DE102018115692A1 - 3D printing of organic fibers - Google Patents

Abstract

The invention relates to a method for three-dimensional printing of organic fibers while obtaining a printed object and a 3D-printed printed object containing organic fibers.

Description

The invention relates to a method for three-dimensional printing of organic fibers while obtaining a printed object and a 3D-printed printed object containing organic fibers.

Pattinson ( SW Pattinson, AJ Hart, Adv. Mater. Technol. 2017, 2, 1600084 ) describes 3D printing of a flowable composition containing cellulose acetate in acetone.

Compton ( Compton, BG and Lewis, JA (2014), 3D Printing of Lightweight Cellular Composites. Adv. Mater., 26: 5930-5935 ) describes the 3D printing of a flowable composition based on epoxy, which contains cellulose as reinforcement.

Siqueira ( G. Siqueira, D. Kokkinis, R. Libanori, MK Hausmann, AS Gladman, A. Neels, P. Tingaut, T. Zimmermann, JA Lewis, AR Studart, Adv. Funct. Mater. 2017, 27, 1604619 ) describes the 3D printing of cellulose nanocrystals from a flowable dispersion of cellulose nanocrystals in 2-hydroxyethyl methacrylate monomer and polyether-urethane-acrylate polymer, which is cured with photoinitiator during printing.

DE 10 2007 016 852 A1 describes the production of three-dimensional cellulose structures in a 3D printed form.

CN 105295106 A describes the 3D printing of cellulose by extrusion printing from a composite material made of cellulose in polylactic acid.

WO 2004 018185 A1 describes the 3D printing of cellulose starch compositions.

EP 0 829 519 A1 describes the production of three-dimensional moldings by pressing and heating.

DE 693 22 948 T2 describes the production of pellets from wood fibers with polyvinyl chloride.

Henke (Henke, K. (2016). Additive construction by extrusion of lightweight wood concrete, dissertation, TU Munich) describes the extrusion of wood concrete.

DE 102 38 897 B4 describes the extrusion of a composition containing sawdust, ocher particles and sodium silicate liquid.

Wang ( Wang, Xin, et al. "3D printing of polymer matrix composites: A review and prospective." Composites Part B: Engineering 110 (2017): 442-458 .) describes 3D printing of composite materials in an overview article.

When packaging machine parts, machines or other goods, a negative form is often made from corrugated cardboard, into which the machine part, the machine or the other goods fit exactly. On the one hand, this had the disadvantage that a lot of waste was produced. Secondly, the topology of the packaging was poorly optimized.

So far, form-fitting protective packaging has been produced from cellulose fiber material with fiber casting or by cutting corrugated cardboard.

Up to now, it was not possible to produce positive-locking protective packaging from cellulose fiber material from larger machines, machine parts or other goods cost-effectively with the known 3D printing processes.

The object of the present invention is to provide a technology with which, for example, packaging material can be produced inexpensively and without waste while optimizing the topology.

The object on which the invention is based is achieved in a first embodiment by a method for three-dimensional printing of organic fibers while obtaining a printed object, in which an aqueous fiber composition is printed on a substrate using a 3D printer, the Fiber composition contains organic fibers with a median fiber strength in a range of 1.5 to 2000 microns.

The fiber thickness can be determined with an optical microscope.

This process enables, for example, very cost-effective printing of aqueous compositions made of cellulose, which was obtained from waste paper, and conventional powder glue into packaging material. Furthermore, the inventors have found that fibers with a fiber thickness below the claimed range are more difficult to process due to their higher surface area. Above the claimed range of fiber thickness, the fibers are very difficult to print. With the method according to the invention it is possible, for example, to print inexpensive environmentally friendly and topologically optimized packaging material made of cellulose for machines, machine parts or other goods using large printing nozzles. For the first time, a form-fitting protective packaging can be made from cellulose fiber material without producing waste.

It is therefore particularly preferred if the organic fibers are cellulose fibers. In principle, however, the organic fibers can also be, for example, polymer fibers such as polyacrylonitrile fibers, polyalkylene fibers, polyamide fibers or polyester fibers.

The use of natural raw materials such as cellulose for the manufacture of the packaging makes it environmentally friendly. The raw materials can be obtained, for example, from waste paper or packaging already printed according to the invention. The waste paper can be ground dry or wet, for example, to obtain the fibers. The packaging produced according to the invention can then also be easily recycled.

Depending on the size, weight and geometry of the article to be packaged, it is possible with 3D printing to individually adapt each packaging. For example, the type of fiber, the fiber thickness or the formulation of the fiber composition can be optimally adjusted depending on the application. The wall thickness can be adjusted to the weight and size of the item to be packaged, which means that the printed packaging remains light and still stable. Due to a grid structure, the printed packaging can offer the necessary stability and no massive packaging is necessary. In addition, raw materials can be saved, which in turn offers an advantage over the currently standard process.

