Note: Descriptions are shown in the official language in which they were submitted.
~3~7~';'
:MAINTENANCE ~FREE SLIDING BEARING
The subject ~f the present invention is a novel
multi-layer maintenance-free sliding bearing.
Main~enance-free sliding bearings, which consist
of a metal base o~ a layer of plastic, are known for
example from German Offanlegungsschrift 3,534,242
publi~hed March 26, 1987 and European Patent Application
0,217,462 published April 4, 1987. Such multi-layer
sliding bearings con ist of a combination of a metal base
of steel, bronze or a high-strength alumi~ium alloy,
provided with a rough primary layer, and of a sliding
layer O:e a matrix of polyte~rafluoroethylene. The rough
primary layer consists of a porously sintered-on bronze
layer, iron layer or layer of an aluminium alloy. This
layer then forms the anchorage material for the
polytetrafluoroethylene layer, or a layer which consists
of its copolymers, to be applied in the form o~ a paste.
The high-viscosity paste is rolled firm and sintered.
What is disadvantageolls about the said sliding
bearing is that the layer of plastic produced from paste
is too thin for many applications. There~ore, the
service life of the bearings produ~-ed from it is not
ad~quate. Furthermore, the une,vennesses oc~urring during
the forming of the multi-layer material cannot be finish-
turned.
Whene~er bronze particles are incorporated in the
pa~te in order to improve the thermal conductivity of the
plastic, important for the bearing, there is the risk
that the outer layer oxidises during production. Such a
bearing material is also not inert. In particular, there
is the risk of des$ruction by acids. Furthermore, a
segregation may occur during application o~ the paste.
A ~ilm coating by means o~ conventional
polytetrafluoroethylene i5 known rom Fertigungstechnik
und ~etrieb 23 (1973), issue 1, pages 48-49. Sin~e this
material is completely inert with respect to all
adhesives, the film is firstly made adhesive. That is to
~2~3~ `'i'
-- 2
say the polytetrafluoroethylene films cannot be applied
to a base in such a way that they are held there by
physical forces of adhesion alone. Rather, it is
necessary to fasten the films by means of an adhesive.
In this case, the temperature endurance consequently no
longer depends only on the type of film but also on the
adhesiva used.
German Offenlegungsschrift 2,401,804 published in
1975 relates to a composite bearing element, the running
layer of whîch consists substantially of an unfilled
plastic. Polyarylene-sulfides, epoxy resins, polyamide
resins, polyester resins, phenoxy resins, polyimide
resins, polyamida-imide resins, polypropylene resins and
polysulfone resins are used for this. These films of
plastic are also not fastened directly to the metal
surface but with the aid of suitable adhesives. In
addition, it is recommended to apply a thin film of
lubricating oil to the plastics.
A coating consistinq of tetra*luoroethylene
filled with molybdenum disulfide has also been proposed.
In Adhesives Age, February 1967, pages 30-34,
polytetrafluoroethylene-coated metals are likewise
mentioned. However, the polytetrafluoroethylene is
chemically treated, so that a bond with the metal base is
established by epoxy groups. A direct application is
only considered possible ~or FEP. It is expressly
~tressed that this metal is thermoplastic and, unlike
tetrafluoroethylen~, can be applied directly to metal
without additional bonding layer.
Finally, it is pointed out that granular, free-
~lowing powders consisting of modified tetrafluoro-
ethylene polymers are known from German
Offenlegung~schrift 3,021,369. These powders are used
for RAM extrusion, since they are particularly well
suited ~or automatic
~ ~ 2 2 7 ~ D
-- 3 --
metering on account of their apparent density and their
free flowin~ properties. Suitability of this material
for the coa~ing of metals or other materials is not
mentioned.
The object of th~ invention is to create a
maintenance-free sliding bearing which does not have the
disadvantages mentioned.
This is achieved by the sliding bearing consist-
ing of a me~al base and a layer, applied directly on it,
of a copol~mer of perfluoroalkyl vinyl ether of the
formula:
C~2 = CF - O - R~,
where R~ is a perfluoroethyl radical, perfluoro-n-propyl
radical or perfluoro-n-butyl radical, and tetrafluoro-
ethylene, which forms either the sliding layer or an
int~rmediate layer on which a sliding layer of plastic is
applied.
