Note: Descriptions are shown in the official language in which they were submitted.
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SULPHUR-CONTAINING AROMATIC POLYOL COMPOUND
1. FIELD OF THE INVENTION
The present invention relates to monomers capable of being used for the
synthesis of
polymers having urethane units (or polyurethanes), especially intended for
adhesive systems
for the adhesive bonding of glass or metal to rubber.
It more particularly relates to the above monomers of the sulphur-containing
polyol type
especially intended for the synthesis of polyurethanes used in composites of
the metal/rubber
type for articles made of rubber, such as tyres.
2. PRIOR ART
Composites of the metal/rubber type, in particular for tyres, are well known.
They are
generally composed of a matrix made of unsaturated rubber, generally diene
rubber, which
can be crosslinked with sulphur, comprising metal reinforcing elements (or
"reinforcers")
such as wires, films or cords made of carbon steel.
As they are subjected to very high stresses during the rolling of the tyres,
especially to
repeated actions of compression, bending or variation in curvature, these
composites must, in
a known way, satisfy a large number of sometimes contradictory technical
criteria, such as
uniformity, flexibility, flexural strength and compressive strength, tensile
strength, wear
resistance and corrosion resistance, and must maintain this performance at a
very high level
for as long as possible.
It is easily understood that the adhesive interphase between rubber and
reinforcers plays a
predominant role in the endurance of this performance. The conventional
process for
connecting the rubber compositions to carbon steel consists in coating the
surface of the steel
with brass (copper/zinc alloy), the bonding between the steel and the rubber
matrix being
provided by sulphurization of the brass during the vulcanization or curing of
the rubber. In
order to improve the adhesion, use is generally made, in addition, in these
rubber
compositions, of organic salts or metal complexes, such as cobalt salts, as
adhesion-
promoting additives.
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In point of fact, it is known that the adhesion between the carbon steel and
the rubber
matrix is capable of weakening over time as a result of the gradual
development of
sulphides formed under the effect of the various stresses encountered,
especially
mechanical and/or thermal stresses, it being possible for the above
decomposition process
to be accelerated in the presence of moisture.
Moreover, the use of cobalt salts renders the rubber compositions more
sensitive to
oxidation and to ageing, and significantly increases the cost thereof, not to
mention that it is
desirable to eliminate, in the long run, the use of such cobalt salts in
rubber compositions
due to recent developments in European regulations relating to metal salts of
this type.
For all the reasons set out above, manufacturers of metal/rubber composites,
in particular
tyre manufacturers, are seeking novel adhesive solutions in order to
adhesively bond metal
reinforcers to rubber compositions, while overcoming, at least in part, the
abovementioned
disadvantages.
3. BRIEF DESCRIPTION OF THE INVENTION
In point of fact, during their research studies, the Applicants have found a
novel polyol
compound of sulphur-containing aromatic type which enables the synthesis of a
polyurethane which meets such an objective.
According to the invention, said sulphur-containing aromatic polyol compound
corresponds
to the formula (I) below:
HO ¨ CH2 ¨ (Zi)a ¨ CH(OH) ¨ CH2 ¨ S ¨ Z3 ¨ S ¨ CH2 ¨ CH(OH) ¨ (Z2)b ¨ CH2 ¨ OH
in which:
- Z1 and Z2, which are identical or different, represent an optional, at
least divalent,
bonding group comprising at least one carbon atom;
- a and b, which are identical or different, are equal to 0 or 1;
- Z3 represents an at least divalent aromatic bonding group comprising at
least 6
carbon atoms, each sulphur atom on either side of the Z3 group being directly
bonded to an aromatic ring of Z3.
