U.S. patent application number 17/285955 was filed with the patent office on 2021-12-09 for polymer reinforced materials for inkjet based 3d printing.
The applicant listed for this patent is Inkbit, LLC. Invention is credited to Gregory ELLSON, Wenshou WANG, Yan ZHANG.
Application Number | 20210380795 17/285955 |
Document ID | / |
Family ID | 1000005849768 |
Filed Date | 2021-12-09 |
United States Patent
Application |
20210380795 |
Kind Code |
A1 |
WANG; Wenshou ; et
al. |
December 9, 2021 |
POLYMER REINFORCED MATERIALS FOR INKJET BASED 3D PRINTING
Abstract
The present disclosure relates to reinforcing photopolymer
resins and uses thereof, e.g., in inkjet 3D printing.
Inventors: |
WANG; Wenshou; (Quincy,
MA) ; ZHANG; Yan; (Lowell, MA) ; ELLSON;
Gregory; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Inkbit, LLC |
Medford |
MA |
US |
|
|
Family ID: |
1000005849768 |
Appl. No.: |
17/285955 |
Filed: |
October 17, 2019 |
PCT Filed: |
October 17, 2019 |
PCT NO: |
PCT/US2019/056715 |
371 Date: |
April 16, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62746818 |
Oct 17, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 31/08 20130101;
B33Y 10/00 20141201; C08L 39/06 20130101; B29C 64/124 20170801;
B33Y 70/00 20141201; C08L 81/02 20130101; C08L 33/12 20130101 |
International
Class: |
C08L 31/08 20060101
C08L031/08; C08L 81/02 20060101 C08L081/02; B29C 64/124 20060101
B29C064/124; B33Y 70/00 20060101 B33Y070/00 |
Claims
1. A reinforced composition for 3-D ink printing, said reinforced
composition comprising: a UV-curable matrix material and a
reinforcing agent, wherein the reinforcing agent is at least
partially soluble in the UV-curable matrix material and wherein the
solubility of the reinforcing agent in the UV-curable matrix
material decreases as the UV-curable matrix material cures, whereby
curing the UV-curable matrix material causes the reinforcing agent
to form a phase-separate domain in the cured UV-curable matrix
material.
2. The reinforced composition of claim 1, wherein the UV-curable
matrix material comprises an acrylate.
3. The reinforced composition of claim 1, wherein the UV-curable
matrix material comprises a thiol-ene.
4. The reinforced composition of claim 1, wherein the UV-curable
matrix material comprises a combination of acrylate and
thiol-ene.
5. The reinforced composition of claim 1, wherein reinforcing agent
is selected based at least in part on a property of the UV-curable
matrix material.
6. The reinforced composition of claim 1, wherein the reinforcing
agent has a higher glass-transition temperature than that of the
UV-curable matrix material.
7. The reinforced composition of claim 1, wherein the reinforcing
agent is non-UV-curable.
8. The reinforced composition of claim 1, wherein the reinforcing
agent and UV-curable matrix material fail to react with each
other.
9. The reinforced composition of claim 1, wherein the cured
reinforced composition is 30-300% has a tensile strength that is
higher than that of the UV-curable matrix material in the absence
of the reinforcing agent.
10. The reinforced composition of claim 1, wherein the cured
reinforced composition has a tensile strength that depends upon
loading of the reinforcing agent within the reinforced
composition.
11. The reinforced composition of claim 1, wherein the reinforcing
agent is present in an amount that is less than 20 wt %.
12. The reinforced composition of claim 1, wherein the reinforcing
agent is a polyvinylpyrrolidone.
13. The reinforced composition of claim 1, wherein the reinforcing
agent is a poly(methyl methacrylate).
14. A method comprising jetting a layer of ink onto a structure
that is being printed and causing dissolved reinforcing agent to
precipitate after said layer of ink has been deposited.
15. The method of claim 14, wherein causing said dissolved
reinforcing agent to precipitate comprises curing said ink.
16. The method of claim 15, wherein curing said ink comprises
exposing said ink to UV.
17. The method of claim 15, wherein curing said ink comprises
exposing said ink to a temperature decrease.
Description
RELATED APPLICATIONS
[0001] The application claims the benefit of the Oct. 17, 2018
priority of U.S. Provisional Application 62/746,818, the contents
of which are herein incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention relates generally to 3D inkjet printing and
more specifically to the printing of reinforcing material in using
a 3D inkjet printer.
