WO2015105762A1

WO2015105762A1 - Materials and methods for three-dimensional fabrication

Info

Publication number: WO2015105762A1
Application number: PCT/US2015/010231
Authority: WO
Inventors: Edward T. Samulski; Joseph M. Desimone
Original assignee: Carbon3D, Inc.
Priority date: 2014-01-08
Filing date: 2015-01-06
Publication date: 2015-07-16

Abstract

A process for the production of a three-dimensional object of a high performance polymer (e.g., a liquid crystal thermoset polymer) is carried out by (a) providing a radiation source (e.g., a carbon dioxide laser) and a carrier for supporting a three dimensional object during production thereof, the radiation source and the carrier defining a build region; (b) providing a precursor of a high performance polymer to the build region in liquid or solid form; (c) cross-linking (e.g., thermally crosslinking) the precursor in the build region to produce a solid polymerized region of the polymer; (d) advancing said carrier with said polymerized region adhered thereto away from said build region to create a subsequent build region between the polymerized region and said radiation source; and (e) repeating steps (b) through (d) until production of the three-dimensional object is completed.

Description

MATERIALS AND METHODS FOR THREE-DIMENSIONAL FABRICATION

Edward T. Samulski and Joseph M. DeSimone

Related Applications

This application claims the benefit of United States Provisional Patent Application Serial No. 61/924,873, filed January 8, 2014, the disclosure of which is incorporated by reference herein in its entirety.

Field of the Invention

The present invention concerns methods, compositions and apparatus for forming three-dimensional objects from thermoset resins.

Background of the Invention.

One of the variety of processes known for additive manufacturing is selective laser sintering (SLS). In general, SLS utilizes a laser (for example, a carbon dioxide laser) to fuse small particles into a mass or "build" that has a desired three-dimensional shape. The laser selectively fuses powdered material by scanning cross -sections generated from a 3-D digital description of the part (for example from a CAD file or scan data) onto the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied to the top surface thereof, and the process is repeated until the part is completed. Because finished part density depends on peak laser power rather than laser duration, a SLS machine typically uses a pulsed laser. The SLS machine may preheat the bulk powder material in the powder bed to a point below its melting point, to make it easier for the laser to raise the temperature of the selected regions the rest of the way to the melting point. Unlike some other additive manufacturing processes such as stereolithography (SLA) and fused deposition modeling (FDM), SLS does not require extensive support structures because the part being constructed is surrounded by unsintered powder at all times. Hence, parts can be made that may be difficult to achieve by other techniques. Unfortunately, the materials available for use in SLS have heretofore been limited, and there is a need for new materials which can be used in SLS-type processes.

Summary of the Invention A first aspect of the present invention is a process for the production of a three- dimensional object from a high performance polymer, comprising the steps of;

(a) providing a (thermal or actinic) radiation source and a carrier for supporting a three dimensional object during production thereof, said radiation source and said carrier defining a build region;

(b) providing a precursor of a high performance polymer to said build region in liquid or solid form;

(c) cross-linking said precursor in said build region (e.g., with said radiation source) to produce a solid polymerized region of said polymer thereon;

(d) advancing said carrier with said polymerized region adhered thereto away from said build region to create a subsequent build region between said polymerized region and said radiation source; and

(e) repeating steps (b) through (d) (sequentially and/or concurrently) until the production of said three-dimensional object is completed.

In some embodiments, the cross-linking step is a thermally cross-linking step (e.g., with a carbon dioxide laser as the radiation source), and said precursor is optionally but preferably in solid form (e.g., as a powder or sheet); In other embodiments, the cross-linking step is a photo -polymerization step, and said precursor is optionally but preferably in liquid form (e.g., as a melt; as a solution with a solvent such as low molar mass free radically polymerizable monomers; or as a combination thereof).

In some embodiments, the high performance polymer comprises a liquid crystalline thermos et (LCT) such as an ester, ester-imide, or ester-amide oligomer.

In some embodiments, the precursor has at least one reactive alkene-containing or alkyne-containing end-cap covalently coupled thereto (e.g., a phenylacetylene, phenylmaleimide, or nadimide end-cap).

In some embodiments, the precursor is provided to said build region in solid form (e.g., as a particulate); in other embodiments, the precursor oligomer is provided to the build region in the form of a continuous solid sheet or sections of a solid sheet.

In some embodiments, the cross-linking step is carried out by laser irradiation.

In some embodiments, the cross-linking step is carried out with patterned irradiation.

In some embodiments, the cross-linking step is a heating step is carried out by laser sintering. A further aspect of the invention is an apparatus for forming a three-dimensional object of a high-performance polymer, comprising:

(a) an energy source (e.g., a heat or actinic radiation source source, such as a carbon dioxide laser);

(b) a carrier operatively associated with said energy source on which carrier said three-dimensional object is formed; and

(c) a sheet supply assembly operatively associated with said carrier and configured to advance a precursor of the high performance polymer into said build region as a solid sheet (e.g., continuously or in segments).

In some embodiments the apparatus further comprises (d) a surplus sheet take-up assembly operatively associated with said sheet supply assembly and configured to advance unused precursor of the high performance polymer out of said build region as a solid sheet.

In some embodiments the apparatus further comprises a controller operatively associated with said carrier, said radiation source, said sheet supply assembly, and optionally said surplus sheet take-up assembly, the controller configured to advance the carrier away from the build region, and advance new solid sheet precursor into said build region.

In some embodiments the sheet supply assembly comprises a roller, chain drive, conveyor belt, or vacuum transfer assembly, or a combination thereof.

In some embodiments the surplus sheet take-up assembly comprises a roller, chain drive, conveyor belt, vacuum transfer assembly, or combination thereof (separate from or together with said sheet supply assembly).

In some embodiments the energy source comprises a patterned energy source.

In some embodiments the energy source comprises a laser (e.g. a carbon dioxide laser).

Non-limiting examples and specific embodiments of the present invention are explained in greater detail in the drawings herein and the specification set forth below. The disclosure of all United States Patent references cited herein are to be incorporated herein by reference in their entirety.

Brief Description of the Drawings

Figure 1 is a schematic illustration of an apparatus useful for carrying out the present invention.

Detailed Description of Illustrative Embodiments The present invention is now described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

Like numbers refer to like elements throughout. In the figures, the thickness of certain lines, layers, components, elements or features may be exaggerated for clarity. Where used, broken lines illustrate optional features or operations unless specified otherwise.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an" and "the" are intended to include plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements components and/or groups or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups or combinations thereof.

As used herein, the term "and/or" includes any and all possible combinations or one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").

Unless otherwise defined, all terms (including 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. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and claims and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well- known functions or constructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being "on," "attached" to, "connected" to, "coupled" with, "contacting," etc., another element, it can be directly on, attached to, connected to, coupled with and/or contacting the other element or intervening elements can also be present. In contrast, when an element is referred to as being, for example, "directly on," "directly attached" to, "directly connected" to, "directly coupled" with or "directly contacting" another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed "adjacent" another feature can have portions that overlap or underlie the adjacent feature.

Spatially relative terms, such as "under," "below," "lower," "over," "upper" and the like, may be used herein for ease of description to describe an element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is inverted, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus the exemplary term "under" can encompass both an orientation of over and under. The device may otherwise be oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Similarly, the terms "upwardly," "downwardly," "vertical," "horizontal" and the like are used herein for the purpose of explanation only, unless specifically indicated otherwise.

It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. Rather, these terms are only used to distinguish one element, component, region, layer and/or section, from another element, component, region, layer and/or section. Thus, a first element, component, region, layer or section discussed herein could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. The sequence of operations (or steps) is not limited to the order presented in the claims or figures unless specifically indicated otherwise.

