U.S. patent application number 11/096068 was filed with the patent office on 2005-10-06 for carcass reinforcement for tire intended to bear heavy loads.
This patent application is currently assigned to MICHELIN RECHERCHE ET TECHNIQUE S.A.. Invention is credited to Chauvin, Brigitte.
Application Number | 20050222318 11/096068 |
Document ID | / |
Family ID | 35055258 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050222318 |
Kind Code |
A1 |
Chauvin, Brigitte |
October 6, 2005 |
Carcass reinforcement for tire intended to bear heavy loads
Abstract
A carcass reinforcement for a tire which is intended to bear
heavy loads, comprising a composite fabric which comprises a rubber
composition of reduced hysteresis and metal cables reinforcing the
composition. The elastomeric matrix thereof comprises natural
rubber or a synthetic polyisoprene in a majority proportion, and a
reinforcing filler comprising a carbon black which meets all of the
following conditions: (i) 45.ltoreq.CTAB specific surface area in
m.sup.2/g (in accordance with Standard ASTM D3765-80).ltoreq.70,
(ii) 45.ltoreq.BET specific surface area in m.sup.2/g (in
accordance with Standard ASTM D4820-93).ltoreq.70, (iii)
45.ltoreq.iodine adsorption index IA in mg/g (in accordance with
Standard ASTM D1510-81).ltoreq.70, (iv) ratio (BET surface
area/index IA).ltoreq.1.07, (v) 115.ltoreq.DBP structure value in
ml/100 g (in accordance with Standard ASTM D2414-93).ltoreq.170,
(vi) 85 nm.ltoreq.Stokes diameter dst in nm.ltoreq.145, where dst
is the diameter of aggregates corresponding to the maximum
frequency of the Stokes diameters in a distribution of aggregates,
and (vii) D50/dst.gtoreq.0.0090. CTAB+0.19, where D50 is the
difference, in the distribution of aggregates, between the Stokes
diameters of two aggregates corresponding to one and the same
frequency equal to 50% of the maximum frequency of the Stokes
diameters, dst and D50 being measured by centrifugal
photosedimentometry.
Inventors: |
Chauvin, Brigitte;
(Chamalieres, FR) |
Correspondence
Address: |
BUCHANAN INGERSOLL PC
(INCLUDING BURNS, DOANE, SWECKER & MATHIS)
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
MICHELIN RECHERCHE ET TECHNIQUE
S.A.
GRANGES-PACCOT
CH
|
Family ID: |
35055258 |
Appl. No.: |
11/096068 |
Filed: |
April 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11096068 |
Apr 1, 2005 |
|
|
|
PCT/EP03/10521 |
Sep 22, 2003 |
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Current U.S.
Class: |
524/496 |
Current CPC
Class: |
C08K 3/04 20130101; C08K
3/04 20130101; C08L 9/00 20130101; C08K 3/04 20130101; C08K 3/04
20130101; B60C 2009/0276 20130101; C08L 7/00 20130101; C08L 21/00
20130101; C08L 2666/08 20130101; C08L 9/00 20130101; B60C 1/0041
20130101; B60C 2009/0021 20130101; C08L 21/00 20130101 |
Class at
Publication: |
524/496 |
International
Class: |
C08K 003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2002 |
FR |
02/12213 |
Claims
1. A carcass reinforcement for a tire which is intended to bear
heavy loads, said reinforcement comprising a composite fabric which
comprises a cross-linkable or cross-linked rubber composition
having a reduced hysteresis in the cross-linked state and metal
cables reinforcing said composition, which comprises: an
elastomeric matrix comprising natural rubber or a synthetic
polyisoprene in a majority proportion, and a reinforcing filler
comprising a carbon black, wherein said carbon black meets all of
the following conditions: (i) 45.ltoreq.CTAB specific surface area
in m.sup.2/g (in accordance with Standard ASTM D3765-80).ltoreq.70,
(ii) 45.ltoreq.BET specific surface area in m.sup.2/g (in
accordance with Standard ASTM D4820-93).ltoreq.70, (iii)
45.ltoreq.iodine adsorption index IA in mg/g (in accordance with
Standard ASTM D1510-81).ltoreq.70 (iv) ratio (BET surface
area/index IA).ltoreq.1.07, (v) 115.ltoreq.DBP structure value in
ml/100 g (in accordance with Standard ASTM D2414-93).ltoreq.170,
(vi) 85 nm.ltoreq.Stokes diameter dst in nm.ltoreq.145, where dst
is the diameter of aggregates corresponding to the maximum
frequency of the Stokes diameters in a distribution of aggregates,
and (vii) D50/dst.gtoreq.0.0090. CTAB+0.19, where D50 is the
difference, in the distribution of aggregates, between the Stokes
diameters of two aggregates corresponding to one and the same
frequency equal to 50% of the maximum frequency of the Stokes
diameters, dst and D50 being measured by centrifugal
photosedimentometry.
2. The carcass reinforcement according to claim 1, wherein said
carbon black furthermore meets the following condition: (viii)
80.ltoreq.DBPC structure value in ml/100 g (in accordance with
Standard ASTM D3493-91).ltoreq.130, the value DBPC being measured
after 4 compressions at 24,000 psi.
3. The carcass reinforcement according to claim 2, wherein said
carbon black furthermore meets the following condition: (ix)
85.ltoreq.DBPC structure value in ml/100 g.ltoreq.125.
4. The carcass reinforcement according to claim 1, wherein said
carbon black further meets the following conditions: (x)
50.ltoreq.CTAB specific surface area in m.sup.2/g.ltoreq.65, (xi)
50.ltoreq.BET specific surface area in m.sup.2/g.ltoreq.65, (xii)
50.ltoreq.iodine adsorption index IA in mg/g.ltoreq.65.
5. The carcass reinforcement according to claim 1, wherein said
carbon black further meets the following condition: (xiii) ratio
(BET surface area)/(index IA).ltoreq.1.05.
6. The carcass reinforcement according to claim 1, wherein said
carbon black further meets the following condition: (xiv)
120.ltoreq.DBP structure value in ml/100 g.ltoreq.165.
7. The carcass reinforcement according to claim 1, wherein said
carbon black further meets the following condition: (xv) 90
mn.ltoreq.Stokes diameter dst in nm.ltoreq.140.
8. The carcass reinforcement according to claim 1, wherein said
carbon black further meets the following condition: (xvi)
D50/dst.gtoreq.0.0092. CTAB +0.21.