3D printing is a flexible process that is advantageous for producing an exclusive and individual packaging in a short time. 3D printed packaging is produced with fewer production steps. On the basis of a CAD file of the article to be packed, for example, a negative form is created digitally. For example, the file required for 3D extrusion is generated from this. This file can be used to start 3D printing.

So far, the 3D printing process is fully automated and is only controlled by one operator. For example, the machine has no additional tools apart from the wearing parts such as nozzles, hoses, etc. and must be serviced regularly. The conventional method uses tools that require additional maintenance. This includes the cutting tool.

method

Preferably, the organic fibers and / or the fiber composition are not melted during the printing process.

With the exception of the optional drying step, the method is preferably carried out at a temperature in a range from 10 to 40 ° C.

The print object is preferably dried after the printing process. This drying process can preferably be carried out in air. This air can preferably have a temperature in a range from 20 to 160 ° C. This drying after the printing process can preferably be carried out over a period in a range from 0.1 to 48 hours.

The drying process can preferably be carried out at a temperature in a range from 30 to 160 ° C., particularly preferably during the printing process. However, the printed object is preferably only dried so far during the printing process that the surface of the last applied layer is still moist and particularly preferably has a residual water content in a range from 5 to 66% by weight.

The drying process is preferably carried out in air. For example, drying is carried out using a heat source, infrared or microwave drying. The drying process is preferably not carried out under UV light.

The printed object is preferably printed free-standing and in particular is not printed in a solution, in a powder bed or in an elastic mass.

Fiber composition

The fiber composition is preferably not flowable without the application of pressure or force. If the fiber composition is not flowable, this has the decisive advantage that printing can be carried out very precisely without having to be cured with UV light, for example. The viscosity of the fiber composition is preferably in a range from 1,000 to 1,000,000 mPas, particularly preferably 5,000 to 200,000 mPas, at 25 ° C. and 1 bar ambient pressure. For example, the viscosity can be measured with a Rosand RH2000 table capillary rheometer in a shear rate range of 100-1000 s ^-1 .

The pH of the fiber composition is preferably in a range from 7 to 9.

The organic fibers are contained in the fiber composition preferably in an amount in a range from 10 to 90% by weight, very particularly preferably in a range from 15 to 30% by weight.

In addition to organic fibers, further fillers can also be contained in the fiber composition. The further fillers are preferably contained in the fiber composition in a range from 0 to 10% by weight. The proportion of inorganic fillers such as nitrides and / or carbides in the fiber composition is preferably in a range from 0 to 3% by weight.

A binder is preferably also contained in the fiber composition. The binder is preferably an organic binder such as a binder based on cellulose derivatives, adhesives (for example based on polyvinyl acetate, polyacrylate or polyvinylpyrrolidone), sealants, dispersion adhesives (based on inorganic fillers for example), glue or even latex. However, the binder is particularly preferably a binder based on methyl cellulose. The binder can be, for example, a conventional powder glue, preferably based on cellulose and optionally additives. It has been found that starch as a binder is disadvantageous. The fiber composition therefore preferably contains at most 1% by weight of starch, very particularly preferably no starch. Inorganic binders such as cements, gypsum or silicates such as water glass are also possible. Epoxy resin is disadvantageous in the context of the present invention, since this resin usually has to be composed of at least 2 components and then has to be cured. The fiber composition according to the invention therefore preferably contains at most 1% by weight of epoxy resin, very particularly preferably no epoxy resin. Binder additives in addition to the binder may also be present, such as, for example, modified starch ether, synthetic resin and / or additives based on, for example, polyvinyl acetate, polyacrylate or polyvinyl pyrrolidone.

The binder is contained in the fiber composition preferably in an amount in a range from 1 to 30% by weight, very particularly preferably in a range from 6 to 20% by weight. Preferably, more binder than organic fibers is included in the fiber composition. If there is too little binder, the fiber composition may not be plastic enough. The binder, including the binder additives, is contained in the fiber composition preferably in an amount in a range from 1 to 30% by weight, very particularly preferably in a range from 6 to 20% by weight.

The aqueous fiber composition always contains water as a liquid. The fiber composition preferably also contains further liquid. This liquid can be an organic solvent (for example glycerols and / or glycols). The fiber composition preferably contains a total of liquid in a range from 10 to 90% by weight, very particularly preferably in a range from 45 to 80% by weight. The fiber composition preferably contains water in a range from 10 to 90% by weight, very particularly preferably in a range from 45 to 80% by weight. The fiber composition preferably contains other liquids which differ from water, for example organic solvents, in a range from 2 to 15% by weight.

