METHOD OF BONDING

METHODE DE COMBINAISON DU CAOUTCHOUC A UNE MATIERE AROMATIQUE

English Abstract

A B S T R A C T
A method of bonding an aromatic polyamide filamentary
material to a rubber composition comprising applying an aqueous
solution or dispersion of an epoxy resin to the filamentary
material, drying the coated filamentary material and assembling
the coated filamentary material with a rubber composition con-
taining resin precursors and vulcanising said composition in
contact with the coated filamentary material.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A method of bonding an aromatic polyamide filament-
ary material to a rubber composition comprises applying an aqueous
solution or dispersion of an epoxy resin to the filamentary material,
drying the coated filamentary material and assembling the coated
filamentary material with a rubber composition containing aldehyde
resin precursors, that is at least two components which will re-
act to form a thermosetting aldehyde condensation resin, and sub-
jecting the assembly to conditions which will vulcanise the rubber
composition and cause that aldehyde resin precursors to react,
2. A method according to claim 1 wherein the aromatic
polyamide filamentary material comprises a polymer of the formula
<IMG> or <IMG>
where A1 and Ar2 are aromatic radicals and n is an integer.
3. A method according to claim 2 wherein the aromatic
polyamide filamentary material composes poly(1,4-benzamide).
4. A method according to claim 2 wherein the aromatic
polyamide filamentary material comprises poly(1,3-phenylene iso-
phthalamide).
5. A method according to claim 2 wherein the aromatic
polyamide filamentary material comprises poly(1,4-phenylene tere-
phthalamide).
6. A method according to claim 1, 2 or 3 wherein the
epoxy resin is based on the reaction product of 2,2-bis (p-hydroxy-

phenyl)- propane with epichlorohydrin.
7. A method according to claim 1, 2 or 3 wherein the
rubber composition comprises sulphur as the vulcanising agent.
8. A method according to claim 1, 2 or 3 wherein the
rubber employed in the composition comprises natural rubber, cis-
1, 4-polyisoprene rubber, styrene-butadiene rubber, polybutadiene
rubber and a mixture of two or more of these rubber.
9. A method according to claim 1, 2 or 5 wherein the
resin precursors comprise an aldehyde condensation resin and a com-
pound which on heating becomes a methylene donor.
10. A method according to claim 9 wherein the resin pre-
cursors comprise an aromatic hydroxy compound and a compound which
becomes a methylene donor on heating.
11. A method according to claim 10 wherein the methylene
donating compound comprises hexamethylenetetramine, hexamethoxyme-
thylmelamine, lauryloxymethyl pyridinium chloride, cetyloxymethyl
pyridinium chloride, formaldehyde, a formaldehyde polymer and a
formaldehyde polymer having stabilising groups or residues of sub-
stances such as pentaerthritol at the ends of the molecules.
12. A method according to claim 10 or 11 wherein the
methylene donating compound is used in an amount of 0.1 to 10
parts by weight per 100 parts by weight of rubber in the composition.
13. A method according to claim 10 wherein the aromatic
hydroxy compound has two hydroxy groups arranged meta to each other.
14. A method according to claim 13 wherein the aromatic
hydroxy compound comprises resorcinol or 1,3-dihydroxy naphthalene.
15. A method according to claim 10 or 11 wherein the
aromatic hydroxy compound is used in an amount of 0,1 to 10 parts

by weight per 100 parts by weight of rubber in the composition.
16. A method according to claim 1, 2 or 3 wherein
the rubber composition contains silica.
17. An aromatic polyamide filamentary material bonded
to a vulcanised rubber composition with an interlayer of an epoxy
resin, the rubber composition containing a condensed aldehyde
resin.