BACKGROUND OF THE INVENTION
[0003] Additive manufacturing allows objects to be fabricated via
selective addition of material. A typical additive manufacturing
process works by slicing a digital model (for example, represented
using an STL file) into layers. Data representing these layers is
then sent to a fabrication apparatus. The fabrication apparatus
then builds an object by depositing one layer at a time, starting
with a bottom layer and ending with a top layer. Additive
manufacturing is rapidly gaining popularity in a variety of markets
including automotive, aerospace, medical devices, pharmaceuticals,
and industrial tooling.
[0004] The growth of additive manufacturing processes has led to
the commercialization of various species of such processes. These
include extrusion processes, such as fused deposition modeling.RTM.
(FDM.RTM.) light polymerization processes, such as
stereolithography (SLA) and multijet/polyjet powder bed fusion
processes, such as selective laser sintering (SLS) or binder
jetting, and lamination processes, such as laminated object
manufacturing (LOM).
[0005] Nevertheless, despite its growth, additive manufacturing has
limitations. Among these limitations are the constraints in the
materials that can be used in conjunction with such processes. Only
limited types of materials can be used. The performance of these
materials limits the efficiency of the manufacturing process and
the quality of the manufactured object.
[0006] One example of an additive manufacturing process relies on
3D printing using an inkjet printer. In this example, printheads
build an object by depositing droplets of liquid ink. These
printheads are typically mounted on a gantry system to allow
deposition of ink in different locations of a build volume. A build
platform may also move with respect to the printheads, which may be
stationary. The liquid ink is then solidified, for example by using
UV or visible-light radiation.
[0007] Because of its high resolution, its high throughput, and its
ability to print multiple materials, an inkjet printers are
particularly useful for building prototypes. These printers
typically rely on low-viscosity acrylates. The resulting structures
are useful as prototypes but lack the durability and strength that
would be desired in an actual end product.
[0008] In some systems, multiple printheads build objects with
multiple base materials. For example, materials that have different
optical, mechanical, thermal, or electromagnetic properties can be
used. These materials can be combined to achieve composite
materials with a wide range of properties.
[0009] An inkjet printer that carries out additive manufacturing
typically has a subsystem for curing the ink. These subsystems
typically rely on UV curing.
[0010] In a UV-curing unit, UV radiation solidifies inks via
photo-initiation of a polymerization reaction. UV radiation can be
supplied by a variety of different mechanisms, such as arrays of
LEDs and mercury or xenon arc lamps. UV-curing is typically applied
after each printed layer or after depositing each material within a
layer. The UV-curing unit can be fixed with respect to the printer
or it can move independently with respect to the object.
[0011] Some inkjet printers that carry out additive manufacturing
combine both UV and thermal curing to manufacture an object.
[0012] Inks suitable for inkjet printing often conform to certain
specifications. Of particular importance are the ink's viscosity
and its surface tension. Suitable viscosities are in the range of
10-15 cps at operating conditions. Surface tension typically should
be between 20-45 mN/m.
[0013] An ink is preferably thermally stable. For example, it
should not solidify anywhere within the ink jet printer. In
particular, it should remain liquid within the printhead, the ink
container, and the feeding system.
[0014] It is also useful for the ink to have formulation stability.
In particular, the different components of the ink should not
separate for a reasonably long time.
[0015] Many inks include additives. These additives include
colorants, such as dyes or pigments or the mixture of pigments and
dyes. These colorants are dispersed or dissolved in the ink. Some
inks also include surfactants adjust the surface tension of the
ink. These surfactants promote jetting or printing performance
[0016] Since different inks have different properties, it is
necessary to optimize various parameters based on these different
properties. As one example, the process of inkjet printing requires
causing the printhead to eject the ink. This is carried out by
applying a waveform to the print head. The shape and duration of
this waveform depends on the nature of the ink to be ejected.
Therefore, it is important to optimize this waveform for different
ink formulations.
SUMMARY OF THE INVENTION
[0017] The invention provides ways to reinforce the materials used
in 3D inkjet printing.
[0018] Upon being cured, an ink becomes a polymer matrix. It is
possible to improve the strength of such a matrix by adding a
reinforcing filler material. Examples of suitable filler materials
include carbon black, silica, clay, glass fibers, and carbon
nanotubes. It is particularly useful to add filler materials at
high loading fractions, often 30-100 phr, in order to adequately
improve the strength of the cured polymer matrix.
