Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-04-13
2003-05-13
Dawson, Robert (Department: 1712)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S306300, C528S015000, C528S017000, C528S031000, C528S032000, C528S034000
Reexamination Certificate
active
06562180
ABSTRACT:
The general field of the invention is that of silicone elastomer compositions which are crosslinkable by addition and/or condensation. The polyorganosiloxanes (POS) considered are of the room-temperature vulcanizable (RTV) type, given that they are conventionally in the form of a two-component system (RTV-2) whose vulcanization can be accelerated under warm conditions.
The context of the invention relates more especially to self-adhesive silicone compositions which crosslink by an addition reaction, whose kinetics can be significantly increased by raising the temperature.
Even more specifically, the present invention is directed towards adhesive silicone compositions which can be crosslinked by addition and which also use coupling reactions to develop the adhesion.
The invention also relates to the use of such a silicone composition as an adhesive.
The crosslinking and incidental curing of these silicone compositions, applied at the interface between two solids, participate in the adhesion mechanism which makes it possible to bind the two solids to each other. Crosslinking by addition involves unsaturated groups, in particular alkenyls and even more particularly vinyls (Vi), linked to the silicon in the POS (Si-Vi units) as well as hydrogens linked to the silicon of the same or of another POS (SiH units). These reactions can be likened to hydrosilylations of the Si-Vi units by Si-H units.
The coupling required for the adhesion involves alkoxy groups OR, linked to the silicon atoms of silanes and/or of other alkoxide groups (POS resins) in the composition.
The crosslinkings by addition can advantageously be catalysed by metal compounds which are, respectively, of platinum type.
Silicone elastomer compositions which can be used for coating various woven or nonwoven fibrous supports are already known for applications other than those of bonding. After crosslinking, the film coated on the support forms a protective and mechanically reinforcing coat. Such fibrous supports thus coated with a crosslinked silicone elastomer film can be used for the manufacture of inflatable bags for the personal protection of the occupants of vehicles (airbags). An example of such silicone elastomer compositions is given in European patent application No. 0,681,014 in the name of the Applicant, and concerning a silicone elastomer coating composition of the room-temperature vulcanizable type, consisting of a mixture formed of:
(I) at least one polyorganosiloxane containing, per molecule, at least two C
2
-C
6
alkenyl groups linked to the silicon,
(II) at least one polyorganosiloxane containing, per molecule, at least three hydrogen atoms linked to the silicon,
(III) a catalytically effective amount of at least one catalyst, composed of at least one metal belonging to the platinum group,
(IV) an adhesion promoter,
(V) optionally, an inorganic filler,
(VI) optionally, at least one crosslinking inhibitor, and
(VII) optionally, at least one unsaturated polyorganosiloxane resin, characterized in that the adhesion promoter exclusively contains:
(IV.1) at least one alkoxylated organosilane containing, per molecule, at least one C
2
-C
6
alkenyl group,
(IV.2) at least one organosilicon compound comprising at least one epoxy radical,
(IV.3) at least one chelate of a metal M and/or a metal alkoxide of general formula: M(OJ)
n
, where n=valency of M and J=linear or branched C
1
-C
8
alkyl,
M being chosen from the group formed by: Ti, Zr, Ge, Li, Mn, Fe, Al, Mg.
More specifically, this coating composition can comprise:
(I)—Si-Vi POS of the &agr;,&ohgr;-(CH
3
)
2
ViSiO
0.5
polydimethylsiloxane type of viscosity=100,000 mPa·s at 25° C.;
(II)—SiH POS of the polydimethyl-methylhydrogeno-&agr;, &ohgr;-(CH
3
)
2
HSiO
0.5
type;
(III)—Platinum catalyst
(IV)—Promoter:
(IV.1) =vinyltrimethoxysilane (VTMO)
(IV.2) =3-glycidoxypropyltrimethoxysilane (GLYMO),
(IV.3) =butyl orthotitanate (TBOT);
(V)—Filler=ground silica or reinforced silica
(VI)—Optional inhibitor=ethynylcyclohexanol (ECH)
(VII)—Optional POS resin bearing unsaturation(s), of following formula, expressed as siloxy units: MM
vi
DD
vi
Q in which
M=(CH
3
)
3
SiO
0.5
M
vi
=(CH
3
)
2
ViSiO
0.5
D=(CH
3
)
2
SiO
D
vi
=CH
3
ViSiO
Q=SiO
2
.
