Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-07-03
2003-05-06
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S451000
Reexamination Certificate
active
06558803
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
The present invention is directed to a crosslinkable perfluorinated polyether and method of preparation thereof, a release film and an adhesive tape formed thereof
Release coatings are used to control or diminish the adhesion between an adhesive and a backing or substrate to which the adhesive is applied. Release coatings may be employed in conjunction with release films, release liners, non-stick carrier webs, and coatings for paper and polymer substrates. A release coating may also comprise a component of a multi-layer or laminated construction. For example, a typical multi-layer or laminated construction may comprise a pressure sensitive adhesive attached to a foamed or non foamed sheet or film, with one or more release layers being employed on one or more of the backing or adhesive layers. The release layer in such a construction may serve as a protective layer during handling or storage, especially when the adhesive layer is wound upon itself such as in the form of an adhesive tape.
Perfluorinated polyethers have been used as release coatings. See, for example, U.S. Pat. Nos. 4,321,404; 4,472,480; 4,567,073; 4,820,588; and 4,830,910; as well as European Patent application Nos. 89,820; 98,698; 98,699; 244,839; 249,048; 337,346; 519,406; 622,353;622,391; 812,890; and 812,891. Perfluorinated polyethers can be either non-reactive oils (i.e., do not contain a reactive functionality), monofunctional or difunctional by nature, depending upon the number of terminal functional groups which are present on the polyether. However, the prior art focuses on use of identical functionalties in the preparation of such difunctional polyethers. The use of identical difunctionalities limits the ability of one skilled in the art to tailor the morphology of the network structure of the crosslinked perfluorinated polyether. Being able to control the morphology provides a means to tailor the release characteristics of the cured polyethers.
The practice of the prior art is dependent on the use of solvents to coat the perfluorinated polyethers. The use of solvents is a cause for safety, health and environmental pollution concerns. The ability to coat and cure perfluorinated polyethers of the present invention without the use of solvents is an advantage over the prior art.
The practice of the prior art is also dependent on the use of initiators, photoinitiators and catalysts (e.g., tin containing catalysts) that can leach out of the cured coating. The need of the sensitive electronics and medical markets for ultraclean materials imposes stringent demands on the amounts of leachable material in the coating.
OBJECTS AND SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide a novel crosslinkable perfluorinated polyether for use in the production of a release film.
It is also an object of the present invention to provide a novel crosslinked perfluorinated polyether release coating for use in conjunction with adhesives.
It is also an object of the present invention to provide an adhesive tape which includes a novel crosslinked perfluorinated polyether release coating.
Furthermore, it is an object of the present invention to provide a novel perfluorinated polyether that can be coated without the use of solvents (also called a 100% solid formulation) and subsequently be crosslinked.
The stringent requirements of the electronics and healthcare markets demand that the release liner be ultraclean. It is accordingly also an object of the present invention to provide chemistries that support the use of non-migrating initiators and catalysts, especially tin free catalyst systems.
In accordance with the present invention, there is thus provided a crosslinkable perfluorinated polyether, the polyether defined by the formula X
1
—(C
a
F
2a
O)
n
—X
2
where X
1
and X
2
are different functional terminal groups which are capable of forming a polymer by either addition, condensation or ring-opening reaction, n ranges from 1 to 2000 and a is an integer from 1 to 4, and wherein the ratio of X
1
to X
2
is 1:1.
In accordance with the present invention, there is also provided a release film comprising:
(1) a backing layer; and
(2) a release liner comprising a crosslinked perfluorinated polyether, the polyether defined by the formula X
1
—(C
a
F
2a
O)
n
—X
2
where X
1
and X
2
are different functional terminal groups which are capable of forming a polymer by either addition, condensation or ring-opening reaction, n ranges from 1 to 2000 and a is an integer from 1 to 4, and wherein the ratio of X
1
to X
2
is 1:1.
In accordance with another embodiment of the present invention, there is provided an adhesive tape comprising:
(1) at least one backing layer;
(2) at least one adhesive layer; and
(3) a release liner comprising a crosslinked perfluorinated polyether, the polyether defined by the formula X
1
—(C
a
F
2a
O)
n
—X
2
where X
1
and X
2
are different functional terminal groups which are capable of forming a polymer by either addition, condensation or ring-opening reaction, n ranges from 1 to 2000 and a is an integer from 1 to 4, and wherein the ratio of X
1
to X
2
is 1:1.
In accordance with the present invention there is further provided a method of production of a crosslinked perfluorinated polyether release film comprising the steps of:
(a) providing a solvent-free coatable crosslinkable perfluorinated polyether, the polyether defined by the formula X
1
—(C
a
F
2a
O)
n
—X
2
where X
1
and X
2
are different functional terminal groups which are capable of forming a polymer by addition, condensation or ring-opening reaction, n ranges from 1 to 2000 and a is an integer of from 1 to 4, and wherein the ratio of X
1
and X
2
is 1:1;
(b) coating said polyether on a substrate; and
(c) subjecting said coated polyether to a thermal or radiation source effective to crosslink said polyether.
DETAILED DESCRIPTION OF THE INVENTION
The novel release coating of the present invention is comprised of a crosslinked perfluorinated polyether, the polyether defined by the formula X
1
—(C
a
F
2a
O)
n
—X
2
where X
1
and X
2
are different functional terminal groups which are capable of forming a polymer by addition, condensation or ring opening reaction, n ranges from 1 to 2000 and a is an integer of from 1 to 4, and wherein the ratio of X
1
and X
2
is 1:1.
The perfluorinated polyether repeating units —(C
a
F
2a
O)
n
— used in the perfluorinated polyether of the present invention are known in the release coating art as disclosed in U.S. Pat. Nos. 4,321,404; 4,472,480; 4,567,073; 4,820,588 and 4,830,910, each herein incorporated by reference. In the —(C
a
F
2a
O)
n
— repeating unit a represents an integer of from 1 to 4 and n ranges from 1 to 2000.
The polyether can be crosslinked by reaction of terminal functional groups X
1
and X
2
by condensation, addition or ring opening reactions. The functionalized perfluorinated polyether of the present invention is a self-crosslinkable polyether.
The requisite crosslinking reaction can occur by means of condensation (either thermal or photoinitiated), cationic (either thermal or photoinitiated) reaction and/or free radical (either thermal or photo initiated) reaction.
The choice of X
1
and X
2
permits the requisite crosslinking to occur with the proviso that X
1
and X
2
are different. The use of different terminal functional groups encourages “chain extension” polymerization reactions to occur as opposed to “network/ladder-type” polymerization reactions. The choice of terminal functional groups enables one skilled in the art to tailor the relative reactivity of the terminal groups and control the morphology of crosslinking. This enables the ultimate release characteristics of the crosslinked polyether to be tailored to a specific application.
U.S. Pat. No. 4,472,480 at column 4, line 15 provides that the perfluoropolyether disclosed therein have an average number of identical terminal functionalities within the range of 1.5 to 2.0 to provide effective covalent bonding. By contrast, the present invention r
Adhesives Research Inc.
Birch & Stewart Kolasch & Birch, LLP
Nakarani D. S.
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