U.S. patent application number 16/084645 was filed with the patent office on 2019-03-14 for radiation curable compositions for additive fabrication with improved toughness and high temperature resistance.
The applicant listed for this patent is DSM IP ASSETS, B.V.. Invention is credited to Luke KWISNEK, Brad SEURER.
Application Number | 20190077073 16/084645 |
Document ID | / |
Family ID | 58548850 |
Filed Date | 2019-03-14 |
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United States Patent
Application |
20190077073 |
Kind Code |
A1 |
KWISNEK; Luke ; et
al. |
March 14, 2019 |
RADIATION CURABLE COMPOSITIONS FOR ADDITIVE FABRICATION WITH
IMPROVED TOUGHNESS AND HIGH TEMPERATURE RESISTANCE
Abstract
Radiation curable compositions for additive fabrication with
improved toughness are described and claimed. Such resins include a
rubber toughenable base resin package and a liquid,
phase-separating toughening agent. The rubber toughenable base
resin, which may possess a suitably high average molecular weight
between crosslinks and may be a pre-reacted hydrophobic
macromolecule, may further include a cationically polymerizable
component, a radically polymerizable component, a cationic
photoinitiator, a free radical photoinitiator, and customary
additives. Also described and claimed are methods for forming a
three-dimensional objects using such radiation curable compositions
for additive fabrication with improved toughness, along with the
three-dimensional parts created therefrom.
Inventors: |
KWISNEK; Luke; (Elgin,
IL) ; SEURER; Brad; (Elgin, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DSM IP ASSETS, B.V. |
TE HEERLEN |
|
NL |
|
|
Family ID: |
58548850 |
Appl. No.: |
16/084645 |
Filed: |
March 14, 2017 |
PCT Filed: |
March 14, 2017 |
PCT NO: |
PCT/US2017/022311 |
371 Date: |
September 13, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62308023 |
Mar 14, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 91/00 20130101;
G03F 7/105 20130101; B29C 64/129 20170801; B29C 64/268 20170801;
G03F 7/027 20130101; C08L 67/06 20130101; C08K 5/55 20130101; B29C
64/277 20170801; B29C 64/393 20170801; G03F 7/038 20130101; G03F
7/0037 20130101; B33Y 70/00 20141201; C08L 63/00 20130101 |
International
Class: |
B29C 64/129 20060101
B29C064/129; B29C 64/393 20060101 B29C064/393; B29C 64/277 20060101
B29C064/277; B29C 64/268 20060101 B29C064/268; C08L 63/00 20060101
C08L063/00; C08L 91/00 20060101 C08L091/00; C08L 67/06 20060101
C08L067/06 |
Claims
1. A radiation curable composition for additive fabrication with
improved toughness comprising: a rubber toughenable base resin
further comprising a cationically polymerizable component; a
radically polymerizable component; a cationic photoinitiator; a
free radical photoinitiator; and optionally, customary additives;
and a liquid phase-separating toughening agent; wherein the liquid
phase-separating toughening agent is present in an amount, relative
to the weight of the rubber toughenable base resin, in a ratio from
1:99 to about 1:9, and wherein the average molecular weight between
crosslinks (M.sub.C) of the rubber toughenable base resin is
greater than 130 g/mol.
2. The radiation curable composition for additive fabrication with
improved toughness of claim 1, wherein the liquid phase-separating
toughening agent is a high molecular weight dimer fatty acid
polyol.
3. The radiation curable composition for additive fabrication with
improved toughness of claim 1, wherein the high molecular weight
polyol is selected to be configured to form, after curing of the
radiation curable composition, phase domains with an average size
of from about 2 microns to about 25 microns when measured according
to an Average Phase Domain Size Procedure.
4. The radiation curable composition for additive fabrication with
improved toughness of claim 1, wherein the high molecular weight
dimer fatty acid polyol possesses a molecular weight of greater
than 8000 g/mol.
5. The radiation curable composition for additive fabrication with
improved toughness of claim 4, wherein the high molecular weight
dimer fatty acid polyol is a propylene oxide or ethylene oxide.
6. The radiation curable composition for additive fabrication with
improved toughness of claim 1, wherein M.sub.C of the rubber
toughenable base resin is less than 500 g/mol.
7. The radiation curable composition for additive fabrication with
improved toughness of claim 6, wherein a three-dimensional
component created therefrom by means of an additive fabrication
process yields an elongation value that is at least 50% greater
than a corresponding elongation value of a three dimensional
component created from the constituent rubber toughenable base
resin of said radiation curable composition.
8. The radiation curable composition for additive fabrication with
improved toughness of claim 7, wherein a three-dimensional
component created therefrom by means of an additive fabrication
process yields an HDT value that is within at least 5 degrees
Celsius of a corresponding elongation value of a three dimensional
component created from the constituent rubber toughenable base
resin of said radiation curable composition.
9. A radiation curable composition for additive fabrication with
improved toughness comprising: a rubber toughenable base resin
further comprising (1) optionally, a cationically polymerizable
component; (2) a radically polymerizable component; (3) optionally,
a cationic photoinitiator; (4) a free radical photoinitiator; and
(5) optionally, customary additives; and a liquid phase-separating
toughening agent; wherein the liquid phase-separating toughening
agent is an epoxidized pre-reacted hydrophobic macromolecule;
wherein the average molecular weight between crosslinks (M.sub.C)
of the rubber toughenable base resin is greater than 180 g/mol; and
wherein the M.sub.C of the rubber toughenable base resin is less
than 260 g/mol.
10. The radiation curable composition for additive fabrication with
improved toughness of claim 9, wherein the rubber toughenable base
resin further contains, relative to the entire weight of the rubber
toughenable base resin, of less than about 40 wt. % of at least one
aromatic glycidyl epoxy, and at least about 5 wt. % of a polyol
component.
11. The radiation curable composition for additive fabrication with
improved toughness of claim 10, wherein the epoxidized pre-reacted
hydrophobic macromolecule is a triblock copolymer possessing
terminating epoxy- or acrylate-functional hard blocks; and at least
one immiscible soft block.
12. The radiation curable composition for additive fabrication with
improved toughness of claim 11, wherein the triblock copolymer is
formed by the reaction product of a soft-block originator with a
monofunctional anhydride such as hexahydrophthalic anhydride, and
then further reacting an epoxy-functional reactant.
13. The radiation curable composition for additive fabrication with
improved toughness of claim 12, wherein the soft-block originator
is selected from the group consisting of polybutadienes, polyols,
and polydmethylsiloxanes, and any combination thereof.
14. The radiation curable composition for additive fabrication with
improved toughness of claim 9, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from a triglyceride fatty
acid.
15. The radiation curable composition for additive fabrication with
improved toughness of claim 9, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from a tall oil, wherein the
epoxidized tall oil is an epoxidized vegetable oil, such as soybean
or linseed oil.
16. The radiation curable composition for additive fabrication with
improved toughness of claim 9, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from a compound of the
following formula: ##STR00009## wherein R.sub.1, R.sub.2, and
R.sub.3 are the same or different, and are each a C.sub.4-C.sub.50
unsaturated alkyl chain, wherein the unsaturation has been at least
30% epoxidized.
17. The radiation curable composition for additive fabrication with
improved toughness of claim 9, wherein the epoxidized pre-reacted
hydrophobic macromolecule possesses a molecular weight of from
about 800 g/mol to about 4000 g/mol.
18. The radiation curable composition for additive fabrication with
improved toughness of claim 17, wherein the epoxidized pre-reacted
hydrophobic macromolecule is present, relative to the weight of the
entire composition, in an amount from about 1% to about 20%, more
preferably from about 1.5% to about 12%.
19. A process of forming a three-dimensional object comprising the
steps of forming and selectively curing a liquid layer of the
radiation curable composition for additive fabrication with
improved toughness of any one of claims 1-18 with actinic radiation
and repeating the steps of forming and selectively curing the
liquid layer of the radiation curable composition for additive
fabrication of any one of claims 1-18 a plurality of times to
obtain a three-dimensional object.
20. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 62/308,023, filed 14 Mar. 2016, which is hereby
incorporated by reference in its entirety as if fully set forth
herein.
TECHNICAL FIELD
[0002] The present invention relates to radiation curable
compositions for additive fabrication with improved toughness, and
their application in additive fabrication processes.
BACKGROUND
[0003] Additive fabrication processes for producing three
dimensional objects are well known. Additive fabrication processes
utilize computer-aided design (CAD) data of an object to build
three-dimensional parts. These three-dimensional parts may be
formed from liquid resins, powders, or other materials.
[0004] A non-limiting example of an additive fabrication process is
stereolithography (SL). Stereolithography is a well-known process
for rapidly producing models, prototypes, patterns, and production
parts in certain applications. SL uses CAD data of an object
wherein the data is transformed into thin cross-sections of a
three-dimensional object. The data is loaded into a computer which
controls a laser that traces a pattern of a cross section through a
liquid radiation curable resin composition contained in a vat,
solidifying a thin layer of the resin corresponding to the cross
section. The solidified layer is recoated with resin and the laser
traces another cross section to harden another layer of resin on
top of the previous layer. The process is repeated layer by layer
until the three-dimensional object is completed. When initially
formed, the three-dimensional object is, in general, not fully
cured, and is called a "green model." Although not required, the
green model may be subjected to post-curing to enhance the
mechanical properties of the finished part. An example of an SL
process is described in U.S. Pat. No. 4,575,330.
[0005] There are several types of lasers used in stereolithography,
traditionally ranging from 193 nm to 355 nm in wavelength, although
other wavelength variants exist. The use of gas lasers to cure
liquid radiation curable resin compositions is well known. The
delivery of laser energy in a stereolithography system can be
Continuous Wave (CW) or Q-switched pulses. CW lasers provide
continuous laser energy and can be used in a high speed scanning
process. However, their output power is limited which reduces the
amount of curing that occurs during object creation. As a result
the finished object will need additional post process curing. In
addition, excess heat could be generated at the point of
irradiation which may be detrimental to the resin. Further, the use
of a laser requires scanning point by point on the resin which can
be time-consuming.
[0006] Other methods of additive fabrication utilize lamps or light
emitting diodes (LEDs). LEDs are semiconductor devices which
utilize the phenomenon of electroluminescence to generate light. At
present, LED UV light sources currently emit light at wavelengths
between 300 and 475 nm, with 365 nm, 390 nm, 395 nm, 405 nm, and
415 nm being common peak spectral outputs. See textbook,
"Light-Emitting Diodes" by E. Fred Schubert, 2.sup.nd Edition,
.COPYRGT. E. Fred Schubert 2006, published by Cambridge University
Press, for a more in-depth discussion of LED UV light sources.
[0007] Many additive fabrication applications require a
freshly-cured part, aka the "green model" to possess high
mechanical strength (modulus of elasticity, fracture strength).
This property, often referred to as "green strength," constitutes
an important property of the green model and is determined
essentially by the nature of the radiation curable composition
employed in combination with the type of apparatus used and degree
of exposure provided during part fabrication. Other important
properties of such compositions include a high sensitivity for the
radiation employed in the course of curing and a minimum amount of
curl or shrinkage deformation, permitting high shape definition of
the green model. Of course, not only the green model but also the
final cured article should have sufficiently optimized mechanical
properties.
[0008] It is also often imperative that the radiation curable
compositions used in additive manufacturing processes are capable
of imparting robust mechanical properties such as strength,
toughness and heat resistance, into the three-dimensional parts
cured therefrom.
[0009] Toughness is the extent to which a certain material, when
stressed, is able to absorb energy and plastically deform without
fracturing. It can be measured in several ways under different
stress conditions, and may vary for a given material depending on
the axis through which a stress is applied. Generally speaking, in
order to possess sufficient toughness, a material should be both
strong and ductile. Strength or ductility alone does not
necessarily render a materials tough. Certain high-strength but
brittle materials, such as ceramics, are not typically considered
to be tough. Conversely, high-ductility but weak materials such as
many rubbers are also do not possess significant toughness. To be
tough, therefore, a material should be able to withstand both high
stresses and high strains.
[0010] To be suitable for many industrial applications, the parts
created via additive fabrication processes are required to possess
a significant toughness. Certain standardized methods which are
used widely for evaluating the relative toughness of materials,
especially for those cured via additive fabrication processes,
include the Young's modulus of elasticity, elongation at break, as
well as the Charpy and Izod impact tests. The Young's modulus of
elasticity and elongation at break tend to approximates toughness
in the form of resilience over a relatively longer time period,
whereas the Charpy and Izod impact tests are considered to be a
better proxy for toughness under conditions in which a shock is
imparted over a shorter time period.
[0011] Additionally, many additive fabrication applications require
that radiation curable compositions used therein be able to impart
sufficient heat resistance to the parts cured therefrom. Such a
property, especially in combination with a high toughness, enables
thermoset plastics (such as those formed from radiation curable
compositions for additive fabrication) to approximate the
properties of injection molded engineering plastics, which are made
from thermoplastic polymers. The degree to which a radiation
curable (i.e. thermoset) material is able to withstand heat is
often characterized in the additive manufacturing industry by such
material's heat deflection temperature (HDT). HDT is the
temperature at which a sample of the cured material deforms by a
fixed distance under a specified load. It gives an indication of
how the material behaves when stressed at elevated temperatures.
The ultimate HDT for radiation curable thermoset materials is
determined by a number of factors, including the polymer network's
crosslink density, its chemical structure, the type of
tougheners/fillers employed, and the degree of cure. A high HDT is
important because it signals that a material is able to retain a
high degree of its maximum strength even at elevated
temperatures.
[0012] Existing conventional radiation curable materials suitable
for workability via additive fabrication processes are either
sufficiently tough, or are sufficiently heat resistant, but not
both. In materials science, tradeoffs between properties are
commonplace. Certain properties generally can be improved, but
often at the cost of reducing others. Perhaps the most limiting and
challenging of these tradeoffs, especially when considering the
constraints necessitated by formulation of radiation curable
compositions suitable for use in additive fabrication processes, is
that of toughness and heat resistance.
