U.S. patent application number 13/706756 was filed with the patent office on 2013-04-18 for material system and method for changing properties of a plactic component.
This patent application is currently assigned to VOXELJET TECHNOLOGY GHBH. The applicant listed for this patent is VOXELJET TECHNOLOGY GHBH. Invention is credited to Ingo Ederer, Daniel Gunther, Johannes Gunther.
Application Number | 20130092082 13/706756 |
Document ID | / |
Family ID | 40433748 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130092082 |
Kind Code |
A1 |
Ederer; Ingo ; et
al. |
April 18, 2013 |
MATERIAL SYSTEM AND METHOD FOR CHANGING PROPERTIES OF A PLACTIC
COMPONENT
Abstract
The instant invention relates to a method for changing
characteristics of a plastic component, wherein a medium is
introduced into the plastic component, which encompasses a porosity
and wherein the medium forms a homogenous compound with the plastic
component by at least partially dissolving the plastic
component.
Inventors: |
Ederer; Ingo; (Geltendorf,
DE) ; Gunther; Daniel; (Munchen, DE) ;
Gunther; Johannes; (Augsburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOXELJET TECHNOLOGY GHBH; |
Friedberg |
|
DE |
|
|
Assignee: |
VOXELJET TECHNOLOGY GHBH
Friedberg
DE
|
Family ID: |
40433748 |
Appl. No.: |
13/706756 |
Filed: |
December 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12681194 |
Apr 1, 2010 |
8349233 |
|
|
PCT/DE08/01593 |
Oct 1, 2008 |
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13706756 |
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Current U.S.
Class: |
118/641 ;
118/313; 118/320; 118/423 |
Current CPC
Class: |
C08J 2351/00 20130101;
C08J 7/18 20130101; B33Y 40/00 20141201; B05C 5/0283 20130101; B05C
3/005 20130101; B33Y 10/00 20141201; B29C 71/0009 20130101; B33Y
80/00 20141201; B05C 3/02 20130101; B33Y 70/00 20141201; C08J 9/405
20130101; C08J 7/02 20130101 |
Class at
Publication: |
118/641 ;
118/423; 118/320; 118/313 |
International
Class: |
B05C 3/02 20060101
B05C003/02; B05C 5/02 20060101 B05C005/02; B05C 3/00 20060101
B05C003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 11, 2007 |
DE |
10 2007 049 058.7 |
Claims
1.-10. (canceled)
11. A material system comprising at least: a building platform or
an applicator for producing a plastic component, wherein the
plastic component has a porosity, a device for introducing a medium
into the plastic component, a device for solidifying, the medium
introduced into the plastic component, and wherein the medium
includes at least one substance, which at least partially dissolves
the plastic component and which forms a homogenous compound
therewith.
12. The material system according to claim 11, wherein the medium
is a monomer.
13.-19. (canceled)
20. The material system according to claim 11, wherein the device
for introducing the medium into the plastic component is device for
dip infiltration.
21. The material system according to claim 20, wherein the device
for dip infiltration comprises: a. a dipping vat, b. a
liquid-permeable bracket for dipping of the plastic component the
dipping vat, c. a hold-down device for preventing floating of the
plastic component in the dipping vat, and d. infiltration
mixture.
22. The material system according to claim 21, wherein the
hold-down device for preventing the floating of the plastic
component in the dipping vat is a weight or a retainer clip.
23. The material system according to claim 21, wherein the dipping
vat is a container made out of chemically resistant high-grade
steel.
24. The material system according to claim 21, wherein the
infiltration mixture contains an accelerator.
25. The material system according to claim 21, wherein the
liquid-permeable bracket for dipping of the plastic component in
the dipping vat is a cage made out of wire.
26. The material system according to claim 21, wherein the dipping
vat contains a seal protecting the dipping vat from contamination
and radiation ingress.
27. The material system according to claim 20, wherein the device
for dip infiltration contains a cooling device.
28. The material system according to claim 11, wherein the device
for solidification of the introduced medium into the plastic
component comprises: a. a Ultra Violet (UV) radiation source, b. a
rotary table comprising one or a plurality of degrees of freedom
for moving the plastic component, and c. a bracket to hold the
plastic component.
