then homogenized by using a mechanical homogenizer to produce a cell homogenate 14. Cellular debris 16 is discarded. In this particular embodiment, the homogenization is conducted at a pressure of 800 bar, and the cell suspension is transferred through the homogenizer. In certain embodiments, this process is repeated at least four times. Conventional cell disruption processes such as mixing with supercritical fluids technology, sonication or enzyme lysis techniques can be used to homogenize the cells. The recovery of polyhydroxyalkanoates from the lysed cells can be conducted via organic solvents such as chloroform, dichloroethane, methylene chloride or cyclic carbonates like ethylene and propylene carbonates. Supercritical fluid technology also has the potential for use in disruption of microbial cells as well as extraction of intracellular components including co-products, and purification of polyhydroxyalkanoates.

[0074] The process continues with centrifugation of the homogenate to produce a crude polyhydroxyalkanoate pellet 18 and washing the pellet in water and then a solvent to produce a water and solvent washed mass of polyhydroxyalkanoate 20. This step removes lipids 22 from the crude material. In certain embodiments of the process, marketable lipid products 24 are purified from the lipids 22. In certain embodiments, the solvent system is composed of methanol, acetone and water (4:2:1 ). Organic solvents, such as chloroform, dichloroethane or methylene chloride, or cyclic carbonates, such as ethylene and propylene carbonates, can also be used to wash the polyhydroxyalkanoate. The solvent-washed polyhydroxyalkanoate 20 is then centrifuged to separate it from the solvent and solvent-washed polyhydroxyalkanoate 20 is then dispersed in water at a concentration of approximately 10% (w/w), followed by heating to about 80 °C, under constant agitation. [0075] The solvent washed polyhydroxyalkanoate product 20 is then bleached. In the present embodiment, hydrogen peroxide is used as the bleaching agent and is added to the heated solvent-washed polyhydroxyalkanoate 20 at a concentration of 3% (w/w) of the dispersion. The temperature of the dispersion is maintained at 80 °C for 3 hours to achieve complete bleaching of the polyhydroxyalkanoate and the bleached polyhydroxyalkanoate 26 is then heated to about 100 °C under constant agitation. The next step of the process is acid treatment. Hydrochloric acid is added to the dispersion of bleached polyhydroxyalkanoate 26 to achieve a concentration of 0.1 N HCI. The temperature of the dispersion is maintained at 100°C for at least 1 hour. This is followed by cooling the dispersion to room temperature, subsequent centrifugation and water washing to remove residual acid. The result of this step is acid-treated polyhydroxyalkanoate 28.

[0076] The acid-treated polyhydroxyalkanoate is then dispersed, preferably at 10% (w/w) in a surfactant solution. In this particular embodiment, the surfactant solution is a 2.5% (w/w) sodium dodecyl sulfate solution which is heated to 40 °C under agitation. The temperature is maintained at 40 °C for at least 1 hour. The resulting surfactant-treated polyhydroxyalkanoate 30 is washed and dried. In this particular embodiment, a spray dryer with an inlet temperature of 175-185 °C and an outlet temperature of 95-1 10°C is used to prepare dry polyhydroxyalkanoate powder 32 which is suitable as starting material for production of the biodegradable filament of the present invention.

Example 2: Formulation of Polymer Blends

[0077] This example describes the polymer blends and components thereof used in the manufacture of the biodegradable filaments of the present invention. The classes of components of the polymer blends described hereinbelow provide the biodegradable filaments with characteristics that support various embodiments for use in various applications. The skilled person will understand that certain components of the polymer blends may fulfill more than one of the functions described hereinbelow. The skilled person has the knowledge to identify certain components that have properties of more than one of the general categories outlined hereinbelow. For example, the skilled person will recognize that, in certain embodiments, nanocrystalline cellulose may function both as a natural strengthening fiber and a nucleating agent. Certain embodiments include bio-based components to enhance the biodegradability of the polymer blend.

