U.S. patent application number 15/836357 was filed with the patent office on 2018-06-14 for dynamic seals, compositions, and methods of making the same.
This patent application is currently assigned to Cooper-Standard Automotive Inc.. The applicant listed for this patent is Cooper-Standard Automotive Inc.. Invention is credited to Krishnamachari Gopalan, Roland Herd-Smith, Gending Ji, Robert J. Lenhart.
Application Number | 20180163037 15/836357 |
Document ID | / |
Family ID | 60935970 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180163037 |
Kind Code |
A1 |
Gopalan; Krishnamachari ; et
al. |
June 14, 2018 |
DYNAMIC SEALS, COMPOSITIONS, AND METHODS OF MAKING THE SAME
Abstract
A sponge sealing member is provided that includes a composition
having a silane-crosslinked polyolefin elastomer with a density
less than 0.60 g/cm.sup.3. The sponge sealing member can exhibit a
compression set of from about 5.0% to about 35.0%, as measured
according to ASTM D 395 (22 hrs @ 70.degree. C.). The
silane-crosslinked polyolefin elastomer can also include a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin having a crystallinity less than 40%, a silane
crosslinker, a grafting initiator, a condensation catalyst, and a
foaming agent.
Inventors: |
Gopalan; Krishnamachari;
(Troy, MI) ; Lenhart; Robert J.; (Fort Wayne,
IN) ; Ji; Gending; (Waterloo, CA) ;
Herd-Smith; Roland; (Brignancourt, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cooper-Standard Automotive Inc. |
Novi |
MI |
US |
|
|
Assignee: |
Cooper-Standard Automotive
Inc.
Novi
MI
|
Family ID: |
60935970 |
Appl. No.: |
15/836357 |
Filed: |
December 8, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62497954 |
Dec 10, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 2423/08 20130101;
C09K 3/10 20130101; C08K 3/011 20180101; C08L 23/0815 20130101;
C08F 255/02 20130101; C08F 2500/21 20130101; C08J 2351/06 20130101;
C08J 3/24 20130101; C09K 2200/0494 20130101; C08J 9/0061 20130101;
C08L 23/142 20130101; C08L 23/16 20130101; C08J 2423/12 20130101;
C08K 5/0025 20130101; C09K 2003/1068 20130101; C09K 2200/062
20130101; C08K 3/36 20130101; C08L 23/12 20130101; C08J 9/228
20130101; C08J 2423/14 20130101; C08L 23/14 20130101; C08L 2312/08
20130101; C08L 2205/025 20130101 |
International
Class: |
C08L 23/12 20060101
C08L023/12; C08L 23/08 20060101 C08L023/08; C08K 3/36 20060101
C08K003/36; C08K 3/011 20060101 C08K003/011; C08J 9/228 20060101
C08J009/228 |
Claims
1. A sponge sealing member comprising: a composition comprising a
silane-crosslinked polyolefin elastomer having a density less than
0.60 g/cm.sup.3, wherein the sponge sealing member exhibits a
compression set of from about 5.0% to about 35.0%, as measured
according to ASTM D 395 (22 hrs @ 70.degree. C.).
2. The sponge sealing member of claim 1, wherein the
silane-crosslinked polyolefin elastomer comprises a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin having a percent crystallinity less than 40%, a silane
crosslinker, a grafting initiator, a condensation catalyst, and a
foaming agent.
3. The sponge sealing member of claim 1, wherein the compression
set is from about 15.0% to about 35.0%, as measured according to
ASTM D 395 (22 hrs @ 70.degree. C.).
4. The sponge sealing member of claim 1, wherein the density is
from about 0.50 g/cm.sup.3 to about 0.59 g/cm.sup.3.
5. The sponge sealing member of claim 1, wherein the
silane-crosslinked polyolefin elastomer exhibits a crystallinity of
from about 5% to about 25%.
6. The sponge sealing member of claim 1, wherein the
silane-crosslinked polyolefin elastomer exhibits a glass transition
temperature of from about -75.degree. C. to about -25.degree.
C.
7. The sponge sealing member of claim 1, wherein the composition is
a thermoset, but exhibits thermoplastic properties during
processing.
8. The sponge sealing member of claim 1, wherein the sponge sealing
member exhibits a weathering color difference of from about 0.25
.DELTA.E to about 2.0 .DELTA.E, as measured according to ASTM
D2244.
9. The sponge sealing member of claim 1, further comprising: a
coloring agent.
10. A foamed silane-crosslinked polyolefin blend comprising: a
first polyolefin having a density less than 0.86 g/cm.sup.3; a
second polyolefin having a percent crystallinity less than 40%; a
silane crosslinker; and a foaming agent, wherein the foamed
silane-crosslinked polyolefin blend exhibits a compression set of
from about 5.0% to about 35.0%, as measured according to ASTM D 395
(22 hrs @ 70.degree. C.), and wherein the foamed silane-crosslinked
polyolefin blend has a density less than 0.60 g/cm.sup.3.
11. The foamed silane-crosslinked polyolefin blend of claim 10,
wherein the first polyolefin comprises an ethylene octene copolymer
from about 60 wt % to about 97 wt %.
12. The foamed silane-crosslinked polyolefin blend of claim 10,
wherein the second polyolefin comprises a polypropylene homopolymer
from about 10 wt % to about 35 wt % and/or a
poly(ethylene-co-propylene).
13. The foamed silane-crosslinked polyolefin blend of claim 10,
wherein the silane crosslinker comprises a vinyltrimethoxy silane
from about 1 wt % to about 4 wt %.
14. The foamed silane-crosslinked polyolefin blend of claim 10,
further comprising a non-metal condensation catalyst that comprises
a sulfonic ester from about 1 wt % to about 4 wt %.
15. The foamed silane-crosslinked polyolefin blend of claim 10,
wherein the blend has a density from about 0.85 g/cm.sup.3 to about
0.89 g/cm.sup.3.
16. The foamed silane-crosslinked polyolefin blend of claim 10,
wherein the blend exhibits a crystallinity of from about 5% to
about 25%.
17. The foamed silane-crosslinked polyolefin blend of claim 10,
wherein the blend exhibits a glass transition temperature of from
about -75.degree. C. to about -25.degree. C.
18. A method for making a sponge sealing member, the method
comprising: extruding a first polyolefin having a density less than
0.86 g/cm.sup.3, a second polyolefin having a crystallinity less
than 40%, a silane crosslinker and a grafting initiator together to
form a silane-grafted polyolefin blend; extruding the
silane-grafted polyolefin blend, a condensation catalyst, and a
foaming agent together to form a foamed silane-crosslinkable
polyolefin blend; molding the foamed silane-crosslinkable
polyolefin blend into an uncured sponge sealing element; and
crosslinking the foamed crosslinkable-polyolefin blend of the
uncured sponge sealing element at an ambient temperature and an
ambient humidity to form the element into a sponge sealing member
having a density from about 0.85 g/cm.sup.3 to about 0.89
g/cm.sup.3 comprising a foamed silane-crosslinked polyolefin blend,
wherein the sponge sealing member exhibits a compression set of
from about 5.0% to about 35.0%, as measured according to ASTM D 395
(22 hrs @ 70.degree. C.).
19. The method of claim 18, wherein the silane-grafted polyolefin
blend and the crosslinkable-polyolefin blend are thermoplastics,
and the foamed-silane crosslinked polyolefin blend is a
thermoset.
20. The method of claim 18, wherein the first polyolefin is an
ethylene/.alpha.-olefin copolymer and the second polyolefin is a
polypropylene homopolymer and/or a poly(ethylene-co-propylene).
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Patent Application No. 62/497,954 filed
Dec. 10, 2016, entitled "WEATHERSTRIP, COMPOSITION INCLUDING
SILANE-GRAFTED POLYOLEFIN, AND PROCESS OF MAKING A WEATHERSTRIP,"
which is herein incorporated by reference in its entirety.
