Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-09-22
2002-06-18
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C528S015000, C528S020000, C525S477000, C525S478000, C556S451000, C568S873000
Reexamination Certificate
active
06406793
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a silicone pressure sensitive adhesive composition of addition reaction type and, more particularly, to an addition-reaction silicone pressure sensitive adhesive composition that can inhibit curing reaction from occurring in a treatment bath (which is prepared by dissolving the composition in an appropriate solvent) before the bath is used actually for treatment, and thereby can have improved working capability.
BACKGROUND OF THE INVENTION
Silicone pressure sensitive adhesives are highly resistant to heat, cold, weather and chemicals, and further have excellent electrical insulation capability. Therefore, they are used under such a severe condition that both acrylic and rubber pressure sensitive adhesives suffer deterioration to be rendered useless. As curing reactions caused in those silicone pressure sensitive adhesives, there are known the peroxide cross-linking reactions utilizing organic peroxides as catalysts and the cross-linking reaction utilizing the addition reaction occurring between SiH and alkenyl groups in the presence of platinum catalysts (Japanese Tokko Sho 54-37907, wherein the term “Tokko” means an “examined patent publication”).
The silicone pressure sensitive adhesives of the type which form cross-links by addition reaction (which are referred to as “addition-reaction silicone pressure sensitive adhesives”) have excellent low-temperature curability, and so require no high temperatures for curing. Consequently, the application of such pressure sensitive adhesives to substrates inferior in heat resistance has been carried forward.
However, the addition reaction is gradually progressing and the SiH groups of cross-linking agents are decreased by consumption even in the state of a treatment bath before application to substrates. Therefore, not only properties of pressure sensitive adhesive change but also the treatment bath causes an increase in viscosity or gelation with a lapse of time in some cases or the pressure sensitive adhesives reduce or lose their curability in other cases. Therefore, the usable term of the treatment bath is limited. In a particular case where a temperature rise is caused by stirring the treatment bath, there occurs a problem that the usable term is further shortened.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide an addition-reaction silicone pressure sensitive adhesive composition which hardly causes a viscosity increase or gelation but also inhibits a cross-linking agent from losing SiH groups and hardly suffer deterioration of tackiness characteristics even when many hours are passed in the state of a treatment bath prepared by dissolving the composition in an appropriate solvent before application to substrates.
The aforementioned object is attained with an addition-reaction silicone pressure sensitive adhesive composition comprising (A) diorganopolysiloxanes containing alkenyl groups the number of which is on average at least two a molecule, (B) an organopolysiloxane comprising R
2
3
SiO
C.5
units (wherein R
2
is an unsubstituted or substituted monovalent hydrocarbon group containing 1 to 10 carbon atoms) and SiO
2
units in a R
2
3
SiO
C.5
/SiO
2
ratio of from 0.6 to 1.3 by mole, (C) an organohydrogenpolysiloxane containing at least two per molecule of silicon-bonded hydrogen atoms, (D) an acetylene alcohol compound represented by the following formula,
wherein R
3
and R
4
are each a monovalent hydrocarbon group containing 1 to 8 carbon atoms and R
5
is a divalent hydrocarbon group containing 3 to 8 carbon atoms, (E) a silylated acetylene alcohol compound represented by the following formula,
wherein R
3
, R
4
and R
6
are each a monovalent hydrocarbon group containing 1 to 8 carbon atoms and R
5
is a divalent hydrocarbon group containing 3 to 8 carbon atoms, and (F) a platinum catalyst.
DETAILED DESCRIPTION OF THE INVENTION
The component (A) is constituted of diorganopolysiloxanes containing alkenyl groups the number of which is on average at least two a molecule, and they are preferably represented by the formula R
1
a
R
(3−a)
SiO—(R
1
RSiO)
m
—(R
2
SiO)
n
—SiR
1
a
R
(3−a)
.
In the above formula, R
1
is an alkenyl group represented by —C
i
H
2i
—CH═CH
2
(i=0 to 8); R groups, which may be the same or different, are each a substituted or unsubstituted 1-10C hydrocarbon group other than an alkenyl group; a is from 0 to 3 and m is a number of 0 or above, provided that the case of a=m=0 is excluded therefrom and the relation 2a+m≧2 is satisfied; and n is a number of at least 10.
Examples of R include alkyl groups such as methyl, ethyl, propyl and butyl groups, cycloalkyl groups such as cyclohexyl group, aryl groups such as phenyl and tolyl groups, and groups prepared by substituting hydroxy group(s), cyano group(s) or halogen atom(s) for a part or all of carbon-bonded hydrogen atoms in the groups as recited above, such as hydroxypropyl, cyanoethyl, 1-chloropropyl and 3,3,3-trifluoropropyl groups. Of these groups, methyl and phenyl groups are preferred in particular as R groups. Further, it is advantageous to the invention that at least 50% of all the R groups be methyl groups.
Examples of R
1
include vinyl, allyl, butenyl and hexenyl groups. In particular, vinyl group is preferred over the others. And a is preferably 1.
The diorganopolysiloxanes containing alkenyl groups as mentioned above may have a straight-chain structure or a branched structure. And they may be in a state of oil or gum. When they are in the state of oil, the suitable viscosity thereof is at least 50 cS at 25° C. However, it is advantageous that the diorganopolysiloxanes as Component (A) be in the state of gum. Additionally, a mixture of diorganopolysiloxanes having the same substituent composition but differring in polymerization degree may be used as Component (A).
The component (B) is constituted of at least one organopolysiloxane comprising R
2
3
SiO
0.5
units (wherein R
2
is an unsubstituted or substituted monovalent hydrocarbon group containing 1 to 10 carbon atoms) and SiO
2
units, wherein the mole ratio of R
2
3
SiO
0.5
units to SiO
2
units (hereinafter abbreviated as “R
2
3
SiO
0.5
/SiO
2
ratio”) is from 0.6 to 1.3. Examples of R
2
include an alkyl group such as methyl, ethyl, propyl or butyl group, a cycloalkyl group such as cyclohexyl group, an aryl group such as phenyl or tolyl group, and a group formed by substituting hydroxyl group(s), cyano group(s) or halogen atom(s) for a part or all of carbon-bonded hydrogen atoms in the groups as recited above, such as hydroxypropyl, cyanoethyl, 1-chloropropyl or 3,3,3-trifluoropropyl group. Of these groups, methyl and phenyl groups are especially preferred as R
2
groups. The component (B) is a component for imparting pressure sensitive adhesiveness to the present composition, and so the greater the amount of Component (B) used, the stronger the adhesion strength of the composition.
When the organopolysiloxane has a R
2
3
SiO
0.5
/SiO
2
ratio lower than 0.6 by mole, it tends to provide poor adhesion and tack; while, when the R
2
3
SiO
0.5
/SiO
2
ratio thereof is higher than 1.3 by mole, it tends to cause a lowering of holding power. The component (B) of the present composition may be a mixture of two or more of organopolysiloxanes meeting the foregoing restrictions. The component (A) and the component (B) may be used as a simple mixture thereof, or as a partially condensed product thereof. The suitable mixing ratio between the component (A) and the component (B) is from 20/80 to 80/20 by weight, particularly from 30/70 to 70/30 by weight.
The component (C), namely organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule, functions as a cross-linking agent. The organohydrogenpolysiloxane used as Component (C) may have any of straight-chain, branched and cyclic structures. Specifically, it can be represented by any of the following formulae, but these formulae should not be construed as limiting the scope of the organohy
Dawson Robert
Millen White Zelano & Branigan P.C.
Peng Kuo-Liang
Shin-Etsu Chemical Co. , Ltd.
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