U.S. patent application number 17/645538 was filed with the patent office on 2022-04-21 for production of low density products by additive manufacturing.
The applicant listed for this patent is Carbon, Inc.. Invention is credited to Justin Poelma, Jason P. Rolland.
Application Number | 20220118689 17/645538 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-21 |
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United States Patent
Application |
20220118689 |
Kind Code |
A1 |
Poelma; Justin ; et
al. |
April 21, 2022 |
PRODUCTION OF LOW DENSITY PRODUCTS BY ADDITIVE MANUFACTURING
Abstract
Provided herein according to some embodiments is polymerizable
liquid useful for the production of a three-dimensional object by
additive manufacturing, said polymerizable liquid comprising a
mixture of: (a) at least one photopolymerizable component; (b) a
photoinitiator; (c) at least one heat polymerizable component; and
(d) heat expandable microspheres. A method of making a
three-dimensional object from such a polymerizable liquid by
additive manufacturing and objects so produced are also
provided.
Inventors: |
Poelma; Justin; (Sunnyvale,
CA) ; Rolland; Jason P.; (San Carlos, CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Carbon, Inc. |
Redwood City |
CA |
US |
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Appl. No.: |
17/645538 |
Filed: |
December 22, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16617042 |
Nov 26, 2019 |
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PCT/US2019/043883 |
Jul 29, 2019 |
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17645538 |
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62713230 |
Aug 1, 2018 |
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International
Class: |
B29C 64/124 20060101
B29C064/124; B29C 64/264 20060101 B29C064/264; B29C 64/188 20060101
B29C064/188 |
Claims
1. A polymerizable liquid useful for the production of a
three-dimensional object by additive manufacturing, said
polymerizable liquid comprising a mixture of: (a) at least one
photopolymerizable component (e.g., in an amount of from 1 or 5
percent by weight to 90 or 98 percent by weight); (b) a
photoinitiator (e.g., in an amount of from 0.05 to 10 percent by
weight); (c) at least one heat polymerizable component (e.g., in an
amount of from 2 or 5 percent by weight to 90 or 98 percent by
weight); and (d) heat expandable microspheres (e.g., in an amount
of from 1 or 2 percent by weight, to 5 or 10 percent by weight, or
more), wherein said photopolymerizable component forms on
photopolymerization a scaffold, which scaffold degrades on heating
and optionally (but in some embodiments preferably) forms a
degradation product that can polymerize with said at least one heat
polymerizable component when heated and/or microwave
irradiated.
2. The liquid of claim 1, wherein said heat polymerizable component
comprises at least one precursor to a polyurethane, polyurea, or
copolymer thereof, a silicone resin, a cyanate ester resin, or a
natural rubber.
3. The liquid of claim 1, wherein said microspheres comprise a
hollow thermally expandable shell (e.g., a thermoplastic polymer
shell), and a propellant (e.g., a low-boiling point liquid or
liquified gas such as a lower alkane), contained in said shell.
4. The liquid of claim 1, wherein the at least one
photopolymerizable component is present in an amount of from 1
percent by weight to 98 percent by weight; the photoinitiator is
present in an amount of from 0.05 to 10 percent by weight; the at
least one heat polymerizable component is present in an amount of
from 2 percent by weight to 98 percent by weight; and the heat
expandable microspheres are present in an amount of from 1 percent
by weight, to 10 percent by weight.
5. The liquid of claim 1, wherein said scaffold degrades on heating
and forms a degradation product that can polymerize with said at
least one heat polymerizable component when heated and/or microwave
irradiated.
6. The liquid of claim 3, wherein said shell comprise a
thermoplastic polymer shell.
7. The liquid of claim 3, wherein said shell comprises
polyacrylonitrile, polyvinyl dichloride (PVDC), polyvinyl chloride
(PVC), polyamide or polyacrylate.
8. The liquid of claim 3, wherein the propellant is a low-boiling
point liquid.
9. The liquid of claim 3, wherein the propellant is a liquified
gas.
10. The liquid of claim 9, wherein the liquified gas comprises
isobutane or isopentane.
11. The liquid of claim 1, wherein said heat polymerizable
component comprises at least one precursor to a polyurethane,
polyurea, or copolymer thereof.
12. The liquid of claim 1, wherein the polymerizable liquid is a
flexible polyurethane resin.
13. The liquid of claim 1, wherein the polymerizable liquid is an
elastic polyurethane resin.
14. The liquid of claim 1, wherein the polymerizable liquid further
comprises a non-reactive pigment or dye that absorbs light.
15. The liquid of claim 1, wherein the polymerizable liquid further
comprises a reactive organic diluent.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 16/617,042, filed Nov. 26, 2019, now allowed, which is a
35 U.S.C. .sctn. 371 national phase application of International
Application Serial No. PCT/US2019/043883, filed Jul. 29, 2019,
which claims the benefit of U.S. provisional patent application
Ser. No. 62/713,230, filed on Aug. 1, 2018, the disclosure of which
is incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention concerns resins formulations, and
methods of use thereof in additive manufacturing (particularly
stereolithography), and objects made from such resins and
methods.