[0013] Although other factors such as molecular structure can
contribute to polymer morphology, adjusting a composition's
crosslink density is a well-known method in the art of formulation
of radiation curable compositions for additive fabrication to
modify such composition's toughness and heat resistance. Crosslink
density can be defined as the number of effective cross-links per
unit volume of the cured polymer. With respect to crosslink density
modifications, there exists a well-known inverse relationship
between toughness and heat resistance. That is, as crosslink
density increases, a thermoset material's HDT increases, but its
toughness concomitantly decreases. Conversely, as the cross-link
density decreases, the toughness increases but HDT performance is
known to suffer. A discussion of the effects of modification of
cross-link density in thermoset resins is discussed in, e.g., pp.
8-10 of "Handbook of Thermoset Plastics", Third Edition (Edited by
Hanna Dodiuk and Sidney H. Goodman).
[0014] There exist several known approaches to toughening,
including the use of chain transfer agents, flexibilizing additives
including polyols, long side chain or main chain functional
monomers and oligomers. While improving toughness, these known
approaches also compromise heat resistance as measured by HDT.
[0015] For prototyping and other niche applications, this tradeoff
has been generally considered acceptable. However, to expand the
range of applications for radiation curable compositions produced
via additive fabrication processes, new materials are desired that
have the combination of both high toughness and high heat
resistance. Achieving this combination of properties would open the
door to many new applications, including high temperature
gas/liquid flow prototyping, and the manufacturing of end-use
parts. Indeed, such improved thermoset materials would bridge the
current gap to engineering thermoplastics.
[0016] Finally, the viscosity of liquid radiation curable
compositions is of particular importance in many additive
fabrication processes, such as vat-based processes like
stereolithography as described above. Many additives or
constituents of the composition which might improve the toughness
or HDT of the three-dimensional parts cured therefrom make such
existing liquid radiation curable resins are highly viscous; that
is, they are sufficiently flow-resistant such that they will not
readily form a smooth layer of liquid photocurable resin over the
just formed solid layer to ensure accurate cure by actinic
radiation. With highly viscous resins, forming a new layer of
liquid photocurable resin over the top of a previously-cured layer
becomes a time consuming process. Other concerns with regards to
high viscosity liquid radiation curable compositions for additive
fabrication processes such as stereolithography are described in,
e.g. US20150044623, assigned to DSM IP Assets, B.V.
[0017] From the foregoing, it is evident that a heretofore unmet
need exists to provide improved radiation curable compositions
suitable for use in additive fabrication processes that possess
sufficient green strength, low viscosity, and which also are
capable of forming three-dimensional parts which possess
simultaneously improved toughness and excellent heat resistance,
such that they are ideal for a greater number of applications
currently only suitable for engineering thermoplastic
materials.
BRIEF SUMMARY
[0018] A first aspect of the claimed invention is a radiation
curable composition for additive fabrication with improved
toughness comprising: [0019] a rubber toughenable base resin
further comprising [0020] a cationically polymerizable component;
[0021] a radically polymerizable component; [0022] a cationic
photoinitiator; [0023] a free radical photoinitiator; and [0024]
optionally, customary additives; and [0025] a liquid
phase-separating toughening agent; [0026] wherein the liquid
phase-separating toughening agent is present in an amount, relative
to the weight of the rubber toughenable base resin, in a ratio from
about 1:99 to about 1:3, more preferably about 1:99 to about 1:4,
more preferably about 1:99 to about 1:9, more preferably about 1:50
to about 1:12, more preferably about 1:19; and [0027] wherein the
average molecular weight between crosslinks (M.sub.C) of the rubber
toughenable base resin is greater than 130 g/mol, more preferably
greater than 150 g/mol; in another embodiment more preferably
greater than 160 g/mol; and in another embodiment greater than 180
g/mol.
[0028] A second aspect of the claimed invention is a radiation
curable composition for additive fabrication with improved
toughness comprising: [0029] a rubber toughenable base resin
further comprising [0030] (1) optionally, a cationically
polymerizable component; [0031] (2) a radically polymerizable
component; [0032] (3) optionally, a cationic photoinitiator; [0033]
(4) a free radical photoinitiator; and [0034] (5) optionally,
customary additives; and [0035] a liquid phase-separating
toughening agent; [0036] wherein the liquid phase-separating
toughening agent is an epoxidized pre-reacted hydrophobic
macromolecule.
[0037] A third aspect of the claimed invention is a process of
forming a three-dimensional object comprising the steps of forming
and selectively curing a liquid layer of the radiation curable
composition for additive fabrication with improved toughness
according to either the first or second aspects of the claimed
invention with actinic radiation and repeating the steps of forming
and selectively curing the liquid layer of the radiation curable
composition for additive fabrication according to the first or
second aspects of the claimed invention a plurality of times to
obtain a three-dimensional object.
[0038] A fourth aspect of the claimed invention is the
three-dimensional object formed by the process according to the
third aspect of the claimed invention from the radiation curable
composition for additive fabrication with improved toughness
according to either the first or second aspects of the claimed
invention.
DETAILED DESCRIPTION
[0039] Throughout this document, if a molecule is referred to as
"high molecular weight", it shall be understood that such molecule
possesses a molecular weight of greater than about 2,000
daltons.
[0040] A first aspect of the claimed invention is a radiation
curable composition for additive fabrication with improved
toughness comprising: [0041] a rubber toughenable base resin
further comprising [0042] a cationically polymerizable component;
[0043] a radically polymerizable component; [0044] a cationic
photoinitiator; [0045] a free radical photoinitiator; and [0046]
optionally, customary additives; and
[0047] a liquid phase-separating toughening agent;
[0048] wherein the liquid phase-separating toughening agent is
present in an amount, relative to the weight of the rubber
toughenable base resin, in a ratio from about 1:99 to about 1:3,
more preferably about 1:99 to about 1:4, more preferably about 1:99
to about 1:9, more preferably about 1:50 to about 1:12, more
preferably about 1:19%; and [0049] wherein the average molecular
weight between crosslinks (M.sub.C) of the rubber toughenable base
resin is greater than 130 g/mol, more preferably greater than 150
g/mol; in another embodiment more preferably greater than 160
g/mol; and in another embodiment greater than 180 g/mol.
Rubber Toughenable Base Resins
[0050] All embodiments of radiation curable compositions with
improved toughness for additive fabrication according to the
present invention possess, as at least a constituent part, a rubber
toughenable base resin. This base resin forms a polymer matrix
within which toughening agents, which themselves can be liquid and
soluble in the base resin prior to curing, phase separate forming
domains from the surrounding polymer network of the base resin
during the curing process. Although such a rubber toughenable base
resin, on its own, sufficiently enables the creation of three
dimensional parts via an additive fabrication process, the
three-dimensional parts created therefrom may lack the requisite
toughness to be considered suitable for many end-use applications.
As used herein, "rubber toughenable" does not require that rubbers
explicitly be used to toughen the base resin; rather, it merely
signifies that such resins are able to be toughened by virtue of a
soft-phase separation mechanism.
[0051] Rubber toughenable base resins according to the present
invention may possess sub-constituents divided into five potential
categories: optionally, at least one cationically polymerizable
component; at least one radically-polymerizable component;
optionally, a cationic photoinitiator; a free-radical
photoinitiator; and customary additives. Each of these potential
components of a base resin according to the present invention is
henceforth discussed in turn.
Cationically Polymerizable Component
[0052] In accordance with an embodiment, the rubber toughenable
base resin comprises at least one cationically polymerizable
component; that is a component which undergoes polymerization
initiated by cations or in the presence of acid generators. The
cationically polymerizable components may be monomers, oligomers,
and/or polymers, and may contain aliphatic, aromatic,
cycloaliphatic, arylaliphatic, heterocyclic moiety(ies), and any
combination thereof. Suitable cyclic ether compounds can comprise
cyclic ether groups as side groups or groups that form part of an
alicyclic or heterocyclic ring system.
[0053] The cationic polymerizable component is selected from the
group consisting of cyclic ether compounds, cyclic acetal
compounds, cyclic thioethers compounds, spiro-orthoester compounds,
cyclic lactone compounds, and vinyl ether compounds, and any
combination thereof.
[0054] Suitable cationically polymerizable components include
cyclic ether compounds such as epoxy compounds and oxetanes, cyclic
lactone compounds, cyclic acetal compounds, cyclic thioether
compounds, spiro orthoester compounds, and vinylether compounds.
Specific examples of cationically polymerizable components include
bisphenol A diglycidyl ether, bisphenol F diglycidyl ether,
bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl
ether, brominated bisphenol F diglycidyl ether, brominated
bisphenol S diglycidyl ether, epoxy novolac resins, hydrogenated
bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl
ether, hydrogenated bisphenol S diglycidyl ether,
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate,
2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)-cyclohexane-1,4-dioxane,
bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide,
4-vinylepoxycyclohexane, vinylcyclohexene dioxide, limonene oxide,
limonene dioxide, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,
3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate,
.epsilon.-caprolactone-modified
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylates,
trimethylcaprolactone-modified
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylates,
.beta.-methyl-.delta.-valerolactone-modified
3,4-epoxycyclohexcylmethyl-3',4'-epoxycyclohexane carboxylates,
methylenebis(3,4-epoxycyclohexane), bicyclohexyl-3,3'-epoxide,
bis(3,4-epoxycyclohexyl) with a linkage of --O--, --S--, --SO--,
--SO.sub.2--, --C(CH.sub.3).sub.2--, --CBr.sub.2--,
--C(CBr.sub.3).sub.2--, --C(CF.sub.3).sub.2--,
--C(CCl.sub.3).sub.2--, or --CH(C.sub.6H.sub.5)--,
dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl) ether of
ethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate),
epoxyhexahydrodioctylphthalate, epoxyhexahydro-di-2-ethylhexyl
phthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol
diglycidyl ether, neopentylglycol diglycidyl ether, glycerol
triglycidyl ether, trimethylolpropane triglycidyl ether,
polyethylene glycol diglycidyl ether, polypropylene glycol
diglycidyl ether, diglycidyl esters of aliphatic long-chain dibasic
acids, monoglycidyl ethers of aliphatic higher alcohols,
monoglycidyl ethers of phenol, cresol, butyl phenol, or polyether
alcohols obtained by the addition of alkylene oxide to these
compounds, glycidyl esters of higher fatty acids, epoxybutylstearic
acid, epoxyoctylstearic acid, epoxidated linseed oil, epoxidated
polybutadiene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,
3-ethyl-3-hydroxymethyloxetane,
3-ethyl-3-(3-hydroxypropyl)oxymethyloxetane,
3-ethyl-3-(4-hydroxybutyl)oxymethyloxetane,
3-ethyl-3-(5-hydroxypentyl)oxymethyloxetane,
3-ethyl-3-phenoxymethyloxetane,
bis((1-ethyl(3-oxetanyl))methyl)ether,
3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane,
3-ethyl-((triethoxysilylpropoxymethyl)oxetane,
3-(meth)-allyloxymethyl-3-ethyloxetane,
3-hydroxymethyl-3-ethyloxetane,
(3-ethyl-3-oxetanylmethoxy)methylbenzene,
4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene,
4-methoxy-[1-(3-ethyl-3-oxetanylmethoxy)methyl]-benzene,
[1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether,
isobutoxymethyl(3-ethyl-3-oxetanylmethyl)ether,
2-ethylhexyl(3-ethyl-3-oxetanylmethyl)ether, ethyldiethylene
glycol(3-ethyl-3-oxetanylmethyl)ether, dicyclopentadiene
(3-ethyl-3-oxetanylmethyl)ether,
dicyclopentenyloxyethyl(3-ethyl-3-oxetanylmethyl)ether,
dicyclopentenyl(3-ethyl-3-oxetanylmethyl)ether,
tetrahydrofurfuyl(3-ethyl-3-oxetanylmethyl)ether,
2-hydroxyethyl(3-ethyl-3-oxetanylmethyl)ether,
2-hydroxypropyl(3-ethyl-3-oxetanylmethyl)ether, and any combination
thereof.
[0055] The cationically polymerizable component may optionally also
contain polyfunctional materials including dendritic polymers such
as dendrimers, linear dendritic polymers, dendrigraft polymers,
hyperbranched polymers, star branched polymers, and hypergraft
polymers with epoxy or oxetane functional groups. The dendritic
polymers may contain one type of polymerizable functional group or
different types of polymerizable functional groups, for example,
epoxy and oxetane functions.
[0056] In an embodiment, the rubber toughenable base resin of the
present invention also or instead comprises one or more mono or
poly glycidylethers of aliphatic alcohols, aliphatic polyols,
polyesterpolyols or polyetherpolyols. Examples of preferred
components include 1,4-butanedioldiglycidylether, glycidylethers of
polyoxyethylene and polyoxypropylene glycols and triols of
molecular weights from about 200 to about 10,000; glycidylethers of
polytetramethylene glycol or poly(oxyethylene-oxybutylene) random
or block copolymers. In a specific embodiment, the cationically
polymerizable component comprises a polyfunctional glycidylether
that lacks a cyclohexane ring in the molecule. In another specific
embodiment, the cationically polymerizable component includes a
neopentyl glycol diglycidyl ether. In another specific embodiment,
the cationically polymerizable component includes a 1,4
cyclohexanedimethanol diglycidyl ether.
[0057] Examples of commercially available preferred polyfunctional
glycidylethers are Erisys.TM. GE 22 (Erisys.TM. products are
available from Emerald Performance Materials.TM.) Heloxy.TM. 48,
Heloxy.TM. 67, Heloxy.TM. 68, Heloxy.TM. 107 (Heloxy.TM. modifiers
are available from Momentive Specialty Chemicals), and
Grilonit.RTM. F713. Examples of commercially available preferred
monofunctional glycidylethers are Heloxy.TM. 71, Heloxy.TM. 505,
Heloxy.TM. 7, Heloxy.TM. 8, and Heloxy.TM. 61.
[0058] In an embodiment, the epoxide is
3,4-epoxycyclohexylmethyl-3',4-epoxycyclohexanecarboxylate
(available as CELLOXIDE.TM. 2021P from Daicel Chemical, or as
CYRACURE.TM. UVR-6105 from Dow Chemical), hydrogenated bisphenol
A-epichlorohydrin based epoxy resin (available as EPON.TM. 1510
from Momentive), 1,4-cyclohexanedimethanol diglycidyl ether
(available as HELOXY.TM. 107 from Momentive), a hydrogenated
bisphenol A diglycidyl ether (available as EPON.TM. 825 from
Momentive), and any combination thereof.
