Note: Descriptions are shown in the official language in which they were submitted.
lU37~
This invention relates to composite structures and in
particular to composite structures of unsaturated rubbers and
polyesters and to a method of making such structures.
It has been proposed to bond an epichlorhydrin rubber
to a polyester by melting at least the surface of the polyester
to be bonded to the rubber and solidifying the polyester in
contact with the rubber (British Patent Serial No. 1387583).
We have now found that it is possible to bond certain polyesters
to certain non-polar unsaturated rubbers by this method pro-
vided that the rubber surface is subjected to a certain pre-
treatment.
According to the present invention there is provided
a composite structure of an unsaturated rubber selected from
. polychloroprene and copolymers of chloroprene with at least
one copolymerisable hydrocarbon and a polyester which is a
reaction product of at least one aliphatic dihydric alcohol
and at least one aromatic compound having two acidic groups
attached to the aromatic nucleus one being a carbonyl-contain-
ing acidic group and the other being a carbonyl-containing :
acidic group or an acidic hydroxyl group, the rubber being
bonded directly to the polyester without ah adhesive inter-
.~ layer.
According to the present invention also, a method
: of making a composite structure of an unsaturated rubber
selected from unsaturated hydrocarbon polymer rubbers,
polychloroprene and copolymers of chloroprene with at least
one copolymerizable hydrocarbon, and a polyester selected
from reaction products of at least one aliphatic dihydric
alcohol and at least one aromatic ompound having two acidic -.
, 30 groups attached to the aromatic nucleus, one being a carbonyl~
` containing acidic group and the other being a carbonyl-con-
- taining acidic group or an acidic hydrozyl group and : .
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~0371~8
elastoplastic linear block copolymers having at least one
block of a reaction product defined in the rubber being bonded
directly to the polyester without an adhesive interlayer,
which comprises treating the surface of the rubber to be
bonded to the polyester with a treatment agent selected from
concentrated nitric acid, hypochlorous acid and hypochlorous
acid generators, heating the polyester to melt at least the
surface to be bonded to the rubber, and solidifying the molten
polyester in contact with the treated rubber. -~ -
10The treatment time should be sufficient to modify - -
the rubber surface without undesirably degrading the bulk
of the rubber, and any residual treatment agent reamining
at the end of the treatment should be removed if its presence
would undesirably affect the rubber or the polyester. The
treatment agent is a modifying agent for the rubber surface
and does not take the form of an adhesive composition or ;
cement between the rubber and the polester.
- The treatment agent may be applied by any convenient
; means, for example by dipping, spraying or brushing, and
,.
the treatment is suitably performed at room temperature
(about 15-20 C). When the treatment agent is concentrated
nitric acid this may be applied as a liquid or as a gel or
paste with fine silica powder. Examples of treatment agents
in the form of hypochlorous acid generators are acidified
solutions of alkali metal hypochlorites, trichloroisocyanuric
.l acid and alkali metal salts of mono- and di-chloroisocyanuric
acid. The alkali metal is suitably sodium. The trichloro-
isocyanuric acid may be employed as a solution in ethyl
acetate and the alkali metal chloroisocyanurates may be
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employed as aqueous solutions.
The rubber is usually in the vulcanized state in
the composite structure. The rubber may be vulcanized in
contact with the polyester, in which case the conditions
of vulcanization may be sufficient to melt the polyester,
or the rubber may be in the vulcanized state prior to contact
with the polyester. The rubber may be peroxide-vulcanized
but preferably it is vulcanized by a sulphur-based vulcanization
system.
Although the treatment employed in this invention
should improve the bond between the polyester and a rubber
having any amount of unsaturation, it is preferred, in
order to obtain a significant improvement for most
practical purposes, that the rubber which is treated
should have more than five carbon-carbon double bonds
for every one hundred main-chain carbon atoms and more
preferably in excess of fifteen carbon-carbon double
bonds for every one hundred main-chain carbon atoms.
When the rubber is a hydrocarbon rubber it may suitably
be a linear polymer of a cyclic hydrocarbon monoene,
for example cyclopentene which polymerises to poly-1,5-
- pentenamer, or a polymer of an aliphatic hydrocarbon
diene. When the rubber is a copolymer of an aliphatic
hydrocarbon diene, the comonomer(s) may be aliphatic
and/or alkenyl-aromatic hydrocarbons. Examples of
suitable aliphatic hlydrocarbon diene rubbers are
-' natural rubber,i synthetic cis-polyisoprene, polybutadiene
rubber, butadiene/styrene rubber and butadiene/alpha-
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1~37~48
methylstyrene rubber. The rubbers referred to herein may
be blended with each other and/or with one or more other
rubbers, and are usually in compositions containing ingre- ;
dients normally used in rubber compositions, for instance
fillers, processing aids, anti-ageing agents and vulcanizing
- agents.
