U.S. patent application number 16/768342 was filed with the patent office on 2022-01-20 for methods of preparing low tack soft gel compositions and such gel compositions prepared therefrom.
This patent application is currently assigned to COMMSCOPE CONNECTIVITY BELGIUM BVBA. The applicant listed for this patent is COMMSCOPE CONNECTIVITY BELGIUM BVBA. Invention is credited to Lydia AERTGEETS, Valja EVERAERT, Ana NEDELCHEVA HRISTOVA, Kristel VAN RENTERGHEM.
Application Number | 20220017700 16/768342 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-20 |
United States Patent
Application |
20220017700 |
Kind Code |
A2 |
EVERAERT; Valja ; et
al. |
January 20, 2022 |
METHODS OF PREPARING LOW TACK SOFT GEL COMPOSITIONS AND SUCH GEL
COMPOSITIONS PREPARED THEREFROM
Abstract
Disclosed herein are methods of preparing thermoplastic gels and
dry silicone gels with an alkyl ester polydimethylsiloxane having a
formula (I): (I) Also disclosed are thermoplastic gels and dry
silicone gels prepared by the disclosed methods. In the formula
(I), n is about 60% to about 90% of the formula (I); m is about 10%
to about 40% of the formula (I); R is --(C.dbd.O)--OR.sub.1; and R
is a C.sub.2-C.sub.20 alkyl group. The alkyl ester
polydimethylsiloxane has a weight average molecular weight of about
10,000 g/mol to about 50,000 g/mol. The hardness of the
thermoplastic gels is less than 120 g peak load. The hardness of
the dry silicone gels is less than 100 g peak load.
Inventors: |
EVERAERT; Valja; (Wetteren,
BE) ; VAN RENTERGHEM; Kristel; (Kortrijk-Dustel,
BE) ; AERTGEETS; Lydia; (Begijnendijk, BE) ;
NEDELCHEVA HRISTOVA; Ana; (Holsbeek, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COMMSCOPE CONNECTIVITY BELGIUM BVBA |
Kessel-Lo |
|
BE |
|
|
Assignee: |
COMMSCOPE CONNECTIVITY BELGIUM
BVBA
Kessel-Lo
BE
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20210171717 A1 |
June 10, 2021 |
|
|
Appl. No.: |
16/768342 |
Filed: |
November 30, 2018 |
PCT Filed: |
November 30, 2018 |
PCT NO: |
PCT/EP2018/083194 PCKC 00 |
371 Date: |
May 29, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62593314 |
Dec 1, 2017 |
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International
Class: |
C08G 77/14 20060101
C08G077/14; C08L 83/04 20060101 C08L083/04; C08J 3/24 20060101
C08J003/24 |
Claims
1.-38. (canceled)
39. A method of preparing a low tack soft polymer gel, comprising:
preparing a polymer gel composition; and treating the polymer gel
composition with an alkyl ester polydimethylsiloxane having a
formula (I): ##STR00013## where n is about 60% to about 90% of the
formula (I); m is about 10% to about 40% of the formula (I); R is
--(C.dbd.O)--OR.sub.1; and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group, wherein the alkyl ester polydimethylsiloxane has a weight
average molecular weight of about 10,000 g/mol to about 50,000
g/mol, to provide the low tack soft polymer gel.
40. The method of claim 39, wherein the low tack soft polymer gel
has a tack time of about 2 seconds or less.
41. The method of claim 40, wherein the low tack soft polymer gel
has a tack time of about 1 second or less.
42. The method of claim 39, wherein the low tack soft polymer gel
has an adhesiveness less than 20 mJ.
43. The method of claim 39, wherein n is about 70% to about 80% of
the formula (I).
44. The method of claim 39, wherein m is about 20% to about 30% of
the formula (I).
45. The method of claim 39, wherein the alkyl ester
polydimethylsiloxane has a weight average molecular weight of about
15,000 g/mol to about 45,000 g/mol.
46. The method of claim 39, wherein the alkyl ester
polydimethylsiloxane has a weight average molecular weight of about
20,000 g/mol to about 40,000 g/mol.
47. The method of claim 46, wherein the alkyl ester
polydimethylsiloxane has a weight average molecular weight of about
25,000 g/mol to about 35,000 g/mol.
48. The method of claim 47, wherein the alkyl ester
polydimethylsiloxane has a weight average molecular weight between
about 31,000 and about 33,000.
49. The method of claim 39, wherein III is a C.sub.9 to C.sub.18
alkyl group.
50. The method of claim 39, wherein the alkyl ester
polydimethylsiloxane has a number average molecular weight between
about 13,000 and about 14,000.