[0059] The above-mentioned cationically polymerizable compounds can
be used singly or in combination of two or more thereof. In
embodiments of the invention, the cationic polymerizable component
further comprises at least two different epoxy components. In a
specific embodiment, the cationic polymerizable component includes
a cycloaliphatic epoxy, for example, a cycloaliphatic epoxy with 2
or more than 2 epoxy groups. In another specific embodiment, the
cationic polymerizable component includes an epoxy having an
aromatic or aliphatic glycidyl ether group with 2 (difunctional) or
more than 2 (polyfunctional) epoxy groups. In yet another specific
embodiment, the rubber toughenable base resin does not contain a
cationic polymerizable component at all.
[0060] The rubber toughenable base resin can therefore include
suitable amounts of the cationic polymerizable component, for
example, in certain embodiments, in an amount from about 0 wt % to
about 85% by weight of the rubber toughenable base resin, in
further embodiments from about 35 wt % to about 75 wt %, and in
further embodiments from about 35 wt % to about 65 wt % of the
rubber toughenable base resin.
[0061] In other embodiments of the invention, the cationically
polymerizable component also includes one or more oxetanes. In a
specific embodiment, the cationic polymerizable component includes
an oxetane, for example, an oxetane containing 1, 2 or more than 2
oxetane groups. If utilized in the composition, the oxetane
component is present in a suitable amount from about 5 to about 30
wt % of the rubber toughenable base resin. In another embodiment,
the oxetane component is present in an amount from about 10 to
about 25 wt % of the rubber toughenable base resin, and in yet
another embodiment, the oxetane component is present in an amount
from 15 to about 20 wt % of the rubber toughenable base resin.
Radically Polymerizable Component
[0062] In accordance with an embodiment of the invention, the
rubber toughenable base resin comprises at least one free-radical
polymerizable component, that is, a component which undergoes
polymerization initiated by free radicals. The free-radical
polymerizable components are monomers, oligomers, and/or polymers;
they are monofunctional or polyfunctional materials, i.e., have 1,
2, 3, 4, 5, 6, 7, 8, 9, 10 . . . 20 . . . 30 . . . 40 . . . 50 . .
. 100, or more functional groups that can polymerize by free
radical initiation, may contain aliphatic, aromatic,
cycloaliphatic, arylaliphatic, heterocyclic moiety(ies), or any
combination thereof. Examples of polyfunctional materials include
dendritic polymers such as dendrimers, linear dendritic polymers,
dendrigraft polymers, hyperbranched polymers, star branched
polymers, and hypergraft polymers; see, e.g., US 2009/0093564 A1.
The dendritic polymers may contain one type of polymerizable
functional group or different types of polymerizable functional
groups, for example, acrylates and methacrylate functions.
[0063] Examples of free-radical polymerizable components include
acrylates and methacrylates such as isobornyl (meth)acrylate,
bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate,
dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate,
cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 4-butylcyclohexyl
(meth)acrylate, acryloyl morpholine, (meth)acrylic acid,
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,
2-hydroxybutyl (meth)acrylate, methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate,
butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate,
t-butyl (meth)acrylate, pentyl (meth)acrylate, caprolactone
acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl
(meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl
(meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate,
undecyl (meth)acrylate, lauryl (meth)acrylate, stearyl
(meth)acrylate, isostearyl (meth)acrylate, tetrahydrofurfuryl
(meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol
(meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate,
polyethylene glycol mono(meth)acrylate, polypropylene glycol
mono(meth)acrylate, methoxyethylene glycol (meth)acrylate,
ethoxyethyl (meth)acrylate, methoxypolyethylene glycol
(meth)acrylate, methoxypolypropylene glycol (meth)acrylate,
diacetone (meth)acrylamide, beta-carboxyethyl (meth)acrylate,
phthalic acid (meth)acrylate, dimethylaminoethyl (meth)acrylate,
diethylaminoethyl (meth)acrylate, butylcarbamylethyl
(meth)acrylate, n-isopropyl (meth)acrylamide fluorinated
(meth)acrylate, 7-amino-3,7-dimethyloctyl (meth)acrylate.
[0064] Examples of polyfunctional free-radical polymerizable
components include those with (meth)acryloyl groups such as
trimethylolpropane tri(meth)acrylate, pentaerythritol
(meth)acrylate, ethylene glycol di(meth)acrylate, bisphenol A
diglycidyl ether di(meth)acrylate, dicyclopentadiene dimethanol
di(meth)acrylate,
[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl
acrylate;
3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5-
]undecane di(meth)acrylate; dipentaerythritol
monohydroxypenta(meth)acrylate, propoxylated trimethylolpropane
tri(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate,
tetraethylene glycol di(meth)acrylate, polyethylene glycol
di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, neopentyl glycol di(meth)acrylate, polybutanediol
di(meth)acrylate, tripropyleneglycol di(meth)acrylate, glycerol
tri(meth)acrylate, phosphoric acid mono- and di(meth)acrylates,
C.sub.7-C.sub.20 alkyl di(meth)acrylates,
tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate,
tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, pentaerythritol
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
dipentaerythritol hexa(meth)crylate, tricyclodecane diyl dimethyl
di(meth)acrylate and alkoxylated versions (e.g., ethoxylated and/or
propoxylated) of any of the preceding monomers, and also
di(meth)acrylate of a diol which is an ethylene oxide or propylene
oxide adduct to bisphenol A, di(meth)acrylate of a diol which is an
ethylene oxide or propylene oxide adduct to hydrogenated bisphenol
A, epoxy (meth)acrylate which is a (meth)acrylate adduct to
bisphenol A of diglycidyl ether, diacrylate of polyoxyalkylated
bisphenol A, and triethylene glycol divinyl ether, and adducts of
hydroxyethyl acrylate.
[0065] In accordance with an embodiment, the radically
polymerizable component is a polyfunctional (meth)acrylate. The
polyfunctional (meth)acrylates may include all methacryloyl groups,
all acryloyl groups, or any combination of methacryloyl and
acryloyl groups. In an embodiment, the free-radical polymerizable
component is selected from the group consisting of bisphenol A
diglycidyl ether di(meth)acrylate, ethoxylated or propoxylated
bisphenol A or bisphenol F di(meth)acrylate, dicyclopentadiene
dimethanol di(meth)acrylate,
[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl
acrylate, dipentaerythritol monohydroxypenta(meth)acrylate,
dipentaerythritol penta(meth)acrylate, dipentaerythritol
hexa(meth)crylate, propoxylated trimethylolpropane
tri(meth)acrylate, and propoxylated neopentyl glycol
di(meth)acrylate, and any combination thereof.
[0066] In a preferred embodiment, the polyfunctional (meth)acrylate
has more than 2, more preferably more than 3, and more preferably
greater than 4 functional groups.
[0067] In another preferred embodiment, the radically polymerizable
component consists exclusively of a single polyfunctional
(meth)acrylate component. In further embodiments, the exclusive
radically polymerizable component is tetra-functional, in further
embodiments, the exclusive radically polymerizable component is
penta-functional, and in further embodiments, the exclusive
radically polymerizable component is hexa-functional.
[0068] In another embodiment, the free-radical polymerizable
component is selected from the group consisting of bisphenol A
diglycidyl ether diacrylate, dicyclopentadiene dimethanol
diacrylate,
[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl
acrylate, dipentaerythritol monohydroxypentaacrylate, propoxylated
trimethylolpropane triacrylate, and propoxylated neopentyl glycol
diacrylate, and any combination thereof.
[0069] In specific embodiments, the rubber toughenable base resin
of the invention includes one or more of bisphenol A diglycidyl
ether di(meth)acrylate, dicyclopentadiene dimethanol
di(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate,
propoxylated trimethylolpropane tri(meth)acrylate, and/or
propoxylated neopentyl glycol di(meth)acrylate, and more
specifically one or more of bisphenol A diglycidyl ether
diacrylate, dicyclopentadiene dimethanol diacrylate,
dipentaerythritol pentaacrylate, propoxylated trimethylolpropane
triacrylate, and/or propoxylated neopentyl glycol diacrylate.
[0070] The above-mentioned radically polymerizable compounds can be
used singly or in combination of two or more thereof. The rubber
toughenable base resin can include any suitable amount of the
free-radical polymerizable components, for example, in certain
embodiments, in an amount up to about 40 wt % of the composition,
in certain embodiments, from about 2 to about 40 wt % of the
composition, in other embodiments from about 5 to about 30 wt %,
and in further embodiments from about 10 to about 20 wt % of the
composition. Particularly in embodiments wherein cationically
curable components are not used, the rubber toughenable base resin
can include up to 95 wt % of one or more radically polymerizable
components.
[0071] The rubber toughenable base resins of the present invention
also include a photoinitiating system. The photoinitiating system
can include a free-radical photoinitiator and/or a cationic
photoinitiator. In accordance with an embodiment, the radiation
curable composition includes a photoinitiating system contains at
least one photoinitiator having a cationic initiating function, and
at least one photoinitiator having a free radical initiating
function. Additionally, the photoinitiating system can include a
photoinitiator that contains both free-radical initiating function
and cationic initiating function on the same molecule. In an
embodiment, the photoinitiating system includes one or more
free-radical photoinitiators and no cationic photoinitiators. The
photoinitiator is a compound that chemically changes due to the
action of light or the synergy between the action of light and the
electronic excitation of a sensitizing dye to produce at least one
of a radical, an acid, and a base.
Cationic Photoinitiator
[0072] In accordance with an embodiment, the rubber toughenable
base resin includes a cationic photoinitiator. Cationic
photoinitiators initiate cationic ring-opening polymerization upon
irradiation of light. In a preferred embodiment, a sulfonium salt
photoinitiator is used, for example, dialkylphenacylsulfonium
salts, aromatic sulfonium salts, triaryl sulfonium salts, and any
combination thereof.
[0073] In accordance with an embodiment, the rubber toughenable
base resin includes a cationic photoinitiator. The cationic
photoinitiator initiates cationic ring-opening polymerization upon
irradiation of light.
[0074] In an embodiment, any suitable cationic photoinitiator can
be used, for example, those with cations selected from the group
consisting of onium salts, halonium salts, iodosyl salts, selenium
salts, sulfonium salts, sulfoxonium salts, diazonium salts,
metallocene salts, isoquinolinium salts, phosphonium salts,
arsonium salts, tropylium salts, dialkylphenacylsulfonium salts,
thiopyrilium salts, diaryl iodonium salts, triaryl sulfonium salts,
ferrocenes, di(cyclopentadienyliron)arene salt compounds, and
pyridinium salts, and any combination thereof.
[0075] In another embodiment, the cation of the cationic
photoinitiator is selected from the group consisting of aromatic
diazonium salts, aromatic sulfonium salts, aromatic iodonium salts,
metallocene based compounds, aromatic phosphonium salts, and any
combination thereof. In another embodiment, the cation is a
polymeric sulfonium salt, such as in U.S. Pat. No. 5,380,923 or
5,047,568, or other aromatic heteroatom-containing cations and
naphthyl-sulfonium salts such as in U.S. Pat. Nos. 7,611,817,
7,230,122, US2011/0039205, US2009/0182172, U.S. Pat. No. 7,678,528,
EP2308865, WO2010046240, or EP2218715. In another embodiment, the
cationic photoinitiator is selected from the group consisting of
triarylsulfonium salts, diaryliodonium salts, and metallocene based
compounds, and any combination thereof. Onium salts, e.g., iodonium
salts and sulfonium salts, and ferrocenium salts, have the
advantage that they are generally more thermally stable.
[0076] In a particular embodiment, the cationic photoinitiator has
an anion selected from the group consisting of BF.sub.4.sup.-,
AsF.sub.6.sup.-, SbF.sub.6.sup.-, PF.sub.6.sup.-,
[B(CF.sub.3).sub.4].sup.-, B(C.sub.6F.sub.5).sub.4.sup.-,
B[C.sub.6H.sub.3-3,5(CF.sub.3).sub.2].sub.4.sup.-,
B(C.sub.6H.sub.4CF.sub.3).sub.4.sup.-,
B(C.sub.6H.sub.3F.sub.2).sub.4.sup.-,
B[C.sub.6F.sub.4-4(CF.sub.3)].sub.4.sup.-,
Ga(C.sub.6F.sub.5).sub.4.sup.-,
[(C.sub.6F.sub.5).sub.3B--C.sub.3H.sub.3N.sub.2--B(C.sub.6F.sub.5).sub.3]-
.sup.-,
[(C.sub.6F.sub.5).sub.3B--NH.sub.2--B(C.sub.6F.sub.5).sub.3].sup.--
, tetrakis(3,5-difluoro-4-alkyloxyphenyl)borate,
tetrakis(2,3,5,6-tetrafluoro-4-alkyloxyphenyl)borate,
perfluoroalkylsulfonates, tris[(perfluoroalkyl)sulfonyl]methides,
bis[(perfluoroalkyl)sulfonyl]imides, perfluoroalkylphosphates,
tris(perfluoroalkyl)trifluorophosphates,
bis(perfluoroalkyl)tetrafluorophosphates,
tris(pentafluoroethyl)trifluorophosphates, and
(CH.sub.6B.sub.11Br.sub.6).sup.-, (CH.sub.6B.sub.11Cl.sub.6).sup.-
and other halogenated carborane anions.
[0077] A survey of other onium salt initiators and/or metallocene
salts can be found in "UV Curing, Science and Technology", (Editor
S. P. Pappas, Technology Marketing Corp., 642 Westover Road,
Stamford, Conn., U.S.A.) or "Chemistry & Technology of UV &
EB Formulation for Coatings, Inks & Paints", Vol. 3 (edited by
P. K. T. Oldring).
[0078] In an embodiment, the cationic photoinitiator has a cation
selected from the group consisting of aromatic sulfonium salts,
aromatic iodonium salts, and metallocene based compounds with at
least an anion selected from the group consisting of
SbF.sub.6.sup.-, PF.sub.6.sup.-, B(C.sub.6F.sub.5).sub.4.sup.-,
[B(CF.sub.3).sub.4].sup.-,
tetrakis(3,5-difluoro-4-methoxyphenyl)borate,
perfluoroalkylsulfonates, perfluoroalkylphosphates,
tris[(perfluoroalkyl)sulfonyl]methides, and
[(C.sub.2F.sub.5).sub.3PF.sub.3].sup.-.
