U.S. patent application number 15/549191 was filed with the patent office on 2018-02-01 for digitally-controlled three-dimensional printing of polymerizable materials.
The applicant listed for this patent is Stratasys Ltd.. Invention is credited to Shai HIRSCH, Lev KUNO, Eynat MATZNER, Ira YUDOVIN-FARBER.
Application Number | 20180029291 15/549191 |
Document ID | / |
Family ID | 56563561 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180029291 |
Kind Code |
A1 |
MATZNER; Eynat ; et
al. |
February 1, 2018 |
DIGITALLY-CONTROLLED THREE-DIMENSIONAL PRINTING OF POLYMERIZABLE
MATERIALS
Abstract
Provided are methods of fabricating an object, effected by
jetting two or more different compositions, each containing a
different material or mixture of materials, which, when contacted
on a receiving medium, undergo a chemical reaction therebetween to
form the building material. The chemical composition of the formed
building material is dictated by a ratio of the number of voxels of
each composition in a voxel block. Systems for executing the
methods, and printed objects obtained thereby are also
provided.
Inventors: |
MATZNER; Eynat; (Adi,
IL) ; YUDOVIN-FARBER; Ira; (Rehovot, IL) ;
HIRSCH; Shai; (Rehovot, IL) ; KUNO; Lev;
(Tzur-Hadassah, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stratasys Ltd. |
Rehovot |
|
IL |
|
|
Family ID: |
56563561 |
Appl. No.: |
15/549191 |
Filed: |
February 5, 2016 |
PCT Filed: |
February 5, 2016 |
PCT NO: |
PCT/IL2016/050135 |
371 Date: |
August 7, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62112277 |
Feb 5, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 10/00 20141201;
B33Y 50/02 20141201; B33Y 30/00 20141201; B29C 64/393 20170801;
B29C 64/112 20170801; C09D 11/30 20130101; C09D 11/101 20130101;
B41J 2/01 20130101; B33Y 70/00 20141201 |
International
Class: |
B29C 64/112 20060101
B29C064/112; B41J 2/01 20060101 B41J002/01; B33Y 70/00 20060101
B33Y070/00; B33Y 10/00 20060101 B33Y010/00; B33Y 30/00 20060101
B33Y030/00; C09D 11/30 20060101 C09D011/30; B29C 64/393 20060101
B29C064/393 |
Claims
1. A method of fabricating an object, the method comprising:
receiving three-dimensional printing data corresponding to the
shape of the object; selecting a ratio between a first composition
and a second composition, wherein said first composition comprises
a first material and said second composition comprises a second
material, said first and second materials undergoing a chemical
reaction with one another so as to form a building material when
exposed to a curing energy; dispensing droplets of said first and
said second compositions in layers, on a receiving medium, using at
least two different inkjet printing heads, according to said
printing data; wherein for at least one region of the object, said
dispensing of said droplets is selected to form voxel blocks,
wherein, for each block, a ratio between a number of voxels of said
first composition in said block and a number of voxels of said
second composition in said block corresponds to said selected
ratio.
2-7. (canceled)
8. The method of claim 1, further comprising exposing the dispensed
layers to said curing energy.
9-13. (canceled)
14. The method of claim 1, wherein at least one of said first and
second compositions comprises an additional material for inducing a
chemical reaction between said first and second materials.
15. The method of claim 1, wherein said first material is a first
curable material.
16. The method of claim 15, wherein said second material is
selected capable of modifying a chemical, physical and/or
mechanical property of a modeling material formed of said first
curable material, upon chemically reacting with said first curable
material and exposure to said curing energy, and wherein a degree
of said modifying is determined by selecting said ratio.
17. The method of claim 15, wherein said second material is a
second curable material.
18. The method of claim 17, wherein said first material comprises a
first plurality of monomers and said second material comprises a
second plurality of monomers being chemically different from said
first plurality of monomers, and wherein said first and second
pluralities of monomers chemically react with one another upon
exposure to said curing energy.
19. The method of claim 15, wherein said second material affects
cross-linking of a polymeric material formed of said first curable
material.
20. The method of claim 15, wherein said second material promotes a
polymerization of said first curable material upon exposure to said
curing energy, while forming a part of a modeling material formed
by curing said first curable material.
21. The method of claim 20, wherein said first curable material is
a monomer that is polymerizable by an anionic ring opening
polymerization.
22-23. (canceled)
24. The method of claim 21, wherein said first curable material is
a caprolactam.
25. The method of claim 24, wherein said second material comprises
at least one material that promotes said anionic ring opening
polymerization while forming a part of said modeling material
formed by curing said caprolactam.
26. The method of claim 25, wherein said second material comprises
a moiety that chemically interacts with said caprolactam during
said polymerization.
27. The method of claim 25, wherein said second material further
comprises an additional moiety which is such that when forming a
part of a modeling material formed of said caprolactam, a chemical,
physical and/or mechanical property of said modeling material is
modified.
28. The method of claim 27, wherein said additional moiety
comprises an elastomeric moiety, and optically-active moiety, a
light-absorbing moiety, a hydrophobic moiety, a hydrophilic moiety
and/or a chemically-reactive moiety.
29. The method of claim 27, wherein said second material is
represented by the general Formula I: ##STR00013## wherein: A is
said additional moiety; R is N-acyl lactam; and n is a positive
integer.
30. The method of claim 29, wherein said second material comprises
at least two N-acyl lactam groups.
31. The method of claim 24, wherein said first composition further
comprises a catalyst for inducing polymerization of said
caprolactam.
32. (canceled)
33. The method of claim 15, wherein said second composition is
devoid of said first curable material.
34-51. (canceled)
52. The method of claim 30, wherein said second material is
represented by Formula II: ##STR00014## wherein: A is said
additional moiety; L is absent or is a linking moiety; and A' is
absent or is another additional moiety, being said or different
from said A.
53. The method of claim 52, wherein A' comprises at least one
N-acyl lactam moiety.
54-56. (canceled)
57. A system for three-dimensional printing, comprising: a
plurality of inkjet printing heads, each having a plurality of
separated nozzles; a user interface for receiving a selected ratio
between a first composition and a second composition, wherein said
first composition comprises a first material and said second
composition comprises a second material, said first and second
materials undergoing a chemical reaction with one another so as to
form a modeling material when contacted and exposed to a curing
energy; and a controller configured for controlling two of said
inkjet printing heads to respectively dispense droplets of said
first and second compositions in layers, such as to print a
three-dimensional object, wherein said controller is configured to
form voxel blocks, wherein, for each block, a ratio between a
number of voxels of said first composition in said block and a
number of voxels of said second composition in said block
corresponds to said selected ratio.
58. (canceled)
Description
FIELD AND BACKGROUND OF THE INVENTION
[0001] The present invention, in some embodiments thereof, relates
to three-dimensional printing and, more particularly, but not
exclusively, to methods of performing three-dimensional inkjet
printing, to compositions utilized in these methods and to objects
obtained by these methods.
[0002] Three-dimensional (3D) inkjet printing is a known process
for building three dimensional objects by selectively jetting
chemical compositions, for example, polymerizable compositions, via
ink-jet printing head nozzles, onto a printing tray in consecutive
layers, according to pre-determined image data. 3D inkjet printing
is performed by a layer by layer inkjet deposition of chemical
compositions. Thus, a chemical composition is dispensed in droplets
from a dispensing head having a set of nozzles to form layers on a
receiving medium. The layers may then be cured or solidified using
a suitable methodology, to form solidified or partially solidified
layers of the building material.
[0003] The chemical compositions used for forming the building
material may be initially liquid (e.g., when jetted through the
inkjet printing head nozzles), and subsequently hardened (cured or
solidified) to form the required layer shape. The hardening may be
effected, for example, by exposing the building material to a
curing energy such as thermal energy (e.g., by heating the building
material) or to irradiation (e.g., UV or other photo-irradiation),
or may be activated chemically, for example, by acid or base
activation.
[0004] The chemical (e.g., polymerizable) compositions utilized in
inkjet 3D printing processes are therefore selected so as to meet
the process requirements, namely, exhibiting a suitable viscosity
during jetting (thus being non-curable under jetting conditions)
and rapid curing or solidification, typically upon exposure to a
stimulus on the receiving medium. The building materials may
include modeling materials and support materials, which form the
object and optionally the temporary support constructions
supporting the object as it is being built, respectively. The
modeling material (which may include one or more material(s)) is
deposited to produce the desired object/s and the support material
(which may include one or more material(s)) is used, with or
without modeling material elements, to provide support structures
for specific areas of the object during building and assure
adequate vertical placement of subsequent object layers, e.g., in
cases where objects include overhanging features or shapes such as
curved geometries, negative angles, voids, and so on.
[0005] Both the modeling and support materials are preferably
liquid at the working temperature at which they are dispensed, and
subsequently hardened, upon exposure to a condition that affects
curing of the materials, to form the required layer shape. After
printing completion, support structures, if present, are removed to
reveal the final shape of the fabricated 3D object.
[0006] In order to be compatible with most of the
commercially-available printing heads utilized in a 3D inkjet
printing system, the uncured building material should feature the
following characteristics: a relatively low viscosity (e.g.,
Brookfield Viscosity of up to 35 cps, preferably from 8 to 25 cps)
at the working (e.g., jetting) temperature; Surface tension of from
about 25 to about 40 Dyne/cm; and a Newtonian liquid behavior and
high reactivity to a selected curing energy, to enable immediate
solidification of the jetted layer upon exposure to a curing
energy).
[0007] The cured modeling material which forms the final object
should preferably exhibit heat deflection temperature (HDT) which
is higher than room temperature, in order to assure its usability.
In most cases, it is also desirable that the object exhibits
relatively high Izod Notched Impact (Impact resistance), e.g.,
higher than 50 or higher than 60 J/m.
[0008] Until today, most 3D inkjet methodologies have utilized
photopolymerizable materials, and photo-induced curing, typically
UV curing, thus narrowing the choice of materials and chemical
reactions that can be utilized in this technology. Exemplary
photopolymerizable building materials that are currently used in,
for example, a "PolyJet" technology (Stratasys Ltd., Israel), are
acrylic based materials.
[0009] International Patent Application Publication No. WO
2013/128452, by the present Assignee, discloses a multi-material
approach which involves separate jetting of two components of a
cationic polymerizable system and/or a radical polymerizable
system, which intermix on the printing tray, leading to a
polymerization reaction similar to pre-mixing of the two components
before jetting, while preventing their early polymerization on the
inkjet head nozzle plate.
[0010] Building materials obtained by Ring Opening Polymerization
(ROP) reactions such as anionic and cationic ring opening
polymerizations, exhibit certain valuable properties, such as
potentially high curing speed, relatively low shrinkage, high
thermal resistance, high impact resistance, and chemical and
solvent resistance. These reactions often provide thermoplastic
and/or thermosetting materials, which may find many applications
upon being engineered by inkjet 3D printing.
[0011] An exemplary material which may be suitable for providing
such building materials is caprolactam, the precursor of the
polyamide Nylon6.
[0012] Nylon6, as well as other polyamides, can be prepared by
anionic polymerization, by known casting processes such as vertical
casting, centrifugal casting or rotocasting. Some industrial
production processes of Nylon6 involve mixing two
components--molten pre-blends of caprolactam/activator and
caprolactam/catalyst, and filling a mold. The polymerization
reaction is then completed within a few minutes in the mold.
[0013] Commercially available Nylon6 is known as a thermoplastic
polymer which exhibits HDT higher than 150.degree. C., and moderate
impact resistance of about 40-60 J/m.
[0014] The moderate impact resistance of Nylon6 and other
polyamides can be improved by using impact modifiers, the most
commonly practiced being PEG/PPG-based materials. Additional
commonly practiced polyamide impact modifiers include polyols, such
as polyetheramine (polyoxyalkylene triamine), commercially
available under the trade names Jeffamine.RTM. (Huntsman),
Polyetheramin (BASF) or PC Amine.RTM. (Nitroil), Jeffamine.RTM.
T-403, Jeffamine.RTM. T-3000, Jeffamine.RTM. T-5000, Polyetheramine
T403, Polyetheramine T5000, PC Amine.RTM. TA 403, PC Amine.RTM. TA
5000.
[0015] The choice of the activator and optionally the impact
modifier may provide for a control of the mechanical properties of
the polyamide obtained by anionic ROP using currently practiced
casting processes.
[0016] NYRIM.RTM., for example, is an elastomer-modified
AP-Nylon.RTM., or PA6 block copolymer. The characteristics of this
copolymer can be selectively controlled, depending on its intended
use, by varying the elastomer content. Typically, the elastomer
component accounts for between 10% (NYRIM.RTM. 1000) and 40% by
weight (NYRIM.RTM. 4000) of the final product.
[0017] Some mechanical properties of NYRIM.RTM. compositions are
presented in Table 1 below.
TABLE-US-00001 TABLE 1 NYRIM .RTM. NYRIM .RTM. NYRIM .RTM. NYRIM
.RTM. Parameter 1000 2000 3000 4000 Modulus of 2500 1700 978 300
elasticity (tensile test) [MPa] Elongation at 40 270 350 420
fracture [%] Tensile 58 47 37 26 strength [MPa] Impact 10 30 62 No
fracture resistance (Izod) at 23.degree. C. [kJ/m.sup.2] Impact 7 9
16 No fracture resistance (Izod) at -40.degree. C. [kJ/m.sup.2]
Hardness 79 74 67 59 (Shore D)
[0018] Additional modifications of anionic polymerization of
polyamides, made in order to control the properties of the obtained
polymer have been described in the art.
[0019] U.S. Patent Application Publication No. 2013/0065466
describes anionic polymerization of polyamides in the presence of
polyethyleneimines.
[0020] U.S. Pat. No. 9,139,752 describes a process for producing
polyamides via anionic polymerization using capped (lactam-blocked)
polyisocyanate as an activator (promoter).
[0021] U.S. Patent Application Publication No. 2012/0283406
describes compositions comprising an aliphatic or alicyclic di-or
multi-isocyanate compound and a lactone, utilized in anionic
polymerization of lactam, for controlling the mechanical properties
of the obtained polyamide.
[0022] EP Patent Application No. 2801588 describes compositions
containing N-acetylcaprolactam and (optionally caprolactam-blocked)
polyisocyanate compounds based on hexamethylene diisocyanate (HDI),
usable in production of polyamide castings.
[0023] Several studies have been conducted for finding caprolactam
compositions which can be used in inkjet printing processes. In
most of these studies, two compositions, one of caprolactam and a
catalyst (typically NaH or MgBr or corresponding lactam salts) and
one of caprolactam and an activator (typically
N-acetylcaprolactam), have been used. See, for example, Khosrow
Khodabakhshi, A Doctoral Thesis. Submitted for the award of Doctor
of Philosophy of Loughborough University, 2011; Khodabakhshi et
al., Solid Freeform Fabrication Proceedings, The University of
Texas at Austin, Tex. (USA), 2009; Fathi et al., NIP25:
International Conference on Digital Printing Technologies and
Digital Fabrication, Louisville, Kentucky, September 2009, 784-787;
Fathi and Dickens, J. Manuf. Sci. Eng. 134(4), 041008 (Jul. 18,
2012).
[0024] Additional background art includes GB2382798.
SUMMARY OF THE INVENTION
[0025] The present inventors have devised and successfully
practiced a methodology for inkjet printing of objects made of
chemical compositions which form the building material (e.g., the
modeling material) upon curing, while digitally controlling the
properties of the obtained building material, at a voxel level.
This methodology is based on dual jetting of two or more different
compositions, each containing a different material or mixture of
materials, which, when contacted, undergo a chemical reaction
therebetween to form the building material. The chemical
composition of the formed building material is dictated by the
number of voxels of each composition in a voxel block. This
methodology allows a production of, for example, printed objects
which feature different chemical compositions and hence different
properties for different voxel blocks, as desired, including
properties that are changed gradually or continuously throughout
the object as desired, at the voxel block level.
[0026] In exemplary embodiments, the methodology described herein
is utilized for printing objects made of, or comprising, polyamide
forming materials (formed by anionic ROP of caprolactam), while
controlling the properties of the objects at the voxel level. The
control of these properties is made by dual jetting of one
composition that comprises, for example, caprolactam (and/or other
curable lactam) and another composition that comprises a promoter
of an anionic ring opening polymerization of the caprolactam
(referred to herein also as an activator), while controlling the
ratio of the compositions at the voxel level, and subjecting the
jetted compositions to curing conditions that effect anionic ring
opening polymerization of caprolactam. The promoter in such a
reaction forms a part of the obtained cured product and can
therefore be selected such that its type and amount at a selected
voxel block determines the properties of the cured product (e.g.,
the modeling material).
[0027] according to an aspect of some embodiments of the present
invention there is provided a method of fabricating an object, the
method comprising: receiving three-dimensional printing data
corresponding to the shape of the object; selecting a ratio between
a first composition and a second composition, wherein the first
composition comprises a first material and the second composition
comprises a second material, the first and second materials
undergoing a chemical reaction with one another so as to form a
building material when exposed to a curing energy; dispensing
droplets of the first and the second compositions in layers, on a
receiving medium, using at least two different inkjet printing
heads, according to the printing data; wherein for at least one
region of the object, the dispensing of the droplets is selected to
form voxel blocks, wherein, for each block, a ratio between a
number of voxels of the first composition in the block and a number
of voxels of the second composition in the block corresponds to the
selected ratio.
[0028] According to some of any of the embodiments of the invention
selecting the ratio is executed at least twice.
[0029] According to some of any of the embodiments of the invention
selecting the ratio is executed at least twice for at least one of
the layers.
[0030] According to some of any of the embodiments of the invention
method comprises heating at least one of the first and second
compositions prior to the dispensing.
[0031] According to some of any of the embodiments of the invention
the heating is at a temperature at which each of the first
composition and the second composition exhibits a viscosity of no
more than 25 centipoises, the temperature being lower than a
temperature at which the first material and the second material
undergo the chemical reaction.
[0032] According to some of any of the embodiments of the invention
method comprises exposing the dispensed layers to the curing
energy.
[0033] According to some of any of the embodiments of the invention
the curing energy comprises heat.