9. The carcass reinforcement according to claim 1, wherein the
elastomeric matrix comprises natural rubber or synthetic
polyisoprene.
10. The carcass reinforcement according to claim 1, wherein said
elastomeric matrix comprises a blend of natural rubber or of
synthetic polyisoprene with at least one diene elastomer,
optionally functional, belonging to the group consisting of
polybutadienes, copolymers of styrene and butadiene prepared in
solution or in emulsion, copolymers of butadiene and isoprene and
terpolymers of styrene, butadiene and isoprene, the natural rubber
or the synthetic polyisoprene being present in said composition in
a quantity equal to or greater than 70 phr (phr:parts by weight per
hundred parts of elastomers).
11. The carcass reinforcement according to claim 1, wherein said
carbon black is present in said reinforcing filler in a mass
fraction greater than 50% and less than or equal to 100%.
12. The carcass reinforcement according to claim 11, wherein said
carbon black is present in said reinforcing filler in a mass
fraction of from 70% to 100%.
13. The carcass reinforcement according to claim 11, wherein said
reinforcing filler comprises a blend of said carbon black and a
reinforcing inorganic filler.
14. The carcass reinforcement according to claim 13, wherein said
reinforcing inorganic filler is a silica.
15. The carcass reinforcement according to claim 13, wherein said
reinforcing filler which comprises a blend of said carbon black and
a reinforcing organic filler further comprises a methylene
donor/methylene acceptor system.
16. The carcass reinforcement according to claim 15, wherein said
composition comprises: between 30 phr and 70 phr of said carbon
black, between 1 phr and 10 phr of said methylene acceptor, and
between 0.5 phr and 5 phr of said methylene donor.
17. The carcass reinforcement according to claim 15, wherein said
methylene acceptor is a phenolic resin.
18. The carcass reinforcement according to claim 17, wherein said
phenolic resin is a novolak phenolic resin.
19. The carcass reinforcement according to claim 15, wherein said
methylene donor is selected from the group consisting of
hexamethylenetetramine, hexamethoxymethylmelamine,
hexaethoxymethylmelamine, para-formaldehyde polymers, N-methylol
melamine derivatives, and mixtures of these compounds.
20. A carcass reinforcement according to claim 1, wherein said
composite fabric comprises said metal cables in a cable density of
between 15 and 100 cables per dm of fabric.
21. The carcass reinforcement according to claim 20, wherein the
distance between two adjacent radial cables, from axis to axis, is
of between 1 and 6 mm.
22. The carcass reinforcement according to claim 21, wherein the
width 1 of a rubber bridge between two adjacent cables is between
0.25 and 1.5 mm.
23. The carcass reinforcement according to claim 22, wherein said
width 1 of the rubber bridge is between 0.35 and 0.85 mm.
24. The carcass reinforcement according to claim 1, wherein said
rubber composition has, in the cross-linked state and measured in
accordance with Standard ASTM D 412, a secant tensile modulus M10
which is less than 12 MPa.
25. The carcass reinforcement according to claim 24, wherein said
rubber composition has, in the cross-linked state and measured in
accordance with Standard ASTM D 412, a secant tensile modulus M10
which is of between 5 and 11 MPa.
26. The carcass reinforcement according to claim 20, wherein said
cable density is between 50 and 80 cables per dm of fabric, said
reinforcement being intended for a heavy-vehicle tire.
27. The carcass reinforcement according to claim 26, wherein the
distance between two adjacent radial cables, from axis to axis, is
between 1.25 and 2 mm.
28. The carcass reinforcement according to claim 20, wherein said
cable density is of between 20 and 35 cables per dm of fabric, said
reinforcement being intended for a construction-machinery tire.
29. The carcass reinforcement according to claim 28, wherein the
distance between two adjacent radial cables, from axis to axis, is
between 2.5 and 5.5 mm.
30. A tire for a vehicle intended to bear heavy loads which
comprises a carcass reinforcement according to claim 1.
31. A tire for a heavy vehicle, which comprises a carcass
reinforcement according to claim 26.
32. A tire for construction machinery, which comprises a carcass
reinforcement according to claim 28.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of PCT Application
No. PCT/EP2003/010521, filed Sep. 22, 2003, published in French on
Apr. 15, 2004, as WO 2004/030946, which claims priority of French
Application No. 02/12213, filed Oct. 2, 2002, the entire contents
of both applications being incorporated herein in their
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a carcass reinforcement for
a tire which is intended to bear heavy loads, such as a
heavy-vehicle or construction-machinery tire, and to such a
heavy-vehicle or construction-machinery tire.
DESCRIPTION OF RELATED ART
[0003] Radial-carcass tires for motor vehicles bearing heavy loads,
in particular for heavy vehicles, comprise reinforcements which are
formed of reinforcing threads or plies of metal wires coated with
elastomers. More precisely, these tires comprise, in their bottom
zone, one or more bead wires, a carcass reinforcement extending
from one bead wire to the other and, in their crown, a crown
reinforcement comprising at least two crown plies.
[0004] These heavy-vehicle tires are designed to be able to be
retreaded one or more times when the treads which they comprise
reach a critical degree of wear after prolonged travel, which
involves having a carcass reinforcement which has not been subject
to significant damage, for each tire to be retreaded the tread of
which has reached this degree of wear.
[0005] When running under heavy load, the "band" of the carcass
(central zone on either side of the median circumferential plane of
the tire) is subjected to flexural stresses which may be very high,
hence the necessity of imparting a high mechanical strength to this
"band", and the bottom zone of the tire (close to each of the two
upturns of the carcass) may be the seat of operating temperatures
which are also very high, hence the necessity of imparting reduced
hysteresis to this bottom zone.
[0006] Consequently, with the aim of minimising the embrittlement
of the tire and of delaying the appearance of damage therein, a
carcass reinforcement of heavy-vehicle type must be both as
cohesive as possible, to resist the mechanical stresses during
travel, and of as low hysteresis as possible, to minimise the
heating during travel and also to limit the thermochemical and
possibly thermo-oxidising change of the internal compositions.
[0007] It is known to the person skilled in the art that the use,
in a rubber composition for a heavy-vehicle carcass reinforcement
and in a quantity of approximately 50 phr (parts by weight per
hundred parts of elastomer(s)), of a relatively structured grade
300 carbon black, such as the black N347, or a less structured one,
such as the black N326, makes it possible to improve the cohesion,
endurance and hysteresis of this composition, which imparts a
longer life to the carcass reinforcement and, consequently, to the
corresponding heavy-vehicle tire.