[0079] Examples of cationic photoinitiators useful for curing at
300-475 nm, particularly at 365 nm UV light, without a sensitizer
include
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
tetrakis(pentafluorophenyl)borate,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
tetrakis(3,5-difluoro-4-methyloxyphenyl)borate,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)
sulfonium tetrakis(2,3,5,6-tetrafluoro-4-methyloxyphenyl)borate,
tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate (Irgacure.RTM. PAG 290 from
BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tris[(trifluoromethyl)sulfonyl]methide (Irgacure.RTM. GSID 26-1
from BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium
hexafluorophosphate (Irgacure.RTM. 270 from BASF), and HS-1
available from San-Apro Ltd.
[0080] Preferred cationic photoinitiators include, either alone or
in a mixture: bis[4-diphenylsulfoniumphenyl]sulfide
bishexafluoroantimonate; thiophenoxyphenylsulfonium
hexafluoroantimonate (available as Chivacure 1176 from Chitec),
tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate (Irgacure.RTM. PAG 290 from
BASF), tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tris[(trifluoromethyl)sulfonyl]methide (Irgacure.RTM. GSID 26-1
from BASF), and tris(4-(4-acetylphenyl)thiophenyl)sulfonium
hexafluorophosphate (Irgacure.RTM. 270 from BASF),
[4-(1-methylethyl)phenyl](4-methylphenyl) iodonium
tetrakis(pentafluorophenyl)borate (available as Rhodorsil 2074 from
Rhodia),
4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfon-
ium hexafluoroantimonate (as SP-172 from Adeka), SP-300 from Adeka,
and aromatic sulfonium salts with anions of
(PF.sub.6-m(C.sub.nF.sub.2n+1).sub.m).sup.- where m is an integer
from 1 to 5, and n is an integer from 1 to 4 (available as CPI-200K
or CPI-200S, which are monovalent sulfonium salts from San-Apro
Ltd., TK-1 available from San-Apro Ltd., or HS-1 available from
San-Apro Ltd.).
[0081] In various embodiments, the liquid radiation curable resin
composition for additive fabrication may be irradiated by laser or
LED light operating at any wavelength in either the UV or visible
light spectrum. In particular embodiments, the irradiation is from
a laser or LED emitting a wavelength of from 340 nm to 415 nm. In
particular embodiments, the laser or LED source emits a peak
wavelength of about 340 nm, 355 nm, 365 nm, 375 nm, 385 nm, 395 nm,
405 nm, or 415 nm.
[0082] In an embodiment of the invention, the rubber toughenable
base resin comprises an aromatic triaryl sulfonium salt cationic
photoinitiator.
[0083] Use of aromatic triaryl sulfonium salts in additive
fabrication applications is known. Please see US 20120251841 to DSM
IP Assets, B.V. (which is hereby incorporated in its entirety),
U.S. Pat. No. 6,368,769, to Asahi Denki Kogyo, which discusses
aromatic triaryl sulfonium salts with tetraryl borate anions,
including tetrakis(pentafluorophenyl)borate, and use of the
compounds in stereolithography applications. Triarylsulfonium salts
are disclosed in, for example, J Photopolymer Science & Tech
(2000), 13(1), 117-118 and J Poly Science, Part A (2008), 46(11),
3820-29. Triarylsulfonium salts Ar.sub.3S.sup.+MXn.sup.- with
complex metal halide anions such as BF.sub.4.sup.-,
AsF.sub.6.sup.-, PF.sub.6.sup.-, and SbF.sub.6.sup.-, are disclosed
in J Polymr Sci, Part A (1996), 34(16), 3231-3253.
[0084] The use of aromatic triaryl sulfonium salts as the cationic
photoinitiator in radiation curable resins is desirable in additive
fabrication processes because the resulting resin attains a fast
photospeed, good thermal-stability, and good photo-stability.
[0085] In an embodiment, the cationic photoinitiator is an aromatic
triaryl sulfonium salt that is more specifically an R-substituted
aromatic thioether triaryl sulfonium
tetrakis(pentafluorophenyl)borate cationic photoinitiator, having a
tetrakis(pentafluorophenyl)borate anion. A suitable R-substituted
aromatic thioether triaryl sulfonium
tetrakis(pentafluorophenyl)borate cationic photoinitiator is
tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate.
Tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate is known commercially as
IRGACURE.RTM. PAG-290 and is available from Ciba/BASF.
[0086] In another embodiment, the cationic photoinitiator is an
aromatic triaryl sulfonium salt that possesses an anion represented
by SbF.sub.6.sup.-, PF.sub.6.sup.-, BF.sub.4.sup.-,
(CF.sub.3CF.sub.2).sub.3PF.sub.3.sup.-,
(C.sub.6F.sub.5).sub.4B.sup.-,
((CF.sub.3).sub.2C.sub.6H.sub.3).sub.4B.sup.-,
(C.sub.6F.sub.5).sub.4Ga.sup.-,
((CF.sub.3).sub.2C.sub.6H.sub.3).sub.4Ga.sup.-,
trifluoromethanesulfonate, nonafluorobutanesulfonate,
methanesulfonate, butanesulfonate, benzenesulfonate, or
p-toluenesulfonate. Such photoinitiators are described in, for
example, U.S. Pat. No. 8,617,787.
[0087] A particularly preferred aromatic triaryl sulfonium cationic
photoinitiator has an anion that is a fluoroalkyl-substituted
fluorophosphate. Commercial examples of an aromatic triaryl
sulfonium cationic photoinitiator having a fluoroalkyl-substituted
fluorophosphate anion is the CPI-200 series (for example
CPI-200K.RTM. or CPI-2105.RTM.) or 300 series, available from
San-Apro Limited.
[0088] The rubber toughenable base resin can include any suitable
amount of the cationic photoinitiator, for example, in certain
embodiments, from 0% to about 15% by weight of the rubber
toughenable base resin, in certain embodiments, up to about 5% by
weight of the rubber toughenable base resin, and in further
embodiments from about 2% to about 10% by weight of the rubber
toughenable base resin, and in other embodiments, from about 0.1%
to about 5% by weight of the rubber toughenable base resin. In a
further embodiment, the amount of cationic photoinitiator is from
about 0.2 wt % to about 4 wt % of the rubber toughenable base
resin, and in other embodiments from about 0.5 wt % to about 3 wt %
of the rubber toughenable base resin. In embodiments of the present
invention wherein cationically curable components are not used, it
may not be desirable or necessary to additionally include a
cationic photoinitiator as described herein.
[0089] In some embodiments, depending on the wavelength of light
used for curing the radiation curable composition for additive
fabrication with improved toughness, it is desirable for the rubber
toughenable base resin to include a photosensitizer. The term
"photosensitizer" is used to refer to any substance that either
increases the rate of photoinitiated polymerization or shifts the
wavelength at which polymerization occurs; see textbook by G.
Odian, Principles of Polymerization, 3.sup.rd Ed., 1991, page 222.
A variety of compounds can be used as photosensitizers, including
heterocyclic and fused-ring aromatic hydrocarbons, organic dyes,
and aromatic ketones. Examples of photosensitizers include those
selected from the group consisting of methanones, xanthenones,
pyrenemethanols, anthracenes, pyrene, perylene, quinones,
xanthones, thioxanthones, benzoyl esters, benzophenones, and any
combination thereof. Particular examples of photosensitizers
include those selected from the group consisting of
[4-[(4-methylphenyl)thio]phenyl]phenyl-methanone,
isopropyl-9H-thioxanthen-9-one, 1-pyrenemethanol,
9-(hydroxymethyl)anthracene, 9,10-diethoxyanthracene,
9,10-dimethoxyanthracene, 9,10-dipropoxyanthracene,
9,10-dibutyloxyanthracene, 9-anthracenemethanol acetate,
2-ethyl-9,10-dimethoxyanthracene,
2-methyl-9,10-dimethoxyanthracene,
2-t-butyl-9,10-dimethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene
and 2-methyl-9,10-diethoxyanthracene, anthracene, anthraquinones,
2-methylanthraquinone, 2-ethylanthraquinone,
2-tertbutylanthraquinone, 1-chloroanthraquinone,
2-amylanthraquinone, thioxanthones and xanthones, isopropyl
thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone,
1-chloro-4-propoxythioxanthone, methyl benzoyl formate (Darocur MBF
from BASF), methyl-2-benzoyl benzoate (Chivacure OMB from Chitec),
4-benzoyl-4'-methyl diphenyl sulphide (Chivacure BMS from Chitec),
4,4'-bis(diethylamino) benzophenone (Chivacure EMK from Chitec),
and any combination thereof.
[0090] In an embodiment, the rubber toughenable base resin may also
contain various photoinitiators of different sensitivity to
radiation of emission lines with different wavelengths to obtain a
better utilization of a UV light source. The use of known
photoinitiators of different sensitivity to radiation of emission
lines is well known in the art of additive fabrication, and may be
selected in accordance with radiation sources of, for example, 351,
nm 355 nm, 365 nm, 385 nm, and 405 nm. In this context it is
advantageous for the various photoinitiators to be selected such,
and employed in a concentration such, that equal optical absorption
is produced with the emission lines used.
[0091] The rubber toughenable base resin can include any suitable
amount of the photosensitizer, for example, in certain embodiments,
in an amount up to about 10% by weight of the rubber toughenable
base resin, in certain embodiments, up to about 5% by weight of the
rubber toughenable base resin, and in further embodiments from
about 0.05% to about 2% by weight of the rubber toughenable base
resin.
Free-Radical Photoinitiator
[0092] Typically, free radical photoinitiators are divided into
those that form radicals by cleavage, known as "Norrish Type I" and
those that form radicals by hydrogen abstraction, known as "Norrish
type II". The Norrish type II photoinitiators require a hydrogen
donor, which serves as the free radical source. As the initiation
is based on a bimolecular reaction, the Norrrish type II
photoinitiators are generally slower than Norrish type I
photoinitiators which are based on the unimolecular formation of
radicals. On the other hand, Norrish type II photoinitiators
possess better optical absorption properties in the near-UV
spectroscopic region. Photolysis of aromatic ketones, such as
benzophenone, thioxanthones, benzil, and quinones, in the presence
of hydrogen donors, such as alcohols, amines, or thiols leads to
the formation of a radical produced from the carbonyl compound
(ketyl-type radical) and another radical derived from the hydrogen
donor. The photopolymerization of vinyl monomers is usually
initiated by the radicals produced from the hydrogen donor. The
ketyl radicals are usually not reactive toward vinyl monomers
because of the steric hindrance and the delocalization of an
unpaired electron.
[0093] To successfully formulate a radiation curable resin for
additive fabrication, it is necessary to review the wavelength
sensitivity of the photoinitiator(s) present in the resin
composition to determine if they will be activated by the radiation
source chosen to provide the curing light.
[0094] In accordance with an embodiment, the rubber toughenable
base resin includes at least one free radical photoinitiator, e.g.,
those selected from the group consisting of benzoylphosphine
oxides, aryl ketones, benzophenones, hydroxylated ketones,
1-hydroxyphenyl ketones, ketals, metallocenes, and any combination
thereof.
[0095] In an embodiment, the rubber toughenable base resin includes
at least one free-radical photoinitiator selected from the group
consisting of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and
2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide,
bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide,
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1,
2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone,
2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-o-
ne, 4-benzoyl-4'-methyl diphenyl sulphide, 4,4'-bis(diethylamino)
benzophenone, and 4,4'-bis(N,N'-dimethylamino) benzophenone
(Michler's ketone), benzophenone, 4-methyl benzophenone,
2,4,6-trimethyl benzophenone, dimethoxybenzophenone,
1-hydroxycyclohexyl phenyl ketone, phenyl
(1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy)
phenyl]-2-methyl-1-propanone,
4-isopropylphenyl(1-hydroxyisopropyl)ketone,
oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl] propanone],
camphorquinone, 4,4'-bis(diethylamino) benzophenone, benzil
dimethyl ketal, bis(eta 5-2-4-cyclopentadien-1-yl)
bis[2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl] titanium, and any
combination thereof.
[0096] For light sources emitting in the 300-475 nm wavelength
range, especially those emitting at 365 nm, 390 nm, or 395 nm,
examples of suitable free-radical photoinitiators absorbing in this
area include: benzoylphosphine oxides, such as, for example,
2,4,6-trimethylbenzoyl diphenylphosphine oxide (Lucirin TPO from
BASF) and 2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide
(Lucirin TPO-L from BASF),
bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819 or
BAPO from Ciba),
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1 (Irgacure
907 from Ciba), 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)
phenyl]-1-butanone (Irgacure 369 from Ciba),
2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-o-
ne (Irgacure 379 from Ciba), 4-benzoyl-4'-methyl diphenyl sulphide
(Chivacure BMS from Chitec), 4,4'-bis(diethylamino) benzophenone
(Chivacure EMK from Chitec), and 4,4'-bis(N,N'-dimethylamino)
benzophenone (Michler's ketone). Also suitable are mixtures
thereof.
[0097] Additionally, photosensitizers are useful in conjunction
with photoinitiators in effecting cure with LED light sources
emitting in this wavelength range. Examples of suitable
photosensitizers include: anthraquinones, such as
2-methylanthraquinone, 2-ethylanthraquinone,
2-tertbutylanthraquinone, 1-chloroanthraquinone, and
2-amylanthraquinone, thioxanthones and xanthones, such as isopropyl
thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, and
1-chloro-4-propoxythioxanthone, methyl benzoyl formate (Darocur MBF
from Ciba), methyl-2-benzoyl benzoate (Chivacure OMB from Chitec),
4-benzoyl-4'-methyl diphenyl sulphide (Chivacure BMS from Chitec),
4,4'-bis(diethylamino) benzophenone (Chivacure EMK from
Chitec).
[0098] It is possible for UV radiation sources to be designed to
emit light at shorter wavelengths. For light sources emitting at
wavelengths from between about 100 and about 300 nm, it is possible
to employ a photosensitizer with a photoinitiator. When
photosensitizers, such as those previously listed are present in
the formulation, other photoinitiators absorbing at shorter
wavelengths can be used. Examples of such photoinitiators include:
benzophenones, such as benzophenone, 4-methyl benzophenone,
2,4,6-trimethyl benzophenone, dimethoxybenzophenone, and
1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone,
phenyl (1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hroxyethoxy)
phenyl]-2-methyl-1-propanone, and
4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal,
and oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]
propanone] (Esacure KIP 150 from Lamberti).