Date Recue/Date Received 2021-01-13
2a
Another embodiment of the invention relates to a polymer having urethane units
which
results of a polycondensation of at least one sulfur-containing aromatic
polyol compound
with a polyisocyanate,
wherein said polyol compound corresponds to the formula:
(I)
HO ¨ CH2 ¨ (Zi)a ¨ CH(OH) ¨ CH2 ¨ S ¨ Z3 ¨ S ¨ CH2 ¨ CH(OH) ¨ (Z2)b ¨ CH2 ¨ OH
in which:
- Z1 and Z2, which are identical or different, represent an optional, at
least divalent,
bonding group comprising at least one carbon atom;
- a and b, which are identical or different, are equal to 0 or 1; and
- Z3 represents an at least divalent aromatic bonding group comprising at
least 6
carbon atoms, each sulphur atom on either side of the Z3 group being directly
bonded to an aromatic ring of Z3; and
wherein said polymer comprises at least units of formula:
(II)
¨0¨ CH2 ¨ (Zi)a ¨ CH(OH) ¨ CH2 ¨ S ¨ Z3 ¨ S ¨ CH2 ¨ (OH) ¨ (Z2)b ¨ CH2 ¨
with Z1, Z2, Z3, a and b as defined above.
Another embodiment of the invention relates to a process for the synthesis of
a polymer
having urethane units, wherein said process comprises a step of
polycondensation of at
least one sulphur-containing aromatic polyol compound as defined hereinabove,
with a
polyisocyanate compound.
Another embodiment of the invention relates to a use of a sulphur-containing
aromatic
polyol compound as defined hereinabove in the manufacture of a polymer having
urethane
units.
By virtue of this very specific sulphur-containing aromatic polyol (primary
diol) compound
comprising in particular, in addition to its two primary alcohol functional
groups, on the one
hand, at least two secondary alcohol functional groups and, on the other hand,
a thioether
Date Recue/Date Received 2021-01-13
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(-S-) functional group in the alpha position with regard to each of these two
secondary
alcohol functional groups, it has proved to be possible to prepare a
polyurethane which, used
as adhesion primer on metal reinforcers, gives these reinforcers the major and
unexpected
advantage of being able to adhere to unsaturated rubber matrices by using
simple textile
adhesives, such as "RFL" (resorcinol/formaldehyde latex) adhesives, or other
equivalent
adhesive compositions, or else directly (that is to say, without use of such
adhesives) to these
unsaturated rubber matrices when the latter comprise, for example, appropriate
functionalized
unsaturated elastomers, such as, for example, epoxidized elastomers.
The invention also relates to the use of a polyol compound in accordance with
the invention
in the manufacture of a polyurethane and also to any polyurethane resulting
from at least one
polyol compound in accordance with the invention.
The invention also relates to any process for the synthesis of a polyurethane
by
polycondensation of at least one polyol compound in accordance with the
invention with a
polyisocyanate compound.
The invention and its advantages will be easily understood in the light of the
detailed
description and exemplary embodiments which follow, and also of Figures 1 to 3
relating to
these examples, which represent or diagrammatically represent:
- two examples of sulphur-containing polyol compounds in accordance with the
invention (denoted Monomers MI and M2), and also a synthesis scheme which can
be used to produce each of these compounds (Fig. 1 and Fig. 2);
95 - a detailed synthesis scheme which can be used, starting from Monomer
MI
according to the invention and a diisocyanate monomer (Monomer A2;
benzophenone-blocked MDT), for a polyurethane polymer P1 according to the
invention (Fig. 3).
4. DETAILED DESCRIPTION OF THE INVENTION
It will be recalled first of all here that a polyurethane is a polymer (by
definition any
homopolymer or copolymer, especially block copolymer) comprising a plurality
of urethane
( 0 CO NH¨) bonds resulting, in a known way, from the addition reaction of a
polyol
having at least two primary alcohol functional groups with a polyisocyanate
(compound
bearing at least two isocyanate ¨NCO functional groups), especially with a
diisocyanate in
the case of a polyurethane of the linear type.