BACKGROUND OF THE INVENTION
[0003] A group of additive manufacturing techniques sometimes
referred to as "stereolithography" create a three-dimensional
object by the sequential polymerization of a light polymerizable
resin. Such techniques may be "bottom-up" techniques, where light
is projected into the resin onto the bottom of the growing object
through a light transmissive window, or "top-down" techniques,
where light is projected onto the resin on top of the growing
object, which is then immersed downward into the pool of resin.
[0004] The recent introduction of a more rapid stereolithography
technique known as continuous liquid interface production (CLIP),
coupled with the introduction of "dual cure" resins for additive
manufacturing, has expanded the usefulness of stereolithography
from prototyping to manufacturing (see, e.g., U.S. Pat. Nos.
9,211,678; 9,205,601; and 9,216,546 to DeSimone et al.; J.
Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquid
interface production of 3D Objects, Science 347, 1349-1352 (2015);
see also Rolland et al., U.S. Pat. Nos. 9,676,963, 9,453,142 and
9,598,606).
SUMMARY OF THE INVENTION
[0005] Provided herein according to some embodiments is
polymerizable liquid useful for the production of a
three-dimensional object by additive manufacturing, said
polymerizable liquid comprising a mixture of: (a) at least one
photopolymerizable component (e.g., in an amount of from 1 or 5
percent by weight to 90 or 98 percent by weight); (b) a
photoinitiator (e.g., in an amount of from 0.05 to 10 percent by
weight); (c) at least one heat polymerizable component (e.g., in an
amount of from 2 or 5 percent by weight to 90 or 98 percent by
weight); and (d) heat expandable microspheres (e.g., in an amount
of from 1 or 2 percent by weight, to 5 or 10 percent by weight, or
more).
[0006] In some embodiments, the photopolymerizable component forms
on photopolymerization a scaffold, which scaffold degrades on
heating and optionally (but in some embodiments preferably) forms a
degradation product that can polymerize with said at least one heat
polymerizable component when heated and/or microwave
irradiated.
[0007] In some embodiments, the heat polymerizable component
comprises at least one precursor to a polyurethane, polyurea, or
copolymer thereof, a silicone resin, a cyanate ester resin, or a
natural rubber.
[0008] In some embodiments, the photopolymerizable component forms
on photopolymerization a scaffold, which scaffold softens on
heating while said heat polymerizable component polymerizes. In
some embodiments, the heat polymerizable component comprises an
epoxy resin.
[0009] In some embodiments, the microspheres comprise a hollow
thermally expandable shell (e.g., a thermoplastic polymer shell),
and a propellant (e.g., a low-boiling point liquid or liquified gas
such as a lower alkane), contained in said shell.
[0010] Also provided is a method of making a three-dimensional
object, comprising: (a) producing an intermediate object from a
polymerizable liquid as taught herein by additive manufacturing
(e.g., by bottom-up stereolithography, such as by continuous liquid
interface production); (b) optionally cleaning said object (e.g.,
by washing, spinning, etc.); and then (c) heating and/or microwave
irradiating said object for a time and at a temperature sufficient
to expand said microspheres, further cure said object, and form
said three-dimensional object. In some embodiments, the
intermediate object comprises a polymer scaffold produced by the
photopolymerization of said photopolymerizable component; and
wherein said polymer scaffold softens and/or degrades during said
heating step, and optionally (but in some embodiments preferably)
forms a degradation product that in turn reacts with said at least
one heat polymerizable component to form said object.
[0011] In some embodiments, the heating and/or microwave
irradiating step is carried out under conditions in which the
modulus of elasticity of said object decreases during at least a
portion of said heating and/or microwave irradiating step.
[0012] In some embodiments, the volume of said object is increased
by at least 5, 10, or 20 percent by said heating and/or microwave
irradiating step.
[0013] In some embodiments, the object comprises a regular or
irregular open-cell lattice.
[0014] In some embodiments, the object comprises a cushion, shock
absorber, thermal insulator, or electric insulator.
[0015] In some embodiments, the object is rigid, flexible, or
elastic.
[0016] In some embodiments, the object is comprised of
polyurethane, silicone, or epoxy.
[0017] Further provided is an object produced by a method or liquid
as taught herein.
[0018] In some embodiments, the object floats on water at a
temperature of 25 degrees Celsius and a pressure of 1 bar.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 presents a graph of tensile stress versus strain of
specimens produced as described in Examples 1 and 2. The specimens
all showed similar, unique yield behaviors, making them highly
suitable for applications such as cushions and other impact
absorbing materials. FIG. 2 is a photograph showing four lattice
structures produced by stereolithography and subsequent heat cure
with a dual cure resin.