[0099] Radiation sources can also be designed to emit at higher
wavelengths. For radiation sources emitting light at wavelengths
from about 475 nm to about 900 nm, examples of suitable free
radical photoinitiators include: camphorquinone,
4,4'-bis(diethylamino) benzophenone (Chivacure EMK from Chitec),
4,4'-bis(N,N'-dimethylamino) benzophenone (Michler's ketone),
bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide ("BAPO," or
Irgacure 819 from Ciba), metallocenes such as bis (eta
5-2-4-cyclopentadien-1-yl) bis [2,6-difluoro-3-(1H-pyrrol-1-yl)
phenyl] titanium (Irgacure 784 from Ciba), and the visible light
photoinitiators from Spectra Group Limited, Inc. such as H-Nu 470,
H-Nu-535, H-Nu-635, H-Nu-Blue-640, and H-Nu-Blue-660.
[0100] In one embodiment of the instant claimed invention, the
light emitted by the radiation source is UVA radiation, which is
radiation with a wavelength between about 320 and about 400 nm. In
one embodiment of the instant claimed invention, the light emitted
by the radiation source is UVB radiation, which is radiation with a
wavelength between about 280 and about 320 nm. In one embodiment of
the instant claimed invention, the light emitted by the radiation
source is UVC radiation, which is radiation with a wavelength
between about 100 and about 280 nm.
[0101] The rubber toughenable base resin can include any suitable
amount of the free-radical photoinitiator as component, for
example, in certain embodiments, in an amount up to about 10 wt %
of the rubber toughenable base resin, in certain embodiments, from
about 0.1 to about 10 wt % of the rubber toughenable base resin,
and in further embodiments from about 1 to about 6 wt % of the
rubber toughenable base resin.
Customary Additives
[0102] In embodiments of the present invention, the rubber
toughenable base resin further contains customary additives.
Customary additives to the rubber toughenable base resin may
include without limitation stabilizers, fillers, dyes, pigments,
antioxidants, wetting agents, chain transfer agents such as
polyols, leveling agents, defoamers, surfactants, bubble breakers,
acid scavengers, thickeners, flame retardants, silane coupling
agents, ultraviolet absorbers, resin particles, core-shell particle
impact modifiers, and the like. Such components may be added in
known amounts and to desired effect.
[0103] Stabilizers are often added to the rubber toughenable base
resin in order to further prevent a viscosity build-up, for
instance a viscosity build-up during usage in a solid imaging
process. Useful stabilizers include those described in, e.g., U.S.
Pat. No. 5,665,792. In the instant claimed invention, the presence
of a stabilizer is optional. In a specific embodiment, the liquid
radiation curable resin composition for additive fabrication
comprises from 0.1 wt % to 3% of a stabilizer.
[0104] If present, such stabilizers are usually hydrocarbon
carboxylic acid salts of group IA and IIA metals. Most preferred
examples of these salts are sodium bicarbonate, potassium
bicarbonate, and rubidium carbonate. Solid stabilizers are
generally not preferred in filled resin compositions. Alternative
stabilizers include polyvinylpyrrolidones and
polyacrylonitriles.
[0105] Fillers are often added to radiation curable compositions
for additive fabrication to impart increased strength, rigidity and
modulus. Useful fillers include those described in, e.g. U.S. Pat.
No. 9,228,073, assigned to DSM IP Assets, B.V. Also described in
the '073 patent are useful prescriptions for stabilized matrices
comprising more than one filler type which may be followed to
impart a filled matrix with improved resistance to filler particle
precipitation.
[0106] Core-shell particles are also often added to radiation
curable compositions for additive fabrication to impart increased
toughness. Useful core-shell particles include those described in,
e.g. publication of patent application number US20100304088,
assigned to DSM IP Assets, B.V.
Compatible Base Resin Matrices
[0107] Inventors have discovered that not all base resins are
sufficiently able to be toughened whilst still sufficiently
maintaining heat resistance upon the inclusion of the various
liquid phase-separating toughening agents prescribed according to
the present invention. Therefore, it has been presently discovered
that such liquid phase-separating toughening agents function as
desired only in an appropriately compatible toughenable base resin
matrix. In embodiments of the present invention, this compatibility
has been linked to the base resin's crosslink density.
[0108] Although it is well-known that resins with a higher
crosslink density are, all else being equal, more brittle and
therefore exhibit reduced toughness, Inventors have surprisingly
discovered that matrices with a crosslink density outside of
certain ranges are also incapable of being further toughened by the
incorporation of certain liquid phase-separating toughening agents
prescribed herein in any sufficient fashion. Furthermore, such base
resins typically exhibit the classical concomitant reduction in
heat resistance after the incorporation of such liquid
phase-separating toughening agents. By contrast, base resin
matrices with a crosslink density that falls within certain ranges
will readily toughen when combined with the liquid phase-separating
toughening agents prescribed herein, and further surprisingly
exhibit a tendency to largely maintain the concomitant HDT values,
in contravention of the longstanding principle of the known inverse
relationship between toughness and HDT. In an embodiment,
compositions according to the current invention exhibit an increase
in elongation at break of at least 5%, more preferably at least
20%, more preferably at least 30%, more preferably at least 50%,
and in some embodiments at least 100%, all while maintaining an HDT
value of within 7 degrees, more preferably 5 degrees, more
preferably 3 degrees, more preferably within 1 degree when compared
to compositions with incompatible rubber toughenable base resin
matrices, or those not including such liquid phase-separating
toughening agents.
[0109] A preferred method used herein to quantify the crosslink
density of a network is by way of calculating the molecular weight
between crosslinks, M.sub.C. M.sub.C, which can be expressed in
terms of the unit g/mol, is the average molecular weight between
cross-link junction points in a crosslinked network. M.sub.C values
may be derived in different ways. One experimental method involves
a derivation based upon data evidencing a network's elongation. As
used herein, however, "ideal" M.sub.C values are derived by
calculations based upon the nature of the individual components of
a formulation, along with such components' individual molecular
weights and functionalities. A formula for calculating such ideal
M.sub.C values of a cured network, taken from James Mark "Physical
Properties of Polymers" 3rd Edition, Cambridge University Press,
2004, P. 11-12, is as follows:
Mc = .rho. ( .upsilon. V ) ##EQU00001##
where: M.sub.C=molecular weight between cross-links (in g/mol)
[0110] .rho.=density of network (in g/cubic centimeter) [0111]
.upsilon.=total number of moles of network chains (in mol) [0112]
V=volume of network (in cc)
[0113] This model as applied herein assumes the network to be a
perfectly connected continuum with no looping (i.e. non-active
chains) and no dead-ends (i.e. from monofunctional species or
initiator fragments). With this model, each cross-linker molecule
(functionality >2, i.e. a diacrylate or diepoxide each have a
defined M.sub.C functionality of 4) contributes a number of network
chains equal to its functionality divided by two, i.e. one network
chain is formed for every 2 functionality provided by a
cross-linker molecule. These crosslinker molecules are the only
components considered for the determination of .upsilon..
Furthermore, for the avoidance of any doubt, photoinitiators are
not included in in the calculations as used herein.
[0114] One example to visualize this approach is that for a resin
mixture of just difunctional species, only a linear polymer would
be formed, thereby precluding any crosslinking network. In such a
case, .upsilon.=0, and therefore the M.sub.C calculated according
to this method would approach infinity (i.e. be undefined according
to the formula). With the introduction of a single cross-linker
that contributes to .upsilon., M.sub.C values begin to decrease to
a definable value.
[0115] It is further assumed that all radiation curable
compositions for additive fabrication evaluated herein possess
components adding up to 100 grams total and possess a constant
density of 1.0 g/cc (nearly all unfilled radiation curable
compositions for stereolithography, for example, have comparable
densities, with actual values ranging from approximately 1.1 to
1.2). Therefore, for all calculations made herein, V is assumed to
be a constant 100 cc.
[0116] When determining M.sub.C functionalities, the following
should be taken into account: Vinyl ethers or Acrylates=2, Oxirane
(ALL, including epoxy, cycloaliphatic, oxetane)=2, primary OH=1,
secondary OH=0 (assume nonreactive).
[0117] To calculate .upsilon. total for the network, calculate
.upsilon. for each component and sum the values accordingly. A
demonstration of .upsilon. may be derived by way of example by
presupposing a resin with a 4-functional component as the only
crosslinker (remaining species are difunctional and so they only
connect and extend the junction cross-link points) with a molecular
weight of 252 g/mol which is further present in an amount relative
to the entire composition with which it is associated of 35 wt %
(35 grams out of 100 grams). The .upsilon. for this component, (and
thus the entire network since this is the only cross-linker
molecule), would therefore be calculated as follows:
35 grams*(1 mole/252 grams)*(4 functionality/mole)*(1 mole network
chains/2 functionality)=0.278 moles of network chains contributed
by this component.
[0118] Since this component in this particular example is the only
cross-linker and therefore the only component contributing to the
formation of network chains, the overall M.sub.C in this example is
calculated as:
M.sub.C=(1 g/cc)/(0.278 mol/100 g)=100 g/0.278 mol=360 g/mol
[0119] Using this method, M.sub.C values according to the present
invention can be derived.
[0120] In an embodiment of the invention, compatible rubber
toughenable base resin possess an M.sub.C value of at least 130
g/mol, more preferably greater than 150 g/mol. In another
embodiment, compatible rubber toughenable base resins possess an
M.sub.C value of at least 160 g/mol; and in another embodiment
greater than 180 g/mol. In yet another embodiment, the M.sub.C of a
compatible rubber toughenable base resin is less than 2,000 g/mol,
more preferably less than 1,000 g/mol, more preferably less than
500 g/mol, more preferably less than 400 g/mol, more preferably
less than 300 g/mol, more preferably less than 280 g/mol, more
preferably less than 260 g/mol, more preferably less than 230
g/mol, more preferably less than 200 g/mol. If the M.sub.C value of
the rubber toughenable base resin becomes too low, the highly
crosslinked network does not readily toughen even upon the addition
of liquid phase-separating toughening agents. If the M.sub.C value
is too high, on the other hand, the polymer network of the base
resin itself is not sufficiently crosslinked to enable the general
properties (modulus, HDT) necessary to form for suitability in many
end-use applications common of components created via additive
fabrication processes.
Liquid Phase-Separating Toughening Agents
[0121] Radiation curable compositions for additive fabrication with
improved toughness according to the present invention also possess
at least one liquid, phase-separating toughening agent. Such agents
are liquid at room temperature and are typically soluble within the
base resin prior to cure. Then, upon curing of the entire radiation
curable composition into which they are incorporated, the
toughening agents phase-separate forming in-situ rubbery domains
residing in the interstitial spaces within the crosslink matrix
formed by the surrounding thermoset polymer. These phase domains
may be light refractive or not, depending on their size and
refractive index relative to the remainder of the polymer matrix.
If they are sufficiently sized and light refractive, they will
impart a white color to the final cured product. This visual effect
is particularly desired in certain applications, and obviates the
need for the inclusion of additives such as pigments, which have
the undesirable effect of precipitating in a vat of material over
time, along with the fact that such pigments may impact the
associated composition's viscosity and photospeed in an undesirable
fashion.
[0122] Inventors have discovered that certain size ranges of the
resulting phase domains are an important indicator of the relative
amount of simultaneous improved rubber toughenability and heat
resistance imparted in the corresponding cured object (when
compared to the base resin matrix alone), particularly when such
phase domains are added to compatible base resin matrices as
prescribed elsewhere herein. Inventors have surprisingly found that
such rubber toughenability and heat resistance are particularly
optimized if the liquid phase-separating toughening agents are
selected such that they are configured to yield average phase
domains of at least 2 microns and less than 25 microns, more
preferably from about 5 microns to about 20 microns, or from about
7 microns to about 15 microns, when measured according to the
average phase domain size procedure outlined in the following
paragraph.
[0123] Average Phase Domain Size Procedure:
[0124] A few drops of resin are placed on a microscope slide. The
microscope slide has 10 mil Mylar squares as shims on the edges. A
second microscope slide is then placed on top of the shims,
sandwiching and spreading out the liquid to be 10 mil (+/-1 mil)
thickness. This glass-resin-glass sandwich is then placed in a
conventional stereolithography machine, for example an SLA Viper
from 3D Systems, and imaged over using appropriate Ec/Dp and other
imaging parameters suitable for the resin being used. A square is
drawn over the sandwich in order to cure the entire liquid area.
The square is imaged three times to ensure full curing of the
liquid. The top glass slide is then removed. The microscope slide
with the thin film cured on top is then investigated by the optical
microscope. Using 20.times. magnification, domains of phase
separation are clearly visible. The diameters of ten (10) of these
domains are measured and tabulated. The average value of these ten
values is the average phase domain size.
[0125] If selected in accordance with compatible rubber toughenable
base resins as prescribed herein above, therefore, such liquid
phase-separating toughening agents can impart a substantial
toughening affect upon the cured composition, without a substantial
sacrifice in the cured composition's heat deflection temperature,
as is known to occur with existing reagents and methods for
improving toughness into radiation curable compositions for
additive fabrication.
[0126] In an embodiment, when incorporated into a sufficiently
compatible rubber toughenable base resin matrix as described above,
the liquid phase-separating toughening agent can be a high
molecular weight dimer fatty acid polyol. In an embodiment, the
high molecular weight dimer fatty acid polyol possesses a molecular
weight of greater than 2000 g/mol, more preferably 3000 g/mol, more
preferably greater than 4000 g/mol. In another embodiment, such
polyol possesses a molecular weight of 8000 g/mol. In an
embodiment, the high molecular weight dimer fatty acid polyol
possesses a molecular weight of up to 10,000 g/mol. Molecular
weights above this value tend to detrimentally affect the viscosity
of the entire radiation curable composition, making such
compositions unsuitable for effective use in many additive
fabrication processes. In another embodiment, the high molecular
weight dimer fatty acid polyol is a propylene oxide or ethylene
oxide.
[0127] Commercially available components of such high liquid
phase-separating toughening agents includes high molecular weight
polyols such as the Acclaim series of polypropylene glycols with
varying molecular weight, such as Acclaim 4200 and 8200, as well as
Croda epoxy-functional toughening agents such as B-tough A2 and
Beta Tough 2CR. Also suitable for use from Croda as such a
liquid-phase separating toughening agent are the Priplast.TM.
series polyester polyols.
