U.S. patent application number 11/650453 was filed with the patent office on 2007-07-05 for radiation curable resin composition and rapid prototyping process using the same.
This patent application is currently assigned to DSM IP Assets B.V.. Invention is credited to Aylvin J.A.A. Dias, John A. Lawton, Jens C. Thies, David L. Winmill, Jigeng Xu, Xiaorong You.
Application Number | 20070154840 11/650453 |
Document ID | / |
Family ID | 29401462 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070154840 |
Kind Code |
A1 |
Thies; Jens C. ; et
al. |
July 5, 2007 |
Radiation curable resin composition and rapid prototyping process
using the same
Abstract
The invention relates to a radiation curable composition
comprising relative to the total weight of the composition (A) 0-29
wt % of a cationically curable component having a linking aliphatic
ester group, (B) 10-85 wt % of an epoxygroup containing component
other than A, (C) 1-50 wt % of an oxetanegroup containing
component, (D) 1-25 wt % of a multifunctional acrylate and a
radical photoinitiator and a cationic photoinitiator.
Inventors: |
Thies; Jens C.; (Maastricht,
NL) ; Dias; Aylvin J.A.A.; (Maastricht, NL) ;
Lawton; John A.; (Landenberg, PA) ; Winmill; David
L.; (Newark, DE) ; Xu; Jigeng; (Boothwyn,
PA) ; You; Xiaorong; (Bear, DE) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DSM IP Assets B.V.
Heerlen
NL
|
Family ID: |
29401462 |
Appl. No.: |
11/650453 |
Filed: |
January 8, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10623153 |
Jul 21, 2003 |
7183040 |
|
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11650453 |
Jan 8, 2007 |
|
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PCT/NL03/00320 |
May 1, 2003 |
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10623153 |
Jul 21, 2003 |
|
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60377239 |
May 3, 2002 |
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Current U.S.
Class: |
430/270.1 |
Current CPC
Class: |
C08F 283/06 20130101;
G03F 7/027 20130101; B29C 64/106 20170801; C08F 290/06 20130101;
C08F 283/10 20130101; B33Y 70/00 20141201; G03F 7/0037 20130101;
G03F 7/038 20130101; C08G 65/18 20130101; C08G 59/68 20130101; B33Y
10/00 20141201 |
Class at
Publication: |
430/270.1 |
International
Class: |
G03C 1/00 20060101
G03C001/00 |
Claims
1-15. (canceled)
16. The radiation curable composition comprising, relative to the
total weight of the composition, 1-29 wt. % of an oxetane compound,
10-85 wt. % of a glcidycl ether, 1-25 wt. % of a multifunctional
acrylate compound, a radical photoinitiator and a cationic
photoinititor.
17-23. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This Application is a continuation of International
Application PCT/NL03/00320, filed May 1, 2003, which claims the
benefit of U.S. Provisional Application 60/377,239, filed May 3,
2002. Both these prior applications are hereby incorporated in
their entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to radiation curable
compositions which are particularly suitable for the production of
three-dimensional shaped articles by means of stereolithography, to
a process for the production of a cured product and, in particular,
for the stereolithographic production of a three dimensional shaped
articles from this composition having excellent moisture
resistance.
BACKGROUND OF THE INVENTION
[0003] The production of three-dimensional articles of complex
shape by means of stereolithography has been known for a number of
years. In this technique the desired shaped article is built up
from a radiation-curable composition with the aid of a recurring,
alternating sequence of two steps (a) and (b). In step (a), a layer
of the radiation-curable composition, one boundary of which is the
surface of the composition, is cured with the aid of appropriate
imaging radiation, preferably imaging radiation from a
computer-controlled scanning laser beam, within a surface region
which corresponds to the desired cross-sectional area of the shaped
article to be formed, and in step (b) the cured layer is covered
with a new layer of the radiation-curable composition, and the
sequence of steps (a) and (b) is repeated until a so-called green
model of the desired shape is finished. This green model is, in
general, not yet fully cured and may therefore be subjected to
post-curing, though such post curing is not required.
[0004] Via an equivalent process, photopolymer can be jetted by ink
jet or multiple ink jet processes in an imagewise fashion. While
jetting the photopolymer or after the photopolymer is applied
actinic exposure can be provided to initiate polymerization.
Multiple materials (for example non-reactive waxes, weakly reacting
photopolymers, photopolymers of various physical properties,
photopolymers with various colors or color formers, etc.) can be
jetted or applied to provide supports or alternate cured
properties.
[0005] The mechanical strength of the green model (modulus of
elasticity, fracture strength), also referred to as green strength,
constitutes an important property of the green model and is
determined essentially by the nature of the
stereolithographic-resin composition employed in combination with
the type of stereolithography apparatus used and degree of exposure
provided during part fabrication. Other important properties of a
stereolithographic-resin composition 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. In addition, for example, it should be
relatively easy to coat a new layer of the stereolithographic resin
composition during the process. And of course, not only the green
model but also the final cured article should have optimum
mechanical properties.
[0006] The developments in this area of technology move towards
compositions having better mechanical properties in order to better
simulate properties of commodity materials like polypropylene and
engineering type polymers. Also there exists a requirement for
faster cure and process speeds, so as to decrease the time to built
a part. This has resulted in new stereolithography machines having
solid state lasers that have a high energy output, very fast
laser-scanning and faster recoating processes. The new machines
supply UV light with a power around 800 mW and above, compared to
200-300 mW for the older conventional machines. Also the scanning
time is reduced by 3 to 4 times. These high powers, high scanning
speeds, and short recoating times result in higher temperatures,
due to polymerization exotherm of the resins and parts during
fabrication. Typical temperatures have risen to values between 50
and 90.degree. C., which leads to part distortion and excessive
color development.
[0007] The developments have resulted in compositions having a
substantial amount of
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, together
with other components like polyols, acrylates and glycidylethers.
Examples of such compositions can be found in for example U.S. Pat.
No. 5,476,748. A disadvantage of such compositions is that cured
parts show poor mechanical properties, when subjected to high
humidity environments or when they are soaked in water for longer
periods of time.
[0008] JP Hei 11-199647 shows examples of hybrid compositions,
containing oxetanes, 38-50 wt %
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and more
than 35 wt % of acrylates. These compositions have the disadvantage
that the green model parts show unacceptable high distortion when
made in a high power solid state stereolithography apparatus,
whereby the parts also are very sensitive to water or high
humidity.
OBJECTS OF THE INVENTION
[0009] It is an object of the present invention to provide resin
compositions that after full cure show improved resistance to
moisture or humidity.
[0010] It is another objective to provide objects made from resin
compositions that substantially keep their mechanical properties
when subjected to water or high humidity conditions for a long
time.
[0011] It is also an object of the invention to provide resin
compositions that can be easily used in solid state laser
stereolithography machines.
[0012] It is a further objective of the invention to provide resin
compositions that show excellent mechanical properties (such as
modulus, izod and flexibility) and low curl behavior when cured in
a stereolithography machine.
SUMMARY OF THE INVENTION
[0013] The present invention relates to a radiation curable
composition comprising [0014] A 0-29 wt % of a cationically curable
component having a linking aliphatic ester group [0015] B 10-85 wt
% of an epoxygroup containing component other than A [0016] C 1-50
wt % of an oxetanegroup containing component [0017] D 1-25 wt % of
a multifunctional acrylate [0018] E a radical photoinitiator [0019]
F a cationic photoinitiator
[0020] A cationically curable component having a linking aliphatic
ester group is a component having at least two cationically curable
functional groups and one ester group, which ester group is located
between two cationically curable functional groups and is coupled
at both sides to aliphatic carbon atoms. The at least two
cationically curable functional groups may be the same or
different. Examples of cationically curable functional groups are
epoxy, oxetane and hydroxy groups.