[0020] FIG. 3 is a photograph showing a lattice structure produced
by stereolithography and subsequent heat cure with a dual cure
resin.
[0021] FIG. 4 is a photograph showing lattice structures produced
by stereolithography and subsequent heat cure of the dual cure
resin FPU with and without 3 wt % of microballoons.
[0022] There was 20% bulk expansion (printed cube), and 23%
expansion of lattice dimensions.
[0023] FIG. 5A-FIG. 5D present graphs showing a comparison of
expanded versus non-expanded lattice performance in FPU and EPU41
resins.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0024] 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.
[0025] 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.
[0026] As used herein, the term "and/or" includes any and all
possible combinations of one or more of the associated listed
items, as well as the lack of combinations when interpreted in the
alternative ("or").
[0027] 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.
1. Polymerizable Liquids (Resins).
[0028] Resins. Dual cure additive manufacturing resins are
described in, for example, Rolland et al., U.S. Pat. Nos.
9,676,963; 9,598,606; and 9,453,142, and in Wu et al., US Patent
Application Pub. No. US2017/0260418, the disclosures of which are
incorporated herein by reference. Additional resins are described
in, for example, J. Cushin et al., WO 2017/04438, which is also
incorporated by reference herein.
[0029] Example dual cure resins into which microspheres can be
added as described herein include, but are not limited to, Carbon
Inc. EPU 40, EPU 41, FPU, RPU 70, SIL 30, and EPX 82 resins, all
available from Carbon Inc., 1089 Mills Way, Redwood City, Calif.
94063 USA.
[0030] Microspheres. Heat expandable microspheres (sometimes also
referred to as "microballoons") are known and described in, for
example, U.S. Pat. Nos. 10,030,115 and 10,023,712 (both to
Matsumoto), U.S. Pat. Nos. 9,902,829, 9,062,170, and 8,388,809 (all
to Akzo Nobel) and U.S. Pat. No. 10,029,550 (to 3M), U.S. Pat. No.
3,615,972 (to Dow), and others. The disclosures of all US Patent
references cited herein are incorporated by reference herein in
their entirety.
[0031] As noted in U.S. Pat. No. 10,029,550, such microspheres
expand upon heating and include in particular expandable polymeric
microspheres that include a polymer shell and a core material in
the form of a gas, liquid or combination thereof that expands upon
heating. An expandable microsphere is one where the shell can
initially be expanded or further expanded without breaking.
Microballoons or microspheres are approximately spherical hollow
bodies having an elastic and thermoplastic polymer shell.
Accordingly, they are also referred to as expandable polymeric
microspheres or as hollow microbeads. Microballoons are filled with
low-boiling liquids or with liquefied gas. Shell materials used
include more particularly polyacrylonitrile, polyvinyl dichloride
(PVDC), polyvinyl chloride (PVC), polyamides or polyacrylates.
Suitable low-boiling liquids are, more particularly, hydrocarbons
of the lower alkanes, for example isobutane or isopentane, which
are enclosed as liquefied gas under pressure in the polymer
shell.
[0032] Action on the microspheres--more particularly by supply of
heat or generation of heat, as for example by ultra-sound or
microwave radiation--causes, first, a softening of the outer
polymer shell, while at the same time the liquid blowing gas
present in the shell undergoes transitions of its gaseous state. At
a particular pairing of pressure and temperature the microspheres
undergo irreversible expansion and expand three-dimensionally. The
expansion ends when the internal pressure equals the external
pressure. Since the polymeric shell is maintained, a closed-celled
foam is achieved in this way.
[0033] A large number of types of micro spheres are available
commercially, such as, for example, from Akzo Nobel, the EXPANCELTM
DU (dry unexpanded) products, which differ essentially in their
size (6 to 45 .mu.m in diameter in the unexpanded state) and in the
starting temperature they require for expansion (75 to 220 degrees
C.).
[0034] Unexpanded types of microballoons are also available in the
form of an aqueous dispersion, with a solids fraction or
microballoon fraction of around 40% to 45% by weight, and also in
the form of polymer-bound microballoons (masterbatches), for
example in ethylene-vinyl acetate, with a microballoon
concentration of around 65% by weight. Obtainable, furthermore, are
what are called microballoon slurry systems, in which the
microballoons are present in the form of an aqueous dispersion with
a solids fraction of 60% to 80% by weight. The microballoon
dispersions, the microballoon slurries, and the masterbatches, like
the DU products, can be used in the process described herein.
[0035] Additional resin ingredients. The liquid resin or
polymerizable material can have (among other things) 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
nonconductive, semi-conductive, or conductive (including metallic
and non-metallic or polymer conductors); and the particles can be
magnetic, ferromagnetic, paramagnetic, or nonmagnetic. The
particles can be of any suitable shape, including spherical,
elliptical, cylindrical, etc. The particles can be of any suitable
size (for example, ranging from 1 nm to 20 .mu.m average
diameter).