[0008] It is also known that coarse carbon blacks, such as the
black N539, only impart sufficient cohesion to a heavy-vehicle
carcass reinforcement composition if these blacks are present in
this composition in a very large quantity, which may have the
undesirable effect of adversely affecting the hysteresis of this
composition.
[0009] Japanese patent specification JP-A-04/274 901 discloses the
use of specific carbon blacks in rubber compositions which are
equally well intended for at least three distinct zones of a tire
having specifically a reduced weight, for imparting to this
lightweight tire improved properties of rolling resistance and
reinforcement, compared with those exhibited by a tire the same
zones of which comprise compositions each comprising a grade 300
carbon black.
[0010] These specific carbon blacks have a specific surface area
N.sub.2SA (measured in accordance with Standard ASTM D3037 of 1984)
of from 60 to 84 m.sup.2/g, a "DBP" structure value (measured in
accordance with Standard JIS K 6221) of from 120 to 200 m/100 g and
they have a surface chemistry which is such that the ratio
"N.sub.2SA/IA" of said specific surface area to the iodine
adsorption index "IA" (also measured in accordance with Standard
JIS K 6221) is equal to or greater than 1.10.
[0011] Japanese patent specification JP-A-02/103 268 discloses the
use of carbon blacks to improve the hysteresis and reinforcement
properties of rubber compositions for carcass reinforcements for
any tires, or even more generally intended for damping
vibrations.
[0012] These carbon blacks have a CTAB specific surface area
(measured in accordance with Standard ASTM D3765-80) of from 50 to
75 m.sup.2/g, a "DBP" structure value (measured in accordance with
Standard JIS K 6221) equal to or greater than 105 ml/100 g and they
have a surface chemistry which is such that the ratio
"N.sub.2SA/IA" of the specific surface area "N.sub.2SA" (measured
in accordance with Standard ASTM D3037-86) to the iodine adsorption
index "IA" (measured in accordance with Standard JIS K 6221) is
equal to or greater than 1.10.
[0013] It will be noted that these last two documents do not relate
to tires intended to bear heavy loads, and certainly not to a
carcass reinforcement of the type having metal cables which is
specifically intended to be fitted on such heavy-vehicle or
construction-machinery tires.
SUMMARY OF THE INVENTION
[0014] The object of the present invention is to propose a novel
carcass reinforcement for a tire which is intended to bear heavy
loads, such as a heavy-vehicle or construction-machinery tire, this
reinforcement comprising a composite fabric which comprises a
cross-linkable or cross-linked rubber composition having a reduced
hysteresis in the cross-linked state and metal cables reinforcing
this composition.
[0015] This object is achieved in that the Applicants have recently
surprisingly discovered that the association, with an elastomeric
matrix comprising natural rubber or a synthetic polyisoprene in a
majority proportion, of a reinforcing filler comprising a carbon
black which meets all the following conditions:
[0016] (i) 45.ltoreq.CTAB specific surface area in m.sup.2/g (in
accordance with Standard ASTM D3765-80).ltoreq.70,
[0017] (ii) 45.ltoreq.BET specific surface area in m.sup.2/g (in
accordance with Standard ASTM D4820-93).ltoreq.70,
[0018] (iii) 45.ltoreq.iodine adsorption index IA in mg/g (in
accordance with Standard ASTM D1510-81).ltoreq.70
[0019] (iv) ratio (BET surface area/index IA).ltoreq.1.07,
[0020] (v) 115.ltoreq.DBP structure value in ml/100 g (in
accordance with Standard ASTM D2414-93).ltoreq.170,
[0021] (vi) 85 nm.ltoreq.Stokes diameter dst in nm.ltoreq.145,
[0022] where dst is the diameter of aggregates corresponding to the
maximum frequency of the Stokes diameters in a distribution of
aggregates, and
[0023] (vii) D50/dst.gtoreq.0.0090. CTAB+0.19,
[0024] where D50 is the difference, in the distribution of
aggregates, between the Stokes diameters of two aggregates
corresponding to one and the same frequency equal to 50% of the
maximum frequency of the Stokes diameters, dst and D50 being
measured by centrifugal photosedimentometry,
[0025] makes it possible to obtain a rubber composition which has
in the cross-linked state improved hysteresis properties at high
deformations, in comparison with the hysteresis properties of known
compositions comprising a grade 300 carbon black and having
substantially one and the same modulus of elongation at low
deformation.
[0026] It will be noted that the carcass reinforcement according to
the invention comprises a carbon black having a ratio (BET surface
area/index IA) of reduced value and a ratio D50/dst which increases
with the CTAB specific surface area, these ratios imparting
respectively to the blacks according to the invention a surface
chemistry and a morphology which are particularly suitable.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The elastomeric matrix of the rubber composition according
to the invention may advantageously be formed of natural rubber or
synthetic polyisoprene, or alternatively of a blend of natural
rubber or synthetic polyisoprene with one or more other diene
elastomers.
[0028] In this second case, the natural rubber or the synthetic
polyisoprene is present in a majority proportion in the matrix,
that is to say in a quantity greater than 50 phr (parts by weight
per hundred parts of elastomers). Preferably, the natural rubber or
the polyisoprene is present in a quantity equal to or greater than
70 phr.
[0029] Among the diene elastomers which may be used in a blend with
the natural rubber or the synthetic polyisoprene, mention may be
made of the diene elastomers, whether functional or not, belonging
to the group consisting of polybutadienes, copolymers of styrene
and butadiene (SBR) prepared in solution or in emulsion, copolymers
of butadiene and isoprene (BIR) and terpolymers of styrene,
butadiene and isoprene (SBIR).
[0030] Preferably, the polybutadiene used comprises a majority of
cis-1,4 linkages and the SBR used comprises a majority of trans-1,4
linkages.
[0031] These elastomers may be modified during polymerisation or
after polymerisation by means of branching agents such as
divinylbenzene, or coupling or starring agents such as carbonates,
halo-tins, halo-silicons, or alternatively by means of
functionalising agents resulting in grafting on the chain or at the
chain end of hydroxyl, carbonyl, carboxyl groups or alternatively
of amine groups (for example by means of dimethylamino-benzophenone
or diethylamino-benzophenone as functionalising agent).