[0021] A preferred embodiment of the present invention involves a
radiation curable composition comprising relative to the total of
the composition [0022] A 0-25 wt % of a component having a linking
estergroup and two cyclohexeneoxide groups [0023] B 10-80 wt % of
an epoxygroup containing component other than A [0024] C 1-50 wt %
of an oxetanegroup containing component [0025] D. 1-25 wt % of a
multifunctional acrylate [0026] E 0,1-10 wt % of a radical
photoinitiator [0027] F 0,1-10 wt % of a cationic photoinitiator
wherein a photo-fabricated article, obtained by repeating the steps
of forming a layer of the composition and selectively irradiating
the layer of the composition with actinic radiation, followed by
postcure during 60 minutes in a postcure apparatus and subsequent
conditioning of the article during 48 hours at a temperature of
20.degree. C. and a relative humidity of 80% RH, has at least one
of the following properties [0028] (i) a flexural modulus in the
range of 500 to 10000 MPa; [0029] (ii) an average elongation at
break of at least 3%; and/or [0030] (iii) a tensile strenght of at
least 25 MPa
[0031] A different embodiment of the present invention relates to a
radiation curable composition, comprising an oxetane, a
glycidylether, a cationic photoinitiator, wherein the composition
is cured to a flexural bar having the approximate dimensions of 5.5
mm thickness, a width of 12.5 mm and a length of 150 mm, with
actinic radiation and 60 min UV postcure and wherein the object has
a ratio of Fwet/Fdry>0.5, wherein Fdry is the Flexural Modulus
of the flexural bar after cure and Fwet is the Flexural Modulus of
a flexural bar after cure and a water treatment, wherein the object
is submersed in water of 20.degree. C. during 48 hours.
[0032] In a further embodiment, the present invention features a
radiation curable composition, comprising an oxetane, a
glycidylether, a cationic photoinitiator, wherein the composition
after cure with actinic radiation and 60 min UV postcure shows the
following properties: [0033] (i) a water absorption of less than 1
wt % after conditioning of a part, having a length of 15 cm, a
height of 0.55 cm and a width of 1.25 cm during 48 hours and a
temperature of 20.degree. C. at a relative humidity of 80% [0034]
(ii) a flexural modulus in the range of 500 to 10000 MPa; and
[0035] (iii) an average elongation at break of at least 3%.
[0036] Preferably the radiation curable composition comprises an
oxetane, a glycidylether, a cationic photoinitiator, 0-20 wt % of
cationically curable components having a linking aliphatic ester
group, wherein the composition after full cure by actinic radiation
and 60 min UV postcure has at least one of the following properties
[0037] (i) a flexural modulus in the range of 1000 to 10000 MPa;
[0038] (ii) an average elongation at break of at least 4%; and
[0039] (iii) a tensile strength of at least 25 Mpa.
[0040] The present invention also provides processes, e.g. a rapid
prototyping process, for curing the present compositions. In
addition, the present invention provides objects, e.g. three
dimensional objects, obtained by such processes.
DETAILED DESCRIPTION OF THE INVENTION
[0041] While not wishing to be limited by any particular theory, it
is believed that the presence of high amounts of components, that
have linking aliphatic ester groups in the molecule, that form
chemical bridges in the object after cure of the compositions, may
be unfavorable for the moisture (i.e. water) resistance of the
objects. Such aliphatic ester groups are believed to be
hydrolytically unstable in the presence of acids and may cause loss
of mechanical properties after being subjected to water or high
humidity conditions for longer periods of time and/or at higher
temperatures. Accordingly, the present invention relates to
radiation curable compositions that comprise a limited amount of
cationically curable components having such linking aliphatic ester
groups.
(A) Cationically Polymerizable Component
[0042] The present invention comprises at least one epoxide-group
containing compound as a cationically polymerizable component
[0043] Epoxide-containing materials, also referred to as epoxy
materials, are cationically curable, by which is meant that
polymerization and/or crosslinking and other reactions of the epoxy
group can be initiated by cations. These materials may be monomers,
oligomers or polymers and are sometimes referred to as "resins."
Such materials may have an aliphatic, aromatic, cycloaliphatic,
arylaliphatic or heterocyclic structure. They can comprise epoxide
groups as side groups or groups that form part of an alicyclic or
heterocyclic ring system. Epoxy resins of those types include those
that are generally known and are commercially available.
[0044] The composition may contain one or more epoxy resins.
Preferably, the composition will comprise at least one liquid (at
room temperature, 23.degree. C.) component such that the
combination of materials is a liquid. Thus, the epoxide-containing
material is preferably a single liquid epoxy material, a
combination of liquid epoxy materials, or a combination of liquid
epoxy material(s) and solid epoxy material(s) which is soluble in
the liquid. However, in certain other preferred embodiments, e.g.
in embodiments where the epoxide material is soluble in other
components of the composition, the epoxide material may be
comprised only of materials that are solid at room temperature.
Also, when solid compositions are used, the compositions may be
melted prior to or during use. It is also possible to use shear
thinning compositions, that show a relatively high viscosity in the
absence of shear but show a much lower viscosity during and
(shortly after) shear.
[0045] The amount of epoxy group containing components that have
linking aliphatic ester groups preferably is below 25 wt % of the
total weight of the composition. Preferably the amount of epoxy
group containing components that have linking aliphatic ester
groups is below 20 wt %, more preferably below 15 wt % of the total
composition.
[0046] In one embodiment, the amount of cationically curable
compounds having ester linking groups may be described in terms of
equivalents or milliequivalents ester groups per 100 grams of total
composition. The ester milliequivalent of a component is calculated
with the formula: ester .times. .times. milliequivalents .times.
.times. of .times. .times. a .times. .times. component .times.
.times. Z = Wt .times. .times. % * 1000 N * Mwt ##EQU1## wherein wt
%=wt % of the component Z relative to the total composition,
N=Number of linking ester groups of the component Z and Mwt is
molecular weight of component Z.
[0047] The ester milliequivalents of the total composition is
calculated by adding up the individual milliequivalent values of
the cationically curable components that have linking
estergroups.
[0048] The milliequivalent linking ester groups in the composition
is preferably below 100 meq of ester links/100 g of composition.
More preferably the amount of linking ester groups is below 50
meq/100 g composition. Most preferably (in view of hydrolytic
stability) the amount of linking ester groups is below 25 meq/100 g
composition.
[0049] For further improved hydrolytic stability of the part, it is
preferred that the compositions do not have cationically curable
compounds having linking aliphatic
[0050] Suitable (component B) epoxy materials also include
poly(N-glycidyl) compounds, which are, for example, obtainable by
dehydrochlorination of the reaction products of epichlorohydrin
with amines that comprise at least two amine hydrogen atoms, such
as, for example, n-butylamine, aniline, toluidine, m-xylylene
diamine, bis(4-aminophenyl)methane or
bis(4-methylaminophenyl)methane. Suitable poly(N-glycidyl)
compounds also include N,N'-diglycidyl derivatives of
cycloalkyleneureas, such as ethyleneurea or 1,3-propyleneurea, and
N,N'-diglycidyl derivatives of hydantoins, such as of
5,5-dimethylhydantoin.
[0051] Examples of suitable (component B) epoxy materials include
poly(S-glycidyl) compounds which are di-S-glycidyl derivatives
which are derived from dithiols, such as, for example,
ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.
[0052] Preferred component B epoxies are glycidyl epoxides of
saturated and unsaturated bisphenol A, F, and S including
alkoxylated bisphenol A, F, and S, triol extended bisphenols, and
brominated bisphenols; glycidyl ethers of C2-C30 alkyls; 1,2
epoxies of C3-C30 alkyls such as tetradecane oxide; glycidyl ethers
of phenols and phenols with pendant groups and chains; mono and
multi glycidyl ethers of alcohols and polyols such as
1,4-butanediol, neopentyl glycol, cyclohexane dimethanol, dibromo
neopentyl glycol, trimethylol propane, poly-THF, polyethylene
oxide, polypropylene oxide, glycerol, and alkoxylated alcohols and
polyols. Also preferred are epoxidized phenolic, cresolic, and
bisphenol-based novolacs, as well as dicyclopentadiene backbone
phenol glycidyl ethers and tris(hydroxyphenyl) methane-based
epoxies. Other examples of preferred epoxides are ortho-glycidyl
phenyl glycidyl ether, diglycidyl ether of resorcinol, triglycidyl
ether of phloroglucinol and substituted phloroglucinols,
2,6-(2,3-epoxypropyl) phenylglycidyl ether, diglycidyl ether of
bisphenol-hexafluoroacetone, diglycidyl ether of
2,2-bis(4-hydroxyphenyl)nonadecane, 4,4-bis(2,3-epoxypropyl)phenyl
ether, diglycidyl ether of tetrachlorobisphenol A, diglycidyl ether
of tetrabromobisphenol A, triglycidyl ether of trihydroxybiphenyl,
tetraglycidoxy biphenyl, tetraglycidyl ether of bisresorcinol F,
tetraglycidyl ether of resorcinol ketone,
3,9-bis[2-(2,3-epoxypropoxy)phenylethyl]-2,4,8,10-tetraoxaspiro[5,5]undec-
ane, triglycidoxy-1,1,3-triphenylpropane, tetraglycidoxy
tetraphenylethane,
1,3-bis[3-(2,3-epoxypropoxy)propyl]tetramethyldisiloxane,
polyepichlorohydrin di(2,3-epoxypropyl)ether, polyallyl glycidyl
ether, epoxidized cyclic silanes such as
2,4,6,8,10-pentakis[3-(2,3-epoxypropoxy)propyl]-2,4,6,8,10-pentamethylcyc-
lopentasiloxane, diglycidyl ether of chlorendic diol, diglycidyl
ether of dioxanediol, diglycidyl ether of endomethylene
cyclohexanediol, 2,2-bis[4-2,3-epoxypropyl)cyclohexyl]propane,
1,1,1-tris(para-hydroxyphenyl)ethane glycidyl ether, and
2,2-(4-[3-chloro-2-(2,3-epoxypropoxy)propoxyl]cyclohexyl)propane.