FIELD OF THE DISCLOSURE
[0002] The disclosure generally relates to compositions that may be
used to form dynamic seals, and more particularly, to compositions
used to form dynamic seals in vehicles and methods for
manufacturing these compositions and seals.
BACKGROUND OF THE DISCLOSURE
[0003] The motor vehicle industry is continuously manufacturing and
developing sealing elements and sections having low friction and
abrasion resistance properties. These elements and sections can be
extruded from certain polymeric materials. One example of an
extruded abrasion-resistant section is a dynamic seal. Dynamic
seals, such as weatherstrips, are typically employed to seal parts
that are capable of motion relative to one another. In particular,
dynamic seals can be mounted on a vehicle door, and other opening
sections, to provide a seal between the respective portions of the
automobile body to prevent wind noise, water leaks, and particulate
matter from entering the automobile.
[0004] Weatherstrip formulations that make contact with various
sections of automotive glass doors, and/or other sections of an
automotive body traditionally utilize either thermoplastic
vulcanizates (TPV) or ethylene propylene diene monomer (EPDM)
rubber to achieve desired sealing performance. TPVs are relatively
easy to process, but sealing performance can be limited in terms of
resilience or sealing ability over time and material costs tend to
be high. Similarly, EPDM rubber formulations often require many
ingredients (e.g., carbon black, petroleum-based oil, zinc oxide,
miscellaneous fillers such as calcium carbonate or talc, processing
aids, curatives, blowing agents, and many other materials to meet
performance requirements), which tend to increase their material
cost.
[0005] EPDM-based seals are also costly from a process stand point.
The EPDM constituent ingredients are typically mixed together in a
one- or two-step process prior to shipping to an extrusion
facility. At the extrusion facility, the ingredients and rubber
compound(s) are extruded together to form a final material, which
is subsequently formed into automotive glass contacting
weatherstrips. Hence, the extrusion process used to manufacture
weatherstrips can include many stages, depending on the type of
EPDM or other types of resins, and may additionally require long
lengths of curing ovens. For example, extrusion lines of up to 80
yards in length that are powered by natural gas and/or electricity
may be required. Much of the natural gas and/or electricity energy
sources are used to fuel hot air ovens, microwaves, infrared ovens,
or other types of equipment used to vulcanize the EPDM rubber
compounds. The vulcanization process also produces fumes that must
be vented and monitored to comply with environmental requirements.
Overall, the processes used to fabricate these traditional
EPDM-based seals can be very time consuming, costly, and
environmentally unfriendly.
[0006] Mindful of the drawbacks associated with current TPV- and
EPDM-based sealing technologies, the automotive industry has a need
for the development of new compositions and methods for
manufacturing dynamic seals, such as weatherstrips, that are
simpler, lighter in weight, lower in cost, have superior long-term
load loss (LLS) (i.e., ability to seal the glass and window for a
long term), and are more environmentally friendly.
SUMMARY OF THE DISCLOSURE
[0007] According to one aspect of the present disclosure, a sponge
sealing member is disclosed. The sponge sealing member includes a
composition comprising a foamed silane-crosslinked elastomer having
a density less than 0.60 g/cm.sup.3. The sponge sealing member
exhibits a compression set of from about 5.0% to about 35.0%, as
measured according to ASTM D 395 (22 hrs @ 70.degree. C.).
[0008] According to another aspect of the present disclosure, a
silane-crosslinked polyolefin blend is disclosed. The
silane-crosslinked polyolefin blend includes a first polyolefin
having a density less than 0.86 g/cm.sup.3, a second polyolefin
having a percent crystallinity less than 40%, a silane crosslinker,
and a foaming agent. The silane-crosslinked polyolefin blend
exhibits a compression set of from about 5.0% to about 35.0%, as
measured according to ASTM D 395 (22 hrs @ 70.degree. C.). The
silane-crosslinked polyolefin blend has a density less than 0.60
g/cm.sup.3.
[0009] According to a further aspect of the present disclosure, a
method for making a sponge sealing member is disclosed. The method
includes the steps of: extruding a first polyolefin having a
density less than 0.86 g/cm.sup.3, a second polyolefin having a
crystallinity less than 40%, a silane crosslinker, and a grafting
initiator together to form a silane-grafted polyolefin blend;
extruding the silane-grafted polyolefin blend, a condensation
catalyst, and a foaming agent together to form a
silane-crosslinkable polyolefin blend; molding the
silane-crosslinkable polyolefin blend into an uncured sponge
sealing element; and crosslinking the crosslinkable-polyolefin
blend at an ambient temperature and an ambient humidity to form the
element into a sponge sealing member having a density from about
0.50 g/cm.sup.3 to about 0.59 g/cm.sup.3 and comprising a foamed
silane-crosslinked polyolefin blend. The sponge sealing member
exhibits a compression set of from about 5.0% to about 35.0%, as
measured according to ASTM D 395 (22 hrs @ 70.degree. C.).
[0010] These and other aspects, objects, and features of the
present invention will be understood and appreciated by those
skilled in the art upon studying the following specification,
claims, and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In the drawings:
[0012] FIG. 1 is a front perspective view of a vehicle having a
plurality of dynamic seals according to some aspects of the present
disclosure;
[0013] FIG. 2 is a cross-sectional view of a primary weatherstrip
seal according to some aspects of the present disclosure;
[0014] FIG. 3 is a schematic perspective view of a plurality of
dynamic seals used in the vehicle presented in FIG. 1 according to
some aspects of the present disclosure;
[0015] FIGS. 4A-4I are a variety of cross-sectional views of the
representative dynamic seals provided in FIG. 3 according to some
aspects of the present disclosure;
[0016] FIG. 5 is a schematic reaction pathway used to produce a
silane-crosslinked polyolefin elastomer according to some aspects
of the present disclosure;
[0017] FIG. 6 is a flow diagram of a method for making a dynamic
seal with a foamed silane-crosslinked elastomer using a two-step
Sioplas approach according to some aspects of the present
disclosure;
[0018] FIG. 7A is a schematic cross-sectional view a reactive
twin-screw extruder according to some aspects of the present
disclosure;
[0019] FIG. 7B is a schematic cross-sectional view a single-screw
extruder according to some aspects of the present disclosure;
[0020] FIG. 8 is a flow diagram of a method for making a dynamic
seal with a foamed silane-crosslinked elastomer using a one-step
Monosil approach according to some aspects of the present
disclosure;
[0021] FIG. 9 is a schematic cross-sectional view a reactive
single-screw extruder according to some aspects of the present
disclosure;
[0022] FIG. 10 is a graph illustrating the stress/strain behavior
of a dynamic silane-crosslinked elastomer, as compared to the
stress/strain behavior of comparative EPDM compounds; and
[0023] FIG. 11 is a graph illustrating the load versus position
behavior of a dynamic silane-crosslinked elastomer, as compared to
load versus position behavior of comparative EPDM compounds;
and
[0024] FIG. 12 is a set of micrographs of dynamic
silane-crosslinked elastomers, as processed with a supercritical
gas-injected fluid or a chemical foaming agent, according to
aspects of the disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] For purposes of description herein the terms "upper,"
"lower," "right," "left," "rear," "front," "vertical,"
"horizontal," and derivatives thereof shall relate to the dynamic
seals of the disclosure as oriented in the vehicle shown in FIG. 1.
However, it is to be understood that the seals and the methods of
making them outlined in the disclosure may assume various
alternative orientations and step sequences, except where expressly
specified to the contrary. It is also to be understood that the
specific devices and processes illustrated in the attached
drawings, and described in the following specification are simply
exemplary embodiments of the inventive concepts defined in the
appended claims. Hence, specific dimensions and other physical
characteristics relating to the embodiments disclosed herein are
not to be considered as limiting, unless the claims expressly state
otherwise.
