U.S. patent application number 11/332270 was filed with the patent office on 2006-11-02 for polymer powders for sib processes.
This patent application is currently assigned to DEGUSSA AG. Invention is credited to Franz-Erich Baumann, Christian Gerth, Maik Grebe, Sylvia Monsheimer.
Application Number | 20060244169 11/332270 |
Document ID | / |
Family ID | 31947640 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060244169 |
Kind Code |
A1 |
Monsheimer; Sylvia ; et
al. |
November 2, 2006 |
Polymer powders for SIB processes
Abstract
A process of selective inhibition of bonding (SIB) to produce
three-dimensional objects is used to obtain high-quality moldings.
High-quality moldings can be produced by using pulverulent
materials which have a median particle size of from 10 to 200 .mu.m
in which at least one polymer or copolymer selected from polyester,
polyvinyl chloride, polyacetal, polypropylene, polyethylene,
polystyrene, polycarbonate, polymethyl methacrylate (PMMA), PMMI,
ionomer, polyamides, copolyester, copolyamides, terpolymers, or
ABS, or a mixture of these, is present.
Inventors: |
Monsheimer; Sylvia; (Haltern
am See, DE) ; Gerth; Christian; (Haltern am See,
DE) ; Baumann; Franz-Erich; (Duelmen, DE) ;
Grebe; Maik; (Bochum, DE) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
DEGUSSA AG
Duesseldorf
DE
|
Family ID: |
31947640 |
Appl. No.: |
11/332270 |
Filed: |
January 17, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10665472 |
Sep 22, 2003 |
|
|
|
11332270 |
Jan 17, 2006 |
|
|
|
Current U.S.
Class: |
264/113 |
Current CPC
Class: |
B33Y 80/00 20141201;
Y10T 156/10 20150115; B33Y 70/00 20141201; B33Y 10/00 20141201;
Y10T 428/2982 20150115; B29C 64/153 20170801 |
Class at
Publication: |
264/113 |
International
Class: |
D04H 1/16 20060101
D04H001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 2002 |
DE |
102 44 047.6 |
Mar 15, 2003 |
DE |
103 11 446.7 |
Claims
1. A process for producing a three-dimensional object, comprising:
a) providing a layer of a pulverulent material, b) applying one or
more bonding inhibitors to one or more regions of the layer wherein
the regions to which the bonding inhibitor is applied are the cross
section regions of the three-dimensional object, and wherein no
bonding inhibitor is applied to regions which are not the cross
section regions of the three-dimensional object, c) repeating a)
and b) until all of the cross-section regions of the
three-dimensional object are a matrix of inhibitor-applied
pulverulent layer regions, wherein the outer boundaries of the
three-dimensional object are the interface between
inhibitor-applied pulverulent material and pulverulent material
without applied inhibitor, and d) treating the layers at least once
to bond the pulverulent material which does not have applied
inhibitor, wherein the pulverulent material has a median particle
size of from 10 to 200 .mu.m and comprises at least one selected
from the group consisting of a polyester, a polyvinyl chloride, a
polyacetal, a polypropylene, a polyethylene, a polystyrene, a
polycarbonate, PMMA, PMMI, an ionomer, a polyamide, a copolyester,
a copolyamide, a terpolymer, ABS and a mixture thereof.
2. The process as claimed in claim 1, wherein d) is carried out
after b).
3. The process as claimed in claim 1, wherein d) is carried out
after c).
4. The process as claimed in claim 1, wherein the pulverulent
material is obtained by grinding, precipitation, anionic
polymerization, or a combination thereof, with optional subsequent
fractionation thereof.
5. The process as claimed in claim 1, wherein the pulverulent
material comprises at least one of nylon-6, nylon-11 or
nylon-12.
6. The process as claimed in claim 1, wherein the pulverulent
material is amorphous or semicrystalline.
7. The process as claimed in claim 1, wherein the pulverulent
material has a linear or branched structure.
8. The process as claimed in claim 1, wherein at least a portion of
the pulverulent material has a melting point of from 50 to
350.degree. C.
9. The process as claimed in claim 1, wherein at least a portion of
the pulverulent material has a melting point of from 70 to
200.degree. C.
10. The process as claimed in claim 1, wherein the pulverulent
material has a median particle size of from 20 to 100 .mu.m.