[0053] Examples of preferred component B cycloaliphatic epoxides
are vinylcyclohexene dioxide, limonene oxide and dioxide,
2,2-bis(3,4-epoxycyclohexyl)propane,
Bis(2,3-epoxycyclopentyl)ether,
ethanedioldi(3,4-epoxycyclohexylmethyl) ether, dicyclopentadiene
dioxide, 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanoindane,
para-(2,3-epoxy)cyclopentylphenyl-2,3-epoxypropyl ether,
epoxydicyclopentenylphenyl glycidyl ether,
ortho-epoxycyclopentenylphenylglycidyl ether, bisepoxydicyclopentyl
ether of ethylene glycol, and
2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)-cyclohexane-meta-dioxane.
[0054] The epoxy materials can have molecular weights that vary
over a wide range. In general, the epoxy equivalent weight, i.e.,
the number average molecular weight divided by the number of
reactive epoxy groups, is preferably in the range of 60 to
1000.
[0055] Preferably the compositions of the present invention have a
weight ratio of glycidylethers to epoxy group containing components
that have linking aliphatic ester groups of larger than 1,
preferably larger than 1.5, more preferably larger than 2.
[0056] The compositions of the present invention preferably contain
10-85 wt % glycidylether compounds, more preferably between 20 and
80 wt %, most preferably between 30 and 75 wt %, relative to the
total of the composition.
(C) Oxetane Group Containing Component
[0057] Preferably the compositions of the present invention contain
oxetanes. The presence of oxetanes in combination with
glycidylethers enhances the cure speed of the compositions relative
to compositions having only glycidylethers but no oxetanes.
Therefore the resin compositions of the present invention may be
advantageously employed in high powered stereolithography machines
having solid state lasers. Also, the presence of oxetanes improves
the flexibility of the objects made from the composition.
Furthermore it has been surprisingly found that the presence of
oxetanes gives a higher accuracy of object formation, less curling
and deformation during the build of the part. It has also been
unexpectedly found that the greenstrength of the parts increases
significantly when oxetanes are present in the composition in
ranges between 1 and 29 wt %.
[0058] It has surprisingly been found that a molar ratio of oxetane
to glycidylether is preferred from the viewpoint of reactivity if
the molar ratio of oxetane to glycidylether is between 0.1 and 1.5,
more preferably between 0.2 and 1.0. Within these ranges, an
unexpectedly high reactivity of the composition towards actinic
radiation is observed.
[0059] An oxetane compound comprises at least one oxetane ring
shown by the following formula (1). ##STR1##
[0060] The oxetane compound can be polymerised or crosslinked by
irradiation with light in the presence of a cationically
polymerizable photoinitiator. The oxetane, or oxetane compound, may
comprise one or more oxetane rings.
[0061] Examples of oxetanes having one oxetane ring in the
molecule, are shown by the following formula (2): ##STR2## wherein
Z represents an oxygen atom or sulphur atom; R1 represents a
hydrogen atom, fluorine atom, an alkyl group having 1-6 carbon
atoms such as a methyl group, ethyl group, propyl group, and butyl
group, a fluoroalkyl group having 1-6 carbon atoms such as
trifluoromethyl group, perfluoroethyl group, and perfluoropropyl
group, an aryl group having 6-18 carbon atoms such as a phenyl
group and naphthyl group, a furyl group, or a thienyl group; and R2
represents a hydrogen atom, an alkyl group having 1-6 carbon atoms
for example a methyl group, ethyl group, propyl group, and butyl
group, an alkenyl group having 2-6 carbon atoms for example a
1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group,
2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group, and
3-butenyl group, an aryl group having 6-18 carbon atoms for example
a phenyl group, naphthyl group, anthranyl group, and phenanthryl
group, a substituted or unsubstituted aralkyl group having 7-18
carbon atoms for example a benzyl group, fluorobenzyl group,
methoxy benzyl group, phenethyl group, styryl group, cynnamyl
group, ethoxybenzyl group, a group having other aromatic rings for
instance an aryloxyalkyl for example a phenoxymethyl group and
phenoxyethyl group, an alkylcarbonyl group having 2-6 carbon atoms
for example an ethylcarbonyl group, propylcarbonyl group,
butylcarbonyl group, an alkoxy carbonyl group having 2-6 carbon
atoms for example an ethoxycarbonyl group, propoxycarbonyl group,
butoxycarbonyl group, an N-alkylcarbamoyl group having 2-6 carbon
atoms such as an ethylcarbamoyl group, propylcarbamoyl group,
butylcarbamoyl group, pentylcarbamoyl group, or a polyethergroup
having 2-1000 carbon atoms.
[0062] Examples of oxetane compounds having two oxetane rings in
the molecule are compounds shown by the following formula (3):
##STR3## wherein R1 is the same as defined for the above formula
(2); R3 represents a linear or branched alkylene group having 1-20
carbon atoms for example an ethylene group, propylene group, and
butylene group, a linear or branched poly(alkyleneoxy) group having
1-120 carbon atoms for example a poly(ethyleneoxy) group and
poly(propyleneoxy) group, a linear or branched unsaturated
hydrocarbon group for example a propenylene group,
methylpropenylene group, and butenylene group; and R3 may be a
polyvalent group selected from groups shown by the following
formulas (4), (5), and (6): ##STR4## wherein R4 represents an alkyl
group having 1-4 carbon atoms, an alkoxy group having 1-4 carbon
atoms, a halogen atom for example a chlorine atom or bromine atom,
a nitro group, cyano group, mercapto group, carboxyl group, or
carbamoyl group, and x is an integer from 0-4; ##STR5## wherein R5
represents an oxygen atom, sulphur atom, methylene group, --NH--,
--SO--, --SO2-, --C(CF3)2-, or --C(CH3)2-; ##STR6## wherein R6
represents an alkyl group having 1-4 carbon atoms or an aryl group
having 6-18 carbon atoms for example a phenyl group or naphthyl
group, y is an integer from 0-200, and R7 represents an alkyl group
having 1-4 carbon atoms, an aryl group having 6-18 carbon atoms for
example a phenyl group or naphthyl group, or a group shown by the
following formula (7): ##STR7## wherein R8 represents an alkyl
group having 1-4 carbon atoms or an aryl group having 6-18 carbon
atoms for example a phenyl group or naphthyl group, and z is an
integer from 0-100.
[0063] As specific examples of the compounds having two oxetane
rings in the molecule, compounds shown by the following formulas
(9), and (10) can be given. ##STR8##
[0064] In the formula (10), R1 is the same as defined for the above
formula (2).
[0065] Examples of the compounds having three or more oxetane rings
in the molecule are compounds represented by formula (11): ##STR9##
wherein R1 is the same as defined for the above formula (2); R9
represents an organic group with a valence of 3-10.
[0066] Specific examples of compounds having three or more oxetane
rings in the molecule are compounds shown by the following formula
(18): ##STR10##
[0067] Compounds shown by the following formula (19) may comprise
1-10 oxetane rings: ##STR11## wherein R1 is the same as defined for
the formula (2), R8 is the same as defined for the formula (7), R11
represents an alkyl group having 1-4 carbon atoms or trialkylsilyl
group (wherein each alkyl group individually is an alkyl group
having 1-12 carbon atom), for example a trimethylsilyl group,
triethylsilyl group, tripropylsilyl group, or tributylsilyl group,
and r is an integer from 1-10.