The polyester is normally thermoplastic before and -
after being bonded to the rubber by the method of this
invention. It is desirable that the polymer should not be
heated too far above its softening point (i.e. the temperature ^
at which it become thermoplastically processible) which for
elastoplastic linear block copolymers is in the region of
200 C because this may lead to loss of quality from thermal
instability by, for example, pyrolysis or oxidative degrada-
tion.
The polyester may be the reaction product of at
least one aliphatic dihydric alcohol and at least one aroma-
tic compound having two acidic groups attached to the aroma-
tic nucleus, one being a carbonyl-containing acid group e.g.
' 20 a carboxylic acid group (COOH), a carboxylic ester group .;
(COOalkyl) or a carbonyl chloride group (COCl), the other
being a carbonyl-containing acid group or an acidic hydro- ~
xyl group (OH). These reaction products are generally long ;
chain ester condensation polymers in which the carbonyl carbon
atom of each ester group is in the polymer main chain and
; is attached directly to ah aromatic nucleus. The reaction
'r, product is preferably a poly(alkylene terephthalate), a ~-
. . .
poly(alkylene isophthalate), and alkylene terephthalate/
isophthalate copolymer or a reaction product of an aliphatic
diol and p-hydroxybenzoic acid. The alkylene groups, which are
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1037~48
derived from the one or more dihydric alcohols, may have for
instance from two to eight carbon atoms. Specific examples
of suitable reaction products are poly(ethylene terephthalate),
poly(butylene terephthalate), poly(1,4-dimethylenecyclohexane
terephthalate) and 1,4-dimethylenecyclohexane terephthalate/
isophthalate copolymers. Poly(tetramethylene terephthalate)
results in a particularly strong bond when employed in the
present invention.
Alternatively, the polyester may be an elastoplastic
linear block copolymer having at least one block of a reaction
product defined in the immediately preceding paragraph. A
preferred block copolymer is one having (a) n (where n is a
positive integer) substantially amorphous (in the unstretched
state) blocks of a polyether e.g. polytetrahydrofuran or poly-
~rimethylene glycol), an aliphatic acid polyester e.g. poly-
(propylene adip~te ) or polycaprolactone, an olefin polymer
e.g. ethylene/propylene copolymer, or two or more sub-blocks of
- one or more of these species interlinked by means of, for
example, a diisocyanate in the case of hydroxyl-terminated
species, and (b) n + 1 blocks of the aforementioned reaction
product which will generally be crystalline. The molecular
weight of each of these blocks may suitably be in the range
1,000 to 10,000.
A particularly preferred block copolymer is one having
n blocks of a polyether and n + 1 blocks of the aforementioned
reaction product. The ratio of the number of carbon atoms ~
to the number of oxygen atoms in the repeating unit of ;
the polyether block should preferably be greater than
2.5:1 and the melting point of the polyether should
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preferably be less than 55C. Preferably the average
molecular weight of the polyether should lie wlthin the
range 600 to 6,000. Preferred blocks of the aforementioned
polyeeter reaotion product are crystalline block~ having a
melting point greater than 170C and preferably from 30 to
60 per cent of the block copolymer is comprised of the
polgesterreaction product. Other preferred feature~ of
the polyester reaction product blocks are (i) from 50 to 90
per cent, especially from 65 to 85 per cent, of the ester
units in each block are identical, (ii) a separate polymer
; of these identical units having a molecular weight of about
5,000 would have a melting point of about 174C, and (iii) a
separatc polymer of a complete block having a molecular
weight of about 5,000 would have a melting point of le~s than
200C.
I The bond between ad~acent polyether and polyester
blocks is suitably an ester-linkage produeed by reaction
of, for example, a hydroxyl-terminated polyether with a
carbosyl-terminated polyester. The block copolymer may be
prepared $rom a reaction mixture of (a) a polyether, allphatic ~ -
acid polyester or olefin polymer, having two terminal hydroxyl
groups, and (b) the reactants from which the polyester reaction
product ie derived. For example, the block copoiymer may be
made by melt copolymerisation of poly(tetramethylene ether)
diol, 1,4-butane diol, dimethyl terephthalate and dimethyl
isophthalate, or a~ternati~ely by melt copolymeri~ation of
poly(tetramethylene ether) diol, 1,3-propane diol, 1,4-butane
diol and dimethyl terephthPlate.
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~037848
Preferred block copolymers are those available under
- the trade names Hytrel and Pelpren.