[0036] The particles can comprise an active agent or detectable
compound as described below, though these may also be provided
dissolved or solubilized in the liquid resin as also discussed
below. For example, magnetic or paramagnetic particles or
nanoparticles can be employed.
[0037] The liquid resin can have additional ingredients solubilized
therein, including pigments, dyes, diluents, active compounds or
pharmaceutical compounds, detectable compounds (e.g., fluorescent,
phosphorescent, radioactive), etc., again depending upon the
particular purpose of the product being fabricated. Examples of
such additional ingredients include, but are not limited to,
proteins, peptides, nucleic acids (DNA, RNA) such as siRNA, sugars,
small organic compounds (drugs and drug-like compounds), etc.,
including combinations thereof.
[0038] Dyes/non-reactive light absorbers. In some embodiments,
polymerizable liquids for carrying out the present invention
include a non-reactive pigment or dye that absorbs light,
particularly UV light. Suitable examples of such light absorbers
include, but are not limited to:
[0039] (i) titanium dioxide (e.g., included in an amount of from
0.05 or 0.1 to 1 or 5 percent by weight), (ii) carbon black (e.g.,
included in an amount of from 0.05 or 0.1 to 1 or 5 percent by
weight), and/or (iii) an organic ultraviolet light absorber such as
a hydroxybenzophenone, hydroxyphenylbenzotriazole, oxanilide,
benzophenone, thioxanthone, hydroxyphenyltriazine, and/or
benzotriazole ultraviolet light absorber (e.g., Mayzo BLS.RTM.
1326) (e.g., included in an amount of 0.001 or 0.005 to 1, 2 or 4
percent by weight). Examples of suitable organic ultraviolet light
absorbers include, but are not limited to, those described in U.S.
Pat. Nos. 3,213,058; 6,916,867; 7,157,586; and 7,695,643, the
disclosures of which are incorporated herein by reference.
[0040] Fillers. Any suitable filler may be used in connection with
the present invention, depending on the properties desired in the
part or object to be made. Thus, fillers may be solid or liquid,
organic or inorganic, and may include reactive and non-reactive
rubbers: siloxanes, acrylonitrile-butadiene rubbers; reactive and
non-reactive thermoplastics (including but not limited to:
poly(ether imides), maleimide-styrene terpolymers, polyarylates,
polysulfones and polyethersulfones, etc.) inorganic fillers such as
silicates (such as talc, clays, silica, mica), glass, carbon
nanotubes, graphene, cellulose nanocrystals, etc., including
combinations of all of the foregoing. Suitable fillers include
tougheners, such as core-shell rubbers, as discussed below.
[0041] Tougheners. One or more polymeric and/or inorganic
tougheners can be used as a filler in the present invention. The
toughener may be uniformly distributed in the form of particles in
the cured product. The particles could be less than 5 microns
(.mu.m) in diameter. Such tougheners include, but are not limited
to, those formed from elastomers, branched polymers, hyperbranched
polymers, dendrimers, rubbery polymers, rubbery copolymers, block
copolymers, core-shell particles, oxides or inorganic materials
such as clay, polyhedral oligomeric silsesquioxanes (POSS),
carbonaceous materials (e.g., carbon black, carbon nanotubes,
carbon nanofibers, fullerenes), ceramics and silicon carbides, with
or without surface modification or functionalization.
[0042] Core-shell rubbers. Core-shell rubbers are particulate
materials (particles) having a rubbery core. Such materials are
known and described in, for example, US Patent Application
Publication No. 20150184039, as well as US Patent Application
Publication No. 20150240113, and U.S. Pat. Nos. 6,861,475,
7,625,977, 7,642,316, 8,088,245, and elsewhere. In some
embodiments, the core-shell rubber particles are nanoparticles
(i.e., having an average particle size of less than 1000 nanometers
(nm)). Generally, the average particle size of the core-shell
rubber nanoparticles is less than 500 nm, e.g., less than 300 nm,
less than 200 nm, less than 100 nm, or even less than 50 nm.
Typically, such particles are spherical, so the particle size is
the diameter; however, if the particles are not spherical, the
particle size is defined as the longest dimension of the particle.
Suitable core-shell rubbers include, but are not limited to, those
sold by Kaneka Corporation under the designation Kaneka Kane Ace,
including the Kaneka Kane Ace 15 and 120 series of products,
including Kaneka Kane Ace MX 120, Kaneka
[0043] Kane Ace MX 153, Kaneka Kane Ace MX 154, Kaneka Kane Ace MX
156, Kaneka Kane Ace MX170, Kaneka Kane Ace MX 257, and Kaneka Kane
Ace MX 120 core-shell rubber dispersions, and mixtures thereof.