[0068] Furthermore, other than the above-mentioned compounds,
compounds having a polystyrene-reduced number average molecular
weight measured by gel permeation chromatography of 1,000-5,000 can
be given as examples of the oxetane compound (A). As examples of
such compounds, compounds shown by the following formulas (20),
(21), and (22) can be given: ##STR12## wherein p is an integer from
20-200: ##STR13## wherein q is an integer from 15-100: ##STR14##
wherein s is an integer from 20-200.
[0069] Specific examples of the above-described oxetane compounds
are given below.
[0070] Compounds containing one oxetane ring in the molecule:
3-ethyl-3-hydroxymethyloxetane,
3-(meth)allyloxymethyl-3-ethyloxetane,
(3-ethyl-3-oxetanylmethoxy)methylbenzene,
(3-ethyl-3-oxetanylmethoxy)benzene,
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, isobornyloxyethyl
(3-ethyl-3-oxetanylmethyl) ether, isobornyl
(3-ethyl-3-oxetanylmethyl) ether, 2-ethylhexyl (3-ethyl -3-oxetanyl
methyl) ether, ethyldiethylene glycol (3-ethyl-3-oxetanylmethyl)
ether, dicyclopentadiene (3-ethyl-3-oxetanylmethyl) ether,
dicyclopentenyloxyethyl (3-ethyl-3-oxetanyl methyl) ether,
dicyclopentenyl (3-ethyl-3-oxetanylmethyl) ether,
tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether,
tetrabromophenyl (3-ethyl-3-oxetanylmethyl) ether,
2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether,
tribromophenyl (3-ethyl-3-oxetanylmethyl) ether,
2-tribromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether,
2-hydroxyethyl (3-ethyl-3-oxetanyl methyl) ether, 2-hydroxypropyl
(3-ethyl-3-oxetanylmethyl) ether, butoxyethyl
(3-ethyl-3-oxetanylmethyl) ether, pentachlorophenyl
(3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl
(3-ethyl-3-oxetanylmethyl) ether, bornyl (3-ethyl-3-oxetanylmethyl)
ether.
[0071] Compounds containing two or more oxetane rings in the
molecule: 3,7-bis(3-oxetanyl)-5-oxa-nonane,
3,3'-(1,3-(2-methylenyl)propanediylbis(oxymethylene))bis-(3-ethyloxetane)-
, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,
1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane,
1,3-bis[(3-ethyl-3-oxetanylmethoxy)methy]propane, ethylene glycol
bis(3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyl
bis(3-ethyl-3-oxetanylmethyl) ether, triethylene glycol
bis(3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol
bis(3-ethyl-3-oxetanylmethyl) ether, tricyclodecanediyldimethylene
(3-ethyl-3-oxetanylmethyl) ether, trimethylolpropane
tris(3-ethyl-3-oxetanylmethyl) ether,
1,4-bis(3-ethyl-3-oxetanylmethoxy)butane,
1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, pentaerythritol
tris(3-ethyl-3-oxetanylmethyl) ether, pentaerythritol
tetrakis(3-ethyl-3-oxetanylmethyl) ether, polyethylene glycol
bis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol
hexakis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol
pentakis(3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol
tetrakis(3-ethyl-3-oxetanylmethyl) ether, caprolactone-modified
dipentaerythritol hexakis(3-ethyl-3-oxetanylmethyl)ether,
caprolactone-modified dipentaerythritol
pentakis(3-ethyl-3-oxetanylmethyl) ether, ditrimethylolpropane
tetrakis(3-ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol A
bis(3-ethyl-3-oxetanylmethyl) ether, PO-modified bisphenol A
bis(3-ethyl-3-oxetanylmethyl) ether, EO-modified hydrogenated
bisphenol A bis(3-ethyl-3-oxetanylmethyl) ether, PO-modified
hydrogenated bisphenol A bis(3-ethyl-3-oxetanylmethyl) ether,
EO-modified bisphenol F (3-ethyl-3-oxetanylmethyl) ether. These
compounds can be used either individually or in combination of two
or more.
[0072] Preferred oxetanes are selected from the group consisting of
components defined by formula 2, wherein R.sup.1 is a C1-C4 alkyl
group, Z=Oxygen and R.sup.2=H, a C1-C8 alkyl group or a
phenylgroup; 3-ethyl-3-hydroxymethyloxetane,
(3-ethyl-3-oxetanylmethoxy)methylbenzene,
(3-ethyl-3-oxetanylmethoxy)benzene, 2-ethylhexyl
(3-ethyl-3-oxetanyl methyl) ether,
1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,
1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane,
1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol
bis(3-ethyl-3-oxetanylmethyl) ether and
bis(3-ethyl-3-oxetanylmethyl) ether.
[0073] The oxetane compounds can be used either individually or in
combinations of two or more.
[0074] The content of the oxetane compound in the resin composition
of the present invention is preferably 1-50 wt %, more preferably
3-29 wt % and still more preferably 10-25 wt %, relative to the
total composition.
[0075] Other cationically polymerizable components that may be used
in the composition of the present invention include, for instance,
cyclic ether compounds, cyclic lactone compounds, cyclic acetal
compounds, cyclic thioether compounds, spiro orthoester compounds,
and vinylether compounds.
[0076] It is of course possible to use mixtures of cationically
polymerizable components in the compositions according to the
invention.
[0077] Preferably the composition of the present invention
comprises, relative to the total weight of the composition, at
least 20 wt %, more preferably at least 40 wt %, and most
preferably at least 60 wt % of cationically curable components.
Preferably the composition of the invention comprises, relative to
the total weight of the composition, less than 95 wt %, more
preferably less than 90 wt % cationically curable components.
(D) Multifunctional Acrylate Compound
[0078] The composition of the present invention may also contain
radically polymerizable compounds. Suitable examples of radical
polymerizable compounds are compounds having one or more
ethylenically unsaturated groups, like for example compounds having
acrylate or methacrylate groups.
[0079] Examples of monofunctional ethylenically unsaturated
compounds include acrylamide, (meth)acryloylmorpholine,
7-amino-3,7-dimethyloctyl (meth)acrylate,
isobutoxymethyl(meth)acrylamide, isobornyloxyethyl (meth)acrylate,
isobornyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
ethyldiethylene glycol (meth)acrylate, t-octyl (meth)acrylamide,
diacetone (meth)acrylamide, dimethylaminoethyl (meth)acrylate,
diethylaminoethyl (meth)acrylate, lauryl (meth)acrylate,
dicyclopentadiene (meth)acrylate, dicyclopentenyloxyethyl
(meth)acrylate, dicyclopentenyl (meth)acrylate, N,N-dimethyl
(meth)acrylamidetetrachlorophenyl (meth)acrylate,
2-tetrachlorophenoxyethyl (meth)acrylate, tetrahydrofurfuryl
(meth)acrylate, tetrabromophenyl (meth)acrylate,
2-tetrabromophenoxyethyl (meth)acrylate, 2-trichlorophenoxyethyl
(meth)acrylate, tribromophenyl (meth)acrylate,
2-tribromophenoxyethyl (meth)acrylate, 2-hydroxyethyl
(meth)acrylate, 2-hydroxypropyl (meth)acrylate, vinylcaprolactam,
N-vinylpyrrolidone, phenoxyethyl (meth)acrylate, butoxyethyl
(meth)acrylate, pentachlorophenyl (meth)acrylate, pentabromophenyl
(meth)acrylate, polyethylene glycol mono(meth)acrylate,
polypropylene glycol mono(meth)acrylate, bornyl (meth)acrylate and,
methyltriethylene diglycol (meth)acrylate.
[0080] Examples of the polyfunctional radically polymerizable
compounds include ethylene glycol di(meth)acrylate, dicyclopentenyl
di(meth)acrylate, triethylene glycol diacrylate, tetraethylene
glycol di(meth)acrylate, tricyclodecanediyldimethylene
di(meth)acrylate; trimethylolpropane tri(meth)acrylate, ethylene
oxide (hereinafter may be abbreviated as "EO") modified
trimethylolpropane tri(meth)acrylate, propylene oxide (hereinafter
may be abbreviated as "PO") modified trimethylolpropane
tri(meth)acrylate, tripropylene glycol di(meth)acrylate, neopentyl
glycol di(meth)acrylate, both-terminal (meth)acrylic acid adduct of
bisphenol A diglycidyl ether, 1,4-butanediol di(meth)acrylate,
1,6-hexanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate,
pentaerythritol tetra(meth)acrylate, polyethylene glycol
di(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
dipentaerythritol penta(meth)acrylate, dipentaerythritol
tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate,
EO-modified bisphenol A di(meth)acrylate, PO-modified bisphenol A
di(meth)acrylate, EO-modified hydrogenated bisphenol A
di(meth)acrylate, PO-modified hydrogenated bisphenol A
di(meth)acrylate, EO-modified bisphenol F di(meth)acrylate,
(meth)acrylate of phenol novolak polyglycidyl ether, and the
like.