51. The method of claim 39, wherein the alkyl ester
polydimethylsiloxane has a polydispersity index between about 2 and
about 3.
52. The method of claim 51, wherein the alkyl ester
polydimethylsiloxane has a polydispersity index between about 2.3
and about 2.4.
53. The method of claim 39, wherein the low tack soft polymer gel
exhibits a hardness of less than 120 g peak load.
54. The method of claim 39, wherein the polymer gel composition is
selected from the group consisting of a thermoplastic gel
composition and a silicone gel composition.
55. The method of claim 54, wherein the preparing of the silicone
gel composition comprises preparing an uncured silicone gel
composition; and curing the uncured silicone gel composition to
provide a cured silicone gel comprising crosslinked silicone
polymers having a Si--O backbone.
56. The method of claim 55, wherein preparing the uncured silicone
gel composition comprises mixing a base polymer having a Si-vinyl
group, a crosslinker, and a chain extender.
57. The method of claim 56, wherein the base polymer is a
vinyl-terminated polydimethylsiloxane.
58. The method of claim 55, wherein the treating comprises treating
the cured silicone gel or uncured silicone gel composition with the
alkyl ester polydimethylsiloxane of formula (I) to provide the low
tack soft polymer gel.
59. The method of claim 58, wherein the treating comprises treating
a surface of the cured silicone gel or uncured silicone gel
composition with the alkyl ester polydimethylsiloxane of formula
(I).
60. The method of claim 58, wherein the treating comprises mixing
into the uncured silicone gel composition the alkyl ester
polydimethylsiloxane having a formula (I).
61. The method of claim 54, wherein the silicone gel composition is
a dry silicone gel composition.
62. The method of claim 54, wherein the preparing of the
thermoplastic gel composition comprises mixing a styrene triblock
copolymer, a styrene diblock copolymer, or a combination thereof,
with an oil extender to provide a pre-swell.
63. The method of claim 62, wherein the styrene triblock copolymer
is selected from poly(styrene-butadiene-styrene),
poly(styrene-ethylene/butylene-styrene),
poly(styrene-ethylene/propylene-styrene),
poly(styrene-ethylene/ethylene-propylene-styrene),
poly(styrene-isoprene-styrene), and combinations thereof.
64. The method of claim 62, wherein the styrene diblock copolymer
is selected from poly(styrene-ethylene/propylene),
poly(styrene-ethylene/butylene), and combinations thereof.
65. The method of claim 62, wherein the treating comprises treating
the pre-swell with the alkyl ester polydimethylsiloxane of formula
(I).
66. The method of claim 65, wherein the treating of the pre-swell
comprises mixing into the pre-swell the alkyl ester
polydimethylsiloxane of formula (I) to provide the low tack soft
polymer gel.
67. The method of claim 62, further comprising shaping the
pre-swell to provide a shaped thermoplastic gel.
68. The method of claim 67, wherein the treating comprises treating
a surface of the shaped thermoplastic gel with the alkyl ester
polydimethylsiloxane having a formula (I) to provide the low tack
soft polymer gel.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Patent
Application Ser. No. 62/593,314, filed on Dec. 1, 2017, the
disclosure of which is incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] The present disclosure relates generally to methods of
preparing gel formulations and gel formulations prepared by such
methods. In particular, the present disclosure relates to methods
of preparing thermoplastic gel formulations exhibiting low tack and
hardness less than 120 g peak load and such thermoplastic gel
formulations prepared therefrom. The present disclosure also
relates to methods of preparing dry silicone gel formulations
exhibiting low tack and hardness less than 100 g peak load and such
dry silicone gel formulations prepared therefrom.
BACKGROUND
[0003] Gel seal arrangements for fiber optic cables apply pressure
to gel contained therein causing the gel to conform to the fiber
optic cables and overcome any penetrating fluid pressure (e.g.,
from air or water). Softer gels used in cable gel seal arrangements
as well as for sealing enclosures are subject to significant
tackiness. For example, dry silicone gels suffer from an extremely
high level of tackiness/stickiness which increases the softer the
gel becomes. Consequently, handling of the gels becomes difficult.
For example, the gels are difficult to handle and cut. Also,
re-entry of fiber optic closures in the field after first
installation is not possible in view of the tackiness/stickiness,
although re-entry is key in some applications as a fiber optic
network is constantly changing and additional customers need to be
added over time.
[0004] For both thermoplastic gel formulations and dry silicone gel
formulations, there is a need for improved soft gel formulations
having a lower hardness that also exhibit a sufficiently low tack.
There is also a need for improved soft gel formulations that can be
more easily handled (e.g., more easily cut during manufacturing,
and suitably used for re-entry operations).