[0019] Although adding a filler material provides reinforcement,
the high loading fraction of filler that is required to achieve
meaningful strengthening increases the resin viscosity. This can
push viscosity beyond what is acceptable for use as an ink in a 3D
printer.
[0020] The use of filler material also causes difficulty because
the ink must remain a homogenous liquid until it is cured. This
requires that the filler material disperse well and that it be
stable over long periods of time. This limits both the maximum
amount of filler and the type of filler material that is usable
with photopolymers.
[0021] Some 3D printing methods, particularly those that rely on
inkjet printing, have even stringent requirements that further
limit the ability to disperse filler. For example, an inkjet
printer may encounter difficulty if there exist particles in the
ink that exceed a maximum particle size.
[0022] One aspect of the invention is related to printing using an
ink that is initially liquid but that transforms, during curing,
into a 3D matrix material in which a constituent of the liquid ink
forms a second phase within the 3D printable matrix material. This
second phase adds strength and support to the 3D printable matrix
material. The result is therefore a reinforced matrix material that
provides additional strength and durability to objects that have
been built using a 3D inkjet printing process.
[0023] In one embodiment, the invention relates to a method of
reinforcing photopolymer resins for improved tensile strength while
maintaining the processability of matrix resins.
[0024] In another embodiment, the reinforcing agent is initially
soluble or partially soluble in the uncured matrix material resin
but undergoes a decrease in solubility when the uncured matrix
material resin is cured.
[0025] In yet another embodiment, the reinforcing agent initially
is soluble or partially soluble in the uncured matrix material
resin but undergoes a decrease in solubility when the uncured
matrix material resin undergoes a temperature change. This causes
the reinforcing material to precipitate from solution and to
separate into a different phase. This forms domains of rigid
material that serve to strengthen the polymer matrix.
[0026] In another aspect, the invention relates to a reinforced
composition for 3D ink printing comprising: a UV-curable matrix
material and a reinforcing agent that is at least partially soluble
in the UV-curable matrix material.
[0027] Embodiments include those in which the UV-curable matrix
material includes acrylates, thiol-enes, or combinations
thereof.
[0028] In other embodiments, the reinforcing agent is selected
based at least in part on one or more properties of the UV-curable
matrix material.
[0029] In yet other embodiments, the reinforcing agent has a higher
glass transition temperature than that of the UV-curable matrix
material.
[0030] Further embodiments include those in which the reinforcing
agent is non-UV-curable and those in which the reinforcing agent
does not react with the UV-curable matrix material.
[0031] Also among the embodiments are those in which the tensile
strength of the cured reinforced composition is 30-300% higher than
the UV-curable matrix material in the absence of any reinforcing
agent and those in which the tensile strength of the cured
reinforced composition depends at least in part upon the loading of
the reinforcing agent within the reinforced composition.
[0032] Further embodiments include those in which the content of
reinforcing agent is less than 20 wt % in the overall
formulation.
[0033] A variety of reinforcing agents can be used. These include,
as representative examples, polyvinylpyrrolidone and a poly(methyl
methacrylate).
DESCRIPTION OF A PREFERRED EMBODIMENT
[0034] A composition of the 3D printable material includes a
printable matrix material, which is curable, and a reinforcing
agent. The printable matrix material is typically a monomer that
polymerizes under UV irradiation. The printable matrix material is
generally, but not limited to, acrylates, thiol-enes or
combinations thereof.
[0035] The reinforcing agent is not UV-curable and is non-reactive
with the printable matrix material. The reinforcing agent is,
however, at least partially soluble in the printable matrix
material. The reinforcing agent and the printable matrix material
may be mixed as liquids, or the reinforcing agent may be dissolved
as a solid into the liquid printable matrix material to form a
solution. The reinforcing agent has a higher glass transition
temperature (Tg) than the printable matrix material. In one
embodiment, the reinforcing agent constitutes less than 20% of the
matrix material-reinforcing solution by weight.
[0036] Although the reinforcing agent is at least partially soluble
in the printable matrix material, as the printable matrix material
is cured under UV irradiation or otherwise undergoes a temperature
decrease, the reinforcing agent becomes less soluble and
precipitates out of solution forming another phase within the
printable matrix material. This phase forms reinforcing structures
within the curing matrix material.
[0037] The principle may be understood by considering the following
non-limiting examples.
