U.S. patent application number 10/553242 was filed with the patent office on 2006-11-23 for use of an object as shaping tool.
Invention is credited to Hartmut Sauer.
Application Number | 20060260780 10/553242 |
Document ID | / |
Family ID | 33300841 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060260780 |
Kind Code |
A1 |
Sauer; Hartmut |
November 23, 2006 |
Use of an object as shaping tool
Abstract
Use of an article as moulding tool whose surface exhibits a
composite material in full or in parts, the composite material
consisting of a non-metallic substrate containing at least one
polymer, and a metallic layer present thereon and deposited without
external current, having an adhesive strength of at least 4
N/mm.sup.2.
Inventors: |
Sauer; Hartmut; (Wilnsdorf,
DE) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
33300841 |
Appl. No.: |
10/553242 |
Filed: |
April 15, 2004 |
PCT Filed: |
April 15, 2004 |
PCT NO: |
PCT/IB04/50462 |
371 Date: |
October 14, 2005 |
Current U.S.
Class: |
164/312 ;
164/98 |
Current CPC
Class: |
C23C 18/2013 20130101;
C23C 18/1662 20130101; C23C 18/1653 20130101; C23C 18/30 20130101;
Y02T 50/60 20130101; C23C 18/22 20130101; C23C 18/285 20130101;
C25D 5/14 20130101 |
Class at
Publication: |
164/312 ;
164/098 |
International
Class: |
B22D 19/00 20060101
B22D019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2003 |
DE |
10317794.9 |
Jan 9, 2004 |
DE |
102004001613.5 |
Claims
1. Use of an article whose surface exhibits a composite material in
full or in parts, the composite material consisting of a
non-metallic substrate containing at least one polymer, and a
metallic layer present thereon and deposited without external
current, having an adhesive strength of at least 4 N/mm.sup.2, as
moulding tool.
2. Use according to claim 1 characterised in that the standard
deviation of the adhesive strength at six different measured value
points distributed over the surface of the composite material is
maximum 25% of the arithmetic mean.
3. Use according to claim 1 characterised in that a) the surface of
the article is not chemically pretreated before the application of
the metallic layer deposited without electric current; and b) the
metallic layer is not applied by thermal spraying, CVD, PVD or
laser treatment.
4. Use according to claim 1 characterised in that the non-metallic
substrate is the surface of the article.
5. Use according to claim 1 characterised in that the non-metallic
substrate is not the surface of the article.
6. Use according to claim 1 characterised in that the boundary
present between the non-metallic substrate and the metallic layer
exhibits a roughness with an R.sub.z value of maximum 35 .mu.m.
7. Use according to claim 1 characterised in that the boundary
present between the non-metallic substrate and the metallic layer
exhibits a roughness with an R.sub.a value of maximum 5 .mu.m.
8. Use according to claim 1 characterised in that the non-metallic
substrate contains at least one fibre-reinforced polymer, in
particular a polymer reinforced with carbon fibre and the diameter
of the fibre is less than 10 .mu.m.
9. Use according to claim 1 characterised in that the non-metallic
substrate contains at least one fibre-reinforced polymer, in
particular a polymer reinforced with glass fibre and the diameter
of the fibre is more than 10 .mu.m.
10. Use according to claim 9 characterised in that the boundary
present between the non-metallic substrate and the metallic layer
exhibits a roughness with an R.sub.a value of maximum 10 .mu.m.
11. Use according to claim 9 characterised in that the boundary
present between the non-metallic substrate and the metallic layer
exhibits a roughness with an R.sub.z value of maximum 100
.mu.m.
12. Use according to claim 1 characterised in that the polymer is
selected from the group of polyamide, polyvinyl chloride,
polystyrene, epoxy resin, polyether ether ketone, polyoxymethylene,
polyformaldehyde, polyacetal, polyurethane, polyether imide,
polyphenyl sulphone, polyphenylene sulphide, polyarylamide,
polycarbonate and polyimide.
13. Use according to claim 12 characterised in that the metallic
layer exhibits an adhesive strength of at least 12 N/mm.sup.2
14. Use according to claim 1 characterised in that the non-metallic
substrate is polypropylene or polytetrafluoroethylene,
15. Use according to claim 1 characterised in that the standard
deviation of the adhesive strength amounts to maximum 25%, in
particular maximum 15%, of the arithmetic mean.
16. Use according to claim 1 characterised in that the metal layer
deposited without electric current is a metal alloy or metal
dispersion layer.
17. Use according to claim 1 characterised in that the metal layer
deposited without external current is a copper, nickel or gold
layer.
18. Use according to claim 1 characterised in that the metal
dispersion layer deposited without external current is a copper,
nickel or gold layer with embedded non-metallic particles.
19. Use according to claim 18 characterised in that the
non-metallic particles exhibit a hardness of more than 1,500 HV and
are selected from the group of silicon carbide, corundum, diamond
and tetraboron carbide.
20. Use according to claim 18 characterised in that the
non-metallic particles exhibit friction-reducing properties and are
selected from the group of polytetrafluoroethylene, molybdenum
sulphide, cubic boron nitride and tin sulphide.