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The sulphur-containing aromatic polyol (primary diol) compound of the
invention, which can
be used especially for the synthesis of a polyurethane, thus corresponds to
the formula (I):
HO ¨ CH2 ¨ (Z ¨ CH(OH) ¨ CH2 ¨ S ¨ Z3 ¨ S CH2 ¨ CH(OH) ¨ (Z2)b ¨ CH2 ¨ OH
in which:
- Z1 and
Z2, which are identical or different, represent an optional, at least
divalent,
bonding group comprising at least 1 carbon atom;
- a and b, which are identical or different, are equal to 0 or 1 (that is to
say that Zi
and Z2 may be present or absent);
- Z3 represents an at least divalent aromatic bonding group comprising at
least 6
carbon atoms, each sulphur atom on either side of the Z3 group being directly
bonded to an aromatic ring of Z3.
This sulphur-containing aromatic polyol compound thus especially has the
essential
characteristic of comprising, on either side of the central aromatic ¨ Z3 ¨
group, a secondary
alcohol (¨ CH(OH) ¨) functional group and a thioether (¨ S ¨) functional group
in the a
position (alpha position, that is to say, as a reminder and by convention,
borne by a carbon
adjacent to the carbon bearing the secondary alcohol functional group) with
respect to this
secondary alcohol functional group. In other words, this polyol compound
comprises an a-
hydroxy-thioether unit on either side of the Z3 group.
Zi, Z2 and Z3 are bonding groups, spacing units, of organic type, preferably
hydrocarbon,
also commonly known as "separators" or "spacers" by those skilled in the art;
they can be
saturated or unsaturated.
According to a particular embodiment, Z1 and Z2, which are identical or
different and
substituted or unsubstituted, represent an aliphatic bonding group having from
1 to 20 atoms,
more preferentially from 1 to 12 carbon atoms. or a cycloaliphatic bonding
group having
from 3 to 20 carbon atoms, more preferentially from 3 to 12 carbon atoms; more
particularly,
this is a C1-Co, especially C1-05, alkylene.
According to another preferential embodiment, Z3 comprises from 6 to 30, more
preferentially from 6 to 20, carbon atoms. By definition, each sulphur atom on
either side of
Z3 is directly bonded to an aromatic ring, it being understood that the latter
may be the same
ring or a different ring for these two sulphur atoms. More preferentially
still, Z3 comprises at
least one (in particular one or two) phenylene group, the latter possibly
being substituted or
unsubstituted.
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According to another preferential embodiment, at least one of the Z1, Z2 and
Z3 groups
comprises at least one (that is to say, 1 or more) heteroatom preferably
chosen from 0, S or
N.
According to another preferential embodiment, at least one of the Zi, Z2 and
Z3 groups
comprises at least one (that is to say, 1 or more) ether (¨ 0 ¨) bond or
thioether (¨ S ¨) bond,
it being possible for this to be present on the carbon-containing chain (ZI,
Z2 or Z3) itself or
on a substituent of one of its carbon atoms.
According to a preferential embodiment, a and b are equal to zero; in other
words, in such a
case, the sulphur-containing primary diol compound of the invention
corresponds to the
formula (I'):
(I')
HO ¨ CH2¨ CH(OH) ¨ CH, ¨ S ¨ Z3 ¨ S ¨ CH2 ¨ CH(OH) ¨ CH, ¨ OH
The formulae below (with "n" an integer ranging for example from 1 to 30,
especially from 1
to 20, more particularly from 1 to 10) illustrate, by way of examples, various
groups
corresponding to the definition of the above sequence ¨ S ¨ Z3 ¨ S
¨S 41 S-
¨S S-
-S 0 S ¨
¨S S 4111 S-
-S CH2 n S-
¨S C F2 n S-
¨S S¨
OH,
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CF,
¨S S-
CF,
S-
-S
1410
N
The formulae of two examples of sulphur-containing aromatic polyol compounds
in
accordance with the invention, denoted Monomers M1 and M2, and also a
synthesis scheme
which can be used for the production of each of these compounds, have been
represented in
expanded form in the appended Figures 1 and 2.