SUMMARY
[0005] Disclosed herein is a method of preparing a thermoplastic
gel. The method comprises preparing a composition comprising a
styrene triblock copolymer, a styrene diblock copolymer, or a
combination thereof; and an oil extender to provide a pre-swell.
The method further comprises shaping the pre-swell to provide a
shaped thermoplastic gel. The method additionally comprises
treating a surface of the shaped thermoplastic gel with an alkyl
ester polydimethylsiloxane having a formula (I) to provide the
thermoplastic gel:
##STR00001##
In the formula (I), n is about 60% to about 90% of the formula (I);
m is about 10% to about 40% of the formula (I); R is
--(C.dbd.O)--OR.sub.1; and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group. The alkyl ester polydimethylsiloxane has a weight average
molecular weight of about 10,000 g/mol to about 50,000 g/mol. The
hardness of the thermoplastic gel is less than 120 g peak load.
[0006] Disclosed herein is another method of preparing a
thermoplastic gel. The method comprises preparing a composition
comprising a styrene triblock copolymer, a styrene diblock
copolymer, or a combination thereof; and an oil extender to provide
a pre-swell. The method further comprises mixing into the pre-swell
an alkyl ester polydimethylsiloxane having a formula (I) to provide
the thermoplastic gel:
##STR00002##
In the formula (I), n is about 60% to about 90% of the formula (I);
m is about 10% to about 40% of the formula (I); R is
--(C.dbd.O)--OR.sub.1; and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group. The alkyl ester polydimethylsiloxane has a weight average
molecular weight of about 10,000 g/mol to about 50,000 g/mol. The
hardness of the thermoplastic gel is less than 120 g peak load.
[0007] Also disclosed herein are thermoplastic gels prepared by the
methods disclosed herein.
[0008] Disclosed herein is a method of preparing a dry silicone
gel. The method comprises preparing an uncured silicone gel
composition. The method further comprises curing the uncured
silicone gel composition to provide a cured silicone gel comprising
crosslinked silicone polymers having a Si--O backbone. The method
further comprises treating a surface of the cured silicone gel with
an alkyl ester polydimethylsiloxane having a formula (I) to provide
the dry silicone gel:
##STR00003##
In the formula (I), n is about 60% to about 90% of the formula (I);
m is about 10% to about 40% of the formula (I); R is
--(C.dbd.O)--OR.sub.1; and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group. The alkyl ester polydimethylsiloxane has a weight average
molecular weight of about 10,000 g/mol to about 50,000 g/mol. The
hardness of the dry silicone gel is less than 100 g peak load.
[0009] Disclosed herein is another method of preparing a dry
silicone gel. The method comprises preparing an uncured silicone
gel composition. The method further comprises, after a start of
reaction but prior to curing, treating a surface of the composition
with an alkyl ester polydimethylsiloxane having a formula (I):
##STR00004##
In the formula (I), n is about 60% to about 90% of the formula (I);
m is about 10% to about 40% of the formula (I); R is
--(C.dbd.O)--OR.sub.1; and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group. The alkyl ester polydimethylsiloxane has a weight average
molecular weight of about 10,000 g/mol to about 50,000 g/mol. The
method additionally comprises curing the composition to provide the
dry silicone gel comprising crosslinked silicone polymers having a
Si--O backbone. The hardness of the dry silicone gel is less than
100 g peak load.
[0010] Disclosed herein is yet another method of preparing a dry
silicone gel. The method comprises preparing an uncured silicone
gel composition. The method further comprises, prior to curing the
uncured silicone gel composition, mixing into the uncured silicone
gel composition an alkyl ester polydimethylsiloxane having a
formula (I):
##STR00005##
In the formula (I), n is about 60% to about 90% of the formula (I);
m is about 10% to about 40% of the formula (I); R is
--(C.dbd.O)--OR.sub.1; and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group. The alkyl ester polydimethylsiloxane has a weight average
molecular weight of about 10,000 g/mol to about 50,000 g/mol. The
method additionally comprises curing the composition to provide the
dry silicone gel comprising crosslinked silicone polymers having a
Si--O backbone. The hardness of the dry silicone gel is less than
100 g peak load.
[0011] Further disclosed herein are dry silicone gels prepared by
the methods disclosed herein.
DETAILED DESCRIPTION
[0012] Aspects of the present disclosure relate to methods of
preparing soft gels having reduced tackiness without compromising
the hardness characteristics of the gel. For example, aspects of
the present disclosure relate to methods of preparing soft gels
having a hardness less than 120 g peak load or a hardness less than
100 g peak load and low tackiness with tack times of 2 seconds or
less or 1 second or less and/or adhesiveness less than 20 mJ.
Furthermore, the gels can better maintain their reduced tackiness
over time, and in some cases, permanently.