11. The process as claimed in claim 1, wherein the pulverulent
material comprises from 0.05 to 5% by weight of one or more flow
aids.
12. The process as claimed in claim 1, wherein the pulverulent
material comprises one or more inorganic fillers.
13. The process as claimed in claim 12, wherein the fillers
comprise glass beads.
14. The process as claimed in claim 1, wherein the wherein
pulverulent material comprises one or more inorganic pigments,
organic pigments, or both.
15. The process as claimed in claim 1, wherein the bonding
inhibitor comprises a material with wetting properties.
16. The process as claimed in claim 1, wherein the bonding
inhibitor comprises at least one liquid selected from the group
consisting of water, an oil, and an alcohol.
17. The process as claimed in claim 1, wherein the bonding
inhibitor temporarily inhibits bonding.
18. The process as claimed in claim 1, wherein the bonding
inhibitor comprises water and at least one surfactant.
19. The process as claimed in claim 1, further comprising
inhibiting bonding of the inhibitor-applied pulverulent layers by
vaporization and cooling.
20. The process as claimed in claim 1, further comprising
inhibiting bonding of the inhibitor-applied pulverulent layers by
forming one or more mechanical barriers between the particles of
pulverulent material of the inhibitor-applied pulverulent
layers.
21. The process as claimed in claim 1, further comprising
inhibiting bonding of the inhibitor-applied pulverulent layers by
forming one or more thermally insulating regions between the
particles of pulverulent material of the inhibitor-applied
pulverulent layers.
22-26. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a polymer powder which can be used
for producing three-dimensional objects by means of selective
inhibition of bonding (SIB), and to a process in which these
powders are used.
[0003] 2. Description of the Related Art
[0004] Very recently a need for the rapid production of prototypes
has arisen. Selective laser sintering (SLS) is a process
particularly well suited to rapid prototyping. In the SLS process,
polymer powders are selectively and briefly irradiated in a chamber
with a laser beam. Particles of powder exposed to the laser beam
melt. The molten particles fuse and solidify to give a solid mass.
Three-dimensional bodies can be produced simply and rapidly by
repeatedly applying fresh layers of polymer powder and exposing the
fresh layers of polymer powder to the laser beam.
[0005] The process of laser sintering (rapid prototyping) to
produce moldings from pulverulent polymers is described in detail
in U.S. Pat. No. 6,136,948 and WO 96/06881. A wide variety of
polymers and copolymers are disclosed to be useful in this
application, including for example polyacetate, polypropylene,
polyethylene, ionomers, and nylon-11.
[0006] Nylon-12 (PA 12) powder has proven particularly successful
for producing engineering components by industrial laser sintering.
Parts manufactured from PA12 powder meet high mechanical
requirements and have properties nearly the same as those of parts
produced by mass-production techniques such as injection molding or
extrusion.
[0007] A material particularly well suited is nylon-12 with a
melting point of from 185 to 189.degree. C., an enthalpy of fusion
of 112.+-.17 J/g, and a solidification point of from 138 to
143.degree. C., as described in EP 0 911 142 (incorporated herein
by reference). It is preferable to use powders whose median
particle size is from 50 to 150 .mu.m, for example those obtained
as in DE 197 08 946 or else DE 44 21 454 (each of which is
incorporated herein by reference).
[0008] The SLS process however suffers from high equipment costs,
in particular the cost of the laser. Further, the processing speed
in laser sintering is relatively slow because large areas have to
be scanned by a point light source. These disadvantages have
inhibited wide adoption of this process for producing
computer-designed objects, and therefore the application of the SLS
process currently remains restricted to rapid prototyping. An
additional problem with SLS is the process' inability to process
colored powders, especially dark-colored powders.
[0009] Processes which are capable of use in both rapid prototyping
and for manufacturing common household goods have to be
significantly simpler to carry out in comparison to SLS, and should
in particular be capable of operating without the expensive and
complicated apparatus and starting materials required in the
conventional process.
[0010] Koshnevis (WO 01/38061) has developed a process in which a
mass is built up of layers of a powder to be bonded (sintered).
After the application of each powder layer, selected regions of the
layer are treated with a bonding inhibitor so that bonding takes
place only in the regions of the cross section of the
three-dimensional article. Bonding (sintering) may take place after
each treatment of a layer with a bonding inhibitor. However, it is
also possible to sinter the mass, e.g. in an oven, after all of the
layers have been completed. Since the regions which are bonded are
only those which have not come into contact with the bonding
inhibitor, the result is a three-dimensional body having a layered
structure.