[0078] Advantageously, various embodiments of the biodegradable filament are characterized for mechanical properties including Young's modulus, tensile stress, tensile strain and impact strength, as well as thermal properties including glass transition temperature, melting temperature, crystallization temperature, total crystallinity, thermal stability, melt viscosity and strain hardening. Blend properties such as filler dispersion, blend morphology, and electrical conductivity are also characterized.

[0079] Exemplary embodiments of the biodegradable filaments of the invention are compostable in simple composting systems, have specific heat between about 1400- 1600 J/Kg- K (vs 1800 J/Kg-K for PLA filaments) and thermal conductivity of 0.178 W/m-K (vs 0.13 W/m-K for PLA filaments)making them appropriate for three dimensional printing with lower energy requirements. These filament embodiments also have low glass transition temperatures of about 0-5 °C, which allow them to be processed at lower temperatures. At room temperature, these blends are above the glass transition temperature and thus movement of the polymer chains is facilitated. The amorphous phase of the polymers in the filaments is rubbery at room temperature and this makes the filaments ductile.

[0080] Various compositions meet specific application requirements. Compositions containing lower amount of plasticizers (10-20 weight %) would have higher Young's modulus and tensile strength. Formulations containing up to 20% by weight of Plasticizers remain in the form of free flowing powder and do not clog the extruder feeder. Compositions containing higher plasticizer content (30-40 weight %) are more ductile and will have higher elongation. Higher levels of plasticizers will reduce crystallinity of polyhydroxybutyrate yielding lower Young's modulus and tensile strength.

[0081 ] Formulations containing one or more coagents are expected to have improved crystallinity, melt viscosity and strain hardening properties. Coagents react with polymers and form long chain branches that provide improved melt strength. Coagents produce highly cross-linked particles which give a nucleating effect which results in improved crystallization kinetics. [0082] Compositions with conducting fillers expected to have enhanced electrical properties. Conducting networks formed by fillers determines the conductivity level.

[0083] Polyhydroxyalkanoates - The main component of the bioactive filament compositions of the present invention is provided by one or more polyhydroxyalkanoates. In certain embodiments, the polyhydroxyalkanoate is poly(3- hydroxybutyrate) or the copolymer poly(3-hydroxybutyrate)-co-valerate or a combination thereof. In other embodiments, the polyhydroxyalkanoate is any one of the following: poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), poly(4-hydroxybutyrate), poly-3- hydroxyhexanoate, poly-3-hydroxyoctanoate, poly-3-hydroxyoctanoatepoly(3- hydroxybutyrate)-co-valerate, poly(3-hydroxynonanoate-co-3-hydroxyheptanoate), poly(3-hydroxynonanoate-co-3-hydroxyheptanoate, poly(3-hydroxyoctanoate-co-3- hydroxyhexanoate), poly(3-hydroxynonanoate-co-3-hydroxyheptanoate-co-3- hydroxynonenoate-co-3-hydroxyundecenoate, poly(3-hydroxynonanoate-co-3- hydroxyheptanoate-co-3-hydroxynonenoate-co-3-hydroxyundeceno ate), poly(3- hydroxynonanoate-co-3-hydroxyheptanoate-co-3-hydroxynonenoat e-co-3- hydroxyundecenoate), poly(3-hydroxbutyrate-co-3-hydroxyvalerate), or poly(3- hydroxbuyrate-co-3-hydroxyhexanoate). In certain embodiments, these polyhydroxyalkanoates are produced by the methanotrophic bacterium Methylobacterium extorquens and purified according to the process described in Example 1 and generally illustrated in Figure 1 . Other bacteria may produce different polyhydroxyalkanoate polymers including short chain length, medium chain length and hybrid chain lengths. These other bacteria are members of the genera Alcaligenes, Bacillus, Clostridium, Corynebacterium, Cupriavidus, Cyanobacterium, Erwinia, Legionella, Methanomonas, Methylobacterium, Methylosinus, Methylocystis, Methylomonas, Methylovibrio, Nitrobacter, Protomonas, Pseudomonas, Ralstonia, Rhizobium, Rhodobacter, Rhodospirillum, Spirillum, Spirulina, Staphylococcus, Vibrio and Wautersia. (see for example, Koller et al., Biotechnological Polymer Synthesis, Food Technol. Biotechnol. 48 (3) 255-269 (2010), incorporated herein by reference in entirety). In other embodiments, recombinant strains of bacteria such as Escherichia coli may be engineered to over-produce polyhydroxyalkanoates. Production of polyhydroxyalkanoates by any of these bacteria are within the scope of the invention. [0084] Plasticizers - Incorporating plasticizers into the polyhydroxyalkanoate polymer blend is beneficial, as they function to decrease the melting temperature of the polymer blend. This will allow 3D printing to be achieved at lower temperatures, saving significant energy resources and inhibiting degradation of the material and the deterioration of properties such as the molecular weight of the material. Examples of plasticizers which may be used for this purpose include glycerol, tributyl-O-acetylcitrate, glyceryl triacetate, bis(2-ethylhexyl) adipate, acetyl-tri-n-butyl citrate polyethylene glycol, sorbitol, mannitol and sodium monoleate. A further benefit of incorporating plasticizers is that the polymer blends have lower crystallinity and glass transition temperature, which increases ductility. Addition of a plasticizer enhances the material flow. A high flow material yields faster printing and facilitates cleaning of the printer nozzle. Filament formulations may be produced with a plasticizer content of about 0.5-30% (w/w) to produce a filament material with a high Young's modulus and high tensile strength. For other applications, the plasticizer content can also be increased up to about 30-40% (w/w), to produce a more ductile and more flexible filament material.