[0026] All ranges disclosed herein are inclusive of the recited
endpoint and independently combinable (for example, the range of
"from 2 to 10" is inclusive of the endpoints, 2 and 10, and all the
intermediate values). The endpoints of the ranges and any values
disclosed herein are not limited to the precise range or value;
they are sufficiently imprecise to include values approximating
these ranges and/orvalues.
[0027] A value modified by a term or terms, such as "about" and
"substantially," may not be limited to the precise value specified.
The approximating language may correspond to the precision of an
instrument for measuring the value. The modifier "about" should
also be considered as disclosing the range defined by the absolute
values of the two endpoints. For example, the expression "from
about 2 to about 4" also discloses the range "from 2 to 4."
[0028] As used herein, the term "and/or," when used in a list of
two or more items, means that any one of the listed items can be
employed by itself, or any combination of two or more of the listed
items can be employed. For example, if a composition is described
as containing components A, B, and/or C, the composition can
contain A alone; B alone; C alone; A and B in combination; A and C
in combination; B and C in combination; or A, B, and C in
combination.
[0029] Referring to FIGS. 1-4I, various dynamic sealing members,
synonymously referred to herein as "sponge sealing members," are
provided. In general, the sponge sealing members of the disclosure
include a composition having a foamed silane-crosslinked elastomer
with a density less than 0.90 g/cm.sup.3. The sponge sealing member
can exhibit a compression set of from about 5.0% to about 35.0%
measured according to ASTM D 395 (22 hrs @ 70.degree. C.). The
foamed silane-crosslinked elastomer can be produced from a blend
including a first polyolefin having a density less than 0.86
g/cm.sup.3, a second polyolefin having a crystallinity less than
60.degree. C., a silane crosslinker, a grafting initiator, a
condensation catalyst, and a foaming agent.
[0030] Referring to FIG. 1, a vehicle 10 is depicted with a variety
of dynamic sealing members 12 (e.g., weatherstrip seals). The
vehicle 10 is shown as a sports utility vehicle (SUV) but the type
of vehicle 10 is not meant to be limiting and can include, for
example, a car, minivan, truck, commercial vehicle, or any other
wheeled motorized vehicle. The vehicle 10 and the dynamic sealing
members 12 described herein are for illustrative purposes only and
are not to be construed as limiting to only vehicles 10, for
example, the dynamic sealing members 12 could additionally be used
in the building construction industry, the transportation industry,
the electronics industry, the footwear industry, and the roofing
industry.
[0031] The term "weatherstrip", as used herein, is an example of a
"seal", as also used herein. The term "seal", as used herein, means
a device or substance that is used to join two surfaces together.
The surfaces used herein may include the various types of surfaces
found on, for example, automobiles, structures, windows, roofs,
electronic devices, footwear, and/or any other industry or product
where seals can be used to help minimize and/or eliminate the
transmission of noise, water, or particulate matter through the
respective surfaces.
[0032] The seals used for the various dynamic sealing members 12
(e.g., weatherstrip seal 120 as shown in FIG. 2) disclosed herein
may be fabricated or manufactured from one or more different
silane-crosslinked polyolefin elastomers. In aspects where the
dynamic seal includes more than one type of silane-crosslinked
polyolefin elastomer, the different silane-crosslinked polyolefin
elastomers can each make up one or more different strips, gripping
portions, bodies, pins, sections, and/or surfaces of the dynamic
seal. As noted earlier, dynamic seals are generally used as seals
for configurations in which there is motion between the mating
surfaces being sealed. As used herein, the "dynamic" or "sponge"
silane-crosslinked polyolefin elastomers of the disclosure include
a chemical and/or physical foaming agent and have a density less
than 0.60 g/cm.sup.3 or, more specifically, a density from about
0.50 g/cm.sup.3to about 0.59 g/cm.sup.3. The synthesis and
processing methods used to produce this dynamic silane-crosslinked
polyolefin elastomer and its specialized material properties are
disclosed herein.
[0033] In other aspects, the dynamic sealing member 12 (see FIGS.
1-3) may additionally include one or more portions made from a
micro-dense silane-crosslinked polyolefin elastomer, as typically
used in micro-dense seals. Such dynamic seals, as including
micro-dense silane-crosslinked polyolefin elastomers, are generally
employed in configurations where there is little to moderate motion
between the mating surfaces being sealed. As used herein, a
"micro-dense" silane-crosslinked polyolefin elastomer includes a
microencapsulated foaming agent, and has a density less than 0.70
g/cm.sup.3 or, more specifically, a density from about 0.60
g/cm.sup.3to about 0.69 g/cm.sup.3.
[0034] In other aspects, the dynamic sealing member 12 may
additionally include one or more portions made from a dense
silane-crosslinked polyolefin elastomer, as typically used in
static seals. Such dynamic seals, as including dense
silane-crosslinked polyolefin elastomers, are employed in
configurations that generally have little or no relative motion
between the mating surfaces being sealed. In some aspects, the
static seals are made entirely of a dense silane-crosslinked
polyolefin elastomer. As used herein, a "dense" silane-crosslinked
polyolefin elastomer has a density of less than 0.90
g/cm.sup.3.
[0035] Referring now to FIG. 2, a cross-sectional representation of
the dynamic sealing member 12, in the form of a primary
weatherstrip seal 120, is depicted in cross-sectional form. In
particular, the primary weatherstrip seal 120 may include a
combination of various types of silane-crosslinked polyolefin
elastomers, including a main body member 124 comprising a
micro-dense polyolefin elastomer, a sponge bulb member 128
comprising a sponge polyolefin elastomer, and a retainer pin 132
comprising a dense polyolefin elastomer. The main body member 124
can be secured to the door panel 62 or other portion of the door 14
(see FIG. 2) of the vehicle 10 by any conventional or known means
for doing so, including but not limited to, for example, the
retainer pin 132, though this is not a limiting feature of the
disclosure. As such, any means known in the relevant art for
securing the primary weatherstrip seal 120 to a surface of the
vehicle 10 may be used. The sponge bulb member 128 can provide a
seal between the door 14 and other portions of the vehicle 10, for
example, when the primary weatherstrip seal 120 is brought into
contact and compressed between the two respective surfaces. As will
be appreciated by one skilled in the art, the body of the vehicle
10 and the inner portion of the door 14 represented in FIG. 2 may
be substituted by any two adjoining surfaces that would benefit
from the presence of one or more primary weatherstrip seals 120
impervious to environmental conditions. As such, the body of the
vehicle 10 and the inner portion of the door 14 are merely
representative of adjoining surfaces and are not considered to be
limiting features of the disclosure. Other locations where primary
weatherstrip seals 120 could be applied include, for example, door
panels, body seals, trunk lid seals, door-to-door seals, rocker
seals, and hood seals (e.g., as provided in FIG. 3).
[0036] Referring to FIG. 3 and FIGS. 4A-4H, an isolated exploded
schematic view of a plurality of dynamic sealing members 12 in the
form of various weatherstrip seals (e.g., seals 122, 126, 130, 134,
142, 146, 150 and 154) that can be used in the vehicle 10 (see FIG.
1) is provided. The dynamic sealing members 12 may be configured as
various weatherstrip seals, including those coupled to the
perimeter of the door, such as a secondary door seal 122 (see FIG.
4A) and a primary door seal 126 (see FIG. 4B). The dynamic sealing
member 12 may also be in the form of a rocker seal 130 (see FIG.
