Curable silicone compositions having enhanced...

Details Curable silicone compositions having enhanced... Curable silicone compositions having enhanced...

2002-11-04

2004-12-07

Robertson, Jeffrey B. (Department: 1712)

Coating processes

Direct application of electrical, magnetic, wave, or...

Polymerization of coating utilizing direct application of...

C427S387000, C522S065000, C522S099000, C522S148000, C528S012000, C528S022000, C528S032000, C528S038000, C528S041000, C525S477000

Reexamination Certificate

active

06827985

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to curable silicone compositions having enhanced cure-through-volume. More particularly, the present invention relates to curable silicone compositions incorporating as a property enhancing additive a curable amino functionalized silane or curable amino silyl-terminated silicone. Desirably the additive is an alkoxy/amino silyl-terminated polymer composition which is the reaction product of a silanol-terminated polyorganosiloxane and at least two end-capping silane components having different end-capping groups.
BACKGROUND OF RELATED TECHNOLOGY
Cure-through-volume (CTV) is an important property of photocurable silicone compositions. Conventional curable silicone compositions have been limited in their ability to cure through wide bond gaps or in potting applications requiring large depths. For example, CTV's of about 2 cm to about 5 cm are typical of conventional curable silicones. Additionally, the use of filler materials and pigments further impedes the ability of light curing sources to effectively penetrate the silicone compositions.
To enhance CTV's, conventional methods have focused on either reduction or elimination of filler and pigment additives, or on the use of polymers which are capable of curing through more than one curing mechanism. For example, one approach has been to use silicone polymers which are capable of both photo and moisture cure. While compositions containing such polymers have their own advantages, it would be desirable to have the ability to improve CTV without having to rely on secondary curing mechanisms and the specialized polymers which are generally used therefor. Decreasing or eliminating filler materials has not been a viable alternative because the overall physical properties of the cured polymers are compromised, often to the point of being commercially unacceptable. Thus, there is a need for photocurable silicone compositions which overcome the CTV limitations of conventional technology and which are capable of curing through greater depths without jeopardizing the structural integrity of the cured silicone and without the need for polymers which rely on secondary curing mechanisms to increase CTV. Moreover, it would be advantageous to have a photocurable silicone composition which is less sensitive to the level of fillers or to the opacity of the composition as a whole.
SUMMARY OF THE INVENTION
The present invention relates to photocurable silicone compositions having enhanced physical properties, and particularly increased CTV, due to the incorporation of a curable silicone-based additive. The curable silicone-based additive may be incorporated in amounts sufficient to provide enhanced CTV, elongation or other desirable properties. For example, incorporation of the additive in amounts of up to about 25% by weight of the total silicone composition, desirably in amounts of about 0.1% to about 15% by weight, and more desirably in amounts of about 1% to about 2%, provides greater depth of cure and wider bond-gap curing than similar compositions, including dual-curing silicone compositions, which do not incorporate the silicone-based additive.
In one aspect of the invention, there is included a photocurable silicone composition which contains a.) at least one photocurable silicone polymer; b.) a photoinitiator; and c.) at least one curable amino functionalized silicone or silane additive. Desirably the curable amino functionalized silicone additive includes a curable alkoxy/amino silyl-terminated polymer or polymer blend which is formed from the reaction of a silanol-terminated polyorganosiloxane with one or more end-capping silane components and desirably with at least two end-capping silane components having different end-capping groups.
