权利要求：
1. A method for additive layer manufacturing in an additive manufacturing device configured for processing a powder, the method comprising:
(i) providing at least one substrate that is not a powder and has a surface adapted for receiving one or more powders to a container of the additive manufacturing device, the container being configured for receiving a powder for processing;
(ii) depositing onto at least a part of the substrate, at a predetermined location on the surface of the substrate, at least a first layer of a first powder comprising a first plurality of particles including at least a first (co)polymer having a melting point between 95° C. and 280° C., the surface of the substrate being composed of a material different from the first (co) polymer;
(iii) fusing, by applying energy generated by at least one energy source of the additive manufacturing device, and according to selective laser sintering, the deposited first layer of the first (co)polymer onto the predetermined location on the surface of the substrate, thereby forming a first fused (co)polymer layer, and
optionally sequentially repeating steps (i)-(iii),
wherein at least one of the container configured for receiving the powder, the substrate, or the first layer of the first powder is at a temperature ranging from 10 to 35° C. prior to performance of step (iii).
2. The method of claim 1, wherein the temperature is a temperature ranging from 15 to 30° C.
3. The method of claim 1, further comprising;
(iv) depositing, at the predetermined location on the surface of the substrate, at least one layer of a second powder comprising a second plurality of particles including at least a second (co)polymer onto at least a part of the first fused (co)polymer layer from step (iii);
(v) fusing the second (co)polymer onto at least a part of the first fused (co)polymer layer generated in step (iii) by applying energy generated from at least one energy source of the additive manufacturing device to the predetermined location according to the selective laser sintering, wherein the second powder and the first powder are of a same material; and
(vi) sequentially repeating steps (iv) and (v) to create an article.
4. The method of claim 1, further comprising
(iv) depositing at least one layer of a second powder comprising a second plurality of particles including at least a second (co)polymer different from the first (co)polymer onto at least a part of first fused (co)polymer layer formed at step (iii);
(v) fusing the second (co)polymer onto the part of the first fused (co)polymer layer generated in step (iii) by applying energy generated from at least one energy source of the additive manufacturing device according to the selective laser sintering; and
(vi) sequentially repeating steps (iv) and (v) to create an article.
5. The method of claim 4, wherein at least one of the first (co)polymer or the second (co)polymer is selected from the group consisting of polyamides, polypropylenes and combinations thereof.
6. The method of claim 4, wherein at least one of the first powder or the second powder further comprises inorganic particles comprising one or more aluminum oxide, one or more silicon carbide, one or more boron carbide, one or more boron nitride, one or more diamonds and combinations thereof.
7. The method of claim 1, wherein the energy source comprises a laser configured to scan an emitted laser beam over the deposited layer of first powder at the predetermined location on the surface of substrate.
8. The method of claim 1, wherein the first layer of the first powder has a thickness that is equal to or approximately equal to an average diameter of a respective powder particle the plurality of powder particles.
9. The method of claim 8, wherein the thickness of the first layer of the first powder is 300 μm or less.
10. The method of claim 9, wherein the diameter of the respective powder particle of the first plurality of powder particles ranges from 3 μm to a diameter less than 300 μm.
11. The method of claim 1, wherein the first (co)polymer is selected from the group consisting of thermoplastic (co)polymers, thermoplastic elastomeric (co)polymers, and cross-linkable (co)polymers.
12. The method of claim 1, wherein the first (co)polymer is a thermoplastic (co)polymer selected from the group consisting of polyurethanes, fluoropolymers and combinations thereof.
13. The method of claim 1, wherein the first (co)polymer is a thermoplastic (co)polymer exhibiting an elongation at break of at least 200%.
14. The method of claim 1, wherein the first (co)polymer is a partially fluorinated thermoplastic fluoropolymer.
15. The method of claim 1, wherein the first (co)polymer is a thermoplastic or cross-linkable (co)polymer including units derived from TFE and HFP monomers, and at least one comonomer selected from vinyl fluoride (VF), vinylidene fluoride (VDF), ethene (E), propene (P), or a combination thereof.
16. The method of claim 1, wherein the surface of the substrate comprises a material selected from metals, organic fibers, inorganic fibers, ceramics, and combinations thereof.
17. The method of claim 1, wherein the surface of the substrate comprises a plurality of alternately raised areas and lowered areas having at least one longest dimension of from about 1/10 up to about 3 times an average diameter of the first plurality of powder particles.
18. The method of claim 17, wherein the plurality of alternately raised areas comprises a plurality of ridges, and the plurality of lowered areas comprises a plurality of grooves, optionally wherein the first plurality of powder particles includes particles of the first (co)polymer having a diameter of from 3 μm to less than 300 μm.