Description

~ his invention relates to a method of bonding an
aromatic polyamide filamentary material to a rubber composition
and is an improvemen~ in or modification of the method described
in U.K. Patent Specification No. 1 465 063. Silica may be
included in the rubber composition.
. .
: According to the presen~ invention a method of bonding
an aromatic polyamide filamentary material to a rubber composition
comprises applying an aqueous solution or disp~rsion of an epoxy
: resin to the filamentary material, drying the coated filamentary
, .,
material and assembling the coated filamentary material with a
` rubber composition containing aldehyde resin precursors, that is
.~ at leas~ two components which will react to form a thermosetting
aldehyde condensation resin and subjecting the assembly to conditions
which will vulcanise the rubber composition and cause the aldehyde
. resin precursors to react.
The aromatic polyamide filamentary material may be of
the formula
,, l - 11 '1l -
Arl-C-~N- n or . - N-C-Arl-L I A 2 ¦ n
. wherein Arl and Ar2 are aromatic radicals and n is an integer,
for example poly-lj 4-ben7amide
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and poly~l,4-phenylene terephthalamide) ~:
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.( WiliCh are available in fibre form from DuPon~: as Fibre B
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or Kevlar/ and poly(l,3-phenylene isophthalamide) J
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which is available in fibre form from DuPont as ~omex
tregistered Trade Mark~.
Epoxy resins that may be used are those resins that
may be formed into an aq~ous solution or dispersion.
. ............ .
Typical epoxy compounds include those based on the reaction
product of 2,2-bis(p-hydroxyphenyl)~propane (Bisphenol A)
with epichlorohydrin, the reaction product of an aliphatic
diol or triol with epichlorohydrin; epoxidised polybutadiene
and triglycidyl isocyanurate.
A typical example of a water soluble epoxy resin is
: /IJ~R olo
~ e~e~ which is commercially available from NOGASI and
is based on the diglycidyl ether of glycerol.
The aqueous solution or dispersion of an epoxy resin
may also contain swelling agents for the resin e.g.
2-pyrrolidone, wetting agents e.g. dioctyl sodium
sulpho~uccinate (e.g. the compound whlch i9 cammercially
Crrc,d~ ~rh)
available as "Aerosol OT"I~rom American Cynamid) or any other
compound that will assist in the ~ormation of the solution or
dispersion, or the coating o~ the ~ilamentary material with `
the solution or dispersion.
The rubber composition containing resin precursors
is pre~erably vulcanised using sulphur as the vulcanising
agent. The rubber employed in the composition may be
~ natural rubber~ styrene-butadiene rubber, cis-1,4-poly-
.
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isoprene rubber, polybutadiene rubber or a blend o~ any of these
rubbers.
Particularly suitable aldehyde resin precursors com-
pounds are an aromatic hydroxy compound and a compound which on
heating becomes a methylene donor. Alternatively, one of the
resin precursors may itself be a resin capable o further reaction
eg. ~ novolac phenol-formaldehyde resin deficient in methyle groups
in combination wi~h a compound which on heating becomes a methylene
donor. The compound which becomes a methylene donor is pre~erably
stable up to a temperature of at least 100C. These compounds in-
clude those which generate formaldehyde on heating or may be com-
`- pounds such as hexamethylenetetramine. Other suitable compounds
include hexamethoxymethyl melamine, lauryl-oxymethyl pyridinium
chloride, cetyloxy~ethyl pyridinium chloride, ethyloxymethyl pyridin- ;
ium chloride, formaldehyde, polymers of ~ormaldehyde and polymers
of formaldehyde having stabilising groups or residues of substances
such as pentaerythritol at the ends of the molecules.
The amou~t of compound employed which liberates methylene
groups may be from 0~1 to 10 parts by weight, preferably from 0.5