The polyol compound (Monomer Ml, subsequently also denoted Monomer Al) of
Figure 1
is 3-{444-(2,3-
dihydroxypropylsulphanyl)phenylsulphanyl]phenylsulphanyl}propane-1,2-
diol. It can be obtained, for example, by reaction of 4,4'-thiobisbenzenethiol
and liquid 3-
chloro-1,2-propanediol, as represented diagrammatically in Figure 1. Its
synthesis will be
described in more detail in the exemplary embodiments which follow (Test 1 of
section 5.1).
The polyol compound (Monomer M2) of Figure 2 is 3-(4-{4-[4-(2,3-
dihydroxypropylsulphanyl)pheny1]-6-pheny1-1,3,5-triazin-2-y1
phenylsulphanyl)propane-
1,2-diol.
It can be obtained, for example, according to the process represented
diagrammatically in
Figure 2.
5.70 g (i.e., 16.5 mmol) of 2,4-bis(p-fluoropheny1)+1,3,5-1-s-triazine, 200 ml
of anhydrous
DMSO solvent and then dry potassium carbonate (6.03 g, i.e. 43.6 mmol) are
introduced,
under a nitrogen stream, into a 4-necked 500 ml round-bottomed flask (equipped
with a
reflux condenser, a magnetic bar and a nitrogen inlet, dried beforehand under
vacuum at a
temperature of greater than 100 C); the triazine compound and the potassium
carbonate were
both dried beforehand under vacuum at 150 C overnight. The starting triazine
compound was
synthesized in a known way, as taught in Application WO 2012/016777 (Test V- I-
A,
Compound I. Fig. 18). The system is subsequently purged for 30 min with
stirring and under
a nitrogen stream. 4.29 g (i.e., 39.6 mmol) of 1-thioglycerol are then
introduced and then the
suspension is heated at 100 C for 4.5 h under a stream of nitrogen and with
stirring. The
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reaction mixture is subsequently cooled to room temperature (23 C) and the
potassium
carbonate is removed by filtration through filter paper; the salt is washed
with an additional
50 ml of DMSO. The filtrate is subsequently poured into 250 ml of ice-cold
water and thus
precipitated. 100 ml of (10%) HC1 solution and 1 litre of &mineralized water
are then added;
the pH is adjusted to 1.0 using the (10%) HC1 solution. The white precipitate
(Monomer M2)
thus obtained (8.6 g, yield of approximately 100%) is isolated by filtration
through filter
paper, washed with demineralized water and dried at 90 C under vacuum
overnight.
The common characteristic of the two sulphur-containing aromatic polyol
compounds
described above in Figures 1 and 2, is that they all indeed correspond to the
formula (I'):
HO ¨ CH2 ¨ CH(OH) ¨ CH2 ¨ S ¨ Z3 ¨ S ¨ CH2 ¨ CH(OH) ¨ CH2 ¨ OH
in which, for these examples:
- a and b are equal to 0; in other words, Zi and Z2 are absent;
- Z3 represents a divalent aromatic bonding group comprising at least 6
carbon atoms
and also at least one heteroatom (S or N), each sulphur atom on either side of
the Z3
group being directly bonded to an aromatic ring (phenylene group).
The sulphur-containing aromatic polyol compound in accordance with the
invention
described above can preferentially be used in the synthesis of a polyurethane
of the linear
type, thus resulting essentially from the addition of this polyol (primary
diol) and of a
diisocyanate compound. The diisocyanate which can be used can be aromatic,
aliphatic or
cycloaliphatic; it can be a monomer, a prepolymer or a quasi-prepolymer,
indeed even a
polymer.
According to a preferential embodiment, the diisocyanate from which the
polymer of the
invention results is selected from the group consisting of the following
aromatic compounds:
diphenylmethane diisocyanate (abbreviated to "MDI"), toluene diisocyanate
("TDI"),
naphthalene diisocyanate (''NDI"), 3,3'-bitoluene diisocyanate ("TODI"), para-
phenylene
diisocyanate ("PPDI"), their various isomers and the mixtures of these
compounds and/or
isomers.
More preferentially, use is made of an MDI or a TDI, more preferentially still
of an MDI.