19. An article produced using the method of claim 1, optionally wherein the article is an abrasive article.
发明内容：
[0005]Generally, partially crystalline polymers are used in SLS. For processing these powders, the powder bed is heated to a temperature above the crystallization temperature of the polymer. For PA12 (also known as Nylon 12) a polyamide commonly used for making articles with SLS, the powder bed is generally heated above 150° C., which is well above the polyamide's crystallization temperature of 144° C.
[0006]Heating of the powder bed is usually performed by heating the processing/sintering chamber. The energy provided by the laser beam is then sufficient to fuse (“sinter”) the polymer powder in the desired regions. When the temperature of the sintered polymer article drops below its crystallization temperature, the polymer starts to crystallize which may lead to curling of the article. The process may have to be interrupted to avoid creating distorted articles. Therefore, in conventional SLS the processing temperature is kept well above the crystallization temperature of the polymer to be processed and below the melting temperature of the polymer (about 186° C. for an SLS PA12 powder).
[0007]The need for high temperatures and strict temperature control in conventional SLS methods is costly and time-consuming. Unconsolidated powder may undergo thermal ageing in the heated chamber and can no longer be recycled. The necessity to apply rather elevated temperatures also may not allow processing of temperature-sensitive (co)polymers, for example cross-linkable (co)polymers, by SLS.
[0008]Therefore, there is a need to provide additive manufacturing method that allows to process at least some materials at low temperatures.
[0009]Thus, in one aspect there is provided a method for additive layer manufacturing, preferably selective laser sintering, in an additive manufacturing device for processing a powder, the method comprising:[0010](i) providing at least one solid substrate that is not a powder in the container of the processing device for receiving the powder for processing wherein the substrate is either placed into to the container and can be removed from it after processing or is removably attached to it;[0011](ii) placing at least a first layer of a first powder comprising at least a first (co)polymer onto at least a part of the substrate;[0012](iii) fusing the first (co)polymer onto at least a part of the substrate at a desired location to deposit a first layer of the first (co)polymer onto the substrate by applying energy generated by at least one energy source of the manufacturing device to that location, wherein the substrate has a surface for receiving particles of the first (co)polymer and wherein at least the surface is of different material than the first (co)polymer.
[0013]In another aspect there is provided an additive layer manufacturing method, preferably selective laser sintering, for manufacturing an article, the method comprising:[0014](i) providing a layer of a first powder, the first powder comprising at least one first (co)polymer;[0015](ii) depositing successive layers of the first powder and selectively fusing each layer prior to deposition of the subsequent layer so as to form the article,[0016]wherein the first powder further comprises particles comprising one or more aluminum oxide, one or more silicon carbide, one or more boron carbide, one or more boron nitride, one or more diamond or combinations thereof.
[0017]In a further aspect there is provided an article obtained using an above method.
[0018]In yet another aspect there is provided a tool for finishing a surface comprising an article manufactured by a method as above.
[0019]In a further aspect there is provide the use of a powder in additive manufacturing, preferably selective laser sintering.
[0020]The following Listing of Exemplary Embodiments summarizes the various exemplary illustrative embodiments of the present disclosure.
LISTING OF EXEMPLARY EMBODIMENTS
[0021]A. A method for additive layer manufacturing, preferably selective laser sintering, in an additive manufacturing device for processing a powder, the method comprising:[0022]providing at least one solid substrate that is not a powder in the container of the processing device for receiving the powder for processing wherein the substrate is either placed into to the container and can be removed from it after processing or is removably attached to it;[0023]placing at least a first layer of a first powder comprising at least a first (co)polymer onto at least a part of the substrate;[0024]fusing the first (co)polymer onto at least a part of the substrate at a desired location to deposit a first layer of the first (co)polymer onto the substrate by applying energy generated by at least one energy source of the manufacturing device to that location, wherein the substrate has a surface for receiving particles of the first (co)polymer and wherein at least the surface is of different material than the first (co)polymer.[0025]B. The method according to Embodiment A, wherein the first and second powder prior to fusing, the container for receiving the powder, and/or the article and/or the substrate material have a temperature below 75° C. before and during manufacturing the article and preferably from about 15 to 30° C. at least 20° C.[0026]C. The method according to any preceding Embodiment, wherein the surface of the substrate contains a plurality of raised and/lowered areas having at least one longest dimension of from about 1/10 up to about 3 times the size of the particles of the first (co)polymer.[0027]D. The method according to any one of the preceding Embodiments, wherein the method further comprises:[0028]providing at least one layer of a second powder comprising at least a second (co)polymer onto at least a part of the deposited first layer generated in step (iii),[0029]fusing the second (co)polymer at a desired location onto at least a part of the (co)polymer layer generated in step (iii) by applying energy generated from at least one energy source of the manufacturing device to that location; wherein the second powder may be identical or different to the first powder and wherein the second (co)polymer may be identical with or different to the first (co)polymer.