Stable polyorganosiloxane based compositions with...

Details Stable polyorganosiloxane based compositions with... Stable polyorganosiloxane based compositions with...

2000-01-10

2001-04-17

Berman, Susan W. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

C522S031000, C522S078000, C522S099000, C522S148000, C524S714000, C524S722000, C528S013000, C528S021000, C528S023000, C528S032000, C528S033000

Reexamination Certificate

active

06218445

ABSTRACT:

The present invention relates to stable compositions based on polyorganosiloxanes containing cationically crosslinkable functional groups, to their use for preparing anti-adherent or anti-adhesive coatings and to articles consisting of a solid support, at least one surface of which is made anti-adherent or anti-adhesive by coating with the said functional polyorganosiloxanes crosslinked by photochemical or thermal activation and/or by activation with a beam of electrons.
It is known practice, for preparing anti-adhesive coatings, to use compositions based on a polyorganosiloxane containing functional groups (such as epoxy, vinyl ether, etc.) to which is added a cationic initiator onium salt for the crosslinking (patents U.S. Pat Nos. 4,450,360; 4,576,999; 4,640,967).
It has been found that the best results are obtained with onium salts in which the anion is SbF
6
−
. However, initiators containing this type of anion are difficult to manipulate and have considerable risks of toxicity.
Moreover, compositions based on UV-crosslinkable polyorganosiloxanes of the prior art can have problems of stability and of ageing in the presence or absence of light. In particular, it has been found that in the presence of a photoinitiator in the said compositions conditioned in liquid form, uncontrolled polymerization reactions of the polyorganosiloxanes took place in the medium without UV irradiation.
Furthermore, when a photoinitiator is used under liquid conditioning, it has a tendency to degrade, in particular releasing traces of acids, and gives reduced performance if it is used after a long period of storage.
The Applicant has found and developed novel compositions based on at least one polyorganosiloxane containing crosslinkable functional groups, these compositions having virtually none of the drawbacks of the compositions of the prior art. In particular, these novel polyorganosiloxane-based compositions contain a stabilizing amino agent capable of neutralizing the traces of acids, and have markedly improved stability on storage and during their use. Thus, uncontrolled polymerization reactions in the compositions are all but eliminated, without, however, reducing the ability of the said compositions to crosslink under controlled conditions.
The novel compositions in accordance with the invention are based:
on at least one polyorganosiloxane containing cationically crosslinkable functional groups,
an initiator system for curing under radiation, in particular UV radiation, and
an amino agent having properties of substantially improving the stability on storage and during use of the mixture of the polyorganosiloxane(s) with the photoinitiator.
The curing-initiator systems used in the compositions according to the invention are advantageously onium salts. In particular, the onium salts are chosen from at least one element from groups 15 to 17 of the Periodic Table (Chem. & Eng. News, Vol. 63, No. 5, 26 of Feb. 4, 1985), the cationic species and anionic species of which are defined below. The curing-initiator systems used in the context of the invention comprise one or more onium salts.
The cationic species of the onium salt is chosen from:
(1) Onium salts of formula
[(R
1
)
n
—A—(R
2
)
m
]
+
  (I)
 in which:
A represents an element from groups 15 to 17, such as I, S, Se, P and N,
the symbol R
1
represents a C
6
-C
20
carbocyclic or heterocyclic aryl radical, preferably phenyl, tolyl or toluyl, it being possible for the said heterocyclic radical to contain at least one hetero element, preferably nitrogen and/or sulphur,
