Use of a mixture of organic peroxides for crosslinking a polyolefin
elastomer
5 The present invention concerns the use of a mixture of organic
peroxides, as defined hereinbelow, for crosslinking polyolefin
elastomer (POE), preferably a copolymer of ethylene and at least one
alpha-olefin, especially intended to be used in photovoltaic
applications.
10 The invention also pertains to a crosslinkable composition
comprising at least one polyolefin elastomer (POE), preferably a
copolymer of ethylene and at least one alpha -olefin, and at least one
mixture of organic peroxides as defined hereinbelow.
The present invention also relates to a method for producing a
15 material based on polyolefin elast omer (POE), preferably an
encapsulating material, particularly for photovoltaic cells, which
comprises a step of crosslinking a crosslinkable composition as defined
above.
The invention is likewise directed to the material based on
20 polyolefin elastomer, pr eferably

CLAIMS
1. The use, for crosslinking a polyolefin elastomer, of a
composition comprising:
- at least one monoperoxycarbonate conforming to the
5 formula (I):
(I)
in which formula (I) R1 represents an alkyl radical
comprising a number of carbon atoms of less than or equal to 6, and R2
represents an alkyl radical, and
10
- at least one monoperoxycarbonate, conforming to the
formula (II):
(II)
15 in which formula (II) R1 represents an alkyl radical comprising
a number of carbon atoms of greater than or equal to 7, and R2 represents
an alkyl radical.
2. The use as claimed in claim 1, characterized in that the
20 composition comprises strictly less than 0.4% by weight of a tert-alkyl
hydroperoxide, calculated relative to 100 parts by weight of a mixture
of monoperoxycarbonate of formula (I) and monoperoxycarbonate of
formula (II).
3. The use as claimed in claim 1 or 2, characterized in that the
25 polyolefin elastomer is a copolymer of ethylene and at least one alpha -
olefin, preferably a linear, branched or cyclic C3 -C2 0 alpha-olefin.
4. The use as claimed in any of claims 1 to 3, characterized in
that the polyolefin elastomer is selected from the group consisting of
ethylene/propylene copolymers, ethylene/1 -butene copolymers,
R2 O O C O R1
O
R2 O O C O R1
O
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ethylene/1-hexene copolymers, ethylene/1-octene copolymers,
ethylene/styrene copolymers, ethylene/propylene/1 -octene copolymers,
ethylene/propylene/1-butene copolymers, ethylene/1-butene/1-octene
copolymers, and ethylene/1-butene/styrene copolymers.
5 5. The use as claimed in any of claims 1 to 4, characterized in
that the polyolefin elastomer is selected from the group consisting of
linear and uniformly branched copolymers of ethylene and alpha -olefin.
6. The use as claimed in any of the preceding claims,
characterized in that, in the formula (I), R1 is a C2 -C5 alkyl radical,
10 more preferably a C3 alkyl radical.
7. The use as claimed in any of the preceding claims,
characterized in that, in the formula (I), R2 is a C1 -C1 0 , preferably C4 -
C8 , alkyl radical, and preferably is a C5 or C6 alkyl radical, and more
preferably is a C5 alkyl radical.
15 8. The use as claimed in any of the preceding claims,
characterized in that the monoperoxycarbonate of formula (I) is selected
from the group consisting of tert-amylperoxy isopropyl monocarbonate
(TAIC), tert-butylperoxy isopropyl monocarbonate (TBIC), tertoctylperoxy isopropyl monocarbonate (TOIC), and tert-hexylperoxy
20 isopropyl monocarbonate (THIC), and preferably is tert-amylperoxy
isopropyl monocarbonate (TAIC).
9. The use as claimed in any of the preceding claims,
characterized in that, in the formula (II), R1 is a C7 -C1 0 , more preferably
C7 -C9 , alkyl radical, and more preferably is a C8 alkyl radical.
25 10. The use as claimed in any of the preceding claims,
characterized in that, in the formula (II), R2 is a C1 -C1 0 , preferably C2 -
C9 , particularly C4 -C8 , alkyl radical, and more preferably is a C4 or C5
alkyl radical, and more preferably still is a C4 alkyl radical.