EXAMPLE 1
Material: Acrylate Matrix Reinforced by a Vinylpyrrolidone
[0038] In this embodiment, IPUC101, an inventor-formulated
elastomeric acrylate material, is reinforced by
Polyvinylpyrrolidone (PVP) (Mw: 6000-150000). IPUC101 is a
self-formulated (see Table 1), elastomeric acrylate material with a
tensile strength of 3.4 MPa, elongation at break of 160%, and Shore
hardness of 35A. The reinforcing agent is Polyvinylpyrrolidone
(PVP) K15, purchased from Tokyo Chemical Industry Co. Ltd. The
reinforcing agent PVP is a polymer known for having high polarity.
Because this formulation of IPUC101 includes almost 30%
2-Hydroxyethyl acrylate (HEA), IPUC101 is also polar to some
extent. The HEA in the IPUC101 helps the PVP to dissolve or
disperse into the uncured material. The reinforcing effect on
IPUC101 is a function of both the composition of reinforcing agent
and the concentration of the reinforcing agent. In this embodiment
using PVP, the molecular weight was shown to have a large effect on
the reinforcement.
Preparation of PVP-Rein Forced IPUC101
[0039] In one embodiment, the desired amount of PVP and IPUC101
were dispensed into a sealed amber bottle. The mixture was stirred
at elevated temperature (for example 70.degree. C.) until all
solids were dissolved. In another embodiment, the PVP powder and
IPUC101 were added into a container and mixed using a Flextek mixer
(Flex-Tek Group, Greenwood, S.C., USA) at room temperature until
the powder was uniformly dissolved in the solution. Each resulting
solution was either clear or slightly cloudy. The inks were stored
at room temperature until use.
[0040] The reinforcing effect of adding PVP K15 to the IPUC101
formulation is shown in Table 2. The tensile strength and Shore
hardness of the material increases as PVP K15 is added to the
formulation. The tensile strength of the IPUC101 material without
PVP is 3.4 MPa, but increases to 4.6, 7.4, and 9.6 MPa at loading
fractions of 1.5%, 3%, and 5% PVP K15 respectively. The Shore A
hardness similarly increases from 35 to 38, 40, and 45
respectively. Notably, the elongation at break does not appear to
change significantly. Also, of note is the degree of reinforcement
at low loading fraction. Typical fillers require 30-100 phr for
adequate reinforcement, whereas PVP K15 reinforcement more than
doubles the tensile strength at only 3% loading.
TABLE-US-00001 TABLE 1 IPUC101 Formulation Percentage Supplier
Function Photomer 6230 29.98 IGM Resins Oligomer 2-Hydroxyethyl
acrylate 29 TCI America Monomer SR440 20 Sartomer Monomer Genomer
1121 20 Rahn AG Monomer Omnirad 819 1 IGM Resins Photo initiator
MEHQ 0.02 Sigma Photo inhibitor Total 100
TABLE-US-00002 TABLE 2 With and Without PVP K15 Reinforcement:
Mechanical Properties Tensile Elongation at Hardness strength (MPa)
break (%) (Shore A) IPUC101 3.4 160 35 IPUC101 - 1.5% K15 4.6 162
38 IPUC101 - 3% K15 7.4 166 40 IPUC101 - 5% K15 9.6 160 45
Table 3 below shows how viscosity of the acrylate resin IPUC101
formulation as a function of temperature without any reinforcing
filler as well as with varying amounts of reinforcing filler.
TABLE-US-00003 IPUC101 + IPUC101 + IPUC101 + IPUC101 1.5% K-15 3%
K-15 5% K-15 30 C. 30.70 cP 36.65 cP 43.17 cP 49.31 cP 40 C. 20.76
cP 24.66 cP 28.78 cP 31.81 cP 50 C. 14.89 cP 17.46 cP 20.19 cP
22.83 cP 60 C. 11.30 cP 13.09 cP 14.85 cP 16.58 cP 70 C. 8.48 cP
9.82 cP 11.24 cP 12.55 cP
EXAMPLE 2
Material: Acrylate Matrix Reinforced by a Second
Vinylpyrrolidone
[0041] In this embodiment, the vinylpyrrolidone is
Polyvinylpyrrolidone K12 provided by BASF. The preparation of
samples of IPUC101 reinforced with PVP K12 is the same with IPUC101
reinforced by PVP K15 (Mw: 4000-6000). The mechanical properties of
PVP K12 reinforced IPUC101 is shown in Table 3. As shown in Table
3, with 5 wt % of loading, there is a 40% of increase in tensile
strength. Although the tensile strength was increased, the increase
is not as significant as when PVP K15 is the reinforcing agent.