All the isomers of MDI (especially 2,2'-MDI, 2,4"-MDI and 4,4'-MDI) and their
mixtures
can be used, as well as what are referred to as polymeric MDIs (or "PMDIs")
comprising
oligomers of the following formula (with p equal to or greater than 1):
OCN ___________________________________________ I NCO
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Diisocyanate compounds of the aliphatic type can also be used, such as, for
example, 1,4-
tetramethylene di isocyanate, 1,6-hexane di isocyanate
("IIDI"), 1,4-
b is(isocyanatomethyl)cyclohexane, 1,3 -b is(isocyanatomethyl)cyclohexane,
1,3-
bis(isocyanatomethyl)benzene, 1,4-bis(isocyanatomethyl)benzene, isophorone
diisocyanate
(" I PDI" ), b is(4-
isocyanatocyclohexyl)methane diisocyanate 1 2MDI") or 4,4'-
dicyclohexylmethane diisocyanate ("HI 3MDI").
According to a particularly preferential embodiment, the diisocyanate used is
4,4-MD! (4,4'-
diphenylmethane diisocyanate), having the formula:
O=C=N NCO
or, if several diisocyanates are used, constitutes the predominant
diisocyanate by weight,
preferably representing, in the latter case, more than 50% of the total weight
of the
di isocyanate compounds.
Use may also advantageously be made of a caprolactam-blocked 4,4'-MDI (for
example the
product in the solid form "Grilbond" IL-6 from EMS), of formula:
0
0
N Nr¨N
CL1 N
H
0 0
As the invention is not, however, limited to a polymer of the linear type (as
a reminder,
derived from a diisocyanate), it will also be possible to use, especially with
the aim of
increasing the Tg of the polymer of the invention by formation of a three-
dimensional
network, a triisocyanate compound, such as, for example, an MDI trimer having
a triazine
ring of the formula below:
I 1
OCN NCO
N
OCN
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The polyurethane resulting from the polyol compound of the invention thus has
the
characteristic of comprising, in addition to its base structural units
comprising urethane (-0¨
CO¨NH¨) units contributed in a well-known way by the starting polyisocyanate
compound,
specific repeat additional units contributed by the polyol monomer according
to the
invention, these additional units comprising at least one unit of formula
(II):
(II)
¨0¨ CH2 ¨ (ZI)a ¨ CH(OH) ¨ CH2 ¨ S ¨ Z3 - S - CH2 - CH(OH) ¨ (Z2)b ¨ CH2 ¨
in which Z1, Z2, Z3, a and b of course have the main and preferential
definitions given above.
Formula (III) below reproduces an example of a sequence (repeat structural
unit) of polymers
of polyurethane type, this sequence comprising both a base unit (urethane)
contributed by a
diisocyanate (here, of formula OCN¨Z¨NCO) and also an additional unit
contributed by a
polyol compound according to the invention, namely:
(III)
¨0¨C(0)¨NH¨Z¨NH¨C(0)-0¨CH2¨(Zi)a¨CH(OH)CI 12¨S¨Zr-S¨C112¨CH(OH)¨(Z2)b¨CH2¨
In Formula (III) above, Z represents a saturated or unsaturated at least
divalent bonding
group; it is preferably an aliphatic, cycloaliphatic or aromatic group, the
aliphatic group
preferably comprising from I to 30 (more preferentially from I to 20) carbon
atoms, the
cycloaliphatic group preferably comprising from 3 to 30 (more preferentially
from 3 to 20)
carbon atoms and the substituted or unsubstituted aromatic group preferably
comprising from
6 to 30 (more preferentially from 6 to 20) carbon atoms.
Figure 3 illustrates a possible synthesis process, starting from the polyol
monomer in
.. accordance with the invention (Monomer Ml, also denoted Al) and from
another monomer
(Monomer A2), of a polymer in accordance with the invention of polyurethane
type (Polymer
PI), which process will be described in detail below.