The silicone coating obtained after crosslinking the coating film based on this composition has good hardness, mechanical strength, surface uniformity and heat-resistance properties. The promoter IV according to the invention claimed in that European patent application affords improved adhesion of the coating to the fabric. This is reflected in a wrinkle test, standard FFG 37 110, of a coated fabric, by a threshold ranging from 350 to 600 cycles for the samples tested in the examples.
Since the primary purpose of the compositions according to that patent application EP 0,681,014 is not to bond two components to each other, it is clear that its adhesion power is not optimized. In any case, this coating composition could not constitute a bonding agent.
Another illustration of the prior art which may be mentioned is European patent application EP 0,326,712, which discloses a crosslinkable POS composition comprising:
an &agr;,&ohgr;-(CH
3
)
2
ViSiO
0.5
polydimethylsiloxane with a degree of polymerization DP of 300;
an SiH POS of the &agr;,&ohgr;-(CH
3
)
3
SiO
0.5
polydimethylmethylhydrogenosiloxane type;
a platinum catalyst;
a crosslinking inhibitor such as 3-methyl-1-butyn-3-ol, and
an adhesion promoter comprising glymo, and a diallyl ether of trimethylolpropane, of ethylene glycol or of glycerol.
According to that patent application
EP 0,326,712, a silicone composition can be used as an adhesive. However, the performance obtained in this respect remains modest, as evidenced by the adhesion tests carried out according to a test JIS K 6301. The maximum adhesion values obtained are about 30 kilos per cm
2
and vary depending on the substrate.
In the face of such prior art which does not propose an adhesive based on a silicone composition which is crosslinkable by addition/coupling and which has all the specifications expected for bonding agents, i.e.:
stability on storage,
viscosity of the liquid form of the composition satisfying the requirements for ease of application to the substrates to be adhesively bonded,
high adhesive power,
heat resistance,
stability of the adhesive bond over time,
low cost price.
The Applicant set itself the essential aim of overcoming this deficiency.
It thus sought to develop a silicone-based adhesive liquid composition which is crosslinkable by SiH/SiVi addition and which satisfies the abovementioned specifications. Another essential aim of the present invention is to recommend the use of a silicone composition, which is crosslinkable by addition, as an adhesive for adhesively bonding various substrates, for example metals or plastics.
Another essential aim of the present invention is to provide a crosslinkable silicone composition or a use of this composition for the adhesive bonding of electrical/electronic components or mechanical components, in particular in the field of motor vehicles or the field of household appliances (connection).
Another essential aim of the present invention is to provide a process for adhesively bonding at least two substrates using a crosslinkable silicone composition, the said process readily and economically giving a solid and long-lasting assembly between the two substrates.
In order to achieve these aims, the inventors have, to their merit, demonstrated, entirely surprisingly and unexpectedly and after long and laborious research, an astute and advantageous selection of a subgroup of crosslinkable silicone elastomer compositions, from among the large group of compositions disclosed in EP 681,014. This subgroup has the particular feature of being singularly adhesive and of moreover having all of the characteristics, and in particular the Theological and mechanical characteristics, for forming an excellent adhesive.
Thus, the present invention satisfies the abovementioned aims, i
Bohin Fabrice
Joubert Gérard
Lorenzetti Dominique
Loubet Olivier
Pouchelon Alain
Burns Doane Swecker & Mathis L.L.P.
Dawson Robert
Rhodia Chimie
Robertson Jeffrey B.
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