[0034] According to some of any of the embodiments of the invention
the exposing the dispensed layers to the curing energy comprises
heating the receiving medium using a resistive heater.
[0035] According to some of any of the embodiments of the invention
the exposing the dispensed layers to the curing energy comprises
irradiating the dispensed layers by heat-inducing radiation.
[0036] According to some of any of the embodiments of the invention
the dispensing is in a printing chamber and the method comprises
heating the printing chamber prior to, during or following the
dispensing.
[0037] According to some of any of the embodiments of the invention
the dispensing and/or exposing to the curing energy is effected
under a generally dry and inert environment.
[0038] According to some of any of the embodiments of the invention
at least one of the first and second compositions comprises an
additional material for inducing a chemical reaction between the
first and second materials.
[0039] According to some of any of the embodiments of the invention
the first material is a first curable material.
[0040] According to some of any of the embodiments of the invention
the second material is selected capable of modifying a chemical,
physical and/or mechanical property of a modeling material formed
of the first curable material, upon chemically reacting with the
first curable material and exposure to the curing energy, and
wherein a degree of the modifying is determined by selecting the
ratio.
[0041] According to some of any of the embodiments of the invention
the second material is a second curable material.
[0042] According to some of any of the embodiments of the invention
the first material comprises a first plurality of monomers and the
second material comprises a second plurality of monomers being
chemically different from the first plurality of monomers, wherein
the first and second pluralities of monomers chemically react with
one another upon exposure to the curing energy.
[0043] According to some of any of the embodiments of the invention
the second material affects cross-linking of a polymeric material
formed of the first curable material.
[0044] According to some of any of the embodiments of the invention
the second material promotes a polymerization of the first curable
material upon exposure to the curing energy, while forming a part
of a modeling material formed by curing the first curable
material.
[0045] According to some of any of the embodiments of the invention
the first curable material is a monomer that is polymerizable by a
ring opening polymerization.
[0046] According to some of any of the embodiments of the invention
the ring opening polymerization is an anionic ring opening
polymerization.
[0047] According to some of any of the embodiments of the invention
the first curable material is a lactam.
[0048] According to some of any of the embodiments of the invention
the first curable material is a caprolactam.
[0049] According to some of any of the embodiments of the invention
the second material comprises at least one material that promotes
the anionic ring opening polymerization while forming a part of the
modeling material formed by curing the caprolactam.
[0050] According to some of any of the embodiments of the invention
the second material comprises a moiety that chemically interacts
with the caprolactam during the polymerization.
[0051] According to some of any of the embodiments of the invention
the second material further comprises an additional moiety which is
such that when forming a part of a modeling material formed of the
caprolactam, a chemical, physical and/or mechanical property of the
modeling material is modified.
[0052] According to some of any of the embodiments of the invention
the additional moiety comprises an elastomeric moiety, and
optically-active moiety, a light-absorbing moiety, a hydrophobic
moiety, a hydrophilic moiety and/or a chemically-reactive
moiety.
[0053] According to some of any of the embodiments of the invention
the second material is represented by the general Formula I:
##STR00001##
[0054] wherein: A is the additional moiety; R is N-acyl lactam; and
n is a positive integer.
[0055] According to some of any of the embodiments of the invention
the second material comprises at least two N-acyl lactam
groups.
[0056] According to some of any of the embodiments of the invention
the first composition further comprises a catalyst for inducing
polymerization of the caprolactam.
[0057] According to some of any of the embodiments of the invention
the second composition is devoid of the first curable material.
[0058] According to an aspect of some embodiments of the present
invention there is provided a method of fabricating an object. The
method comprises: receiving three-dimensional printing data
corresponding to the shape of the object; selecting a ratio between
a first composition and a second composition, wherein the first
composition comprises a lactam and the second composition comprises
a second material which promotes an anionic ring opening
polymerization of the lactam upon exposure to heat to thereby form
a polyamide building material; dispensing droplets of the first and
the second compositions in layers, on a receiving medium, using at
least two different inkjet printing heads, according to the
printing data; wherein for at least one region of the object, the
dispensing of the droplets is selected to form voxel blocks,
wherein, for each block, a ratio between a number of voxels of the
first composition in the block and a number of voxels of the second
composition in the block corresponds to the selected ratio.
[0059] According to some of any of the embodiments of the invention
each of the voxel blocks comprises from 2 to 20 voxels.
[0060] According to some of any of the embodiments of the invention
selecting the ratio is performed for at least two different
layers.
[0061] According to some of any of the embodiments of the invention
selecting the ratio is executed at least twice.
[0062] According to some of any of the embodiments of the invention
method comprises heating at least one of the first and second
compositions prior to the dispensing.
[0063] According to some of any of the embodiments of the invention
the heating is at a temperature at which each of the first
composition and the second composition exhibits a viscosity of no
more than 25 centipoises, the temperature being lower than a
temperature at which the caprolactam is polymerizable.
[0064] According to some of any of the embodiments of the invention
method comprises, subsequent to the dispensing, exposing the
dispensed layers to the heat.
[0065] According to some of any of the embodiments of the invention
the exposing the dispensed layers to the heat comprises heating the
receiving medium using a resistive heater.
[0066] According to some of any of the embodiments of the invention
the exposing the dispensed layers to the heat comprises irradiating
the dispensed layers by heat-inducing radiation.
[0067] According to some of any of the embodiments of the invention
the dispensing is effected under a generally dry and inert
environment.
[0068] According to some of any of the embodiments of the invention
a property of the modeling material is determined by selecting the
ratio.
[0069] According to some of any of the embodiments of the invention
the lactam comprises a caprolactam.
[0070] According to some of any of the embodiments of the invention
the second material comprises at least one material that promotes
the anionic ring opening polymerization while forming a part of the
modeling material formed by curing the lactam.
[0071] According to some of any of the embodiments of the invention
the second material comprises a moiety that chemically interacts
with the lactam during the polymerization.
[0072] According to some of any of the embodiments of the invention
the second material comprises at least one moiety which is such
that when forming a part of a modeling material formed of the
lactam, a chemical, physical and/or mechanical property of the
modeling material is modified.
[0073] According to some of any of the embodiments of the invention
the at least one moiety comprises an elastomeric moiety, and
optically-active moiety, a light-absorbing moiety, a conductance
modifying moiety, a metal chelating moiety, a hydrophobic moiety, a
hydrophilic moiety and/or a chemically-reactive moiety.
[0074] According to some of any of the embodiments of the invention
the second material is represented by the general Formula I:
##STR00002##
[0075] wherein: A is the additional moiety; R is N-acyl lactam; and
n is a positive integer.
[0076] According to some embodiments of the invention the method
wherein the second material comprises at least two N-acyl lactam
groups.
[0077] According to some of any of the embodiments of the invention
the second material is represented by Formula II:
##STR00003##
[0078] wherein: A is the additional moiety; L is absent or is a
linking moiety; and A' is absent or is another additional moiety,
being the same or different from the A.
[0079] According to some embodiments of the invention the method
wherein A' comprises at least one N-acyl lactam moiety.
[0080] According to some of any of the embodiments of the invention
the first composition further comprises a catalyst for inducing the
ring opening polymerization.
[0081] According to some of any of the embodiments of the invention
the catalyst is selected from the group consisting of sodium
caprolactam and magnesium bromide caprolactam.
[0082] According to some of any of the embodiments of the invention
the second composition is devoid of caprolactam.
[0083] According to an aspect of some embodiments of the present
invention there is provided a system for three-dimensional
printing. The system comprises: a plurality of inkjet printing
heads, each having a plurality of separated nozzles; a user
interface for receiving a selected ratio between a first
composition and a second composition, wherein the first composition
comprises a first material and the second composition comprises a
second material, the first and second materials undergoing a
chemical reaction with one another so as to form a modeling
material when contacted and exposed to a curing energy; and a
controller configured for controlling two of the inkjet printing
heads to respectively dispense droplets of the first and second
compositions in layers, such as to print a three-dimensional
object, wherein the controller is configured to form voxel blocks,
wherein, for each block, a ratio between a number of voxels of the
first composition in the block and a number of voxels of the second
composition in the block corresponds to the selected ratio.
[0084] According to some of any of the embodiments of the invention
the system comprises a waste collection device receiving excessive
amounts of the compositions, the waste collection device being
constructed for at least one of (i) mechanically breaking reaction
product of the compositions formed in the waste collection device,
and (ii) maintaining a reduced temperature of the compositions, the
reduce temperature being lower than a temperature at which the
composition react with each other to form the modeling
material.
[0085] Unless otherwise defined, all technical and/or scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which the invention pertains.
Although methods and materials similar or equivalent to those
described herein can be used in the practice or testing of
embodiments of the invention, exemplary methods and/or materials
are described below. In case of conflict, the patent specification,
including definitions, will control. In addition, the materials,
methods, and examples are illustrative only and are not intended to
be necessarily limiting.
[0086] Implementation of the method and/or system of embodiments of
the invention can involve performing or completing selected tasks
manually, automatically, or a combination thereof. Moreover,
according to actual instrumentation and equipment of embodiments of
the method and/or system of the invention, several selected tasks
could be implemented by hardware, by software or by firmware or by
a combination thereof using an operating system.
[0087] For example, hardware for performing selected tasks
according to embodiments of the invention could be implemented as a
chip or a circuit. As software, selected tasks according to
embodiments of the invention could be implemented as a plurality of
software instructions being executed by a computer using any
suitable operating system. In an exemplary embodiment of the
invention, one or more tasks according to exemplary embodiments of
method and/or system as described herein are performed by a data
processor, such as a computing platform for executing a plurality
of instructions. Optionally, the data processor includes a volatile
memory for storing instructions and/or data and/or a non-volatile
storage, for example, a magnetic hard-disk and/or removable media,
for storing instructions and/or data. Optionally, a network
connection is provided as well. A display and/or a user input
device such as a keyboard or mouse are optionally provided as
well.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0088] Some embodiments of the invention are herein described, by
way of example only, with reference to the accompanying drawings.
With specific reference now to the drawings in detail, it is
stressed that the particulars shown are by way of example and for
purposes of illustrative discussion of embodiments of the
invention. In this regard, the description taken with the drawings
makes apparent to those skilled in the art how embodiments of the
invention may be practiced.
[0089] In the drawings:
[0090] FIG. 1 is a flowchart diagram of a method suitable for
fabricating an object by three-dimensional (3D) inkjet printing
according to aspects of some embodiments of the present
invention.
[0091] FIG. 2 is a schematic illustration of a layer having a
plurality of voxels arranged in blocks, according to some
embodiments of the present invention.
[0092] FIG. 3A is a schematic illustration of two layers, each
having a plurality of voxels arranged in blocks, according to some
embodiments of the present invention.
[0093] FIG. 3B is a schematic illustration of a layer having two
regions, according to some embodiments of the present
invention.
[0094] FIG. 4 is a schematic illustration of a three-dimensional
printing system, according to some embodiments of the present
invention.
[0095] FIGS. 5A and 5B present schematic illustrations of bitmaps
in embodiments of the invention in which a "Drop on Drop" printing
protocol is employed. A bitmap suitable for the deposition of the
first composition is illustrated in FIG. 5A and a bitmap suitable
for the deposition of the second composition is illustrated in FIG.
5B. When the droplets of both compositions have the same or
approximately the same weight, the bitmaps are useful for a 50:50
(or 1:1) w/w ratio. White boxes represent vacant locations, dotted
boxes represent droplets of the first composition and wavy boxes
represent droplets of the second composition. Each patterned
(wavy/dotted) box represents a pixel (e.g., one composition
droplet) in a layer. Both compositions can be deposited at the same
location, but different times, during movement of the printing
head.
[0096] FIGS. 6A and 6B present schematic illustrations of bitmaps
in embodiments of the invention in which a "side-by-side" printing
protocol is employed. A bitmap suitable for the deposition of the
first composition is illustrated in FIG. 6A and a bitmap suitable
for the deposition of the second composition is illustrated in FIG.
6B. When the droplets of both compositions have the same or
approximately the same weight, the bitmaps are useful for a 50:50
(or 1:1) w/w ratio. White boxes represent vacant locations, dotted
boxes represent droplets of the first composition and wavy boxes
represent droplets of the second composition. Each patterned
(wavy/dotted box represents a pixel (e.g., one formulation
droplet). A drop of the first composition (dotted boxes) is
deposited adjacent to a drop of the second composition.
DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION
[0097] The present invention, in some embodiments thereof, relates
to three-dimensional printing and, more particularly, but not
exclusively, to methods of performing three-dimensional inkjet
printing, to compositions utilized in these methods and to objects
obtained by these methods.
[0098] Before explaining at least one embodiment of the invention
in detail, it is to be understood that the invention is not
necessarily limited in its application to the details of
construction and the arrangement of the components and/or methods
set forth in the following description and/or illustrated in the
drawings and/or the Examples. The invention is capable of other
embodiments or of being practiced or carried out in various
ways.
[0099] A major advantage of 3D printing by ink jet technology comes
from the ability to control every voxel in the printed layer so
that a multi-material object may be produced, in which there is a
predetermined distribution of materials over the voxels.
[0100] Herein throughout, the phrase "building material" describes
two major categories of material: `modeling material`, i.e., the
hardened (cured) material that forms the final product (e.g.,
object) of the 3D printing process, and `support material`.
[0101] The phrases "hardened building material", "cured building
material" and simply "building material" as used herein refer to
the material obtained after dispensing droplets of uncured
formulations, and after a chemical reaction occurred between the
first and second compositions, preferably, after curing energy is
applied, unless otherwise stated. Whenever reference is made to
building material formulations used before dispensing the droplets
and before curing energy is applied, it is referred to herein as
"uncured building material" or "uncured building material
formulation" or simply as "building material formulation".
[0102] The terms "composition" and "formulation" are used herein
throughout interchangeably.
[0103] The support material serves as a supporting matrix for
supporting the object or object parts during the fabrication
process and/or other purposes, e.g., for hollow or porous objects,
or to support overhangs. The support material, when cured, is
preferably water dispersible to facilitate its removal once the
buildup of object is completed. The formulation (composition) used
to form the cured support material is preferably dispensed in
liquid form and is typically curable by radiation, such as, but not
limited to, electromagnetic radiation (e.g., ultraviolet radiation,
visible light radiation, infrared radiation), and electron beam
radiation, so as to form the support material. Also contemplated
are support materials which comprise a wax component, and,
optionally, also a viscosity modifying component. These types of
support materials are in liquid form at the inkjet printing
temperatures, solidify once cooled after being dispensed, and do
not require curing by radiation.
[0104] The modeling material is generally made of a formulation
(composition) which is formulated for use in inkjet technology and
which forms the three-dimensional object, typically upon curing.
The modeling material is generally made of a curable (base)
material composition, formulated for use in inkjet technology, and
which is able to form the three-dimensional object on its own,
i.e., without having to be mixed or combined with any other
substance. The base material is preferably dispensed in liquid form
and is curable by radiation, such as, but not limited to,
electromagnetic radiation (e.g., ultraviolet radiation, visible
light radiation, infrared radiation), and electron beam radiation,
or by heat delivered convectively or conductively, as to form the
(cured) modeling material.
[0105] The phrase "modeling material" is also referred to herein
and in the art as "model material" and refers to the modeling
material obtained after dispensing droplets of uncured modeling
material formulations (e.g., the first and second compositions as
described herein), and after a chemical reaction occurred between
the first and second compositions, preferably, after curing energy
is applied, unless otherwise stated. This phrase is also referred
to herein as cured modeling material or hardened modeling material.
Whenever reference is made to modeling material formulations used
before dispensing the droplets and before curing energy is applied,
it is referred to herein as "uncured modeling material", "uncured
model material" or "uncured modeling material formulation" or
simply as "modeling material formulation".
[0106] In some embodiments of the invention both the support and
the modeling materials are obtained using the same type of
curing.
[0107] The final three-dimensional object that is fabricated is
typically made of only the cured modeling material or materials. In
some embodiments of the present invention the three-dimensional
object or parts of the object may be made of a combination of cured
modeling and support materials.
[0108] Herein throughout, the phrase "base material" describes the
material that is jetted during the inkjet printing, which cures
(e.g., polymerizes) to form the cured modeling material. The phrase
"base material" describes an uncured formulation (composition), or
a mixture of uncured formulations (compositions) that upon curing
forms a cured modeling material as described herein.
[0109] The phrase "multi-material model", as used herein and in the
art, describes a printed object (model) featuring macroscopic
domains of different modeling materials in at least a portion
thereof, for example, a printed object that is comprised of
portions having different properties, e.g. mechanical properties,
such as flexibility, rigidity, elasticity and so on, such that, for
example, a printed object may comprise a combination of a flexible
portion and a rigid portion. This phrase encompasses an object
featuring domains of different modeling materials, wherein the
modeling materials differ from one another by the ratio of the
compositions (formulations) that are used to form the modeling
material.
[0110] The phrase "digital materials", as used herein and in the
art, describes a combination of two or more materials on a
microscopic scale or voxel level such that the printed zones of a
specific material are at the level of few voxels, or at a level of
a voxel block. Such digital materials may exhibit new properties
that are affected by the selection of types of materials and/or the
ratio and relative spatial distribution of two or more
materials.
[0111] In exemplary digital materials, the modeling material of
each voxel or voxel block, obtained upon curing, is independent of
the modeling material of a neighboring voxel or voxel block,
obtained upon curing, such that each voxel or voxel block may
result in a different model material and the new properties of the
whole part are a result of a spatial combination, on the voxel
level, of several different model materials.
[0112] Herein throughout, whenever the expression "at the voxel
level" is used in the context of a different material and/or
properties, it is meant to include differences between voxel
blocks, as well as differences between voxels or groups of few
voxels. In preferred embodiments, the properties of the whole part
are a result of a spatial combination, on the voxel block level, of
several different model materials.
[0113] The present inventors have now designed a methodology for
inkjet printing, via separate printing heads, two or more
compositions, which form, upon chemically reacting with one
another, a hardened (cured) building material. The present
inventors have shown that the chemical composition of the hardened
building material can be digitally controlled, by controlling the
ratio of the jetted compositions at a voxel level. As demonstrated
in the Examples section that follows, the present inventors have
demonstrated that practicing this methodology by dual jetting of a
caprolactam composition containing a catalyst, and another
composition containing a material that participates in the
polymerization of caprolactam (e.g., a promoter), while controlling
the number of voxels of each composition and particularly the ratio
between these numbers of voxels, results in tailor-made, multiple
cured building (e.g., modeling) materials which may be designed to
exhibit a plethora of mechanical and chemical properties, at the
voxel level.