[0085] Adhesives - In certain embodiments, adhesives are incorporated into the filament formulations in order to improve adhesion properties and allow the use of the filament in dual nozzle printers configured for production of multicolored items. Attachment of first layer of polymer to a three dimensional printer platform is very crucial in order for an object to be successfully produced by a 3D printer. Typically, masking tape is used on 3D printer beds to achieve polymer attachment; however, the incorporation of an adhesive such as epoxy-based adhesives or functionalized polymers to improve the adhesive properties of the filament formulation provide a means for bonding of the polymer to the printer platform. Formulations containing an adhesive will also improve layer bonding of 3D printed components. This provides the advantage of eliminating the use of masking tape and other adhesives. Other examples of adhesives appropriate for inclusion in certain embodiments of the invention include, but are not limited to, polyurethanes, silicones, acrylates, Polyvinyl acetate, and polyimides.

[0086] Strengthening Polymers - One or more strengthening polymers (which are also be known as "toughening agents" or "impact modifiers") may also be blended with polyhydroxyalkanoates to modulate the properties of the filament by increasing its impact strength. In some embodiments, these strengthening polymers are derived from biological sources and are biodegradable. Examples of strengthening polymers that may be used in embodiments of the filament include starch, chitin, poly(butylene adipate co- terephthalate), polybutyrate adipate terephthalate, polybutylene succinate, bio-based polyethylene, natural rubber and polylactic acid. Synthetically-derived polymers may also be used, examples of which are polycaprolactone, polyamides, polyimides, polyethylene, polypropylene, polycarbonate, polyolefin, polyesters, polyvinyl alcohol and polyvinyl acetate and elastomers such as ethylene styrene, butylene styrene, and polyethylene octene. A blend containing 20-30% strengthening polymers as impact modifiers can produce a material with high impact strength.