[0128] A second aspect of the claimed invention is a radiation
curable composition for additive fabrication with improved
toughness comprising: [0129] a liquid phase-separating toughening
agent; and [0130] a rubber toughenable base resin further
comprising [0131] (1) optionally, a cationically polymerizable
component; [0132] (2) a radically polymerizable component; [0133]
(3) optionally, a cationic photoinitiator; [0134] (4) a free
radical photoinitiator; and [0135] (5) optionally, customary
additives; [0136] wherein the liquid phase-separating toughening
agent is an epoxidized pre-reacted hydrophobic macromolecule.
Liquid Phase-Separating Toughening Agents which are Pre-Reacted
Epoxidized Hydrophobic Macromolecules
[0137] According to other embodiments consistent with the second
aspect of the claimed invention, the radiation curable compositions
for additive fabrication with improved toughness incorporate at
least one liquid phase-separating toughening agent which is an
epoxidized, pre-reacted, hydrophobic macromolecule. For purposes
herein, "epoxidized" means that such toughening agent is
epoxy-functional; that is, it is able to undergo a ring-opening
reaction of one or more epoxy moieties present anywhere on its
molecule. Such moieties need not be terminating epoxy groups.
"Pre-reacted" for purposes herein means that such epoxidization
and/or macromolecule synthesis is completed prior to any
incorporation of such toughening agent into the surrounding rubber
toughenable base resin. "Hydrophobic" means that such
macromolecule, once synthesized, possesses an absence of attraction
from a proximate mass of water. Without wishing to be bound by any
theory, it is believed that a toughening agent's level of
hydrophobicity is correlated to an acceleration of its
phase-separation from the surrounding rubber toughenable base resin
during curing.
[0138] In an embodiment, the epoxidized pre-reacted hydrophobic
macromolecule is a triblock copolymer possessing terminating epoxy-
or acrylate-functional hard blocks and at least one immiscible soft
block. In an embodiment, the triblock copolymer is formed by the
reaction product of a soft-block originator with a monofunctional
anhydride, and then further reacting an epoxy-functional reactant.
In an embodiment, the soft-block originator is selected from the
group consisting of polybutadienes, polyols, and
polydmethylsiloxanes, and any combination thereof, although other
known soft-block originators and combinations may be used. In a
preferred embodiment, the monofunctional anhydride is an
hexahydropthalic anhydride because it possesses a known superior
water stability, but any monofunctional anhydrides may be used as
is suitable.
[0139] According to another embodiment of the invention, the
epoxidized pre-reacted hydrophobic macromolecule is derived from a
triglyceride fatty acid or a tall oil. Certain non-limiting
preferred tall oils include vegetable-based oils such as soybean or
linseed oil, along with any of the drying oils such as linseed,
tung, poppy seed, walnut, and rapeseed oil, to name a few.
[0140] In an embodiment the epoxidized pre-reacted hydrophobic
macromolecule is derived from a compound of the following
formula:
##STR00001##
wherein R.sub.1, R.sub.2, and R.sub.3 are the same or different,
and are each a C.sub.4-C.sub.50 unsaturated alkyl chain, wherein
the unsaturation has been at least 2% epoxidized, more preferably
10% epoxidized, more preferably 30% epoxidized. In another
embodiment, the epoxidized pre-reacted hydrophobic macromolecule is
derived from the an epoxidized soybean oil (ESO), such as the
following:
##STR00002##
[0141] In an embodiment, the epoxidized triglyceride or tall oil is
reacted with an alkyl chain carboxylic acid to form a pre-reacted
hydrophobic macromolecule.
[0142] As would be well-known by one of ordinary skill in the art
to which this invention applies, the synthesis of epoxidized
pre-reacted hydrophobic macromolecules according to the present
invention are carried out in the presence of various catalysts. Any
suitable catalysts known in the art could be used, especially weak
base or chromium-base catalysts. In an embodiment, the catalyst
used to enable to formation of the pre-reacted hydrophobic
macromolecule is triphenylphosphine, available from Sigma Aldrich,
or a chromium catalyst, such as the commercial product AMC-2 from
AMPAC Fine Chemicals.
[0143] According to an embodiment, the ratio of equivalents
utilized in the synthesis of the epoxidized pre-reacted hydrophobic
macromolecule is 1 part epoxidized triglyceride or tall oils to 2
part alkyl chain carboxylic acids. In another embodiment, that
ratio is 1:3. In other embodiments, the epoxidized pre-reacted
hydrophobic macromolecule is synthesized by reacting, in terms of
equivalents, a ratio of ESO to an alkyl chain carboxylic acid from
about 2:3 to about 2:7, more preferably from about 1:2 to about
1:3.
[0144] In embodiments, the ratios and reagents are maintained
within limits to ensure an appropriate length of the alkyl chain
attached to the triglyceride or tall oil. This is because it is
believed that the alkyl chain's length turn directly affects the
macromolecule's hydrophobicity. Thus if the alkyl chain becomes too
long, the macromolecule becomes too hydrophobic and will not
readily react with the surrounding rubber toughenable base resin
matrix. If it becomes too short, on the other hand, it may not
possess the requisite hydrophobicity to phase-separate from the
matrix.
[0145] The epoxidized pre-reacted hydrophobic macromolecules of the
present invention can optionally be further acrylate functionalized
prior to incorporation in the rubber toughenable base resin. This
can occur, by for example, acrylate-functionalizing the alkyl chain
carboxylic acid prior to the reaction with the epoxidized
triglyceride or tall oil in the presence of a suitable catalyst to
yield an acrylate-functionalized epoxidized pre-reacted hydrophobic
macromolecule. Especially, when this has occurred, the accompanying
rubber toughenable base resin need not necessarily contain
cationically curable components. Therefore, in an embodiment of the
invention wherein the liquid phase-separating toughening agent is
an acrylate functionalized pre-reacted hydrophobic macromolecule,
components (1) and (3), namely, the cationically polymerizable
component and cationic photoinitiator, respectively, are not
present in the composition. Regardless, the descriptions of
examples and combinations of cationically polymerizable components,
free-radically polymerizable components, cationic photoinitiators,
free-radical photoinitiators, and additives as described in the
description accompanying the first aspect of the present invention
are also equally available for creating rubber toughenable resins
suitable for use according to the second aspect of the present
invention as well.
Solubility of Liquid Phase-Separating Toughening Agents, and its
Relation to Compatibility with Rubber Toughenable Base Resin
Matrices
[0146] Inventors have surprisingly further discovered that a liquid
phase-separating toughening agent's solubility within its
associated rubber toughenable base resin is of significant
importance when ensuring optimum usefulness therewith.
Specifically, according to certain embodiments of the invention, if
the solubility delta of the liquid phase-separating toughening
agent and its associated rubber toughenable base resin is within
certain ranges, the toughness of the resulting cured
three-dimensional articles are improved, and the heat resistance is
sufficiently maintained. In embodiments of the invention, this
factor, along with the aforementioned M.sub.C values of the
corresponding rubber toughenable base resin, enable the skilled
artisan to select optimally compatible compositional substituents
that impart superior toughness and heat resistance properties into
the three-dimensional objects cured therefrom.
[0147] As used herein, solubility "deltas" can be expressed by
using the Hansen solubility parameters (HSP). The deltas expressed
herein would represent the theoretical straight-line distance in
the three dimensional Hansen space between the rubber toughenable
base resin and the liquid phase-separating toughening agent.
According to a preferred embodiment, the deltas are from about 10
to about 25, in another embodiment from 10-15, in another
embodiment from 15-20, in another embodiment from 20-25.
[0148] A third aspect of the claimed invention is a process of
forming a three-dimensional object comprising the steps of forming
and selectively curing a liquid layer of the radiation curable
composition for additive fabrication with improved toughness
according to either the first or second aspects of the claimed
invention with actinic radiation and repeating the steps of forming
and selectively curing the liquid layer of the radiation curable
composition for additive fabrication according to the first or
second aspects of the claimed invention a plurality of times to
obtain a three-dimensional object.
[0149] A fourth aspect of the claimed invention is the
three-dimensional object formed by the process according to the
third aspect of the claimed invention from the radiation curable
composition for additive fabrication with improved toughness
according to either the first or second aspects of the claimed
invention.
[0150] The following examples further illustrate the invention but,
of course, should not be construed as in any way limiting its
scope.
EXAMPLES
[0151] These examples illustrate embodiments of radiation curable
compositions for additive fabrication with improved toughness
according to the instant invention. Table 1 describes the various
commercially available raw materials which constitute various
components or sub-components, as the case may be, of the radiation
curable compositions for additive fabrication with improved
toughness used in the present examples. Table 2, meanwhile,
describes the synthesis of the liquid hydrophobic macromolecular
phase-separating toughening agents which are not commercially
available and are used in the present examples.
TABLE-US-00001 TABLE 1 Function in Supplier/ Component Formula
Chemical Descriptor Manufacturer PerFORM Base resin Radiation
curable composition with DSM cationically & free-radically
Somos .RTM. polymerizable components, cationic & free-radical
photoinitiator Prototherm Base resin Radiation curable composition
with DSM cationically & free-radically Somos .RTM.
polymerizable components, cationic & free-radical
photoinitiator; manufacturer-provided M.sub.C of 141.3 Protogen
18120 Base resin Radiation curable composition with DSM (Protogen)
cationically & free-radically Somos .RTM. polymerizable
components, cationic & free-radical photoinitiator;
manufacturer-provided M.sub.C of 163.2 Somos NeXt Base resin
Radiation curable composition with DSM cationically &
free-radically Somos .RTM. polymerizable components, cationic &
free-radical photoinitiator; core-shell particles;
manufacturer-provided M.sub.C of 173.4 Modified NeXt Base resin
Radiation curable composition with DSM cationically &
free-radically Somos .RTM. polymerizable components, cationic &
free-radical photoinitiator; filtered to remove core-shell
particles Clear Base resin Radiation curable composition for
FormLabs additive fabrication containing free- radically
polymerizable component and free-radical photoinitiator Acclaim
8200 Liquid phase Polyether polyol, 8,000 MW diol Covestro
separating toughing agent (LPSTA) Acclaim 4200 LPSTA Polyether
polyol, 4,200 MW diol Covestro Beta Tough 2cr LPSTA 44% solution of
naturally derived Croda epoxidized rubber in butanediol diglycidyl
ether Polybutadiene Liquid phase polybutadiene polyol; 1,300 g/mol
and Cray Valley oligomer (PBD) separating M.sub.n 2,800 g/mol
toughening sub-agent (LPSTsub) Pluronic F127 LPSTsub Polyethylene
oxide-polypropylene BASF oxide-polyethylene oxide triblock
copolymer; Mn ~13,000 g/mol Hexahydrophthalic LPSTsub
Hexahydrophthalic anhydride Sigma- anhydride Aldrich (HHPA)
Celloxide 2021P Cationically 3,4-epoxycyclohexylmethyl-3',4'-
Daicel polymerizable epoxycyclohexanecarboxylate Corporation
component Epon 828 Cationically Bisphenol A diglycidyl ether
Momentive polymerizable component --OH Functional LPSTsub
Polydimethylsiloxane Polyol; M.sub.n ~1,000 g/mol GELEST PDMS
(PDMS) Jenkinol .RTM. 680 LPSTsub Epoxidized soybean oil Acme-
(ESO) Hardesty Triphenyl- Catalyst "TPP" Sigma- phosphine Aldrich
AFC Catalyst Chromium-based catalyst AMPAC ACCELERATOR Fine AMC-2
Chemicals (AFC) Janie I-16 (I-16) LPSTsub Branched alkyl chain
acid; isopalmitic Jarchem (2-hexyldecanoic acid) Jaric I-24 (I-24)
LPSTsub Branched alkyl chain acid; isopalmitic Jarchem
(2-hexyldecanoic acid) Acrylate LPSTsub Acrylate functionalized
carboxylic Synthesized functionalized acid in-house carboxylic acid
from 2- HEA + HHPA w/ DABCO catalyst
Synthesis of Liquid Hydrophobic Macromolecular Phase-Separating
Toughening Agents
[0152] Triblock copolymer "ABA" type hydrophobic macromolecular
phase separating toughening agents were generally synthesized from
hydrophobic center "B" blocks end-capped with polar and reactive
"A" blocks. To connect B with A, an anhydride small molecule was
used as linker. A typical synthetic procedure was as follows. To a
3-neck round bottom flask equipped with thermometer and mechanical
stirrer was added 1 equivalent (X moles) of the hydrophobic center
"B" oligomer block with --OH end group functionality. With gentle
stirring, 2 equivalents (2.times. moles) of a monoanhydride, i.e.
HHPA, was added along with 0.1 wt % of base catalyst (DABCO). This
mixture was heated typically to 80.degree. C. for several hours
(typically 2 hours, but as long as 4 hours to ensure complete
coupling of hydroxyl groups with anhydrides, forming carboxylic
acid end group functional oligomers). Next, to this same vessel was
added an excess of diepoxide end "A" block. Typical excess used was
5 equivalents (moles) of diepoxide monomer per 1 equivalent (mole)
of hydrophobic center block oligomer. Since the molecular weight of
the center block was in most cases much greater than the molecular
weight of the diepoxide end blocks, the actual mass excess of free
diepoxide after complete reaction was minimal. The acid+epoxy
coupling catalyst was also added at 0.1 wt %; typical catalyst used
was triphenylphosphine (TPP) but other catalysts such as the AMC-2
or other chromium catalysts are effective for this coupling
reaction as well. The mixture was then heated to 105.degree. C. for
5 to 6 hours with gentle stirring. At this time, a small aliquot of
sample was taken from the reaction and analyzed for acid value
(A.V.) using a Metrohm 751 GPD Titrino potentiometric titration
system. If A.V. was sufficiently low corresponding to >95%
consumption of carboxylic acid groups, the product was poured off
and stored. If not, reaction was continued and sampled periodically
for A.V. until reaction completion was obtained. A slightly
different synthesis was applied to the epoxy-functional ESO-based
toughening additives where the ESO comes equipped with epoxide
groups and so a direct reaction with carboxylic acids to
hydrophobicize the ESO) was performed (i.e. no use of HHPA as
linker). Various epoxidized pre-reacted hydrophobic macromolecules
synthesized accordingly and used in the examples are presented in
Table 2 below.