[0011] WO 01/38061 mentions polymer powders and metal powders
generally as matrix materials. The disadvantage with most polymer
powders is relatively high shrinkage, arising in particular during
the sintering of polymer powders. The processing temperatures of
some polymer powders are moreover unsuitable in sintering because
the high temperatures required during processing can cause
technical problems during processing.
SUMMARY OF THE INVENTION
[0012] Accordingly, it is an object of the present invention to
provide polymer powders which are particularly well suited for use
as a matrix material in the process described in WO 01/38061, for
producing three-dimensional objects by means of selective
inhibition of bonding.
[0013] Surprisingly, it has been found that powders in which
polymers or copolymers selected from polyester, polyvinyl chloride,
polyacetal, polypropylene, polyethylene, polystyrene,
polycarbonate, PMMA, PMMI, ionomer, polyamides, copolyester,
copolyamides, terpolymers, or acrylonitrile-butadiene-styrene
copolymers (ABS), or a mixture of these, is present, and which have
a median particle size of from 10 to 200 .mu.m, are particularly
well suited for producing three-dimensional objects by means of
selective inhibition of bonding, in particular in processes in
which the bonding takes place via radiated heat (sinter
processes).
DETAILED DESCRIPTION OF THE INVENTION
[0014] The present invention therefore provides a process for
producing a three-dimensional object, which includes:
[0015] a) providing a layer of pulverulent material,
[0016] b) applying, bonding inhibitors to selected regions of the
layer from a), the manner of selection of the regions on which the
bonding inhibitor is placed being in accordance with the cross
section of the three-dimensional object, and specifically being
such that bonding inhibitors are applied only to the regions which
are not part of the cross section of the three-dimensional
object,
[0017] c) repeating steps a) and b) until all of the
cross-sectional areas of which the three-dimensional object is
composed form a matrix, and the outer boundaries of the object are
formed by the interface between pulverulent material with applied
bonding inhibitor and untreated pulverulent material, and
[0018] d) treating the layers at least once so that bonding takes
place between pulverulent material not provided with a bonding
inhibitor,
[0019] wherein the pulverulent material has a median particle size
of from 10 to 200 .mu.m and is at least one polymer or copolymer
selected from polyester, polyvinyl chloride, polyacetal,
polypropylene, polyethylene, polystyrene, polycarbonate, polymethyl
methacrylate (PMMA), poly(N-methylmethacrylimide) (PMMI), ionomer,
polyamides, copolyester, copolyamides, terpolymers, or
acrylonitrile-butadiene-styrene copolymers, or a mixture of
these.
[0020] The present invention also provides a molding produced by
the process of the invention, and pulverulent material which is
suitable for use in a process of the invention. Moldings may be
sintered shaped bodies.
[0021] By using pulverulent material which has a median particle
size of from 10 to 200 .mu.m, and in which at least one polymer or
copolymer selected from polyacetal, polyvinyl chloride,
polypropylene, polyethylene, polystyrene, polycarbonate, PMMA,
PMMI, ionomer, polyamides, or a mixture of these, is present,
components thus produced have the advantage of exhibiting
significantly less shrinkage than components composed of polymer
materials which do not meet the abovementioned requirements. The
use of pulverulent material within the stated boundaries permits
adjustment of the roughness of the surfaces of the moldings
produced therefrom.
[0022] The use of amorphous or semicrystalline polymers or
copolymers whose melting point is above 85.degree. C. and below
200.degree. C. can substantially eliminate any high degree of
shrinkage. Furthermore, the use of pulverulent materials where the
melting point of the polymers or copolymers is between 85 and
200.degree. C. can make it unnecessary to use an apparatus of
complicated design and expensive materials for constructing the
apparatus, in particular in relation to thermal insulation or
thermal conductivity.
[0023] Depending on the inhibitor system used in the process, there
may be a preference for some polymers or polymer mixtures. The use
of pulverulent material with the specified parameters in the SIB
process ensures problem-free treatment of the material with
inhibitor without any risk that the inhibitor will wet the
pulverulent material outside the desired region, as can, for
example, be the case if the bulk density of the pulverulent
material is too low.