[0044] Organic diluents. In some embodiments, diluents for use in
the present invention are preferably reactive organic diluents;
that is, diluents that will degrade, isomerize, cross-react, or
polymerize, with themselves or a light polymerizable component,
during the additive manufacturing step. In general, the diluent(s)
are included in an amount sufficient to reduce the viscosity of the
polymerizable liquid or resin (e.g., to not more than 15,000,
10,000, 6,000, 5,000, 4,000, or 3,000 centipoise at 25 degrees
Centigrade). Suitable examples of diluents include, but are not
limited to, N,N-dimethylacrylamide, N-vinyl-2-pyrrolidone, and
N-vinyl formamide, or a mixture if two or more thereof. The diluent
may be included in the polymerizable liquid in any suitable amount,
typically from 1, 5 or 10 percent by weight, up to about 30 or 40
percent by weight, or more. Accelerators. In some embodiments, the
liquid may include a deoxygenating compound as an accelerator of
stereolithography (particularly CLIP). An example of a suitable
such accelerator is triphenylphosphine.
2. Production by Additive Manufacturing.
[0045] Polymerizable liquids or resins as described herein may be
used to make three-dimensional objects, in a "light" cure
(typically by additive manufacturing) which in some embodiments
generates a "green" intermediate object, followed in some
embodiments by a second (typically heat) cure of that intermediate
object.
[0046] Techniques for additive manufacturing are known. Suitable
techniques include bottom-up or top-down additive manufacturing,
generally known as stereolithography. Such methods are known and
described in, for example, U.S. Pat. No. 5,236,637 to Hull, U.S.
Pat. Nos. 5,391,072 and 5,529,473 to Lawton, U.S. Pat. No.
7,438,846 to John, U.S. Pat. No. 7,892,474 to Shkolnik, U.S. Pat.
No. 8,110,135 to El-Siblani, U.S. Patent Application Publication
No. 2013/0292862 to Joyce, and US Patent Application Publication
No. 2013/0295212 to Chen et al. The disclosures of these patents
and applications are incorporated by reference herein in their
entirety.
[0047] In some embodiments, the intermediate object is formed by
continuous liquid interface production (CLIP). CLIP is known and
described in, for example, U.S. Pat. Nos. 9,211,678, 9,205,601,
9,216,546, and in J. Tumbleston, D. Shirvanyants, N. Ermoshkin et
al., Continuous liquid interface production of 3D Objects, Science
347, 1349-1352 (2015). See also R. Janusziewcz et al., Layerless
fabrication with continuous liquid interface production, Proc.
Natl. Acad. Sci. USA 113, 11703-11708 (2016). In some embodiments,
CLIP employs features of a bottom-up three-dimensional fabrication
as described above, but the irradiating and/or said advancing steps
are carried out while also concurrently maintaining a stable or
persistent liquid interface between the growing object and the
build surface or window, such as by: (i) continuously maintaining a
dead zone of polymerizable liquid in contact with said build
surface, and (ii) continuously maintaining a gradient of
polymerization zone (such as an active surface) between the dead
zone and the solid polymer and in contact with each thereof, the
gradient of polymerization zone comprising the first component in
partially-cured form. In some embodiments of CLIP, the optically
transparent member comprises a semipermeable member (e.g., a
fluoropolymer), and the continuously maintaining a dead zone is
carried out by feeding an inhibitor of polymerization through the
optically transparent member, thereby creating a gradient of
inhibitor in the dead zone and optionally in at least a portion of
the gradient of polymerization zone. Other approaches for carrying
out CLIP that can be used in the present invention and potentially
obviate the need for a semipermeable "window" or window structure
include utilizing a liquid interface comprising an immiscible
liquid (see L. Robeson et al., WO 2015/164234), generating oxygen
as an inhibitor by electrolysis (see I. Craven et al., WO
2016/133759), and incorporating magnetically positionable particles
to which the photoactivator is coupled into the polymerizable
liquid (see J. Rolland, WO 2016/145182).
[0048] Other examples of methods and apparatus for carrying out
particular embodiments of CLIP include, but are not limited to:
Batchelder et al., US Patent Application Pub. No. US 2017/0129169;
Sun and Lichkus, US Patent Application Pub. No. US 2016/0288376;
Willis et al., US Patent Application Pub. No. US 2015/0360419; Lin
et al., US Patent Application Pub. No. US 2015/0331402; D.
Castanon, US Patent Application Pub. No. US 2017/0129167; B.
Feller, US Pat App. Pub. No. US 2018/0243976; M. Panzer and J.
Tumbleston, US Pat App Pub. No. US 2018/0126630 (published May 10,
2018); and K. Willis and B. Adzima, US Pat App Pub. No. US
2018/0290374 (Oct. 11, 2018).
[0049] After an intermediate three-dimensional object is formed, it
is optionally cleaned, optionally dried (e.g., air dried) and/or
rinsed (in any sequence). It is then further cured, preferably by
heating (although further curing may in some embodiments be
concurrent with the first cure, or may be by different mechanisms
such as contacting to water, as described in U.S. Pat. No.
9,453,142 to Rolland et al.).