This example of Polymer PI prepared according to the invention does indeed
comprise a
repeat unit of Formula (III) in which Z corresponds more particularly to the
MDI residue
divalent group, a and b are equal to 0 and Z3 represents an aromatic group
especially bearing
a thioether (-S-) bond.
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It is clearly seen in Figure 3 that, in accordance with the invention, Polymer
P1 comprises, in
addition to its urethane base units, additional units which comprise two cf.-
hydroxy-thioether
(- CH(OH) ¨ CH2 ¨ S ¨) functional groups on either side of Z3.
The polyurethane which can be synthesized from a sulphur-containing aromatic
polyol
compound in accordance with the invention can comprise from ten to several
hundred,
preferentially from 20 to 200, repeat structural units as described above. Its
glass transition
temperature Tg, measured by DSC (Differential Scanning Calorimetry), for
example
according to Standard ASTM D3418, is preferably greater than 50 C, more
preferentially
greater than 100 C, in particular between 130 C and 250 C.
This polyurethane exhibits a high flexibility and a high elongation at break
and has
furthermore displayed effective hydrophobic properties and corrosion-
resistance properties.
It can advantageously be used as hydrophobic coating on any type of substrate,
especially
made of metal or glass, or else as adhesion primer on any type of metal
reinforcer, such as,
for example, a thread, a film, a plate or a cord made of carbon steel coated
or not coated with
brass, intended in particular to reinforce an unsaturated rubber matrix, such
as natural rubber.
5. EXEMPLARY EMBODIMENTS OF THE INVENTION
In the present application, unless expressly indicated otherwise, all the
percentages (%)
shown are percentages by weight.
5.1. Test 1 - Synthesis of the Monomer Al
Monomer Al (or MI) is 3-{444-(2,3-dihydroxypropylsulphanyl) phenylsulphanyll-
phenylsulphanyllpropane-1,2-diol, in accordance with the invention. This
monomer was
synthesized according to the procedure represented diagrammatically in Figure
3, as
described in detail below.
8.3 g of (Compound 1) solid 4,4'-thiobisbenzenethiol (i.e., 33.03 mmol) and
then 10.0 g of
potassium carbonate (i.e., 72.56 mmol, dried beforehand under vacuum at 150 C
for 12 h)
are introduced under an inert atmosphere (stream of nitrogen) into a 500 ml 4-
necked round-
bottomed flask dried beforehand under vacuum at more than 100 C and equipped
with a
condenser, thermometer and magnetic stirrer bar. 200 ml of anhydrous DMSO are
then
added, the dispersion is purged under nitrogen for 30 min, then 7.29 g of
(Compound 2)
liquid 3-chloro-1,2-propanediol (66.06 mmol) are added dropwise. The reaction
mixture is
immediately heated at 100 C for 5 h, still under a stream of nitrogen. The
solution obtained is
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subsequently allowed to cool to room temperature and the solid potassium
carbonate (K2CO3)
is recovered by filtration through a filter paper. The filtrate is
subsequently washed with 50
ml of DMSO and then everything is poured into 250 ml of deionized water at 0 C
(ice) in
order to precipitate the targeted product.
In order to neutralize the residual K2CO3, 10 ml of (10%) HC1 and 1 litre of
deionized water
are subsequently added. After drying under vacuum at 60 C overnight (12 h),
the precipitate
obtained (tacky orange-coloured solid) is poured into 500 ml of ethyl acetate
and the
combined mixture is heated to 40 C until complete dissolution is obtained. The
solution
obtained is cooled to room temperature (20 C) then decanted into a separating
funnel; 50 ml
of saturated (aqueous) NH4C1 are subsequently added. After stirring, the
organic phase is
separated then washed twice with 25 ml of deionized water, then dried with dry
sodium
carbonate. After filtration and distillation of the ethyl acetate on a rotary
evaporator
("Rotavap"), the solid obtained is dried at 80 C.