[0032] According to another characteristic of the invention, said
carbon black furthermore satisfies the following condition:
[0033] (viii) 80.ltoreq.DBPC structure value in ml/100 g (in
accordance with Standard ASTM D3493-91).ltoreq.130,
[0034] DBPC being measured after 4 compressions at 24,000 psi.
[0035] Preferably, said carbon black furthermore meets the
following condition:
[0036] (ix) 85.ltoreq.DBPC structure value in ml/100
g.ltoreq.125.
[0037] Preferably, the carbon black used in the composition
according to the invention furthermore meets the following three
conditions:
[0038] (x) 50.ltoreq.CTAB specific surface area in
m.sup.2/g.ltoreq.65,
[0039] (xi) 50.ltoreq.BET specific surface area in
m.sup.2/g.ltoreq.65,
[0040] (xii) 50.ltoreq.iodine adsorption index IA in
mg/g.ltoreq.65.
[0041] Equally preferably, said carbon black furthermore meets the
condition:
[0042] (xiii) ratio (BET surface area)/(index IA).ltoreq.1.05.
[0043] Equally preferably, said carbon black furthermore meets the
condition:
[0044] (xiv) 120.ltoreq.DBP structure value in ml/100
g.ltoreq.165.
[0045] Equally preferably, said carbon black furthermore meets the
condition:
[0046] (xv) 90 nm.ltoreq.Stokes diameter dst in nm.ltoreq.140.
[0047] Equally preferably, said carbon black furthermore meets the
condition:
[0048] (xvi) D50/dst.gtoreq.0.0092. CTAB+0.21.
[0049] The values dst and D50 are measured by means of a
centrifugal photosedimentometer of type "DCP" (Disk Centrifuge
Photosedimentometer), sold by Brookhaven Instruments. The operating
method for these measurements is as follows:
[0050] A sample of carbon black is dried, in accordance with
Standard JIS K6221 (1975). Then 10 mg of carbon black thus dried is
suspended in 40 ml of an aqueous solution of 15% ethanol and 0.05%
of a non-ionic surfactant (by volume).
[0051] The dispersion of carbon black is obtained by ultrasound
treatment for 10 minutes, by means of a 600 Watt ultrasonic probe.
To this end an ultrasound generator designated "Vibracell 1/2 inch"
sold by Bioblock and adjusted to 60% of its power (namely to 60% of
maximum amplitude) is used.
[0052] A gradient solution composed of 15 ml water (with 0.05%
non-ionic surfactant) and 1 ml ethanol is injected into the disc of
the sedimentometer, rotating at 8,000 rpm, then 0.30 ml of the
suspension of carbon black is injected on to the surface of the
gradient solution. The mass size distribution curve is recorded for
120 minutes. A software program provides said values dst and D50 in
nm.
[0053] The carbon black according to the invention may be used on
its own as reinforcing filler, or alternatively in a blend with a
reinforcing organic filler and/or a reinforcing inorganic filler.
The quantity of carbon black used may vary from 30 phr to 70 phr
and, preferably, from 35 to 65 phr.
[0054] In the case of a blend with a reinforcing organic or
inorganic filler, said carbon black is present in a majority
proportion in the reinforcing filler (i.e. in a mass fraction
greater than 50%). Preferably, the mass fraction of carbon black in
the reinforcing filler is greater than 70%.
[0055] According to a particularly advantageous embodiment of the
invention, the reinforcing organic filler comprises a methylene
acceptor/donor system (what is called an "M.A.D." system), which
designates compounds suitable for reacting together to generate a
three-dimensional reinforcing resin by condensation.
[0056] In known manner, the term "methylene acceptor" designates
the reactant with which the methylene donor compound reacts by
formation of methylene bridges (--CH2--), upon the curing of the
composition, thus resulting in the formation in situ of the
three-dimensional resin lattice. The methylene acceptor must be
capable of dispersing perfectly in the elastomeric matrix.
[0057] Particularly suitable as methylene acceptors are phenols,
the generic name for hydroxylated derivatives of arenes, and the
equivalent compounds. This definition covers in particular
monophenols, for example phenol or hydroxybenzene, bisphenols,
polyphenols (polyhydroxyarenes), substituted phenols such as
alkylphenols or aralkylphenols, for example bisphenols,
diphenylolpropane, diphenylolmethane, naphthols, cresol,
t-butylphenol, octylphenol, nonylphenol, xylenol, resorcinol or
analogous products.
[0058] Preferably phenolic resins referred to as "novolac resins",
also called phenol-aldehyde precondensates, resulting from the
precondensation of phenolic compounds and aldehydes, in particular
formaldehyde, are used as methylene acceptor. In known manner,
these novolac resins (also referred to as "two-step resins") are
thermoplastic and require the use of a curing agent (methylene
donor) to be cross-linked, unlike, for example, Resols.RTM. which
are thermohardening; they have sufficient plasticity not to
interfere with the processing of the rubber composition. After
cross-linking by the methylene donor (they may then be referred to
as "thermohardened" novolac resins), they are characterised in
particular by a tighter three-dimensional lattice than that of the
Resols.RTM..
[0059] The quantity of methylene acceptor must be between 1 and 10
phr; below 1 phr, the technical effect desired is inadequate,
whereas beyond 10 phr there are risks of excessive stiffening and
excessive compromising of the hysteresis. For all these reasons, a
quantity of between 1.5 and 8 phr is more preferably selected,
amounts lying within a range from 2 to 4 phr being particularly
advantageous.
[0060] A curing agent, capable of cross-linking or hardening the
methylene acceptor previously described, also commonly referred to
as "methylene donor", must be associated with this acceptor.
[0061] Preferably, the methylene donor is selected from the group
consisting of hexamethylenetetramine ("HMT"),
hexamethoxymethylmelamine ("H3M"), hexaethoxymethylmelamine,
formaldehyde polymers such as p-formaldehyde, N-methylol
derivatives of melamine, or mixtures of these compounds. More
preferably, this donor is selected from among HMT, H3M or a mixture
of these compounds.
[0062] The quantity of methylene donor must be between 0.5 and 5
phr; below 0.5 phr, the technical effect desired is inadequate,
whereas beyond 5 phr there are risks of compromising the processing
in the uncured state of the compositions (for example, problem of
solubility of the HMT) or of the vulcanisation (slowing in the
presence of H3M). For these reasons, a quantity of between 0.5 and
3.5 phr is more preferably selected, amounts lying within a range
from 1 to 3 phr being particularly advantageous.