[0087] Blends containing 20-30% by weight of impact modifiers will provide the filament with higher impact strength. Impact modifiers are dispersed in the polyhydroxybutyrate matrix and will absorb energy to prevent brittle failure. Compositions containing natural fibers will provide improved Young's modulus and tensile strength. Natural fibers will acts as reinforcing agents in polyhydroxybutyrate and they can also act as nucleating agents. Filament compositions containing about 20% by weight of an impact modifier and about 20% by weight of natural fibers provide balanced properties with sufficient elongation and strength and Young's modulus. Impact modifiers will improve the toughness at the cost of Young's modulus but addition of natural fibers can reverse this effect.

[0088] Toughening agents or "impact modifiers" are included in the formulations of the invention to compensate for the brittleness of polyhydroxyalkanoates and to improve ductility, toughness and tensile strain of the formulations. In the embodiments described herein, the toughening agents provide elasticity. Polybutyrate adipate terephthalate is a biodegradable elastomeric material with elongation greater than 500%. Polybutylene succinate is another promising candidate which is elastic and biodegradable. Examples of other toughening agents are starch, bio based polyethylene, natural rubber, polylactic acid and synthetic polymer such as polyamides, polyimides, polycarbonate, polyolefin, polyesters and elastomers such as styrene ethylene butylene styrene, polyethylene- octene elastomer. Polybutyrate adipate terephthalate mixes well with polyhydroxybutyrate and has demonstrated good compatibility with polyhydroxybutyrate. [0089] Natural Fibers - Further improvement to the filament properties may be achieved by incorporating natural fibers into the polymer blend as reinforcing agents. Examples of such natural fibers include, but are not limited to: nanocrystalline cellulose, microcrystalline cellulose, cellulose fibers, cellulose filaments lignin, flax, hemp, bamboo and rice husk. Incorporation of any of these materials will improve the Young's modulus and tensile strength of the material while also accelerating biodegradation. Natural fibers may also be functionalized in order to increase their interaction with the polymer. Composite filaments that include natural fibers offer improved strength, dimensional stability and provide fine surface texture which hides printing layers. This gives a superior aesthetic appearance to printed objects and allow for the introduction of different shades of color to the object by using different temperature profiles. Natural fibers may also be functionalized in order to increase their interaction with the polymer. Compatibilizers may also be added in order to improve polymer-fiber adhesion. Nanocrystalline cellulose can be modified through reactions including sulfonation, oxidation, cationization or grafting via acid chloride, acid anhydride and silylation. Compatibilizers may also be added in order to improve the polymer-fiber adhesion. Crystalline nanocellulose fibers may also be modified through reactions including sulfonation, oxidation, cationization, or through grafting via acid chloride, acid anhydride and silylation. A composition of 10% strengthening polymer as an impact modifier and 10% natural fibers can be used to produce a polymer blend with balanced properties of flexibility and strength. Impact modifiers reduce the brittleness but lower the modulus of the polyhydroxyalkanoates, while natural fibers or other reinforcing agents increase the modulus of the composition.

[0090] Nucleating Agents - Nucleating agents may be added to the polymer blend to enhance the crystallization of the polyhydroxyalkanoate base material. The addition of nucleating agents increases the crystallization rate, which allows optimal properties of the blend to be achieved in minimal time. Nucleating agents such as talc, mica, boron nitride, natural fibers including nanocrystalline cellulose and microcrystalline cellulose, sodium benzoate, calcium carbonate, silica, ionomers, clays, diacetal, titanium dioxide, various sorbitol derivatives such as dibenzylidene sorbitol, benzophenone, diacetal benzoate, lithium benzoate, sodium benzoate, potassium benzoate, thymine and the sodium salt of organophosphates may be used for this function. [0091 ] Coagents - In certain embodiments, coagents are added to the filament compositions to improve the crystallization kinetics of polyhydroxyalkanoates. In one embodiment, the reactive extrusion technique may be used to modify the properties of polyhydroxyalkanoates. Initiators such as peroxides may be used at controlled processing temperature so as to induce decomposition of peroxides to produce free radicals. Unstable free radicals will remove hydrogen from the polyhydroxyalkanoate to produce additional free radicals. Coagents that have multiple functional groups will react with free radicals to form a branched structure, thus forming cross-linked, coagent-rich micron sized particles. Examples of coagents that may be used for this purpose are acrylic, styrenic, malemido, vinylic or allylic compounds such as triallyl trimestate, N,N- m-phenylenedimalemide, timethylpropane triacrylate, 1 ,2-polybutadiene, neopentylglycol diacrylate, diallylisophthlate, N-phenylmalemide and triallyl phosphate. These coagent particles will act as nucleating agents to enhance the crystallization rate of the polyhydroxyalkanoates and eliminate the requirement for incorporating a nucleating agent into the polymer blend, preventing the deterioration of polymer properties such as ductility that are typically caused by adding nucleating agents. Another advantage of using the reactive extrusion technique is that it will substantially improve the melt strength of the polyhydroxyalkanoates enabling their use in applications involving stretching of polymer melt such as thermoforming, film blowing and blow molding.