[0024] The present process is unlike the known laser-sintering
(SLS) process, insofar as the present process permits production of
prototypes or short production runs from materials that comprise
colored pigments thereby allowing the mass produced resin to be
produced on a small scale or prototype scale. In contrast, when an
SLS process is used, the use of dark-pigmented material is
impossible due to the use of a laser.
[0025] The process of the invention is described below by way of
examples, that are not intended to limit the invention.
[0026] The process of the invention for producing a
three-dimensional object, includes
[0027] a) providing or applying a layer of pulverulent
material,
[0028] b) applying one or more bonding inhibitors to one or more
selected regions of the layer from a), the manner in which the
bonding inhibitor is placed on the layers corresponding to the
cross section of the three-dimensional object to be produced,
application is specifically such that bonding inhibitors are
applied only to the regions which are not part of the cross section
of the three-dimensional object,
[0029] c) repeating steps a) and b) until all of the
cross-sectional areas form a matrix, and the outer boundaries of
the object are formed by the interface between pulverulent material
with applied bonding inhibitor and untreated pulverulent material,
and
[0030] d) treating the layers at least once so that bonding takes
place between pulverulent material to which no bonding inhibitor
has been applied,
[0031] wherein the pulverulent material has a median particle size
of from 10 to 200 .mu.m and contains at least one polymer or
copolymer selected from polyester, polyvinyl chloride, polyacetal,
polypropylene, polyethylene, polystyrene, polycarbonate, PMMA,
PMMI, ionomer, polyamides, copolyester, copolyamides, terpolymers,
or ABS, or a mixture of these. The pulverulent material may contain
only the copolymer or polymer, or may contain additional materials.
The process of the invention is based on the process described in
WO 01/38061 (expressly incorporated herein by reference). WO
01/38061 provides a detailed description of the functional
principle of the SIB process.
[0032] A consequence of the application of the bonding inhibitor in
step b), which is usually computer-controlled, using CAD
applications to calculate the cross-sectional areas, is that only
untreated powder particles are bonded in a subsequent treatment
step. The inhibitor is therefore only applied to selected regions
of the layer from a) where these regions are not part of the cross
section of the three-dimensional object to be provided, but rather
surround the cross-sectional areas. One example of a method of
applying the pulverulent material is with use of a printing head
provided with nozzles. After the final treatment step d), the
process of the invention gives a matrix with, in part, bonded
pulverulent material, revealing the solid three-dimensional object
after removal of the non-bonded powder.
[0033] The pulverulent layer may be provided by physical or
chemical processes. Physical processes include pouring and/or
forming and chemical processes include such processes as chemical
vapor deposition.
[0034] Depending on the manner in which the process of the
invention is carried out, treatment may be carried out after each
or repeated steps b), and/or after step c). The sequence in
relation to the treatment in step d), i.e. the bonding of the
pulverulent material, depends on the physical or chemical process
used to bond at least some of the pulverulent material. If the
treatment in step d) is intended to take place after step c), it
has to be ensured that reaction can take place between the
pulverulent material not treated with bonding inhibitor in all of
the layers. When the process is carried out in this way, the
preferred method of bonding the pulverulent material uses heat, a
chemical reaction, or a thermally initiated chemical reaction. The
use of photons, e.g. UV radiation for crosslinking of pulverulent
particles, takes place preferably in those embodiments of the
process of the invention in which step d) takes place after every
step b).
[0035] Available physical processes are any of the processes which
permit simultaneous or near-simultaneous bonding of pulverulent
material in one or more layers, with the exception of the
pulverulent material to which an inhibitor has been applied.
Particularly preferred physical processes are those processes in
which at least a part of the pulverulent material is sintered or
melted. Preferred processes utilize an increase in the temperature
which may be achieved by irradiation, in particular using photons,
radiated heat, or microwave radiation, by increasing the ambient
temperature, by increasing the pressure, and/or by chemical
reaction.
[0036] Available chemical processes are likewise various chemical
reaction processes which permit bonding of at least a part of the
pulverulent materials to which an inhibitor has not been applied.
These reaction processes may in particular lead to the formation of
covalent or ionic bonds between molecules or elements of one or
more powder particles with molecules or elements of one or more
adjacent powder particles. Examples of suitable reactions are any
of the well-known crosslinking reactions or polymerization
reactions. Examples of these reactions include free-radical or
ionic polymerization, esterification reactions, polyaddition, or
polycondensation.