[0013] Aspects of the present disclosure further relate to methods
of preparing gels having an additive dispersed throughout the gel
or, alternatively, on the surface of the gel. Therefore, the
additive can provides a softer gel with improved handling (e.g.,
easier cutting and manufacturing operations, and easier re-entry in
the field).
[0014] The inventors have discovered that adding a small amount of
an alkyl ester polydimethylsiloxane to the gel surface directly,
either before or after curing, provides a significantly reduced
tackiness without compromising the hardness characteristics of the
gel. Thus, the gels disclosed herein can be manufactured with ease
(e.g., by spraying, painting, or brushing the additive onto the gel
surface).
[0015] The inventors have further discovered that adding the alkyl
ester polydimethylsiloxane to the gel surface after curing is very
effective. For example, by this method, only small amounts of the
alkyl ester polydimethylsiloxane need to be added to achieve
reduced tackiness without compromising the hardness
characteristics.
[0016] Adding the alkyl ester polydimethylsiloxane to the gel
surface before curing (but after a start of reaction in the uncured
composition) is also effective.
[0017] The inventors have also discovered that mixing a small
amount of an alkyl ester polydimethylsiloxane into a gel
composition, after mixing the gel components but prior to curing,
advantageously provides reduced tackiness without compromising the
hardness of the gel. Mixing the alkyl ester polydimethylsiloxane
into the uncured gel composition prior to curing can also impart
reduced tackiness throughout the body of the gel. This preparation
method is beneficial when the gel needs to be cut or otherwise
handled, either during manufacturing or by a user. Importantly,
mixing the alkyl ester polydimethylsiloxane with other gel-forming
components during preparation of the uncured gel composition is not
effective.
[0018] As used herein, the term "curing" refers to chemical
crosslinking of polymer chains upon introduction of some type of
reaction accelerant such as heat or UV light. Thus, "curing" is
distinguished from reaction and crosslinking that occurs at room
temperature. "Curing" requires some kind of accelerant of the
reaction. "Curing" does not occur upon mere mixing of gel-forming
components.
[0019] As used herein, "preparing an uncured composition" refers to
mixing gel-forming components to prepare the uncured composition.
There is no limitation on the method of mixing. For example, all
gel-forming components can be mixed together simultaneously or
gel-forming components can be mixed together sequentially.
[0020] As used herein, "shaping" refers to any method that can be
used to impart a shape to a thermoplastic gel, for example, molding
or extruding.
[0021] In regard to thermoplastic gels, providing a pre-swell
generally involves mixing the styrene triblock copolymer, the
styrene diblock copolymer, or a combination thereof with the oil
extender and allowing the mixture to sit at room temperature. There
is no limitation on the method of mixing. For example, all
gel-forming components can be mixed together simultaneously or
gel-forming components can be mixed together sequentially.
Alkyl Ester Polydimethylsiloxane Additive
[0022] The alkyl ester polydimethylsiloxane additive used in the
gel preparation methods disclosed herein has the formula (I):
##STR00006##
[0023] In the formula (I), n is about 60% to about 90% of the
formula (I). In embodiments, n is about 70% to about 80% of the
formula (I). In the formula (I), m is about 10% to about 40% of the
formula (I). In embodiments, m is about 20% to about 30% of the
formula (I). For example, n can be about 75% of the formula (I) and
m can be about 25% of the formula (I). In the formula (I), R is
--(C.dbd.O)--OR.sub.1 and R.sub.1 is a C.sub.2-C.sub.20 alkyl
group. In embodiments, R.sub.1 is a C.sub.2-C.sub.18 alkyl group.
In embodiments, R.sub.1 is a C.sub.2-C.sub.16 alkyl group. In
embodiments, R.sub.1 is a C.sub.4-C.sub.20 alkyl group. In
embodiments, R.sub.1 is a C.sub.4-C.sub.18 alkyl group. In
embodiments, R.sub.1 is a C.sub.4-C.sub.16 alkyl group. In
embodiments, R.sub.1 is C.sub.6-C.sub.20 alkyl group. In
embodiments, R.sub.1 is a C.sub.6-C.sub.18 alkyl group. In
embodiments, R.sub.1 is a C.sub.6-C.sub.16 alkyl group. In
embodiments, R.sub.1 is a C.sub.9-C.sub.20 alkyl group. In
embodiments, R.sub.1 is a C.sub.9-C.sub.18 alkyl group. In
embodiments, R.sub.1 is a C.sub.9-C.sub.16 alkyl group. In
embodiments, R.sub.1 is a C.sub.1-C.sub.20 alkyl group. In
embodiments, R.sub.1 is a C.sub.1-C.sub.18 alkyl group. In
embodiments, R.sub.1 is a C.sub.1-C.sub.16 alkyl group. Generally,
R.sub.1 is a linear alkyl group. However, R.sub.1 can be a
combination of linear alkyl groups and branched alkyl groups.