21. Use according to claim 1 characterised in that, onto the
metallic layer deposited without external current, a layer of
aluminium, titanium or their alloys is applied whose surface is
anodically oxidised or ceramics-treated.
22. Use according to claim 21 characterised in that one or several
metallic layers are also arranged between the metallic layer
deposited without external current and the layer of aluminium,
titanium or their alloys.
23. Use according to claim 21 characterised in that the surface of
the article is a ceramic oxide layer of aluminium, titanium or
their alloys, which layer is coloured black by foreign ion
embedments.
24. Use according to claim 1 as punching, casting or conversion
tool.
Description
[0001] The present invention relates to the use of an article whose
surface exhibits a composite material in full or in parts, the
composite material consisting of a polymer and a metallic layer
present thereon, as moulding tool.
[0002] The conventional way of manufacturing lost-wax casting
models, spray, conversion or punching tools consists of
manufacturing the tools and/or models according to drawings on
cutting machines. Consequently, these conventional tools consist
mainly of materials which can be worked yet exhibit the necessary
properties with respect to hardness, low deformability and
dimensional stability. Examples of such conventional materials are
tool steel, case-hardened steels etc. Due to the need for the
cutting manufacturing process, it is not possible to manufacture
tool or models with very fine surface contours or corresponding
moulded parts.
[0003] Tools consisting of a metal/plastic composite material, on
the other hand are little known. An example is a moulding tool
which exhibits a shell of tool steel which is back-filled with
polymeric materials such as fibre-reinforced epoxy resin or epoxy
resin reinforced with metal particles in order to guarantee the
rigidity of the mould.
[0004] Articles with a surface exhibiting a metal/plastic composite
consisting of a polymer and a metallic layer present thereon are
otherwise known from other fields of application.
[0005] In general, there are three different types of such
articles:
[0006] On the one hand, those in the case of which at least one
metal layer is deposited directly onto the plastic surface by an
electrodeposition process without electric current. The field of
application of such articles is highly restricted as a result of
the plastics used so far and the low adhesive strength of the metal
layer applied without electric current and is almost exclusively in
the decorative area such as e.g. chrome-plated articles of ABS
(acrylic/butadiene/styrene polymers) or polymer blends, in
particular decorative mouldings, showerheads, radiators grills of
motor vehicles and coffee pots.
[0007] On the other hand, the use of such composite materials is
known for electronic structural parts such as shields in the high
frequency sector, in the case of which the metal layer present on
the plastic surface is produced by the vapour deposition of metal
onto plastic in a vacuum (CVD/PVD process). In this way, closed
metallic coatings are applied onto non-metallic substrates such as
plastics. On account of the basic principle, however, not all
common articles can be produced in this way with a metal layer
present on a plastic surface: on the one hand, no articles of
fairly large dimensions can be produced in an economic way on an
industrial scale; on the other hand, the metal layers have a
thickness if maximum 3 .mu.m. Moreover, structural parts with
indentations or cavities are not completely metallised and the
metal layer has only a very low adhesive strength such that its use
for tools subject to strong mechanical stress is altogether
impossible.
[0008] A wide-spread field of application for this vapour
deposition technique is coating of plastic films, e.g. for food
packaging. Thus, DE 198 49 661 A1 discloses the vapour deposition
of aluminium onto a special polyester film in such a way that it
exhibits a strong oxygen barrier, a high gloss and a low
coefficient of friction. The adhesive strengths of up to 3 N/mm
indicated therein, however, are too low to withstand a functional
application, subject to mechanical stress, of the metallised
film.
[0009] In DE 43 12 926 A1, a process for the improvement of the
adhesive strength of dental metal-polymer composite layers is
described. For this purpose, a metallic substrate onto which a
polymer has already been applied is irradiated with a special
Te--CO.sub.2 laser. If necessary, an adhesive agent is additionally
used. A metallisation of plastic substrates is not described
here.
[0010] DE 42 11 712 A1 also describes the irradiation of the
surface of a substrate in order to improve the adhesive strengths
with an Eximer laser. A PET (polyethylene terephthalate) film is
irradiated with this special laser in order to subsequently apply a
ferromagnetic metal layer by vapour deposition within the framework
of a PVD process. Such films are used as audio or video recording
medium, among other things.
[0011] In addition, a process exists for special plastics, such as
PEES and PA, in the case of which the articles to be coated are
first caused to swell with suitable substances and subsequently
etched chemically. The adhesive strengths of the metal layer
applied onto the plastic, which are thus achieved, amount to
maximum 2 N/mm.sup.2.
[0012] A major disadvantage of this process is the considerable
environmental pollution by the two chemical treatment agents such
that this process cannot be used much longer for considerations of
environmental politics.
[0013] A process, which has been developed further, for metallising
polyamides which is based on the principle, described above, of
causing the surface of the plastic substrate to swell but does not
provide for pickling with chromium sulphuric acid is presented in
an article by G. D. Wolf and F. Funger "Metallisierte
Polyamid-Spritzgu.beta.teile" (metallised polyamide
injection-moulded parts), Kunststoffe, 1989, pages 442-447. The
surface of the amorphous polyamide is treated with an
organometallic activator solution. Subsequently, a conventional
plating process for depositing a chemical nickel layer is carried
out.