[0037] Treating the pulverulent material to cause bonding may also
include a combination of chemical and physical processes. For
example, the pulverulent material may, at least in part, have
reactive groups at the surface which react with one another on
heating. When such groups are present, a material which inactivates
the reactive groups even without heating may be used as an
inhibitor.
[0038] Bonding inhibitors include, inter alia, those described in
WO 01/38061. For example, inhibitors against bonding induced by
radiated heat are particles which reflect radiated heat, for
example, metallic inks, silver pigment, or reflective powder, or
thermally insulating particles, e.g. ceramic powder or ceramic
dispersions. Sintering inhibitors for polymers include oils,
alcohols, or waxes having sufficiently high viscosity to form a
coherent film around the pulverulent material to inhibit the
sintering-together of the pulverulent materials at the sintering
temperature. The process of the invention can also use bonding
inhibitors whose inhibition of bonding is achieved by forming
mechanical barriers between the particles to be melted, or by
forming insulating regions between the particles to be fused.
[0039] Oils, alcohols, or waxes may likewise be used as inhibitors
for chemical reactions. For example, the surface of the pulverulent
materials of selective regions of the individual layers may be
hydrophobicized, or else hydrophilicized, using one or more of an
oil, alcohol, hydrocarbon, water, or another suitable compound,
e.g. a silane. If the entire matrix of built-up layers is finally
treated with a crosslinking agent, e.g. with an adhesive, e.g.
applied by pouring or spraying of the adhesive, or by immersing the
matrix in the adhesive, and if the adhesive has hydrophilic or,
respectively, hydrophobic properties, bonding then takes place only
between the pulverulent materials to which no inhibitor has been
applied.
[0040] Another example of a suitable inhibitor is hydrogen
peroxide, which may react with a polymer used as pulverulent
material to alter the surface chemistry of the polymer. It is also
possible to use brine as inhibitor. Application of brine leads to
the formation of crystals on the particle surface of the
pulverulent materials, thereby acting as a chemical, or physical,
separator.
[0041] Another suitable inhibitor is water, which may comprise
additional materials to improve wetting, e.g. surfactants, of the
pulverulent material. The water may inhibit physical bonding of the
particles, e.g. because the particles do not melt immediately when
exposed to heat in the regions where the particles have been
treated with water, but instead remain pulverulent due to the
cooling action of the vaporizing water, and therefore do not bond.
The use of water can also inhibit chemical reactions. For example,
water, or a mixture comprising water, e.g. a water/surfactant
mixture, may be used in particular to inhibit anionic
polymerization in cases where anionic polymerization is the
reaction bonding the particles.
[0042] Examples of other inhibitors include dyes which, for
example, can serve as filters for radiation of a particular
wavelength, and thus can inhibit bonding of the particles.
[0043] The pulverulent material used preferably comprises a
pulverulent material which has been produced by grinding,
precipitation, and/or anionic polymerization, or any combinations
of these, specifically precipitation of a powder of somewhat too
coarse particle size, and subsequent milling, or precipitation, and
subsequent classification.
[0044] It is particularly preferred that the pulverulent material
has a median particle size (d.sub.50) of from 10 to 200 .mu.m,
particularly preferably from 20 to 100 .mu.m, and very particularly
preferably from 40 to 70 .mu.m. Any range or subrange within 10 to
200 .mu.m may be used, e.g., 10-20, 20-40, 20-100, 100-200, 50-150,
10-15 etc. Depending on the intended use, it can be advantageous to
use pulverulent materials which comprise particularly small and
particularly large particles. In order to obtain three-dimensional
articles with maximum resolution and maximum surface smoothness, it
can be advantageous to use particles whose median particle size is
from 10 to 45 .mu.m, preferably from 10 to 35 .mu.m, very
particularly preferably from 20 to 30 .mu.m.
[0045] The pulverulent material particularly preferably comprises a
polyamide, in particular nylon 12, preferably prepared as described
in DE 197 08 946, or else DE 44 21 454 (each of which is
incorporated herein by reference), and particularly preferably
having a melting point and an enthalpy of fusion as given in EP 0
911 142 (incorporated herein by reference), or comprise a
copolyamide or copolyester, e.g. as obtainable with the trademark
VESTAMELT.RTM. from Degussa AG. The pulverulent material may
consist of only nylon-12 or may contain other materials.