Furthermore, further additives may preferably be contained in the fiber composition in an amount in a range from 0.1 to 15% by weight. These additives can preferably be selected from plasticizers (for example hydrocolloids, cellulose derivatives, organic swelling and binding agents or mixtures thereof), preservatives (for example isothiazolinones), pressing agents and lubricants (for example based on polyoxyethylene, fatty acid, wax, wetting agents or mixtures thereof) , Dispersants, dyes and / or drying retardants. There are preferably no reducing and / or oxidizing agents in the fiber composition. There are preferably no catalysts in the fiber composition.

Organic fibers

As already described above, it is particularly preferred if the organic fibers are cellulose fibers. The cellulose fibers can, for example, also be in the form of sulfate pulps, sulfite pulps, TMP (thermomechanical pulp) and / or CTMP (chemithermomechanical pulp). In principle, however, the organic fibers can also be, for example, polymer fibers such as polyacrylonitrile fibers, polyalkylene fibers, polyamide fibers or polyester fibers.

The organic fibers are preferably cellulose fibers (for example viscose fibers or cellulose fibers from, for example, from softwood, cellulose, sisal, hemp, coconut, jute, grass, flax, or fibers made from waste paper). The cellulose fibers can also be fibrids (e.g. Lyocell fibrids) or pulp or sawdust. The organic fibers can also be a mixture of the aforementioned fibers.

The median fiber length of the organic fibers is preferably in a range from 0.1 to 20 mm, very particularly preferably in a range from 0.7 to 10 mm. If the fibers are too short, then the fibers only get caught badly or matted badly, so that the mechanical stability of the resulting printed object can decrease. If the fibers are too long, the printer nozzle may become clogged more easily.

The median fiber thickness of the organic fibers is preferably in a range from 2 to 500 μm, very particularly preferably in a range from 10 to 70 μm. The organic fibers are preferably not nanofibers. If the organic fibers are too thin, they have a high surface area and are therefore more difficult to process. If nanofibers are not bioabsorbable, then they are probably also a health hazard.

Preferably, no crystalline cellulose and in particular no cellulose nanocrystals are used. It has been shown that the mechanical stability of the printed object can be lower with crystalline cellulose.

The cellulose or the cellulose fibers are preferably not chemically modified and the cellulose fibers are particularly preferably not made of cellulose acetate. The chemical modification breaks or disrupts the hydrogen bond between the hydroxyl groups, so that the mechanical stability of the printed object can be impaired.

Depending on the application, a fiber type and shape and in particular a cellulose fiber type and shape can be selected in order to optimize the printed object for this application.

D Printers

The 3D printer is preferably a delta 3D printer. The 3D printer is preferably a 3D extruder. These are particularly suitable for the production of large packaging.

The nozzle diameter is preferably in a range from 0.3 to 20 mm, particularly preferably in a range from 0.5 to 10 mm. If the nozzle diameter is below this range, it can happen that too much force has to be applied to push the pasty composition through the nozzle. In addition, the pressure takes longer if the nozzle diameter is too small. If the nozzle diameter is above this range, it can happen that printing can no longer be precise enough.

The ratio of the median of the fiber length of the organic fibers to the nozzle diameter is preferably in a range from 0.5: 1 to 50: 1. If the ratio is above this range, then can it may happen that the printing process cannot be started and ended precisely enough. If the ratio is below this range, it can happen that the fibers within the composition are not sufficiently aligned during the printing process and the mechanical stability of the printed object is impaired.

The ratio of the nozzle diameter to the median of the fiber thickness of the organic fibers is preferably in a range from 5: 1 to 200: 1.

The 3D printer preferably has an extruder and particularly preferably an extrusion screw, so that the fiber composition can thus be conveyed to the nozzle.

print object

The printed object is preferably a packaging, very particularly preferably a form-fitting protective packaging.

The printed object is preferably produced according to the method according to the invention.

The 3-point flexural strength of the material of the printed object, determined with a support distance of 40 mm and a load rise speed of 0.15 MPa / s, is preferably in a range from 20 to 200 MPa. The modulus of elasticity of the material of the printed object, measured in the same way, is preferably in a range from 200 to 4000 MPa. The measurement was carried out on samples with dimensions of 50x2x7mm. The strength is significantly higher than that of a similarly large corrugated cardboard (bending strength below 5 MPa, elastic modulus below 100 MPa). At least 50% by weight of the printed object is preferably in the form of lightweight structures (for example honeycomb or lattice structures).