[0063] Finally, the quantity of methylene donor, in the
aforementioned ranges, is advantageously adjusted so as to
represent between 10% and 80%, more preferably within a range from
40 to 60%, by weight relative to the quantity of methylene
acceptor.
[0064] In the present application, "reinforcing inorganic filler",
in known manner, is understood to mean an inorganic or mineral
filler, whatever its colour and its origin (natural or synthetic),
also referred to as "white" filler or sometimes "clear" filler in
contrast to carbon black, this inorganic filler being capable, on
its own, without any other means than an intermediate coupling
agent, of reinforcing a rubber composition intended for the
manufacture of tires, i.e. capable of replacing a conventional
tire-grade carbon black filler in its reinforcement function.
[0065] Preferably, all or at the very least a majority proportion
of the reinforcing inorganic filler is silica (SiO.sub.2). The
silica used may be any reinforcing silica known to the person
skilled in the art, in particular any precipitated silica having a
BET surface area and a CTAB specific surface area both of which are
less than 450 m.sup.2/g, even if the highly dispersible
precipitated silicas are preferred. Even more preferably, the
silica has BET or CTAB specific surface areas both of which are
from 70 to 250 m.sup.2/g and, preferably, from 80 to 240
m.sup.2/g.
[0066] The BET specific surface area of the silica is determined in
known manner, in accordance with the method of Brunauer, Emmett and
Teller described in "The Journal of the American Chemical Society"
vol. 60, page 309, February 1938, corresponding to Standard
AFNOR-NFT 45007 (November 1987); the CTAB specific surface area is
the external surface area determined in accordance with the same
Standard AFNOR-NFT-45007 of November 1987.
[0067] "Highly dispersible silica" is understood to mean any silica
having a very substantial ability to disagglomerate and to disperse
in an elastomeric matrix, which can be observed in known manner by
electron or optical microscopy on thin sections. As non-limitative
examples of such preferred highly dispersible silicas, mention may
be made of the silicas [sic] Perkasil KS 430 from Akzo, the silicas
BV3380 and BV3370GR from Degussa, the silicas Zeosil 1165 MP and
1115 MP from Rhodia, the silica Hi-Sil 2000 from PPG, the silicas
Zeopol 8741 or 8745 from Huber, and treated precipitated silicas
such as, for example, the aluminium-"doped" silicas described in
European patent specification EP-A-0 735 088.
[0068] Other silicas which are not highly dispersible, such as the
silica Perkasil KS404 from Akzo and the silicas Ultrasil VN2 or
VN3, may also be used.
[0069] The physical state in which the reinforcing inorganic filler
is present is immaterial, whether it be in the form of a powder,
microbeads, granules or alternatively balls. Of course,
"reinforcing inorganic filler" is also understood to mean mixtures
of different reinforcing inorganic fillers, in particular of highly
dispersible silicas such as described above.
[0070] As reinforcing inorganic filler, it is also possible to use,
although this is not limiting, aluminas (of formula
Al.sub.2O.sub.3), such as the aluminas of high dispersibility which
are described in European patent specification EP-A-810 258, or
alternatively aluminium hydroxides, such as those described in
international patent specification WO-A-99/28376.
[0071] Also suitable as reinforcing inorganic fillers are carbon
blacks modified by silica, such as, although this is not limiting,
the fillers sold by CABOT under the name "CRX 2000", which are
described in international patent specification WO-A-96/37547.
[0072] In the event that the carbon black according to the
invention is used in a blend with a reinforcing inorganic filler,
the rubber composition according to the invention may furthermore
comprise in conventional manner a reinforcing inorganic
filler/elastomeric matrix bonding agent (also referred to as
coupling agent), the function of which is to ensure sufficient
chemical and/or physical bonding between said inorganic filler and
the matrix, while facilitating the dispersion of the inorganic
filler within the matrix.
[0073] "Coupling agent" is more precisely understood to mean an
agent capable of establishing a sufficient chemical and/or physical
connection between the filler in question and the elastomer, while
facilitating the dispersion of this filler within the elastomeric
matrix. Such a coupling agent, which is at least bifunctional, has,
for example, the simplified general formula "Y-T-X", in which:
[0074] Y represents a functional group ("Y" function) which is
capable of bonding physically and/or chemically with the inorganic
filler, such a bond being able to be established, for example,
between a silicon atom of the coupling agent and the surface
hydroxyl (OH) groups of the inorganic filler (for example, surface
silanols in the case of silica);
[0075] X represents a functional group ("X" function) which is
capable of bonding physically and/or chemically with the elastomer,
for example by means of a sulphur atom;
[0076] T represents a group making it possible to link Y and X.
[0077] Silica/elastomer coupling agents in particular have been
described in a large number of documents, the best known being
bifunctional alkoxysilanes such as polysulphurised
alkoxysilanes.
[0078] As polysulphurised alkoxysilanes, mention will be made more
particularly of the polysulphides (in particular disulphides,
trisulphides or tetrasulphides) of
bis-((C.sub.1-C.sub.4)alkoxyl-(C.sub.1-
-C.sub.4)alkylsilyl-(C.sub.1-C.sub.4)alkyl), such as for example
the polysulphides of bis(3-trimethoxysilylpropyl) or of
bis(3-triethoxysilylpropyl). Of these compounds, in particular
bis(3-triethoxysilylpropyl) tetrasulphide, abbreviated TESPT, of
the formula
[(C.sub.2H.sub.5O).sub.3Si(CH.sub.2).sub.3S.sub.2].sub.2, or
bis(triethoxysilylpropyl) disulphide, abbreviated TESPD, of the
formula [(C.sub.2H.sub.5O).sub.3Si(CH.sub.2).sub.3S].sub.2, are
used. TESPD is sold, for example, by Degussa under the names Si266
or Si75 (in the latter case, in the form of a mixture of disulphide
(75% by weight) and of polysulphides), or alternatively by Witco
under the name Silquest A1589. TESPT is sold, for example, by
Degussa under the name Si69 (or X50S when it is supported to 50% by
weight on carbon black), or alternatively by Osi Specialties under
the name Silquest A1289 (in both cases, a commercial mixture of
polysulphides having an average value of n close to 4). Mention
will also be made of tetrasulphurised monoalkoxysilanes, such as
monoethoxydimethylsilylpropyl tetrasulphide (abbreviated to MESPT),
which are the subject of international patent application
PCT/EP02/03774.