, 20 to 3 parts by weight, per 100 parts by weight of rubber in the com-
~, position.
The aromatic hydroxy compound which may be employed
may be a monohydroxy compound, but it is pre~erably one containing
two hydroxy groups and it is especially preferred that the hydroxy
groups be meta to each other. Examples of suitable aromatic hydroxy
compounds are resorcinol and
.r.
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lr3-dihydroxy naphthalene. If desired, melamine or urea
or a compound which generates either o theqe two compounds
on heating may be employed in place of the aromatic hydroxy
compound.
The amount of aromatic hydro~y compound or other
compound employed to react with the compound which liberateq
methylene groups may be from 0.1 to 10 parts by weight,
preferably from 1.0 to 4.0 parts by weight, per 100 parts
by weight of rubber in the composition.
The aqueous solution or dlspersion of an epoxy resin
may be applied to the filamentary material by passing the
., .
material into the aqueous solution or dispersion at room
temperature, but i~ desired higher temperatures may be used.
. . .
- After the application of the epoxy resin coating the
5 material is dried. The drying process may comprise drying
.~! at room temperature ollowed by drying at a higher
temperature. The rubber composltion containing resin
precursors is then applied to khe coated filamentary
~material and the assembly is then suitably subjected to
heat and~pressure to vulcanise the composition and form the
resin precursors into a resin, thereby producing a bond
. . ,
between the coated filamentary material and the rubber
composition.
; The method of the present invention may be used to
; ?5 bond aromatic polyamide filamentary materials in the orm
of reinforcing cords to rubber~ compositions, in the
manufacture o~ e.g. tyres, driving belts, conveyor belts
and hose.~
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The method accordin~ to the present inven~ion is
illu~trated by the followin~ Example in ~hich all parts
are by welght,:-
EXAMP~E
Reinforcing cords based on the fibre~ produced frompoly(l,4-phenylene terephthalamide) as Fibre B availa~le
from DuPont were coated on a labora~ory ~cale with an epoxy ~
resin solu~ion of the ~ormulation given below, and were , :
~' subsequently dried. ~:
Part~
' Water 84.0 `~:
;~.', Sodium hydroxide (10% solution) 1.0
Epoxy resinl 3.0
2-pyrrolidone 10.0
',, 15 Wetting agent~ 2.0
1 - Diglycidyl ether o~ gl~cerol (was commercially available
dc. /na~
,,.`. ~ as "Epon 812"/rom Shell)
~ 2 = Dioctyl sodium sulphosuccinate (commercially available
~,
',~ as l'Aerosol OT" from American Cynamide)
Untreated cords and cords treated with the epoxy
resin solution were embedded in rubber compositions A to C
(Table I). The composition~ were then vulcanised for 25
~ minute~ at 148C.
2 The adhesion between the reinforcing cords and the
rubber composition in each case was then meaaured using a
atandard 1 cm pull-through test,(similar ko J O Wood Trans
: I R I, Vol. 32, No. 1, February 1956). The avsrage adhesion ~ :
~,~,values determined over 10 measurements are recorded in Table II. : ',
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TABLE I ~ B C
~atural rubber 100.00 100.00 100.00
Stearic acid 2.75 1.90 1.05
Retarder.(50/0 active0.60 0.60 0.60
cyclohexylthiophthalimide)
Antioxidant ~diphenylamine/ l.oo l.oo l.oo
~: acetone reaction product)
Process oil (aromatic7.00 7.00 7.00
-~ process oil available as
Dutrex RT~from Shell)
( T~ac/c. rrlark~
'~J~ Zinc oxide 7.50 7.50 7.50
: Carbon black (A furnace 43.00 43.00 43.00
black available as
Regal 30~)~ r~ h~
Sulphur 2.60 2.60 2.60
.~ Accelerator (2,4 morph- 1.20 1.20 1.20
iolinyl mercapto-
: benzthiazole
.: ~e~amethylene tetramine - 0.80 1.60
Resorcinol/stear.ic acid - 2.10 4.20
(60/40 melt) - ~
165.65 167.70169.75
:. TABLE II
.
Adhesion (Mewtons/cm)
.
Rubber Composition Treated Cords U~treated Cords
A 50 34
B 140 65
;`: C 138 96
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