[0081] Preferred radically polymerizable compounds are selected
from the group consisting of bisphenol A diglycidylether diacrylate
and mono-acrylate, dipentaerithritol hexacrylate and pentacrylate,
trimethylolpropane triacrylate, neopentylglycol propoxylated
diacrylate and isobornyl acrylate.
[0082] Each of the above mentioned radically polymerizable
compounds can be used either individually or in combinations of two
or more, or in combinations of at least one monofunctional monomer
and at least one polyfunctional monomer.
[0083] The content of the radically polymerizable compound that may
be used in the photocurable resin composition of the present
invention is usually 0-45 wt %, preferably 3-35 wt %. Preferably
polyfunctional acrylates, having functionality between 2 and 6 are
used in the compositions of the present invention in amounts
between 1 and 30, more preferably 2-20, most preferably between 3
and 15 wt %, relative to the total composition.
(E) Radical Photoinitiator
[0084] The compositions of the present invention may employ one or
more free radical photoinitiators. Examples of photoinitiators
include benzoins, such as benzoin, benzoin ethers, such as benzoin
methyl ether, benzoin ethyl ether, and benzoin isopropyl ether,
benzoin phenyl ether, and benzoin acetate, acetophenones, such as
acetophenone, 2,2-dimethoxyacetophenone,
4-(phenylthio)acetophenone, and 1,1-dichloroacetophenone, benzil,
benzil ketals, such as benzil dimethyl ketal, and benzil diethyl
ketal, anthraquinones, such as 2-methylanthraquinone,
2-ethylanthraquinone, 2-tertbutylanthraquinone,
1-chloroanthraquinone, and 2-amylanthraquinone, also
triphenylphosphine, benzoylphosphine oxides, such as, for example,
2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO),
benzophenones, such as benzophenone, dimethoxybenzophenone,
diphenoxybenzophenone, and
4,4'-bis(N,N'-dimethylamino)benzophenone, thioxanthones and
xanthones, acridine derivatives, phenazene derivatives, quinoxaline
derivatives or l-phenyl-1,2-propanedione-2-O-benzoyloxime,
l-aminophenyl ketones or l-hydroxyphenyl ketones, such as
1-hydroxycyclohexyl phenyl ketone, phenyl
(1-hydroxyisopropyl)ketone and
4-isopropylphenyl(1-hydroxyisopropyl)ketone, or triazine compounds,
for example, 4'''-methyl
thiophenyl-1-di(trichloromethyl)-3,5-S-triazine,
S-triazine-2-(stilbene)4,6-bistrichloromethyl, and paramethoxy
styryl triazine, all of which are known compounds.
[0085] Especially suitable free-radical photoinitiators, which are
normally used in combination with a He/Cd laser, operating at for
example 325 nm, an Argon-ion laser, operating at for example 351
nm, or 351 and 364 nm, or 333, 351, and 364 nm, or a frequency
tripled YAG solid state laser, having an output of 351 or 355 nm,
as the radiation source, are acetophenones, such as
2,2-dialkoxybenzophenones and 1-hydroxyphenyl ketones, for example
1-hydroxycyclohexyl phenyl ketone,
2-hydroxy-1-{4-(2-hydroxyethoxy)phenyl}-2-methyl-1-propanone,
benzophenone, or 2-hydroxyisopropyl phenyl ketone (also called
2-hydroxy-2,2-dimethylacetophenone), but especially
1-hydroxycyclohexyl phenyl ketone. Another class of free-radical
photoinitiators comprises the benzil ketals, such as, for example,
benzil dimethyl ketal. Especially an alpha-hydroxyphenyl ketone,
benzil dimethyl ketal, or 2,4,6-trimethylbenzoyldiphenylphosphine
oxide may be used as photoinitiator.
[0086] Another class of suitable free radical photoinitiators
comprises the ionic dye-counter ion compounds, which are capable of
absorbing actinic rays and producing free radicals, which can
initiate the polymerization of the acrylates. The compositions
according to the invention that comprise ionic dye-counter ion
compounds can thus be cured in a more variable manner using visible
light in an adjustable wavelength range of 400 to 700 nanometers.
Ionic dye-counter ion compounds and their mode of action are known,
for example from published European patent application EP 223587
and U.S. Pat. Nos. 4,751,102, 4,772,530 and 4,772,541. There may be
mentioned as examples of suitable ionic dye-counter ion compounds
the anionic dye-iodonium ion complexes, the anionic dye-pyryllium
ion complexes and, especially, the cationic dye-borate anion
compounds of the following formula (10) ##STR15## wherein D.sup.+
is a cationic dye and R.sub.12, R.sub.13, R.sub.14, and R.sub.15
are each independently of the others alkyl, aryl, alkaryl, allyl,
aralkyl, alkenyl, alkynyl, an alicyclic or saturated or unsaturated
heterocyclic group. Preferred definitions for the radicals R.sub.12
to R.sub.15 can be found, for example, in published European patent
application EP 223587.
[0087] Preferred free radical photoinitiators include
1-hydroxycyclohexyl phenyl ketone,
2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxyacetophenone,
benzophenone and 2,4,6-trimethylbenzoyidiphenylphosphine oxide.
These photoinitiators alone or in combination with each other tend
to be comparatively less yellowing.
[0088] Preferably, the present composition comprises, relative to
the total weight of the composition, 0.1-15 wt % of one or more
free radical photoinitiators, more preferably 1-10 wt %.
(F) Cationic Photoinititator
[0089] In the compositions according to the invention, any suitable
type of photoinitiator that, upon exposure to actinic radiation,
forms cations that initiate the reactions of the cationically
polymerizable compounds, such as epoxy material(s), can be used.
There are a large number of known and technically proven cationic
photoinitiators that are suitable. They include, for example, onium
salts with anions of weak nucleophilicity. Examples are halonium
salts, iodosyl salts or sulfonium salts, such as are described in
published European patent application EP 153904 and WO 98/28663,
sulfoxonium salts, such as described, for example, in published
European patent applications EP 35969, 44274, 54509, and 164314, or
diazonium salts, such as described, for example, in U.S. Pat. Nos.
3,708,296 and 5,002,856. All eight of these disclosures are hereby
incorporated in their entirety by reference. Other cationic
photoinitiators are metallocene salts, such as described, for
example, in published European applications EP 94914 and 94915,
which applications are both hereby incorporated in their entirety
by reference.
[0090] A survey of other current 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), and both books are
hereby incorporated in their entirety by reference.
[0091] Preferred initiators include diaryl iodonium salts, triaryl
sulfonium salts, or the like. Typical photo-polymerization
initiators are represented by the following formulae (8) and (9):
##STR16## wherein [0092] Q.sub.3 represents a hydrogen atom, an
alkyl group having 1 to 18 carbon atoms, or an alkoxyl group having
1 to 18 carbon atoms; [0093] M represents a metal atom, preferably
antimony; [0094] Z represents a halogen atom, preferably fluorine;
and [0095] t is the valent number of the metal, for example 6 in
the case of antimony.
[0096] Preferred cationic photoinitiators include iodonium
photoinitiators, e.g. iodonium tetrakis (pentafluorophenyl) borate,
because they tend to be less yellowing, especially when used in
combination with photosensitizers such as, for instance, n-ethyl
carbazole.
[0097] In order to increase the light efficiency, or to sensitize
the cationic photoinitiator to specific wavelengths, such as for
example specific laser wavelengths or a specific series of laser
wavelengths, it is also possible, depending on the type of
initiator, to use sensitizers. Examples are polycyclic aromatic
hydrocarbons or aromatic keto compounds. Specific examples of
preferred sensitizers are mentioned in published European patent
application EP 153904. Other preferred sensitizers are
benzoperylene, 1,8-diphenyl-1,3,5,7-octatetraene, and
1,6-diphenyl-1,3,5-hexatriene as described in U.S. Pat. No.
5,667,937, which is hereby incorporated in its entirety by
reference. It will be recognized that an additional factor in the
choice of sensitizer is the nature and primary wavelength of the
source of actinic radiation.