[0046] Fine material of size below 20 .mu.m, in particular below 10
.mu.m, is difficult to process, because it does not flow freely,
and the bulk density falls drastically, with the possible result
that more cavities are produced. To ease handling, it can be
advantageous to use particles whose median particle size is from 60
to 200 .mu.m, preferably from 70 to 150 .mu.m, and very
particularly preferably from 75 to 100 .mu.m. These pulverulent
materials may also preferably comprise a polyamide, in particular
nylon 12, or comprise a copolyamide, and/or a copolyester, as
described above. If significantly coarser powder is used the layer
thickness may conflict with particle size and result in
insufficient resolution.
[0047] The particle size distribution may be selected as desired
for the stated median particle sizes of the pulverulent materials.
Preference is given to the use of pulverulent materials which have
a broad or narrow particle size distribution, preferably a narrow
particle size distribution. Mixtures of particles having different
particle size distribution may be used (e.g., polymodal
distribution). Particularly preferred pulverulent materials for use
in the process of the invention have a particle size distribution
in which, based on the median particle size, a particle size
deviation of more than 50% is present in not more than 20% of the
particles, preferably 15%, and very particularly preferably not
more than 5%. The particle size distribution can be adjusted by
conventional classification methods, e.g. pneumatic separation.
Maximum narrowness of particle size distribution in the process of
the invention gives three-dimensional objects in which the surface
is very uniform and any pores present are very uniform.
[0048] At least a part of the pulverulent material used may be
amorphous, crystalline, or semicrystalline. Preferred pulverulent
material has a linear or branched structure. Particularly preferred
pulverulent material has, at least in part, a melting point of from
50 to 350.degree. C., preferably from 70 to 200.degree. C. The
inhibition of sintering procedures via the use of oils, alcohols,
hydrogen peroxide, water, or brine is very possible in these
temperature ranges.
[0049] In the process of the invention it is very particularly
preferable to use a pulverulent material in which a polyamide,
preferably at least one of nylon 6, nylon 11, and/or nylon 12, or a
copolyester, or a copolyamide, is present. Polyamides can produce
three-dimensional moldings which are particularly dimensionally
stable. Particular preference is given to nylon 12 powder, e.g. as
described in EP 0 911 142. Preferred copolyamides or copolyesters
used are those obtainable with the trademark VESTAMELT from Degussa
AG. Particularly preferred copolyamides are those having a melting
point of from 76 to 159.degree. C., preferably from 98 to
130.degree. C., and very particularly preferably from 110 to
123.degree. C., determined by differential scanning calometry
(DSC). Examples of methods of preparing the copolyamides include
polymerization of mixtures of suitable monomers, e.g. those
selected from laurolactam and/or caprolactam, as bifunctional
component, suberic acid, azeleic acid, dodecanedioic acid, adipic
acid, and/or sebacic acid as component bearing an acid function,
and 1,6-hexanediamine, isophoronediamine and/or
methylpentamethylenediamine as diamine.
[0050] In order to achieve better processibility of the pulverulent
materials, it can be advantageous to use a pulverulent material
which comprises additives. Examples of these additives include flow
aids. The pulverulent material particularly preferably comprises
from 0.05 to 5% by weight, with preference from 0.1 to 1% by
weight, of additives. Examples of flow aids include fumed silicas,
stearates, or other flow aids known from the literature, e.g.
tricalcium phosphate, calcium silicates, Al.sub.2O.sub.3, MgO,
MgCO.sub.3, or ZnO. An example of fumed silica is supplied with the
trademark AEROSIL.RTM. by Degussa AG.
[0051] Together with, or instead of, these flow aids, inorganic
fillers may also be present in a pulverulent material used
according to the invention. Fillers have the advantage that they
may substantially retain their shape through the treatment during
the bonding process, and thereby reduce shrinkage in the
three-dimensional object. In addition, the use of fillers permits,
for example, alteration of the plastic properties and physical
properties of the objects. For example, the transparency and color
of the object, and/or its magnetic properties, can be adjusted by
using pulverulent material which comprises metal powders. By way of
example, glass particles, ceramic particles, or metal particles may
also be present as fillers in the pulverulent material. Typical
fillers include granular metals, aluminum powders, steel shot, or
glass beads. It is particularly preferable to use pulverulent
materials which comprise glass beads as fillers. In one preferred
embodiment, the pulverulent material of the invention comprises
from 1 to 70% by weight of fillers, preferably from 5 to 50% by
weight, and very particularly preferably from 10 to 40% by weight.