1. Po ymerizable precursors.

In some embodiments, high performance polymers resins are used as the polymerizable precursor. Numerous examples of such high performance polymers are known, including but not limited to those described in Narang and Fuller, US Patent No. 7,517,641 (Xerox).

Particular examples of suitable precursors resins include, but are not limited to, resins for those materials sometimes referred to as liquid crystalline polymers of esters, ester-imide, and ester-amide oligomers, as described in US Patents Nos. 7,507,784; and 6,939,940. The LCT end-caps are selected for ease of thermosetting for 3D printing via laser sintering, as discussed below, or other processes that will be apparent in view of the present disclosure.

Liquid crystal thermoset monomers ("LCT monomers") or LCT oligomers as used herein may refer to liquid crystal monomers or liquid crystal oligomers that form a liquid crystal thermoset when polymerized (e.g. by chain-extension and/or by cross-linking). The LCT monomers or oligomers can thus be regarded as a macro-monomer or an oligomer of a liquid crystal thermoset.

"Oligomer(s)" as used herein refers to mixtures of varying backbone length liquid crystal polymers, preferably of maximally 500 repeat units, within the weight range of approximately 500 to approximately 15,000 grams per mole, and which in some embodiments are not isolated as discreet molecular weight molecules.

LCT oligomers are relatively short linear liquid crystal polymers (LCPs). LCPs exhibit higher degrees of molecular order (chain parallelism) while in the molten state than other polymeric species.

LCT oligomers preferably comprise a liquid crystal backbone selected from the group consisting of an ester, an ester-imide and an ester-amide, wherein the backbone of the oligomer is entirely, or at least substantially entirely, aromatic in composition. This means that preferably at least 95 mol%, more preferably at least 99 mol%, even more preferably 100 mol% of the monomers present in the backbone are aromatic. The above-described LCT oligomers are known and described in US Patents Nos. 7,507,784 and 6,939,940 to Dingemans et al., the disclosures of which are incorporated by reference herein in their entirety.

The LCT oligomer may be capable of polymerizing by chain-extension. The liquid crystal oligomers are preferably end-capped with self-reactive end-groups, in which case the LCT oligomer has a general structure of:

wherein:

Z indicates the oligomer backbone (e.g., an LCT oligomer as described above and below); and each E is an independently selected end-cap, such as an alkene or alkyne end- cap (as discussed further below).

Such a reactive or self-reactive end-cap is capable of reacting with another self- reactive end-cap of the same type and (optionally) to some extent with the HPP it is intended to reinforce. Accordingly, an LCT oligomer with reactive end-caps is capable of chain- extension. In some embodiments the end-cap is preferably a vinyl, acetylene, or diacetylene- containing group such as a phenylacetylene, phenylmaleimide, or nadimide end-cap, examples of which include but are not limited to;

The LCT oligomers may have a backbone having at least one structural repeat unit selected from the group consisting of

wherein Ar is an aromatic group. Ar may in particular be an aromatic group selected from;

wherein X is selected from the group consisting of

and wherein n is a number or integer less than 500, and wherein E and E' are selected from the group consisting of:

and wherein R' is selected from the group consisting of hydrogen, alkyl groups containing six or less carbon atoms, aryl groups containing six or less carbon atoms, aryl groups containing less than ten carbon atoms, lower alkoxy groups containing six or less carbons, lower aryloxy groups containing ten or less carbon atoms, fluorine, chlorine, bromine and iodine.

Examples of the above-described LCT oligomers are known and described in US Patents Nos. 7,507,784 and 6,939,940 to Dingemans et al, the disclosures of which are incorporated by reference herein in their entirety.

Additional end caps. Additional examples of suitable end-caps for the LCT monomers and oligomers include, but are not limited to, those set forth below:

X = -COOH or -OH or -NH₂ where each group Ar may, in the alternative to being phenyl as shown, be any aromatic or aryl group. It will be appreciated that group X forms a linking group to the oligomer backbone "Z" when reacted thereto.