[0098] Preferably, the present composition comprises, relative to
the total weight of the composition, 0.1-15 wt % of one or more
cationic photoinitiators, more preferably 1-10 wt %.
(G) Hydroxy Functional Components
[0099] Most of the known compositions use hydroxy-functional
compounds to enhance the properties of the parts made from the
compositions. It has been surprisingly found, that the presence of
hydroxy functional compounds that have no other cationically
polymerizable functional group like an epoxy, oxetane or acrylate
group, is not needed in the compositions of the present invention
to obtain parts having excellent mechanical properties.
Nevertheless, the present compositions may comprise suitable
non-free radical polymerizable hydroxy-functional compounds.
[0100] The hydroxyl-containing material which can be used in the
present invention may be any suitable organic material having a
hydroxyl functionality of at least 1. The material is preferably
substantially free of any groups which interfere with the curing
reactions or which are thermally or photolytically unstable.
[0101] Any hydroxy group may be employed for the particular
purpose. Preferably the hydroxyl-containing material contains one
or more primary or secondary aliphatic hydroxyl. The hydroxyl group
may be internal in the molecule or terminal. Monomers, oligomers or
polymers can be used. The hydroxyl equivalent weight, i.e., the
number average molecular weight divided by the number of hydroxyl
groups, is preferably in the range of 31 to 5000.
[0102] Representative examples of hydroxyl-containing materials
having a hydroxyl functionality of 1 include alkanols, monoalkyl
ethers of polyoxyalkyleneglycols, monoalkyl ethers of
alkyleneglycols, and others, and combinations thereof.
[0103] Representative examples of useful monomeric polyhydroxy
organic materials include alkylene and arylalkylene glycols and
polyols, such as 1,2,4-butanetriol, 1,2,6-hexanetriol,
1,2,3-heptanetriol, 2,6-dimethyl-1,2,6-hexanetriol,
(2R,3R)-(-)-2-benzyloxy-1,3,4-butanetriol, 1,2,3-hexanetriol,
1,2,3-butanetriol, 3-methyl-1,3,5-pentanetriol,
1,2,3-cyclohexanetriol, 1,3,5-cyclohexanetriol,
3,7,11,15-tetramethyl-1,2,3-hexadecanetriol,
2-hydroxymethyltetrahydropyran-3,4,5-triol,
2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,3-cyclopentanediol,
trans-1,2-cyclooctanediol, 1,16-hexadecanediol,
3,6-dithia-1,8-octanediol, 2-butyne-1,4-diol, 1,3-propanediol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol,
1,8-octanediol, 1,9-nonanediol, 1-phenyl-1,2-ethanediol,
1,2-cyclohexanediol, 1,5-decalindiol,
2,5-dimethyl-3-hexyne-2,5-diol,
2,7-dimethyl-3,5-octadiyne-2-7-diol, 2,3-butanediol,
1,4-cyclohexanedimethanol, and combinations thereof.
[0104] Representative examples of useful oligomeric and polymeric
hydroxyl-containing materials include polyoxyethylene and
polyoxypropylene glycols and triols of molecular weights from about
200 to about 10,000; polytetramethylene glycols of varying
molecular weight; poly(oxyethylene-oxybutylene) random or block
copolymers; copolymers containing pendant hydroxy groups formed by
hydrolysis or partial hydrolysis of vinyl acetate copolymers,
polyvinylacetal resins containing pendant hydroxyl groups;
hydroxy-terminated polyesters and hydroxy-terminated polylactones;
hydroxy-functionalized polyalkadienes, such as polybutadiene;
aliphatic polycarbonate polyols, such as an aliphatic polycarbonate
diol; and hydroxy-terminated polyethers, and combinations
thereof.
[0105] Preferred hydroxyl-containing monomers include
1,4-cyclohexanedimethanol and aliphatic and cycloaliphatic
monohydroxy alkanols. Preferred hydroxyl-containing oligomers and
polymers include hydroxyl and hydroxyl/epoxy functionalized
polybutadiene, polycaprolactone diols and triols, ethylene/butylene
polyols, and monohydroxyl functional monomers. Preferred examples
of polyether polyols are polypropylene glycols of various molecular
weights and glycerol propoxylate-B-ethoxylate triol. Especially
preferred are linear and branched polytetrahydrofuran polyether
polyols available in various molecular weights, such as in the
range of 150-4000 g/mol, preferably in the range of 150-1500 g/mol,
more preferably in the range of 150-750 g/mol.
[0106] If present, the composition preferably comprises, relative
to the total weight of the- composition, at least 1 wt % of one or
more non-free radical polymerizable hydroxy-functional compounds,
more preferably at least 5 wt %, and most preferably at least 10 wt
%. Furthermore, the composition preferably comprises, relative to
the total weight of the composition, at most 60 wt % of one or more
non-free radical polymerizable hydroxy-functional compounds, more
preferably at most 40 wt %, and most preferably at most 25 wt
%.
(H) Additives
[0107] Additives may also be present in the composition of the
invention. Stabilizers are often added to the compositions in order
to prevent a viscosity build-up, for instance a viscosity build-up
during usage in a solid imaging process. Preferred stabilizers
include those described in U.S. Pat. No. 5,665,792, the entire
disclosure of which is hereby incorporated by reference. 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.
Rubidium carbonate is preferred for formulations of this invention
with recommended amounts varying between 0.0015 to 0.005% by weight
of composition. Alternative stabilizers are polyvinylpyrrolidones
and polyacrylonitriles. Other possible additives include dyes,
pigments, fillers (e.g. silica particles -preferably cylindrical or
spherical silica particles-, talc, glass powder, alumina, alumina
hydrate, magnesium oxide, magnesium hydroxide, barium sulfate,
calcium sulfate, calcium carbonate, magnesium carbonate, silicate
mineral, diatomaceous earth, silica sand, silica powder, titanium
oxide, aluminum powder, bronze powder, zinc powder, copper powder,
lead powder, gold powder, silver dust, glass fiber, titanic acid
potassium whisker, carbon whisker, sapphire whisker, beryllia
whisker, boron carbide whisker, silicon carbide whisker, silicon
nitride whisker, glass beads, hollow glass beads, metaloxides and
potassium titanate whisker), antioxidants, wetting agents,
photosensitizers for the free-radical photoinitiator, chain
transfer agents, leveling agents, defoamers, surfactants and the
like.
Applications
[0108] The present compositions are suitable for a wide variety of
applications. For instance, the compositions can be used to prepare
a three dimensional object by rapid prototyping. Rapid prototyping,
sometimes also referred to as "solid imaging" or
"stereolithography", is a process wherein a photoformable
composition is coated as a thin layer upon a surface and exposed
imagewise to actinic radiation such that the composition solidifies
imagewise. This coating is most conveniently done if the
composition is a liquid at room temperature, but a solid
composition may also be melted to form a layer, or a solid or paste
composition may be coated if it shows shear thinning behavior.
Subsequently, new thin layers of photoformable composition are
coated onto previous layers of exposed and unexposed composition.
Then the new layer is exposed imagewise in order to solidify
portions imagewise and in order to induce adhesion between portions
of the new hardened region and portions of the previously hardened
region. Each imagewise exposure is of a shape that relates to a
pertinent cross-section of a photohardened object such that when
all the layers have been coated and all the exposures have been
completed, an integral photohardened object can be removed from the
surrounding composition.
[0109] Accordingly, a rapid prototyping process can for instance be
described as: [0110] (1) coating a thin layer of a composition onto
a surface; [0111] (2) exposing said thin layer imagewise to actinic
radiation to form an imaged cross-section, wherein the radiation is
of sufficient intensity and time to cause substantial curing of the
thin layer in the exposed areas; [0112] (3) coating a thin layer of
the composition onto the previously exposed imaged cross-section;
[0113] (4) exposing said thin layer from step (3) imagewise to
actinic radiation to form an additional imaged cross-section,
wherein the radiation is of sufficient intensity and time to cause
substantial curing of the thin layer in the exposed areas and to
cause adhesion to the previously exposed imaged cross-section;
[0114] (5) repeating steps (3) and (4) a sufficient number of times
in order to build up the three-dimensional article.
EXAMPLES
Example 1
[0115] The effect of the presence of a cationically curable
component with linking aliphatic ester groups on the hydrolytic
stability of a part was determined with IR (infrared) analysis
while the impact on mechanical properties was evaluated by TMA
(thermomechanical analysis).