3. Cleaning or Washing.
[0050] Objects as described above can be cleaned in any suitable
apparatus, in some embodiments with a wash liquid as described
herein, and in other embodiments by wiping (with an absorbent, air
blade, etc.) spinning, or variations thereof.
[0051] Wash liquids that may be used to carry out the present
invention include, but are not limited to, water, organic solvents,
and combinations thereof (e.g., combined as co-solvents),
optionally containing additional ingredients such as surfactants,
chelants (ligands), enzymes, borax, dyes or colorants, fragrances,
etc., including combinations thereof. The wash liquid may be in any
suitable form, such as a solution, emulsion, dispersion, etc.
[0052] In some preferred embodiments, where the residual resin has
a boiling point of at least 90 or 100.degree. C. (e.g., up to 250
or 300.degree. C., or more), the wash liquid has a boiling point of
at least 30.degree. C., but not more than 80 or 90.degree. C.
Boiling points are given herein for a pressure of 1 bar or 1
atmosphere.
[0053] In some embodiments, the wash liquid consists of a 50:50
(volume:volume) solution of water and an alcohol organic solvent
such as isopropanol (2-propanol).
[0054] Examples of hydrofluorocarbon solvents that may be used to
carry out the present invention include, but are not limited to,
1,1,1,2,3,4,4,5,5,5-decafluoropentane (Vertrel.RTM. XF, DuPont.TM.
Chemours), 1,1,1,3,3-Pentafluoropropane,
1,1,1,3,3-Pentalluorobutane, etc. Examples of
hydrochlorofluorocarbon solvents that may be used to carry out the
present invention include, but are not limited to,
3,3-Dichloro-1,1,1,2,2-pentalluoropropane,
3-Dichloro-1,1,2,2,3-pentafluoropropane,
1,1-Dichloro-1-fluoroethane, etc., including mixtures thereof.
[0055] Examples of hydrofluoroether solvents that, may be used to
carry out the present invention include, but are not limited to,
methyl nonafluorobutyl ether (HFE-7100), methyl nonafluoroisobutyl
ether (HFE-7100), ethyl nonatluorobutyl ether (HFE-7200), ethyl
nonafluoroisobutyl ether (HFE-7200),
1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, etc.,
including mixtures thereof. Commercially available examples of this
solvent include Novec 7100 (3M), Novec 7200 (3M).
[0056] Examples of volatile methylsiloxane solvents that may be
used to carry out the present invention include, but are not
limited to, hexamethyldisiloxane (OS-10, Dow Corning),
octamethyltrisiloxane (OS-20, Dow Corning), decamethyltetrasiloxane
(OS-30, Dow Corning), etc., including mixtures thereof.
[0057] Other siloxane solvents (e.g., NAVSOLVE.TM. solvent) that
may be used to carry out the present invention include but are not
limited to those set forth in U.S. Pat. No. 7,897,558.
[0058] In some embodiments, the wash liquid comprises an azeotropic
mixture comprising, consisting of, or consisting essentially of a
first organic solvent (e.g., a hydrofluorocarbon solvent, a
hydrochlorofluorocarbon solvent, a hydrofluoroether solvent, a
methylsiloxane solvent, or a combination thereof; e.g., in an
amount of from 80 or 85 to 99 percent by weight) and a second
organic solvent (e.g., a C1-C4 or Co alcohol such as methanol,
ethanol, isopropanol, tert-butanol, etc.; e.g., in an amount of
from 1 to 15 or 20 percent by weight). Additional ingredients such
as surfactants or chelants may optionally be included. In some
embodiments, the azeotropic wash liquid may provide superior
cleaning properties, and/or enhanced recyclability, of the wash
liquid. Additional examples of suitable azeotropic wash liquids
include, but are not limited to, those set forth in U.S. Pat. Nos.
6,008,179; 6,426,327; 6,753,304; 6,288,018; 6,646,020; 6,699,829;
5,824,634; 5,196,137; 6,689,734; and 5,773,403, the disclosures of
which are incorporated by reference herein in their entirety.
[0059] When the wash liquid includes ingredients that are not
desired for carrying into the further curing step, in some
embodiments the initial wash with the wash liquid can be followed
with a further rinsing step with a rinse liquid, such as water
(e.g., distilled and/or deionized water), or a mixture of water and
an alcohol such as isopropanol.
[0060] 4. Further Curing.
[0061] After washing, the object is in some embodiments further
cured, preferably by heating or baking.
[0062] Heating may be active heating (e.g., in an oven, such as an
electric, gas, solar oven or microwave oven, heated bath, or
combination thereof), or passive heating (e.g., at ambient (room)
temperature). Active heating will generally be more rapid than
passive heating and in some embodiments is preferred, but passive
heating--such as simply maintaining the intermediate at ambient
temperature for a sufficient time to effect further cure--is in
some embodiments preferred.