[0092] In order to modulate the molecular weight, crystallization properties and strain hardening, chain extenders may also be incorporated. The use of a reactive extrusion approach is preferable as it eliminates the requirement for nucleating agents. Coagent modification improves the crystallization rate and also prevents the deterioration of the polymer properties such as ductility that is caused by the addition of nucleating agents.

[0093] Fillers - Fillers are particulate materials added to polymers in order to improve the physical properties and/or to reduce the cost of the composite. They can be classified according to their source, function, composition, and/or morphology. No single classification scheme is entirely adequate because of the overlap and ambiguity of these categories. The chemical composition and its effect on composite physical properties typically provides a basis for classifying fillers into three broad categories: nonreinforcing or degrading, semi-reinforcing or extending, and reinforcing fillers. The use of fillers in many commercial polymers is for the enhancement in stiffness, strength, dimensional stability, toughness, heat distortion temperature, color, damping, impermeability, and cost reduction, although not all of these desirable features are found in any single filled polymer. Improvements in composite physical properties is directly related to particle size, whereby the smaller particulate fillers impart greater reinforcement. Particle-size distribution and particle shape also have significant effects on composite reinforcement. Filler structure ranges from precise geometrical forms, such as spheres, hexagonal plates, or short fibers, to irregular masses. A particle with a high aspect ratio has higher reinforcement than a more spherical one. Fillers having a broad particle-size distribution have better packing in the polymer matrix and provide lower viscosity than that provided by an equal volume of the filler with a narrow particle-size distribution. The properties of particulate-filled polymers are determined by the properties of the components, by the shape of the filler phase, by the morphology of the system, and by the polymer-filler interfacial interactions. In certain embodiments, the fillers are biodegradable biological materials.

[0094] Coating Polymers - In some embodiments, the filament is coated with a coating polymer in order to provide a superior surface finish. Advantageously, the coating polymer had a low coefficient of friction, which improves flow and reduces the amount of force required to extrude the polymer. This facilitates unwinding of the filament from its spool and improves the look and feel of 3D-printed items. Additional polymer coatings can be applied on filament for various purposes. Polymer coatings can provide customized surface finishes to meet user requirements. It can provide a glossy surface or matte surface finish. Examples of polymer coatings include, but are not limited to paraffin wax, polyvinyl alcohol, ethylene vinyl acetate, polyvinyl acetate, ethylene acrylic acid, ethylene ethyl acrylate, ethylene methacrylate and ethylene methacrylic acid. In certain embodiments, an adhesive is provided between the blended formulation and the coating polymer to improve adhesion between the blended formulation and the coating polymer. In certain embodiments coating can be applied by the melt extrusion process as shown in Figure 2. In certain embodiments low molecular weight polymer or plasticizers can be compounded in a filament formulation, these materials are non- compatible with polyhydroxyalkanoates and can migrate to the surface of the filament. This can provide a lubrication effect and reduce friction while the filament reaches the print head and also during unwinding from the 3D printing spool. This is particularly important in industrial 3D printers where the filament travels over a long distance. Specific low molecular weight polymers or plasticizers that migrate to the surface provide improved layer bonding.