4C) used to seal an underbody with a foot well of the vehicle 10
(see FIG. 1). The sealing members 12 can also be in the form of one
or more hood seals 134 (see FIG. 4D) to provide a sponge member
used to better prevent chatter and/or vibrations from being
transmitted across the hood. A pillar margin seal 138 (see FIG. 4E)
may be positioned along a pillar of the vehicle 10 and a headlamp
seal 142 (see FIG. 4F) may be positioned between a headlamp lens
and the vehicle body. A liftgate seal 146 (see FIG. 4G) may be
configured to provide a functional seal used to couple a back hatch
with a flip glass seal 150 (see FIG. 4H) positioned against a
liftable rear glass window. Similarly, pillar margin seal 154 (see
FIG. 4I) may be configured to seal another pillar of the vehicle
10.
[0037] Referring now to FIGS. 4A-4I, a variety of cross-sectional
views of the dynamic sealing members 12 depicted in FIG. 3 are
provided that include: the secondary door seal 122, the primary
door seal 126, the rocker seal 130, the hood seal 134, the pillar
margin seal 138, the headlamp seal 142, and the liftgate seal 146.
The structures of each of the dynamic sealing members 12 may be
varied based on the particular application, e.g., sealing a glass
surface to a portion of the vehicle 10 (see FIG. 1). More
particularly, the various dynamic sealing members 12, as shown in
FIGS. 4A-4I, can include combinations of bodies, legs, lips,
flanges, sections, gripping portions, and edges (as previously
described in connection with FIG. 3), comprising a sponge (or
dynamic) silane-crosslinked polyolefin elastomer, along with
optional dense and micro-dense silane-crosslinked polyolefin
elastomers. In some aspects, the dynamic sealing member 12 may be
extruded around a piece of metal to provide greater structural
stability as shown in outer belt dynamic seal 122, rear pillar
margin seal 138, and first center pillar dynamic seal 146. In some
aspects, the dynamic sealing member 12 may have a flock material
coupled to a surface of the member 12. The term "flock", as used
herein, is defined to mean a light powder, comprised of ground wood
or cotton fiber, used as a coating, extender, and/or filler with
the dynamic silane-crosslinked polyolefin elastomer to provide a
surface having a lower surface energy and/or lower friction
surface.
[0038] More generally, the disclosure focuses on the composition,
method of making the composition, and the corresponding material
properties for the dynamic silane-crosslinked polyolefin elastomer
used to make dynamic seals, e.g., dynamic sealing members 12. The
dynamic sealing member 12 is formed from a silane-grafted
polyolefin where the silane-grafted polyolefin may have a catalyst
added to form a silane-crosslinkable polyolefin elastomer. This
silane-crosslinkable polyolefin may then be crosslinked upon
exposure to moisture and/or heat to form the final dynamic
silane-crosslinked polyolefin elastomer or blend. In aspects, the
dynamic silane-crosslinked polyolefin elastomer or blend includes a
first polyolefin having a density less than 0.90 g/cm.sup.3, a
second polyolefin having a crystallinity of less than 40%, a silane
crosslinker, a graft initiator, and a condensation catalyst.
First Polyolefin
[0039] The first polyolefin can be a polyolefin elastomer including
an olefin block copolymer, an ethylene/.alpha.-olefin copolymer, a
propylene/.alpha.-olefin copolymer, EPDM, EPM, or a mixture of two
or more of any of these materials. Exemplary block copolymers
include those sold under the trade names INFUSE.TM., an olefin
block co-polymer (the Dow Chemical Company) and SEPTON.TM.
V-SERIES, a styrene-ethylene-butylene-styrene block copolymer
(Kuraray Co., LTD.). Exemplary ethylene/.alpha.-olefin copolymers
include those sold under the trade names TAFMER.TM. (e.g., TAFMER
DF710) (Mitsui Chemicals, Inc.), and ENGAGE.TM. (e.g., ENGAGE 8150)
(the Dow Chemical Company). Exemplary propylene/.alpha.-olefin
copolymers include those sold under the trade name VISTAMAXX 6102
grades (Exxon Mobil Chemical Company), TAFMER.TM. XM (Mitsui
Chemical Company), and Versify (Dow Chemical Company). The EPDM may
have a diene content of from about 0.5 to about 10 wt %. The EPM
may have an ethylene content of 45 wt % to 75 wt %.
[0040] The term "comonomer" refers to olefin comonomers which are
suitable for being polymerized with olefin monomers, such as
ethylene or propylene monomers. Comonomers may comprise but are not
limited to aliphatic C.sub.2-C.sub.20 .alpha.-olefins. Examples of
suitable aliphatic C.sub.2-C.sub.20 .alpha.-olefins include
ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene,
1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene,
1-octadecene and 1-eicosene. In an embodiment, the comonomer is
vinyl acetate. The term "copolymer" refers to a polymer, which is
made by linking more than one type of monomer in the same polymer
chain. The term "homopolymer" refers to a polymer which is made by
linking olefin monomers, in the absence of comonomers. The amount
of comonomer can, in some embodiments, be from greater than 0 to
about 12 wt % based on the weight of the polyolefin, including from
greater than 0 to about 9 wt % and from greater than 0 to about 7
wt %. In some embodiments, the comonomer content is greater than
about 2 mol % of the final polymer, including greater than about 3
mol % and greater than about 6 mol %. The comonomer content may be
less than or equal to about 30 mol %. A copolymer can be a random
or block (heterophasic) copolymer. In some embodiments, the
polyolefin is a random copolymer of propylene and ethylene.
[0041] In some aspects, the first polyolefin is selected from the
group consisting of: an olefin homopolymer, a blend of
homopolymers, a copolymer made using two or more olefins, a blend
of copolymers each made using two or more olefins, and a
combination of olefin homopolymers blended with copolymers made
using two or more olefins. The olefin may be selected from
ethylene, propylene, 1-butene, 1-propene, 1-hexene, 1-octene, and
other higher 1-olefin. The first polyolefin may be synthesized
using many different processes (e.g., using gas phase and solution
based using metallocene catalysis and Ziegler-Natta catalysis) and
optionally using a catalyst suitable for polymerizing ethylene
and/or .alpha.-olefins. In some aspects, a metallocene catalyst may
be used to produce low density ethylene/.alpha.-olefin
polymers.
[0042] In some aspects, the polyethylene used for the first
polyolefin can be classified into several types including, but not
limited to, LDPE (Low Density Polyethylene), LLDPE (Linear Low
Density Polyethylene), and HDPE (High Density Polyethylene). In
other aspects, the polyethylene can be classified as Ultra High
Molecular Weight (UHMW), High Molecular Weight (HMW), Medium
Molecular Weight (MMW) and Low Molecular Weight (LMW). In still
other aspects, the polyethylene may be an ultra-low density
ethylene elastomer.
[0043] In some aspects, the first polyolefin may include a
LDPE/silane copolymer or blend. In other aspects, the first
polyolefin may be polyethylene that can be produced using any
catalyst known in the art including, but not limited to, chromium
catalysts, Ziegler-Natta catalysts, metallocene catalysts or
post-metallocene catalysts.
[0044] In some aspects, the first polyolefin may have a molecular
weight distribution M.sub.w/M.sub.n of less than or equal to about
5, less than or equal to about 4, from about 1 to about 3.5, or
from about 1 to about 3.
[0045] The first polyolefin may be present in an amount of from
greater than 0 to about 100 wt % of the composition. In some
embodiments, the amount of polyolefin elastomer is from about 30 to
about 70 wt %. In some aspects, the first polyolefin fed to an
extruder can include from about 50 wt % to about 80 wt % of an
ethylene/.alpha.-olefin copolymer, including from about 60 wt % to
about 75 wt % and from about 62 wt % to about 72 wt %.
[0046] The first polyolefin may have a melt viscosity in the range
of from about 2,000 cP to about 50,000 cP as measured using a
Brookfield viscometer at a temperature of about 177.degree. C. In
some embodiments, the melt viscosity is from about 4,000 cP to
about 40,000 cP, including from about 5,000 cP to about 30,000 cP
and from about 6,000 cP to about 18,000 cP.
[0047] The first polyolefin may have a melt index (T2), measured at
190.degree. C. under a 2.16 kg load, of from about 20.0 g/10 min to
about 3,500 g/10 min, including from about 250 g/10 min to about
1,900 g/10 min and from about 300 g/10 min to about 1,500 g/10 min.
In some aspects, the first polyolefin has a fractional melt index
of from 0.5 g/10 min to about 3,500 g/10 min.
[0048] In some aspects, the density of the first polyolefin is less
than 0.90 g/cm.sup.3, less than about 0.89 g/cm.sup.3, less than
about 0.88 g/cm.sup.3, less than about 0.87 g/cm.sup.3, less than
about 0.86 g/cm.sup.3, less than about 0.85 g/cm.sup.3, less than
about 0.84 g/cm.sup.3, less than about 0.83 g/cm.sup.3, less than
about 0.82 g/cm.sup.3, less than about 0.81 g/cm.sup.3, or less
than about 0.80 g/cm.sup.3. In other aspects, the density of the
first polyolefin may be from about 0.85 g/cm.sup.3to about 0.89
g/cm.sup.3, from about 0.85 g/cm.sup.3to about 0.88 g/cm.sup.3,
from about 0.84 g/cm.sup.3to about 0.88 g/cm.sup.3, or from about
0.83 g/cm.sup.3to about 0.87 g/cm.sup.3. In still other aspects,
the density is at about 0.84 g/cm.sup.3, about 0.85 g/cm.sup.3,
about 0.86 g/cm.sup.3, about 0.87 g/cm.sup.3, about 0.88
g/cm.sup.3, or about 0.89 g/cm.sup.3.
[0049] The percent crystallinity of the first polyolefin may be
less than about 60%, less than about 50%, less than about 40%, less
than about 35%, less than about 30%, less than about 25%, or less
than about 20%. The percent crystallinity may be at least about
10%. In some aspects, the crystallinity is in the range of from
about 2% to about 60%.
Second Polyolefin
[0050] The second polyolefin can be a polyolefin elastomer
including an olefin block copolymer, an ethylene/.alpha.-olefin
copolymer, a propylene/.alpha.-olefin copolymer, EPDM, EPM, or a
mixture of two or more of any of these materials. Exemplary block
copolymers include those sold under the trade names INFUSE.TM. (the
Dow Chemical Company) and SEPTON.TM. V-SERIES (Kuraray Co., LTD.).
Exemplary ethylene/.alpha.-olefin copolymers include those sold
under the trade names TAFMER.TM. (e.g., TAFMER DF710) (Mitsui
Chemicals, Inc.) and ENGAGE.TM. (e.g., ENGAGE 8150) (the Dow
Chemical Company). Exemplary propylene/.alpha.-olefin copolymers
include those sold under the trade name TAFMER.TM. XM grades
(Mitsui Chemical Company) and VISTAMAXX.TM. (e.g., VISTAMAXX 6102)
(Exxon Mobil Chemical Company). The EPDM may have a diene content
of from about 0.5 to about 10 wt %. The EPM may have an ethylene
content of 45 wt % to 75 wt %.
[0051] In some aspects, the second polyolefin is selected from the
group consisting of: an olefin homopolymer, a blend of
homopolymers, a copolymer made using two or more olefins, a blend
of copolymers each made using two or more olefins, and a blend of
olefin homopolymers with copolymers made using two or more olefins.
The olefin may be selected from ethylene, propylene, 1-butene,
1-propene, 1-hexene, 1-octene, and other higher 1-olefin. The first
polyolefin may be synthesized using many different processes (e.g.,
using gas phase and solution based using metallocene catalysis and
Ziegler-Natta catalysis) and optionally using a catalyst suitable
for polymerizing ethylene and/or .alpha.-olefins. In some aspects,
a metallocene catalyst may be used to produce low density
ethylene/.alpha.-olefin polymers.
[0052] In some aspects, the second polyolefin may include a
polypropylene homopolymer, a polypropylene copolymer, a
polyethylene-co-propylene copolymer, or a mixture thereof. Suitable
polypropylenes include but are not limited to polypropylene
obtained by homopolymerization of propylene or copolymerization of
propylene and an alpha-olefin comonomer. In some aspects, the
second polyolefin may have a higher molecular weight and/or a
higher density than the first polyolefin.
[0053] In some embodiments, the second polyolefin may have a
molecular weight distribution M.sub.w/M.sub.n of less than or equal
to about 5, less than or equal to about 4, from about 1 to about
3.5, or from about 1 to about 3.
[0054] The second polyolefin may be present in an amount of from
greater than 0 wt % to about 100 wt % of the composition. In some
embodiments, the amount of polyolefin elastomer is from about 30 wt
% to about 70 wt %. In some embodiments, the second polyolefin fed
to the extruder can include from about 10 wt % to about 50 wt %
polypropylene, from about 20 wt % to about 40 wt % polypropylene,
or from about 25 wt % to about 35 wt % polypropylene. The
polypropylene may be a homopolymer or a copolymer.
[0055] The second polyolefin may have a melt viscosity in the range
of from about 2,000 cP to about 50,000 cP as measured using a
Brookfield viscometer at a temperature of about 177.degree. C. In
some embodiments, the melt viscosity is from about 4,000 cP to
about 40,000 cP, including from about 5,000 cP to about 30,000 cP
and from about 6,000 cP to about 18,000 cP.
[0056] The second polyolefin may have a melt index (T2), measured
at 190.degree. C. under a 2.16 kg load, of from about 20.0 g/10 min
to about 3,500 g/10 min, including from about 250 g/10 min to about
1,900 g/10 min and from about 300 g/10 min to about 1,500 g/10 min.
In some embodiments, the polyolefin has a fractional melt index of
from 0.5 g/10 min to about 3,500 g/10 min.
[0057] In some aspects, the density of the second polyolefin is
less than 0.90 g/cm.sup.3, less than about 0.89 g/cm.sup.3, less
than about 0.88 g/cm.sup.3, less than about 0.87 g/cm.sup.3, less
than about 0.86 g/cm.sup.3, less than about 0.85 g/cm.sup.3, less
than about 0.84 g/cm.sup.3, less than about 0.83 g/cm.sup.3, less
than about 0.82 g/cm.sup.3, less than about 0.81 g/cm.sup.3, or
less than about 0.80 g/cm.sup.3. In other aspects, the density of
the first polyolefin may be from about 0.85 g/cm.sup.3to about 0.89
g/cm.sup.3, from about 0.85 g/cm.sup.3to about 0.88 g/cm.sup.3,
from about 0.84 g/cm.sup.3to about 0.88 g/cm.sup.3, or from about
0.83 g/cm.sup.3to about 0.87 g/cm.sup.3. In still other aspects,
the density is at about 0.84 g/cm.sup.3, about 0.85 g/cm.sup.3,
about 0.86 g/cm.sup.3, about 0.87 g/cm.sup.3, about 0.88
g/cm.sup.3, or about 0.89 g/cm.sup.3.
[0058] The percent crystallinity of the second polyolefin may be
less than about 60%, less than about 50%, less than about 40%, less
than about 35%, less than about 30%, less than about 25%, or less
than about 20%. The percent crystallinity may be at least about
10%. In some aspects, the crystallinity is in the range of from
about 2% to about 60%.
[0059] As noted, the silane-crosslinked polyolefin elastomer or
blend, e.g., as employed in dynamic sealing members 12 (see FIGS.
1-3, 4A-4I), includes both the first polyolefin and the second
polyolefin. The second polyolefin is generally used to modify the
hardness and/or processability of the first polyolefin having a
density less than 0.90 g/cm.sup.3. In some aspects, more than just
the first and second polyolefins may be used to form the
silane-crosslinked polyolefin elastomer or blend. For example, in
some aspects, one, two, three, four, or more different polyolefins
having a density less than 0.90 g/cm.sup.3, less than 0.89
g/cm.sup.3, less than 0.88 g/cm.sup.3, less than 0.87 g/cm.sup.3,
less than 0.86 g/cm.sup.3, or less than 0.85 g/cm.sup.3 may be
substituted and/or used for the first polyolefin. In some aspects,
one, two, three, four, or more different polyolefins,
polyethylene-co-propylene copolymers may be substituted and/or used
for the second polyolefin.
[0060] The blend of the first polyolefin having a density less than
0.90 g/cm.sup.3 and the second polyolefin having a crystallinity
less than 40% is used because the subsequent silane grafting and
crosslinking of these first and second polyolefin materials
together are what form the core resin structure in the final
silane-crosslinked polyolefin elastomer. Although additional
polyolefins may be added to the blend of the silane-grafted,
silane-crosslinkable, and/or silane-crosslinked polyolefin
elastomer as fillers to improve and/or modify the Young's modulus
as desired for the final product, any polyolefins added to the
blend having a crystallinity equal to or greater than 40% are not
chemically or covalently incorporated into the crosslinked
structure of the final silane-crosslinked polyolefin elastomer.
[0061] In some aspects, the first and second polyolefins may
further include one or more TPVs and/or EPDM with or without silane
graft moieties where the TPV and/or EPDM polymers are present in an
amount of up to 20 wt % of the silane-crosslinked polyolefin
elastomer/blend.
Grafting Initiator
[0062] A grafting initiator (also referred to as "a radical
initiator" in the disclosure) can be utilized in the grafting
process of at least the first and second polyolefins by reacting
with the respective polyolefins to form a reactive species that can
react and/or couple with the silane crosslinker molecule. The
grafting initiator can include halogen molecules, azo compounds
(e.g., azobisisobutyl), carboxylic peroxyacids, peroxyesters,
peroxyketals, and peroxides (e.g., alkyl hydroperoxides, dialkyl
peroxides, and diacyl peroxides). In some embodiments, the grafting
initiator is an organic peroxide selected from di-t-butyl peroxide,
t-butyl cumyl peroxide, dicumyl peroxide,
2,5-dimethyl-2,5-di(t-butyl-peroxy)hexyne-3,
1,3-bis(t-butyl-peroxy-isopropyl)benzene,
n-butyl-4,4-bis(t-butyl-peroxy)valerate, benzoyl peroxide,
t-butylperoxybenzoate, t-butylperoxy isopropyl carbonate, and
t-butylperbenzoate, as well as bis(2-methylbenzoyl)peroxide,
bis(4-methylbenzoyl)peroxide, t-butyl peroctoate, cumene
hydroperoxide, methyl ethyl ketone peroxide, lauryl peroxide,
tert-butyl peracetate, di-t-amyl peroxide, t-amyl peroxybenzoate,
1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,
.alpha.,.alpha.'-bis(t-butylperoxy)-1,3-diisopropylbenzene,
.alpha.,.alpha.-bis(t-butylpexoxy)-1,4-diisopropylbenzene,
2,5-bis(t-butylperoxy)-2,5-dimethylhexane, and
2,5-bis(t-butylperoxy)-2,5-dimethyl-3-hexyne and
2,4-dichlorobenzoyl peroxide. Exemplary peroxides include those
sold under the tradename LUPEROX.TM. (available from Arkema,
Inc.).
[0063] In some aspects, the grafting initiator is present in an
amount of from greater than 0 wt % to about 2 wt % of the
composition, including from about 0.15 wt % to about 1.2 wt % of
the composition. The amount of initiator and silane employed may
affect the final structure of the silane grafted polymer (e.g., the
degree of grafting in the grafted polymer and the degree of
crosslinking in the cured polymer). In some aspects, the reactive
composition contains at least 100 ppm of initiator, or at least 300
ppm of initiator. The initiator may be present in an amount from
300 ppm to 1500 ppm, or from 300 ppm to 2000 ppm. The
silane:initiator weight ratio may be from about 20:1 to 400:1,
including from about 30:1 to about 400:1, from about 48:1 to about
350:1, and from about 55:1 to about 333:1.
[0064] The grafting reaction can be performed under conditions that
optimize grafts onto the interpolymer backbone while minimizing
side reactions (e.g., the homopolymerization of the grafting
agent). The grafting reaction may be performed in a melt, in
solution, in a solid-state, and/or in a swollen-state. The
silanation may be performed in a wide-variety of equipment (e.g.,
twin screw extruders, single screw extruders, Brabenders, internal
mixers such as Banbury mixers, and batch reactors). In some
embodiments, the polyolefin, silane, and initiator are mixed in the
first stage of an extruder. The melt temperature (i.e., the
temperature at which the polymer starts melting and starts to flow)
may be from about 120.degree. C. to about 260.degree. C., including
from about 130.degree. C. to about 250.degree. C.
Silane Crosslinker
[0065] A silane crosslinker can be used to covalently graft silane
moieties onto the first and second polyolefins and the silane
crosslinker may include alkoxysilanes, silazanes, siloxanes, or a
combination thereof. The grafting and/or coupling of the various
potential silane crosslinkers or silane crosslinker molecules is
facilitated by the reactive species formed by the grafting
initiator reacting with the respective silane crosslinker.
[0066] In some aspects, the silane crosslinker is a silazane where
the silazane may include, for example, hexamethyldisilazane (HMDS)
or Bis(trimethylsilyl)amine. In some aspects, the silane
crosslinker is a siloxane where the siloxane may include, for
example, polydimethylsiloxane (PDMS) and
octamethylcyclotetrasiloxane.
[0067] In some aspects, the silane crosslinker is an alkoxysilane.