TABLE-US-00002 TABLE 2 Name Pre-reactants (Ratio by Equivalents)
Catalyst Functionalized PBD-based PBD (M.sub.n 2,800 g/mol) + HHPA
DABCO Celloxide 2021P Toughener A (1:2) PBD-based PBD (M.sub.n
2,800 g/mol) + HHPA DABCO Epon 828 Toughener B (1:2) PBD-based PBD
(M.sub.n 1,300 g/mol) + HHPA DABCO Celloxide 2021P Toughener C
(1:2) PBD-based PBD (M.sub.n 1,300 g/mol) + HHPA DABCO Epon 828
Toughener D (1:2) Pluronic-based Pluronic + HHPA (1:2) DABCO
Celloxide 2021P Toughener A Pluronic-based Pluronic + HHPA (1:2)
DABCO Epon 828 Toughener B PDMS-based PDMS + HHPA (1:2) DABCO
Celloxide 2021P Toughener A PDMS-based PDMS + HHPA (1:2) DABCO Epon
828 Toughener B ESO-based ESO + I-16 (1:2) Triphenyl- n/a Toughener
A phosphine ESO-based ESO + I-16 (1:3) Triphenyl- n/a Toughener B
phosphine ESO-based ESO + I-16 (1:3) Triphenyl- Acrylate Toughener
C phosphine w/carboxylic acid ESO-based ESO + I-16 (1:3) Chromium
n/a Toughener D ESO-based ESO + I-24 (1:3) Triphenyl- n/a Toughener
E phosphine
Examples 1-47
[0153] Various radiation curable compositions for additive
fabrication were prepared according to well-known methods in the
art, employing available base resin, along with one or more liquid
phase-separating toughening agents. The specific compositions are
reported in Table 3 below. These samples were then tested according
to the methods described below for evaluation of one or more of
Young's Modulus, Elongation at Break, HDT, Izod Notched Impact, and
viscosity. The results are presented in Table 3.
[0154] Examples 1-5 and 42-47 represent three-dimensional
components which were created in accordance with ASTM D638-10.
Examples 6-41 were used by evaluating draw-down strips, which were
created by the procedure described below.
[0155] All parts were washed with DOWANOL.TM. DPnB Glycol Ether,
followed by IPA, to remove excess resin. Parts were then dried
thoroughly with compressed air and UV post cured in a standard PCA
chamber. The PCA chamber consisted of a rotating turntable
surrounded by an alternating mix of Philips TLK 40W/05 and TLK
40W/03 lamps. Parts were post cured for 30 minutes per side, i.e.
one hour total. In most cases, to obtain high HDT, parts were then
thermally post cured (TPC) in an oven at 100.degree. C. for two
hours. Prior to testing, parts were then conditioned in a
controlled temperature humidity (TH) room (23.degree. C., 50% RH)
for at least 48 hours.
Draw-Down Strip Creation
[0156] A sheet of flexible Mylar PET (4 mil thick) was taped to the
top of a glass plate. Approximately 20 grams.+-.2 grams of resin
were poured onto the glass plate at one end spreading across the
width of the Mylar sheet. This resin sample was then drawn down to
a controlled thickness using a byko-drive Auto Applicator (BYK) and
a 10 mil drawdown bar. These thin resin layers were then placed on
top of a standard build platform loaded in a 3D Systems Viper SLA
machine. A 3D part file consisting of 4 ASTM D256 tensile bar
models was then loaded and one layer was imaged onto the thin draw
down resin layer. Ec was typically set to 15; Dp typically set to
5. After this layer finished, the build was stopped. The entire
glass plate, Mylar film, and resin layer (now with imaged tensile
bar strips fixed to the Mylar) were removed from the SLA machine.
Excess resin was gently wiped clean leaving the imaged tensile bars
strips. The entire glass plate, Mylar film, and imaged tensile bar
strips remaining were then UV post cured for 30 minutes. Following
UVPC, the tensile bar strips were gently removed by bending the
Mylar film and peeling the strips away. The strips were then turned
over and UV post cured for another 30 minutes. Typically, strips
were then thermally post cured using procedures used for thermally
post curing 3D parts in this work (i.e. 2 hours, 100.degree.
C.).
Measurement of Young's Modulus & Elongation at Break
[0157] Samples were tested in accordance with ASTM D638-10, except
as modified as described herein. Samples were built by a Viper SLA
machine (S/N 03FB0244 or S/N 02FB0160), manufactured by 3D Systems,
Inc., to the standard, art-recognized Type I "dogbone" shape with
an overall length of 6.5 inches, an overall width of 3/4 of an inch
(0.75 inches), and an overall thickness of 1/8 of an inch (0.125
inches). Samples were conditioned for 7 days at 23.degree. Celsius
at 50% relative humidity. The conditioning period exceeds the
minimum prescribed in the ASTM 618-13 standard to ensure maximum
stabilization in the cationic cure of the hybrid system. The
samples were measured and then placed in the Sintech tensile-tested
S/N using the 6500 N load cell S/N # with a 50% extensometer SN#.
The speed of testing was set at 5.1 mm/min with a nominal strain
rate of 0.1 mm/min at the start of test. The Young's modulus or
Modulus of Elasticity was calculated by extending the initial
linear portion of the load-extension curve and dividing the
difference in stress corresponding to any segment of the section on
this straight line by the corresponding difference in strain. All
elastic modulus values were computed using the average original
cross sectional area in the gage length segment of the specimen in
the calculations. The Percent Elongation at break was calculated by
reading the extension at point of specimen rapture and dividing
that extension by the original gage length and multiplying by 100.
Standard deviations were calculated according to known statistical
methods.
Measurement of Heat Deflection Temperature
[0158] Heat Deflection Temperature (HDT) is tested on parts built,
washed, and UV postcured, as previously described. Specimens are
numbered and allowed to condition at 23.degree. C., 50% relative
humidity for a period of not less than 48 hours. Part dimensions
and test method is as described in ASTM D648-00a Method B. Reported
HDT values are for an applied stress of 0.45 MPa (66 psi). Care was
taken to ensure that the test contacts for the HDT tester were in
contact with smooth surfaces of the polymer part. It has been found
that surface irregularities (i.e. non-smooth surfaces) can
contribute to a lower HDT than measuring a smooth part surface. Top
surfaces of HDT parts are typically smooth without alteration.
Sidewalls and bottom-facing surfaces were sanded with 100 grit
followed by 250 grit sandpaper to ensure a smooth testing surface
before measurement. Listed HDT data are for parts that have not
experienced thermal postcure.
Viscosity
[0159] The viscosity of each sample was taken with an Anton Paar
Rheoplus Rheometer (S/N 80325376) using a Z3/Q1 measuring cylinder
(S/N 10571) with a 25 mm diameter. The temperature was set at
30.degree. Celsius with a shear rate of 50 s.sup.-1. The rotational
speed was set at 38.5 min.sup.-1. The measuring container was a
H-Z3/SM cup (diameter 27.110 mm) which was filled with 21.4 grams
of sample (enough to the spindle). Measurements were recorded in
millipascal-seconds (mPas), but converted and reported herein as
centipoise (cPs).
Notched Izod Impact Strength
[0160] Izod impact tests of specimen were tested according to ASTM
D256A. Parts were built by a Viper SLA machine (S/N 03FB0244 or S/N
02FB0160) manufactured by 3D Systems, Inc. to the standing testing
size according to ASTM D256A. Specimen were conditioned for at
least 48 hours at 23.degree. Celsius at 50% relative humidity after
a thermal post-cure. The specimen were then notched with a
Qualitest saw. They were then tested on a Zwick/Roell HIT5.5P
instrument, using an Izod Hammer of 2.75 J. The average of at least
5 test specimens is reported.
TABLE-US-00003 TABLE 3 Component Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7
Ex 8 Ex 9 Ex 10 Somos LV Grey 100 0 0 0 0 0 0 0 0 0 Somos
Prototherm 0 0 0 0 0 100 100 100 100 100 Somos Protogen 0 100 100 0
0 0 0 0 0 0 Somos Modified NeXt 0 0 0 100 100 0 0 0 0 0 Formlabs
Clear 0 0 0 0 0 0 0 0 0 0 Acclaim 8200 0 0 5 0 5 0 0 0 0 0 Acclaim
4000 0 0 0 0 0 0 0 0 0 0 Beta Tough 2cr 14 0 0 0 0 0 0 0 0 0
PBD-based Toughener A 0 0 0 0 0 0 2 0 5 0 PBD-based Toughener B 0 0
0 0 0 0 0 2 0 5 PBD-based Toughener C 0 0 0 0 0 0 0 0 0 0 PBD-based
Toughener D 0 0 0 0 0 0 0 0 0 0 Pluronic-based Toughener A 0 0 0 0
0 0 0 0 0 0 Pluronic-based Toughener B 0 0 0 0 0 0 0 0 0 0
PDMS-based Toughener A 0 0 0 0 0 0 0 0 0 0 PDMS-based Toughener B 0
0 0 0 0 0 0 0 0 0 ESO-based Toughener A 0 0 0 0 0 0 0 0 0 0
ESO-based Toughener B 0 0 0 0 0 0 0 0 0 0 ESO-based Toughener C 0 0
0 0 0 0 0 0 0 0 ESO-based Toughener D 0 0 0 0 0 0 0 0 0 0 ESO-based
Toughener E 0 0 0 0 0 0 0 0 0 0 Elongation at Break (%) 21.3 6.5
12.4 9.4 23.0 2.3 2.6 2.9 2.2 2.5 Young's Modulus (MPa) 2410 2960
2410 3010 2250 3494 3276 3250 2960 3009 HDT (.degree. C.) n/a 97.6
100.8 55.5 52.7 127 125 122 127 114 Izod Impact (J/cm) 0.39 0.23
0.31 0.25 0.28 n/a n/a n/a n/a n/a Viscosity (cPs) 657 n/a n/a n/a
n/a n/a n/a n/a n/a n/a Component Ex 11 Ex 12 Ex 13 Ex 14 Ex 15 Ex
16 Ex 17 Ex 18 Ex 19 Ex 20 Somos LV Grey 0 0 0 0 0 0 0 0 0 0 Somos
Prototherm 100 100 100 100 100 100 100 100 100 100 Somos Protogen 0
0 0 0 0 0 0 0 0 0 Somos Modified NeXt 0 0 0 0 0 0 0 0 0 0 Formlabs
Clear 0 0 0 0 0 0 0 0 0 0 Acclaim 8200 0 0 0 0 0 0 0 0 0 0 Acclaim
4000 0 0 0 0 0 0 0 0 0 0 Beta Tough 2cr 0 0 0 0 0 0 0 0 0 0
PBD-based Toughener A 10 0 0 0 0 0 0 0 0 0 PBD-based Toughener B 0
10 0 0 0 0 0 0 0 0 PBD-based Toughener C 0 0 2 0 5 0 10 0 0 0
PBD-based Toughener D 0 0 0 2 0 5 0 10 0 0 Pluronic-based Toughener
A 0 0 0 0 0 0 0 0 2 0 Pluronic-based Toughener B 0 0 0 0 0 0 0 0 0
2 PDMS-based Toughener A 0 0 0 0 0 0 0 0 0 0 PDMS-based Toughener B
0 0 0 0 0 0 0 0 0 0 ESO-based Toughener A 0 0 0 0 0 0 0 0 0 0
ESO-based Toughener B 0 0 0 0 0 0 0 0 0 0 ESO-based Toughener C 0 0
0 0 0 0 0 0 0 0 ESO-based Toughener D 0 0 0 0 0 0 0 0 0 0 ESO-based
Toughener E 0 0 0 0 0 0 0 0 0 0 Elongation at Break (%) 1.5 2.4 2.6
2.6 3.1 3.1 3.0 3.0 2.7 3.2 Young's Modulus (MPa) 2111 2868 3182
3255 2990 2858 3242 2880 3221 2826 HDT (.degree. C.) 125 92 129 124
121 109 122 94 128 117 Izod Impact (J/cm) n/a n/a n/a n/a n/a n/a
n/a n/a n/a n/a Viscosity (cPs) n/a n/a n/a n/a n/a n/a n/a n/a n/a
n/a Component Ex 21 Ex 22 Ex 23 Ex 24 Ex 25 Ex 26 Ex 27 Ex 28 Ex 29
Ex 30 Somos LV Grey 0 0 0 0 0 0 0 0 0 0 Somos Prototherm 100 100
100 100 100 100 100 100 100 100 Somos Protogen 0 0 0 0 0 0 0 0 0 0
Somos Modified NeXt 0 0 0 0 0 0 0 0 0 0 Formlabs Clear 0 0 0 0 0 0
0 0 0 0 Acclaim 8200 0 0 0 0 0 0 0 0 0 0 Acclaim 4000 0 0 0 0 0 0 0
0 0 0 Beta Tough 2cr 0 0 0 0 0 0 0 0 0 0 PBD-based Toughener A 0 0
0 0 0 0 0 0 0 0 PBD-based Toughener B 0 0 0 0 0 0 0 0 0 0 PBD-based
Toughener C 0 0 0 0 0 0 0 0 0 0 PBD-based Toughener D 0 0 0 0 0 0 0
0 0 0 Pluronic-based Toughener A 5 0 10 0 0 0 0 0 0 0
Pluronic-based Toughener B 0 5 0 10 0 0 0 0 0 0 PDMS-based
Toughener A 0 0 0 0 2 0 5 0 10 0 PDMS-based Toughener B 0 0 0 0 0 2
0 5 0 10 ESO-based Toughener A 0 0 0 0 0 0 0 0 0 0 ESO-based
Toughener B 0 0 0 0 0 0 0 0 0 0 ESO-based Toughener C 0 0 0 0 0 0 0
0 0 0 ESO-based Toughener D 0 0 0 0 0 0 0 0 0 0 ESO-based Toughener
E 0 0 0 0 0 0 0 0 0 0 Elongation at Break (%) 2.2 1.9 2.3 1.3 2.7
3.2 2.2 1.9 2.3 1.3 Young's Modulus (MPa) 3286 2985 2990 2864 3221
2826 3286 2985 2990 2864 HDT (.degree. C.) 128 114 124 110 128 117
128 114 124 110 Izod Impact (J/cm) n/a n/a n/a n/a n/a n/a n/a n/a
n/a n/a Viscosity (cPs) n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a
Component Ex 31 Ex 32 Ex 33 Ex 34 Ex 35 Ex 36 Ex 37 Ex 38 Ex 39 Ex
40 Somos LV Grey 0 0 0 0 0 0 0 0 0 0 Somos Prototherm 100 100 100
100 100 100 0 0 0 0 Somos Protogen 0 0 0 0 0 0 0 0 0 0 Somos NeXt 0
0 0 0 0 0 100 0 0 0 Somos Modified NeXt 0 0 0 0 0 0 0 100 100 0
Formlabs Clear 0 0 0 0 0 0 0 0 0 100 Acclaim 8200 0 0 0 0 0 0 0 0 0
0 Acclaim 4000 0 0 0 0 0 0 0 0 0 0 Beta Tough 2cr 0 0 0 0 0 0 0 0 0
0 PBD-based Toughener A 0 0 0 0 0 0 0 0 0 0 PBD-based Toughener B 0
0 0 0 0 0 0 0 0 0 PBD-based Toughener C 0 0 0 0 0 0 0 0 0 0
PBD-based Toughener D 0 0 0 0 0 0 0 0 0 0 Pluronic-based Toughener
A 0 0 0 0 0 0 0 0 0 0 Pluronic-based Toughener B 0 0 0 0 0 0 0 0 0
0 PDMS-based Toughener A 0 0 0 0 0 0 0 0 0 0 PDMS-based Toughener B
0 0 0 0 0 0 0 0 0 0 ESO-based Toughener A 2 0 5 0 10 0 0 0 0 0
ESO-based Toughener B 0 2 0 5 0 10 0 5 2 0 ESO-based Toughener C 0
0 0 0 0 0 0 0 0 0 ESO-based Toughener D 0 0 0 0 0 0 0 0 0 0
ESO-based Toughener E 0 0 0 0 0 0 0 0 0 0 Elongation at Break (%)
2.6 3.6 3.1 3.7 3.2 3.5 2.8 3.0 2.9 7.2 Young's Modulus (MPa) 2971
2926 2600 2821 2358 2511 2936 2615 2570 2519 HDT (.degree. C.) 128
122 126 121 117 115 n/a n/a n/a 76 Izod Impact (J/cm) n/a n/a n/a
n/a n/a n/a n/a n/a n/a 0.19 Viscosity (cPs) n/a n/a n/a n/a n/a
n/a n/a n/a n/a n/a Component Ex 41 Ex 42 Ex 43 Ex 44 Ex 45 Ex 46
Ex 47 Ex 48 Ex 49 Ex 50 Somos LV Grey 0 0 0 0 0 0 0 Somos
Prototherm 0 0 0 0 0 0 0 Somos Protogen 0 100 100 100 100 100 100
Somos NeXt 0 0 0 0 0 0 0 Somos Modified NeXt 0 0 0 0 0 0 0 Formlabs
Clear 100 0 0 0 0 0 0 Acclaim 8200 0 0 0 0 0 0 0 Acclaim 4000 0 0 0
0 0 0 0 Beta Tough 2cr 0 0 0 0 0 0 0 PBD-based Toughener A 0 0 0 0
0 0 0 PBD-based Toughener B 0 0 0 0 0 0 0 PBD-based Toughener C 0 0
0 0 0 0 0 PBD-based Toughener D 0 0 0 0 0 0 0 Pluronic-based
Toughener A 0 0 0 0 0 0 0 Pluronic-based Toughener B 0 0 0 0 0 0 0
PDMS-based Toughener A 0 0 0 0 0 0 0 PDMS-based Toughener B 0 0 0 0