[0014] A disadvantage of this type of surface treatment which is
based on a chemical reaction of the treatment solution with the
substrate is that the swollen surfaces are highly sensitive to
environmental influences such as e.g. dust embedments. Moreover,
the polyamide to be treated must be amorphous since partially
crystalline or crystalline polyamides are not attacked by the
method presented. Consequently, this method is a time-consuming,
expensive process which has only limited use in order to achieve
adhesive composite layers between the polymer substrate and metal
layer.
[0015] In order to avoid the problem of the complex and
time-consuming manufacturing process in the case of PVD composite
materials, composite materials have been developed in which the
metal layer is produced by thermal spraying onto the plastic
surface. During thermal spraying, metallic particles are heated and
applied in an accelerated manner onto the substrate to be
coated.
[0016] From U.S. Pat. No. 6,305,459 it is known to coat mould cores
of plastics, whose interior is cooled, externally by thermal
spraying with a metallic layer. A disadvantage of this process is
that only simple rotation-symmetrical articles can be coated with a
corresponding layer. Flat structures not exhibiting a rotation axis
cannot be metallised by this process since, as a result of the
geometry, so-called hot spots, i.e. local superheated areas, are
formed and the plastic substrate melts as a result of the thermal
energy used. The further essential disadvantages of this process
consist of the fact that the layers exhibit a high porosity, a high
inherent stress, a high layer thickness and insufficient adhesion
for articles subject to high mechanical stresses.
[0017] The object of the present invention consists of the
provision of a moulding tool whose surface exhibits in full or in
parts a composite material of a plastic and a metal layer, which
tool overcomes the disadvantages of the state of the art described
above and can be manufactured on an industrial scale.
[0018] The object is achieved according to the invention by the use
of an article whose surface exhibits a composite material, in full
or in parts, the composite material consisting of a non-metallic
substrate containing at least one polymer, and a metallic layer
present thereon and deposited without external current, having an
adhesive strength of at least 4 N/mm.sup.2, as moulding tool.
[0019] In an embodiment of the present invention which is
particularly preferred, an object is used as electronic structural
part whose surface exhibits a composite material, in full or in
parts, the composite material exhibiting a first non-metallic layer
and a second metallic layer applied thereon and [0020] a) the
surface of the article not being chemically pretreated before the
application of the metallic layer; and [0021] b) the metallic layer
not being applied by thermal spraying, CVD, PVD or laser
treatment.
[0022] Chemical pretreatment should be understood here and
subsequently, as a delimitation to mechanical treatments, any
treatment of a substrate surface which is carried out by pickling,
etching, swelling, vapour deposition, plasma treatment or similar
methods and in the case of which a change to the surface is caused
by a chemical reaction.
[0023] In contrast to the articles of the state of the art
metallised after chemical pretreatment, the articles according to
the present invention used exhibit a rough, sharp-edged boundary
layer between the non-metallic layer and the metallic layer applied
without external current. These sharp edged indentations and
undercuts of the boundary layer are clearly recognisable as edged
surface contours, e.g. in a microtome section analysis whose
execution is described in the following. Thus, they can be
distinguished from the rather roundish, and in any case rounded-off
contours which are formed in an ABS plastic by a chemical
pretreatment, e.g. by etching or by removing a 2.sup.nd phase
embedded for this purpose (FIG. 2).
[0024] The adhesive strengths (indicated in N/mm.sup.2) of the
composite materials according to the invention are determined
exclusively by way of the frontal tensile test according to DIN
50160: The frontal tensile test (vertical tensile test) according
to DIN 50160 has been used for many years for testing
semiconductors, the determination of the adhesive tensile strength
of thermally sprayed layers and in various coating techniques.
[0025] For the determination of the adhesive strength by the
frontal tensile test, the layer/substrate composite to be tested is
bonded between two test dies and subjected to a load under a
single-axis force up to rupture (compare FIG. 1). If the adhesive
strength of the adhesive is greater than that of the coating and
the rupture occurs between the layer and the substrate, it is
possible to calculate the adhesive strength according to the
equation .sigma. H .times. .times. exp = F max A G ##EQU1## (with
.sigma..sub.H exp: experimentally determinable adhesive strength,
F.sub.max: maximum force on rupture of the composite and A.sub.G:
geometric surface of rupture).
[0026] In a preferred embodiment, the standard deviation of the
adhesive strength at six different measured value points
distributed over the surface of the composite material is maximum
25% of the arithmetic mean.
[0027] The indicated homogeneities of the adhesive strength allow
the use according to the invention of articles with a composite
material as moulding tools in a particular manner. Thus, it is
possible to manufacture tools which can be subjected to both high
mechanical and thermal stress in a wide variety of forms, e.g. with
complex surface contours.
[0028] According to a further preferred embodiment, an article is
used whose composite material exhibits a non-metallic substrate
which is simultaneously the surface of the article. Preferably,
these surfaces are based on a polymeric material. Fibre-reinforced
plastics, thermoplastics and other industrially used polymers are
to be mentioned as being particularly preferred.