[0079] The compositions according to the invention are capable of
cross-linking under the action of sulphur, peroxides or
bismaleimides with or without sulphur. They may also contain the
other constituents conventionally used in rubber mixes, such as a
conventional non-reinforcing inorganic filler (for example clay,
bentonite, talc, chalk, kaolin or titanium oxides), plasticisers,
pigments, antioxidants, processing agents, cross-linking
accelerators such as benzothiazole derivatives, diphenylguanidine
and, in the present case of rubber compositions for carcass
reinforcements provided to have satisfactory adhesion to metal, a
cobalt salt and/or a silica/resin association.
[0080] The compositions according to the invention may be prepared
using known thermomechanical working processes for the constituents
in one or more stages. For example, they may be obtained by
thermomechanical working in an internal mixer in one stage which
lasts from 3 to 7 minutes, with a speed of the blades of 50 rpm, or
in two stages which last from 3 to 5 minutes and from 2 to 4
minutes respectively, this thermomechanical working being followed
by mechanical working or a finishing stage effected at about
80.degree. C., during which the sulphur, the vulcanisation
accelerators (in the case of a sulphur-cross-linked composition)
and possibly said cobalt salt are incorporated.
[0081] In the event that a reinforcing organic filler of type
methylene acceptor/donor system is used in the composition
according to the invention, the methylene donor is only introduced
during the step of mechanical working, unlike the methylene
acceptor, which is introduced during the thermomechanical
working.
[0082] The carcass reinforcement according to the invention is
preferably such that, in the composite fabric used as heavy-vehicle
or construction-machinery carcass ply, the density of the metal
cables is of between 15 and 100 cables per dm of radial ply and the
distance between two adjacent radial cables, from axis to axis, is
preferably of between 1 and 6 mm.
[0083] In a heavy-vehicle carcass ply, this cable density is
preferably of between 40 and 100 cables per dm, more preferably
between 50 and 80 cables per dm, and the distance between two
adjacent radial cables, from axis to axis, is preferably of between
1.0 and 2.5 mm, more preferably between 1.25 and 2 mm.
[0084] In a construction-machinery carcass ply, this cable density
is preferably of between 15 and 70 cables per dm, more preferably
between 20 and 35 cables per dm, and the distance between two
adjacent radial cables, from axis to axis, is preferably of between
2 and 6 mm, more preferably between 2.5 and 5.5 mm.
[0085] These cables according to the invention are preferably
arranged such that the width ("1") of the rubber bridge between two
adjacent cables is of between 0.25 mm and 1.5 mm. In a
heavy-vehicle carcass ply, the width 1 is more preferably of
between 0.25 and 1 mm and, in a construction-machinery carcass ply,
this width 1 is more preferably of between 0.25 and 1.5 mm.
[0086] This width 1 in known manner represents the difference
between the calendering pitch (laying pitch of the cable in the
rubber fabric) and the diameter of the cable. Below the minimum
value indicated, the rubber bridge, which is too narrow, risks
mechanically degrading during working of the ply, in particular
during the deformation which it experiences in its own plane by
extension or shearing. Beyond the maximum indicated, there are
risks of flaws in appearance occurring on the sidewalls of the
tires or of penetration of objects, by perforation, between the
cables.
[0087] For these reasons, the width 1 is even more preferably
selected to be between 0.35 and 0.85 mm, be it for a heavy-vehicle
or construction-machinery carcass ply.
[0088] Equally preferably, the rubber composition of this composite
fabric has, in the cross-linked state (i.e., after curing) and
measured in accordance with Standard ASTM D 412, a secant tensile
modulus M10 which is less than 12 MPa, more preferably of between 5
and 11 MPa. It is within such a field of moduli that the best
compromise of endurance in the composite fabrics of the carcass
reinforcement has been recorded.
[0089] A heavy-vehicle or construction-vehicle tire according to
the invention is such that it comprises this carcass
reinforcement.
[0090] This heavy-vehicle or construction-machinery tire comprises
in known manner a crown, two sidewalls and two beads, each of these
beads being reinforced by a bead wire. The crown is conventionally
reinforced by a crown reinforcement formed for example of at least
two superposed crossed plies, reinforced by metal cables. The
carcass reinforcement is wound around the two bead wires within
each bead, the upturn of the reinforcement being for example
arranged towards the outside of the tire.
[0091] The carcass reinforcement is formed of at least one ply
reinforced by so-called "radial" metal cables, that is to say that
they are arranged practically parallel to each other and extend
from one bead to the other, forming an angle of between 80.degree.
and 90.degree. with the median circumferential plane (plane
perpendicular to the axis of rotation of the tire which is located
halfway between the two beads and passes through the centre of the
crown reinforcement).
[0092] The aforementioned characteristics of the present invention,
as well as others, will be better understood on reading the
following description of several examples of embodiment of the
invention, which are given by way of illustration and not of
limitation.
[0093] In these examples, the properties of the compositions are
evaluated as follows:
[0094] Mooney Viscosity
[0095] The Mooney viscosity ML (1+4) is measured in accordance with
Standard ASTM D1646 (1999).
[0096] Shore A Hardness
[0097] The Shore A hardness is measured in accordance with standard
ASTM D2240 (1997).
[0098] Moduli of Elongation
[0099] The moduli of elongation are measured at 10% (M10) at a
temperature of 23.degree. C. in accordance with Standard ASTM D412
(1998) on ASTM C test pieces. These are true secant moduli in MPa,
that is to say the secant moduli calculated reduced to the real
cross-section of the test piece at the given elongation.
[0100] Break Indices
[0101] These indices are measured at 100.degree. C. The properties
at break, breaking stress FR in MPa and elongation at break AR in %
are measured in accordance with Standard ASTM D412 (1998). The
measurements are carried out on ASTM C test pieces.
[0102] Tearability Indices
[0103] These indices are measured at 100.degree. C. The breaking
load (FRD) in N/mm of thickness and the elongation at break (ARD)
in % are measured on a test piece of dimensions
10.times.105.times.2.5 mm notched at its centre over a depth of 5
mm.
[0104] Hysteresis Losses (HL)
[0105] They are measured in % by rebound at 60.degree. C. at the
sixth impact, in accordance with the equation:
HL (%)=100.times.(W.sub.0-W.sub.1)/W.sub.1, with W.sub.0: energy
supplied and W.sub.1: energy restored.