[0024] In the formula (I), R.sub.1 can also be a C.sub.2-C.sub.2O
alkenyl group. In embodiments, R.sub.1 can be a C.sub.3-C.sub.20
alkenyl group. In embodiments, R.sub.1 can be a C.sub.4-C.sub.20
alkenyl group. In embodiments, R.sub.1 can be a C.sub.2-C.sub.18
alkenyl group, a C.sub.2-C.sub.16 alkenyl group, a C.sub.3-C.sub.18
alkenyl group, a C.sub.3-C.sub.16 alkenyl group, a C.sub.4-C.sub.18
alkenyl group, a C.sub.4-C.sub.16 alkenyl group, a C.sub.6-C.sub.20
alkenyl group, a C.sub.6-C.sub.18 alkenyl group, a C.sub.6-C.sub.16
alkenyl group, a C.sub.9-C.sub.20 alkenyl group, a C.sub.9-C.sub.18
alkenyl group, or a C.sub.9-C.sub.16 alkenyl group. Generally,
R.sub.1 is a linear alkenyl group. However, R.sub.1 can be a
combination of linear alkenyl groups and branched alkenyl
groups.
[0025] As used herein, an "alkenyl group" can have one or more
carbon-carbon double bonds. For example, an "alkenyl group" can be
an alkadienyl group (i.e., having two carbon-carbon double bonds).
For example, R.sub.1 can be a C.sub.4-C.sub.20 alkadienyl
group.
[0026] In reference to the above, R.sub.1 can be an alkyl group, an
alkenyl group, or combinations thereof.
[0027] In embodiments, the alkyl ester polydimethylsiloxane
additive can contain hexadecene as an impurity in an amount between
about 0.01 wt % and about 5 wt %.
[0028] In embodiments, the weight average molecular weight of the
alkyl ester polydimethylsiloxane is in the range of about 10,000
g/mol to about 50,000 g/mol. In embodiments, the weight average
molecular weight of the alkyl ester polydimethylsiloxane is in the
range of about 15,000 g/mol to about 45,000 g/mol. In embodiments,
the weight average molecular weight of the alkyl ester
polydimethylsiloxane is in the range of about 20,000 g/mol to about
40,000 g/mol. In embodiments, the weight average molecular weight
of the alkyl ester polydimethylsiloxane is in the range of about
25,000 g/mol to about 35,000 g/mol.
[0029] In some embodiments, the gel comprises about 0.01 wt % to
about 2 wt % of the additive, about 0.1 wt % to about 2 wt % of the
additive, about 0.01 wt % to about 1.5 wt % of the additive, about
0.1 wt % to about 1.5 wt % of the additive, about 0.01 wt % to
about 1.3 wt %, about 0.1 wt % to about 1.3 wt %, about 0.01 wt %
to about 1 wt % of the additive, about 0.1 wt % to about 1 wt %,
about 0.01 wt % to about 0.7 wt %, or about 0.1 wt % to about 0.7
wt %. In some embodiments, the gel comprises about 2 wt % of the
additive. In some embodiments, the gel comprises about 1 wt % of
the additive. In some embodiments, the gel comprises about 0.1 wt %
of the additive. In some embodiments, the gel comprises about 0.01
wt % of the additive. In some embodiments, the gel comprises about
0.01 wt % to about 0.1 wt % of the additive. In other embodiments,
the gel comprises from about 1 wt % to about 2 wt % of the
additive. In other embodiments, the gel comprises about 0.7 wt % to
about 1.3 wt % of the additive. These weight percentages are based
on the final gel weight.
Thermoplastic Gel
[0030] The thermoplastic gel prepared by the methods disclosed
herein has a hardness of less than 120 g peak load. In embodiments,
the thermoplastic gel has a hardness of less than 110 g peak load.
In embodiments, the thermoplastic gel has a hardness of less than
100 g peak load.
[0031] In embodiments, the thermoplastic gel prepared by the
methods disclosed herein has a tack time of about 2 seconds or
less. In embodiments, the thermoplastic gel has a tack time of
about 1 second or less. In embodiments, the thermoplastic gel has a
tack time of less than 2 seconds. In embodiments, the thermoplastic
gel has a tack time of less than 1 second.