[0029] Similarly, however, it is also possible to use articles
whose non-metallic substrate is not the surface of the article.
Thus, the article used can consist of a metallic or ceramic
material which is coated with a non-metallic substrate which
contains at least one polymer.
[0030] In a further embodiment of the present invention, an
articles with a composite material is used as moulding tool which
exhibits a boundary present between the non-metallic substrate and
the metallic layer with a roughness whose R.sub.z value does not
exceed 35 .mu.m.
[0031] The R.sub.z value is a measure of the average vertical
surface fragmentation.
[0032] According to an embodiment of the present invention which is
particularly preferred, articles with a composite material are used
as moulding tools, which exhibit a boundary present between the
non-metallic substrate and the metallic layer with a roughness
expressed by an R.sub.a value of maximum 5 .mu.m.
[0033] The R.sub.a value is a measure reproducible by measuring
techniques of the roughness of surfaces, profile runaways (i.e.
extreme troughs or elevations) being largely ignored in the surface
integration.
[0034] To determine the roughness values R.sub.a and R.sub.z, a
specimen is taken from an article according to the invention and a
microtome section is made according to the method detailed as
follows.
[0035] When making the microtome section, there is the particular
difficulty that the boundary surface between the substrate and the
surface can be very rapidly destroyed or detached by the treatment.
To avoid this, a new separation disc from Struer, type 33TRE DSA
No. 2493, is used for each microtome section. Moreover, care must
be taken to ensure that the application pressure which is
transferred from the separation disc onto the substrate coating is
directed such that the force flows from the coating in the
direction towards the substrate. During the separation, care must
be taken to ensure that the application pressure is kept as low as
possible.
[0036] The specimen to be examined is placed into a transparent
embedding mass (Epofix putty, obtainable from Struer). The embedded
specimen is ground in a table grinding machine from Struer, type
KNUTH-ROTOR-2. Different abrasive papers with silicon carbide and
different granulations are used for this purpose. The exact
sequence is as follows: TABLE-US-00001 Granulation Time First
grinding treatment P800 approximately 1 min Second grinding
treatment P1200 approximately 1 min Third grinding treatment P2400
approximately 30 sec Fourth grinding treatment P 4000 approximately
30 sec
[0037] During the grinding process, water is used in order to
remove the grinding particles. The tangential force which arises at
the cross-section and by friction is directed in such a way that
the metallic layer is pressed against the non-metallic substrate.
In this way, the metallic layer is effectively prevented from
detaching itself from the non-metallic substrate during the
grinding process.
[0038] Subsequently, the specimen thus treated is polished with a
motor-driven preparation device of the DAP-A type from Struer. For
this process, it is not the usual specimen mover which is used but
the specimen is instead polished exclusively by hand. Depending on
the substrate to be polished, a torque of between 40 to 60 rpm/min
and an application force between 5 and 10 N is used.
[0039] The microtome section is subsequently subjected to SEM
micrography. For the determination of the boundary line
enlargement, the boundary line of the layer between the
non-metallic substrate and the metallic surface is determined with
a 10,000 fold magnification. For the evaluation, the OPTIMAS
program from Wilhelm Mikroelektronik is used. The result is
determined in the form of the X-Y value pairs which describe the
boundary line between the substrate and the layer. To determine the
boundary layer magnification in the sense of the present invention,
a distance of at least 100 .mu.m is required. The course of the
boundary layer needs to be determined with at least 10 measuring
points per .mu.m in this case. The boundary layer magnification is
determined from the quotient of the true length by the geometric
length. The geometric length corresponds to the distance of the
measured distance, i.e. between the first and the last measuring
point. The true length is the length of the line which passes
through all the measuring points recorded.
[0040] The surface roughness value R.sub.a is determined according
to the standard DIN 4768/ISO 4287/1 again using the X-Y value pairs
recorded before.
[0041] According to a further embodiment of the present invention
which is also preferred, the non-metallic substrate contains at
least one fibre-reinforced polymer, in particular a polymer
reinforced with carbon fibres, and the diameter of the fibres is
less than 10 .mu.m.
[0042] Moreover, in a further form of the present invention, the
non-metallic substrate may contain at least one fibre-reinforced
polymer, in particular a polymer reinforced with glass fibre, the
diameter of the fibre amounting to more than 10 .mu.m.
[0043] Insofar as the composite materials are subject not only to
thermal stresses but also to mechanical stresses, reinforced
plastics, in particular plastics reinforced with carbon fibre
(CRP), plastics reinforced with glass fibre (GFP) and also plastics
reinforced with aramite fibres or plastics reinforced with mineral
fibres are used particularly preferably. By using these articles, a
high rigidity of the resulting structural parts is achieved with a
low weight which structural parts are of particular interest for
industrial application because of their low cost. In particular,
polymers reinforced with glass fibre used as a component of the
non-metallic substrate exhibiting fibres with a diameter of more
than 10 .mu.m are very cheap and easy to process. The fibre
diameter has a strong influence on the roughness values such that,
in the case of such materials according to the present invention, a
roughness value R.sub.a of maximum 10 .mu.m is achieved. At the
same time, it is possible according to the invention to achieve
excellent values for the adhesive strength. In addition, the
articles used according to the invention have a high homogeneity of
adhesion. This makes it possible for the first time to
substantially increase the service life of the moulding tool since
even a local delamination of the layer composite leads to failure
of the moulding tool as a whole. Of particular weight is the
advantage in the case of moulding tools with a surface covered by
the layer composite of more than 10 dm.sup.2, i.e. in the case of
large structural parts or moulding tools with a large surface
area.