As used herein, the term "alkoxysilane" refers to a compound that
comprises a silicon atom, at least one alkoxy group and at least
one other organic group, wherein the silicon atom is bonded with
the organic group by a covalent bond. Preferably, the alkoxysilane
is selected from alkylsilanes; acryl-based silanes; vinyl-based
silanes; aromatic silanes; epoxy-based silanes; amino-based silanes
and amines that possess --NH.sub.2, --NHCH.sub.3or
--N(CH.sub.3).sub.2; ureide-based silanes; mercapto-based silanes;
and alkoxysilanes which have a hydroxyl group (i.e., --OH). An
acryl-based silane may be selected from the group comprising
beta-acryloxyethyl trimethoxysilane; beta-acryloxy propyl
trimethoxysilane; gamma-acryloxyethyl trimethoxysilane;
gamma-acryloxypropyl trimethoxysilane; beta-acryloxyethyl
triethoxysilane; beta-acryloxypropyl triethoxysilane;
gamma-acryloxyethyl triethoxysilane; gamma-acryloxypropyl
triethoxysilane; beta-methacryloxyethyl trimethoxysilane;
beta-methacryloxypropyl trimethoxysilane; gamma-methacryloxyethyl
trimethoxysilane; gamma-methacryloxypropyl trimethoxysilane;
beta-methacryloxyethyl triethoxysilane; beta-methacryloxypropyl
triethoxysilane; gamma-methacryloxyethyl triethoxysilane;
gamma-methacryloxypropyl triethoxysilane;
3-methacryloxypropylmethyl diethoxysilane. A vinyl-based silane may
be selected from the group comprising vinyl trimethoxysilane; vinyl
triethoxysilane; p-styryl trimethoxysilane,
methylvinyldimethoxysilane, vinyldimethylmethoxysilane,
divinyldimethoxysilane, vinyltris(2-methoxyethoxy)silane, and
vinylbenzylethylenediaminopropyltrimethoxysilane. An aromatic
silane may be selected from phenyltrimethoxysilane and
phenyltriethoxysilane. An epoxy-based silane may be selected from
the group comprising 3-glycydoxypropyl trimethoxysilane;
3-glycydoxypropylmethyl diethoxysilane; 3-glycydoxypropyl
triethoxysilane; 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, and
glycidyloxypropylmethyldimethoxysilane. An amino-based silane may
be selected from the group comprising 3-aminopropyl
triethoxysilane; 3-aminopropyl trimethoxysilane;
3-aminopropyldimethyl ethoxysilane;
3-aminopropylmethyldiethoxysilane; 4-aminobutyltriethoxysilane;
3-aminopropyldiisopropyl ethoxysilane;
1-amino-2-(dimethylethoxysilyl)propane;
(aminoethylamino)-3-isobutyldimethyl methoxysilane;
N-(2-aminoethyl)-3-aminoisobutylmethyl dimethoxysilane;
(aminoethylaminomethyl)phenetyl trimethoxysilane;
N-(2-aminoethyl)-3-aminopropylmethyl dimethoxysilane;
N-(2-aminoethyl)-3-aminopropyl trimethoxysilane;
N-(2-aminoethyl)-3-aminopropyl triethoxysilane;
N-(6-aminohexyl)aminomethyl trimethoxysilane;
N-(6-aminohexyl)aminomethyl trimethoxysilane;
N-(6-aminohexyl)aminopropyl trimethoxysilane;
N-(2-aminoethyl)-1,1-aminoundecyl trimethoxysilane;
1,1-aminoundecyl triethoxysilane; 3-(m-aminophenoxy)propyl
trimethoxysilane; m-aminophenyl trimethoxysilane; p-aminophenyl
trimethoxysilane; (3-trimethoxysilylpropyl)diethylenetriamine;
N-methylaminopropylmethyl dimethoxysilane; N-methylaminopropyl
trimethoxysilane; dimethylaminomethyl ethoxysilane;
(N,N-dimethylaminopropyl)trimethoxysilane;
(N-acetylglycysil)-3-aminopropyl trimethoxysilane,
N-phenyl-3-aminopropyltrimethoxysilane,
N-phenyl-3-aminopropyltriethoxysilane,
phenylaminopropyltrimethoxysilane,
aminoethylaminopropyltrimethoxysilane, and
aminoethylaminopropylmethyldimethoxysilane. An ureide-based silane
may be 3-ureidepropyl triethoxysilane. A mercapto-based silane may
be selected from the group comprising 3-mercaptopropylmethyl
dimethoxysilane, 3-mercaptopropyl trimethoxysilane, and
3-mercaptopropyl triethoxysilane. An alkoxysilane having a hydroxyl
group may be selected from the group comprising hydroxymethyl
triethoxysilane; N-(hydroxyethyl)-N-methylaminopropyl
trimethoxysilane; bis(2-hydroxyethyl)-3-aminopropyl
triethoxysilane; N-(3-triethoxysilylpropyl)-4-hydroxy butylamide;
1,1-(triethoxysilyl)undecanol; triethoxysilyl undecanol; ethylene
glycol acetal; and N-(3-ethoxysilylpropyl)gluconamide.
[0068] In some aspects, the alkylsilane may be expressed with a
general formula: R.sub.nSi(OR').sub.4-n wherein: n is 1, 2 or 3; R
is a C.sub.1-20 alkyl ora C.sub.2-20 alkenyl; and R' is an
C.sub.1-20 alkyl. The term "alkyl" by itself or as part of another
substituent, refers to a straight, branched or cyclic saturated
hydrocarbon group joined by single carbon-carbon bonds having 1 to
20 carbon atoms, for example 1 to 10 carbon atoms, for example 1 to
8 carbon atoms, preferably 1 to 6 carbon atoms. When a subscript is
used herein following a carbon atom, the subscript refers to the
number of carbon atoms that the named group may contain. Thus, for
example, C.sub.1-6 alkyl means an alkyl of one to six carbon atoms.
Examples of alkyl groups are methyl, ethyl, propyl, isopropyl,
butyl, isobutyl, sec-butyl, f-butyl, 2-methylbutyl, pentyl,
iso-amyl and its isomers, hexyl and its isomers, heptyl and its
isomers, octyl and its isomer, decyl and its isomer, dodecyl and
its isomers. The term "C.sub.2-20 alkenyl" by itself or as part of
another substituent, refers to an unsaturated hydrocarbyl group,
which may be linear, or branched, comprising one or more
carbon-carbon double bonds having 2 to 20 carbon atoms. Examples of
C2-6 alkenyl groups are ethenyl, 2-propenyl, 2-butenyl, 3-butenyl,
2-pentenyl and its isomers, 2-hexenyl and its isomers,
2,4-pentadienyl and the like.
[0069] In some aspects, the alkylsilane may be selected from the
group comprising methyltrimethoxysilane; methyltriethoxysilane;
ethyltrimethoxysilane; ethyltriethoxysilane;
propyltrimethoxysilane; propyltriethoxysilane;
hexyltrimethoxysilane; hexyltriethoxysilane; octyltrimethoxysilane;
octyltriethoxysilane; decyltrimethoxysilane; decyltriethoxysilane;
dodecyltrimethoxysilane: dodecyltriethoxysilane;
tridecyltrimethoxysilane; dodecyltriethoxysilane;
hexadecyltrimethoxysilane; hexadecyltriethoxysilane;
octadecyltrimethoxysilane; octadecyltriethoxysilane,
trimethylmethoxysilane, methylhydrodimethoxysilane,
dimethyldimethoxysilane, diisopropyldimethoxysilane,
diisobutyldimethoxysilane, isobutyltrimethoxysilane,
n-butyltrimethoxysilane, n-butylmethyldimethoxysilane,
phenyltrimethoxysilane, phenyltrimethoxysilane,
phenylmethyldimethoxysilane, triphenylsilanol,
n-hexyltrimethoxysilane, n-octyltrimethoxysilane,
isooctyltrimethoxysilane, decyltrimethoxysilane,
hexadecyltrimethoxysilane, cyclohexylmethyldimethoxysilane,
cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane,
tert-butylethyldimethoxysilane, tert-butylpropyldimethoxysilane,
dicyclohexyldimethoxysilane, and a combination thereof.
[0070] In some aspects, the alkylsilane compound may be selected
from triethoxyoctylsilane, trimethoxyoctylsilane, and a combination
thereof.
[0071] Additional examples of silanes that can be used as silane
crosslinkers include, but are not limited to, those of the general
formula
CH.sub.2.dbd.CR--(COO).sub.x(C.sub.nH.sub.2n).sub.ySiR'.sub.3,
wherein R is a hydrogen atom or methyl group; x is 0 or 1; y is 0
or 1; n is an integer from 1 to 12; each R' can be an organic group
and may be independently selected from an alkoxy group having from
1 to 12 carbon atoms (e.g., methoxy, ethoxy, butoxy), aryloxy group
(e.g., phenoxy), araloxy group (e.g., benzyloxy), aliphatic acyloxy
group having from 1 to 12 carbon atoms (e.g., formyloxy, acetyloxy,
propanoyloxy), amino or substituted amino groups (e.g., alkylamino,
arylamino), or a lower alkyl group having 1 to 6 carbon atoms. x
and y may both equal 1. In some aspects, no more than one of the
three R' groups is an alkyl. In other aspects, not more than two of
the three R' groups is an alkyl.
[0072] Any silane or mixture of silanes known in the art that can
effectively graft to and crosslink an olefin polymer can be used in
the practice of the present disclosure. In some aspects, the silane
crosslinker can include, but is not limited to, unsaturated silanes
which include an ethylenically unsaturated hydrocarbyl group (e.g.,
a vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or a
gamma-(meth)acryloxy allyl group) and a hydrolyzable group (e.g., a
hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group).
Non-limiting examples of hydrolyzable groups include, but are not
limited to, methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, and
alkyl, or arylamino groups. In other aspects, the silane
crosslinkers are unsaturated alkoxy silanes which can be grafted
onto the polymer. In still other aspects, additional exemplary
silane crosslinkers include vinyltrimethoxysilane,
vinyltriethoxysilane, 3-(trimethoxysilyl)propyl methacrylate
gamma-(meth)acryloxypropyl trimethoxysilane), and mixtures
thereof.