[0032] In embodiments, the thermoplastic gel prepared by the
methods disclosed herein has an adhesiveness less than 20 mJ. In
embodiments, the thermoplastic gel has an adhesiveness less than 10
mJ. In embodiments, the thermoplastic gel has an adhesiveness less
than 5 mJ. In embodiments, the thermoplastic gel has an
adhesiveness less than 1 mJ. In embodiments, the thermoplastic gel
has an adhesiveness less than 0.75 mJ.
[0033] As used herein, the term "styrene diblock copolymer" refers
to a diblock copolymer having a polystyrene segment and another
elastomeric segment. Styrene diblock copolymers are known. Examples
of a "styrene diblock copolymer" include
poly(styrene-ethylene/propylene) (SEP),
poly(styrene-ethylene/butylene), and combinations thereof. Other
examples of a "styrene diblock copolymer" include
poly(styrene-butadiene) and poly(styrene-isoprene). The styrene
diblock copolymer can have about 25 wt % to about 40 wt % styrene,
for example, between about 30 wt % and about 40 wt % styrene or
between about 35 wt % and about 40 wt % styrene.
[0034] As used herein, the term "styrene triblock copolymer" refers
to a triblock copolymer having polystyrene end segments and another
elastomeric center segment. Styrene triblock copolymers are known.
Examples of a "styrene triblock copolymer" include
poly(styrene-butadiene-styrene) (SBS),
poly(styrene-ethylene/butylene-styrene) (SEBS),
poly(styrene-ethylene/propylene-styrene) (SEPS),
poly(styrene-ethylene/ethylene-propylene-styrene) (SEEPS), and
combinations thereof. Another example of a "styrene triblock
copolymer" is poly(styrene-isoprene-styrene) (SIS). The styrene
triblock copolymer can have about 25 wt % to about 40 wt % styrene,
for example, between about 30 wt % and about 40 wt % styrene or
between about 35 wt % and about 40 wt % styrene.
[0035] In embodiments where the thermoplastic gel is with both a
styrene triblock copolymer and a styrene diblock copolymer, about
10 wt % to about 20 wt % of the styrene triblock copolymer and
about 4 wt % to about 10 wt % of the styrene diblock copolymer can
be used in combination. For example, about 12 wt % to about 16 wt %
of the styrene triblock copolymer and about 5 wt % to about 7 wt %
of the styrene diblock copolymer can be used in combination.
[0036] In some embodiments, a combination of SEPS triblock
copolymer and SEP diblock copolymer is used. In some embodiments,
two or more types of SEPS triblock copolymers are used. In some
embodiments, two types of SEPS triblock copolymers are used.
[0037] In some embodiments, from about 10 wt % to about 20 wt % of
the styrene triblock copolymer is used. For example, from about 15
wt % to about 20 wt % of the styrene triblock copolymer can be
used.
[0038] About 60 wt % to about 90 wt % of the oil extender can be
used. For example, about 70 wt % to about 85 wt % of the oil
extender can be used. As another example, about 75 wt % to about 85
wt % of the oil extender can be used. As yet another example, about
75 wt % to about 81 wt % of the oil extender can be used. The oil
extender may be selected from oils conventionally used to extend
copolymer materials and are known in the art. The oil may be a
hydrocarbon oil such as paraffinic oil, naphthenic oil, or
polyalphaolefin (PAO) oil such as polydecene, polydodecene, or
polytetradecene; a synthetic oil such as polybutene or polypropene
oil, and mixtures thereof. For example, the oil extender can be a
mixture of a non-aromatic paraffin and a naphthenic hydrocarbon
oil.
Dry Silicone Gel
[0039] The dry silicone gel prepared by the methods disclosed
herein has a hardness of less than 100 g peak load. In embodiments,
the dry silicone gel has a hardness of less than 75 g peak load. In
embodiments, the dry silicone gel has a hardness of less than 70 g
peak load.
[0040] In embodiments, the dry silicone gel prepared by the methods
disclosed herein has a tack time of about 2 seconds or less. In
embodiments, the dry silicone gel has a tack time of about 1 second
or less. In embodiments, the dry silicone gel has a tack time of
less than 2 seconds. In embodiments, the dry silicone gel has a
tack time of less than 1 second.
[0041] In embodiments, the dry silicone gel prepared by the methods
disclosed herein has an adhesiveness less than 20 mJ. In
embodiments, the dry silicone gel has an adhesiveness less than 10
mJ. In embodiments, the dry silicone gel has an adhesiveness less
than 5 mJ.
[0042] As used herein, a "dry silicone gel" has crosslinked
silicone polymers having a Si--O backbone and does not include any
diluent fluid such as silicone oil or mineral oil. As opposed to
carbon-based polymer, the crosslinked silicone polymer of dry
silicone gels are based on a Si--O backbone. The characteristics of
silicon and oxygen provide crosslinked polymers with their
exceptional properties. For example, silicon forms stable
tetrahedral structures, and silicon-oxygen bonds are relatively
strong which results in dry silicone gels with high temperature and
creep resistance. In addition, crosslinked Si--O polymers have a
relatively high chain flexibility as well as low rotational energy
barrier.