[0063] In some embodiments, the heating step is carried out at at
least a first (oven) temperature and a second (oven) temperature,
with the first temperature greater than ambient temperature, the
second temperature greater than the first temperature, and the
second temperature less than 300.degree. C. (e.g., with ramped or
step-wise increases between ambient temperature and the first
temperature, and/or between the first temperature and the second
temperature).
[0064] For example, the intermediate may be heated in a stepwise
manner at a first temperature of about 70.degree. C. to about
150.degree. C., and then at a second temperature of about
150.degree. C. to 200 or 250.degree. C., with the duration of each
heating depending on the size, shape, and/or thickness of the
intermediate. In another embodiment, the intermediate may be cured
by a ramped heating schedule, with the temperature ramped from
ambient temperature through a temperature of 70 to 150.degree. C.,
and up to a final (oven) temperature of 250 or 300.degree. C., at a
change in heating rate of 0.5.degree. C. per minute, to 5.degree.
C. per minute. (See, e.g., U.S. Pat. No. 4,785,075).
[0065] In some embodiments, the heating step is carried out in an
inert gas atmosphere. Inert atmosphere ovens are known, and
generally employ an atmosphere enriched in nitrogen, argon, or
carbon dioxide in the oven chamber. Suitable examples include but
are not limited to those available from Grieve Corporation, 500
Hart Road Round Lake, Ill. 60073-2898 USA, Davron Technologies,
4563 Pinnacle Lane, Chattanooga, Tenn. 37415 USA, Despatch Thermal
Processing Technology, 8860 207th Street, Minneapolis, Minn. 55044
USA, and others.
[0066] In other embodiments, the heating step is carried out in an
inert liquid bath. Suitable inert liquids may be aqueous liquids
(i.e., pure water, salt solutions, etc.), organic liquids (e.g.,
mineral oil, fluorinated, perfluorinated, and polysiloxane organic
compounds such as perfluorohexane,
perfluoro(2-butyl-tetrahydrofurane), perfluorotripentylamine, etc.
(commercially available as PERFLUORINERT.RTM. inert liquids from 3M
Company)), and mixtures thereof. These inert liquids can be
deoxygenated if necessary, such as by bubbling an inert gas such as
nitrogen through the liquid, by boiling the inert liquid, by mixing
oxygen-scavenging agents with the inert liquid medium (or
contacting them to one another), etc., including combinations
thereof (see, e.g., U.S. Pat. No. 5,506,007).
[0067] In some embodiments, the further curing or heating step
(whether carried out in a liquid or gas fluid) is carried out at an
elevated pressure (e.g., elevated sufficiently to reduce
volatilization or out-gassing of residual monomers, prepolymers,
chain extenders, and/or reactive diluents, etc.). Suitable pressure
ranges are from 10 or 15 psi to 70 or 100 psi, or more.
5. Objects Made.
[0068] The present invention can be implemented for the production
of any object by additive manufacturing.
[0069] In some embodiments, where the objects are made from a resin
prone to shrinking, the microballoons can be added to offset
shrinking that may otherwise occur.
[0070] In other embodiments, the objects can be additively produced
at a smaller size than intended (e.g., to speed the additive
manufacturing step), and then expanded to the intended final size
during the further curing step.
[0071] In some embodiments, the resins of the invention may be used
to produce heat insulators and heat insulating objects.
[0072] In some embodiments, the resins are useful for the
production of low-k dielectric objects or electrical insulators,
such as for use as packaging in the semiconductor industry.
[0073] In some embodiments, after the further curing step, the
object made is dipped or immersed in a liquid such as a penetrant
liquid, so that the pores may fill with another material such as a
dye.
[0074] In some embodiments, prior to the further curing step, the
intermediate object is contacted in a fixturing apparatus) to
another pre-formed object, and the further curing step carried out
with the intermediate object contacting the pre-formed object, to
produce a composite object. The expansion of the intermediate
object by the microballoons may aid in joining the two objects
together.
[0075] The resins of the present invention are useful for making
objects that comprise lattices, including rigid lattices where no
recovery after impact is necessary (e.g., impact absorbers such as
in automotive bumpers and body panels, helmets and helmet inserts
such as in bicycling and motorcycling helmets which are typically
discarded after a single impact, etc.). In some embodiments, the
use of the microballoons in the resins as taught herein may
increase the stiffness of lattices compared to non-expanded
lattices with approximately the same mass and overall
dimensions.
[0076] As products made from resins of the present invention may
have a fine textured or "sand paper" feel, they can be used to
produce objects that have a matte finish, and/or to produce an
object having an antislip or gripping surface.
[0077] The foregoing is illustrated in greater detail in the
following non-limiting Examples.