The arylethynyl benzoic acid end-cap is a useful one to claim for 3D print applications. The arylethynyl and norbornene functionality are used for the thermal post polymerization step and the -COOH, -OH or -NH2 functionality are needed to end-cap the oligomer chain. Note also that any meta- or para-substituted one or multiple aromatic ring system may be used.

There are also solution-based processing techniques and incorporate less expensive and lower curing end-groups, such as benzoxazines and malermides, as shown below:

¾Me 1 EflcH ι$$ used far fii e prejjaratkm of reaet s mono rows ant olgojjers

Cam Tmpemtm

fatty $tt m (t)

See generally T, Dingemans, High-Temperature Thermosets, in: K. Matyjaszewski and M. Moller, Polymer Science: A Comprehensive Reference, Vol 5, pp. 753-769 (2012).

Resin blends. In addition, any suitable free-radically polymerizable material can be used in combination with the above LCP resins to provide composites useful for carrying out the present invention. Examples include, but are not limited to, acrylics, methacrylics, acrylamides, styrenics, olefins, halogenated olefins, cyclic alkenes, maleic anhydride, alkenes, alkynes, carbon monoxide, functionalized oligomers, multifunctional cure site monomers, etc., including combinations thereof. Examples of liquid resins, monomers and initiators include but are not limited to those set forth in US Patents Nos. 8,232,043; 8,119,214; 7,935,476; 7,767,728; 7,649,029; WO 2012129968 Al; CN 102715751 A; JP 2012210408 A.

Additional ingredients. The resin or polymerizable precursor material can have solid particles suspended or dispersed therein. Any suitable solid particle can be used, depending upon the end product being fabricated. The particles can be metallic, organic/polymeric, inorganic, or composites or mixtures thereof. The particles can be of any suitable shape, including spherical, elliptical, cylindrical, fractal, etc. The particles can comprise an active agent or detectable compound as described below. For example, magnetic or paramagnetic particles or nanoparticles can be employed. The resin can have have additional ingredients solubilized, dispersed or suspended therein, including pigments, dyes, active compounds or pharmaceutical compounds, detectable compounds {e.g., fluorescent, phosphorescent, radioactive), etc., again depending upon the particular purpose of the product being fabricated,

2. Methods and Apparatus.

By thermally initiating polymerization, the LCT oligomers are cured, thereby irreversibly forming a covalently-linked polymer network, In this process, at least some of the reactive LCT oligomers are cross-linked. Cross-linking occurs in particular between the reactive termini of the aromatic backbones of the LCT oligomers. Initiating polymerization (chain extension/crosslinking) as used herein may therefore particularly refer to initiating cross-linking of the LCT oligomers, and in particular to initiating cross-linking of the backbone of the LCT oligomers.

One embodiment of the invention provides the precursor to the build region in solid particulate form, which may then be irradiated, and fresh particulate precursor provided to the build region, in like manner as employed for other materials in laser sintering. See, e.g., US Patents Nos. 6,858,816; 5,525,264; and 5,155,321, This embodiment takes advantage of the inherent physical properties of the LCT precursor resin. As LCT is a "macromonomer"— a low molecular weight, typically crystalline organic compound, it is crystalline or glassy and consequently very brittle. This brittleness lends itself to ease of grinding into a free-flowing, micron or smaller sized powder, which is ideally suited for selective laser sintering (SLS) 3D printing.

Another embodiment of a method and apparatus of the invention is schematically illustrated in Figure 1.

As shown in Figure 1, a thin (1 to several hundred micron thick) film or sheet (11) of the oligomer (the high performance polymer precursor in solid form) is fed (from the right) by a roller supply assembly (12) into a "build region" defined by a carrier (13) and light or energy source (14) {e.g., a laser such as a carbon dioxide laser). A fresh section of film is translated and held on top surface of the object being produced (15), or the "build" (center object below film). The film is fused e.g., by laser beam (dotted arrows above film and build object) into 2D pattern completing a layer of "build" on the lowering carrier (or build plate), The first layer of build is translated downwards. Another "fresh" section of film is translated into the build region (in the illustrated embodiment from right-to-left), and the foregoing steps are repeated until the fabrication of the object or article is completed. Wasted sheet material (unfused area of film) is collected by the roller take-up assembly (16) at left and recycled. A controller and associated drives and patterning elements for patterning the light or thermal energy may be provided in accordance with known techniques.