[0043] The dry silicone gels may be made according to a number of
different polymerization reactions. In certain embodiments, the
polymerization reaction is a hydrosilylation reaction, also
referred to as a hydrosilation reaction. In some embodiments, the
hydrosilylation reaction makes use of a platinum catalyst, while
other embodiments make use of radicals. In further embodiments, the
dry silicone gel is made by a dehydrogenated coupling reaction. In
other embodiments, the dry silicone gel is made by a condensation
cure RTV reaction.
[0044] In embodiments, the uncured silicone gel composition
prepared in the methods disclosed herein comprises a base polymer
having a Si-vinyl group. In other embodiments, the uncured silicone
gel composition prepared in the methods disclosed herein comprises
monomers that upon a chemical reaction and crosslinking provide
crosslinked silicone polymers having a Si--O backbone. In
embodiments, preparing the uncured silicone gel composition
comprises mixing a base polymer having a Si-vinyl group (e.g., a
vinyl-terminated polydimethylsiloxane), a crosslinker, and a chain
extender.
[0045] In certain embodiments, the dry silicone gel is made by an
addition cure or platinum cure reaction mechanism. In some
embodiments, the mechanism employs the use of a catalyst. By using
a catalyst, the activation energy of the reaction is lowered and
faster curing times at lower temperatures can be achieved. A
schematic overview of the platinum cure reaction mechanism is shown
below in (I).
##STR00007##
[0046] For the reaction in (I) to be made possible, two functional
groups must react with each other. In certain embodiments, the two
functionalities are (1) the Si--H group and (2) the Si-vinyl group.
These two functionalities may be provided by: (1) a base polymer,
(2) a crosslinker, and (3) a chain extender.
Base Polymer
[0047] In certain embodiments, the Si-vinyl group is provided by a
base polymer such as a vinyl terminated polydimethylsiloxane
(otherwise referred to as "V-PDMS"), which is shown below in (II).
In this example, the base polymer compound comprises a vinyl group
at each end of the compound.
##STR00008##
[0048] In certain embodiments, the molecular weight of the base
polymer is controlled through anionic ring-opening polymerization
of cyclic siloxanes in the presence of alkali-metal hydroxide of a
base that is volatile (e.g., tetramethylammonium silanolate).
Encapping of the PDMS with a vinyl group is needed, so these groups
are added to the polymerization mixture. V-PDMS together with the
chain extender determine the molecular weight between the different
crosslink sites.
[0049] The vinyl-containing base polymer, such as V-PDMS, may have
different viscosities that affect the resulting dry silicone gel.
In general a high molecular weight V-PDMS will produce an uncured
gel with a higher viscosity. In certain embodiments, a lower
molecular weight V-PDMS generally improves processability.
[0050] The hardness of the dry silicone gel depends upon the number
of vinyl groups that are unreacted both at the surface of the gel
and inside the gel. The excess unreacted vinyl groups result in the
gel being softer and also causes the gel to be subject to
tackiness.
Crosslinker
[0051] In certain embodiments, the Si--H end groups for the
reaction in (I) may be provided by a crosslinker and/or a chain
extender. A crosslinker is capable of forming connections between
vinyl-terminated polydimethylsiloxane chains. In certain
embodiments, the crosslinker includes electronegative substituents
such as alkylsiloxy or chlorine. In one embodiment, the crosslinker
comprises four Si--H groups that are capable of forming a
connection point between four different vinyl-terminated
polydimethylsiloxane chains. In some embodiments, the crosslinker
is tetrakis(dimethylsiloxy)silane, shown below in (III).
##STR00009##
In other embodiments, the crosslinker is
methyltris(dimethylsiloxy)silane. Other crosslinkers may also be
used. Using higher functional crosslinkers is also possible, but
these form less defined polymer structures.
Chain Extender
[0052] In addition to the crosslinker, the Si--H end group may be
provided by a chain extender, wherein both ends of the chain
extender compound are terminated with a Si--H group.
[0053] In certain embodiments, the chain extender comprises
reactive groups that are compatible and are willing to react with
the vinyl groups in the base polymer. Just as for the crosslinker,
these groups are Si--H groups that can react in a hydrosilation
reaction. The chain extender typically includes two functional
groups; however, the chain extender may include three of more
functional groups, such that the chain extender functions as a
branching agent. The functional groups may be the same as or
different from each other. The functional groups may also be the
same as or different than the functional groups of the first
component and/or the second component.