[0114] The present inventors have shown that changing the ratio of
voxels of each composition which are adjacent to one another,
results in cured polymers which exhibit different chemical
compositions and different chemical, physical and/or mechanical
properties, whereby these structures and properties are
controllable at a level of few voxels (e.g., from 2 to 100 voxels
or from 2 to 80 voxels or from 2 to 60 voxels or from 2 to 40
voxels or from 2 to 30 voxels or from 2 to 20 voxels or from 2 to
10 voxels or from 2 to 8 voxels or from 2 to 6 voxels or from 2 to
4 voxels or from 10 to 80 voxels or from 10 to 60 voxels or from 10
to 40 voxels).
[0115] Such a methodology results in printed objects in which the
properties of portions of these objects are controlled at a
resolution of a few voxels.
[0116] The method:
[0117] FIG. 1 is a flowchart diagram of a method suitable for
fabricating an object by three-dimensional (3D) inkjet printing
according to aspects of some embodiments of the present invention.
It is to be understood that, unless otherwise defined, the
operations described hereinbelow can be executed either
contemporaneously or sequentially in many combinations or orders of
execution. Specifically, the ordering of the flowchart diagrams is
not to be considered as limiting. For example, two or more
operations, appearing in the following description or in the
flowchart diagrams in a particular order, can be executed in a
different order (e.g., a reverse order) or substantially
contemporaneously. Additionally, several operations described below
are optional and may not be executed.
[0118] The method begins at 10 and optionally and preferably
continues to 11 at which 3D printing data corresponding to the
shape of the object is received. The data can be received, for
example, from a host computer which transmits digital data
pertaining to fabrication instructions based on computer object
data, e.g., in a form of a Standard Tessellation Language (STL) or
a StereoLithography Contour (SLC) format, Virtual Reality Modeling
Language (VRML), Additive Manufacturing File (AMF) format, Drawing
Exchange Format (DXF), Polygon File Format (PLY) or any other
format suitable for Computer-Aided Design (CAD).
[0119] At 12 a ratio between a first composition and a second
composition is received. While the embodiments below are described
with a particular emphasis on a ratio between two compositions, it
is to be understood that more detailed reference to a ratio between
two compositions is not to be interpreted as indicating that
embodiments in which a ratio between more than two compositions are
not contemplated. Thus, embodiments of the present invention
contemplate receiving a ratio between N compositions, where N is at
least 2, and can be 2, 3, 4, or more. The ratio is typically
expressed in terms of the volumes of the respective compositions,
but may also be expressed in terms of other extensive physical
properties, such as the weights of the respective compositions. A
representative example of a received ratio for two compositions is
X1:X2, where X1 and X2 are the extensive physical properties (e.g.,
weight, volume) of the first and second compositions. A
representative example of a received ratio for three or more
compositions is X1:X2: . . . :XN, where N is the number of the
compositions (N>2, in the present example) and X1, X2, . . . ,
XN are the extensive physical properties (e.g., weight, volume) of
the respective compositions.
[0120] The ratio can be received as a user input or can be obtained
from an external source, such as, but not limited to, a computer
that calculates the ratio and transmits it to the method. At least
two of the compositions comprise substances (materials) that react
chemically with one another to form a building (e.g., modeling)
material. The properties of the building (e.g., modeling) material
that is formed by the chemical reaction typically depend on the
selected ratio. The computer can thus calculate the ratio based on
the desired properties of the building (e.g., modeling) material.
Also contemplated are embodiments in which instead of receiving the
ratio the method receives building (e.g., modeling) material
properties and calculates the ratio based on the received
properties.
[0121] Optionally, the method continues to 13 at which the first
and/or second compositions are heated. These embodiments are
particularly for compositions that are either solid or are liquid
yet have relatively high viscosity at the operation temperature of
the working chamber of the 3D printing system. The heating of the
composition(s) is preferably to a temperature that allows jetting
the respective composition through a nozzle of a printing head of a
3D printing system. In some embodiments, the heating of the
composition is to a minimal temperature at which the respective
composition is in a liquid form, e.g., above the highest melting
point of a material in the composition. In some embodiments of the
present invention, the heating is to a temperature at which the
respective composition exhibits a viscosity in a range of from
about 8 centipoises and up to no more than X centipoises, where X
is about 35 centipoises, or about 30 centipoises, preferably about
25 centipoises and more preferably about 20 centipoises, or 18
centipoises, or 16 centipoises, or 14 centipoises, or 12
centipoises, or 10 centipoises, and at which the composition cannot
undergo thermal curing (e.g., below a temperature at which curing,
as defined herein, can be effected). Thus, denoting the temperature
at which the viscosity of the respective composition is X
centipoises by T.sub.1 and the temperature at which thermal curing
is effected for that composition by T.sub.2, the heating at 13 is
preferably to a temperature T satisfying
T.sub.1<T<T.sub.2.
[0122] The heating 13 can be executed before loading the respective
composition into the printing head of the 3D printing system, or
while the composition is in the printing head or while the
composition passes through the nozzle of the printing head.
[0123] In some embodiments, heating 13 is executed before loading
of the respective composition into the printing head, so as to
avoid clogging of the printing head by the composition in case its
viscosity is too high.
[0124] In some embodiments, heating 13 is executed by heating the
printing heads, at least while passing the first and/or second
composition(s) through the nozzle of the printing head.
[0125] In some embodiments, both the first and second (or all
other) compositions are heated, and in some embodiments, only one
(or more) of the compositions is heated, while the other
composition(s) exhibit a desired viscosity of less than 25
centipoises at ambient temperature.
[0126] The method continues to 14 at which droplets of the
compositions are dispensed in layers, on a receiving medium, using
at least two different multi-nozzle inkjet printing heads,
according to the printing data. The receiving medium can be a tray
of a three-dimensional inkjet system or a previously deposited
layer.
[0127] In some embodiments of the present invention, the dispensing
14 is effected under a generally dry and inert environment.
[0128] As used herein "generally dry environment" means an
environment having a relative humidity of less than 50% or less
than 40% or less than 30% or less than 20% or less than 10%,
preferably less than 5%, or less than 2% or less than 1% or
less.
[0129] As used herein "inert environment" means an environment that
is substantially free of oxygen, carbon dioxide, water and/or any
other substances that may chemically react with the first and
second compositions or otherwise interfere in the chemical reaction
between substances in the first and second compositions.
[0130] As used herein, "substantially free" means less than 1% or
less than 0.5%, or less than 0.1%, or less than 0.05%, or less than
0.01% of a substance that may interfere in the chemical
reaction.
[0131] An inert environment can be established by supplying an
inert gas or an inert gas mixture into the working chamber of the
3D printing system. Representative examples of an inert gas
include, but are not limited to, nitrogen and/or argon.
[0132] In some embodiments, the inert environment is a dry inert
environment, such as dry nitrogen and/or argon.
[0133] Accordingly, as used herein, "inert" environment or "inert"
atmosphere is not limited to an environment consisting of inert
gases, but can mean either an inert gas, a mixture of inert gases,
or a vacuum.
[0134] The method optionally and preferably continues to 15 at
which curing energy is applied to the deposited layers. Preferably,
the curing is applied to each individual layer following the
deposition of the layer and prior to the deposition of the previous
layer.
[0135] In some embodiments, the applied curing energy in 15 is
thermal energy.
[0136] Applying thermal energy can be effected, for example, by
heating a receiving medium onto which the layers are dispensed. In
some embodiments, the heating is effected using a resistive
heater.
[0137] In some embodiments, the heating is effected by irradiating
the dispensed layers by heat-inducing radiation. Such irradiation
can be effected, for example, by means of an IR lamp or Xenon lamp,
operated to emit radiation onto the deposited layer.
[0138] Alternatively, or in addition, the applied curing energy is
electromagnetic irradiation, as described herein.
[0139] In some embodiments, two or different curing energies are
applied. In some of these embodiments, curing energy of a first
type is applied and then curing energy of a second type is applied.
For example, the first curing energy can be in the form of UV
radiation and the second curing energy can be in the form of
thermal energy delivered by convection, conduction and/or
radiation.
[0140] In some embodiments, applying a curing energy is effected
under a generally dry and inert environment, as described
herein.
[0141] The method ends at 16.
[0142] In some embodiments, the method is effected such that for at
least one region of the object, the dispensing of the droplets is
selected to form voxel blocks, wherein, for each block, a ratio
between a number of voxels of the first composition in the block
and a number of voxels of the second composition in the block
corresponds to the selected ratio between the at least first and
second compositions.
[0143] These embodiments are illustrated in FIG. 2 which shows a
layer 20 having a plurality of voxels 22 arranged in blocks 24.
[0144] Herein throughout, the term "voxel" describes a volume
element deposited by a single nozzle of a three-dimensional
printing system.
[0145] Herein throughout, the term "voxel block" describes a group
of voxels wherein each voxel in the group is adjacent to at least
one other voxel in the group.
[0146] Voxels occupied with the first composition are shown in FIG.
2 as white and voxels occupied with the second composition are
marked in FIG. 2 with hatching. In the representative example of
FIG. 2, which is not intended to be limiting, each block includes 9
voxels, wherein the ratio between a number of voxels of the first
composition and a number of voxels of the second composition in the
block is 8:1.
[0147] In various exemplary embodiments of the invention the ratio
8:1 corresponds to the ratio received or calculated at 12. For
example, when the same amount (e.g., weight, volume) of composition
is deposited onto each voxel, the ratio between the number of
voxels can be the same as the ratio received or calculated at 12.
When the amount of composition in a voxel occupied with the first
composition is not the same as the amount of composition in a voxel
occupied with the second composition, the ratio between the numbers
of voxels is obtained by correcting the ratio received or
calculated at 12 using the amounts in the respective voxels. In
other words, the ratio between the numbers of voxels in a block is
selected such that the ratio between the amounts of compositions
deposited within the block approximately equals the ratio received
or calculated at 12. As a representative example, consider a
process in which the method receives a ratio X1:X2=4:1, and in
which the amount of the first composition per voxel is 2 times the
amount of the second composition per voxel. In this case, a ratio
of 8:1 between the number of voxels corresponds to a ratio of 4:1
between the amounts since 8/2=4/1. The correction of the ratio the
ratio received or calculated at 12 using the amounts in the
respective voxels, can be done by a controller that is integrated
in the three-dimensional printing system (e.g., controller 52, see
FIG. 4 described below), or, alternatively by a data processor or a
computer that is external to the three-dimensional printing system
(e.g., computer 54, see FIG. 4 described below).
[0148] In some embodiments, a ratio is selected between a first
composition and a second composition.
[0149] In some embodiments, a ratio is selected between three or
more compositions, that is a first composition, a second
composition, a third composition, and optionally a fourth
composition, a fifth composition and so on.
[0150] For simplicity, the following description relates to
embodiments where a first and a second composition are used.
However, it is to be noted that embodiments in which more than two
compositions are utilized are also contemplated, as stated
hereinabove.
[0151] In some embodiments, each voxel block as defined herein
comprises from 2 to 100 voxels or from 2 to 80 voxels or from 2 to
60 voxels or from 2 to 40 voxels or from 2 to 30 voxels or from 2
to 20 voxels or from 2 to 10 voxels or from 2 to 8 voxels or from 2
to 6 voxels or from 2 to 4 voxels or from 10 to 80 voxels or from
10 to 60 voxels or from 10 to 40 voxels.
[0152] In some preferred embodiments of the invention each droplet
occupies a single voxel upon deposition of the droplet. Thereafter,
and before curing, the droplet may spread to one or more adjacent
voxels.
[0153] It is appreciated that more than one ratio between the
compositions can be received or calculated. When more than one
ratio between the compositions is employed, different ratios can
correspond to different layers or different regions in the same
layer. These embodiments are illustrated in FIGS. 3A and 3B.
[0154] FIG. 3A illustrates two layers 20a and 20b, each having a
plurality of voxels 22 arranged in blocks 24. In layer 20a each
block includes 3 voxels of the first composition and 1 voxel of the
second composition, and in layer 20b each block includes 8 voxel of
the first composition and 1 voxel of the second composition. Since
different ratios between the compositions correspond to different
properties of the building (e.g., modeling) material formed by the
reaction of the compositions with each other, the different ratios
in layers 20a and 20b can be selected to ensure that the properties
of the building (e.g., modeling) materials formed in each layer are
also different.
[0155] FIG. 3B illustrates a layer 20 having two regions designated
26 and 28. In the representative example of FIG. 3B, which is not
intended to be limiting, each block in region 26 includes 9 voxels,
and each block in region 28 includes 12 voxels. Region 26 includes
blocks of voxels wherein the ratio between a number of voxels of
the first composition and a number of voxels of the second
composition in each block is 8:1; and region 28 includes blocks of
voxels wherein the ratio between a number of voxels of the first
composition and a number of voxels of the second composition in
each block is 12:2.
[0156] Since different ratios between the compositions correspond
to different properties of the building (e.g., modeling) material
formed by the reaction of the substances in the compositions with
each other, the different ratios in regions 26 and 28 can be
selected to ensure that the properties of the building (e.g.,
modeling) materials formed in each region of the same layer are
also different.
[0157] In any of the above embodiments, the first and second
compositions begin to mix within each block 24 following their
deposition on the receiving medium, typically upon being exposed to
curing energy. The mixing and/or curing results in a building
(e.g., modeling) material which is optionally and preferably
chemically different to any of the first and second compositions
and which occupies most or all the voxels in the respective block
24. Preferably, the distribution of the building (e.g., modeling)
material, once formed, is generally uniform over the entire block
24.
[0158] As used herein "generally uniform distribution" means a
deviation from uniformity of less than 30% or 20% or less than 10%
or less than 5%.
[0159] The distribution of the building (e.g., modeling) material
can be measured with respect to any extensive property, including,
without limitation, weight and volume.
[0160] In some embodiments, all the voxels in at least one voxel
block participate in a reaction between the first and second
compositions, such that the cured building material that results
from the reaction, following the exposure to the curing energy, is
substantially homogenous.
[0161] As used herein, "substantially homogenous" means that the
building material in a voxel block vary in weight percent of its
ingredients by less than 10% or less than 8% or less than 6% or
less than 4% or less than 2% or less than 1% or less than 0.5% or
less than 0.25%.
[0162] To ensure reaction between the first and second
compositions, the deposition of the compositions can be performed
in more than one way.
[0163] In some embodiments of the present invention a "Drop on
Drop" printing protocol is employed. These embodiments are
schematically illustrated in FIGS. 5A and 5B. A bitmap suitable for
the deposition of the first composition is illustrated in FIG. 5A
and a bitmap suitable for the deposition of the second composition
is illustrated in FIG. 5B. White boxes represent vacant locations,
dotted boxes represent droplets of the first composition and wavy
boxes represent droplets of the second composition. The printing
data in these embodiments are such that for each layer, both
compositions are deposited at the same location, but different
times, during movement of the printing head. For example, each
droplet of a first composition can be jetted on top of a droplet of
a second composition, or vice versa. Preferably, but not
necessarily, the two formulation parts are jetted in drops at the
same weight and/or rate. These embodiments are particularly useful
when the desired weight ratio is 1:1. For other desired weight
ratios, the two formulation parts are preferably jetted in drops of
different weights, wherein the ratio of the weights corresponds to
the desired ratio.
[0164] A representative example for a resolution suitable for the
present embodiments is 1200 dpi in the X direction and 300 dpi in
the Y direction. The drop on drop printing protocol allows the two
types of drops to combine and mix before the crystallization of
deposited material.
[0165] In some embodiments of the present invention a "side by
side" printing protocol is employed. These embodiments are
schematically illustrated in FIGS. 6A and 6B. A bitmap suitable for
the deposition of the first composition is illustrated in FIG. 6A
and a bitmap suitable for the deposition of the second composition
is illustrated in FIG. 6B. The white, dotted and wavy boxes
represent vacant locations, droplets of the first composition and
droplets of the second composition, respectively. The printing data
in these embodiments is such that for each layer, each drop of a
first composition is jetted adjacent to a drop of a second
composition, or vice versa. Due to drop spreading, the adjacent
drops tend to partially overlap. As a result, the two drops diffuse
toward each other, mix and react after deposition.
[0166] In the schematic illustrations shown in FIGS. 5A-6B,
chessboard bitmaps are illustrated, but this need not necessarily
be the case, since, for some applications, other bitmap patterns
can be employed.
[0167] In some of any of the embodiments described herein, the
building material further comprises a support material.
[0168] In some of any of the embodiments described herein,
dispensing a building material formulation (uncured building
material) further comprises dispensing support material
formulation(s) which form the support material upon application of
curing energy.
[0169] Dispensing the support material formulation, in some
embodiments, is effected by inkjet printing head(s) other than the
inkjet printing heads used for dispensing the first and second (and
other) compositions forming the modeling material.
[0170] In some embodiments, exposing the building material to
curing energy includes applying a curing energy that affects curing
of a support material formulation, to thereby obtain a cured
support material.
[0171] In some of any of the embodiments described herein, once a
building material is cured, the method further comprises removing
the cured support material. Any of the methods usable for removing
a support material can be used, depending on the materials forming
the modeling material and the support material. Such methods
include, for example, mechanical removal of the cured support
material and/or chemical removal of the cured support material by
contacting the cured support material with a solution in which it
is dissolvable (e.g., an alkaline aqueous solution).
[0172] As used herein, the term "curing" describes a process in
which a composition is hardened. This term encompasses
polymerization of monomer(s) and/or oligomer(s) and/or
cross-linking of polymeric chains (either of a polymer present
before curing or of a polymeric material formed in a polymerization
of the monomers or oligomers). The product of a curing reaction is
therefore typically a polymeric material and in some cases a
cross-linked polymeric material. This term, as used herein,
encompasses also partial curing, for example, curing of at least
20% or at least 30% or at least 40% or at least 50% or at least 60%
or at least 70% of the formulation, as well as 100% of the
formulation.