[0116] Blends of 3,4-Epoxy Cyclohexyl Methyl-3,4-Epoxy Cyclohexyl
Carboxylate (UVI 1500) (Linking Ester Epoxy), and hydrogenated
bisphenol A diglycidyl ether (Eponex 1510) (Epoxy 1), were mixed
with 5% 3-Ethyl-3-(hydroxymethyl)oxetane (UVR6000) (Oxetane 1), and
0.6%
Sulfonium,(thiodi-4,1-phenylene)bis[diphenyl-bis[(OC-6-11)hexafluoroantim-
onate(1-)]] CPI-6976 (Cationic Initiator 1).
[0117] The ratios of Linking Ester Epoxy to Epoxy 1 varied from
100% Linking Ester Epoxy to 100% Epoxy 1 in 20% increments.
[0118] For the IR study, one gram aliquots of each mixture were
spiked with 0.02 g of perdeuterated dodecane. The D26 dodecane,
available from Aldrich, was chosen as an internal standard because
it absorbs in a distinct region in the IR and should be chemically
inert. For the IR study a few drops of each deuterated formulation
were placed between polymethylpentene plates and cured in a 10 bulb
PCA (3 D Systems Post Curing Apparatus) for 60 minutes. The bulbs
were Phillips TLK 40W/05 which had been used for .about.1500 hours.
Films of 20-30 micron thickness yielded well resolved IR spectra.
These thin films were placed between pieces of the cured thick
plates. The samples were heated at 35 deg. C. for 28 hours in a
closed plastic container with a pool of water on the bottom (the
films were not in contact with the liquid water). IR spectra were
then recorded for the films, and the procedure was repeated after
an additional 21 hours humidity exposure. As a reference, films of
some of the formulations were heated at 35.degree. C. in a
desiccated jar; IR spectra were also recorded for these films.
[0119] The extent of hydrolysis is indicated by the change in area
of the --OH stretching absorbance (3100-3600 cm-1): hydrolysis of
the ester groups in the Linking Ester Epoxy yields alcohol and
carboxylic acid groups (both will absorb in the --OH region). In 25
micron thick films, the hydrolysis reaches an equilibrium value in
no longer than 28 hours. The presence of the Epoxy 1 does not
appear to affect the extent of hydrolysis of the Linking Ester
Epoxy.
[0120] The thin films at 80 and 100% Linking Ester Epoxy were found
to stick to the thick plates after humid conditioning and were
noticeably more brittle.
[0121] The most obvious change in the IR spectra after humidity
conditioning was an increase in absorbance in the OH region. Both
the intensity and the breadth of the absorbance increased, with a
shift in intensity towards lower energy. The peak areas were
normalized against the areas of the CD (carbon-deuterium) stretch
absorbance and against the --CH (carbon-hydrogen) stretch
absorbance. Because of the relatively large error in determining
the peak area of the --CD absorbance, the --CH absorbance was
chosen as the internal reference. The increase in --OH absorbance
at 28 hr. versus the initial value was found to be proportional to
the amount of Linking Ester Epoxy in the formulation as shown in
Table 1: TABLE-US-00001 TABLE 1 % of Linking Ester Epoxy Increase
of OH-absorbance after 28 hr 100% 8.5 80% 9.2 60% 5.2 40% 5.2 20%
3.4 0% 3.1
[0122] This experiment indicates that hydrolysis of films prepared
from blends of Linking Ester Epoxy and Epoxy 1 proceeds rapidly at
35 deg. C. and high humidity.
[0123] This hydrolysis is accompanied by a loss of mechanical
properties. The Linking Ester Epoxy/Epoxy 1 blends described above
(without the deuterated dodecane) were used to measure the effect
of humidity exposure on Flexural Modulus. Approximately 18 grams of
each non-deuterated formulation were poured into polymethylpentene
petri dishes (available from Nalge Nunc International, part number
5500-0010 which have a nominal size of 100 mm diameter and 15 mm
height) and PCA cured for one hour. 10 mm long.times.3 mm wide
samples were cut from the cured films. The samples were analyzed
with a TA Associates TMA 2940 using a flexure probe. The stress on
the sample is given by the equation S=3LF/(2bd.sup.2) where
[0124] S=Stress (MPa)
[0125] L=Sample length (mm)
[0126] F=Force exerted by TMA probe (N)
[0127] b=Sample width (mm)
[0128] d=Sample thickness (mm)
The sample strain is given by the equation r=6dD/L.sup.2 where D is
the deflection of the surface of the sample at mid-span The flex
modulus is the stress divided by the strain
E=(F/D)(L.sup.3/4bd.sup.3)
[0129] So for a given sample geometry, the modulus is directly
proportional to the slope of the plot of applied force versus
deflection.
[0130] The analysis was made at 30.degree. C. with the force on the
parts cycled twice from 0.01 to 0.5 N and back; the modulus was
calculated from 0.05 to 0.1 N applied force. The average values for
the two ramp-down cycles were used for the analysis. Between
analyses, samples were kept in an oven at 35.degree. C. Half the
samples were kept in a desiccator jar while the other half were
kept in high humidity. The modulus was measured of a sample, kept
under high humidity condition (28 hours, 35 .quadrature.C and 100%
relative humidity (RH); wet condition) and compared with the
modulus of a sample kept under dry conditions (35 .quadrature.C
having less than 10% RH). The Modulus Ratio (Wet/Dry) is the ratio
of the value of the Modulus of the sample, kept under the wet
condition to the value of the Modulus of the sample kept under the
dry condition. TABLE-US-00002 TABLE 2 % Ester Linked Epoxy Modulus
Ratio (Wet/Dry) 100 0.47 80 0.55 60 0.71 40 0.66 20 N.D. 0 0.85
TMA Results: Flexure modulus of samples maintained at high humidity
are lower than those kept dry at 35 deg. C. As shown in Table 2,
samples with high ester linked epoxy content have lower retained
modulus than the low linking ester content samples.
Example 2
Humidity Effect on Hybrid Stereolithography Compositions
[0131] A composition of the present invention containing 59.4 wt %
of Hydrogenated Bisphenol a-Ephichlorohydrin Based Epoxy Resin
(Epoxy 1), 20 wt % of 3-Ethyl-3-(hydroxymethyl)oxetane (oxetane 1),
13 wt % of Dipentaerythritol Pentaacrylate (acrylate 1) and 1.75 wt
% of a 1-Hydroxycyclohexyl phenyl ketone, and 5.85 wt % of
Sulfonium,(thiodi-4,1-phenylene)bis[diphenyl-bis[(OC-6-11)hexafluoroantim-
onate(1-)]] is prepared as Resin A.
[0132] A comparative composition containing 55 wt % of 3,4 epoxy
Cyclohexyl methyl-3,4-Epoxy Cyclohexyl carboxylate (UVI 1500), 18
wt % of a polytetrahydrofuran-polymer, 15 wt % of Dipentaerythritol
Pentaacrylate, 5 wt % of propoxylated neopentyl glycol diacrylate,
5 wt % of
Sulfonium,(thiodi4,1-phenylene)bis[diphenyl-bis[(OC-6-11)hexafluoroant-
imonate(1-)]] and 1.6 wt % of a 1-Hydroxycyclohexyl phenyl ketone
is prepared as Resin B.
[0133] The humidity resistance of a compositions of the instant
invention (Resin A) is determined versus that of Resin B,
containing a substantial amount (55 wt %) of Linking Ester Epoxy.
In this experiment, ASTM D790 flex bars were fabricated by
stereolithography means using the following conditions:
[0134] Fabricated flexural bar size approximately 5.5 mm thick,
12.5 mm wide, and 150 mm long. The coated layer thickness was
.about.150 micron. The exposure given each layer was 51 mJ/cm.sup.2
for the Resin A and 47 mJ/cm.sup.2 for the resin B. After
fabrication by stereolithography the flexural bars were washed in
isopropanol, then dried in air.
[0135] All the samples were postcure exposed in the 10 bulb PCA
(3-D Systems Post Curing Apparatus) for 60 minutes.
[0136] After postcure, two of each-composition's flexural bars were
placed in vacuum bell jars which contained water saturated salt
solutions or just water to achieve the desired humidity for
storage. 100% RH was achieved with water in the base of the bell
jar; 80% RH was achieved with a salt solution of Potassium Hydrogen
Sulfate, Fused; 54% RH was achieved with Sodium Bisulfate
Monohydrate; and 20% RH was achieved with Potassium Acetate
saturated water solution. The samples were stored in the bell jars
at room temperature (this is approximately 22.degree. C.) for one
month.