[0044] In a further embodiment, the article described above
exhibits a boundary between the non-metallic substrate and the
metallic layer which exhibits a roughness with an R.sub.z value of
maximum 100 .mu.m.
[0045] For the use of fibre-reinforced polymers, in particular,
whose fibre thickness is more than 10 .mu.m, it is important to
achieve R.sub.z values which are as low as possible. In the case of
this combination, it is, surprisingly, possible to achieve high
adhesive strengths with--in comparison to the fibre diameters
used--low R.sub.z values.
[0046] In a preferred embodiment of the invention, the polymer of
the non-metallic substrate is selected from the group of polyamide,
polyvinyl chloride, polystyrene, epoxy resins, polyether ether
ketone, polyoxymethylene, polyformaldehyde, polyacetal,
polyurethane, polyether imide, polyphenyl sulphone, polyphenylene
sulphide, polyarylamide, polycarbonate and polyimide.
[0047] In the case of this embodiment, the metallic layer may
exhibit an adhesive strength of at least 12 N/mm.sup.2.
[0048] However, in another embodiment of the present invention, the
polymer of the non-metallic metallic substrate may similarly also
be selected from polypropylene or polytetrafluoroethylene.
[0049] In those cases in which the non-metallic layer contains
either polypropylene and/or polytetrafluoroethylene, adhesive
strengths of at least 4 N/mm.sup.2 are achieved. This represents an
excellent value, in particular in combination with the high
homogeneity of the adhesive strength which could not be achieved
previously.
[0050] Embodiments according to the invention are particularly
preferred which exhibit a standard deviation of the adhesive
strength of six different measured value points distributed over
the surface of the layer composite of maximum 25%, in particular
maximum 15%, of the arithmetic mean.
[0051] In this way, an even higher mechanical resistance to stress
of the resulting moulding tools is guaranteed.
[0052] According to a further embodiment of the present invention,
which is also preferred, the metal layer deposited without electric
current is a metal alloy or metal dispersion layer.
[0053] In this way, articles with a composite material can be used
as moulding tools for the first time which exhibit an excellent
adhesion of the metallic layer to the non-metallic substrate. The
homogeneity of the adhesion of the metallic layer also plays an
important part for the suitability of these articles as structural
parts subjected to high stress. A controlled selection of the
non-metallic substrate and the metallic layer present thereon
allows an accurate adjustment of the property profile to the
conditions of the field of use.
[0054] Particularly preferably, a copper, nickel or gold layer is
applied onto the non-metallic layer of the article used according
to the invention as a metal layer deposited without external
current.
[0055] However, a metal alloy or metal dispersion layer deposited
without external current can also be applied, preferably a copper,
nickel or gold layer with embedded non-metallic particles. In this
respect, the non-metallic particles may exhibit a hardness of more
than 1,500 HV and may be selected from the group of silicon
carbide, corundum, diamond and tetraboron carbide.
[0056] These dispersion layers consequently have other functions,
apart from the properties described above; for example, the
resistance to wear and tear or surface wetting of the articles used
can be improved.
[0057] Also preferably, the non-metallic particles may exhibit
friction-reducing properties and be selected from the group of
polytetrafluoroethylene, molybdenum sulphide, cubic boron nitride
and tin sulphide.
[0058] The articles of the present invention are obtained
particularly preferably by means of a special process which
comprises the following steps: [0059] i. the surface of the
non-metallic layer is not chemically pretreated before applying the
metallic layer; [0060] ii. the surface of the non-metallic layer is
microstructured in a first step by a blasting agent; [0061] iii.
the metallic layer is subsequently applied by metal deposition
without external current.
[0062] The articles according to the present invention to be used
as moulding tools exhibit, as composite material, first of all a
non-metallic substrate which contains at least one polymer. To
produce the composite material according to the invention, the
surface of the non-metallic substrate is microstructured in a first
step by means of a blasting treatment. The process used is
described in DE 197 29 891 A1, for example. Inorganic particles
resistant to wear and tear, in particular, are used as blasting
agent. Preferably, these consist of copper-aluminium oxide or
silicon carbide. It has proven advantageous in this respect that
the blasting agent has a particle size of between 30 and 300 .mu.m.
It is further described therein that a metal layer can be applied
by means of metal deposition without external current onto surfaces
roughened in this way.
[0063] As the designation of the process already indicates, no
electric energy is supplied from outside during the coating process
in the case of the metal deposition without electric current but
instead the metal layer is deposited exclusively by a chemical
reaction. The metallisation of non-conductive plastics in a metal
salt solution operating by chemical reduction requires a catalyst
at the surface in order to interfere with the metastable
equilibrium of the metal reduction bath there and to deposit metal
on the surface of the catalyst. This catalyst consists of noble
metal seeds such as palladium, silver, gold and occasionally copper
which are added onto the plastic surface from an activator bath.