[0173] A "curing energy" typically includes application of
radiation or application of heat, as described herein.
[0174] A curable material or system that undergoes curing upon
exposure to electromagnetic radiation is referred to herein
interchangeably as "photopolymerizable" or "photoactivatable" or
"photocurable".
[0175] When the curing energy comprises heat, the curing is also
referred to herein and in the art as "thermal curing" and comprises
application of thermal energy. Applying thermal energy can be
effected, for example, by heating a receiving medium onto which the
layers are dispensed or a chamber hosting the receiving medium, as
described herein. In some embodiments, the heating is effected
using a resistive heater.
[0176] In some embodiments, the heating is effected by irradiating
the dispensed layers by heat-inducing radiation. Such irradiation
can be effected, for example, by means of an IR lamp or Xenon lamp,
operated to emit radiation onto the deposited layer.
[0177] In some embodiments, heating is effected by infrared
radiation applied by a ceramic lamp, for example, a ceramic lamp
that produces infrared radiation of from about 3 .mu.m to about 4
.mu.m, e.g., about 3.5 .mu.m.
[0178] In some of any of the embodiments described herein, the
method further comprises exposing the cured modeling material,
either before or after removal of a support material formulation,
if such has been included in the building material, to a
post-treatment condition. The post-treatment condition is typically
aimed at further hardening the cured modeling material. In some
embodiments, the post-treatment hardens a partially-cured material
to thereby obtain a completely cured material.
[0179] In some embodiments, the post-treatment is effected by
exposure to heat or radiation, as described in any of the
respective embodiments herein. In some embodiments, when the
condition is heat, the post-treatment can be effected for a time
period that ranges from a few minutes (e.g., 10 minutes) to a few
hours (e.g., 1-24 hours).
[0180] The Compositions:
[0181] In some of any of the embodiments described herein, the
first and second compositions chemically react with one another to
form the building (e.g., modeling) material.
[0182] By "chemically reacting" and any grammatical diversion
thereof, it is meant that two or more substances (materials) in the
compositions undergo a chemical reaction that leads to a bond
formation. The bond can be an ionic bond, a hydrogen bond, or a
covalent bond, and is preferably a covalent bond.
[0183] In some of any of the embodiments described herein, the
chemical reaction occurs once the first and second compositions are
being contacted with one another.
[0184] By "being contacted" it is meant that the first and second
compositions are in a proximity that enables a chemical reaction
between two or more substances in the compositions to occur. An
exemplary suitable proximity, in the context of the present
embodiments, is, for example, of adjacent voxels within a layer of
dispensed drops, and/or of drops deposited one onto (on top of) the
other within the same voxel of a layer.
[0185] For example, by forming one or more voxels of the first
composition and one or more adjacent voxels of the second
composition, the first and second chemical compositions are
contacted and a chemical reaction occurs.
[0186] In some of any of the embodiments described herein, the
chemical reaction occurs upon exposure to a curing energy, as
defined herein.
[0187] In some of any of the embodiments described herein, the
first composition comprises at least a first material and the
second composition comprises at least a second material, and the at
least first and second materials chemically react to form the
building (e.g., modeling) material upon being contacted and exposed
to curing energy.
[0188] Each of the first and second compositions may comprise
additional materials, which may or may not form a part of the
building (e.g., modeling) material formed upon contacting the first
and second compositions. Such additional materials may participate
in the chemical reaction that forms the building (e.g., modeling)
material. Alternatively, such additional materials induce the
chemical reaction, yet may not form a part of the building (e.g.,
modeling) material. Exemplary such materials include, but are not
limited to, catalysts, initiators, pH-adjusting agents, viscosity
modifying agents, surface tension modifiers, and the like.
[0189] In some of any of the embodiments described herein, the
ratio between materials included in the first composition (e.g., a
first material) and materials included in the second composition
(e.g., a second material), which chemically react to form a
building (e.g., modeling) material, determines the chemical
composition of a building material, for example, by determining the
stoichiometric ratio between in the materials in the product of the
chemical reaction.
[0190] By selecting a ratio of the number of voxels of the first
composition and the number of voxels of the second composition, in
a voxel block where the first and second compositions are dispensed
and chemically react, a chemical composition of the building
material is determined. Selecting different ratios of the first and
the second compositions, and thus of the first and second
materials, for each voxel block, results in building materials of
different chemical compositions in each voxel block.
[0191] This enables obtaining a printed object in which at least
two, and preferably much more, voxel blocks exhibit different
properties, such as chemical properties, mechanical properties,
thermal properties, optical properties, as described in further
detail hereinbelow, based on the selected ratio.
[0192] It is to be noted that embodiments where one or both
compositions comprise both a first material and a second material
that chemically react with one another to form the building (e.g.,
modeling) material are also contemplated. In such embodiments, the
first and second materials do not react, or react slowly, with one
another, without the presence of an additional material, in which
case only one of the compositions further comprises such an
additional material. Alternatively, in such embodiments, the first
and second materials do not react, or react slowly, with one
another, without being subjected to conditions that effect the
reaction. In these embodiments, a ratio of the first and second
materials in each composition is considered for selecting a ratio
of the first and second compositions.
[0193] In some of any of the embodiments described herein, one or
both of the first and second compositions comprises a curable
material, which may form a building (e.g., modeling) material upon
being exposed to a curing energy.
[0194] The curable material is typically a monomer or a mixture of
monomers, but can also be an oligomer or a mixture of oligomers, or
a short-chain polymer or a mixture of such polymers, which
undergoes a chemical reaction to produce a hardened or solidified
(cured) building (e.g., modeling) material.
[0195] It is to be noted that hereinthroughout, whenever the
curable material is referred to as a monomer, it is meant to
encompass also an oligomer, a short-chain polymer, or any mixture
of monomers, oligomers and/or short-chain polymers, unless
specifically indicated otherwise.
[0196] Such a chemical reaction is referred to herein and in the
art as "curing", and typically includes polymerization of the
monomer(s) or oligomer(s) and/or cross-linking of the polymeric
chains (either present before curing or formed in a polymerization
of the monomers or oligomers). The product of a curing reaction,
which is the cured building material, is therefore typically a
polymeric material.
[0197] Herein, a curable material which can be used per se for
forming a building material, when subjected to a suitable curing
energy, optionally in the presence of catalysts or activators or
additional materials that promote or induce curing, is also
referred to as a "base material", as defined herein.
[0198] In some of any of the embodiments described herein, the
curing is effected when a curable material as defined herein is
exposed to a curing energy. The curing energy can be as described
herein.
[0199] In some embodiments, the curing energy comprises heat.
Curing by exposure to heat is also referred to herein and in the
art as "thermal curing".
[0200] A curable material that undergoes a curing reaction when
exposed to heat is referred to herein and in the art as
"thermally-curable material".
[0201] In some of any of the embodiments described herein, a
curable material is a monomer or a mixture of monomers which can
form a polymeric building (e.g., modeling) material upon a
polymerization reaction, when exposed to curing energy at which the
polymerization reaction occurs.
[0202] In some of any of the embodiments described herein, the
first composition comprises a first material which is a curable
material as described herein. The curable material in the first
composition is also referred to herein as a "first curable
material". In some embodiments, the first curable material can be
used per se for forming a building material, when subjected to
suitable reaction conditions (curing energy), optionally in the
presence of catalysts and/or activators.
[0203] In some of any of the embodiments described herein, the
second composition comprises a second material, which participates
in the chemical reaction in which a building material is formed of
the first curable material.
[0204] In some embodiments, the second material, by chemically
reacting with the first material, as defined herein, forms a part
of the cured building material that is formed of the first curable
material, when the first and second materials are exposed to a
curing energy.
[0205] In some of any of the embodiments described herein, the
second material is selected as being capable of modifying a
property (e.g., a chemical, physical, thermal and/or mechanical
property) of a building material formed of the first curable
material, when chemically reacting with the first curable material
upon exposure to a curing energy.
[0206] That is, a building material formed as a result of a
chemical reaction between the first and the second materials has at
least one property that is different from a respective property of
a building material formed upon curing only the first curable
material. This property may also depend on the ratio of the first
and second materials participating in the reaction.
[0207] It is to be noted that, in some embodiments, the different
chemical property is not a result of a physical mixture of the two
compositions but rather a result of a chemical reaction that occurs
between the first and the second compositions upon contacting one
another and being exposed to a curing energy.
[0208] It is to be further noted that both the first and second
compositions are preferably exposed to the same curing energy under
which the chemical reaction occurs. However, different curing
energies, or a combination of curing energies, are also
contemplated.
[0209] It is to be further noted that subjecting the first and
second compositions, including at least the first and second
materials, to chemical reaction, upon contacting the compositions
and exposure to curing energy, results in a polymeric material,
which is different from a polymeric material that is formed when
each of the compositions is subjected alone to curing energy, even
if such polymeric materials are physically mixed. That is, for
example, the second material chemically reacts with the first
material when both are subjected to the same curing energy, and the
obtained polymeric material is different from a polymeric material
formed upon curing a first material, a polymeric material formed
upon curing a second material, and/or a physical mixture of such
polymeric materials. The polymeric material structure and/or
properties also depend on the ratio between the materials getting
in contact and exposed to curing energy.
[0210] As described herein, selecting a ratio of the first and
second compositions determines a chemical composition of the
building (e.g., modeling) material within a voxel block.
[0211] A property of the building (e.g., modeling) material which
is modified by the second material, at a voxel level, can be, for
example, a mechanical property, a physical property or a chemical
property.
[0212] Mechanical properties which can be modified by the second
material include, for example, elasticity, elongation at fracture,
impact resistance at ambient temperature and/or at a low
temperature, Shore hardness, heat deflection temperature (HDT),
tear resistance, tensile strength, impact strength, flexural
strength, creep resistance, and any additional mechanical property
relevant to the formed building material, as would be readily
recognized by those skilled in the art.
[0213] Physical properties which can be modified by the second
material include, for example, optical activity, light absorbance
or transmittance, conductivity, crystallinity, phase transition
temperature (e.g., Tm), and any additional physical property
relevant to the formed building material, as would be readily
recognized by those skilled in the art.
[0214] Chemical properties which can be modified by the second
material include, for example, hydrophobicity, hydrophilicity,
chemical reactivity, solubility, adhesion, surface roughness, and
any additional physical property relevant to the formed building
material, as would be readily recognized by those skilled in the
art.
[0215] In some of any of the embodiments described herein, the
degree by which a property of the building material is modified
(with respect to a building material made of only the first curable
material) is determined by selecting the ratio between the first
and second compositions, and hence between the first and second
materials.
[0216] For example, when a first curable material chemically reacts
with a second material to form a building material that has a
higher elasticity compared to a building material formed of the
first curable material in the absence of the second material, the
ratio between the first and the second compositions determines the
degree of elasticity of the building material, at a selected voxel
block.
[0217] In another example, when a first curable material chemically
reacts with a second material to form a building material that has
a higher hydrophobicity compared to a building material formed of
the first curable material in the absence of the second material,
the ratio between the first and the second composition determines
the degree of hydrophobicity of the building material, at a
selected voxel block.
[0218] In another example, when a first curable material chemically
reacts with a second material to form a building material that has
a higher Impact resistance compared to a building material formed
of the first curable material in the absence of the second
material, the ratio between the first and the second composition
determines the Impact resistance of the building material, at a
selected voxel block.
[0219] Co-Polymerizable Compositions:
[0220] In some of any of the embodiments described herein, the
chemical reaction between the first and second materials is
co-polymerization.
[0221] In these embodiments, a mixture of curable monomers (or
oligomers) is used to form the building (e.g., modeling) material
such that the latter is a co-polymer composed of this mixture of
monomers, e.g., composed of repeating backbone units derived from
one type of monomer (or oligomer) and repeating backbone units of
another type of monomer (or oligomer), covalently linked
therebetween in any order. In some embodiments, a co-polymer is
formed of a mixture of monomers that are curable under the same
curing conditions (e.g., in the presence of the same polymerization
catalysts/activators and/or when exposed to the same curing
energy). A chemical composition of such a co-polymer is determined
by the molar ratio of each of the curable monomers when
polymerization occurs.
[0222] In some of the any of the embodiments described herein the
second material is also a curable material, which is chemically
different from the first curable material. When the second material
is a curable material, it is referred to herein as a second curable
material.
[0223] The second curable material, according to some of these
embodiments is curable under the same conditions and upon exposure
to the same curing energy as the first curable material.
[0224] In some embodiments, both the first and the second curable
materials are monomers, which form a polymeric material under the
same type of polymerization reaction.
[0225] In some embodiments, the first material comprises a first
plurality of monomers and the second material comprises a second
plurality of monomers which is chemically different from the first
plurality of monomers. When contacted and exposed to a suitable
curing energy, and the first and second pluralities of monomers
chemically react with one another to form a co-polymeric building
material.
[0226] In some of these embodiments, one of the compositions
comprises one or more types of monomers (or oligomers), referred to
as a part of the base material, and the other composition comprises
one or more other types of monomers (or oligomers), also referred
to herein as a part of the base of material.
[0227] In these embodiments, both the first and second compositions
comprise a part of the base material, yet each composition
comprises a different part of the base material, and a chemical
reaction between these parts occurs for forming the building (e.g.,
modeling) material.
[0228] When the two compositions chemically react, the building
(e.g., modeling) material is formed via co-polymerization of the
monomers (or oligomers).
[0229] In these embodiments, both the first and second materials,
in the first and second compositions, form the base material.
[0230] These embodiments are described herein interchangeably as
referring to a first composition which comprises a part of the base
material and a second composition which comprises another part of
the base material. One of the parts of the base material can also
be regarded as a second material that chemical reacts with the part
of the base material in the other composition, to form the building
(e.g., modeling) material.
[0231] In these embodiments, the second material forms a part of
the building (e.g., modeling) material upon chemically reacting
with the base material.
[0232] In exemplary embodiments, the second material is a second
curable material which co-polymerizes with the first curable
material, as described herein, and the second curable material
comprises monomers which are more hydrophobic compared to the first
curable material, thus modifying the hydrophobicity of the building
material.
[0233] For example, the second curable material may comprise
monomers which are substituted by a hydrophobic moiety, whereby the
hydrophobic moiety does not participate in the polymerization of
the monomers when exposed to curing energy. When contacting such a
second curable material with a first curable material which
comprises monomers that do not have a hydrophobic moiety, exposing
to curing energy, and selecting a ratio of the first and second
compositions, the hydrophobicity of the co-polymer that forms the
building material can be digitally controlled.
[0234] Similarly, the second curable material may comprise monomers
which are substituted by a chemically-reactive group, or a
conductive group (e.g., a charged group), or a hydrophilic group,
or a light-absorbing group, as defined herein, such that selecting
a ratio of the first and second compositions results in modifying a
respective property of a building material made of the first
curable material.
[0235] In alternative embodiments, a mixture of curable monomers
(or oligomers) is used to form the building (e.g., modeling)
material, whereby a polymerized material formed of at least one of
the curable materials interacts with a polymerized material formed
of another (e.g., a second curable material) by, for example,
cross-linking. A chemical composition of such a co-polymer is
determined by the molar ratio of each of the curable monomers when
polymerization occurs.
[0236] In further alternative embodiments, a mixture of curable
materials is used to form the building material and at least two of
the curable materials are curable under the different curing
conditions (e.g., in the presence of the different polymerization
catalysts/activators and/or when exposed to a different curing
energy).
[0237] In some of the any of the embodiments described herein the
first composition comprises a first curable material and the second
composition comprises a second curable material, which is
chemically different from the first curable material.
[0238] The second curable material, according to some of these
embodiments is curable under curing conditions which are different
from the curing conditions under which the first curable material
is curable.
[0239] In some embodiments, both the first and the second curable
materials are monomers, which form a polymeric material via
different polymerization reactions.
[0240] In some embodiments, the first material comprises a first
plurality of monomers which are polymerizable by a first
polymerization reaction and the second material comprises a second
plurality of monomers which are chemically different from the first
plurality of monomers and which are polymerizable by a second
polymeric reaction which is different from the first polymerization
reaction.
[0241] For example, the first polymerization reaction can be a
free-radical polymerization, a cationic polymerization, or an
anionic polymerization, and the second polymerization reaction can
be a ring opening polymerization such as anionic ROP, or vice
versa. Alternatively, the first polymerization reaction can be a
free-radical polymerization, and the second polymerization reaction
can be a cationic polymerization, or an anionic polymerization, or
vice versa. Further alternatively, the first and polymerization
reactions can be the same reactions, but the first polymerization
reaction is a photoinduced polymerization and the second
polymerization reaction is thermally-induced polymerization, or
vice versa. Any other combination of different polymerization
reactions is contemplated.
[0242] Exemplary compositions that are usable in these embodiments,
while digitally controlling the properties of the obtained building
material at the voxel level, include compositions similar to those
disclosed in International Patent Application Publication No. WO
2013/128452.
[0243] Exemplary compositions that are usable in these embodiments,
while digitally controlling the properties of the obtained building
material at the voxel level, include a first composition that
comprises a first curable material that is polymerizable by
photo-induced polymerization, for example, cationic polymerization,
such as a monomer usable for forming an epoxy resin, and a second
curable material that is polymerizable by a ring opening
polymerization, for example, a thermally-induced anion ROP, such as
a lactam or lactone (e.g.,caprolactone). Epoxy resins formed upon
exposure to a suitable electromagnetic irradiation may chemical
interact with polyester or polyamide materials forms upon exposure
to a suitable thermal curing by cross-linking. The formed building
material features properties that can be digitally controlled at
the voxel level.
[0244] When contacted and exposed to a suitable curing energy, the
first and second pluralities of monomers chemically react with one
another to form a building material that comprises two polymerized
materials which are chemically interacted with one another. The two
polymerized materials, one formed of the first curable material and
the other formed of the second polymerized material, can be
chemically interacted by means of forming a co-polymer, as
described herein, or, for example, by means of covalent
cross-linking therebetween.
[0245] These embodiments are also described herein interchangeably
as referring to a first composition which comprises a part of the
base material and a second composition which comprises another part
of the base material. One of the parts of the base material can
also be regarded as a second material that chemical reacts with the
part of the base material in the other composition, to form the
building (e.g., modeling) material.