29. The material system according to claim 28, wherein the bracket
to hold the plastic component is made out of wires.
30. The material system according to claim 11, wherein the device
for introducing a medium into the plastic component contains a jet
spray system to apply a wetting agent on to the plastic component
and a rotary table to rotate the plastic component
31. The material system according to claim 30, wherein the jet
spray system comprises one or a plurality of spray nozzles to
generate the wetting agent.
32. The material system according to claim 28, wherein the UV
radiation source is one or a plurality of UVA radiation tubes.
33. The material system according to clam 11, wherein a device for
solidification of the introduced medium into the plastic component
contains an initiating system.
34. A material system comprising at least: a building platform or
an applicator for producing a plastic component, wherein the
plastic component has a porosity; a device for introducing a medium
into the plastic component located downstream of the building
platform, so that the plastic component is completed on the
building platform and then transported to the device for
introducing the medium; wherein the device for introduction of a
medium into the plastic component comprises: a device for dip
infiltration, the device for dip infiltration comprising: a. a
dipping vat, b. a liquid-permeable bracket for dipping of the
plastic component in the dipping vat, and c. a hold-down device for
preventing floating of the plastic component in the dipping vat,
and d. an infiltration mixture; a device for solidifying the medium
introduced into the plastic component, wherein the device for
solidifying the medium introduced into the plastic component
comprises: a. a UV radiation source, b. a rotary table comprising
one or a plurality of degrees of freedom for moving the plastic
component, and c. a bracket to hold the plastic component; wherein
the medium includes at least one substance, which at least
partially dissolves the plastic component and which forms a
homogenous compound therewith.
35. The material system according to claim 34, wherein the bracket
to hold the plastic component is made out of wires.
36. The material system according to claim 35, wherein the
hold-down device for preventing the floating of the plastic
component in the dipping vat is a weight or a retainer clip.
37. The material system according to claim 36, wherein the plastic
component and the medium for introduction into the plastic
component are from the same class of chemicals.
Description
[0001] The invention relates to a material system as well as to a
method for changing the characteristics of a plastic component.
[0002] Plastic components encompassing a certain porosity are often
created in response to the use of generative three-dimensional
processes, such as the selective laser sintering or the
three-dimensional print process, for example.
[0003] A thin layer of a powdery element is applied to a building
platform in response to the selective laser sintering as well as in
response to a three-dimensional print process. Subsequently, a part
of the powder is selectively bonded, for example by means of
applying binding material. This selection corresponds to a cut
through the component, which is to be attained.
[0004] Subsequently, the building platform is lowered by a layer
thickness and is provided with a new layer of particulate material,
which is also solidified, as is described above. These steps are
repeated until a certain desired height of the object has been
reached. The imprinted and solidified areas thus create a
three-dimensional object. Such a method is known from DE 69634921,
for example.
[0005] Other powder-based rapid prototyping processes also operate
in a similar manner, for example the electron beam sintering,
whereby a loose particulate material is solidified selectively by
means of a controlled, physical source of radiation.
[0006] All of these methods will be combined herein below under the
term "generative three-dimensional processes".
[0007] The components produced by means of generative
three-dimensional processes oftentimes encompass a certain
porosity. For the most part, the porosity of the components is
conditional on the method of the selective bonding. The connection
by means of a laser beam corresponds to the sufficiently known
sintering. The grains of the powder connect at their contact points
by fusing together. The space between the grains remains open. The
conditions of components, in the case of which the selective
hardening is realized by metering a liquid (three-dimensional
printing), are similar. A porous body is created in the event that
the smallest possible quantity of liquid is metered as compared to
the powder mass per unit of space. This is known from DE 60008778,
for example.
[0008] Inadequate mechanical strength properties and
disadvantageous surface characteristics are oftentimes problematic
for the use of such porous components.
[0009] Similar to the known method for creating fiber reinforced
materials, the absorptive capacity of porous parts makes it
possible to introduce liquid media into the component.