The layer of a copolymer of perfluoroalkyl vinyl
ether and tetrafluoroethylene has a thicknes~ which is
adequate for a reworking. This may be up to 1.5 mm. The
layer is applied directly to the smooth or roughened
surface o~ the metal base. The application is per~ormed
by the copolymer layer being pressed over its surface
area onto the metal ba~e, unti:L the forces of adhesion
are adequately strong to hold it fi~m on the metal base.
I~ is thus to be seen as a special feature of the in~en-
tion that a layer consi~ting of a copol~mer o perfluoro-
alkyl vinyl ether and tetrafluoroethylene can b~ applied
directly to a metal base, This layer may serve either
directly as sliding layer or be used as intermediate
layer, on which polytetr fluoroethylene, polyLmide or
polyether ether ketone (PEER) in particular adhere well.
Tha~ is to say~it is not necessary to make ~he copolymers
of perfluoroalkyl vinyl ether and tetrafluoroethylene
adhesive or to fasten them by means of an adhesive. In
particular, the thermal endurance is therefore no longer
dependent on the adhesive used.
SteQl preferably comes into consideration
as metal base. Plastics, in particular
13 ?, ?~
~ ~
polytetrafluoroethylene, polyLmide or polyether ether
ketone (PEER~ are suitable as material for the sliding
layer applied on th~ layer of a copolymer of
perfluoroalkyl vinyl ether and tetrafluoroethylene.
Qne or more fillers may be added to the layer of
a copolymer of perfluoroalXyl vinyl ether and te~ra
fluoroethyl~ne and/or the sliding layer Qf plastic
applied to it, to intensify and/or improve the thermal
conductivity and/or the wear propertie~. Depending on
the objective, carbon, aluminium oxide, ceramic
materials, glass, bronze, molybdenum disulfite or silicon
carhide (weave~, powders, beads, fibres) are incorporated
in particular.
Good thermal conductivity properties which do not
entail the xisk of oxida ion during production are
achieved by silicon caxbide particles. ~he silicon
carbide particles are also acid~resistant and cheap.
They are al~o lighter than metal particles, in particular
bronze, so that there is not l;he risk of sPgregation
during the preparation of the :Layer of a copolymer of
perfluoroalkyl vinyl ether and tetrafluoroethylene~ On
the bearing side, on the other hand, fillers which
impxove the wear properties of the bearing should be
incorporated. In ~he case of the invention, a filler
content of 1 to 40% by volume can be accompli~hed,
because the filler need not be xolled in a~ in the case
o~ the prior ~rt, but is alrea~y present in the layer o~
a copolymer of perfluoro lkyl vinyl ether and
tetra~luoroethyle~e. 5 to 30~ by volume are particularly
preferred. The thickness of the layer of a copolymer of
perfluoroalkyl vinyl ether and tetrafluoroethylene (up to
1.5 mm) can be set Yary precisely~ which is not possible
when rolling on a paste as in the prior art in
thicknesses exceeding 50 ~mO
In tests, the sliding bearing has withstood
temperatures up to 260DC in continuous operatio~, depend-
ing on material used, without a peeling-off o the layer
of a copolymex of perfluoroalkyl vinyl ether and tetra~
fluoroethylene occurring. The sliding bearing withstood
r~
-- 5 --
brief higher temperature load without damage.
The structure of the sliding bearing material
according to the invention is shown in the Fi~ure. Here,
the metal layer is deno~ed by 1, while 2 denotes ~he
layer of a copolymer of perfluoroalkyl vinyl ether and
tetrafluoroethylene and 3 denote~ ~he layer of plastic
applied on it.
The pre-~ent in~ention i5 explained in more detail
by the following tests~
Ex~mple 1
~ests with tetrafluoroethylene and etched metal base (V~-
Metallo~last~
A steel plate wa~ coated.