[0246] In these embodiments, the second material forms a part of
the building (e.g., modeling) material upon chemically reacting
with the base material.
[0247] In exemplary embodiments, the second material is a second
curable material which is cross-linked by the first curable
material, or by a polymer or an oligomer formed upon exposing the
first material to a suitable curing energy. Such cross-linking
modifies one or more of the chemical, physical and mechanical
properties of the first and/or second materials.
[0248] When contacting such first and second curable materials,
exposing to suitable curing energy or energies, and selecting a
ratio of the first and second compositions, various properties of
the obtained building material can be digitally controlled.
[0249] Non Co-Polymerizable Compositions:
[0250] In some of any of the embodiments described herein, the
first curable material, as defined herein, forms the building
(e.g., modeling) material by chemically reacting with a second
material that is not a curable material, or is not a base material
or a part thereof, namely, it does not constitute the repeating
backbone units of the polymeric building (e.g., modeling)
material.
[0251] In these embodiments, the curing of the first curable
material occurs in the presence of a second material, which
chemically reacts with the curable material when the materials are
contacted and exposed to a curing energy, as defined herein, and
forms a part of the building (e.g., modeling) material.
[0252] When the first curable material in a monomer that
polymerizes when exposed to curing energy, the second material can
react chemically with the first curable material before the
polymerization, e.g., with a monomer, during the polymerization,
e.g., with an intermediate oligomer, or with one or more polymeric
chains of the polymeric material obtained by the curing.
[0253] In some embodiments, by chemically interacting with the
first curable material, the second material forms a part of the
building (e.g., modeling) material obtained upon exposing the first
curable material to curing energy.
[0254] In some of these embodiments, the first composition
comprises the first curable material, and another composition
(e.g., the second composition) comprises the second material which
chemically reacts with the first curable material to form the
building (e.g., modeling) material.
[0255] In some of these embodiments, the first curable material
comprises one material, e.g., one type of monomers or oligomers, or
short-chain polymers, and a modeling material is formed by exposing
the first material to curing energy, such that curing results in
polymeric chains that are substantially comprised of repeating
backbone units of the first curable material, covalently attached
to one another, without being chemically interrupted or
cross-linked by other backbone units, and without reacting with
other materials (e.g., chemically different monomers) to form the
backbone unit of the polymeric chains.
[0256] In some of any of the embodiments described herein, the
first material is a curable material and the second material is a
cross-linking agent that chemically reacts with the first curable
material by cross-linking the polymeric material formed upon curing
the first curable material.
[0257] Alternatively, the first curable material comprises a
mixture of curable materials (e.g., mixture of chemically different
monomers), as described herein. In some embodiments, the second
material is such that promotes the curing of the first curable
material. Such materials are referred to herein and in the as art
as "promoters" or "activators".
[0258] Herein, by "promoting a curing" it is meant that the curing
does not occur, or occurs slowly, in the absence of a promoter, yet
occurs or is accelerated in the presence of a promoter.
[0259] Herein, a "promoter" or "activator" is to be distinguished
from a catalyst or an initiator in that it reacts chemically, as
defined herein, with a curable material, and hence forms a part of
the final building material formed upon exposing the curable
material to curing energy.
[0260] A promoter can be utilized in a chemical reaction at a
ratio, relative to curable material, that is 1:1, yet, is
preferably lower than 1:1, for example, 1:1.5, 1:2, 1:3, 1:4, 1:5,
and so forth, and up to 1:100, including any intermediate value or
subranges between 1:1 and 1:100. Preferably, the ratio ranges from
1:1 to 1:10, and can be, for example, 1:2, 2:3, 4:6, 1:5, etc.
[0261] While promoters are often used to accelerate a
polymerization reaction, that is, to affect the reaction kinetics,
some promoters are designed and/or selected to impart to the final
polymeric material additional properties, or to modify properties
of the polymeric material. As an example, a promoter can be a
material that forms a block-copolymer when reacting with a monomer
(or an oligomer, or a mixture of monomers and/or oligomers), upon
exposure to curing energy. In another example, the promoter
introduces to the formed polymeric material a moiety that imparts
or modifies a property in the polymeric material as described
herein. In another example, the promoter induces cross-linking of
the formed polymeric material and thereby modifies a property in
the polymeric material as described herein.
[0262] By selecting the ratio of the first and second compositions,
and thus the ratio of the first curable material and the second
material, which is a promoter, for each voxel block, the property
or properties imparted or modified by the promoter is determined,
and different polymeric materials (building materials), which
exhibit a different degree of such property or properties, are
obtained, for each voxel block.
[0263] In exemplary embodiments, the second material promotes a
curing (e.g., polymerization) of a curable material, as described
herein, and comprises a moiety such as, for example, an elastomeric
chemical moiety, and optically-active chemical moiety, a
light-absorbing chemical moiety, a hydrophobic chemical moiety, a
hydrophilic chemical moiety and/or a reactive chemical moiety.
[0264] By chemically reacting with the curable material and forming
a part of the building material upon exposure to curing energy,
such a moiety is introduced to the polymeric material formed upon
curing, and the respective property of the building material is
modified.
[0265] Thermally-Curable Compositions:
[0266] In some embodiments of any of the embodiments described
herein, any of the first and second materials described herein
chemically react with one another upon being exposed to thermal
curing, that is, upon being exposed to heat.
[0267] In some embodiments of any of the embodiments described
herein, at least one of the first and second compositions comprises
a thermally-curable material.
[0268] According to these embodiments, the building material is
referred to as a thermally-cured building material.
[0269] A thermally-cured building material, according to
embodiments of the present invention, is obtained by exposing a
thermally-curable material to heat.
[0270] Thermally-curable materials are materials which harden or
solidify upon exposure to heat. Such materials are typically
monomers, oligomers or short-chain polymers, or a mixture thereof,
which undergo a chemical reaction such as polymerization and/or
cross-linking, upon exposure to heat, to produce a hardened or
solidified material, typically a polymeric material.
[0271] In some embodiments, a thermally-curable material is a
monomer, an oligomer, or a mixture of monomers and/or oligomers,
which undergoes polymerization or co-polymerization or
cross-linking, when exposed to heat, as described herein.
[0272] Such a reaction is referred to herein as "thermally-induced
polymerization" or "thermal curing".
[0273] In these embodiments, the first and/or second material is a
thermally-curable monomer or mixture of monomers and a building
material formed therefrom is a thermally-cured polymer or
co-polymer, respectively.
[0274] Exemplary thermally-induced polymerization reactions which
require exposure to heat include, but are not limited to,
ring-opening polymerization, anionic polymerization, and
polycondensation.
[0275] Exemplary polymers that are typically obtained by thermal
curing include, but are not limited to, polyamides, polyurethanes,
and polyesters.
[0276] According to these embodiments, the thermally-curable
material is selected suitable for undergoing any of the
thermally-induced polymerization reactions described herein, and/or
for forming any of the thermally-cured polymeric materials
described herein.
[0277] In some embodiments, the thermally-curable material is a
mixture of thermally-curable monomers, which upon exposure to heat
co-polymerize via a thermally-induced polymerization reaction as
described herein, to form a polymeric building material.
[0278] In some of these embodiments, the first and second
compositions comprise a first and second thermally-curable
materials, respectively, as described herein, which form a
co-polymeric building material upon being contacted and exposed to
heat.
[0279] In some embodiments, the thermally-induced polymerization
reaction involves, in addition to a thermally-curable material, a
second material which chemically reacts with the thermally-curable
material during the thermally-induced curing, and upon being
contacted with the thermally-curable material and exposure to heat,
such that the second material forms a part of the building material
formed upon thermally-induced polymerization, as described
herein.
[0280] In some embodiments, the thermally-curable material and the
second material react chemically with one another upon being
contacted and exposed to heat.
[0281] In some embodiments, the second material is such that
promotes a thermally-induced polymerization of the
thermally-curable material, such as a promoter, as described
herein.
[0282] In some of any of the embodiments described herein, the
thermally-curable material polymerizes by a thermally-induced ring
opening polymerization, such as an anionic ring opening
polymerization.
[0283] In some of any of the embodiments described herein, the
thermally-cured building material is a polyester, and the
thermally-curable material is a precursor of the polyester.
[0284] Exemplary precursors of polyesters that polymerize by
thermally-induced ring-opening polymerization are lactones, for
example, a caprolactone.
[0285] In some of any of the embodiments described herein, the
thermally-cured building material is a polyamide, and the
thermally-curable material is a precursor of the polyamide.
[0286] Exemplary precursors of polyamides that polymerize by
thermally-induced ring-opening polymerization are lactams.
[0287] An exemplary, commonly used lactam is a caprolactam, and
more specifically .epsilon.-caprolactam.
[0288] Exemplary such thermally-curable monomers are lactams, which
form upon thermally-induced polymerization polyamides such as
Nylon6. Embodiments in which the thermally-cured building (e.g.,
modeling) material is a polyamide are discussed in the further
detail hereinunder.
[0289] In some of these embodiments, the second material is a
promoter of an anionic ring opening polymerization of caprolactam,
which chemically reacts with the caprolactam upon exposure to heat.
Such promoters are described in further detail hereinunder.
[0290] In some of any of the embodiments related to a method in
which a thermally-cured building material is formed, the method
further comprises exposing the dispensed layers to heat, as
described herein.
[0291] When exposure to heat is effected by heat inducing
radiation, it is preferable that at least some of the materials
included in the first and/or second compositions and chemically
reacting with one another are capable of absorbing the
heat-inducing radiation.
[0292] In some embodiments, when one or more of these materials,
e.g., the thermally-curable material and/or the second material, as
described herein, do not absorb heat-inducing radiation, an IR dye
or pigment are added to one or both of the first and second
composition, as needed.
[0293] Polyamide-Containing Building Materials:
[0294] In some of any of the embodiments described herein, the
building material is a polyamide-containing polymeric material, and
the first curable material is a thermally-curable precursor of the
polyamide.
[0295] By "polyamide-containing polymeric material" it is meant a
polymeric material, at least a portion of which is a polyamide that
is formed by polymerization of a precursor thereof. That is, the
final polymeric material comprises at least one polymeric chain
that is a polymerized precursor of a polyamide, as described
herein.
[0296] Materials and compositions comprising such materials which
are usable for forming polyamide-containing polymeric materials are
also referred herein as "polyamide-forming materials".
[0297] Exemplary precursors of polyamides that polymerize by
thermally-induced ring-opening polymerization are lactams, such as
caprolactam, piperidone, pyrrolidone and laurolactam.
[0298] An exemplary, commonly used, lactam is a caprolactam, and
more specifically .epsilon.-caprolactam. Whenever "caprolactam" is
mentioned herein, c-caprolactam is encompassed.
[0299] In some of any of the embodiments described herein for
polyamide-forming materials, the lactam is caprolactam, laurolactam
or a mixture thereof. In some embodiments, the lactam is
caprolactam.
[0300] As discussed hereinabove polyamides of the Nylon6 type are
formed by polymerization of caprolactam. Such a polymerization is a
thermally-induced ring opening polymerization, which can undergo
several pathways:
[0301] Self polycondensation (typically by heating at a temperature
of 260.degree. C. for a few hours); cationic polycondensation
(typically in an acidic aqueous solution, by heating at a
temperature of 250.degree. C. for a few hours); and anionic
polymerization (typically by heating at 130-160.degree. C., for up
to 30 minutes, and even for less than 1 minute).
[0302] An anionic ring opening polymerization of caprolactam is
considered the most industrially applicable methodology for
production Nylon6. This reaction takes place in the presence of a
catalyst, typically a strong base or a product of a reaction of a
strong base and caprolactam, as described hereinafter, and a
promoter or activator, for example, an N-acylcaprolactam.
[0303] Scheme 1 below presents an exemplary synthetic pathway for
polymerization of caprolactam via anionic ROP using an
N-acylcaprolctam as an activator.
##STR00004##
[0304] In step (i), initiation of the reaction is effected by
reacting caprolactam with a strong base. This step can be performed
in situ, such that the base (e.g., sodium) serves as catalyst, or
that sodium caprolactam is added as the catalyst.
[0305] Commonly used catalysts include sodium caprolactam and
caprolactam MgBr (magnesium bromide caprolactam).
[0306] In step (ii), the anionic caprolactam reacts with an N-acyl
caprolactam (or any other activator) to form an intermediate anion,
whereby the activator forms a part of this intermediate anion. The
polymerization then proceeds by step-by-step linking amide units to
the intermediate anion.
[0307] Commonly used activators include N-acetylcaprolactam and
N,N'-isophthaloyl-bis-caprolactam, respectively:
##STR00005##
[0308] Other lactam activators include, lactams N-substituted by
electrophilic (electron-withdrawing) moieties, aliphatic
diisocyanates, aromatic diisocyanates, polyisocyanates, aliphatic
diacyl halides and aromatic diacyl halides, and any combination
thereof.
[0309] Lactams N-substituted by electrophilic moieties include for
example acyllactams.
[0310] Aliphatic diisocyanates include compounds such as butylene
diisocyanate, hexamethylene diisocyanate, octamethylene
diisocyanate, decamethylene diisocyanate, undodecamethylene
diisocyanate, dodecamethylene diisocyanate,
4,4'-methylenebis(cyclohexyl isocyanate), isophorone
diisocyanate.
[0311] Aromatic diisocyanates include compounds such as tolyl
diisocyanate, and 4,4'-methlenebis(phenyl)isocyanate.
[0312] Polyisocyanates include, for example,isocyanurates of
hexamethylene diisocyanate, allophanates (for example ethyl
allophanate).
[0313] Aliphatic diacyl halides include, for example, compounds
such as butylene diacyl chloride, butylene diacyl bromide,
hexamethylene diacyl chloride, hexamethylene diacyl bromide,
octamethylene diacyl chloride, octamethylene diacyl bromide,
decamethylene diacyl chloride, decamethylene diacyl bromide,
dodecamethylene diacyl chloride, dodecamethylene diacyl bromide,
4,4'-ethylenebis(cyclohexyl acid chloride),
4,4'-methylenebis(cyclohexyl acid bromide), isophorone diacyl
chloride, isophorone diacyl bromide.
[0314] Aromatic diacyl halides include, for example, compounds such
as tolyhnethylene diacyl chloride, tolylmethylene diacyl chloride,
4,4'-methylenebis(phenyl)acid chloride,
4,4'-methylenebis(phenyl)acid bromide.
[0315] Additional activators include, for example, acyl lactams,
such as disclosed in EP Patent No. 1449865, oxazolines such as
disclosed in EP Patent No. 0786482, ethylenebisamides such as
disclosed in U.S. Patent Application Publication No. 2010/0113661,
isocyanates, and masked (capped, e.g., caprolactam-blocked)
isocyanate compounds, such as, for example, hexamethylene
diisocyanate (HDI).
[0316] Other liquid activator systems for anionic lactam
polymerization are known in which isocyanate compounds are mixed
with pyrrolidone compounds, e.g. N-methyl pyrrolidone or N-ethyl
pyrrolidone, as described, for example, in EP Patent No. 0167907.
EP Patent Application Nos. 0134616 and 0135233 disclose
N-substituted carbamoyl-lactam compounds suitable as promoters or
activators for anionic polymerization of lactams.
[0317] In some embodiments, the activator is used either per se or
in a solution. Ire some embodiments, the activator is dissolved in
the lactam (e.g., caprolactam).
[0318] As seen in Scheme 1, the activator serves as a base unit to
which amide moieties are added to form the final polymer, and hence
forms a part of the final polymeric material.
[0319] The amount of the activator defines the number of growing
chains, since every activator molecule represents the initial
member of a polymer chain. The molar ratio of the lactam to the
activator can be varied within wide limits can be in the range from
1:1 to 10 000:1, preferably in the range from 5:1 to 2000:1, and
more preferably in the range from 20:1 to 1000:1.
[0320] In some embodiments, the ratio of the lactam and the
activator can determine a property of the obtained polyamide
material.
[0321] In exemplary embodiments of any of the embodiments described
herein, the method is effected while utilizing a first composition
which comprises a lactam (e.g., caprolactam) and a second
composition which comprises a second material which chemically
reacts with the lactam upon exposure to heat to form the building
material by anionic ring opening polymerization.
[0322] In some of these embodiments, the second material is a
promoter of a ring opening polymerization (ROP) (e.g., an anionic
ring opening polymerization) of the lactam (an activator as
described herein).
[0323] In some of these embodiments, the promoter is selected as
capable of modifying a property of the building material, as
described herein.
[0324] In some of these embodiments, a degree of the modifying is
determined by selecting the ratio of the first and second
compositions.
[0325] Thus, a method as described herein can be utilized for
forming objects made by utilizing a polyamide-containing building
(e.g., modeling) material, by selecting a promoter which forms a
part of a polyamide formed from a lactam such as caprolactam, and
modifies a property of this polyamide-containing polymer, whereby a
chemical composition of the building material, and hence one or
more properties thereof, are determined, at a voxel level, by
selecting a ratio between a first composition which comprises the
lactam and the second composition which comprises the promoter.
[0326] Many promoters for anionic ROP of caprolactam, which affect
a property, and particularly a mechanical property, of the formed
polymeric material are known in the art, and all such promoters are
contemplated by embodiments of the present invention.
[0327] Non-limiting exemplary promoters, referred to also as
"activators", which are usable in the context of these embodiments
of the present invention are described, for example, in U.S. Pat.
No. 3,304,291, which discloses activators consisting of organic
nitrogen compounds having on at least 2 to 12 carbon hydrocarbon
radical being an N-substituted compound of at least one urea,
thiourea or guanidine radical; U.S. Pat. No. 3,770,689, which
discloses polyether promoters in which the polymer chains are
permanently terminated on at least one end by a promoter function,
whereby the promoter functional groups or substituents are similar
to monomeric promoters such as acid-chloride groups, isocyanates,
N-carbonyl-lactam groups, imide groups, N-carbonyl-sulfonamide
groups, N-carbonyl-urea groups and acid-anhydride groups; GB Patent
No. 1,067,153 which discloses an isocyanate capped polypropylene
glycol; in U.S. Pat. Nos. 3,862,262, 4,031,164, 4,034,015, and
4,223,112, which disclose additional polyol-polyacyl polymers used
as promoters and forming Nylon block co-polymers or terpolymers;
U.S. Pat. No. 9,139,752 which discloses capped (lactam-blocked)
isocyanate as an activator (promoter); U.S. Patent Application
Publication No. 2012/0283406 which discloses an aliphatic or
alicyclic di-or multi-isocyanate compound; and EP Patent
Application No. 2801588 which discloses (optionally
caprolactam-blocked) isocyanate compounds based on hexamethylene
diisocyanate (HDI). Any of the activators described hereinabove are
also contemplated.