TABLE-US-00004 TABLE 3 PVP K12 Reinforcement: Mechanical Properties
Tensile Elongation at Hardness strength (MPa) break (%) (Shore A)
IPUC101 3.4 160 35 IPUC101 - 3% K12 3.7 156 40 IPUC101 - 5% K12 4.9
161 40
EXAMPLE 3
Material: Thiol-ene Matrix Reinforced by Poly(Methyl Methacrylate)
PMMA
[0042] In this embodiment, a new Thiol-ene matrix material, TE14,
is a self-formulated (see table 4), elastomeric thiol-ene material
with a tensile strength of 1 MPa, elongation at break of 107%, and
Shore hardness of 30 A. The reinforcing material PMMA (Mw: 120000)
was purchased from Sigma.
TABLE-US-00005 TABLE 4 TE14 Formulation Percentage Supplier
Function Trimethylolpropane tris(3- 15.15 Sigma Monomer
mercaptopropionate) 3,6-dioxa-1,8- 29.6 TCI America Monomer
octanedithiol Diallyl phthalate 53.7 TCI America Monomer
Vinylphosphonic acid 0.5 TCI America Photo inhibitor Omnirad 651 1
IGM Resins Photo initiator Pyrogallol 0.05 TCI America Photo
inhibitor Total 100
Preparation of TE14 Reinforced by PMMA
[0043] In this embodiment, a desired amount of each of PMMA and
TE14 was dispensed into a sealed amber bottle. The mixture was
stirred at elevated temperature (for example 70.degree. C.) until
all solids were dissolved. Alternatively, PMMA powder and TE14 were
added into a container and mixed through a Flextek mixer at room
temperature until the powder was dissolved in the solution. The
resultant solutions were clear. The composition was stored at room
temperature until use.
[0044] The reinforcing effect of adding PMMA to the TE14
formulation is shown in Table 5. The tensile strength and Shore
hardness of the material increases as PMMA is added to the
formulation.
TABLE-US-00006 TABLE 5 Reinforcing Effect of Adding PMMA to the
TE14 Formulation Tensile Elongation at Hardness strength (MPa)
break (%) (Shore A) TE14 1.0 107 30 TE14 - 3% PMMA 1.3 236 32 TE14
- 5% PMMA 1.7 184 35
[0045] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of the
disclosure. For example, various forms of the materials shown above
may be used, with steps re-ordered, added, or removed. Accordingly,
other implementations are within the scope of the following
claims.
[0046] The examples presented herein are intended to illustrate
potential and specific implementations of the present disclosure.
The examples are intended primarily for purposes of illustration of
the invention for those skilled in the art. No particular aspect or
aspects of the examples are necessarily intended to limit the scope
of the present invention.
[0047] The figures and descriptions of the present invention have
been simplified to illustrate elements that are relevant for a
clear understanding of the present invention, while eliminating,
for purposes of clarity, other elements. Those of ordinary skill in
the art may recognize, however, that these sorts of focused
discussions would not facilitate a better understanding of the
present disclosure, and therefore, a more detailed description of
such elements is not provided herein.
[0048] Unless otherwise indicated, all numbers expressing lengths,
widths, depths, or other dimensions and so forth used in the
specification and claims are to be understood in all instances as
indicating both the exact values as shown and as being modified by
the term "about." As used herein, the term "about" refers to a
.+-.10% variation from the nominal value. Accordingly, unless
indicated to the contrary, the numerical parameters set forth in
the specification and attached claims are approximations that may
vary depending upon the desired properties sought to be obtained.
At the very least, and not as an attempt to limit the application
of the doctrine of equivalents to the scope of the claims, each
numerical parameter should at least be construed in light of the
number of reported significant digits and by applying ordinary
rounding techniques. Any specific value may vary by 20%.
[0049] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The foregoing embodiments are therefore to be considered
in all respects illustrative rather than limiting on the invention
described herein. Scope of the invention is thus indicated by the
appended claims rather than by the foregoing description, and all
changes which come within the meaning and range of equivalency of
the claims are intended to be embraced therein.
[0050] It will be appreciated by those skilled in the art that
various modifications and changes may be made without departing
from the scope of the described technology. Such modifications and
changes are intended to fall within the scope of the embodiments
that are described. It will also be appreciated by those of skill
in the art that features included in one embodiment are
interchangeable with other embodiments; and that one or more
features from a depicted embodiment can be included with other
depicted embodiments in any combination.
* * * * *