However, an activation with palladium seeds is preferred for
process technology reasons.
[0064] Essentially, the activation of the substrate surface takes
place in two steps. In a first step, the structural part is
immersed into a colloidal solution (activator bath). In this
respect, the palladium seeds necessary for the metallisation and
already present in the activator solution are adsorbed to the
plastic surface. After seeding, the tin(II) and/or tin(IV) oxide
hydrate which is additionally formed on immersion into the
colloidal solution is dissolved by rinsing in an alkaline aqueous
solution (conditioning) and the palladium seed is exposed as a
result. After rinsing, nickel coating or copper coating can take
place using chemical reduction baths.
[0065] This is effected in a bath maintained in metastable
equilibrium by means of a stabiliser, which bath contains both the
metal salt and the reducing agent. The baths for the nickel and/or
copper deposition have the characteristic of reducing the metal
ions dissolved therein at the seeds and to deposit elementary
nickel or copper. In the coating bath, the two reactants must
approach the noble metal seeds on the plastic surface. As a result
of the redox reaction taking place in this way, the conductive
layer is formed, the noble metal seeds absorbing the electrons of
the reducing agents in this case and releasing them again when a
metal ion approaches. In this reaction, hydrogen is liberated.
After the palladium seeds have been coated with nickel and/or
copper, the layer applied takes on the catalytic effect. This means
that the layer grows together starting out from the palladium seeds
until it is completely closed.
[0066] As an example, the deposition of nickel will be discussed in
further detail here. During coating with nickel, the seeded and
conditioned plastic surface is immersed into a nickel metal salt
bath which permits a chemical reaction to take place within a
temperature range of between 82.degree. C. and 94.degree. C. In
general, the electrolyte is a weak acid with a pH of between 4.4
and 4.9.
[0067] The thin nickel coatings applied can be strengthened with an
electrolytically deposited metal layer. Coating of structural parts
with layer thicknesses of >25 .mu.m is not economical because of
the low rate of deposition of chemical deposition processes.
Moreover, only a few coating materials can be deposited using the
chemical deposition processes such that it is advantageous to make
use of electrolytic processes for further industrially important
layer materials. A further essential aspect consists of the
different properties of layers chemically and electrolytically
deposited with layer thicknesses of >25 .mu.m, e.g. levelling,
hardness and gloss. The bases of electrolytic metal deposition have
been described e.g. in B. Gaida, "Einfuhrung in die Galvanotechnik"
(Introduction into electroplating) "E. G. Leuze-Verlag, Saulgau,
1988 or in H. Simon, M. Thoma, "Angewandte Oberflachentechnik fur
metallische Werkstoffe" (Applied surface technology for metallic
materials) "C. Hanser-Verlag, Munich (1985).
[0068] Plastic parts which exhibit an electrically conductive layer
as a result of a coating processes applied without electric current
differ with respect to electrolytic metallisation only slightly
from those of the metals. Nevertheless, a few aspects should not be
disregarded in the case of the electrolytic metallisation of
metallised polymers. As a result of the usually low conductive
layer thickness, the current density must be reduced at the
beginning of electrolytic deposition. If this aspect is ignored, a
detachment and combustion of the conductive layer may occur.
Moreover, care should be taken to ensure that undesirable layers of
tarnish are removed by pickling baths particularly adapted for this
purpose. Moreover, inherent stresses may lead to the destruction of
the layer. In the case of deposits of nickel layers from an
ammonia-containing bath, tensile stresses of the order of 400 to
500 MPa, for example, may occur. By means of additives such as
saccharin and butine diols, a change to the structure of the nickel
coating in the form of a modified grain size and the formation of
microdeformations may promote the decrease in internal stresses
which may have a positive effect on a possible premature failure of
the coating.
[0069] Examples of metal layers applied without external current
are described in detail in the handbook of AHC Oberflachentechnik
("Die AHC-Oberflache" Handbuch fur Konstruktion und Fertigung,
("The AHC surface" Handbook for construction and manufacture")
4.sup.th edition 1999).
[0070] In addition, one or several further layers, in particular
metallic, ceramic and crosslinked or cured polymer layers can be
arranged on the metallic layer.
[0071] It is thus possible, for example to apply a further
electrolytically deposited nickel layer onto a nickel layer
deposited without electric current, as metallic layer of the
present invention, and to deposit a chromium layer thereon. The
electrolytic deposition of the second nickel layer is preferably
carried out in order to be able to produce greater layer
thicknesses cost effectively.
[0072] The articles used according to the present invention can
also exhibit a nickel layer as metallic layer onto which a further
nickel layer is applied. It is possible in this way to achieve a
high rigidity of the resulting plastic parts, thus guaranteeing an
application for components subject to high mechanical stress.
[0073] Moreover, metallic layers can be applied onto an article
with a metallic layer according to the invention not only
electrolytically but also by means of other processes such as
CVD/PVD.
[0074] In this way, it is possible to apply aluminium or stainless
steel onto an article which consists e.g. of plastic and has been
provided with a nickel layer according to the present
invention.