[0030]E. The method according to any one of the preceding Embodiments, further comprising:[0031]providing at least one layer of a second powder comprising a second (co)polymer and fusing the second (co)polymer onto at least a part of a previously formed layer, wherein the second powder is identical with or different to the first powder and wherein the second (co)polymer is identical with or different to the first (co)polymer and[0032]repeating (vi) to create an article, wherein the second powder used in (vii) may be always the same second powder or one or more different second powders.[0033]F. The method according to any one of the preceding Embodiments, wherein the first and second powder prior to fusing, the container for receiving the powder, and/or the article and/or the substrate material have a temperature below 75° C. before and during manufacturing the article and preferably at least 20° C.[0034]G. The method of any one of the preceding Embodiments, wherein the energy generated by the energy source is a laser beam.[0035]H. The method of any one of the preceding Embodiments, wherein the first layer of the first powder has a thickness that is about the same as the thickness of the particle size of the powder.[0036]I. The method of any one of the preceding Embodiments, wherein the first layer of the first powder has a thickness of 300 μm or less and wherein the particle size of the first powder is 300 μm or less.[0037]J. The method according to any one of the preceding Embodiments, wherein the particles of the first (co)polymer have a size of from 3 μm to less than 300 μm.[0038]K. The method according to any one of the preceding Embodiments, wherein the first (co)polymer is a (co)polymer selected from group consisting of thermoplastic (co)polymers, thermoplastic elastomers, and cross-linkable (co)polymers.[0039]L. The method according to any one the preceding Embodiments, wherein the first (co)polymer is a thermoplastic (co)polymer selected from a polyurethane, a fluoropolymer and combinations thereof.[0040]M. The method according to any one of the preceding Embodiments, wherein the first (co)polymer is a thermoplastic (co)polymer and has an elongation at break of at least 200%, preferably at 450%, more preferably at least 500%, most preferably at least 600%.[0041]N. The method according to any one of the preceding Embodiments, wherein the first (co)polymer is a thermoplastic partially fluorinated fluoropolymer.[0042]O. The method according to any one of the preceding Embodiments, wherein the first (co)polymer comprises is a thermoplastic or cross-linkable (co)polymer and comprises units derived from TFE and HFP, further comprises at least one comonomer selected from vinyl fluoride (VF), vinylidene fluoride (VDF), ethene (E) or propene (P) or a combination thereof.[0043]P. The method according to any one of the preceding Embodiments, wherein the first and/or the second powder further comprises at least one (co)polymer selected from the group of polyamides and polypropylenes and a combination thereof.[0044]Q. The method according to any one of the preceding Embodiments, wherein the first and/or the second powder further comprises particles comprising one or more aluminum oxides, one or more silicon carbides, one or more boron carbides, one or more boron nitrides, one or more diamonds and combinations thereof.[0045]R. The method according to any one of the preceding Embodiments, wherein the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 70° C., preferably below 65° C., more preferably below 60° C., more preferably below 55° C., more preferably below 45° C., more preferably below 40° C., more preferably below 35° C., more preferably below 30° C. prior and during the manufacturing of the article and preferably at least above 0° C., preferably at least above 20° C.[0046]S. The method according to any one of the preceding Embodiments, wherein the substrate has a surface for receiving the particles of the first (co)polymer and wherein the surface comprises a material selected from metals, organic fibers, inorganic fibers, ceramics, and combinations thereof.[0047]T. The method according to any one of the preceding Embodiments, wherein the substrate has a surface for receiving particles of the first (co)polymer and the surface contains a plurality of raised and/lowered areas having at least one longest dimension of from about 1/10 up to about 3 times the size of the particles of the first (co)polymer and wherein the particles of the first (co)polymer have a size of from 3 μm to less than 300 μm and wherein the areas is in the form of a groove, a ridge, a dome, a pore and a combination thereof.[0048]U. The method according to any one of the preceding Embodiments, wherein the substrate is removably attached to the container for receiving the powder by at least one adhesive.[0049]V. The method according to any one of the preceding Embodiments wherein the substrate is an adhesive tape.[0050]W. An article produced using the method according to any one of Embodiments A to V.[0051]X. A tool for finishing a surface comprising an article manufactured by the method according to any one of Embodiments A to V.[0052]Y. An additive manufacturing process using a powder comprising a first (co)polymer and further comprising particles comprising one or more aluminum oxide, one or more silicon carbide, one or more boron carbide, one or more boron nitride, one or more diamonds and combinations thereof, optionally wherein the additive manufacturing comprises selective laser sintering, wherein the first (co)polymer is selected from thermoplastic (co)polymers, thermoplastic elastomers, and cross-linkable (co)polymers and combinations thereof and wherein the first (co)polymer is present as particles having a size of from 3 μm to 300 μm, inclusive.