[0054] The chain extender may be any chain extender known in the
art. In one embodiment, the chain extender is a hydride containing
polydimethylsiloxane. In another embodiment, the chain extender is
a hydride terminated polydimethylsiloxane, shown below in (IV).
##STR00010##
[0055] In a further embodiment, the chain extender is a hydride
terminated polyphenylmethylsiloxane. In another embodiment, the
chain extender is a hydride terminated polydiphenylsiloxane. In yet
another embodiment, the chain extender is a dihydride containing
siloxane. The chain extender may have a high molecular weight or a
low molecular weight. The chain extender may also be branched or
unbranched. In other embodiments, the chain extender is a high
molecular weight polydimethylsiloxane. In other embodiments, the
chain extender is a low molecular weight polydimethylsiloxane.
[0056] In other embodiments, the chain extender is a
functionally-terminated silicone such as a silanol terminated,
vinyl terminated, and amino terminated polydimethylsiloxane. Such
silicones have low tear strength and can be toughened by
incorporating fumed silica (SiO2) into the structure. For example,
an alkoxy-functionalized siloxane can be included. Suitable
alkoxy-functionalized siloxanes include polydiethoxysiloxane,
tetraethoxy silane, tetramethoxy silane, and polydimethoxy
siloxane. In other embodiments, the chain extender is a
fluorosilicone, phenyl silicone, or a branching diethyl
silicone.
[0057] In certain embodiments, by making use of the chain extender
molecule, the V-PDMS base polymer can be shorter because the H-PDMS
chain extender will extend the V-PDMS base polymer chain in situ
between two crosslinker compounds. By using this mechanism, a
V-PDMS chain of a shorter length can be applied which leads to
lower viscosities and compounds that are easier to work with.
Therefore, lower viscosity base polymer compounds can be used
unlike a peroxide activated cure reaction mechanism.
MFHC and H/V Ratios
[0058] The amounts of crosslinker and chain extender that provide
the hydride component may be varied. In certain embodiments, the
amount of hydride in the gel is defined in terms of the mole
fraction of hydride present as crosslinker ("MFHC"). For example,
when the MFHC value is 0.3 or 30%, this means that 30% of the
hydrides present in the system are part of the crosslinker and the
remaining 70% of the hydrides are provided by the chain extender.
In certain embodiments, the MFHC ratio may be altered to adjust the
hardness of the gel (i.e., an increase in the MFHC may increase the
hardness).
[0059] The overall amount of hydride components in the gel can also
vary. The ratio of hydride to vinyl components (provided by the
base polymer) can be defined as "HA/". In other words, H/V is the
total moles of hydride (contributions from crosslinker and chain
extender) divided by the amount in moles of vinyl from the base
polymer (e.g., V-PDMS) present.
[0060] A schematic overview of the reaction is depicted in (V)
below, wherein the crosslinker compounds are represented by "+",
the chain extender compounds are represented by "=", and the base
polymer V-PDMS compounds are represented by "-". In certain
embodiments, the chain extender must always connect two different
base polymer compounds, or connect to one base polymer and
terminate the chain on the opposite end.
##STR00011##
Catalyst
[0061] In certain embodiments, an addition cure catalyst is used in
reacting the base polymer, crosslinker, and chain extender.
Performing the reaction without using a catalyst is typically a
very energy consuming process. Temperatures of 300.degree. C. or
even higher are needed in order to avoid the produced gel having
poor and inconsistent mechanical properties.
[0062] In certain embodiments, the catalyst comprises platinum. For
example, the catalyst can be made of Pt complexed with
divinyltetramethyldisiloxane, shown below in (VI).
##STR00012##
Measurement of Hardness
[0063] Hardness is peak load is as measured by a standard texture
analyzer. For example, a LFRA Texture Analyzer-Brookfield may
include a probe assembly fixed to a motor driven, bi-directional
load cell. In such a system, the probe is driven vertically into
the sample at a pre-set speed and to a pre-set depth. The hardness
is the amount of force (peak load) needed to push the probe into
the test sample.
[0064] Hardness is evaluated with a stainless steel ball diameter
6.35 mm, trigger point: 4 grams, probe speed: 2 mm/sec, target
depth: 4 mm, and hold time: 60 sec.
Measurement of Tack Time and Adhesiveness
[0065] Both tack time and adhesiveness are evaluated with an ALU
probe (diameter 20 mm), trigger load: 4 grams, probe speed: 2
mm/sec, and hold time: 15 sec.
[0066] From the foregoing detailed description, it will be evident
that modifications and variations can be made to the methods and
gels disclosed herein without departing from the spirit or scope of
the disclosure.
* * * * *