[0075] In a further particularly preferred embodiment of the
present invention, a layer of aluminium, titanium or their alloys
is applied onto the metallic layer, deposited without electric
current, of the article used according to the invention, the
surface of the layer being anodically oxidised or ceramic
coated.
[0076] Such layers of aluminium, titanium or their alloys oxidised
or ceramic-coated by the anodic route are known on metallic
articles and are marketed under the trade name Hart-Coat.RTM. or
Kepla-Coat.RTM., for example, by AHC Oberflachentechnik GmbH &
Co. OHG. These layers are characterised by a particularly high
hardness and a high operating resistance and resistance to
mechanical stresses.
[0077] Between the metallic layer of the article used according to
the invention and deposited without electric current and the layer
of aluminium, titanium or their alloys, one or several further
metallic layers can be arranged.
[0078] The further metallic layers ranged between the layer
deposited without electric current and the aluminium layer are
selected according to the purpose of use. The selection of such
intermediate layers is well known to the expert and described e.g.
in the book "Die AHC-Oberflache--Handbuch fur Konstruktion und
Fertigung (The AHC surface--Handbook for construction and
manufacture") 4.sup.th enlarged edition 1999.
[0079] It is also possible for the surface of such an article to be
a ceramic oxide layer of aluminium, titanium or their alloys which
is coloured black by foreign ion embedment.
[0080] The ceramic oxide layer of aluminium, titanium or their
alloys which is coloured black by foreign ions is of particular
interest for high value optical elements, in particular in the
aircraft and aerospace industry.
[0081] The manufacture of ceramic oxide layers coloured black by
foreign ion embedment has, for example, been described in U.S. Pat.
No. 5,035,781 or U.S. Pat. No. 5,075,178. The manufacture of oxide
ceramic layers on aluminium or titanium is described e.g. in EP 0
545 230 B1. The manufacture of anodically produced oxide layers on
aluminium is described e.g. in EP 0 112 439 B1.
[0082] Overall, the examples detailed above show that the articles
according to the invention can be used in a very large field of
technical applications.
[0083] For example, an article according to the present invention
can be used as punching, casting or conversion tool.
EXAMPLE (ACCORDING TO THE INVENTION)
[0084] A panel of polyamide-6 with the dimensions
200.times.100.times.12 mm with an initial roughness of R.sub.a=0.64
.mu.m and R.sub.z=7.5 .mu.m was surface treated:
[0085] The surface pretreatment is carried out with a modified
pressure blasting device from Straaltechnik International. The
blasting device is operated at a pressure of 4 bar. A boron carbide
nozzle with a diameter of 8 mm is used as jet nozzle. The blasting
period is 4.6 s. SiC with the granulation P80 with an average grain
diameter of 200 to 300 .mu.m is used as blasting agent.
[0086] To adjust the blasting system specifically to the
requirements of the plastic modification as regards reproducible
surface topographies, 2 pressure circuits were installed, one each
for transporting the blasting agent and the actual acceleration
process respectively. This modification gave a highly constant
volume stream and a large pressure range.
[0087] A stream of compressed air transports the blasting agent
with a pressure as low as possible to the nozzle. The flow
conditions guarantee a low wear and tear of the unit and the
blasting agent as a result of a high volume stream of the blasting
agent and a low proportion of compressed air. Only at the end of
the conveying hose in front of the mixing nozzle is the cross
section reduced in order to adjust the desired volume stream. In
the case of all polymer pretreatments, a constant volume flow of 1
l/min was set. In the second part of the system, compressed air
(volume stream 1) flows to the nozzle which can be adjusted
steplessly within a pressure range of 0.2-7 bar. The blasting agent
which is conveyed into the mixing nozzle at a very low flow rate is
then accelerated by the high flow rate of the compressed air
stream.
[0088] The panel roughened in this way is treated in an ultrasonic
bath with a mixture of deionised water and 3% by vol. of butyl
glycol for five minutes.
[0089] The series of baths used for the metal deposition of the
conductive layer are based on the known colloidal palladium
activation in association with a final catalysed metal reduction.
All bath sequences required for this purpose were purchased from
Max Schlotter. The immersion sequences, treatment times and
treatment temperatures indicated by the manufacturer were
maintained in all the process steps of nickel deposition:
(1) Preliminary Activator Immersion Solution:
[0090] This is used to avoid the entrainment of contaminants and to
completely wet the specimen before the actual activation of the
surface. [0091] Immersion time: 2 min, room temperature (2)
Activator GS 510: [0092] Activation of the surface with
tin/palladium colloid. [0093] Immersion time: 4 min, room
temperature (3) Rinsing Bath: Deionised Water [0094] To avoid the
entrainment of activator GS 510 components by rinsing in deionised
water.