[0328] In some of any of the embodiments described herein for a
method in which the curable material is a lactam such as
caprolactam, a second material is a promoter of caprolactam anionic
ROP, which comprises one or more moieties that chemically interact
with the lactam (e.g., caprolactam), and thus forms a part of the
polyamide material formed upon curing the caprolactam.
[0329] In some of any of the embodiments described herein, the
promoter further comprises an additional moiety which, when present
in the obtained polymeric material, imparts or modifies a property
of the polymeric (polyamide) material, as described herein. For
example, the promoter can further comprise a moiety that imparts or
modifies a property of the polyamide material compared to a Nylon6
polyamide made of caprolactam and an activator such as, for
example, N-acetyl caprolactam.
[0330] In some embodiments, the second material is other than
N-acetyl caprolactam. This commonly used activator, while
accelerating the anionic polymerization reaction, does not include
a moiety that affects a property of a formed polyamide-containing
polymer.
[0331] Exemplary moieties that impart or modify a property of a
polymeric material when present in a promoter according to these
embodiments include, but are not limited to, impact modifying
moieties, elastomeric moieties, optically-active moieties,
light-absorbing moieties, conductive moieties, metal-chelating
moieties, hydrophobic moieties, hydrophilic moieties and/or a
chemically-reactive moieties, as these are defined herein.
[0332] Moieties capable of effecting cross-linking of polyamide
chains are an example of moieties that affect properties of the
formed polyamide, for example, impact resistance, elasticity,
stiffness, and the like.
[0333] Multifunctional moieties to which polyamide chains are
attached are also an example of moieties that affect properties of
the formed polyamide, for example, impact resistance, elasticity,
stiffness, and the like. Multifunctional activators, having two or
preferably three or more groups that attach to the lactam are an
example of materials that form such moieties.
[0334] An exemplary second material according to these embodiments
can be generally represented by Formula I:
##STR00006##
[0335] wherein:
[0336] A is the additional moiety that imparts or modifies a
property of the polyamide-containing polymer, as described herein;
R is N-acyl lactam, which is attached to a polyamide chain formed
of the lactam; and n is a positive integer.
[0337] In some of any of the embodiments described herein for a
lactam such as caprolactam, the second material comprises at least
two N-acyl lactam groups, such that in Formula I, for example, n is
2 or is greater than 2 (e.g., 3 or 4).
[0338] An N-acyl lactam group is described herein as:
##STR00007##
[0339] wherein m can be 1, 2, 3, 4, or 5. In N-acetyl caprolactam,
m=3.
[0340] Exemplary promoters which are usable in the context of the
caprolactam embodiments described herein as a second material can
be collectively represented by Formula II:
##STR00008##
[0341] wherein A is the additional moiety that imparts or modifies
a property of the polyamide-containing polymer; L is absent or is a
linking moiety; and A' is absent or is another additional moiety,
being the same or different from the moiety A.
[0342] In some embodiments, A is a hydrocarbon moiety, of e.g.,
1-30 carbon atoms in length. The hydrocarbon moiety can be linear
and/or cyclic, saturated or unsaturated, substituted or
unsubstituted, and may be interrupted by one or more heteroatoms
(e.g., O, N, or S). The hydrocarbon moiety can be composed of
alkyl, alkenyl, alkynyl, cycloalkyl, aryl or any combination of
these groups.
[0343] In a non-limiting example, A is an alkyl (alkylene chain) of
6 carbon atoms, terminating at both ends by amine groups, and the
promoter is:
##STR00009##
[0344] In some embodiments, A comprises a hydrocarbon moiety, as
described herein, interrupted by one or more polymeric
moieties.
[0345] In some embodiments, L is absent and in some embodiments L
is a linking moiety connecting A to A'. The linking moiety can be a
hydrocarbon moiety, as described herein, a polymeric moiety, or can
comprise both, as described herein for A.
[0346] In some of these embodiments, A is a branched moiety,
connected to L via a branching unit.
[0347] A' is as described herein for A.
[0348] In some embodiments, A' comprises at least one N-acyl lactam
moiety, connected directly to the linking moiety, or to an A
moiety.
[0349] An exemplary such polymeric promoter is presented in the
Examples section that follows. It is to be noted that other
structures that comprise 1, 2 or more polymeric moieties that
terminate with N-acyl lactam are usable as a second material as
described herein.
[0350] In some embodiments, a polymeric moiety as described in any
of these embodiments, is a poly(alkyene glycol) moiety (e.g.,
poly(ethylene glycol) or poly(propyleneglycol)), a polyacyl moiety,
a poloxamer, and any combination thereof.
[0351] Such polymeric moieties, when included in the polymeric
material obtained upon curing, typically modify a mechanical
property (e.g., as described herein) of the obtained
polyamide-containing polymer (the building material).
[0352] Another exemplary second material according to these
embodiments can be generally represented by Formula III:
##STR00010##
[0353] wherein:
[0354] A is the additional moiety that imparts or modifies a
property of the polyamide-containing polymer, as described herein;
R is an isocyanate group, which reacts with the lactam; and n is a
positive integer.
[0355] In some of any of the embodiments described herein for a
lactam such as caprolactam, the second material comprises at least
two isocyanate groups, such that in Formula I, for example, n is 2
or is greater than 2 (e.g., 3 or 4).
[0356] In some embodiments, A is a hydrocarbon moiety, of e.g.,
1-30 carbon atoms in length. The hydrocarbon moiety can be linear
and/or cyclic, saturated or unsaturated, substituted or
unsubstituted, and may be interrupted by one or more heteroatoms
(e.g., O, N, or S). The hydrocarbon moiety can be composed of
alkyl, alkenyl, alkynyl, cycloalkyl, aryl or any combination of
these groups.
[0357] In a non-limiting example, A is an alkyl (alkylene chain) of
6 carbon atoms, terminating at both ends by isocyanate groups.
[0358] In a non-limiting example, A is an isocyanurate moiety,
substituted by 1, 2 or 3 isocyanate-containing moieties, for
example, an alkyl terminated by isocyanate.
[0359] In some embodiments, A comprises a hydrocarbon moiety, as
described herein, interrupted by one or more polymeric
moieties.
[0360] In some embodiments, A is or comprises a polymeric
moiety.
[0361] In some embodiments, a polymeric moiety as described in any
of these embodiments, is or comprises a poly(alkyene glycol) moiety
(e.g., poly(ethylene glycol) or poly(propyleneglycol)), a polyacyl
moiety, a poloxamer, a polyol, and any combination thereof. Such
polymeric moieties, when included in the polymeric material
obtained upon curing, may modify a mechanical property (e.g., as
described herein) of the obtained polyamide-containing polymer (the
building material).
[0362] Any of the isocyanate-containing activators described herein
can be used per se or can be blocked, for example,
caprolactam-blocked wherein and in the art, the phrase "capped
isocyanate" is also referred to interchangeably as "blocked
isocyanate" and describes an isocyanate group which has been
blocked by another functional group, e.g. a caprolactam group. This
group typically acts as "protective group", blocking the isocyanate
group during the reaction.
[0363] In some of any of the embodiments provided herein for
caprolactam, the first composition further comprises a catalyst for
inducing anionic polymerization of caprolactam. Any catalyst known
in the art is usable in the context of these embodiments, including
the exemplary catalysts sodium caprolactam and magnesium bromide
caprolactam, which are also referred to herein and in the art as
sodium caprolactamate and magnesium bromide caprolactamate,
respectively.
[0364] Additional exemplary catalysts usable in polyamide forming
compositions as described herein include, but are not limited to,
alkali metal caprolactamates such as the above-mentioned sodium
caprolactamate, as well as potassium caprolactamate; alkaline earth
metal caprolactamates such as the above-mentioned bromide magnesium
caprolactamate, chloride magnesium caprolactamate, and magnesium
biscaprolactamate; alkali metal bases, for example sodium or sodium
bases such as sodium hydride, sodium, sodium hydroxide, sodium
methoxide, sodium ethoxide, sodium propoxide, sodium butoxide, for
example potassium or potassium bases such as potassium hydride,
potassium, potassium hydroxide, potassium methoxide, potassium
ethoxide, potassium propoxide, potassium butoxide and mixtures
thereof.
[0365] In some embodiments, the catalyst is sodium hydride, sodium,
sodium caprolactamate and mixtures thereof.
[0366] The catalyst is preferably introduced into a caprolactam (or
any other lactam) melt in which it can dissolve.
[0367] In some of any of the embodiments provided herein for
caprolactam, the second composition is devoid of caprolactam.
[0368] In some of any of the embodiments provided herein for
caprolactam, any of the embodiments described herein for chemical
reaction between the first and second materials upon exposure to
heat, and any combination thereof, are contemplated.
[0369] In some of any of the embodiments provided herein for
caprolactam, any of the embodiments described herein for a second
material being a promoter for modifying a property of a building
material made of a curable material, and any combination thereof,
are contemplated.
[0370] Additional Exemplary Compositions:
[0371] In some of any of the embodiments described herein, the
curable material(s) are selected so as to form a polymeric material
that comprises a polyester, a polycarbonate, a polyurethane, a
polyether urethane, a polyether carbonate, a polyester carbonate, a
polyester urethane, a polyanhydride, a polyamide, a polyacid, and
copolymers thereof.
[0372] Curable materials that form such polymeric materials upon
exposure to curing energy would be known to any person skilled in
the art.
[0373] In some of any of the embodiments described herein, the
curable materials are selected to form a polymeric (or
co-polymeric) material upon exposure to heat.
[0374] In some of any of the embodiments described herein, the
curable materials are selected to form a polymeric material upon
exposure to heat, via an anionic polymerization.
[0375] In some of any of the embodiments described herein, the
curable materials are selected to form a polymeric material upon
exposure to heat, via a ring opening polymerization, e.g., an
anionic ring opening polymerization.
[0376] In some of any of the embodiments described herein, the
second material comprises a moiety (a component) that imparts or
modifies a property of the polymeric material made of a curable
material, as described herein.
[0377] In some embodiments, the property is a mechanical property
and in some embodiments, it is the impact resistance.
[0378] Herein throughout and in the art, the phrase "impact
resistance", which is also referred to interchangeably, herein and
in the art, as "impact strength" or simply as "impact", describes
the resistance of a material to fracture by a mechanical impact,
and is expressed in terms of the amount of energy absorbed by the
material before complete fracture. Impact resistance can be
measured using, for example, the ASTM D256-06 standard Izod impact
testing (also known as "Izod notched impact", or as "Izod impact"),
and is expressed as J/m.
[0379] In these embodiments, the second material can be regarded as
an impact modifying agent, and the ratio between the first and the
second compositions determines an impact resistance property of the
building material at a voxel block.
[0380] Moieties that may affect impact resistance (also referred to
as impact modifying agents, or simply as impact modifiers) include,
for example, elastomeric moieties, such as, but not limited to, a
moiety derived from an elastomeric oligomer, polymer and/or
co-polymer, and/or any other moiety that forms, for example, block
polymers or co-polymers, within the polymeric network.
[0381] In some embodiments, the property is a physical property and
in some embodiments, it is the heat deflection temperature.
[0382] Herein throughout and in the art, the phrase "heat
deflection temperature", or HDT, describes the temperature at which
a specimen of cured material deforms under a specified load.
Determination of HDT can be performed using the procedure outlines
in ASTM D648-06/D648-07.
[0383] As described herein, other moieties can be included in the
second material for affecting a property of the building material,
as described herein.
[0384] Optically-active moieties include, for example, moieties
that may rotate the plane of linearly polarized light about the
direction of motion as the light travels therethrough.
[0385] Light-absorbing moieties include, for example, chromophore
moieties, including dye moieties, fluorescent moieties,
phosphorescent moieties, and the light.
[0386] Conductance modifying moieties, referred to herein also as
conductive moieties, include, for example, conjugated moieties that
allow charge transfer therethrough.
[0387] Metal chelating moieties include moieties that can form
organometallic complexes with various metals or metal ions.
[0388] Hydrophobic moieties include hydrocarbon moieties, as
described herein, containing more than 4 carbon atoms, preferably
more than 6 carbon atoms, and more preferably more than 8 carbon
atoms.
[0389] Hydrophilic moieties include, for example, hydrocarbons, as
described herein, substituted by one, and preferably more, e.g., 2,
3, 4, 5, 6, 7, 8, 10, and even more, hydrophilic moieties such as
hydroxyl, carboxylic acid, amine, and the like. The inclusion of
hydrophilic moieties may affect the swelling properties of the
building material (e.g., a modeling material or a support
material).
[0390] Chemically-reactive moieties include, for example, moieties
or groups that readily react with another moiety or compound to
form a bond, as described herein. Such moieties allow for attaching
an additional material to selected portions of a printed
object.
[0391] In embodiments pertaining to co-polymerizable materials, the
second material may include a curable material which is a monomer
similar to the first curable material, which is substituted by any
one of the moieties described herein. By controlling the ratio of
the first and the second compositions, the object features variable
degrees of the property or properties imparted by these moieties at
the voxel level, as described herein.
[0392] In embodiments pertaining to non co-polymerizable materials,
one or the first and second composition may include materials that
chemically interact with a curable material (the base material) so
as to form a part of the building material, and these materials are
or include any one of the moieties described herein. By controlling
the ratio of the first and the second compositions, the object
features variable degrees of the property or properties imparted by
these moieties at the voxel level, as described herein.
[0393] In some of any of the embodiments described herein, the
first and/or second compositions may comprise additional agents
which may affect the formation of the building (e.g., modeling)
material (e.g., affect the curing rate, the required curing energy
and/or affect physical, chemical and/or mechanical property of the
material).
[0394] Such agents include, but are not limited to, amine boosters,
as described herein.
[0395] Exemplary amine boosters include polyalkyleneimines, for
example, hyperbranched polyalkyleneimines or hyperbranched
poethyleneimines.
[0396] Polyalkyleneimines, for example, polyethyleneimines can have
an average molecular weight (weight average) in the range of from
100 to 3,000,000 grams/mol, or from 500 to 50,000 grams/mol, as
determined, for example, via light scattering.
[0397] The polymers can have an amino functionality of primary
and/or secondary amino groups in the range of from 10 to 70,000,
for example, from 10 to 10,000 per chain, preferably in the range
of from 20 to 500 per chain. Amino functionality can be determined
from the distribution of the amino groups as is determinable from
NMR measurements.
[0398] Polyalkyleneimines can be homopolymers or copolymers. The
homopolymers are generally obtainable by polymerization of
ethyleneimine (aziridine) in aqueous or organic solution in the
presence of acid-detaching compounds, acids or Lewis acids.
Homopolymers of this type are branched polymers generally
comprising primary, secondary and tertiary amino groups in a ratio
of about 30%:40%:30%. This distribution of amino groups is
generally determinable via 13C NMR spectroscopy. The distribution
is preferably in the range from 1:0.8:0.5 to 1:1.3:0.8.
[0399] Comonomers used are preferably compounds having at least two
amino functions. Useful comonomers include for example
alkylenediamines having 2 to 10 carbon atoms in the alkylene
moiety, in which case ethylenediamine and propylenediamine are
preferred. Useful comonomers further include triamines such as
diethylenetriamine, triethylenetetramine, tetraethylenepentamine,
dipropylenetriamine, tripropylene-tetramine,
dihexamethylenetriamine, aminopropylethylenediamine and
bisamino-propylethylenediamine.
[0400] Useful polyethyleneimines further include crosslinked
polyethyleneimines, which are obtainable by reaction of
polyethyleneimines with bi- or polyfunctional crosslinkers having
at least one halohydrin, glycidyl, aziridine or isocyanate unit, or
at least one halogen atom, as functional group. Examples of such
crosslinkers are epichlorohydrin or bischlorohydrin ethers of
polyalkylene glycols having 2 to 100 ethylene oxide and/or
propylene oxide units.
[0401] Polyethyleneimines can further include amidated polymers
typically obtainable by reaction of polyethyleneimines with
carboxylic acids, carboxylic esters, carboxylic anhydrides,
carboxamides or carbonyl halides; and/or alkoxylated
polyethyleneimines obtainable for example by reaction of
polyethyleneimines with ethylene oxide and/or propylene oxide;
and/or hydroxyl-containing polyethyleneimines and amphoteric
polyethyleneimines and/or lipophilic polyethyleneimines, generally
obtained by incorporating long-chain hydrocarbon moieties in the
polymer chain.
[0402] Suitable polyethyleneimines are available under the
Lupasol.RTM. brand (from BASF SE, Ludwigshafen) for example.
[0403] Such agents can further affect a property of the building
material as described herein. Inclusion of these agents in one of
the first and second compositions and controlling the ratio of the
compositions at the voxel level can therefore result in objects
having different properties at different voxel blocks, as described
herein.
[0404] Any of the first and second compositions as described herein
can further comprise one or more agents which are chemically
non-reactive with the curable materials forming the building (e.g.,
modeling) material.
[0405] Such agents include, for example, toughening agent, surface
active agents, stabilizers, antioxidants, pigments, dyes, and/or
dispersants.
[0406] A surface-active agent may be used to reduce the surface
tension of the formulation to the value required for jetting or for
printing process, which is typically around 30 dyne/cm.
[0407] Suitable stabilizers (stabilizing agents) include, for
example, thermal stabilizers, which stabilize the formulation at
high temperatures.
[0408] The pigment may be a white pigment. The pigment may be an
organic pigment or an inorganic pigment, or a metal pigment or a
combination thereof.
[0409] Combinations of white pigments and dyes are usable for
preparing colored cured materials.
[0410] The dye may be any of a broad class of solvent soluble dyes.