In another aspect of the invention there is included a method of preparing a photocurable composition having enhanced cure-through-volume comprising the steps of (i) providing a photocurable silicone polymer and a photoinitiator; and (ii) incorporating therein a curable alkoxy/amino silyl-terminated polymer additive comprising the reaction product of at least one silanol terminated polyorganosiloxane and one or more end-capping silane components and desirably with at least two end-capping silane components having different reactive end-capping groups.
Another aspect of the invention includes a method of providing enhanced cure-through-volume (CTV) in a curable composition by applying the aforementioned silicone composition to a substrate and exposing it to sufficient light radiation to effectuate cure.
DETAILED DESCRIPTION OF THE INVENTION
Photocurable Silicone Component
The photocurable silicone component may be any photocurable silicone polymer. Among the useful photocurable silicone polymers are those described in U.S. Pat. Nos. 4,675,346, 4,528,081, 5,300,608 and 4,699,802, all of which are incorporated herein by reference.
More particularly, the reactive silicone polymers include those which conform to the general structure:
wherein R
1
is H or alkyl C
1-10
, desirably methyl; R
2
is a divalent hydrocarbon or hydrocarbonoxy group such as alkylene, alkyleneoxy, alkenylene or arylene; the R
3
and R
4
may be the same or different and are C
1-10
monovalent hydrocarbon radicals which are desirably alkyl, substituted alkyl, aryl, substituted aryl, alkoxy, aryloxy, (meth)acrylic, oxime, acetoxy, N,N-dialkylamino, N,N-dialkylamino, N-alkylamido or,
R is H or hydrocarbyl; R
5
is C
1-10
monovalent hydrocarbon radical and n is an integer between about 1 and 1200. R
2
is desirably alkylene or alkenylene C
1-3
, such as propylene and propenylene. Examples of useful R
3
and R
4
groups are alkyls such as methyl and ethyl; halo alkyls, such as trifluoropropyl; phenyl and benzyl. In the case where moisture curing is desired R
3
and R
4
will desirably be hydrolyzable groups and most desirably methoxy groups.
These reactive silicone polymers are desirably made from a material having at least one end terminating in a silanol group. The process of preparing the photocurable silicone polymers includes reacting the aforementioned material having at least one end terminating in a silanol group with a silane containing at least one photocurable group, and desirably more than one photocurable group.
The silanes useful for preparing the photocurable silicone polymers may have the general formula:
(R
6
)Si(OR
7
)
3
  II
wherein R
6
and R
7
can be identical or different monovalent hydrocarbon radicals having C
1-10
; R
6
may also be a monovalent heterohydrocarbon radical having 1 to 10 carbon atoms wherein the hetero atoms are selected from the group consisting of halo atoms, O, N and S.
Desirably, R
6
and R
7
are selected from the group consisting of methyl, ethyl, isopropyl, vinyl, phenyl, methacryloxypropyl and norbornenyltrimethoxy; and R
7
is desirably selected from the group consisting of methyl, ethyl, isopropyl and CH
2
CH
2
OCH
3
.
For example, one desirable silane is represented by the formula:
wherein R
1
, R
2
, R
3
and R
4
are as defined above.
Other polyalkoxysilanes useful in the present invention include:
Si(OCH
3
)
4
, Si(OCH
2
CH
3
)
4
, Si(OCH
2
CH
2
CH
3
)
4
, (CH
3
O)
3
SiCH
3
, (CH
5
O)
3
SiCH
3
,
(CH
3
O)
3
SiCH═CH
2
, (C
2
H
5
O)
3
SiCH═CH
2
,
(CH
3
O)
3
SiCH
2
—CH═CH
2
, (CH
3
O)
3
Si[CH
2
—(CH
3
)C═CH
2
],
(C
2
H
5
O)
3
Si(OCH
3
), Si(OCH
2
—CH
2
—OCH
3
)
4
, CH
3
Si(OCH
2
—CH
2
—OCH
3
)
3
,
CH
2
═CHSi(OCH
2
CH
2
OCH
3
)
3
, C
6
H
5
Si(OCH
3
)
3
, C
6
H
5
Si(OCH
2
—CH
2
—OCH
3
)
3
,
(CH
3
O)
3
Si[(CH
2
)
3
O—CH
2
—CH—CH
2
], (CH
3
O)
3
Si[(CH
2
)
3
—Cl],
(CH
3
O)
3
Si[(CH
2
)
3
OOC(CH
3
)C═CH
2
], (C
2
H
5
O)
3
Si(CH
2
)
2
CH
2
—Cl, (CH
3
O)
3
Si(CH
2
)
3
NH
2
,
(C
2
H
5
O)
3
Si(CH
2
)
3
NH
2
, (CH
3
O)
3
Si(CH
2
)
3
NH(CH
2
)
2
NH
2
, (C
2
H
5
O)
3
Si(CH
2
)
3
NH(CH
2
)
2
NH
2
,
(CH
3
O)
3
—Si(CH
2
)
3
SH, (CH
3
O)
3
Si[(CH
2
)
3
OOCH
2
═CH], and
Primary, secondary and tertiary amino silanes are also contemplated. For examp

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