[0106] Dynamic Properties
[0107] The dynamic characteristics of the materials are analysed on
a Schenck machine, in accordance with Standard ASTM D 5992 (1996).
The response of a sample of vulcanised material (cylindrical test
piece of a thickness of 4 mm and a section of 400 mm.sup.2),
subjected to an alternating single sinusoidal shearing stress, at a
frequency of 10 Hz and at 60.degree. C., is recorded. Scanning is
effected at an amplitude of deformation of 0.1 to 50% (outward
cycle), then of 50% to 0.1% (return cycle). The maximum shear
modulus G*max in MPa and the maximum value of the tangent of the
loss angle tan delta max is determined during the outward
cycle.
EXAMPLES OF EMBODIMENT OF THE INVENTION
1) First Series of Examples
[0108] The object of these examples is to compare compositions
based on natural rubber (NR hereafter) reinforced with carbon
black, with quantities of black of from 52 to 58 phr. These
compositions are specified in Table 1 hereafter (in phr).
[0109] The "control" composition 1 is representative of the known
prior art, and comprises 52 phr of black N347 as reinforcing
filler.
[0110] Compositions 2 to 7 according to the invention comprise a
carbon black A for compositions 2 to 5, or a carbon black B for
compositions 6 and 7.
[0111] Carbon black A is sold under the name "CRX1416B" by CABOT,
and carbon black B is sold under the name "EX 3-3" by
COLUMBIAN.
[0112] Composition 5 differs from composition 4 in that it
furthermore comprises a processing aid sold by RHEIN CHEMIE under
the name "AFLUX 42", in order to reduce the viscosity of
composition 5 in the non-cross-linked state).
[0113] All these compositions are sulphur-cross-linkable.
1 TABLE 1 Comp. 1 Comp. 2 Comp. 3 Comp. 4 Comp. 5 Comp. 6 Comp. 7
NR 100 100 100 100 100 100 100 Black N347 52 Black A 52 55 58 58
Black B 55 58 ZnO 9 9 9 9 9 9 9 Stearic acid 0.65 0.65 0.65 0.65
0.65 0.65 0.65 Antioxidant 1.50 1.50 1.50 1.50 1.50 1.50 1.50
"AFLUX 42" 3 Cobalt salt* 0.20 0.20 0.20 0.20 0.20 0.20 0.20
Insoluble 7.6 7.6 7.6 7.6 7.6 7.6 7.6 sulphur Accelerator 0.93 0.93
0.93 0.93 0.93 0.93 0.93 *phr of cobalt metal
[0114] The natural rubber (NR) which is used is peptised and has a
Mooney viscosity ML (1+4) at 100.degree. C. equal to 60.
[0115] The antioxidant used is
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene- diamine.
[0116] The carbon blacks used are set forth in Table 2 below:
2 TABLE 2 N347 Black A Black B CTAB in m.sup.2/g 88 55 50 BET in
m.sup.2/g 88 53 50 IA in mg/g 90 62 56 BET/IA 0.98 0.85 0.89 DBP in
ml/100 g 124 134 130 DBPC in ml/100 g 100 94 88 dst in nm 77 131
133 D50 in nm 53 103 113 D50/dst 0.688 0.786 0.849
[0117] These compositions 1 to 7 are obtained by mixing all the
aforementioned constituents, except for the cobalt salt, the
sulphur and the accelerator, by thermomechanical working in an
internal mixer in one step which lasts approximately 4 minutes with
a speed of rotation of the blades of 50 rpm, until a dropping
temperature of approximately 170.degree. C. is reached, followed by
a finishing step effected at 80.degree. C., during which the cobalt
salt, the sulphur and the vulcanisation accelerator are
incorporated.
[0118] The cross-linking is effected at 150.degree. C. for a time
sufficient to achieve 99% of the maximum torque on a rheometer.
[0119] The properties in the cross-linked state and in the
non-cross-linked state of these compositions 1 to 7 were compared.
The results are set forth in Table 3 below.
3 TABLE 3 Comp. 1 Comp. 2 Comp. 3 Comp. 4 Comp. 5 Comp. 6 Comp. 7
ML(1 + 4) at 100.degree. C. 52 52 55 58 52 48 52 Shore 80 78 80 81
81 77 79 M10 in MPa 9.13 7.67 8.03 8.94 9.49 8.27 8.92 as base 100
100 84 88 98 104 89 96 HL in % 22.85 17.13 17.13 18.05 18.96 16.85
18.00 as base 100 100 75 75 79 83 74 79 G* max 60.degree. C. 8.24
5.76 6.43 8.82 8.04 as base 100 100 70 78 107 97 Tan delta max
60.degree. C. 0.163 0.130 0.132 0.142 0.139 as base 100 100 80 81
87 85 Break 100.degree. C. FR in MPa 16.0 14.7 14.1 15.1 14.1 14 14
AR in % 360 360 326 323 308 359 364 Tearability 100.degree. C. FRD
in N/mm 30 33 38 34 25 36 29 ARD in % 97 84 87 87 77 88 85
[0120] It would appear that the carbon blacks A or B impart to
compositions 4, 5 and 7 according to the invention hysteresis
properties at high deformation (HL at 60.degree. C.) which are
improved by 17% to 21% relative to those of the "control"
composition comprising the black N347, these compositions according
to the invention furthermore having a modulus of elongation at low
deformation (M10) which is close to that of said "control"
composition, which makes these compositions according to the
invention particularly well suited for use in the carcass
reinforcement of tires intended to bear heavy loads.
[0121] It will be noted that the other properties of these
compositions 4, 5 and 7 according to the invention are comparable
to those of said "control" composition.
[0122] It will also be noted that the incorporation in the
composition 5 of the processing aid imparts to this composition 5 a
viscosity in the non-cross-linked state and, consequently, a
processing ability which is similar to that of the "control"
composition, and practically without adversely affecting the
hysteresis properties of this composition 5.
2) Second Series of Examples
[0123] The object of the following examples is to compare two
rubber compositions each having in the cross-linked state a secant
tensile modulus M10 of approximately 6 MPa, which are both based on
natural rubber and which comprise respectively two different carbon
blacks as reinforcing filler, in a quantity of black of between 40
and 50 phr.
[0124] The first composition 8 is a "control" composition
representing the known prior art, and it comprises 45 phr of carbon
black designated "N326".
[0125] The second composition 9 is in accordance with the
invention, and it comprises 48 phr of said carbon black A
designated "CRX1416B".