NMR and ESI analyses indeed confirm the structure of Monomer Al, of formula:
s
Ho
OH
OH
The 1H NMR analysis (500 MHz, d6-DMS0) of the product gave the following
results:
2.89 (m, 2H), 3.11 (m, 2H), 3.40 (m, 4H), 3.61 (m, 2H), 4.67 (d, 2H), 4.99 (d,
2H), 722-7.24 (d, 4H),
7.31-7.33 (d, 4H).
With regard to the molecular weight, measured by ESI mass spectrometry in an
ethyl
acetate/methanol (1/1) mixture (with traces of aqueous NaCl), it was evaluated
in negative
mode ([M + Cl]- anion) at 433.3 (calculated theoretical value equal to 434.0)
and in positive
mode ([M + Na] cation) at 421.1 (calculated theoretical value equal to 420.6).
5.2. Test 2: synthesis of Polymer P1 by reacting Monomers Al and A2
This test gives a detailed description of the synthesis of Polymer P1 in
accordance with the
invention, starting from Monomers Al and A2 (caprolactam-blocked MDI),
according to the
procedure represented diagrammatically in Figure 3.
280.0 mg of Monomer Al, 334.6 mg of Monomer A2 ("Grilbond" IL-6) and 8 ml of
NMP
solvent are placed in a glass flask. The suspension is heated (under a stream
of hot air) at
120 C, until a clear solution is obtained. 3 ml of the solution thus obtained
are then deposited
on a polished brass sheet (10 x 10 cm2) which is subsequently placed in an
oven at 190 C for
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15 min. A transparent film of Polymer PI is thus obtained, the DSC analysis of
which
(second pass, from -80 C to 200 C; 10 C/min) revealed a Tg of approximately
115 C. It may
be noted that a similar polymerization reaction, but carried out in a 1-
methoxypropano1-2-
acetate/sulpholane (3:1) solvent mixture, led to a Tg of approximately 130 C.
5.3. Test 3 - Test of adhesion of Polymer 1 in a metal/rubber composite
A thin film of Polymer P1 thus obtained was deposited (at room temperature)
uniformly at
the surface of a brass sheet. Everything was then covered with a layer of
conventional textile
adhesive of the "RFL" (resorcinol/formaldehyde latex) type. After a predrying
at 100 C for
5 min, the assembly was subsequently treated in an oven at 190 C for 10 min.
The brass sheet thus coated with the film of Polymer PI and over which RFL has
been spread
was subsequently placed in a matrix of conventional rubber composition (in the
uncured
state, non-vulcanized) for a belt reinforcement of a passenger vehicle tyre,
based on natural
rubber, on carbon black and silica as filler and on a vulcanization system
(sulphur and
sulphenamide accelerator), this composition being devoid of cobalt salt.
The metal/rubber composite test specimen thus prepared was then placed under a
press and
everything was cured (vulcanized) at 165 C for 30 min under a pressure of 20
bar. After
vulcanization of the rubber, excellent adhesive bonding between the rubber
matrix and the
metal sheet was obtained, despite the absence of cobalt salt in the rubber
matrix: this is
because, during peel tests carried out both at room temperature (23 C) and at
high
temperature (100 C), it was found that the failure occurred systematically in
the rubber
matrix itself and not at the interphase between metal and rubber.
In conclusion, the sulphur-containing aromatic polyol compounds of the
invention make it
possible to synthesize polyurethanes which are characterized by a high glass
transition
temperature, a high thermal and chemical stability and excellent adhesion to
glass or metal.
By virtue of the invention, these polyurethanes, used as adhesion primer on
metal in
metal/rubber composites, make it possible very advantageously to subsequently
adhesively
bond the metal to the rubber matrices using, for example, simple textile
adhesives, such as
"RFL" (resorcinol/formaldehyde latex) adhesives or other equivalent adhesive
compositions,
or else directly (that is to say, without use of such adhesives) to these
rubber matrices when
the latter comprise, for example, appropriate functionalized unsaturated
elastomers, such as
epoxidized elastomers.
Thus, cobalt salts (or other metal salts) can especially be dispensed with in
the rubber
compositions intended to be attached to brass-coated metal reinforcers.
P10-3422