EXAMPLE 1
Loading of a Flexible Polyurethane Dual Cure Resin with
Microspheres and Production of "Green" Intermediate Object
[0078] Dual-cure resin additive manufacturing resin FPU 50,
commercially available from
[0079] Carbon, Inc., 1089 Mills Way, Redwood City, CA 94063 USA,
FPU 50, was dispensed into a mixing cup according to standard
operating procedures. EXPANCELTM DU microspheres (461 DU 40) were
then added to the Part A+B resin mixture to obtain a total loading
of 3 wt %. The DU particles were dispersed with a 4-propeller
mixing blade for 5 minutes at 250-300 rpm. The material was then
3d-printed with Carbon's DLS/CLIP technology to obtain a 3d
part.
EXAMPLE 2
Further curing of Green Intermediate Object and Expansion of
Microspheres
[0080] The "green" object produced in Example 1 was thermally cured
in an oven at 120 degrees Centigrade for 12h according to the FPU
50 operating procedure. During this baking step, the expanding
microspheres are activated causing a decrease in part density and
volume expansion. The final parts have a density of about 0.8 g/cc
and volume expansion 20-25%--A substantial change from the same
resin without the microspheres (density of about 1.05 g/cc).
TABLE-US-00001 TABLE 1 Flexible polyurethane resin with 3 wt %
microspheres and product properties Parts by weight FPU 50 97 461
DU 40 3 Tensile Strength (MPa) 20 Tensile Modulus (MPa) 620
EXAMPLE 3
Tensile Properties
[0081] Six expanded tensile specimens were produced in like manner
as described in Examples 1-2 above and their stress-strain
properties determined in accordance with standard techniques. As
shown in FIG. 1, the specimens all showed similar, unique yield
behaviors, making them highly suitable for applications such as
cushions and other impact absorbing materials.
EXAMPLE 4
Failure of Expansion of Microspheres in Product produced with a
Single Cure Resin
[0082] A conventional single-cure (light cured) urethane
methacrylate resin, UMA 90, available from Carbon Inc., was loaded
with microspheres in like manner as in Example 1, products produced
in like manner, and the products heated in like manner. The
microspheres, however, did not expand, and the resulting product
did not show a decrease in density. Without wishing to be bound to
any specific theory of the invention, we hypothesize that the
highly crosslinked network typical of single-cure photopolymer
resins, that cannot rearrange or undergo secondary chemistry,
prevents the expansion of the particles.
EXAMPLE 5
[0083] Loading of an Elastic Polyurethane Dual Cure Resin with
Microspheres In this Example, the microspheres were added to Carbon
Inc. elastic polyurethane dual cure resin EPU 41, a part produced,
and the part baked, according to the procedure described in Example
1 above. Results are given in Table 2 below.
TABLE-US-00002 TABLE 2 Elastic polyurethane resin with 3 wt %
microspheres and product properties. Parts by weight EPU 41 97 461
DU 40 3 Density 0.82 g/cc Volumetric Expansion 23%
EXAMPLE 6
Loading of an Epoxy Dual Cure Resin with Microspheres and
Production of Object
[0084] This example is carried out in like manner as Examples 1-2
above, except that an epoxy dual cure resin, EPX 82, commercially
available from Carbon Inc., is used instead of FPU 50, and additive
production and further curing is carried out in accordance with
standard techniques for the EPX 82 resin.
[0085] While objects made from the EPX 82 resin do not have a
rearrangabie polymer network like that provided by the FPU and RPU
resins, Dynamic Mechanical Analysis (DMA) reveals that the "green"
part is still affected by temperature, with the modulus dropping to
approximately the same range as that of the FPU and. RPU resins,
thereby indicating that the microballoons can expand during the
heat curing step.
[0086] Initial experiments with the microballoons in EPX 82 resin
did not produce visible expansion. However, altering conditions
such as the heating temperature range and time may result in
sufficient softening to allow the microballoon expansion of the
produced part considering the drop in modulus noted above upon
heating.
EXAMPLE 7
Production of Lattice Objects
[0087] Dual cure resins as described above are useful for the
production of objects comprised of lattices, such as lattices shown
in FIG. 2 and FIG. 3.
[0088] While lattices shown in FIG. 2 and FIG. 3 are formed by
stereolithography and subsequent heat cure from resins that do not
contain thermally expandable microspheres, expanded versions of the
lattices are produced by including microspheres as described
herein, and then forming the lattice objects by stereolithography,
and subsequent heat curing, in accordance with known
techniques.
[0089] For example, the image in FIG. 4 shows FPU with and without
3 wt % of microballoons. Samples were baked according to the FPU
curing schedule --12 h, 120.degree. C. There was 20% bulk expansion
(printed cube), and 23% expansion of lattice dimensions.
[0090] As shown in the graphs of FIG. 5A-5D, the addition of the
microballoons generally increases the stiffness of lattices
compared to non-expanded lattices with approximately the same mass
and overall dimensions. This effect may be attributed to the
increase in node size and strut diameter as the microballoons
expand during baking. These properties may be particularly
advantageous in applications where high-stiffness, low-weight
lattices are preferred (e.g. foam replacements, midsoles, helmets,
seat cushioning).
[0091] 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.
* * * * *