[0095] In certain embodiments, the filament is a conductive filament and the coating is an electrostatic coating, such as the electrostatic coatings used in automotive painting. Electrostatic coatings provide friction reduction, non-stick surfaces, squeak reduction, release, corrosion, abrasion and wear resistance, conductivity, and shielding.

In certain embodiments 3D printing of conductive filaments is performed and the printed components are painted using an electrostatic painting technique.

[0096] Coloring Agents - In certain embodiments, the filament is provided with one or more coloring agents or combinations thereof to provide diverse colors and improve its decorative appearance. Coloring agents are provided by dyes, pigments or any substance that will impart a color. Examples include, but are not limited to: organic pigments, organometallic pigments, mineral-based pigments, carbon pigments, titanium pigments, azo compounds, quinacridone compounds, phthalocyanine compounds, cadmium pigments, chromium pigments, cobalt pigments, copper pigments, iron pigments, clay earth pigments, titanium pigments, aluminum pigments, manganese pigments, ultramarine pigments, zinc pigments, tin pigments, iron oxide pigments, antimony pigments, barium pigments, biological pigments, dyes, photochromic pigments, conductive and liquid crystal polymer pigments, piezochromic pigments, goniochromatic pigments, silver pigments, diketopyrrolo-pyrrole compounds, benzimidazolone compounds, isoindoline compounds, isoindolinone compounds, and radio-opacifiers.

[0097] Examples of organic pigments include, but are not limited to: alizarin, anthoxanthin, arylide yellow, bilin, bistre, bone char, caput mortuum, carmine, crimson, diarylide pigment, Dragon's blood, Gamboge, Indian yellow, indigo dye, naphthol red, ommochrome, perinone, phthalocyanine Blue BN, phthalocyanine Green G, Pigment Yellow 10, Pigment yellow 139, Pigment Yellow 16, Pigment yellow 185, Pigment Yellow 81 , Pigment yellow 83, quinacridone, Rose madder, Rylene dye, sepia ink and Tyrian purple. [0098] Antioxidants - Antioxidants are used in formulations of certain embodiments of the invention to prevent thermal degradation of the polyhydroxyalkanoate during processing and to prevent oxidation during the lifetime of the filament as well as three- dimensional printed objects formed from the filament. One preferred antioxidant is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate). Other examples include, but are not limited to hindered amines, hindered phenol, phosphites and sulfur based antioxidants.

Example 3: Extrusion Process

[0099] In this example embodiment, the filament is manufactured using a twin-screw extruder constructed of customizable parts to provide a structure for optimal blending of formulation components prior to extrusion at the die of the extruder. The segmental design provides the ability to change the screw and barrel design in segments known as "zones." The screws are formed from a number of screw elements. The length of screw is selected according to the blending requirements of a particular application.