The polyester may be in a composition with ingredients
normally present in polyester compositions, for example
fillers, processing aids and anti-ageing agents.
In the method of this invention, the polyester may be
melted by direct application of heat with or without an
elevated pressure. Since the polyester is normally thermo-
plastic before and after bonding, solidification normally
occurs by mere cooling. Preferred methods of applying the
polyester to the rubber are by injection-moulding or
transfer-moulding, but other technia~ues such as compression-
moulding, rotational-moulding, extrusion, powder-spraying
or fluidised-bed coating may be employed if desired.
The invention is illustrated in the following
Examples.
EXAMPLE I
' A rubber composition prepared from the following
;- formulation was w lcanized for 40 minutes at 150C. in a
mould measuring 4.0 x 76.2 x 228.6 mm.
Formulation Parts bY weiaht
Natural rubber (SMR 10) lOO
Carbon black (N330) 49.15
Mineral Oil 5.0
Zinc oxide 5 0
Stearic acid 1 2.0
Sulphur 2.5
N-cyclohexyl benzthiazole-2-sulphenamide 0.5
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1037~8
Formulation Parts bv wei~ht
4-isopropylamino-diphenylamine
(Nonox ZA)* 0.15
Condensation product of acetone and di-
phenylamine adsorbed on carbon black
(Nonox BLB)* 1.70
The natural rubber had about 25 C=C per 100 main-chain
carbon atoms.
One end of the slab of vulcanized rubber was immersed
at a depth of 180 mm for five minutes in an acid hypochlorite
10 solution consisting of:-
..
Water 1000 ml -
Concentrated hydrochloric acid 5 ml
Aqueous sodium hypochlorite solution
containing 12 weight/volume per cent
15 of available chlorine 30 ml
, . .~
The treated slab was allowed to dry and then placed
in a plunger mould of the same dimensions. A sheet of a
linear block copolymer containing 42% by weight polytetra-
hydrofuran and 58% by weight poly(butylene terephthalate),
` 20 commercially available under the trade name Hytrel 4055,
was compression moulded onto the 76.2 x 228.6 mm surface
, of the slab at 250C until the plastic was molten, followed
;, by cooling under a slight pressure (about 40 kg/cm2). No
i bond was produced between the block copolymer and the
untreated rubber surface. The strength of the bond between
the block copolymer and the hypochlorite-treated rubber
surface was determined by a simple peel adhesion test
at a jaw separation rate bf 500 mm per minute. A bond
strength of 147 Newtons per 20 mm wide test-piece was
obtained with failure of the rubber.
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1037848
EXAMPLE II
A rubber composition prepared from the formulation
- given in Example I was vulcanized for 55 minutes at 135 C
in a mould measuring 2.5 x 76.2 x 228.6 mm. A slab measuring
2.5 x 76.2 x 30 mm was cut from the vulcanized composition
and was immersed for 1 minute in an acid hypochlorite
solution consisting of:-
Water 1000 ml
Concentrated hydrochloric acid 10 ml
10 Aqueous sodium hypochlorite solution 5
containing 12 weight/volume per cent
! of available chlorine 30 ml ~ -
The treated slab was washed in water, allowed to dry
; and then placed in a mould measuring 7.0 x 76.Z x 30 mm.
Poly(tetramethylene terephthalate), commercially available
as Dereton TAP10 , was injected into the mould from a
Batenfeld 1/2 oz Type BSKM 15 HKF 4 injection-moulding machine
2 ~ -
under a pressure of 700 kg/cm which was maintained for `~
12 seconds. The mould and injector nozzle were respectively '~
20 at 140 C and 265 C. After cooling for a total time of 40
seconds the composite was de-moulded. ''
The strength of the bond between the rubber and the
polydster was determined by peel adhesion at a jaw
separation rate of 500 mm per minute. A bond strength of
25 216 Newtons per 30 mm wide test-piece was obtained with
.
failure in the rubber phase.
' EXAMPLE III
Example II was repeated using a rubber composition
prepared from the formulation given below which was
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~37~4B
vulcanized for 40 minutes at 150 C.
Parts by weight
Styrene/butadiene rubber (Intol 1502) 100
Carbon black (N330) 48.75
Mineral oil 5.0
Zinc oxide 3.0
Sulphur 1.75
Stearic acid 1.0
N-cyclohexyl benthiazole-2-sulphenamide 1.0
4-isopropylamino-diphenylamine (Nonox ZA) 0.15
*
BLE 25 1.25 1 -
The rubber had about 19 C=C per 100 main-chain carbon ~ -
atoms. ;
BLE is a high temperature reaction product of diphenyl- -~
amine and acetone.