[0010] It is thus known from DE 195 45 167 A1, for example, to
cover a pattern, which is produced by means of selective laser
sintering, with wax, so as to create a closed surface. Subsequent
dipping processes in liquid shaped material require a liquid-tight
part, so as to ensure the contour accuracy of the mold. What is
important here are the strength characteristics. The method uses
the thermal phase transition from solid to liquid and vice
versa.
[0011] Disadvantageous the component must be subjected to
considerable temperatures, depending on the infiltration material.
In most cases, infiltration materials comprising a low melting
point furthermore also encompass low mechanical properties.
[0012] In particular the characteristics of the used materials must
be considered in response to the configuration of prototypes by
means of the above-mentioned generative methods.
[0013] For example, it is known to use resins for the infiltration.
The resins are introduced into the porous body in the form of a
liquid and solidify in the component in the form of dispersion by
evaporating the solvent or as resin mixtures by means of a
polymerization. Such methods are known from WO 2005/82603 A1, from
U.S. Pat. No. 6,375,874 and from U.S. Pat. No. 5,616,294, for
example. Due to the necessity for the evaporation of the solvent,
such dispersions described in these documents are only suitable for
components comprising thin wall thicknesses. Due to the temperature
sensitivity for porous plastic components, thermal methods
following the example of wax infiltration are not very suitable to
increase the strength.
[0014] For the most part, polymerizing mixtures for infiltrating
are two-component systems, such as epoxy resins. Such mixtures
attain high mechanical strength properties. However, they do not
come close to the characteristics of commercially polymerized
products, such as PE, PET, PMMA, etc., for example.
[0015] Polymerizing mixtures, as they are known from the state of
the art, have the following limits.
[0016] The polymerizing infiltrate together with the porous
component or also with the matrix, forms a composite material,
which is weakened by the phase limits in the interior. The
mechanical properties of the components thus always lie below
values of the pure infiltrate.
[0017] Furthermore, one binding element and one resin element are
typically mixed with one another prior to the introduction into the
component in response to the use of a two-element system. The
polymerization then begins in a time-delayed manner. It is a
disadvantage of this method that once a mixture has been prepared,
it must be processed within a short period of time. A dipping
process, which provides for high quantities and for a high degree
of automation, can thus not be realized in an economical manner.
For the most part, the application is carried out by means of a
brush. This method cannot be automated and requires high degree of
effort in the case of complex geometries.
[0018] It is thus the objective of the present invention to provide
a method and a material system to increase mechanical properties of
a porous plastic component.
[0019] This objective is solved by means of a method for changing
characteristics of a plastic component, in the case of which a
medium, which encompasses a porosity, is introduced into the
plastic component, and the medium forms a homogenous compound with
said plastic component by at least partially dissolving it.
[0020] The objective is furthermore solved by means of a material
system comprising a medium for introducing into a plastic component
encompassing a porosity, in the case of which the medium
encompasses at least one substance, which at least partially
dissolves the plastic component and which forms a homogenous
compound therewith.
[0021] In particular in the case of generative three-dimensional
methods, such as the three-dimensional print process, high volume
outputs can be attained, when porous components are configured
intentionally.
[0022] The characteristics of the component can be improved
specifically by an infiltration after the three-dimensional
configuration, such as the printing, for example. The creation of
porous components, which are subsequently infiltrated, is
furthermore considerably less time-intensive than the creation of
components comprising a very high liquid introduction, which is
necessary to directly create leak-proof parts in the generative
method.
[0023] The mechanical properties of infiltrated components, which
can be attained, according to methods of the state of the art, are
oftentimes too low for prototypes, because the porous component
hereby forms a type of matrix and because the infiltrate fills the
cavities. This leads to a so-called inner notching effect between
the matrix and the infiltrate at the bounding surfaces, which
furthermore represents a considerable unstableness factor. The
strengths of the components thus vary highly. In addition,
infiltration methods known from the state of the art are very
labor-intensive and thus represent a serious production
bottleneck.