[0053]Various aspects and advantages of exemplary embodiments of the disclosure have been summarized. The above Summary and Listing of Exemplary Embodiments are not intended to describe each embodiment or every implementation of the embodiments of the present disclosure. The Detailed Description and Examples that follow more particularly exemplify certain presently preferred embodiments using the principles disclosed herein.
具体实施方式：
[0067]While the above-identified drawings, which may not be drawn to scale, set forth various embodiments of the present disclosure, other embodiments are also contemplated, as noted in the Detailed Description.
DETAILED DESCRIPTION
[0068]Before any embodiments of this disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description. Contrary to the use of “consisting”, the use of “including,”“containing”, “comprising,” or “having” and variations thereof is meant to encompass the items listed thereafter as well as additional items.
Glossary
[0069]Certain terms are used throughout the description and the claims that, while for the most part are well known, may require some explanation. It should be understood that:
[0070]The terms “(co)polymer” or “(co)polymers” includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction, including, e.g., transesterification. The term “copolymer” includes random, block and star (e.g. dendritic) copolymers.
[0071]The term “molecularly same (co)polymer” means one or more (co)polymers that have essentially the same repeating molecular unit, but which may differ in molecular weight, method of manufacture, commercial form, and the like.
[0072]The terms “particle” and “particulate” are used substantially interchangeably. Generally, a particle or particulate means a small distinct piece or individual part of a material in finely divided form. However, a particulate may also include a collection of individual particles associated or clustered together in finely divided form. Thus, individual particles used in certain exemplary embodiments of the present disclosure may clump, physically intermesh, electro-statically associate, or otherwise associate to form particulates. In certain instances, particulates in the form of agglomerates of individual particles may be intentionally formed such as those described in U.S. Pat. No. 5,332,426 (Tang et al.).
[0073]The term “mean particle diameter” means the number-average diameter obtained by measuring the diameter of 50 individual particles using Scanning Electron Microscopy (SEM).
[0074]The terms “about” or “approximately” with reference to a numerical value or a shape means +/−five percent of the numerical value or property or characteristic, but expressly includes the exact numerical value. For example, a viscosity of “about” 1 Pa-sec refers to a viscosity from 0.95 to 1.05 Pa-sec, but also expressly includes a viscosity of exactly 1 Pa-sec. Similarly, a perimeter that is “substantially square” is intended to describe a geometric shape having four lateral edges in which each lateral edge has a length which is from 95% to 105% of the length of any other lateral edge, but which also includes a geometric shape in which each lateral edge has exactly the same length.
[0075]The term “substantially” used with reference to a property or characteristic means that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited. For example, a substrate that is “substantially” transparent refers to a substrate that transmits more radiation (e.g. visible light) than it fails to transmit (e.g. absorbs and reflects). Thus, a substrate that transmits more than 50% of the visible light incident upon its surface is substantially transparent, but a substrate that transmits 50% or less of the visible light incident upon its surface is not substantially transparent.
[0076]Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
[0077]Unless indicated otherwise the total amounts of ingredients of a composition expressed as “percentage by weight”, “% by weight” or “wt. %” or similar add up to 100%, i.e., the total weight of the composition is 100 wt. % unless stated otherwise. Likewise, unless indicated otherwise the total amounts of ingredients of a composition expressed as “percentage by volume”, “vol %” or similar add up to 100% and the total volume of the composition is 100% unless stated otherwise.
[0078]Any numerical range recited herein describing a physical property or a concentration is intended to include all values from the lower value to the upper value of that range and including the endpoints. For example, a concentration range of from 1% to 50% is intended to be an abbreviation and to expressly disclose the values between the 1% and 50%, such as, for example, 2%, 40%, 10%, 30%, 1.5%, 3.9% and so forth.
[0079]As used in this specification and the appended embodiments, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to fine filaments containing “a compound” includes a mixture of two or more compounds. As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0080]By using terms of orientation such as “atop”, “on”, “over,”“covering”, “uppermost”, “underlying” and the like for the location of various elements in the disclosed coated articles, we refer to the relative position of an element with respect to a horizontally-disposed, upwardly-facing substrate. However, unless otherwise indicated, it is not intended that the substrate or articles should have any particular orientation in space during or after manufacture.
[0081]By using the term “overcoated” to describe the position of a layer with respect to a substrate or other element of an article of the present disclosure, we refer to the layer as being atop the substrate or other element, but not necessarily contiguous to either the substrate or the other element.
[0082]By using the term “separated by” to describe the position of a layer with respect to other layers, we refer to the layer as being positioned between two other layers but not necessarily contiguous to or adjacent to either layer.
[0083]Various exemplary embodiments of the disclosure will now be described. Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments, but are to be controlled by the limitations set forth in the claims and any equivalents thereof.
[0084]It has been found that initial layer formation without curling can be achieved by fusing (“sintering”) the initial (co)polymer layer onto a substrate material that is not a powder and that is of a different material than the initial (co)polymer layer. Contrary to creating the initial layer within the powder bed the initial layer is constrained in its planar direction which prevents or reduces curling of the first and subsequent layers. This concept is referred to as herein as “constraint sintering”.
[0085]A sketch illustrating constrained sintering is shown in FIG. 1A and FIG. 1B. 1. In FIG. 1A, film A is not connected to an underlying substrate B, i.e. they are not joined thus resulting in different strain and no in-plane tensile stress. Consequently, shrinkage can occur not only perpendicular to the plane of the film A but also in-plane. In FIG. 1B, the film A is connected to the underlying substrate B thus resulting in a same strain and in-plane tensile stress. Now shrinkage can only occur perpendicular to the plane of the film A.
[0086]By providing a substrate onto which the (co)polymer is fused during the formation of the first layer articles can be produced at low temperatures or even at room temperature. Bringing the (co)polymer powder above its crystallization temperature, for example by heating the powder or the processing chamber, is not necessary. The article to be produced can be directly built onto the substrate material without the need of creating support structures, i.e. structures generated by SLS from the same (co)polymer but that are not intended to form a part of the final article but are meant to be removed from the article generated.
[0087]The powdered (co)polymer material is provided in sufficient thickness over the substrate such that the first layer is fused onto the substrate. Typically, the layer is sufficiently thin, and may, for example, be a single layer. The single layer thickness may be made up by the particle size of the powder, preferably the (co)polymer particles. In some exemplary embodiments, the powder for producing the first layer (“first powder”) is homogeneous and contains only the (co)polymer. Once the first layer has been deposited onto the substrate subsequent layers may be built using the same powder or one or more different powders (“second powder”). Typically, the first layer deposited onto the substrate may be the first layer of the final article to be built.
[0088]The first and subsequent layers are deposited by fusing the (co)polymer in the first or second powder by exposure to an energy beam, typically a laser beam, at desired and preprogrammed locations. The energy beam is selected such that the energy it generates is sufficient to fuse the (co)polymer particles onto the substrate layer or subsequent layers at the desired locations.
[0089]The substrate is a solid material that is not a powder and is selected such that it allows for the formation of (co)polymer layers on its surface. Various materials may be used depending on the powder selected for additive manufacturing and the energy applied and will be described in greater detail below but typically the substrate is made of a different material than the first (co)polymer, or at least the surface of the substrate onto which the first (co)polymer is to be fused is made of a different material than the first (co)polymer.
[0090]In some exemplary embodiments the production process is carried out at ambient temperature (e.g., room) temperature, typically 20-30° C.
[0091]The present disclosure describes an additive layer manufacturing method for manufacturing a solid article. The additive manufacturing method of the present disclosure creates an article by repeated fusing particle in a powder to form layers in a controlled way to create an article. Preferably, the additive manufacturing method is selective laser sintering, which means the particles are fused upon exposure to one or more laser beams.
[0092]The method according to the present disclosure is carried out in an additive manufacturing device. An additive manufacturing device for SLS as known in the art can be used. Such devices typically contain a processing chamber. The processing chamber contains at least one container for receiving the powder for additive processing. The container for receiving the powder for processing is referred to herein also as “base plate” or “powder bed”. The base plate may be moved upwards or downwards in a controlled manner to allow for new powder to be placed into the base plate.
[0093]The device includes at least one energy source that provides an energy beam, e.g. a laser beam, that can be directed at desired locations on the base plate to allow the formation of layers by fusing the (co)polymer particles in the powder at desired locations.
[0094]The method of the present disclosure includes the step of providing at least one layer of a first powder onto the substrate. The substrate is placed in the container receiving the powder of the processing chamber of the device. The substrate can be removed from the container after the first layers has been deposited onto the substrate or after the article has been produced or it can be removably attached to the container
[0095]The first powder comprises at least one first (co)polymer. The method further includes the step of fusing the first (co)polymer at a desired location in the powder to deposit the first (co)polymer onto the substrate and to provide at least a first layer deposited onto the substrate. The first layer may be continuous or discontinuous and may describe a pattern. The first layer may only be created in selected areas of the substrate. Powder that was not exposed to the energy beam remains in its powdered state, i.e. is unfused and can be removed if needed.
[0096]The method further includes the step of depositing successive layers onto the at least first layer to create an article as is done in conventional additive manufacturing using powders, for example in SLS. Fusing in this context means fusing or melting the (co)polymer comprised in the powder. In the case where the powder comprises the abrasive particles described below or other particles that do not melt/fuse upon exposure to the energy beam, the (co)polymer may not only fuse to a previously formed (co)polymer layer but may also fuse to these particles and may solidify onto the particles after fusing. In some cases the powder may comprise a blend of powders, for example, a first powder comprising a first (co)polymer, and one or more additional powders comprising other (co)polymers, inorganic particulates, mixtures thereof and combinations thereof.
[0097]The process can be carried out in the appropriate conventional additive processing devices, e.g. SLS printers. An advantage of the methods disclosed herein over conventional SLS processing is that the processing can be carried out at low temperatures, for example below 75° C. or even at room temperature (20° C.), for example between 15° C. and 50° C. The additive processing, preferably, is carried out without any additional heating, meaning any heating other than the heat generated by the energy source, e.g. the laser beam to fuse the (co)polymer particles.
[0098]The processing chamber and/or the powder prior to fusing and/or the article and/or the substrate can be kept at such low temperatures, for example at temperatures below the crystallization temperature of a crystalline or semi-crystalline (co)polymer to be processed. In some exemplary embodiments, the processing chamber and/or the powder and/or the substrate are not heated during manufacturing of the article and/or not preheated before manufacturing of the article by additional heating. In some exemplary embodiments, the processing chamber and/or the substrate and/or the powder in the powder bed prior to fusing have a temperature below 75° C., during manufacturing the article.
[0099]Preferably, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 70° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 65° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 60° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 55° C.
[0100]In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 45° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 40° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 35° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature below 30° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have the aforementioned temperatures during the manufacturing of the solid article.
[0101]In certain exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 0° C. and 75° C. In some exemplary embodiments the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 5° C. and 70° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 5° C. and 60° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 10° C. and 50° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 10° C. and 45° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 10° C. and 40° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 10° C. and 35° C.
[0102]In further exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 10° C. and 30° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have a temperature between 10° C. and 25° C. In some exemplary embodiments, the processing chamber and/or the powder prior to fusing and/or the article and/or the substrate have the aforementioned temperature ranges during the manufacturing of the solid article.
First Powder
[0103]The first powder for use in the methods described herein contains at least one first (co)polymer. The (co)polymer is in powdered form, which means it is present as fine particles. Typically, the (co)polymer particles have a particle size of less than 500 μm (e.g. D100<500 μm), preferably less than 300 μm (e.g. D100<100 μm) and more preferably less than 100 μm (e.g. D100<100 μm). Typical particle sizes include average particles sizes from 5 to 150 μm (D50). The particle size is determined by the longest axis of the particle. The particle size can be determined by laser diffraction in a particle analyzer. Polymer particles of this size are commercially available or can be prepared, for example, by milling and sieving as known in the art.
[0104]Preferably, the particles are spherical or substantially spherical (aspect ratio preferably is from 0.5 to 1.5).
[0105]The first powder may contain at least 45% by weight of (co)polymer, preferably at least 50% by weight and in some embodiments the powder contains up to 100% of (co)polymer. For example, the powder may contain from 45% by weight to 65% weight, or from 55 by weight up to 85% by weight of (co)polymer, preferably total amount of (co)polymers and more preferably of a (co)polymer described below. The first powder, for example, may contain from about 60% by volume up to about 100% by volume, from example from 70% by volume to 95% by volume of a (co)polymer, more preferably of a (co)polymer described below.
Polymers
[0106]The first powder for use in the methods according to the present disclosure contain at least one first (co)polymer. In one embodiment the first (co)polymer preferably is a soft or flexible (co)polymer, i.e. a (co)polymer having a high elongation at break. For example, the method may be particularly suitable for processing powders comprising a first (co)polymer that is a thermoplastic (co)polymer having a shore D hardness (ISO 868) below 70, preferably below 50, for example below 45 or 40 or even below 38. Preferably, the first (co)polymer is a thermoplastic (co)polymer having an elongation at break of at least 200%, preferably at least 450%, more preferably at least 500%, most preferably at least 600% (DIN EN ISO 527-1, test speed 50 mm/min). In some exemplary embodiments, the first (co)polymer is a thermoplastic (co)polymer having a flexural modulus of less than 100 MPas (ISO 6721-1).
[0107]In one exemplary embodiment the first (co)polymer is a thermoplastic polyurethane, for example an at least partially crystalline polyurethane, preferably having a shore D hardness as described above, more preferably having a shore D hardness and an elongation at break and or a flexural modulus as described above.
[0108]The at least partially crystalline, i.e. thermoplastic (co)polymers may have a melting point between about 78° C. and 300° C., for example between 95° C. and 280° C.
[0109]In another exemplary embodiment the first (co)polymer is a curable (co)polymer, i.e. a (co)polymer that can be cross-linked, for example by applying heat, radiation or by mixing with a curing catalyst and activating the curing catalyst. Curable (co)polymers include, for example, curable acrylic resins, i.e. (co)polymers with one or more acrylic and methacrylic functional groups, preferably end groups; curable epoxy resins, i.e. (co)polymers with one or more epoxy groups, preferably end groups; curable polyesters and vinyl esters with unsaturated sites at the ends or on the backbone and combinations thereof. In one embodiment, the curable (co)polymer is a fluoropolymer, e.g. a curable fluoroelastomer. Typical examples of curable fluoroelastomers include (co)polymers having repeating units derived from vinylidene fluoride (VDF) and one or more other unsaturated perfluorinated olefins or unsaturated olefinic ethers like perfluorinated alkyl vinyl ethers or perfluorinated alkyl allyl ethers. In a preferred embodiment the curable (co)polymer is a thermoset, i.e. a (co)polymer that is cross-linked by application of heat only, i.e. without requiring curing catalysts or curing systems. In some exemplary embodiments the curable (co)polymer is an epoxy resin, i.e. a curable (co)polymer having at least one epoxy end group.
[0110]The first (co)polymer according to the present disclosure is present in the powder as particles, for example particles having a particle size of less than 500 μm (e.g. D100<500 μm), preferably less than 300 μm (e.g. D100<100 μm) and more preferably less than 100 μm (e.g. D100<100 μm). Typical particle sizes include average particles sizes from 5 to 150 μm (D50). Particle size is determined by the longest axis of the particle. The particle size can be determined by laser diffraction in a particle analyzer. Polymer particles of this size are commercially available or can be prepared, for example, by milling and sieving as known in the art.
[0111]In one particular embodiment the first (co)polymer is a fluoropolymer, for example a fluorothermoplastic fluoropolymer having a shore D hardness as described above and more preferably having an elongation at break and/or a flexural modulus as described above. The fluoropolymer preferably is a tetrafluoroethene (TFE)-based fluoropolymer and comprises at least 25% by weight of units derived from TFE. The fluoropolymer further comprises at least 1.5% by weight of units derived from one or more perfluorinated or partially fluorinated or non-fluorinated alpha olefin and combinations thereof. Examples for perfluorinated alpha olefins include Examples for such optional comonomers include fluorinated monomers selected from perfluorinated C3-C8 olefins, in particular, hexafluoropropene (HFP) and alpha olefin ethers, in particular those corresponding to the formula. Examples of perfluorinated unsaturated ether monomers that may be used include those corresponding to the formula (I):
CF2═CF—(CF2)n—O—Rf (I)
wherein Rf represents a perfluorinated aliphatic group that may contain one or more oxygen atoms and n is either 0 or 1. In case n is 0 the ethers are referred to as vinyl ethers (perfluorinated alkyl vinyl ethers or PAVEs). When n is 1 the ethers are referred to as allyl ethers (perfluorinated alkyl allyl ethers or PAAEs). In some exemplary embodiments, Rf corresponds to
(Rf′O)n(R″fO)mR′″f (II)
wherein R′f and R″f are different linear or branched perfluoroalkylene groups of 2-6 carbon atoms, m and n are independently 0-10, and R′″f is a perfluoroalkyl group of 1-6 carbon atoms. Particular examples include but are not limited to perfluoro(2-propoxypropyl vinyl) ether (PPVE-2), perfluoro(methyl vinyl) ether (PMVE), perfluoro(3-methoxy-n-propyl vinyl) ether, perfluoro(ethyl vinyl ether) (PEVE), perfluoro(2-methoxy-ethyl vinyl) ether, perfluoro(n-propyl vinyl) ether (PPVE-1) and F3C—(CF2)2—O—CF(CF3)—CF2—O—CF(CF3)—CF2—O—CF═CF2.
[0112]Examples of partially fluorinated monomers include vinylidene fluoride, vinylfluoride, and chlorotrifluoroethene (CTFE) and the unsaturated ethers according to formula (I) and (II) above with the difference that Rf is partially fluorinated, which means at least one fluorine atom has been replaced by a hydrogen atom.
[0113]Examples of non-fluorinated alpha olefins include ethene (E) and propene (P).
[0114]Suitable fluoropolymers typically have a melt flow index (MFI) at a 5 kg load at a temperature of 372° C. of from about 100 to 15 g/10 mins (DIN EN ISO 1133-1:2012-03; standardized extrusion die of 2.1 mm in diameter and a length of 8.0 mm).