[0137] After one month, the samples were removed from the bell jars
and immediately tested according to ASTM D790 (at approximately
22.6 Deg. C. and 25% RH). Following are the results of the
comparison: TABLE-US-00003 Humidity Storage Resin A Resin B Testing
1 month @ Flex Modulus Flex Modulus RH % Room Temp MPa Mpa 100% RH
1666 97 80% RH 1731 140 54% RH 2110 741 20% RH 2255 1508
[0138] A flexural bar made from Resin A, according to the present
invention, retains approximately 74% of its flex modulus comparing
the 20% RH and the 100% RH results. The flexural bar made from
Resin B only retains 6.4% of its flex modulus comparing the 20% and
100% RH results.
Examples 3-20 and Comparative Experiment 1
[0139] Table 3 shows more non-limiting examples of the present
inventions. Compositions have been prepared with the indicated
components. After cure with actinic radiation and subsequent 60 min
UV-postcure, mechanical analysis of the parts was performed.
TABLE-US-00004 Component Chemical Name Component Linking Ester
3,4-Epoxy Cyclohexyl Methyl-3,4-Epoxy Cyclohexyl UVR-1500 Epoxy
Carboxylate Epoxy 1 Hydrogenated Bisphenol a-Ephichlorohydrin Based
Epoxy Eponex 1510 Resin Epoxy 2 Bisphenol a-Ephichlorohydrin Based
Epoxy Resin Epon 825 Epoxy 3 Tetradecane Oxide Vikolox 14 Oxetane 1
3-Ethyl-3-(hydroxymethyl)oxetane UVR-6000 Acrylate 1
Dipentaerythritol Pentaacrylate SR-399 Acrylate 2 Propoxylated (2)
Neopentyl Glycol Diacrylate SR-9003 Free Radical
1-Hydroxycyclohexyl phenyl ketone Ir-184 Initiator Cationic
Sulfonium,(thiodi-4,1-phenylene)bis[diphenyl-bis[(OC-6- CPI 6976
Initiator 1 11)hexafluoroantimonate(1-)]] Cationic sulfonium,
(thiodi-4,1-phenylene)bis[diphenyl-, UVI-6990 Initiator 2
bis[hexafluorophosphate(1-)]]
[0140] Optionally, the compositions contain small amounts of
stabilizer, antioxidant, surfactant and defoamer.
[0141] The 1 day cured modulus is from tensile or Young's modulus
data obtained from tensile bars made in a stereolithography
machine. The bars were made in 150 um thick layers. Each
cross-sectional layer of the tensile bar was given exposure
sufficient to polymerize the composition at a 250 um depth (E10
exposure), providing approximately 100 um of overcure or engagement
cure to assure adhesion to the previously coated and exposed layer.
Comparative Example 1, Examples 3-14 and 18-20 were exposed with a
laser emitting in the UV at 355 nm. Examples 15-17 were exposed
with a laser emitting in the UV at 325 nm. The tensile bars were
approximately 150 mm long and had a cross-section in the narrowed
portion of approximately 1 cm square. The tensile tests were run
according to ASTM D638 except that no provision was made for
controlling the room temperature and humidity and the bars were not
equilibrated for 2 days. Although the data is described as 1 day,
some of data was obtained from 34 day old bars allowing for
weekends and holidays. The Average Elongation @ Break % data is
obtained from the same tensile bars. In general from 3-6 bars were
used to obtain the data for each Example. The Toughness Factor is a
multiplication of the Modulus times the Average Elongation @ Break
% and may be interpreted as a measure of the toughness of the
Example polymerized composition.
[0142] The Peak Polymerization Temperature Deg. C. and the Coated
Surface Temperature Deg. C. was obtained using a Linear
Laboratories C-600 E infrared thermometer pointed approximately at
the center of a part under fabrication. The part was a 50 mm square
and approximately 1.2 cm thick. The part was fabricated in 150 um
thick layers and each layer was exposed to produce approximately
250 um of cure depth (E10 exposure) for the Example composition.
The scanning speed was held constant at 1130 cm/sec with a 75 um
spaced overlapping scan in one direction only. The laser power was
controlled to ensure the proper cure depth for the composition. The
Peak Polymerization Temperature is the highest temperature attained
throughout part fabrication for the example formulation. The Coated
Surface Temperature is the highest temperature measured on the part
surface just after a new layer of composition was coated on the
previous layer. The Temperature Delta Deg. C. is the difference
between the Peak Polymerization Temperature and the Coated Surface
Temperature. The scanning speeds and laser powers used represent
high speed scanning and high power laser scans. TABLE-US-00005
Component Comp. Exp 1 Example 3 Example 4 Example 5 Example 6
Example 7 Example 8 Example 9 Example 10 Linking Ester Epoxy Epoxy
1 79.645 74.645 69.095 64.995 59.395 54.895 49.895 44.905 39.905
Epoxy 2 Epoxy 3 Oxetane 1 5 10 15 20 25 30 35 40 Acrylate 1 13 13
13 13 13 13 13 13 13 Acrylate 2 Free Radical Initiator 1.65 1.65
1.8 1.6 1.75 1.8 1.8 1.94 1.94 Cationic Initiator 1 5.7 5.7 6.1 5.4
5.85 5.3 5.3 5.15 5.15 Cationic Initiator 2 Total Composition 100
100 100 100 100 100 100 100 100 Oxetane/Epoxy Ratio 0.00 0.10 0.22
0.35 0.52 0.70 0.92 1.19 1.53 1 day Cured Modulus MPa 1737 2275
2572 2792 2696 2661 2613 2558 1751 Ave. Elongation @ Break % 10 7.5
3.1 4.8 6 5.9 9.8 8 26.2 Toughness Factor MPA X % 17375 17065 7972
13403 16175 15702 25609 20464 45884 Ec mJ/cm{circumflex over ( )}2
7.56 12.61 9.49 13.63 11.36 10.53 11.4 10.14 10.09 Dp mm 0.123
0.164 0.134 0.175 0.151 0.153 0.162 0.153 0.155 E10
mJ/cm{circumflex over ( )}2 59.78 59.31 62.99 58.2 61.15 55.45
54.85 53.04 52.18 Peak Polymerization Temp. Deg. C 74 64 70 76 78
81 74 73 67 Coated Surface Temperature Deg. C 54 50 50 52 52 54 52
51 51 Temperature Delta Deg. C 20 14 20 24 26 27 22 22 16 Example
Example Example Example Example Example Example Example Example
Example Component 11 12 13 14 15 16 17 18 19 20 Linking Ester Epoxy
7 10 7 Epoxy 1 62.525 59.9275 48.7474 54.7505 61.025 57.1238
59.9925 Epoxy 2 62.495 46.695 43.615 Epoxy 3 4 4 4 Oxetane 1 20 32
30 16.50 23.5 23.5 23.5 16.00 18.73 19.5 Acrylate 1 12 10 12 8 8 8
9 8 10 8 Acrylate 2 4 4 4 4 4 4 4 Free Radical Initiator 1.5 1.52
1.45 3.2 3 3.14 3.18 4 2.97 2.92 Cationic Initiator 1 4 2.75 2.9
4.3 0.35 0.39 0.347 0.365 Cationic Initiator 2 5.5 5.7012 Total
Composition 100 100 100 100 100 100 100 100 100 100 Oxetane/Epoxy
Ratio 0.49 1.06 1.06 0.40 0.60 0.69 0.62 0.40 0.50 0.47 1 day Cured
Modulus MPa 3344 3344 3447 2592 2806 2634 2461 2372 2392 2448 Ave.
Elongation @ 3.4 3.1 3.2 12.4 8.4 3.7 14.3 10.3 10.3 12.8 Break %
Toughness Factor MPA 11370 10366 11032 32146 23572 9745 35198 24430
24643 31330 X % Ec mJ/cm{circumflex over ( )}2 9.36 15.24 10.19
12.89 10.47 11.15 11.58 11.84 10.19 13.53 Dp mm 0.109 0.212 0.191
0.167 0.139 0.133 0.144 0.142 0.139 0.153 E10 mJ/cm{circumflex over
( )}2 95.1 50.59 38.51 58.97 65.33 75.45 67.39 70.62 63.26 70.79
Peak Polymerization 72 Temp. Deg. C. Coated Surface 52 Temperature
Deg. C. Temperature Delta Deg. C 20
* * * * *