0 0 0 ESO-based Toughener A 0 0 0 0 0 0 0 ESO-based Toughener B 0 0
5 3 10 0 0 ESO-based Toughener C 5 0 0 0 0 0 0 ESO-based Toughener
D 0 0 0 0 0 5 0 ESO-based Toughener E 0 0 0 0 0 0 5 Elongation at
Break (%) 10.6 7.1 17.7 8.9 10.2 8.7 13.9 Young's Modulus (MPa)
2338 2838 2435 2786 2029 2386 2206 HDT (.degree. C.) 71 95 94 n/a
n/a n/a n/a Izod Impact (J/cm) 0.26 .28 .31 n/a n/a n/a n/a
Viscosity (cPs) n/a n/a n/a n/a n/a n/a n/a
Additional Exemplary Embodiments
[0161] A first aspect of a first additional exemplary embodiment of
the invention is a radiation curable composition for additive
fabrication with improved toughness comprising: [0162] a rubber
toughenable base resin further comprising [0163] a cationically
polymerizable component; [0164] a radically polymerizable
component; [0165] a cationic photoinitiator; [0166] a free radical
photoinitiator; and [0167] optionally, customary additives; and
[0168] a liquid phase-separating toughening agent;
[0169] wherein the liquid phase-separating toughening agent is
present in an amount, relative to the weight of the rubber
toughenable base resin, in a ratio from about 1:99 to about 1:3,
more preferably about 1:99 to about 1:4, more preferably about 1:99
to about 1:9, more preferably about 1:50 to about 1:12, more
preferably about 1:19; and wherein the average molecular weight
between crosslinks (M.sub.C) of the rubber toughenable base resin
is greater than 130 g/mol, more preferably greater than 150 g/mol;
in another embodiment more preferably greater than 160 g/mol; and
in another embodiment greater than 180 g/mol.
[0170] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein the liquid phase-separating toughening agent is a high
molecular weight dimer fatty acid polyol.
[0171] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein the high molecular weight polyol is selected to be
configured to form, after curing of the radiation curable
composition, phase domains with an average size of from about 2
microns to about 25 microns, or from about 5 microns to about 20
microns, or from about 7 microns to about 15 microns, when measured
according to an Average Phase Domain Size Procedure.
[0172] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein the high molecular weight dimer fatty acid polyol possesses
a molecular weight of greater than 2000 g/mol, more preferably 3000
g/mol, more preferably greater than 8000 g/mol.
[0173] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein the high molecular weight dimer fatty acid polyol is a
propylene oxide or ethylene oxide.
[0174] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein M.sub.C of the rubber toughenable base resin is less than
500 g/mol, more preferably less than 400 g/mol, more preferably
less than 300 g/mol, more preferably less than 280 g/mol, more
preferably less than 260 g/mol, more preferably less than 230
g/mol, less than 200 g/mol.
[0175] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein a three-dimensional component created therefrom by means of
an additive fabrication process yields an elongation value that is
at least 20% greater, more preferably at least 50% greater, more
preferably 100% greater than a corresponding elongation value of a
three dimensional component created from the constituent rubber
toughenable base resin of said radiation curable composition.
[0176] An additional aspect of the first additional exemplary
embodiment is a radiation curable composition for additive
fabrication with improved toughness according to any of the
previous aspects of the first additional exemplary embodiment,
wherein a three-dimensional component created therefrom by means of
an additive fabrication process yields an HDT value that is within
at least 5 degrees, more preferably within at least 3 degrees, more
preferably within at least 1 degree Celsius of a corresponding
elongation value of a three dimensional component created from the
constituent rubber toughenable base resin of said radiation curable
composition.
[0177] A first aspect of a second additional exemplary embodiment
is a radiation curable composition for additive fabrication with
improved toughness comprising: [0178] a rubber toughenable base
resin further comprising [0179] (1) optionally, a cationically
polymerizable component; [0180] (2) a radically polymerizable
component; [0181] (3) optionally, a cationic photoinitiator; [0182]
(4) a free radical photoinitiator; and [0183] (5) optionally,
customary additives; and [0184] a liquid phase-separating
toughening agent; [0185] wherein the liquid phase-separating
toughening agent is an epoxidized pre-reacted hydrophobic
macromolecule.
[0186] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the average molecular
weight between crosslinks (M.sub.C) of the rubber toughenable base
resin is greater than 130 g/mol, more preferably greater than 150
g/mol; in another embodiment more preferably greater than 160
g/mol; and in another embodiment greater than 180 g/mol; [0187]
wherein the M.sub.C of the rubber toughenable base resin is less
than 500 g/mol, more preferably less than 400 g/mol, more
preferably less than 300 g/mol, more preferably less than 280
g/mol, more preferably less than 260 g/mol, more preferably less
than 230 g/mol, less than 200 g/mol.
[0188] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the rubber toughenable
base resin further contains less than 50%, more preferably less
than 40%, more preferably less than 30% by weight, relative to the
entire weight of the rubber toughenable base resin, of an aromatic
glycidyl epoxy.
[0189] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the glycidyl epoxy is a
bisphenol A diglycidyl ether.
[0190] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the rubber toughenable
base resin further comprises a polyol component.
[0191] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the polyol component is
present in an amount, relative to the entire weight of the rubber
toughenable base resin, of at least about 3%, more preferably at
least 5%, more preferably 10%.
[0192] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is a triblock copolymer possessing [0193]
terminating epoxy- or acrylate-functional hard blocks; and [0194]
at least one immiscible soft block.
[0195] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the triblock copolymer is
formed by the reaction product of a soft-block originator with a
monofunctional anhydride such as hexahydrophthalic anhydride, and
then further reacting an epoxy-functional reactant.
[0196] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the soft-block originator
is selected from the group consisting of polybutadienes, polyols,
and polydmethylsiloxanes, and any combination thereof.
[0197] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the polyols are selected
from the group consisting of polyethylene oxide and polypropylene
oxide.
[0198] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxy-functional
reactant is selected from the group consisting of
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate,
2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)-cyclohexane-1,4-dioxane,
bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide,
4-vinylepoxycyclohexane, vinylcyclohexene dioxide,
bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,
3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate,
.epsilon.-caprolactone-modified
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylates,
trimethylcaprolactone-modified
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylates,
.beta.-methyl-.delta.-valerolactone-modified
3,4-epoxycyclohexcylmethyl-3',4'-epoxycyclohexane carboxylates,
methylenebis(3,4-epoxycyclohexane), bicyclohexyl-3,3'-epoxide,
bis(3,4-epoxycyclohexyl) with a linkage of --O--, --S--, --SO--,
--SO.sub.2--, --C(CH.sub.3).sub.2--, --CBr.sub.2--,
--C(CBr.sub.3).sub.2--, --C(CF.sub.3).sub.2--,
--C(CCl.sub.3).sub.2--, or --CH(C.sub.6H.sub.5)--,
dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl) ether of
ethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate), and
epoxyhexahydrodioctylphthalate.
[0199] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from a triglyceride fatty
acid.
[0200] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from a tall oil.
[0201] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized tall oil is
an epoxidized vegetable oil, such as soybean or linseed oil.
[0202] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from a compound of the
following formula:
##STR00003## [0203] wherein R.sub.1, R.sub.2, and R.sub.3 are the
same or different, and are each a C.sub.4-C.sub.50 unsaturated
alkyl chain, wherein the unsaturation has been at least 10%
epoxidized, more preferably 30% epoxidized.
[0204] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is derived from the following
compound:
##STR00004##
[0205] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is the reaction product of an epoxidized
soybean oil (ESO) and an alkyl chain carboxylic acid, thereby
forming an ESO-based globular toughener.
[0206] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is synthesized in the presence of a
catalyst.
[0207] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the catalyst is selected
from the group consisting of triphenylphosphine, chromium, or DABCO
catalysts.
[0208] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the alkyl chain carboxylic
acid is liquid at room temperature.
[0209] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is synthesized by reacting, in terms of
equivalents, a ratio of the ESO to the alkyl chain carboxylic acid
from about 2:3 to about 2:7, more preferably from about 1:2 to
about 1:3.
[0210] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the alkyl chain carboxylic
acid is selected from the group consisting of isopalmitic acid,
2-hexyl decanoic acid, and compounds of the following
structure:
##STR00005##
[0211] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the alkyl chain carboxylic
acid possesses the following structure:
##STR00006##
[0212] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule possesses the following structure:
##STR00007##
[0213] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule possesses a molecular weight of from
about 800 g/mol to about 4000 g/mol, more preferably from about
1000 g/mol to about 2500 g/mol, more preferably from about 1500
g/mol to about 2000 g/mol.
[0214] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is further acrylate functionalized.
[0215] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the wherein epoxidized
pre-reacted hydrophobic macromolecule that is further acrylate
functionalized possesses the following structure:
##STR00008##
[0216] An additional aspect of the second additional exemplary
embodiment is a radiation curable composition for additive
fabrication according to any of the previous aspects of the second
additional exemplary embodiment, wherein the epoxidized pre-reacted
hydrophobic macromolecule is present, relative to the weight of the
entire composition, in an amount from about 1% to about 20%, more
preferably from about 1.5% to about 12%, more preferably from about
2% to about 10%, more preferably about 5%.
[0217] A first aspect of a third additional exemplary embodiment is
a process of forming a three-dimensional object comprising the
steps of forming and selectively curing a liquid layer of the
radiation curable composition for additive fabrication with
improved toughness of any of the aspects of either of the first or
second additional exemplary embodiments of the invention with
actinic radiation and repeating the steps of forming and
selectively curing the liquid layer of the radiation curable
composition for additive fabrication a plurality of times to obtain
a three-dimensional object.
[0218] An additional aspect of the third additional exemplary
embodiment is the three-dimensional object formed by the process of
the first aspect of the third additional exemplary embodiment from
the radiation curable composition for additive fabrication with
improved toughness of any the aspects of either the first or second
additional exemplary embodiments of the invention.
[0219] An additional aspect of the third additional exemplary
embodiment is the three-dimensional object of the previous aspect
of the third additional exemplary embodiment wherein the elongation
value is at least 5%, more preferably at least 10%, more preferably
at least 20%, more preferably at least 50%, and/or the HDT value is
at least 75, more preferably at least 85, more preferably at least
95 degrees Celsius.
[0220] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0221] Preferred embodiments of this invention are described
herein, including the best mode known to the inventor for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventor expects skilled artisans to
employ such variations as appropriate, and the inventor intends for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
While the invention has been described in detail and with reference
to specific embodiments thereof, it will be apparent to one of
ordinary skill in the art that various changes and modifications
can be made therein without departing from the spirit and scope of
the claimed invention.
* * * * *