[0126] Table 4 below lists the characteristics of these carbon
blacks N326 and A.
4 TABLE 4 N326 Black A CTAB in m.sup.2/g 83 55 BET in m.sup.2/g 84
53 IA in mg/g 82 62 BET/IA 1.02 0.85 DBP in ml/100 g 72 134 DBPC in
ml/100 g 69 94 dst in nm 72 131 D50 in nm 54 103 D50/dst 0.75
0.786
[0127] It will be noted that this black N326 is such that D50/Dst
does not meet the aforementioned condition (vii) according to the
invention, since 0.75 is less than 0.0090. CTAB+0.19=0.937.
[0128] The formulations of these compositions 8 and 9 are set forth
in Table 5 below.
5 TABLE 5 Comp. 8 Comp. 9 NR 100 100 Black N326 45 Black A 48 ZnO
7.50 7.50 Stearic acid 0.90 0.90 Antioxidant 1.50 1.50 Cobalt salt*
0.20 0.20 Insoluble sulphur 5.60 5.60 Accelerator 0.93 0.93 *phr of
cobalt metal
[0129] The natural rubber (NR) which is used is peptised and has a
Mooney viscosity ML (1+4) at 100.degree. C. equal to 60.
[0130] The antioxidant used is
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene- diamine.
[0131] These compositions 8 and 9 are obtained by mixing all the
aforementioned constituents, except for the cobalt salt, the
sulphur and the accelerator, by thermomechanical working in an
internal mixer in one stage, of a duration of about 4 minutes with
a speed of rotation of the blades of 50 rpm, until a dropping
temperature of approximately 170.degree. C. is obtained, followed
by a finishing step effected at 80.degree. C., during which are
incorporated the cobalt salt, the sulphur and the vulcanisation
accelerator.
[0132] The cross-linking is effected at 150.degree. C. for a time
sufficient to achieve 99% of the maximum torque on a rheometer.
[0133] The properties in the cross-linked state and in the
non-cross-linked state of these compositions 8 and 9 were compared.
The results are set forth in Table 6 below.
6 TABLE 6 Composition 8 Composition 9 ML(1 + 4) at 100.degree. C.
89 85.5 M10 in MPa 5.8 6.3 as base 100 100 109 HL in % 18.5 14.2 as
base 100 100 77 Break at 100.degree. C.: FR in MPa 17.5 15.0 AR in
% 530 425 Tearability at 100.degree. C.: FRD in N/mm 29.0 36.5 ARD
in % 130 180
[0134] It would appear that the carbon black A imparts to the
composition 9 according to the invention hysteresis properties at
high deformation (HL at 60.degree. C.) which are improved by 23%
(going from 18.5% to 14.2%) compared with those of the "control"
composition 8 comprising the black N326, this composition 9
furthermore having a modulus of elongation at low deformation (M10)
which is close to that of said composition 8, which makes said
composition 9 particularly well suited for use in the carcass
reinforcement of tires intended to bear heavy loads.
[0135] It will be noted that the other properties of this
composition 9 according to the invention are comparable to those of
said "control" composition 8.
3) Third Series of Examples
[0136] The object of the following examples is also to compare two
rubber compositions each having in the cross-linked state a secant
tensile modulus M10 of approximately 6 MPa, which are both based on
natural rubber and which comprise respectively two different carbon
blacks as reinforcing filler, in a quantity of black of between 40
and 50 phr.
[0137] The first composition 10 is a "control" composition
representing the known prior art, and it comprises 47 phr of carbon
black designated "N326".
[0138] The second composition 11 is in accordance with the
invention, and it comprises, on one hand, 47 phr of said carbon
black A of the name "CRX1416B" and, on the other hand, 1 phr of a
methylene donor and 2 phr of a methylene acceptor as reinforcing
organic filler.
[0139] The formulations of these compositions 10 and 11 are set
forth in Table 7 below.
7 TABLE 7 Composition 10 Composition 11 NR 100 100 Black N326 47
Black A 47 ZnO 7.5 9 Stearic acid 0.9 0.5 Antioxidant 1.5 1.8
Cobalt salt* 0.2 0.15 "Methylene acceptor" 2 "Methylene donor" 1
Insoluble sulphur 5.6 3.13 Accelerator 0.93 0.6 *phr of cobalt
metal
[0140] The natural rubber (NR) which is used is peptised and has a
Mooney viscosity ML (1+4) at 100.degree. C. equal to 60.
[0141] The antioxidant used is
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene- diamine.
[0142] The methylene acceptor is a "novolac" phenolic resin sold by
INSPEC under the name "Penacolite B20".
[0143] The methylene donor is hexamethylenetetramine.
[0144] These compositions 10 and 11 are obtained by mixing all the
aforementioned constituents, except for the cobalt salt, the
sulphur, the accelerator and the methylene donor, by
thermomechanical working in an internal mixer in one stage, of a
duration of about 4 minutes with a speed of rotation of the blades
of 50 rpm, until a dropping temperature of approximately
170.degree. C. is obtained, followed by a finishing step effected
at 80.degree. C., during which are incorporated the cobalt salt,
the sulphur, the vulcanisation accelerator and the methylene
donor.
[0145] The cross-linking is effected at 140.degree. C. for a time
sufficient to achieve 99% of the maximum torque on a rheometer.
[0146] The properties in the cross-linked state and in the
non-cross-linked state of these compositions 10 and 11 were
compared. The results are set forth in Table 8 below.
8 TABLE 8 Composition 10 Composition 11 ML(1 + 4) at 100.degree. C.
78 94 M10 in MPa 5.9 5.8 as base 100 100 98 HL in % 18.1 14.6 as
base 100 100 81 Break at 100.degree. C.: FR in MPa 16.7 15.8 AR in
% 490 500 Tearability at 100.degree. C.: FRD in N/mm 24.9 35.1 ARD
in % 155 153
[0147] It would appear that the carbon black A imparts to the
composition 11 according to the invention hysteresis properties at
high deformation (HL at 60.degree. C.) which are improved by 19%
(going from 18.1% to 14.6%) compared with those of the "control"
composition 10 comprising the black N326, this composition 11
furthermore having a modulus of elongation at low deformation (M10)
which is close to that of the composition 10, without impairing the
cohesion properties (break and tearability), which makes this
composition 11 according to the invention particularly well suited
for use in the carcass reinforcement of tires intended to bear
heavy loads.
* * * * *