While displayed as rollers in Figure 1 , both the sheet supply assembly and the surplus sheet take-up assembly may comprise a roller, chain drive, conveyor belt, or vacuum transfer assembly, or a combination thereof.

In another embodiment of the invention, the precursors described herein may be used in liquid form for photo-polymerization as the polymerizable liquid in a "bottom up" or "top down" three-dimensional printing (or additive manufacturing) method and apparatus, including but not limited to those set forth in US Patent No. 5,236,637 to Hull.

The foregoing is illustrative of the present invention, and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

TH AT WHICH IS CLAIMED IS:

1. A process for the production of a three-dimensional object from a high performance polymer, comprising the steps of:

(a) providing a radiation source and a carrier for supporting a three dimensional object during production thereof, said radiation source and said carrier defining a build region;

(c) cross-linking said precursor in said build region with said radiation source to produce a solid polymerized region of said polymer thereon;

(e) repeating steps (b) through (d) until the production of said three-dimensional object is completed.

2. The process of claim 1, wherein said cross-linking step is a thermally cross-linking step, and said precursor is in solid form.

3. The process of claim 1, wherein said radiation source is a carbon dioxide laser, and said precursor is in the form of a solid powder or sheet.

4. The process of claim 1 to 3, wherein said high performance polymer comprises a liquid crystalline thermoset (LCT).

5. The process of claim 1 to 4, wherein said precursor comprises an ester, ester-imide, or ester-amide oligomer.

6. The process of claim 1 to 5, wherein said precursor has at least one reactive alkene- containing or alkyne-containing end-cap covalently coupled thereto.

7. The process of claim 1 to 6, wherein the said precursor comprises an oligomer that has a phenylacetylene, phenylmaleimide, or nadimide end-cap.

8. The process of claim 1 to 7, wherein said precursor is provided to said build region in solid form (e.g., as a particulate).

9. The process of claim 1 to 8, wherein said precursor is provided to said build region in the form of a continuous solid sheet or sections of a solid sheet.

10. The method of claim 1 to 9, wherein said cross-linking step is carried out by laser irradiation.

1 1. The method of claim 1 to 10, wherein said cross-linking step is carried out with patterned irradiation.

12. The method of claim 1 to 1 1, wherein said heating step is carried out by laser sintering.

13. An apparatus for forming a three-dimensional object of a high-performance polymer, comprising:

(a) an energy source;

(c) a sheet supply assembly operatively associated with said carrier and configured to advance a precursor of the high performance polymer into said build region as a solid sheet.

1 . The apparatus of claim 13, further comprising:

(d) a surplus sheet take-up assembly operatively associated with said sheet supply assembly and configured to advance unused precursor of the high performance polymer out of said build region as a solid sheet.

15. The apparatus of claim 13 to 14, further comprising:

a controller operatively associated with said carrier, said radiation source, said sheet supply assembly, and optionally said surplus sheet take-up assembly, the controller configured to advance the carrier away from the build region, and advance new solid sheet precursor into said build region.

16. The apparatus of claim 13 to 15, wherein said sheet supply assembly comprises a roller, chain drive, conveyor belt, or vacuum transfer assembly, or a combination thereof.

17. The apparatus of claim 13 to 16, wherein said surplus sheet take-up assembly comprises a roller, chain drive, conveyor belt, vacuum transfer assembly, or combination thereof.

18. The apparatus of claim 13 to 17, wherein said energy source comprises a patterned energy source.

19. The apparatus of claim 13 to 18, wherein said energy source comprises a laser.

20. The apparatus of claim 13 to 19, wherein said energy source comprises a carbon dioxide laser.