All ranges and subranges including for example 1-2,2-4, 5-10,
10-20, 20-40, 25-50 etc. are included.
[0052] Together with, or instead of, inorganic flow aids or
fillers, inorganic or organic pigments may also be present in the
pulverulent material. These pigments may be not only color pigments
which determine the perceived color of the three-dimensional body
to be generated, but may also be pigments that affect other
physical properties of the three-dimensional articles, examples
include magnetic pigments, and/or conductivity pigments, e.g.
conductivity-modified titanium dioxide or tin oxide, which alter
the magnetic properties and, respectively, the conductivity of the
article. The pulverulent material particularly preferably comprises
inorganic or organic color pigments selected from chalk, ochre,
umber, green earth, burnt sienna, graphite, titanium white
(titanium dioxide), white lead, zinc white, lithopone, antimony
white, carbon black, iron oxide black, manganese black, cobalt
black, antimony black, lead chromate, minium, zinc yellow, zinc
green, cadmium red, cobalt blue, Prussian blue, ultramarine,
manganese violet, cadmium yellow, Schweinfurter green, molybdate
orange, molybdate red, chrome orange, chrome red, iron oxide red,
chromium oxide green, strontium yellow, metallic-effect pigments,
pearlescent pigments, luminescent pigments using fluorescent and/or
phosphorescent pigments, umber, gamboge, animal charcoal, Cassel
brown, indigo, chlorophyll, azo dyes, indigoids, dioxazine
pigments, quinacridone pigments, phthalocyanine pigments,
isoindolinone pigments, perylene pigments, perinone pigments, metal
complex pigments, alkali blue pigments, and dicetopyrrolopyrrole.
Further information concerning pigments which may be used may be
found in, for example, Rompp Lexikon Chemie [Rompp Chemical
Encyclopedia]--Version 2.0, Stuttgart/New York: Georg Thieme Verlag
1999, and also in the references given in that publication. The
particle sizes of the pigments used may be those described for the
pulverulent material. However, the pigments frequently have
particle sizes significantly smaller than the median particle sizes
of the polymers used. The pigments may, for example, be applied in
a manner similar to that for the bonding inhibitors such as through
nozzles used in printing heads, or may be present in the polymer
particles. The pulverulent material of the invention particularly
preferably comprises polymer particles which comprise one or more
of the pigments mentioned--preferably with the exception of white
pigments alone. The proportion of the pigments in the pulverulent
material is preferably from 0.01 to 25% by weight, preferably from
0.1 to 10% by weight, and particularly preferably from 1 to 3% by
weight.
[0053] In the process of the invention, the moldings produced
therefrom may have one or more functionalized layers. By way of
example, functionalization, e.g. the provision of conductive
properties to the entire molding, or else only to certain regions,
may take place by applying appropriate pigments or substances to
the layer or pulverulent material, using a method similar to that
for the inhibitor.
[0054] One embodiment of the process of the invention, use includes
of bonding inhibitors whose action is only temporary. These bonding
inhibitors may be frames, plates, sheets, or glass materials of
various shape, where these may comprise two or more parts, and
where, after application of the powder, bonding inhibitors
protectively cover regions of the powder layer in the manner of a
frame. By using a large number of different shapes, or by using
flexible shapes which can be adapted by computer control to the
area to be protectively covered, it is possible to provide
protective covering for almost any conceivable cross-sectional
area. The pulverulent material in the area not protectively covered
is bonded, together and to adjacent underlying layers, by exposure
to radiation, in particular radiated heat, or by spraying with a
chemical. The temporary bonding inhibitors are then removed, and a
fresh layer of pulverulent material is applied. This embodiment of
the process of the invention also gives a three-dimensional article
by repeating the steps of the process as required by the number of
cross-sectional areas. The pulverulent materials used may be the
abovementioned materials.