Origin of the sliding layero ~talloplast~ ~P3 (=
PTFE + weave of
stainle~ steel +
gla~s + graphite)
Thicknes~ o th~ sliding layer: 0.48 mm
Temperaturs of the heated plate: 375 ~ 385C
Pres~ure of the heated plat~ 6 - 10 har
Origin o the intermediate layers Ho~taflo~R TFM 4025
Thickne3s of the intermediate
layer before coating: 0.25 mm
Thickne~s of the inke~mediate
layer after coating: about 0.20 mm
Re~ult of the qhear force te~t 5
= 106 N/cmZ at room temperature
= 70 N/cm2 at 200C
Example 2
Thickna~s of tha specimen before
coating: 1.10 mm
Thickne~s of the specimen after
coating: 1.00 mm
35 Te~perature of the heated plateo 29DC
Pre~ur~ of the heated plate: 6 - 10 bar
7 ~
- 6
Intermediate layer used: Hoæta1On(~
ET 6235 (ETFE)
Sliding layer as in Example 1
Etched and non-etched VA~Metalloplast was tested with
rising temperatures.
Results of the shear force tests:
Temperature etched non-etched MP
Metalloplast
~N/cm2) ~N/cm2)c
Room temp. 133 91
100C 12S 77
150C 107 62
200C 58 26
Ex~m~le 3
Slidin~ layer: PTFE filled with 35%
carbon
Thickness: 0.5 mm
Intermediate layers TFM with 30~ SiC
Thickne~: 0.25 mm
20 Temperatura of the heated plate: 330C
Pressure of the heated plate 2 2 bar
Result of the shear force test:
No peeling-off of the film, film tears~
Exam~le 4 ~no intermedia~e layer)
Sliding layer: TFM + 25% ~ 5% graph-
ite ~unetched3 (pres-
sed directly cn~o
steel)
Thickness: 0.25 mm
30 Temperature of the heated plate~ 380C
Pressure of the hsat~d plate: 2 bar
Result o th~ ~hear force tes~:
~t room temperature~ = 1500 ~/cm2
At 100C: = 1080 ~/C~2
At 150Co = 22() N/cm2
~ 3 9 2 7 ~ ~
-- 7 --
Exampl0 5
Sliding layer: polyimide (Rapton ~ype
M (DuPont~)
Thicknf~ss: 0.125 mm
Adhesive film: TFM (as in Example 1)
Thicknesss 0.25 mm
Tempera~ure of the hea~ed plate: 395C
Pressure of th~ he~ted plate: 50 bar
Result of the shear force test:
No peeling-off, film tears.
Exam~les 6 - 8
Test conditions:
Sample size: 25 ~ 25 mm
Pulling-o:Ef force: 0.100 kg
Temperatu:re variation: Increasing 5C per
stage
3 min. rising tempera-
ture
3 min. ~tabletempera-
~ure
ExamPle 6
Slidins~ layer: Netalloplast MP2
(- plastic + bronze
weave)
Intermediate layer- ETFE
Preparation of ~he sample: Metallopla~t MP2 +
ETFE: f ilm were pressed
onto a sheet ~ O . 5 ~n
chromed )
310C mould tempera
~ure, 25 sec. holding
time and
3 t mouldingpres~ure.
7 ~ ~
-- 8 --
Re~ult of the shear test: 5 samples dropped off
at 300C
Example 7
Sliding layer: ~etalloplast NP2
Intermediate layer: PFA film
Preparation of the sample: MetalloplastMP2 + PFA
film were pressed onto
a sheet 10.5 mm
chromed)
385C mould tempera-
ture, 25 sec. holding
time
3 t mouldingpressureO
Result of the shear test: 5 samples dropped off
at 380, 385, 386,
387, 390C.
Exam~le_8
Sliding layer: Metalloplast MP2
Intermediate layer: TFM film
Prepaxation of the sample: Metalloplast NP2 ~ TFM
film were pressed onto
a sheet (0.5 mm
chromed)
at
2S 3 t mouldingpressure.
Result of the hear test: no sample~ dropped off
at 410C.
The following meanings are used in the ~xamples:
PTFE = Polytetrafluoroethylene0 TFM = modified polytetrafluoroethylene (= copolymer of
pe~fluoroal~yl vinyl ether and tetrafluoro-
ethylene ~ccording ~o the i~vantion,
~2~
g
ETFE = copolymer o ethylene and tetra$1uoroethylene.
Here it is a thermoplastic fluoropolymer
PFA = Copolymer of perfluorovinyl ether and ~etra-
fluoroethylene. Thi~ product is chemically
5similar to TFM. Howevsr, due to it~ higher
e~her content, it is thermopla tic.