[0024] According to the instant invention, materials, which can
slightly dissolve the generatively created matrix and which thus
lead to a particularly homogenous material, are now used for the
infiltration. Slightly dissolving thus means that a homogenous
compound between the matrix and the medium, in particular
infiltrate, is formed.
[0025] According to a preferred embodiment of the method according
to the invention, the solidification of the introduced medium takes
place by means of polymerization.
[0026] According to a particularly preferred embodiment of the
instant invention, it can be advantageous for an outermost layer of
the plastic component to be solidified in an accelerated manner by
means of chemical and/or physical measures as compared to the
remaining plastic component.
[0027] Through this, it is possible to efficiently prevent a
possible loss of geometric shape caused by a softening of the
components in response to the connection of the component to the
medium.
[0028] The component is thereby solidified in an accelerated manner
in the outermost layer as compared to the remaining component
volume and a stable structure is thus created. The softening caused
by the slight dissolution of the matrix can thus not impact the
geometry. The outermost layer solidification could take place, for
example, by additionally applying accelerators and with the use of
polymerization media comprising radiation initiation.
[0029] "outermost layer" according to the instant invention refers
to the outer area of the component.
[0030] "Accelerated" could be defined in such a manner that a
solidification of an outermost layer occurs in a noticeably more
rapid manner than a solidification of the remaining body.
"Solidification" shall not be understood to mean that a complete
solidification has taken place. In terms of the invention, a
solidification that allows for the form stability, that is, a
stability that supports the dead weight, is oftentimes
sufficient.
[0031] According to an embodiment of the instant invention, the
accelerated solidification of the outermost layer could take place
with the use of two polymerization systems comprising different
reaction times.
[0032] In addition, it could also be advantageous when the
accelerated solidification of the outermost layer is reached with
the introduction of high-energy radiation, such as UV radiation or
microwave radiation, for example.
[0033] A further embodiment of the method according to the
invention represents the possibility of introducing the medium into
the plastic component by means of dipping into a vat of the
medium.
[0034] The porous component could thereby now be automatically
infiltrated in a dipping vat. The dipping vat itself does not
harden, so that a permanent and economical use of the dipping vat
is ensured.
[0035] However, the liquids of the dipping vat result in high
strength characteristics after the polymerization. The material of
the porous component forms a compound with the infiltrate, which is
similar to a homogenous material. The hardening of the resin should
advantageously take place within a period of a few minutes.
[0036] In the case of the method according to the invention, the
plastic component can furthermore be dipped into a vat comprising
an accelerator according to a preferred embodiment for hardening
the outermost layer.
[0037] According to the present invention it can furthermore be
advantageous when the component is rotated at least in response to
the introduction of medium and/or high-energy radiation.
[0038] This rotation could thereby take place about one or a
plurality of axes.
[0039] According to a particularly preferred embodiment, provision
could be made for a rotary table comprising one or a plurality of
degrees of freedom for moving the component. To ensure the influx
of the radiation in response to the use of the radiation curing,
the component is held in a bracket, for example made of wires,
which shields as little radiation as possible. A grate, which is
connected to an axis of rotation, represents a simple
embodiment.
[0040] A material system according to the instant invention
comprises a medium for introduction into a plastic component, which
encompasses a porosity. The medium thereby encompasses at least one
substance, which at least partially dissolves the plastic component
and which forms a homogenous compound therewith.
[0041] Preferably, the medium is hereby a monomer.
[0042] According to a particularly preferred embodiment, the medium
encompasses at least one part, which is from the same substance
class as a plastic part of the plastic component.
[0043] Preferably, a monomer is included in the medium as material.
Said monomer is also a part of the bond bridges or of the grains of
the matrix, thus of the plastic component, or a foreign monomer,
which, however, slightly dissolves the generatively created body.
Due to the slight dissolution by means of the liquid, the
generatively created body solidifies in a homogenous manner.
[0044] Due to the similarity of its characteristics with the base
material of the plastic component, such a medium or infiltrate can
penetrate particular deep into the component. Excess material drips
off the component and does not leave behind surface flaws. In the
event that a component of the polymerizing material is introduced
during the generative creation of the component, a dipping process
could preferably also be realized by means of a long term dipping
vat.