Some non-limiting examples are azo dyes which are yellow, orange,
brown and red; anthraquinone and triarylmethane dyes which are
green and blue; and azine dye which is black.
[0411] Such agents can further affect a property of the building
material as described herein. Inclusion of these agents in one of
the first and second compositions and controlling the ratio of the
compositions at the voxel level can therefore result in objects
having different properties at different voxel blocks, as described
herein.
[0412] In some of any of the embodiments described herein, one or
more of the first and second compositions further comprises a
toughening agent.
[0413] Non-limiting examples of toughening agents include
elastomeric materials. Representative examples include, without
limitation, natural rubber, butyl rubber, polyisoprene,
polybutadiene, polyisobutylene, ethylene-propylene copolymer,
styrene-butadiene-styrene triblock rubber, random styrene-butadiene
rubber, styrene-isoprene-styrene triblock rubber,
styrene-ethylene/butylene-styrene copolymer,
styrene-ethylene/propylene-styrene copolymer,
ethylene-propylene-diene terpolymers, ethylene-vinyl acetate and
nitrile rubbers. Preferred agents are elastomers such as
polybutadienes. Toughening agents such as elastomeric materials can
be added by incorporating in one or more of the compositions an
elastomeric material in a dispersed/dissolved phase.
[0414] In some of any of the embodiments described herein, one or
more of the first and second compositions further comprises an
impact modifying agent.
[0415] Exemplary such agents include impact modifying agents usable
in the formation of polyamine (e.g., Nylon6) materials, as
described herein.
[0416] Other impact modifying agents, such as, for example, carbon
fibers, carbon nanotubes, glass fibers, aramid Keylar,
polyparaphenylene benzobisoxazole Zylon, and other polar and non
polar impact modifiers, are also contemplated.
[0417] Such agents can further affect a property of the building
material as described herein. Inclusion of these agents in one of
the first and second compositions and controlling the ratio of the
compositions at the voxel level can therefore result in objects
having different properties at different voxel blocks, as described
herein.
[0418] The Printed Object:
[0419] According to an aspect of some embodiments of the present
invention there is provided a printed object, obtained by a method
as described herein in any of the respective embodiments and any
combination thereof.
[0420] When the building material is a modeling material, as
defined herein, the printed object is characterized by at least one
portion in which one voxel block exhibits a certain property or
sets of properties, and another voxel block exhibits a different
property or sets of properties. In some embodiments, the different
property is a different degree of the same property or set of
properties, for example, different impact resistance, different
HDT, different stiffness, different elasticity, different chemical
reactivity, etc.
[0421] In exemplary embodiments, a printed object, or a portion
thereof, comprises a polyamide material, as described herein, and
in some embodiments, different voxels or voxel blocks of the
polyamide material exhibits different properties, for example,
different impact resistance, different elasticity, etc.
[0422] The Systems:
[0423] FIG. 4 is a schematic illustration of a three-dimensional
printing system 40, according to some embodiments of the present
invention. System 40 comprises a three-dimensional printing
apparatus 44 having a printing block 41 which comprises a plurality
of printing heads. Printing block 41 is typically placed within an
enclosure 76 forming a printing chamber therein. Each head
preferably comprises an array of one or more nozzles (not shown),
through which a composition is dispensed. The composition is
generally shown at 74, but it is to be understood that more than
one composition is employed as further detailed hereinabove. In
various exemplary embodiments of the invention each head dispenses
one of the compositions. If desired, two or more heads can dispense
the same composition.
[0424] Each printing head is fed via a material reservoir which may
optionally include a temperature control unit (e.g., a temperature
sensor and/or a heating device), and a material level sensor. To
dispense the composition, a voltage signal is applied to the
printing heads to selectively deposit droplets of the respective
composition via the printing head nozzles, for example, as in
piezoelectric inkjet printing technology. The printing rate of each
head depends on the number of nozzles, the type of nozzles and the
applied voltage signal rate (frequency). Such printing heads are
known to those skilled in the art of solid freeform
fabrication.
[0425] In the example of FIG. 4, four printing heads 41a, 41b, 41c
and 41d are illustrated. Each of heads 41a, 41b, 41c and 41d has a
nozzle array. Heads 41a and 41b can be designated for the first and
second compositions, as further detailed hereinabove, and heads 41c
and 41d can be designated for a support material. Thus, head 41a
can deposit the first composition, head 41b can deposit the second
composition and heads 41c and 41d can both deposit a support
material. Alternatively, heads 41c and 41d, can be combined in a
single head having more nozzles than each of heads 41a and 41b. The
heads and nozzles are preferably made of materials selected capable
to withstand passage of heated compositions therethrough. In
various exemplary embodiments of the invention the heads are
configured for heating the materials contained therein.
[0426] Apparatus 44 can further comprise a curing system which can
comprise one or more radiation sources 48, which can be, for
example, an ultraviolet or visible or infrared or Xenon lamp, or
other sources of electromagnetic radiation, or electron beam
source, or ultrasound radiation source or microwave radiation
source, depending on the materials being used. Radiation source 48
serves for curing or solidifying the materials, following their
deposition. When the curing or solidifying is thermal, the
components of the system may be exposed to elevated temperatures.
Thus, the components of system 40 (particularly the printing heads,
but also any other component) are preferably made of materials that
sustain thermal curing temperatures. The present embodiments also
contemplate configuration in which two different radiation sources
apply different types of curing energies, as further detailed
hereinabove.
[0427] The printing heads and radiation source or sources can be
mounted in a frame or block 68 which is preferably operative to
reciprocally move over a tray 60, which serves as the working
surface. The radiation sources can be mounted in the block such
that they follow in the wake of the printing heads to at least
partially cure or solidify the materials just deposited by the
printing heads. According to the common conventions, tray 60 is
positioned in the X-Y plane. Tray 60 is typically configured to
move vertically (along the Z direction), e.g., downward. Apparatus
44 can further comprise one or more leveling devices 62, e.g., a
roller 64. Leveling device 62 serves to straighten, level and/or
establish a thickness of the newly formed layer prior to the
formation of the successive layer thereon. Leveling device 62 can
comprise a waste collection device 66 for collecting the excess
material generated during leveling. Waste collection device 66 may
comprise any mechanism that delivers the material to a waste tank
or waste cartridge. In various exemplary embodiments of the
invention waste collection device 66 is constituted to handle
reactive mixtures. This can be done in more than one way. In some
embodiments, the compositions react within waste collection device
66 after they are removed from the deposited layer. In these
embodiments, waste collection device 66 comprises a grinding device
67 that mechanically breaks the reaction product of the
compositions into sufficiently small debris to allow them to be
removed easily. Grinding device 67 can be in the form of a rotating
blade, a shaker, an ultrasound source or the like. In some
embodiments of the present invention waste collection device 66 is
maintained at a reduced temperature such as to reduce the reaction
rate, thereby allowing the compositions to be removed before the
reaction is completed. This can be achieved, for example, using a
heat pump 65 mounted on device 66.
[0428] System 40 preferably comprises a heater 76 that maintains an
elevated temperature within the printing chamber enclosed by
enclosure 76. The temperature within the enclosure is above the
melting point of the dispensed compositions so as to maintain them
in liquid form, thereby allowing them to be dispensed from the
heads of block 41, yet sufficiently low so as to prevent the first
and second composition from spontaneously reacting or curing before
they are leveled by device 62 and to facilitate waste collection.
For example when caprolactam is employed, heater 78 heats the
printing chamber to a temperature of about 80.degree. C. In some
embodiments, leveling device 62 is heated, for example, by a heater
(not shown) mounted on or integrally formed in device 62. These
embodiments are particularly useful for compositions which tend to
solidify or partially solidify immediately after they are
dispensed. In these cases, a heated device 62 is advantageous since
it liquefies or further liquefies the just deposited compositions
thereby facilitating easier straightening and waste removal.
[0429] System 40 may also comprises a gas inlet 82 port, mounted on
enclosure 76 and constituted to allow entry of gas, such as an
inert gas or inert gas mixture as further detailed hereinabove,
into the printing chamber. The gas can be provided to inlet 82
through a gas supply conduit 84 connected to a gas supply system
80, both of which can optionally and preferably also be part of
system 40. In some embodiments, gas supply system 80 heats the gas
prior to the delivery of the gas to inlet 82 port. Alternatively or
additionally, a gas heater 86 can be placed in proximity to inlet
port 82, so as to heat the gas upon entry into the printing
chamber. Preferably the gas is heated to the same temperature that
is maintained by heater 78.
[0430] Optionally, the printing chamber 76 is also formed with a
gas outlet 368 for allowing the gas to exit the chamber if desired.
Both inlet 82 and outlet 368 are of the present embodiments
provided with valves (not shown) so as to controllably allow entry
and/or exit of the gas to and from the chamber. Preferably,
controller 52 generates, continuously or intermittently, inflow and
outflow of the inert gas through the gas inlet and the gas outlet.
This can be achieved by configuring controller 52 to control at
least one of supply 80, inlet 82 and outlet 368. Optionally, system
40 comprises a gas flow generating device 370, placed within the
chamber 76 and configured for generating a flow of the inert gas
within the chamber. Device 370 can be a fan or a blower. Controller
52 can be configured for controlling also device 370, for example,
based on a predetermined printing protocol.
[0431] In some embodiments of the present invention apparatus 44
comprises a mixing chamber 362 for preparing the modeling material
formulation prior to entry of the modeling material formulation
into a respective head. In the schematic illustration of FIG. 4,
which is not to be considered as limiting, chamber 362 receives
materials from different containers, mixes the received materials
and introduces the mix to two heads (heads 41c and 41d, in the
present example). However, this need not necessarily be the case
since in some embodiments chamber 362 can receive materials from
different containers, mixes the received materials and introduces
the mix only to more than two heads of only to one head.
Preferably, the position and fluid communication between mixing
chamber 362 and respective head is selected such that at least 80%
or at least 85% or at least 90% or at least 95% or at least 99% or
the modeling material formulation that enters the respective head
or heads (e.g., heads 41c and 41d in the present example) remains
uncured. For example, chamber 362 can be attached directly to the
printing head or the printing block, such that motion of the
printing head is accompanied by motion of the mixing chamber. These
embodiments are particularly useful when the formulation undergoes
fast polymerization reaction even in the absence of curing
radiation.
[0432] In operation, the printing heads of printing block 41 move
in a scanning direction, which is referred to herein as the X
direction, and selectively deposit material in a predetermined
configuration in the course of their passage over tray 60. The
material typically comprises two or more compositions as further
detailed hereinabove and one or more types of support material. The
passage of the printing heads of printing block 41 is followed by
the curing of the deposited material(s) by radiation source 48. In
the reverse passage of the heads, back to their starting point for
the layer just deposited, an additional deposition of material(s)
may be carried out, according to a predetermined configuration. In
the forward and/or reverse passages of the printing heads, the
layer thus formed may be straightened by leveling device 62, which
can follow in the path of the printing heads in their forward
and/or reverse movement. Once the printing heads return to their
starting point along the X direction, they may move to another
position along an indexing direction, referred to herein as the Y
direction, and continue to build the same layer by reciprocal
movement along the X direction. Alternately, the printing heads may
move in the Y direction between forward and reverse movements or
after more than one forward-reverse movement. The series of scans
performed by the printing heads to complete a single layer is
referred to herein as a single scan cycle.
[0433] Once the layer is completed, tray 60 is lowered in the Z
direction to a predetermined Z level, according to the desired
thickness of the layer subsequently to be printed. The procedure is
repeated to form three-dimensional object 42 in a layerwise
manner.
[0434] Tray 60 can alternatively or additionally be displaced in
the Z direction between forward and reverse passages of the
printing head of printing block 41, within the layer. Such Z
displacement may be carried out for example in order to cause
contact of the leveling device with the surface in one direction
and prevent contact in the other direction.
[0435] System 40 also comprises a material supply apparatus 50
which comprises the material containers or cartridges and supplies
a plurality of materials to fabrication apparatus 44, via a
respective plurality of supply ducts 58. In the illustration of
FIG. 4, four supply containers 56a, 56b, 56c and 56d, and four
supply ducts 58a, 58b, 58c and 58d are shown, for providing
materials to heads 41a, 41b, 41c and 41d, respectively.
[0436] A controller 52 includes an electronic circuit that controls
fabrication apparatus 44 and supply apparatus 50. The electronic
circuit of controller 52 can communicate with a computer or data
processor 54 which transmits digital data pertaining to fabrication
instructions based on computer object data stored on a computer
readable medium, preferably a non-transitory medium, in a form of a
Standard Tessellation Language (STL) format or any other format
such as, but not limited to, at the aforementioned formats.
Typically, the circuit of controller 52 controls the voltage
applied to each printing head or nozzle array and the temperature
of the material in the respective printing head.
[0437] Once the manufacturing data is loaded to controller 52 it
can operate without user intervention. Controller 52 may, however,
receive additional input from the operator, e.g., using data
processor 54 or using a user interface 46 communicating with unit
52. User interface 46 can be of any type known in the art, such as,
but not limited to, a keyboard, a touch screen and the like. For
example, controller 52 can receive, as additional input, one or
more material types and/or attributes, such as, but not limited to,
color, characteristic distortion and/or transition temperature,
viscosity, electrical property, magnetic property. Other attributes
and groups of attributes are also contemplated. Controller 52 can
also receive a ratio between the first composition and the second
composition, as further detailed hereinabove. The ratio can be
received via user interface 46 or data processor 54. Data processor
can also calculated the ratio based on the desired properties of
object 42 and then transmit the ratio to controller 52. In some
embodiments of the present invention radiation source(s) 48 are
also controlled by controller 52. For example, controller 52 can
activate and deactivate radiation source(s) 48 according to a
predetermined printing protocol. When system 40 comprises two
different radiation sources that apply different types of curing
energies, controller 52 preferably controls each of these radiation
sources separately. For example, controller 52 can signal a first
radiation source to deliver a first type of curing energy (e.g., in
the form of UV radiation), and a second radiation source to deliver
a second type of curing energy (e.g., thermal energy), such that
the two types of curing energies are delivered according to a
predetermined curing scenario sequentially, simultaneously or
intermittently. In any of these curing scenarios, controller 52 can
also signal the radiation source(s) to deliver the energy
repeatedly.
[0438] System 40 can fabricate an object by depositing different
materials from different printing heads. In various exemplary
embodiments of the invention the electronic circuit of controller
52 is configured to form voxel blocks, wherein, for each block, a
ratio between a number of voxels of the first composition in the
block and a number of voxels of the second composition in the block
corresponds to the selected ratio received from data processor 54
or user interface 46.
[0439] The system of present embodiments provides the ability to
select materials from a given number of materials and define
desired combinations of the selected materials and their
properties. The spatial locations of the deposition of each
material with the layer are defined, either to effect occupation of
different three-dimensional spatial locations by different
materials, or to effect occupation of substantially the same
three-dimensional location or adjacent three-dimensional locations
by two or more different materials so as to allow post-deposition
spatial combination of the materials within the layer.
[0440] As used herein the term "about" refers to .+-.10%.
[0441] The terms "comprises", "comprising", "includes",
"including", "having" and their conjugates mean "including but not
limited to".
[0442] The term "consisting of means "including and limited
to".
[0443] The term "consisting essentially of" means that the
composition, method or structure may include additional
ingredients, steps and/or parts, but only if the additional
ingredients, steps and/or parts do not materially alter the basic
and novel characteristics of the claimed composition, method or
structure.
[0444] As used herein, the singular form "a", "an" and "the"
include plural references unless the context clearly dictates
otherwise. For example, the term "a compound" or "at least one
compound" may include a plurality of compounds, including mixtures
thereof.
[0445] Throughout this application, various embodiments of this
invention may be presented in a range format. It should be
understood that the description in range format is merely for
convenience and brevity and should not be construed as an
inflexible limitation on the scope of the invention. Accordingly,
the description of a range should be considered to have
specifically disclosed all the possible subranges as well as
individual numerical values within that range. For example,
description of a range such as from 1 to 6 should be considered to
have specifically disclosed subranges such as from 1 to 3, from 1
to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as
well as individual numbers within that range, for example, 1, 2, 3,
4, 5, and 6. This applies regardless of the breadth of the
range.
[0446] Whenever a numerical range is indicated herein, it is meant
to include any cited numeral (fractional or integral) within the
indicated range. The phrases "ranging/ranges between" a first
indicate number and a second indicate number and "ranging/ranges
from" a first indicate number "to" a second indicate number are
used herein interchangeably and are meant to include the first and
second indicated numbers and all the fractional and integral
numerals therebetween.
[0447] As used herein the term "method" refers to manners, means,
techniques and procedures for accomplishing a given task including,
but not limited to, those manners, means, techniques and procedures
either known to, or readily developed from known manners, means,
techniques and procedures by practitioners of the chemical,
pharmacological, biological, biochemical and medical arts.
[0448] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention, which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable subcombination
or as suitable in any other described embodiment of the invention.
Certain features described in the context of various embodiments
are not to be considered essential features of those embodiments,
unless the embodiment is inoperative without those elements.
[0449] Various embodiments and aspects of the present invention as
delineated hereinabove and as claimed in the claims section below
find experimental support in the following examples.
EXAMPLES
[0450] Reference is now made to the following examples, which
together with the above descriptions illustrate some embodiments of
the invention in a non limiting fashion.
Example 1
Polyamide-Forming Materials
[0451] Materials:
[0452] A caprolactam monomer and a catalyst for anionic ring
opening polymerization (ROP), were obtained from Bruggerman, in
accordance with a monomer and a catalyst used for preparing
NYRIM.RTM. products.
[0453] The monomer and catalysts were mixed to form composition A
(an exemplary first composition according to some embodiments of
the present invention).
[0454] A caprolactam activator used for preparing NYRIM.RTM.
products, was also obtained from Bruggerman. The caprolactam
activator is 1,3-Benzenedicarbonyl dichloride, polymer with
2-methyloxirane polymer with oxirane ether with 1,2,3-propanetriol
(3:1), caprolactam-terminated; otherwise referred to as
Polyoxypropylene-polyoxyethylene-block copolymer isophthalic acid
biscaprolactam ester; CAS No. 718612-97-6;
C.sub.20H.sub.24N.sub.2O.sub.4[C.sub.3H.sub.8O.sub.33(C.sub.3H.sub.6OC.su-
b.2H.sub.4O).sub.x], the chemical structure of which is shown
below:
##STR00011##
wherein R is:
##STR00012##
wherein k is approx. 23 and j is approx. 5.
[0455] The polymer has Mn of 10,485 Da; and Mw of 27,143 Da.
[0456] The caprolactam activator forms an exemplary Composition B
according to some embodiments of the present invention.
[0457] Methods:
[0458] Composition A was jetted by inkjet head A or a set of inkjet
heads A and Composition B by inkjet head B or a set of inkjet head
B.
[0459] The inkjet temperature was between 80-110.degree. C., to
make sure the caprolactam is liquid and the activator viscosity is
suitable.
[0460] The compositions were jetted on a heated tray,
simultaneously, and were subsequently heated by an IR or Halogen
lamp, at a temperature above 110.degree. C., so as to effect a
polymerization.
[0461] The ratio between the jetted materials was digitally
predetermined, controlling the amount (weight) jetted from every
head. Optionally, drop sizes can be controlled to achieve a
selected weight between compositions A and B, while considering
viscosity and/or density of the compositions.
Results: Table 2 below presents the obtained data.
TABLE-US-00002 TABLE 2 Level of chemical Jet A Jet B ratio control
Properties Caprolactam + Activator 5:1 6 voxels Similar to catalyst
Nyrim .RTM. 2000* Caprolactam + Activator 7:3 10 voxels Similar to
catalyst Nyrim .RTM. 3000 Caprolactam + Activator 6:4 5 voxels
Similar to catalyst Nyrim .RTM. 4000* *See, Table 1
Example 2
Polyamide-Forming Materials
[0462] Materials:
[0463] Table 3 below presents materials usable for forming
polyamide materials while using a method as described herein.
TABLE-US-00003 TABLE 3 Trade name/Chemical Compound Function
Composition Source .epsilon.-CL Curable AP-NYLON .RTM. Caprolactam
Bruggemann monomer KG .epsilon.-CLE Curable .epsilon.-Caprolactone;
Capa .TM. Perstorp monomer/ Monomer Impact modifier C10 Curable
BRUGGOLEN .RTM. C10 Bruggemann Monomer + (about 17-18% of NaCL in
KG catalyst .epsilon.-CL) C20 Curable Bruggolen .RTM. C20P
Bruggemann Monomer + (about 80% of .epsilon.-CL blocked KG
activator HDI in .epsilon.-CL) BruggolenTP Activator Bruggolen TP
C-1312 Bruggemann C-1312 (PPG/PEG based high KG molecular weight
.epsilon.-CL blocked isocyanate macroactivator) LL Curable
Laurolactam Sigma- monomer (12-Aminododecanolactam, Aldrich 98%)
PDL Curable .omega.-Pentadecalactone, .gtoreq.98% Sigma- monomer
Aldrich PEI FG Impact Lupasol .RTM. FG BASF modifier/
(polyethyleneimine, about amine 800 g/mol, 99%) booster PEI PR8515
Impact Lupasol .RTM. PR8515 BASF modifier/ (polyethyleneimine,
about amine 2000 g/mol, 99%) booster PEI WF Impact Lupasol .RTM. WF
BASF modifier/ (polyethyleneimine, about amine 25000 g/mol, 99%)
booster N3900 Activator Desmodur N 3900 Bayer (asymmetric
isocyanurate trimer of hexamethylene diisocyanate) BL-N3900
activator .epsilon.-Caprolactam blocked Synthetically Desmodur N
3900 prepared by the present inventors* IDA Impact Baxxodur .RTM.
EC 201 BASF modifier/ (Isophorone diamine) amine booster T-403
Impact Baxxodur .RTM. EC 310 BASF modifier/ (Trifunctional
polyether amine amine, M.sub.w about 440 g/mol) booster C540 Impact
Bruggolen .RTM. C540 Bruggemann modifier/ (Trifunctional polyether
KG amine amine, M.sub.w about 5000 g/mol) booster *see below
general synthesis procedure
[0464] Preparation of .epsilon.-Caprolactam Blocked Desmodur N3900
(BL-N3900):
[0465] The subject modified activator is generally prepared as
follows:
[0466] 50 grams of AP-NYLON.RTM. Caprolactam (Bruggemann Chemie)
and 50 grams of Desmodur N 3900 (Bayer AG) are added into a glass
bottle containing a magnetic stirrer. The bottle is tightly sealed
and the mixture is subjected to vigorous magnetic stirring and
heated to 85-95.degree. C. for 6 hours. Completion of the block
reaction can be determined by viscosity measurements, wherein no
further change in viscosity is indicative of reaction
completion.
[0467] The reaction product is a highly viscous liquid, which does
not crystallize at room temperature.
[0468] Methods:
[0469] All experiments are performed using two-part model
formulation systems, comprising a set of polyamide-forming
materials divided into two formulations. Generally, the Model A
formulation in the formulation system (the first composition)
comprises at least one caprolactam monomer, and a catalyst, and may
further comprise one or more impact modifier(s) and/or amine
boosters, and/or one or more additional thermally-curable monomers
(e.g., a laurolactam or a caprolactone). Model B formulation (the
second composition) in the formulation system comprises an
activator and may further comprise one or more impact modifier(s)
and/or amine booster(s), and/or one or more additional
thermally-curable monomers (e.g., a caprolactone).
[0470] Herein, the term "amine booster" refers to an
amine-containing compound which increases the polymerization rate,
as described herein, presumably by activating the activator. Some
amine boosters are also known and referred to in the art as Impact
modifiers.
[0471] Molds: Mold experiments are conducted by mixing Model A
formulation (the first composition) and Model B formulation (the
second composition) at the indicated weight ratio in, for example,
a mold having a thickness of 3.2 mm, a length of 127 mm, and a
width of 12.7 mm. The total weight ratio of Model A and Model B
formulations is about 100 grams. Mold experiments are indicative of
an effect of different ratios of the first and second compositions
(formulations), and are used to predict as effect of a selected
ratio of the compositions on a property of the building (e.g.,
modeling) material.
[0472] 3D Inkjet printing: Three-dimensional inkjet printing of
polyamide-producing formulations is performed using Connex.RTM. 500
system by dual jetting: Model formulation A (Model A; the first
composition) was jetted by inkjet head A (or a series of inkjet
heads A) and Model formulation B (Model B; the second composition)
was jetted by inkjet head B (or a series of inkjet heads B).
[0473] The inkjet temperature is 65-110.degree. C., typically
70-90.degree. C. Jetting at this temperature range is suitable for
having the caprolactam-containing and/or activator-containing
formulations being in a liquid form and featuring the required
viscosity.
[0474] The materials are jetted on a heated tray, simultaneously,
and are subsequently heated by an IR or Halogen lamp or ceramic
lamp, at a temperature above 110.degree. C. (e.g., above
400.degree. C.), so as to effect a polymerization.
[0475] Mechanical Properties:
[0476] HDT is measured using HDT 3 VICAT (CEAST, Italy).
[0477] Izod Impact is measured by RESIL 5.5J (CEAST, Italy).
[0478] DMA measurements indicate the temperature at which storage
modulus decreases by 50%. This value is indicative of the stiffness
degree of the material. Decrease of storage modulus at a high
temperature indicates a stiff material and at a low temperature it
indicates weak material.
[0479] DMA measurements are performed using DMA Q800 measurement
device (TA Instruments (Belgium))
[0480] Exemplary Formulations:
[0481] Table 4A below presents exemplary Model A formulations (the
first composition) and Table 4B below presents exemplary Model B
formulations (the second composition).
TABLE-US-00004 TABLE 4A (Model A) Com- ponent (a) (b) (c) (d) (e)
(f) (g) (h) (i) (j) (k) C10 7.5 50 50 50 50 50 50 50 25 25 25
.epsilon.-CL 92.5 50 45 45 45 45 45 45 72.5 72.5 62.5 LL 10 IDA 5
T-403 5 C540 5 PEI FG 5 2.5 2.5 2.5 PEI PR 5 8515 PEI WF 5
TABLE-US-00005 TABLE 4B (Model B) Component (a) (b) (c) (d) (e) (f)
(g) (h) (i) (j) (k) C20 5.2 34.7 34.7 34.7 34.7 34.7 34.7 34.7
.epsilon.-CL 92.5 65.3 65.3 65.3 65.3 65.3 65.3 65.3 30 30 30
.epsilon.-CLE 50 50 PDL 50 BL-N3900 20 20 20
[0482] The ratio between the jetted materials is digitally
predetermined, controlling the amount (weight) jetted from every
head. Optionally, drop sizes can be controlled to achieve a
selected weight ratio between compositions A and B, while
considering viscosity and/or density of the compositions.
[0483] Table 5 below presents an additional set of exemplary
compositions, in which Model A formulations (the first
compositions) containing caprolactam, catalyst, and optionally one
or more amine compound(s) which increase the polymerization rate
(amine booster(s)), and Model B formulations (the second
compositions) containing non-blocked polyisocyanate-based activator
and optionally caprolactone, were tested at various weight ratios.
Table 5 below further presents the mechanical properties of the
cured modeling materials obtained in the experiments conducted with
formulations I-VI in molds, showing the effect of the weight ratio
of Model A and Model B formulations (exemplary first and second
compositions, respectively) of the mechanical properties of he
obtained modeling material.
TABLE-US-00006 TABLE 5 A/B Izod Model A Model B weight HDT,
.degree. C. Notched No. C10 .epsilon.-CL IDA T-403 C540 N3900
.epsilon.-CLE ratio (0.45 MPa) (J/m) I 31 69 100 80/20 155 60 II 31
64 5 100 80/20 153 65 III 31 64 5 100 80/20 155 60 IV 31 64 5 100
80/20 155 140 V 31 64 5 45 55 70/30 155 54 VI 31 59 5 5 27.5 72.5
60/40 75.8 850
[0484] In an additional set of experiments, the effect of various
A:B ratios of selected first and second compositions on the
mechanical properties of the obtained cured polyamide material was
tested. The obtained data is presented in Tables 6A-6C.
TABLE-US-00007 TABLE 6A (A/B = 50:50 wt. %) Jet A Jet B C10
.epsilon.-CL PEI FG BL-N3900 .epsilon.-CL .epsilon.-CLE HDT Izod,
notched DMA 25% 72.5% 2.5% 20% 30% 50% 153.degree. C. 210 J/m
59.degree. C.
TABLE-US-00008 TABLE 6B (A/B = 70:30 wt. %) DMA Jet A Jet B Izod,
(Tan C10 .epsilon.-CL PEI FG BL-N3900 .epsilon.-CL .epsilon.-CLE
HDT notched DMA* Delta, Tg) 25% 72.5% 2.5% 20% 30% 50% 155.degree.
C. 25 J/m 74.degree. C. 80.degree. C.
TABLE-US-00009 TABLE 6C (A/B = 40:60 wt. %) Jet A PEI Jet B Izod,
C10 .epsilon.-CL FG BL-N3900 .epsilon.-CL .epsilon.-CLE HDT notched
25% 72.5% 2.5% 20% 30% 50% 48.7.degree. C. 390 J/m
[0485] The obtain data demonstrate that HDT, Impact resistance and
stiffness of the cured material can be controlled by selecting the
A:B weight ratio. At higher amount of part B, a cured material with
high Impact is achieved. At higher amount of part A, a cured
material with higher stiffness is achieved.
[0486] The compositions presented in Tables 4A, 4B, 5 and 6A-6C are
to be regarded as representative, non-limiting, examples. The
weight percents of each component in the compositions are not to be
regarded as limiting and can be manipulated as desired.
Alternatively, or in addition, the indicated components can be
replaced by other components featuring the same function, and are
not to be regarded as limiting in any way. Further alternatively,
or in addition, the weight ratio between the compositions can be
manipulated as desired.
[0487] By digitally controlling the A:B ratio modeling materials
featuring variable properties at the voxel block level can be
obtained.
Example 3
Exemplary Process
[0488] Post-process treatment:
[0489] The present inventors have uncovered that following a 3D
inkjet printing process of polyamide-forming compositions, the
obtained cured material is not fully polymerized, and typically
exhibits a relatively low HDT of about 40-50.degree. C.
[0490] In order to achieve higher HDT values, thermal post process
is required in order to complete the polymerization and obtain
cured material featuring HDT of 150.degree. C.
[0491] For example, the present inventors have successfully
practiced a thermal post-process curing for 1 hour at 150.degree.
C.
[0492] In order to monitor polymerization completion, weight loss
upon the post-process thermal treatment was measured. Weight of the
cured material was measured prior to and following thermal post
process.
[0493] A minimum weight loss during post-process (e.g., of about
1.5-2.5% by weight), is indicative of a successful printing and of
obtaining a printed object with mechanical properties identical to
those polymerized in molds.
[0494] Printing Data Selection:
[0495] In exemplary embodiments of the 3D inkjet printing processes
described herein, Model A and Model B formulations (a first and a
second composition, respectively) are jetted at various weight
ratios, which can be realized as described herein
[0496] Such a process can be performed in more than one way.
[0497] In some embodiments of the present invention a "Drop on
Drop" printing protocol is employed, as described herein.
[0498] In some embodiments of the present invention a "side by
side" printing protocol is employed, as described herein.
[0499] The weight loss of the cured object obtained upon 3D inkjet
printing of formulation (c) in Tables 4A and 4B, using the "Drop on
Drop" pattern and the "side by side" pattern was measured.
[0500] The obtained data suggested that selecting a Drop-on-Drop
printing mode in which combining the two formulations occurs within
each pixel, layer by layer, and distribution of the two composition
within each layer is homogeneous/isotropic, is superior to the
"side by side" printing protocol.
[0501] Thus, when printing data is selected such that different
ratios of the first and second compositions are selected at each
voxel level, as described herein, a printed object with
controllable mechanical properties at the voxel level is
provided.
Example 4
Exemplary System
[0502] The compositions of the present embodiments can be
deposited, for example, using a system marketed as Objet Connex.TM.
(Stratasys Ltd., Israel). Thermal curing conditions can be
achieved, for example, using a ceramic lamp providing temperature
of from about 400.degree. C. to about 900.degree. C., and
wavelength of from about 2.4 .mu.m to about 4.3 .mu.m. Additionally
or alternatively, the printing tray 60 can be heated to a
temperature of from about 50.degree. C. to about 180.degree. C.,
and the printing chamber can be heated to a temperature of from
about 50.degree. C. to about 90.degree. C.
[0503] In some embodiments of the present invention the printing
system is sealed and is optionally and preferably equipped with one
or more filters. These embodiments are useful for keeping the
printing environment generally dry and inert. These embodiments are
also useful for reducing or preventing entry of moisture into the
system. Moisture can also be reduced alternatively or additionally
using by means of a gas, such as an inert gas or inert gas mixture,
that fills the chamber as further detailed hereinabove. Use of a
drying filter is also contemplated. For example, the gas forming
the printing environment within the printing chamber can be
circulated through the drying filter.
[0504] In some embodiments of the present invention the printing
block is thermally isolated from the printing chamber. These
embodiments are particularly useful when it is desired to employ
jetting at different temperatures.
Example 5
Co-Polymerizable Compositions Containing an Epoxy Curable Material
and a Caprolactone Curable Material
[0505] Materials and Methods:
[0506] A cycloaliphatic epoxy,
3,4-Epoxycyclohexyl-methyl-3,4-epoxycyclohexane carboxylate
(UVACURE.RTM.1500 by CYTEC) was used as a curable monomer which is
polymerizable via cationic polymerization, in the presence of an
initiator. Commonly used initiators are photoinitiators. The
UV-activated photoinitiator Uvacure.RTM.6976 was used.
.epsilon.-Caprolactone (CAPA) was used as a thermally-curable
monomer, which can be polymerized in the presence of the same
photoinitiator.
[0507] Composition A is the epoxy+photoinitiator, and composition B
is Caprolactone. .epsilon.-Caprolactone (CAPA) and the
photoinitiator were mixed to form the first composition,
composition A, and the epoxy curable material and the
photoinitiator were mixed to form the second composition,
composition B.
[0508] Composition A was jetted by inkjet head A or a set of inkjet
heads A and Composition B by inkjet head B or a set of inkjet head
B.
[0509] The inkjet heads temperature was between 50 and 80.degree.
C.
[0510] The compositions were jetted on a heated tray,
simultaneously, and were subsequently exposed to UV irradiation,
for 30 minutes, and then to thermal curing, as described herein,
for 12 hours, at 85.degree. C.
[0511] The ratio between the jetted materials was digitally
predetermined, controlling the amount (weight) jetted from every
head. Optionally, drop sizes can be controlled to achieve a
selected weight between compositions A and B, while considering
viscosity and/or density of the compositions.
[0512] Alternatively, for assessing the effect of the A:B
compositions ratio, compositions A and B were mixed in a mold and
the mechanical properties of the obtained polymeric films were
measured.
[0513] The data obtained for films obtained by 3D inkjet printing
of various composition ratios is presented in Table 7 below.
TABLE-US-00010 TABLE 7 Max Stress Max Strain CAPA EPOXY (MPa) (%)
Feel 100 0 wax 95 5 10.2 115 thermoplastic 90 10 0.33 50 rubber 67
33 1.7 29 rubber 50 50 20 12 hard 0 100 10 1 hard
[0514] These data suggest that the epoxy resin reacts as a
cross-linker of the polycaprolactone, whereby the latter acts as an
Impact modifier of the epoxy resin. These data indicate that the
properties of objects made by dual jetting these two polymeric
systems can be finely controlled at the voxel level, using the
methods described herein.
[0515] Although the invention has been described in conjunction
with specific embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims.
[0516] All publications, patents and patent applications mentioned
in this specification are herein incorporated in their entirety by
reference into the specification, to the same extent as if each
individual publication, patent or patent application was
specifically and individually indicated to be incorporated herein
by reference. In addition, citation or identification of any
reference in this application shall not be construed as an
admission that such reference is available as prior art to the
present invention. To the extent that section headings are used,
they should not be construed as necessarily limiting.
* * * * *