11. The use as claimed in any of the preceding claims,
30 characterized in that the monoperoxycarbonate of formula (II) is
selected from the group consisting of OO-tert-amyl O-(2-ethylhexyl)
monoperoxycarbonate (TAEC), OO-tert-butyl O-(2-ethylhexyl)
monoperoxycarbonate (TBEC), OO-tert-octyl O-(2-ethylhexyl)
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monoperoxycarbonate (TOEC), and OO-tert-hexyl O-(2-ethylhexyl)
monoperoxycarbonate (THEC).
12. The use as claimed in any of the preceding claims,
characterized in that the mass ratio between the monoperoxycarbonate
5 of formula (I) and the monoperoxycarbonate of formula (II) varies in
the range from 0.1:99.9 to 80:20, preferably from 1:99 to 70:30, and
more preferably from 10:90 to 60:40.
13. A crosslinkable composition comprising:
- at least one polyolefin elastomer as defined in any of claims 1
10 to 5, preferably a copolymer of ethylene and at least one alpha -
olefin as defined in any of claims 3 to 5,
- at least one monoperoxycarbonate of formula (I) as defined in
any of claims 1 and 6 to 8,
- at least one monoperoxycarbonate of formula (II) as defined in
15 any of claims 1 and 9 to 11;
- the composition comprising preferably strictly less than 0.4%
by weight of a tert-alkyl hydroperoxide, calculated relative to 100 parts
by weight of the mixture of monoperoxycarbonate of formula (I) and
monoperoxycarbonate of formula (II).
20 14. The crosslinkable composition as claimed in claim 13,
characterized in that the amount of monoperoxycarbonates of
formulae (I) and (II) is less than or equal to 3 parts by weight per
100 parts by weight of the polyolefin elastomer.
15. The crosslinkable composition as claimed in claim 13 or 14,
25 characterized in that it further comprises at least one coagent other than
an organic peroxide, preferably selected from the group consisting of
triallyl cyanurate, triallyl isocyanurate, N,N'-m-phenylenedimaleimide,
triallyl trimellitate, trimethylolpropane triacrylate, and
trimethylolpropane trimethacrylate, preferably selected from the group
30 consisting of triallyl cyanurate, triallyl isocyanurate,
trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate,
and more preferably still is triallyl isocyanurate.
16. The use as claimed in any of claims 1 and 3 to 12 or
composition as claimed in any of claims 13 to 15, characterized in that
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the composition is devoid of a tert-alkyl hydroperoxide present in an
amount of from 0.4 to less than 4% by weight, calculated relative to
100 parts by weight of a mixture of monoperoxycarbonate of formula
(I) and monoperoxycarbonate of formula (II), particularly calculated
5 relative to 100 parts by weight of the total monoperoxycarbonate
content of the composition.
17. The use as claimed in any of claims 1 and 3 to 12 or
composition as claimed in any of claims 13 to 15, characterized in that
the composition is devoid of a tert-alkyl hydroperoxide.
10 18. A method for producing a material, comprising (a) at least
one step of crosslinking a crosslinkable composition as defined in any
of claims 13 to 17.
19. The method as claimed in claim 18, characterized in that the
material is selected from the group consisting of an encapsulating
15 material, particularly a material for encapsulating solar cells, wire and
cable insulation, pipes and hoses, r oller coatings, rotational moldings,
cellular articles, and shoe soles.
20. The method as claimed in claim 18 or 19, characterized in
that the crosslinking step (a) is implemented at a temperature of from
20 130 to 250°C, preferably from 130 to 180°C, more prefer ably of from
140 to 165°C.
21. The method as claimed in any of claims 18 to 20,
characterized in that it comprises a step prior to and/or simultaneous
with (a′) step (a), selected from the group consisting of molding,
25 extrusion, and injection-molding the crosslinkable composition as
defined in any of claims 13 to 17.
22. A material comprising at least one polyolefin elastomer,
obtainable by the method as defined in any of claims 18 to 21.
23. A method for producing a photovoltaic module, comprising:
30 (i) at least one step of laminating an assembly comprising in
succession:
 a first, transparent layer forming the front face of a
photovoltaic module,
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 a layer obtained from the crosslinkable composition as
defined in any of claims 13 to 17,
 a plurality of solar cells disposed side by side and
connected electrically to one another,
5  a layer obtained from the crosslinkable composition as
defined in any of claims 13 to 17,
 a second layer or a multilayer assembly forming the rear
face (or backing) of the module;
(ii) at least one step of pressing the layers laminated together
10 during step (i).
24. A photovoltaic module comprising a material for
encapsulating solar cells as defined in claim 23