[0100] In one particular example embodiment shown in Figure 2, the extruder 100 has a screw 100 cm long (not shown) which is formed of segments of 10 cm. Likewise, the barrel 102 has 10 segments, each 10 cm each in length, which form a barrel with a total of 10 zones (numbered 1 -10 in Figure 2). Zone 1 has the main feeder 104 attached thereto, for feeding of a mixture including the polyhydroxybutyrate, the toughening agent, the nucleating agent and the adhesive. Zone 4 is provided with a liquid feeder 106 for feeding of the plasticizer. Zone 6 is provided with a side feeder 108 for feeding of the reinforcing materials, which, in some embodiments is a natural fiber such as such as microcrystalline cellulose or nanocrystalline cellulose, lignin, flax, hemp, bamboo, cellulose fibers, cellulose filaments, rice husk, wood fibers, and sawdust. Sawdust can be obtained from pulp, peanut hulls, and bamboo are reported as reinforcement in wood composite formulations. Wood fibers separated from aspen, beech, and birch have also been reported to reinforce polymer composites. The downstream feeding of the natural fiber minimizes fiber attrition and maintains the aspect ratio of the fibers. Therefore, the pre-mixed feed is first mixed with the plasticizer in Zone 4 and then the reinforcing materials in Zone 6. In certain alternative embodiments, the reinforcing material is fed at one of the further downstream zones. The mixture emerges from the die 110 as a filament F which is cooled in a water cooling bath 112, and dried with an air blade or air gun dryer 114. In this particular embodiment, the filament F is provided with a coating polymer P emerging from a coating extruder 116 before it is wound on a spool 118. In alternative embodiments, the filament is cooled in air rather than in a water bath if it is deemed that water drying is not advantageous. In certain embodiments, the die used to form the filament F has an opening diameter of 1 .75 mm or 3 mm. The spools may be of various sizes, for example spools configured to hold spooled filament masses of 0.25 kg, 0.5 kg, 0.75 kg, 1 kg, 2 kg, 5 kg, 10 kg, 25 kg, 50 kg to 100 kg.

[0101] This embodiment of the process is projected to produce a filament with sufficient rigidity to maintain consistent roundness to preserve proper functioning within the 3D printer. The filament is projected to retain a uniform diameter over its length, which ensures accurate 3D printing. In certain embodiments, the branching introduced by coagents in the formulation enhances the rigidity. Controlled crosslinking is also projected to provide additional strength to the filament.

[0102] In the present example embodiment, the blend components of the main feed mixture are individually dried in a hot air oven, vacuum oven or dehumidifier at 100 °C for a minimum of 3 hours or at 60 °C for overnight followed by weighing and dry mixing in a batch mixer or tumbler, prior to further compounding in the extruder 100.

[0103] Processing parameters including screw design and screw speed particularly influence the dispersion and distribution of natural fibers in polymer. In certain embodiments, the screw design has two sets of kneading blocks to avoid breaking fibers and at least four mixing elements are incorporated to produce intense shear to achieve homogenous mixing.

[0104] In certain embodiments, reverse elements between the forward conveying elements are used to improve mixing without generating high shear. The specific screw design produces specific geometry of natural fibers in a polymer.

[0105] In one specific embodiment, the following conditions are employed: Screw diameter: 25 mm, L/D: 40, Temperatures: Zone 1 - 100°C; Zone 2 - 160 °C; Zone 3 - 170 °C; Zone 4 - 175°C; Zone 5 - 180 °C; Zone 6 - 180 °C; Zone 7 - 175°C; Zone 8 - 170 °C; Zone 9 - 165°C; Zone 10 - 160 °C; and Die - 160°C. The screw speed is 100 rpm.

[0106] In certain embodiments, after extrusion, the molten plastic exiting the die is passed through a water cooling bath. The filament is then wound onto a spool.

[0107] In alternative embodiments, a polymer coating is applied while the filament is hot.

Example 4: Flexible Filament

[0108] The present example describes one embodiment of a flexible filament. This formulation provides sufficient ductility required for general purpose filaments that can be used to print any household or industrial functional component and provide printing material for the three-dimensional printing hobbyist community.

[0109] The target properties for one embodiment of a flexible filament are: tensile strain: 25-100%; tensile strength: 30-50 MPa; Young's modulus: 200- 500 MPa; and Izod impact strength: 10-30 KJ/m ²

[0110] Ranges of components for this polymer filament embodiment are provided in Table 1 below.

Table 1 : Flexible Filament Formulation

Example 5: High Strength Filament

[0111] The filament of this example has a composition providing high strength for three- dimensionally printed items such as tools and reinforcing members. Nanocrystalline cellulose used in composition provides outstanding strength in a low concentration range. Calcium carbonate reduces the overall cost of the formulation while maintaining or improving the functional performance of filament. The target properties for this particular embodiment of the high strength filament are: tensile strain: 10-50%; tensile strength: 50-100 MPa; Young's modulus: 500-1000 MPa; and Izod impact strength: 5-20 KJ/m ² .