[0115]In some exemplary embodiments the fluoropolymers contain units derived from the copolymers selected from TFE, HFP, and VDF and may or may not contain units derived from unsaturated ethers according to formula (I). In another embodiment, the comonomers are used to make a copolymer having repeating units derived from vinylidene fluoride, tetrafluoroethene, hexafluoropropene, and optionally an unsaturated ether according to formula (I) above, preferably a perfluoro(propyl vinyl ether) or perfluoro(methyl vinyl ether). In general, the comonomer units in the ranges of 10 mol % to 60 mol % vinylidene fluoride comonomer units, 30 mol % to 80 mol % tetrafluoroethene comonomer units, 3 mol % to 20 mol % hexafluoropropene comonomer units, and 0 mol % to 2 mol % of the one or more unsaturated ether according to formula (I), preferably a perfluoro(propyl vinyl ether), a perfluoro(ethyl vinyl ether), a perfluoro(methyl vinyl ether) or a combination thereof. In another embodiment, the fluoropolymer contains units derived from the comonomer combination comprising TFE and ethene; TFE, HFP and ethene; TFE and propene; TFE, HFP and propene; TFE, HFP, and one or more unsaturated ethers according to formula (I) above; TFE, HFP and VDF; TFE-VDF; TFE-PAVE; TFE-PAAE; and TFE-PAVE-PAAE.
[0116]In other exemplary embodiments the fluoropolymers are selected from thermoplastic fluoropolymers having a melting point of less than 150° C. The low melting thermoplastic fluoropolymers may have a melt-flow index under a 5 kg load at 265° C. (MFI 265/5) of from about 3 to 70 g/10 mins (DIN EN ISO 1133-1:2012-03; standardized extrusion die of 2.1 mm in diameter and a length of 8.0 mm). Typically, the (co)polymers contain units derived from TFE and one or more unsaturated ether as described above in formula (I) and may also contain units derived from the optional comonomers described above, in particular units derived from HFP and/or units derived from vinylidene fluoride. In one embodiment, the fluoropolymers contain units derived from the comonomers TFE, HFP and one or more non-fluorinated comonomers like ethene and propene but no units from an unsaturated ether. In another embodiment the fluoropolymers contain units derived from the comonomers TFE, HFP and vinylidene fluoride but no units from an unsaturated ether.
[0117]The methods according to the present disclosure further use a second (co)polymer. The second (co)polymer may be a (co)polymer selected from the (co)polymers described above for the first (co)polymer. The second (co)polymer may be the same (co)polymer as the first (co)polymer.
[0118]In another embodiment of the present disclosure the first and/or second powders may additionally contain at least one additional (co)polymer selected from a polyamide and/or a polypropylene.
Inorganic Particles:
[0119]In some exemplary embodiments the powder further comprises inorganic particles. In some exemplary embodiments, the particles are abrasive particles and have a Mohs hardness of at least 4, preferably at least 5, more preferably at least 6, more preferably at least 7, more preferably at least 8, more preferably at least 8.5, more preferably at least 9, and more preferably 9.5.
[0120]Preferably, the abrasive particles have hardness greater than or equal to that of aluminum oxide. In some exemplary embodiments, the abrasive particles have hardness greater than or equal to that of silicon carbide.
[0121]In some exemplary embodiments, the particles comprise or consist of aluminum oxide, preferably sintered aluminum oxide, silicon carbide, boron carbide, boron nitride and diamonds.
[0122]In certain exemplary embodiments, the particles are agglomerates of at least one of aluminum oxide particles, silicon carbide particles, boron carbide particles, boron nitride particles, and diamond particles. In some exemplary embodiments, the agglomerates have a binder phase.
[0123]In some particular exemplary embodiments, the particles have an average particle size less than 300 μm (e.g. D100<300 μm), preferably less than 200 μm, preferably less than 150 μm, preferably less than 100 μm, preferably less than 50 μm, preferably less than 25 μm. In some exemplary embodiments, the abrasive particles have an average particle size less than 100 μm in at least one lateral dimension, preferably less than 80 μm in at least one lateral dimension, more preferably less than 50 μm in at least one lateral dimension.
[0124]Preferably, the concentration of the inorganic particles in the powder is below 35 vol %. For example, the concentration of the inorganic particles in the powder may be up to 30 vol %, or up to 22 vol %, or up to 20 vol %, and, more preferably, up to 15 vol %. In one embodiment the concentration of the inorganic particles in the powder is between 15 and 35 vol %.
Second Powder:
[0125]The second powder comprises at least one (co)polymer. The (co)polymer includes the one or more (co)polymer described above. The second powder may also include the additional presence of a polypropene and/or a polyamide. The second powder may also contain the abrasive particles described above. In fact, in one embodiment the second powder may be the same powder as the first powder. In another embodiment, the second powder may be different from the first powder, for example different in its composition, concentration, particle size and combinations thereof.
[0126]The at least second powder may also comprise the abrasive particles described above or it may not comprise them and may be free of abrasive particles. The abrasive particles comprised in the first powder may be the same as in the second powder but differ in concentration. The abrasive particles may differ in their shape but have the same composition, or may differ in composition and shape. Or, the abrasive particles in the first and second powder may be identical but the (co)polymers in the first and second powder differ in concentration or in composition or both. For example, the abrasive particles comprised in the first powder can be diamond particles and the abrasive particles comprised in the at least one further powder can be aluminum oxide particles.
[0127]The