A bond strength of 235 Newtons per 30 mm wide test-piece
was obtained with failure in the rubber phase.
; EXAMPLE IV ~ -
A rubber composition prepared from the formulation
given below was vulcanized for 40 minutes at 150 C in a
mould measuring 2.5 x 76.2 x 228.6 mm.
Parts by weight
Oil-extended styrene/butadiene rubber
(Intol 1712) 77.5
Styrene/butadiene rubber (Intol 1502) 22.5
' Carbon black (N339) 59.0
Aromatic oil ~Dutrex RT) 5.0
j Zinc oxide 2.5
Stearic acid 1.0
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1037~4~
Parts bY wel~ht
~ineral oil 5.0
4-isopropylamino_diphenylamine (Nonox ZA) 2.0
BIE 25 2.0
40 mesh crumb natural rubber 5.0
B ~-nitrOso-diphenylamine (Vulcatard A)~ 0.4 2-Morpholinothio-benzthiazole (Santocure ~OR) 1~0
Sulphur 1075
The rubbers hsd about 19 C=C per 100 main-chain carbon
atom3.
A slab measuring 2.5 x 76.2 x 30 mm was cut from the
vulcanized composition and was treated with the acid -~
hypochlorite solution as described in Example II. The
treated slab was washed with water, allowed to dry and then ~ -
placed in a mould measuring 7.0 x 76.2 x 30 mm. A block ~- ~
copolymer containing 35.5% by weight polytetrahydrofuran --
and 64.5% by weight poly(butylene terephthalate), ~ -
commercially available under the trade ~ 4 Hytrel 5555,
was lnjected into the mould at a pressure of 210 k~ cm2
which was maintained for 12 seconds. The mould and injector
nozzle were at 100C and 260C respectively. After cooling
for a total time of 40 seconds, the composite was de-moulded.
; The peel adhesion strength of the bond between the
rubber and the block copolymer measured at a jaw separation
rate of 500 mm per minute was 324 Newtons per 30 mm wide
test-piece with fallure of the rubber.
EXAMP~E V
Example IV was repeated except that the block copolymer
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12
' i
7848
was a copolymer of polytetrahydrofuran and poly(ethylene
terephthalate), commercially available under the Trade Mark
Pelpren P7os~ and the injector nozzle temperature was 250C.
m e peel adhesion bond strength was 274 Newtons per
5 30 mm wide test-piece with failure of the rubber. -
EXAMPLE VI
A hypochlorite-treated vulcanized rubber composition
was prepared as described in Example III. m e treated slab
was washed with water, allowed to dry and placed in a mould -~ -
- 10 measuring 7.0 x 76.2 x 30 mm. A glass-reinforced poly(tetra-
methylene terephthalate) containing 20 weight per cent glass
reinforcement and commercially available under the trade mark
-' Dereton T&A50 was injected into the mould at a pressure of
500 kg/cm2 which was maintained for 12 seconds. m e mould
and injector nozzle temperatures were respectively at 100C.
and 260C. After cooling for a total time of 24 seconds the
composite was de-moulded.
Failure occurred in the rubber upon testing of the
bond strength.
~MPLE VII
A vulcanized rubber composltion was prepared as
described in Example II. A slab measuring 2.5 x 76.2 x 30 mm
was cut from the vulcanized composition and was immersed in a
saturated aqueous solution of sodium dichloroisocyanurate,
available under the trade mark Fi-clor 60S, for 15 minutes.
The treated slab was washed with water, allowed to dry and
placed in a mould m~asuring 7.0 x 76.2 x 30 mm. Poly(tetra-
methylene terephthalate), commercially available under the
Trade Mark Tenite
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1~37E~
6PR0, was injected into the mould under a pressure of 700
kg/cm2 which was maintained for 12 seconds. The mould and
injector nozzle temperatures were 100C and 260C respectively.
After cooling for a total time of 24 seconds the composite was
de-moulded.
Upon testing the bond strength, failure occurred in
the rubber.
EXAMPLE VIII
Example VII was repeated except that the vulcanized
rubber slab was treated by painting the slab surface with
a saturated ethyl acetate solution of trichloroisocyanuric
acid, available under the trade mark Fi-clor 91, and leaving
- it to dry at room temperature.
Failure occurred in the rubber upon testing the bond
strength.
The same result was obtained when the treatment agent
was applied by immersion in the Fi-clor 91 solution for 5
minutes followed by washing with water and drying. ;
EXAMPLE IX
Example VII was repeated except that the vulcanized
rubber slab was treated by immersion in commercially
available concentrated nitric acid for 30 seconds before .
washing with water and drying.
Failure occurred in the rubber on testing the bond - -
strength.
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