[0045] According to an embodiment of the instant invention, the
material system furthermore encompasses a catalyst and/or a cross
linking agent.
[0046] It can moreover be advantageous when provision is further
made for a photo initiator.
[0047] It could thereby be the case that provision is made for the
photo initiator in the medium.
[0048] According to an embodiment of the material system, the
plastic component and the medium encompass a methacrylate.
[0049] The material system according to the invention as well as
the method according to the invention can preferably be used for
infiltrating porous plastic components, in particular plastic
components produced by means of three-dimensional print
processes.
[0050] To elaborate in more detail, the invention will be described
in more detail below by means of preferred exemplary embodiments
with reference to the drawing.
[0051] FIG. 1 shows an non-infiltrated and infiltrated matrix;
[0052] FIG. 2 shows an infiltrated matrix according to an
embodiment of a method and of a material system of the instant
invention;
[0053] FIG. 3 shows an outermost layer hardening according to a
preferred embodiment of the instant invention;
[0054] FIG. 4 shows a dipping vat according to a preferred
embodiment of the instant invention;
[0055] FIG. 5 shows a dipping vat according to a further preferred
embodiment of the instant invention;
[0056] FIG. 6 shows the irradiation of the component according to a
preferred embodiment of the instant invention and a spray coat
method for applying a liquid according to a preferred embodiment of
the instant invention;
[0057] FIG. 7 shows a bracket according to a preferred embodiment
of the instant invention.
[0058] According to the instant invention, a medium 5 is to be
introduced into a plastic component 10. A porous component 10 forms
the basis for this.
[0059] As can be seen in FIG. 1, a porous component 10 or the
matrix 4, respectively, are formed by grains 1 and by connecting
bridges 2 and the cavities 3 or pores, respectively, of the matrix
4 are located between the grains 1.
[0060] The instant invention relates to bodies, the grains of which
consist of plastic. The bridges 2 of the matrix 4 can consist of a
material, which is similar or not similar to the grains 1.
[0061] The connecting bridges 2 between the grains 1 can be created
by means of different methods in response to the formation of the
plastic component 10 or matrix 4, respectively. In the case of
components, which have been produced by means of the laser
sintering process, the bridges 2 are created from molten material,
which is created by means of the heat exposure of the laser beam.
This means that the bridges 2 are formed from the material of the
grains 1.
[0062] By means of three-dimensional print methods, bridges 2 can
be formed from the material of the grains 1, for example by
metering a solvent, as well as from a further material, for example
by introducing a polymerizing liquid.
[0063] Preferably, porous plastic component are used, in the case
of which the bridges 2 and the material of the grains 1 belong to a
chemically similar plastic system.
[0064] The porosity of the component can be controlled within
certain limits via the temperature control in response to the laser
sintering process and via the metered quantity of the bonding agent
in response to the three-dimensional printing.
[0065] Preferably, a liquid medium is used according to the
invention, the chemical composition of which corresponds to the
material system of grains 1 and bridges 2. After the wetting of the
porous body, the medium 5 permeates into the cavities 3 by means of
a capillary effect. A leak-proof body is created by means of the
solidification of the medium or of the infiltrate 5,
respectively.
[0066] Excess material 5 drips off from the surface 6 of the
component 10 after the solidification and the plastic component has
a smoother surface than in the non-infiltrated state.
[0067] It is illustrated in FIG. 2 that according to the instant
invention, it has proven to be advantageous for attaining high
strengths for the medium 5 to encompass a separation force relative
to the matrix 4. Said separation force should be considerable. By
means of such a medium 5 it is possible to slightly dissolve 7 the
grains 1 and bridges 2 and to thus form a homogenous compound in
response to the solidification.
[0068] Preferably, the medium 5 encompasses monomers, which
solidify in or with the component 10, respectively, if applicable
with the addition of auxiliary materials by forming molecular
chains/structures.