[0055] Moldings which can be produced by the process of the
invention can have any desired three-dimensional shape which can be
formed by layers. The molding particularly preferably comprises a
nylon 12, a copolyamide, or a copolyester. Moldings produced using
the process of the invention preferably comprise at least one
filler selected from glass beads or aluminum powder. Moldings which
can be produced by means of the process of the invention are in
particular those whose color is neither white nor transparent (nor
transparent with a milky or yellowish effect). Moldings with these
colors cannot be produced using conventional laser-sintering
processes, because the color pigments impair the supply of energy
by the laser. The moldings produced according to the invention may
also have functionalized layers. Besides functionalization through
pigments, there may also be compounds with particular functional
properties present in one or more of the layers, or in the entire
molding. An example of functionalization may consist in provision
of electrically conducting properties to the entire molding, to one
or more layers of the molding, or else only to parts of one or more
layers of the molding. This functionalization may be achieved
through conductive pigments, e.g. metal powders, or through the use
of conductive polymers, e.g. polyaniline. Moldings which have
conductor tracts can be obtained in this way, and these may be
present either on the surface or else within the molding.
[0056] The present invention also provides the pulverulent material
as described above, suitable for use in the process of the
invention, and in which, in particular, the median particle size is
from 10 to 200 .mu.m, and in which at least one polymer or
copolymer selected from polyvinyl chloride, polyester, polyacetal,
polypropylene, polyethylene, polystyrene, polycarbonate, PMMA,
PMMI, ionomer, polyamides, copolyester, copolyamides, terpolymers,
or ABS, or a mixture of these, is present. The powder particularly
preferably comprises nylon 12, a copolyamide, or a copolyester, or
a mixture of these. The powder particularly preferably comprises
polymer particles which have been colored, their color being other
than white.
EXAMPLES
[0057] Triangular objects with edge length 50.times.50 mm were
produced by means of the process of the invention for the selected
inhibition of bonding. For this, a square metal frame with internal
dimensions of 50 mm and external dimensions of 100 mm, with a
thickness of 1 mm, was placed on a continuous metal plate. The
resultant aperture was then filled with powder and another metal
plate was used for smoothing. One half of the rectangle was then
protectively covered, using a flexible metal plate. The remaining
powder surface was then uniformly wetted, by spray-application,
using an air-brush gun, with water which had been treated with 10%
by weight of a washing composition (Pril, Henkel). After removal of
the protective covering, the entire powder layer was heated for 2
and, respectively, 5 seconds at a distance of 2 cm from a radiant
heater from the company AKO, having a power rating of 1000 watts.
This gave a powder layer including, as component, a triangular
structure comprising sintered powder. The powder which was present
around the component and which was treated with the water
comprising washing composition during the production process
remained in powder form. The component could be removed without
difficulty from the powder layer. Table 1 below lists the powders
tested, and the results of the experiments. TABLE-US-00001 TABLE 1
Melting point Pulverulent (DSC) material Trade name in .degree. C.
Result Copolyamide Vestamelt X1310 110 No curl, good sinterability,
sharp edges PA12 EOSINT PA 186 Good sinterability, slight curl 2200
PA612 Vestamid D16 216 Sinterable Copolyester Vestamelt 4481 107
Good sinterability Copolyamide Vestamelt 840 113 Very good
sinterability, the inhibitor-covered parts also sintered when using
5 seconds of irradiation; when using 5 seconds and a distance of 10
cm, edges were not sharp PE Vestolen A6016 Good sinterability, curl
EPVC Vestolit P1403 K Sinterable, discoloration MPVC Vestolit P2004
Sinterable, KF discoloration
[0058] The abbreviations MPVC and EPVC indicate the PVC production
method: MPVC represents mass-polymerized polyvinyl chloride, and
EPVC represents emulsion-polymerized polyvinyl chloride. PE
represents polyethylene.
[0059] The products with the Vestamelt and Vestamid can be
purchased from Degussa AG. The product EOSINT PA 2200 can be
purchased from EOS GmbH Electro Optical Systems. The product
Vestolen is obtainable via Sabic EPC, and the products with the
name Vestolit are obtainable via Vestolit GmbH & Co KG. The
abovementioned product names are registered trademarks of the
respective stated companies, with the exception of the name
Vestolen, which is registered as a trademark of DSM Polyolefin
GmbH, Gelsenkirchen, Germany.
[0060] German applications 10244047.6 and 1031146.7 filed on Sep.
21, 2002 and Mar. 15, 2003, respectively, are each incorporated
herein by reference in their entireties.
[0061] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *