Note: Descriptions are shown in the official language in which they were submitted.
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Ht~LS AKTIENGESELLSC}IAET 0. Z . 4428
- - PATENTABq'E ILUNG
Composite article~ of mQtals and vulcanized rsbb~L-A~
process for their preparation
The invention relates to composite articles which are
composed of at least one metal component and at lea~t one
vulcanized rubber component and which contain an
adhesion-promoting polyamide layer and to a process for
the preparation of articles of this type.
~t is well known that a s$ngle material cannot always
provide all the properties which are regu$red of an
ob~ect. For in~tance, high strength, rigidity or hard-
ness on the one hand are irreconcilable with qood vlbra-
tion damping, flexibility or non-skid properties on the
other hand. If an article is to combine these proper-
ties~ then composites of a plurality of materials are
used.
One possibility in this case is to use metal and
vulcanized rubber. According to the state of the art,
the following procedure i8 used to prepare elements whose
components, metal and vulcanized rubber, are firmly
bonded togethers
1. The metallic component is shaped, for example by
casting, pressing, machining or drawing.
2. The surface of the metallic component $8 treated, for
example by degreaslng, sandblasting, brassing or
phosphatizing.
3. A primer is applied from a solution, for example in
aroma~ics or chlorinated hydrocarbons.
4. The solvent iB removed by evaporation.
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5. An adhe~ion promoter i8 applied from a solution, for
- example in aromatics or chlorinated hydrocarbon~.
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6. The ~olvent i3 removed by evaporation.
7. The unvulcanized rubber i8 applied to the metal
surface which has been pre-treated in this manner and
is vulcanized.
The substancQs which promote adhesion between metal and
unvulcanized or vulcanized rubber are descrlbed, for
example, in W. Rleemann, Mii8chungen f~r die Elastverar-
beitung, Leipzig 1982 and ln the Bayer-Taschenbuch fUr
die Gumml-Industrie, 1963, and also in particular in data
sheet~ from ~enkel RGaA under the trade name "Chemosil~.
,
; The known processes are in need of improvement for a
; variety of reasonss
1. They ar- oompllcated, as can be seen from the list
of the~m~ny process steps.
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2. They are not ~afe with regard to environmental
pollution and occupational health hazardss the
801vent8 are not harmle~s and must be dispQsed of.
2D ~ 3. Th tr at-d e-l co~ponents have a limlted shelf
4. The procedure cannot be automated. -~
It~ ha~ i;now~been found that the conventional adheslon
promoter-~;and~primers can advantageously be dispensed
~ with if~the~metal 8urface is coated in a manner known per
se~with polyamide~ before thi8 surface is brought into
oontact wlth certa~in unvulcanized rubber composition~.
The~polyam$de is applied either by electrostatic powder
coating or by fluidlzed bed coatlng. It is al80 pos~ible
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to apply the polyamide in the manner of a paint or by
extrusion coating, but these processes are less advantag-
eous. The suitable powder coating processe~ are des-
cribed, for example, by R. Feldmann in data ~heet no.
5215 from HUls AG, D-4370 Marl, dated November 1987.
Coating processes have hitherto been used to protect the
metal surface from corrosion; the use of the said powder
coatlngs as adhesion promoters for unvulcanized rubbers,
as de~crlbed here, i8 novel.
The use of polyamides as adhesion promoter between
metals and unvulcanized or vulcanized rubber has a number
of advantages in comparison with conventional processes~
,
1. Problems to do with ecology and hygiene are elimina-
ted, since no solvents are used.
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2. The metal components which have been treated with the
adhesion-promoting polyamide have a virtually unlimi-
ted shelf llfe.
3. The procedure can be automated.
The unvulcanized rubbers listed below can be used for the
~ 20 process according to the invention. These unvulcanized
'~ rubbers must be crosslinked using peroxide or other free
;;I- radical-forming additives. Crosslinking agents based on
,~ ~ sulphur or ~ulphur donors alone are unsuitsble for the
process.
The metallic components used are preferably workpieces
made from steel, but it 18 also possible to use iron or
non-ferrous metals such as alumlnium or brass. The
surf~ces can be pre-treated, for example by degreasing,
sandblasting or phosphatizlng. A primer, such as is
often consldered necessary with polyamide powder coat-
~` - ings, is superfluous in this case.
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-~ The polyamide tPA) used is preferably PA 1012, PA 11,
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PA 12*or PA 1212* Paxticular preference 18 given to PA
1~ having a relative vi~c08ity in m-cresol (determined in
accordance with the condition~ described in DIN 53 727)
of 1.4 to 2.0, preferably 1.5 to 1.7. The polyamide i~
used in pulverulent for~. The particle diameter can b~
up to 200 ~m. The polyamide may optionally contain
additive~ such as, for example, catalyets, ~tabilizer~ or
pigment~. Proce~es for the preparation of suitable
polyamides are known (R. Vieweg/A. MUller, Xun~tstoff-
handbuch, Vol. 6 - Polyamide, C. Hanser Verlag, Munich
1966, p. 187; D. E. Floyd, Polyamide Resins, 2nd Editlon,
Chapman Hall New York/London 1966, p.S5).
The preparation of polyamide powders for coatings is des-
cribed, for example, in German Published Patent Applications
No. 3,510,687, 3,510,688, 3,510,689, 3,510,690 and -
3,510,691 (corresponding to European Published Patent
Applications No. 0,202,393, 0,199,000, Q,200,853,
0,200,852 and 0,202,389).
; The unvulcanized rubber compositlons used contain~
- - 100 parts by weight of a carboxyl- or -
anhydride-containing rubber
- 10 to 300 parts by weight of additives
; - 1 to 10 parts by weight of peroxide vulcaniz-
ing agents
- O.S to 4 parts by weight of vulcanization -~
activators and
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~ ~ - 0 to 150 parts by weight of plasticizer
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~ The unvulcanized rubber u~ed may also be a mixture of
I Pi! various~uitabl6 types. Preference i~ given to iEP(D)M
and NBR rubber~.
~he EPM rubber i~ prepared in a known manner by polymeri-
zing a mixture of 25 to 75% of ethylene and 75 to 25% of
~ propylene ~n the pre~ence of a Ziegler-Natta catalyst.
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The EPDM rubber 18 prepared in similar manner by polymer-
izing a mixture of
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more than 25~ of ethylene,
more than 25% of propylene and
1 to 10%, in particular 1 to 3%, of a diene.
~ This diene must not be con~ugated. PreferenCe i~ given
to bicyclo(2.2.1)h~ptadiene, 1,4-hexadiene, dicyclopenta-
diene and in particular 5-ethylidenenorbornene.
The carboxylation of the EP(D)M rubber~ is carried out,
for example, in a known manner by compounding with
unsaturated acid~ or acid derivatives such a maleic acid
or maleic anhydride (MAA), optionally in the presence of
a free radical initiator. Suitable preparative methods
are given, for example, in US-A-4,010,223.
Carboxylated EPM rubbers of thi~ type are produced, for
example, by EXXON under the trade name EXXELORR VA 1803.
An example of an EPD~ rubber which has proven suitable is
maleic anhydride-modified BUNAR AP (trade name: ~V~STAMID
X 4496~) from Bunawerke H~ls GmbH, D-4370 Marl.
The nitrile rubbers ~NBR) are prepared in a known manner
by copolymerization of 50 to 80 % by weight of butadiene
and correspondingly 50 to 20 % by weight of acrylo-
nitrile. The carboxyl-containing nitrile rubbers are a
particular modificatio~. These are copolymers of
butadiene, acrylonitrile and acrylic acid, methacrylic
acid or sorbic acid.
The vulcanizates of mixtures of this type have a high
tensile strength, good elasticity and very good abrasion
resistance. The oil and solvent resistance typical of
nitrile rubber remains unaltered.
.
Suitable carboxylated NBR rubbers are produced, for
example, by GOODYEAR TIR~ & RUBBER Company, Akron, Ohio,
~ USA, under the trade nam~ CHEMIGUN~ NX 775 or by BF
-~` GOODRICH, NV, Arnhem, Netherlands, under the trade name
~ HYCAR~ 1472.
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Suitable additives are all conventional fillers for
EP(D)M and NBR rubbers such as, for example, carbon
black, silica, ~ilicates and calcium carbonates, and also
zinc oxide and stearic acid.
Suitable plasticizers are, in particular, mineral oils or
synthetic plasticizers such as esters and ethers. In
this context, in the case of EP(D)M rubber, preference is
given to the use of mineral oils, in particular naph-
thenic oils. The amount of plasticizer can be up to 150
part~ by weight, relative to 100 parts by weight of
rubber; preferably up to 50 parts by weight.
Suitable peroxide vulcanizing agents are the peroxides
known to a person skilled in the art such as, for
example, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane,
dicumyl peroxide, 4,4-di-tert-butylperoxy-n-butyl
valerate, l,l-di-tert-butylperoxy-3,3,5-trimethyl-cyclo-
hexane and bis(tert-butylperoxyisopropyl)benzene.
Details regarding the use of peroxide vulcanizing agent~
are to be found in the company brochure ~Rubbery
Chemical-Crosslinking-Peroxides" from Akzo-Chemie (publi-
cation date: April 1985).
Examples of suitable vulcanization activators ars
triallyl cyanurate (TAC) and acrylates such as ethylene
glycol dimethacrylate (EDNA) and trimethylolpropane
--~ 25 trimethacrylate (TRIM). Preference is given to the use
;~ of TAC and/or EDMA.
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The composite articles are prepared by vulcanizing the
abovementioned rubbers ln intimate contact, preferably
under pressure, with the polyamide-coated metals. The
vulcanizing conditions are identical per se with the
conditions which are used when employing conventional
adhesion promoters. The vulcanization is preferably
carried out at temperatures of between 140 and 200-C in
2 to 30 minutes, in particular at temperatures of between
150 and 180-C in 5 to 10 minutes.
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Ex~mple~ o typ~cal compo~lte artlcle~ m~de fro~ met~l~
and ~ulc~nlzed rubber ~re rubber-co~ted roller~, se~
flangeA, buffer~, ~prlng element~, Ylbratlon damper~,
met~l-relnforced rubber proflle~, and clutch and brake
disc~. A partlcular advantage of elements of thl~ type
1~ their resi~tance to corrosive media, in partlcular to
corrosive ~alt~
The ex~mple~ whlch follow ser~e to illu~tr~te the
lnvention. In these example~, the following 8ub~tance~
are used
E~X2LORa VA 1803 i~ a malelc ~nhydride-modifled ~P~ rubber
from Exxon Chemical~, Wilmlngton, ~elaware, USA. $he
propertle~ of thi~ product are given ln the technical
data sheet ~EXXELOR VA~, dated 01.03.1988.
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ZnO c~n be obt~ined under the trade na~e Zinkwei~ ~
Rot~iegel from Grillo-Werke AG, D-3380 Goslar. : -
VULXASII~ C i~ a highly reactive ~ilica, obtainable fro~
Bayer AG, D-5090 Leverku~en.
CIRCOSOL~ 4240 ~ a predomlnantly naphthenic mineral oil
fro~ Sun Oll, Antwerp (Belglu~
VULXANOS~ HS 1~ an antioxidant fro~ 8ayer AG, D-5090
~everku~en. It i~ 2,2,4-trimethyl-1,2-dlhydroqu~noline.
PERXADO~a 14/~0 and PERKADO~ BC ~0 are peroxide~ ~ro~
, I 25 ~ Akzo-Chemie, 3800 AZ Amer~foort, NetherlandJ.
~AC (triallyl cyanurate) and eDMA (ethylene qlycol
dimethacrylate) are product~ of Degu~a, D-6450 Hanau.
;~ CHEMIGUn~ N~ 7~5 18 a carboxyl-containing NBR rubber from
Goodyear $1re and Rubber, Akron, Ohio, USA. The proper-
tle~ of thl~ product are given in the data sheet
s ~
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"CHEMIGUMR NX 775", November 1987.
Example 1 (using a carboxylated EPM rubber)
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A 1 mm thick steel panel is heated to 400C in a heating
furnace in the course of 10 minutes and then dipped for
10 seconds into a fluidized bed which is filled with the
commercially available coating powder of the trademark
VESTOSINTR 1101 white. The coated steel panel i8 allowed
to cool. The poly~mide-coated ~teel panel i~ mounted in
a 4 mm thick spacer frame and one third of the panel i~
coated with a Teflon film to prevent adhesion in this
area, and then the panel and release film are coated with
a milled sheet composed of
EXX~LORR VA 1803100 parts
ZnO 5 parts
VULRASILR C 60 parts
CIRCOSOL8 4240 40 parts
VULRANOXR HS 2 parts
PERRADOXX 14/407.5 parta
~ TAC 3 parts
- 20 and the composition is pressed for 20 minutes at 170-C
and 200 bar. After this treatment, the metal and the
vulcanized rubber can only be separated from one another
by a cohesive fracture within the rubber.
Example 2 (using a carboxylated N~R rubber)
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The procedure of Example 1 i8 followed, but a different
I l unvulcanized rubber mixture is used~ ` -
CHEMIGUMR NX 775100 parts
Stearic acid 1 parts
VULRASILR C 40 parts ~-
PERRADOX~ BC 40 3 parts
~¦ ~ Actlvator EDMA 0.5 parts
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In this composite article al80, the vulcanized rubber and
metal can only be separated from one another by a cohe-
sive fracture within the rubber.
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