[0069] The polymerization can thereby take place by means of the
reaction types polyaddition, polycondensation, radical and ionic
polymerization or ring opening polymerization. Depending on the
purpose of application, homopolymers, as a chain of a monomer, or
copolymers can be used by means of the polymerization of different
monomers.
[0070] The used monomers preferably encompass a low viscosity.
Depending on the reaction type, the medium 5 includes further
components in addition to different monomers. Among others,
reaction-initiating initiators, accelerating catalysts and
strength-increasing wetting components can be added to the medium
5. These substances can furthermore be used to control the reaction
process. In addition, reaction-inhibiting substance-inhibitors can
be included.
[0071] The components, which are necessary to form a polymerizing
substance, can be introduced in separate phases of the workpiece
creation. Initiating components or catalysts in the powder or the
grains 1, respectively, or the bridges 2 of the component 10 can be
introduced in response to the generative construction process.
These components can fulfill a chemical function either in the
construction process and in response to the infiltration or two
separate systems are realized. According to a preferred embodiment
of the invention, as is shown in FIG. 3, a slight matrix
dissolution is carried out in response to the method according to
the invention and a stabilization of the outermost layer 8 of the
component 10 is created. Preferably, this is attained by means of
two polymerization systems, which react in a chronologically
separate manner. The rapid system generates a thin, solid outermost
layer 8 in preferably only a few seconds.
[0072] Due to the fact that the reaction heat causes the
temperature in the component to increase to a high degree in
response to a rapid, complete hardening of the component 10, a
thermal softening of the component can occur. The second reaction,
which solidifies the main part or the "inner" part, respectively,
of the material volume 9 (main reaction), thus takes place within a
larger time frame.
[0073] An initiating system, which is bound in the powdery material
or which is present on the surface thereof, which is thus
introduced during the generative creation of the component, is
preferred for the second polymerization reaction.
[0074] A system, in the case of which the powdery material, which
forms the porous component, consists of polymethylmethacrylate
(PMMA) or polyethylmethacrylate (PEMA) is particularly preferred.
The grain contains the initiator benzoyl peroxide (BPO). The BPO
can be made accessible for the reaction via the dissolving effect
of the monomer in the infiltration liquid as compared to the
grain.
[0075] A system for initiating by means of ethyl barbituric acid is
likewise preferred. A PMMA or PEMA grain is coated therewith.
[0076] An element (initiator or catalyst/accelerator), which is
required for the independent hardening, is missing in the liquid
for infiltrating, the medium 5. The infiltrate 5 thus only hardens
in contact with the component 10. It can thus be kept ready in a
vat for an automated dipping infiltration.
[0077] A mixture of a monomer or a monomer mixture and a catalyst
is preferred for the infiltration. In addition, a wetting agent can
be added. Monomers comprising a low viscosity are particularly
suitable here. Together with the initiator in the component, the
result is a mixture, which can be polymerized.
[0078] A mixture of 2-hydroxyethylmethacrylate (HEMA) and
N,N-dimethyl-p-toluidine (DMPT) is particularly preferred. HEMA
thereby acts as monomer and DMPT acts as catalyst, which
accelerates the initiation by the BPO from the grain.
[0079] Wetting agents are added to control the reaction heat in
response to the main solidification.
Ethyleneglycol-dimethylmethacrylate (EGDMA), which reduces the
reaction speed under certain reaction conditions, is preferred.
[0080] A mixture of HEMA and copper-acetyl-acetonate (CuAA) is
likewise preferred. Through this, a system comprising ethyl
barbituric acid-coated grains can be initiated.
[0081] The accelerated solidification of the edge area 8 can be
attained in different ways. On the one hand, a liquid component can
be used. Said liquid component can contain an initiator or catalyst
in a high quantity, as compared to the actual infiltration mixture.
On the other hand, a component, which can be activated by means of
irradiation, can be added to the infiltration mixture. Furthermore,
one component can be available in a gaseous form and can thus
evenly come in contact with all of the edges of the component.
[0082] The use of a liquid component takes place in an additional
dipping step, which follows the actual infiltration. In the case of
the additional liquid, a catalyst or an initiator can be used. The
catalyst DMPT in the case of a grain comprising BPO and/or CuAA is
preferred for the outermost layer hardening by means of a liquid in
the case of an ethyl barbituric acid system, into which the
component is dipped. Due to the low diffusion in the component,
only one outermost layer is solidified when proceeding in this
manner.
[0083] As is shown in FIG. 6, the wetting of the outermost layer 8
can be carried out by means of a jet spray system instead of by
means of a dipping method. For this purpose, the component 10 is
rotated on a rotary table 19, for example. One or a plurality of
spray nozzles 21 generate a mist from the liquid component so as to
activate the polymerization of the outermost layer.
[0084] As an expansion of the above-mentioned system
(polymerization system comprising two different initiator
concentrations), a polymerization system comprising a plurality of
independent initiator systems can be used to better control the
individual desired reactions. A grain, which is coated with ethyl
barbituric acid and which contains BPO in the interior, represents
one exemplary embodiment. By adding the catalysts CuAA or DMPT, a
system can now specifically be made to react. In addition, a photo
initiator can also serve as a second initiation system.
[0085] A photo initiator of the type diphenyl
(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) is preferred for the
radiation hardening. With the help of this initiator, radicals for
the polymerization can be generated by means of UV radiation. All
of the radiation types of UVA, UVB to UVC can be used. UVA
radiation is preferred for the hardening.
[0086] For the infiltration, see FIG. 4, the component 10 is dipped
into a vat 12 comprising the liquid components 11. All of the
elements, which form a mixture that is capable of reaction and
polymerization with the element in the component 10, are located in
the vat. The essential demand on the mixture is for the elements in
the vat without the element in the component to not react and
solidify or to only slowly react and solidify.
[0087] According to the above explanations, an infiltration mixture
consisting of 79% HEMA, 20% EGDMA, 0.5% DMPT, 0.5% TPO is
particularly preferred.
[0088] The device for dip infiltration includes a vat 12, a
liquid-permeable bracket 16 for dipping and a hold-down device 17,
18, which prevents the floating of the component in the dipping vat
(see FIGS. 4 and 5).
[0089] The dipping vat consists of a chemically resistant container
12. High-grade steel is preferred. Depending on the infiltration
medium, it can be heated for lowering the viscosity of the
infiltrate 13. A seal 14 protects the vat from contamination and
from radiation ingress, which can lead to an undesired
polymerization. The cooling device 13, which provides for a
particularly high degree of conservation of the infiltration fluid,
represents an expansion.
[0090] A cage made of wire is preferred for the liquid-permeable
bracket 16. Retainer clips 17 or a weight 18 are located on said
cage for holding down the component. An axis for lowering 15
provides for an automatable and even dipping of the components.
[0091] FIG. 6 shows the hardening of the outermost layer by means
of UV radiation 20. The selection of the process parameters thus
takes place in such a manner that only a very thin layer is
solidified in the edge region. A distortion caused by a high degree
of internal stresses is thus avoided. For this purpose, 0.5% by
weight of TPO is located in the monomer mixture. The exposure takes
place by means of UVA radiation tubes comprising an input power of
75 W in a distance of 10 cm.
[0092] To compensate for inhomogeneities of the UV radiation
source, the component is moved in the radiation field. The movement
provides for the access of UV radiation to otherwise shadowed
areas. The movement can take place by rotation about all of the
spatial dimensions. A rotation about only one axis is
preferred.
[0093] A rotary table 19 comprising one or a plurality of degrees
of freedom is preferred for moving the component. To ensure the
influx of the radiation, the component is held in a bracket made of
wires, which encompass the smallest possible cross section. A
grate, which is connected to an axis of rotation, represents a
simple embodiment.
[0094] To prevent an adhesion of the components to the wire rack,
provision can be made for a special device. The supporting points
of the component 10 are thereby changed in a chronological sequence
by means of movement. A simple embodiment illustrated in FIG. 7
illustrated two grates 22, 23, which are integrated into one
another. One grate is thereby displaced against the second grate in
its height. The component is thus taken over by the respective
higher grid and the supporting points change 24, 25.
* * * * *