Table 2: High Strength Filament Composition

Example 6: Wood Composite Filament [0112] Wood composite formulations provide fine grainy surface finishes and textures similar to wood. Lignin or rice husk acts as a multipurpose filler, offering wood-like appearance, lowering the cost of formulation, providing dimensional stability and improving the crystallization behavior of the base polymer. Wood fibers and sawdust are also used as a multipurpose filler. Sawdust as particle fillers obtained from pulp, peanut hulls, and bamboo are used in reinforcement in wood composite formulations. Wood fibers separated from aspen, beech, and birch have also been reported to reinforce polymer composites and are applicable in certain embodiments of wood composite filaments.

[0113] The properties projected for this composition are: tensile strain: 10-50%; tensile strength: 50-100 MPa; tensile modulus: 200-500 MPa; Young's modulus: 400-1000 MPa; and Izod impact strength: 5-20 KJ/m ² .

Table 3: Wood Composite Filament Composition

Example 7: Conductive Filament [0114] Components printed using conductive filaments can be painted with variety of colors using conductive spray painting used widely in automotive industry. Conductive components generated by 3D printing can be used in cold weather conditions and can easily be defrosted by passing heat though the conducting component.

[0115] Conductive fillers such as carbon black provides conductivity at level as low as 0.01 % by weight. Lower carbon black content does not affect most of the other properties of formulation, however, other conductive fillers including steel fiber and carbon nano tubes provides higher conductivity at the cost of ductility of the formulation. Toughening agents used in formulations of conducting filaments counteract brittleness caused by use of steel fibers and carbon nano tubes. Such formulations provide higher conductivity while maintaining other properties of the filaments.

[0116] The properties projected for this composition are: tensile strain: 10-50%; tensile strength: 50-100 MPa; tensile modulus: 50-100 MPa; Young's modulus: 500-1000 MPa; Izod impact strength: 5-20 KJ/m ² ; and volume resistivity: 1 ^χ 10 ⁴ Ohm-cm.

Table 4: Conductive Filament Composition

[0117] In certain embodiments, the conductive carbon black may be replaced with about 1 % to about 10% carbon nano tubes or about 1 % to about 20% steel fibers.

Example 8: Glow-in-the-dark Filament

[0118] There are a number of different uses of glow-in-the-dark filaments such as decorations and signage and/or instructions provided on highway signs and camping equipment.

[0119] The properties projected for this composition are: tensile strain: 10-50%; tensile strength: 50-100 MPa; tensile modulus: 50-100 MPa; Young's modulus: 500-1000 MPa; Izod impact strength: 5-20 KJ/m ² .

Table 5: Glow-in-the-Dark Filament Composition

[0120] In certain embodiments, strontium aluminate is used instead of zinc sulfide. Equivalents and Scope [0121 ] Other than described herein, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages, such as those for amounts of materials, elemental contents, times and temperatures, ratios of amounts, and others, in the following portion of the specification and attached claims may be read as if prefaced by the word "about" even though the term "about" may not expressly appear with the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0122] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains error necessarily resulting from the standard deviation found in its underlying respective testing measurements. Furthermore, when numerical ranges are set forth herein, these ranges are inclusive of the recited range end points (i.e., end points may be used). When percentages by weight are used herein, the numerical values reported are relative to the total weight.

[0123] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. The terms "one," "a," or "an" as used herein are intended to include "at least one" or "one or more," unless otherwise indicated.

[0124] Within this specification, the term "about" means plus or minus 10%, more preferably plus or minus 5%, most preferably plus or minus 2%. [0125] Any patent, publication, internet site, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference.

[0126] Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0127] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[0128] While this invention has been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.