The printed object preferably contains less than 1% by weight of thermoplastics and very particularly preferably cellulose fibers in a range from 60 to 95% by weight. As a result, there is no softening above the glass transition temperature, so that the printed objects according to the invention are more temperature-resistant but nevertheless light.

The printed object is preferably according to the test methods OECD 301 or 302 biodegradable.

• 1-3 zeigen als Druckobjekt eine formschlüssige Schutzverpackung aus Cellulose-Fasermaterial für ein Maschinenteil zu einem verschiedenen Druckfortschritt.
• 4 zeigt das Maschinenteil - Maßangaben in mm.

Further practical embodiments and advantages of the invention are described below in connection with the drawings. Show it:

• 1-3 show as a printed object a form-fitting protective packaging made of cellulose fiber material for a machine part for a different printing progress.
• 4 shows the machine part - dimensions in mm.

embodiment

A pasty and non-flowable fiber composition containing the following components was produced by intensive mixing: Component A Softwood cellulose from STW (FZ 350) 21.89% by weight Component B Usual powder glue made from methyl cellulose 7.15% by weight Component C water 64.38% by weight Component D ethylene glycol 6.58% by weight

A homogeneous mass was produced from the components as a fiber composition using SpeedMixer DAC 150SP.

The finished fiber composition was processed as an extrusion mass with the 3D printer WASP Delta 2040. The fiber composition was transported with an extruder to the extrusion die (die diameter 0.75 mm) and printed while the die was moving. First was on a substrate printed like a metal plate. As usual with additive manufacturing, the layers that were already printed were then printed.

On the basis of the CAD file, a file with a corresponding machine code was generated, by means of which the aforementioned printer produced the corresponding component. The 1 to 3 show the print object in different stages of completion. The printed object was a form-fitting protective packaging made of cellulose fiber material for a machine part and had a length of approximately 8 cm, a width of approximately 6 cm and a height of approximately 3 cm. The machine part to be packed is in 4 displayed.

The features of the invention disclosed in the present description, in the drawings and in the claims can be essential both individually and in any combination for realizing the invention in its various embodiments. The invention is not restricted to the described embodiments. It can be varied within the scope of the claims and taking into account the knowledge of the responsible specialist.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102007016852 A1 [0005]
• CN 105295106 A [0006]
• WO 2004018185 A1 [0007]
• EP 0829519 A1 [0008]
• DE 69322948 T2 [0009]
• DE 10238897 B4 [0011]

Non-patent literature cited

• S. W. Pattinson, A. J. Hart, Adv. Mater. Technol. 2017, 2, 1600084 [0002]
• Compton, B.G. and Lewis, J.A. (2014), 3D Printing of Lightweight Cellular Composites. Adv. Mater., 26: 5930-5935 [0003]
• G. Siqueira, D. Kokkinis, R. Libanori, M.K. Hausmann, A.S. Gladman, A. Neels, P. Tingaut, T. Zimmermann, J.A. Lewis, A.R. Studart, Adv. Funct. Mater. 2017, 27, 1604619 [0004]
• Wang, Xin, et al. "3D printing of polymer matrix composites: A review and prospective." Composites Part B: Engineering 110 (2017): 442-458 [0012]

Claims (11)

Process for three-dimensional printing of organic fibers to obtain a printed object, in which an aqueous fiber composition is printed on a substrate using a 3D printer, the fiber composition comprising organic fibers with a median of the fiber strength in a range from 1.5 to Contains 2000 µm. Procedure according to Claim 1 , characterized in that the fiber composition is not flowable without pressure or force. Procedure according to Claim 1 or 2 , characterized in that the fiber length of the organic fibers is in the median in a range of 0.1 to 20 mm. Method according to one of the Claims 1 to 3 , characterized in that the nozzle diameter of the 3D printer is in a range from 0.3 to 20 mm. Method according to one of the Claims 1 to 4 , characterized in that the organic fibers are contained in the fiber composition in an amount ranging from 10 to 90% by weight. Method according to one of the Claims 1 to 5 , characterized in that the fiber composition contains binder in an amount ranging from 1 to 30% by weight. Method according to one of the Claims 1 to 6 , characterized in that the fiber composition contains organic solvents in a range of 2 to 15 wt.%. Method according to one of the Claims 1 to 7 , characterized in that the organic fibers are cellulose fibers. 3D printed printed object containing cellulose fibers with a median of the fiber strength in a range from 1.5 to 2000 µm. Print object according to Claim 9 , characterized in that according to the method according to one of the Claims 1 to 8th was produced. Print object according to one of the Claims 9 or 10 , characterized in that the bending strength is in a range from 20 to 200 MPa.

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