[0095] Immersion time: 1 min, room temperature
(4) Conditioner 101:
[0096] Conditioning of the material surface by removing undesirable
tin compounds from the surface. [0097] Immersion time: 6 min, room
temperature (5) Rinsing Bath: Deionised Water. [0098] Immersion
time: 1 min, room temperature (6a) Chemical Nickel Bath SH 490 LS:
[0099] Metallising of the plastics with a light-coloured,
semi-bright amorphous layer at a separation temperature of
88-92.degree. C. [0100] Immersion time: 10 minutes
[0101] In the case of the selected immersion time in the nickel
bath, a layer thickness of 1.4 .mu.m was obtained. This thickness
of the nickel layer is sufficient for an electrolytic coating. All
process steps necessary for depositing the conductive layer took
place in plastic tubs holding 50 l, a bath temperature of
90.degree..+-.0.5.degree. C. being maintained throughout the entire
coating cycle during the nickel deposition by means of an
additional hot plate with temperature control. In order to obtain a
homogeneous and reproducible layer quality, the series of baths
were analysed and supplemented according to information provided by
Max Schlotter after putting through 20 specimens.
[0102] After chemically applying the conductive nickel layer, the
specimen was cooled in distilled water from approximately
90.degree. C. to approximately 60.degree. C. in order to be then
coated further electrolytically with nickel at 55.degree. C. This
intermediate step had the purpose of avoiding the formation of
reaction layers and excluding inherent stresses caused by rapid
cooling. The specimens which were coated exclusively with a
conductive nickel layer cooled slowly to 25.degree. C. in a
distilled water bath.
[0103] The microtome section investigations by SEM (1,500 fold and
3,000 fold) are represented in the following figures (FIG. 3).
[0104] The results of the adhesive strength investigations are show
in Table 1. TABLE-US-00002 TABLE 1 No. Adhesive Strength 1 20.5
N/mm.sup.2 2 19.5 N/mm.sup.2 3 13.4 N/mm.sup.2 4 16.4 N/mm.sup.2 5
22.3 N/mm.sup.2 6 20.3 N/mm.sup.2 7 16.8 N/mm.sup.2 8 14.5
N/mm.sup.2 9 13.2 N/mm.sup.2 10 12.9 N/mm.sup.2 11 16.7 N/mm.sup.2
12 24.5 N/mm.sup.2 13 18.4 N/mm.sup.2 14 19.2 N/mm.sup.2 15 15.4
N/mm.sup.2 16 22.9 N/mm.sup.2 17 16.7 N/mm.sup.2 18 17.3 N/mm.sup.2
19 12.8 N/mm.sup.2 20 14.5 N/mm.sup.2 21 18.2 N/mm.sup.2 22 19.7
N/mm.sup.2 23 23.4 N/mm.sup.2 24 18.9 N/mm.sup.2 25 20.1 N/mm.sup.2
26 21.4 N/mm.sup.2 Standard deviation 3.4 N/mm.sup.2 Mean 18.1
N/mm.sup.2 Coefficient of variation 19%
COMPARATIVE EXAMPLE (NOT ACCORDING TO THE INVENTION)
[0105] The example according to the invention is repeated; however,
after the blasting treatment, the panel is treated in an ultrasonic
bath, in a suspension of 5% by weight of CaCO.sub.3 in 96% ethanol
for 5 minutes.
[0106] Subsequently, the panel is treated in a further ultrasonic
bath with pure 96% ethanol for a further five minutes.
[0107] The micro section investigations by SEM (1,500 fold and
3,000 fold) are shown in the following figures (FIG. 4).
[0108] The evaluation of EDX analysis gave a residual quantity of
calcium of 0.91% by weight which originates from the treatment of
the CaCO.sub.3/ethanol suspension.
[0109] The results of the adhesive strength investigations are
shown in Table 2. TABLE-US-00003 TABLE 2 No. Adhesive Strength 1
9.9 N/mm.sup.2 2 19.1 N/mm.sup.2 3 10.1 N/mm.sup.2 4 13.1
N/mm.sup.2 5 16.6 N/mm.sup.2 6 10.3 N/mm.sup.2 7 19.8 N/mm.sup.2 8
13.3 N/mm.sup.2 9 21.4 N/mm.sup.2 10 10.9 N/mm.sup.2 11 20.0
N/mm.sup.2 12 10.9 N/mm.sup.2 13 11.7 N/mm.sup.2 14 13.0 N/mm.sup.2
15 16.4 N/mm.sup.2 16 14.1 N/mm.sup.2 17 15.4 N/mm.sup.2 18 10.5
N/mm.sup.2 19 15.8 N/mm.sup.2 20 16.7 N/mm.sup.2 21 8.5 N/mm.sup.2
22 17.2 N/mm.sup.2 23 7.0 N/mm.sup.2 24 18.2 N/mm.sup.2 25 7.2
N/mm.sup.2 26 19.4 N/mm.sup.2 Standard deviation 4.2 N/mm.sup.2
Mean 14.1 N/mm.sup.2 Coefficient of variation 29.8%
[0110] The resutls clearly show a signficant difference between the
standard deviation of the adhesive strength of the different
measured valued points distributed over the surface of the
composite material.
[0111] During the using of moulding tools, this difference leads to
a substantially longer service life since no locally occurring
delamination is observed.
LIST OF REFERENCE SYMBOLS OF FIG. 1
[0112] (1) Tensile die [0113] (2) Adhesive [0114] (3) Metal layer
[0115] (4) Substrate
* * * * *