the symbol R
2
represents R
1
, a linear or branched alkyl or alkenyl radical containing 1 to 30 carbon atoms,
the said radicals R
1
and R
2
optionally being substituted with an alkoxy group containing between 1 and 25 carbon atoms, an alkyl group containing 1 to 25 carbon atoms, a nitro group, a chloro group, a bromo group, a cyano group, a carboxyl group and/or a mercapto group,
n is an integer ranging from 1 to v+1, v being the valency of the element A,
m is an integer ranging from 0 to v−1, with n+m=v+1.
(2) The oxoisothiochromanium salts of formula:
in which the symbol R
3
represents a linear or branched alkyl radical containing 1 to 20 carbon atoms, a linear or branched cycloalkyl radical containing 1 to 20 carbon atoms, or an aryl radical.
By way of example, the oxoisothiochromanium salts which can be used are those which are described in particular in patent application WO A90/11303 (published on Oct. 4, 1990). As oxoisothiochromanium salts which are particularly suitable, mention will be made in particular of the sulphonium salt of 2-ethyl-4-oxoisothiochromanium or of 2-dodecyl-4-oxoisothiochromanium.
The anionic species of the said onium salt is chosen from the group consisting of SbF
6
−
, PF
6
, AsF
6
−
, CF
3
SO
3
−
, BF
4
−
, BCl
4
−
, B(O
3
SCF
3
)
4
−
, B(O
3
SC
2
F
5
)
4
−
, B(O
3
SC
4
F
9
)
4
−
. However, other anionic species can also be used, such as those described in patent application EP-A-697,449 (page 4, lines 28 to 37).
In addition, in the case of an anionic borate species, this can be chosen from the group consisting of the species of formula [BX
a
(R
4
)
b
]
−
(II), which moreover comprises BF
4
−
, BCl
4
−
, in which:
a is an integer between 0 and 4,
b is an integer between 0 and 4, with a+b=4,
the symbols X represent:
a halogen atom, preferably chlorine or fluorine,
an OH function with a=0 to 2,
the symbols R
4
are identical or different and represent:
a phenyl radical substituted with at least one electron-withdrawing group, preferably CF
3
, OCF
3
, NO
2
or CN, or with at least two halogen atoms, preferably fluorine,
an aryl radical containing at least two aromatic rings, such as biphenyl or naphthyl, optionally substituted with at least one electron-withdrawing element or group, preferably CF
3
, NO
2
or CN or a halogen atom, in particular fluorine.
Advantageously, the anionic borate species is the following anions:
[B(C
6
F
5
)
4
]
−
[B(C
6
H
4
CF
3
)
4
]
−
[B(C
6
H
3
(CF
3
)
2
)
4
]
−
[(C
6
F
5
)
2
BF
2
]
−
[B(C
6
H
4
OCF
3
)
4
]
−
[B(C
6
H
3
F
2
)
4
]
−
The onium salts of formula I are described in many documents, in particular in patents U.S. Pat. Nos. 4,026,705; 4,069,056; 4,136,102; 4,173,476. In particular, the cations used in the context of the invention are the following:
[(&PHgr;)
2
I]
+
[C
8
H
17
-O-&PHgr;-I-&PHgr;]
+
[C
12
H
25
-&PHgr;-I-&PHgr;]
+
[(C
8
H
17
-O-&PHgr;)
2
I]
+
[(&PHgr;)
3
S]
+
[(&PHgr;)
2
-S-&PHgr;-O-C
8
H
17
]
+
[&PHgr;-S-&PHgr;-S-(&PHgr;)
2
]
+
[(C
12
H
25
-&PHgr;)
2
I]
+
[CH
3
-&PHgr;-I-&PHgr;-CH(CH
3
)
2
]
+
[CH
3
-&PHgr;-I-&PHgr;-CH
3
]
+
et[(&PHgr;)
2
S-&PHgr;-S-&PHgr;-S(&PHgr;)
2
]
+2
In accordance with the invention, the initiators used are advantageously the following onium borates:
[(&PHgr;-CH
3
)
2
I]
+
, [B(C
6
F
5
)
4
]
−
,
[(&PHgr;)
2
I]
+
, [B(C
6
F
5
)
4
]
−
,
[C
12
H
25
-&PHgr;-I-&PHgr;]
+
, [B(C
6
F
5
)
4
]
−
,
[(C
8
H
17
-O-&PHgr;-I-&PHgr;]
+
,
[B(C
6
F
5
)
4
]
−
,
[(C
8
H
17
-O-&PHgr;)
2
I]
+
, [B(C
6
F
5
)
4
]
−
,
[(&PHgr;)
2
I]
+
, [B(C
6
H
3
(CF
3
)
2
)
4
]
−
,
[(&PHgr;)
2
S-&PHgr;-O-C
8
H
17
]
+
, [B(C
6
H
4
CF
3
)
4
]
−
,
[(C
12
H
25
-&PHgr;)
2
I]
+
, [B(C
6
F
5
)
4
]
−
,
[CH
3
-&PHgr;-I-&PHgr;-CH(CH
3
)
2
]
+
, [B(C
6
F
5
)
4
]
−
,
[(&PHgr;)
3
S]
+
, [B(C
6
F
5
)
4
]
−
,
[CH
3
-&PHgr;-I-&PHgr;-CH(CH
3
)
2
]
+
,
and
[B(C
6
H
4
OCF
3
)
4
]

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