[0073] The silane crosslinker may be present in the silane-grafted
polyolefin elastomer in an amount of from greater than 0 wt % to
about 10 wt %, including from about 0.5 wt % to about 5 wt %. The
amount of silane crosslinker may be varied based on the nature of
the olefin polymer, the silane itself, the processing conditions,
the grafting efficiency, the application, and other factors. The
amount of silane crosslinker may be at least 2 wt %, including at
least 4 wt % or at least 5 wt %, based on the weight of the
reactive composition. In other aspects, the amount of silane
crosslinker may be at least 10 wt %, based on the weight of the
reactive composition. In still other aspects, the silane
crosslinker content is at least 1% based on the weight of the
reactive composition. In some embodiments, the silane crosslinker
fed to the extruder may include from about 0.5 wt % to about 10 wt
% of silane monomer, from about 1 wt % to about 5 wt % silane
monomer, or from about 2 wt % to about 4 wt % silane monomer.
Condensation Catalyst
[0074] A condensation catalyst can facilitate both the hydrolysis
and subsequent condensation of the silane grafts on the
silane-grafted polyolefin elastomer to form crosslinks. In some
aspects, the crosslinking can be aided by the use of an electron
beam radiation. In some aspects, the condensation catalyst can
include, for example, organic bases, carboxylic acids, and
organometallic compounds (e.g., organic titanates and complexes or
carboxylates of lead, cobalt, iron, nickel, zinc, and tin). In
other aspects, the condensation catalyst can include fatty acids
and metal complex compounds such as metal carboxylates; aluminum
triacetyl acetonate, iron triacetyl acetonate, manganese
tetraacetyl acetonate, nickel tetraacetyl acetonate, chromium
hexaacetyl acetonate, titanium tetraacetyl acetonate and cobalt
tetraacetyl acetonate; metal alkoxides such as aluminum ethoxide,
aluminum propoxide, aluminum butoxide, titanium ethoxide, titanium
propoxide and titanium butoxide; metal salt compounds such as
sodium acetate, tin octylate, lead octylate, cobalt octylate, zinc
octylate, calcium octylate, lead naphthenate, cobalt naphthenate,
dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin maleate and
dibutyltin di(2-ethylhexanoate); acidic compounds such as formic
acid, acetic acid, propionic acid, p-toluenesulfonic acid,
trichloroacetic acid, phosphoric acid, monoalkylphosphoric acid,
dialkylphosphoric acid, phosphate ester of p-hydroxyethyl
(meth)acrylate, monoalkylphosphorous acid and dialkylphosphorous
acid; acids such as p-toluenesulfonic acid, phthalic anhydride,
benzoic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid,
formic acid, acetic acid, itaconic acid, oxalic acid and maleic
acid, ammonium salts, lower amine salts or polyvalent metal salts
of these acids, sodium hydroxide, lithium chloride; organometal
compounds such as diethyl zinc and tetra(n-butoxy)titanium; and
amines such as dicyclohexylamine, triethylamine,
N,N-dimethylbenzylamine, N,N,N',N'-tetramethyl-1,3-butanediamine,
diethanolamine, triethanolamine and cyclohexylethylamine. In still
other aspects, the condensation catalyst can include
ibutyltindilaurate, dioctyltinmaleate, dibutyltindiacetate,
dibutyltindioctoate, stannous acetate, stannous octoate, lead
naphthenate, zinc caprylate, and cobalt naphthenate. Depending on
the desired final material properties of the silane-crosslinked
polyolefin elastomer or blend, a single condensation catalyst or a
mixture of condensation catalysts may be utilized. The condensation
catalyst(s) may be present in an amount of from about 0.01 wt % to
about 1.0 wt 5, including from about 0.25 wt % to about 8 wt %,
based on the total weight of the silane-grafted polyolefin
elastomer/blend composition.
[0075] In some aspects, a crosslinking system can include and use
one or all of a combination of radiation, heat, moisture, and
additional condensation catalyst. In some aspects, the condensation
catalyst may be present in an amount of from 0.25 wt % to 8 wt %.
In other aspects, the condensation catalyst may be included in an
amount of from about 1 wt % to about 10 wt %, or from about 2 wt %
to about 5 wt %.
Foaming Agent
[0076] The foaming agent can be a chemical foaming agent (e.g.,
organic or inorganic foaming agent) and/or a physical foaming
(e.g., gases and volatile low weight molecules) that is added to
the silane-grafted polyolefin elastomer and condensation catalyst
blend during the extrusion and/or molding process to produce the
foamed or sponge silane-crosslinked polyolefin elastomer.
[0077] In some aspects, an endothermic blowing (foaming) agent may
be used that can include, for example, sodium bicarbonate and/or
citric acid and its salts or derivatives. Exemplary citric acid
foaming agents include those sold under the trade name
HYDROCEROL.RTM. that includes a mixture of zinc stearate,
polyethylene glycol, and a citric acid or citric acid derivative.
The desired decomposition temperature for the endothermic blowing
(foaming) agent may be from about 160.degree. C. to about
200.degree. C., or about 175.degree. C., about 180.degree. C.,
about 185.degree. C., about 190.degree. C., or about 195.degree.
C.
[0078] Organic foaming agents that may be used can include, for
example, azo compounds, such as azodicarbonamide (ADCA), barium
azodicarboxylate, azobisisobutyronitrile (AIBN),
azocyclohexylnitrile, and azodiaminobenzene, N-nitroso compounds,
such as N,N'-dinitrosopentamethylenetetramine (DPT),
N,N'-dimethyl-N,N'-dinitrosoterephthalamide, and
trinitrosotrimethyltriamine, hydrazide compounds, such as
4,4'-oxybis(benzenesulfonylhydrazide)(OBSH), paratoluene
sulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide,
2,4-toluenedisulfonylhydrazide,
p,p-bis(benzenesulfonylhydrazide)ether,
benzene-1,3-disulfonylhydrazide, and allylbis(sulfonylhydrazide),
semicarbazide compounds, such as p-toluilenesulfonylsemicarbazide,
and 4,4'-oxybis(benzenesulfonylsemicarbazide), alkane fluorides,
such as trichloromonofluoromethane, and dichloromonofluoromethane,
and triazole compounds, such as 5-morpholyl-1,2,3,4-thiatriazole,
and other known organic foaming agents. Preferably, azo compounds
and N-nitroso compounds are used. Further preferably,
azodicarbonamide (ADCA) and N,N'-dinitrosopentamethylenetetramine
(DPT) are used. The organic foaming agents listed above may be used
alone or in any combination of two or more.
[0079] The decomposition temperature and amount of organic foaming
agent used can have important consequences on the density and
material properties of the foamed silane-crosslinked polyolefin
elastomer. In some aspects, the organic foaming agent has a
decomposition temperature of from about 150.degree. C. to about
210.degree. C. The organic foaming agent can be used in an amount
of from about 0.1 wt % to about 40 wt %, from about 5 wt % to about
30 wt %, from about 5 wt % to about 20 wt %, from about 10 wt % to
about 30 wt %, or from about 1 wt % to about 10 wt % based on the
total weight of the polymer blend. If the organic foaming agent has
a decomposition temperature lower than 150.degree. C., early
foaming may occur during compounding. Meanwhile, if the organic
foaming agent has a decomposition temperature higher than
210.degree. C., it may take longer, e.g., greater than 15 minutes,
to mold the foam, resulting in low productivity. Additional foaming
agents may include any compound whose decomposition temperature is
within the range defined above.
[0080] The inorganic foaming agents that may be used include, for
example, hydrogen carbonate, such as sodium hydrogen carbonate, and
ammonium hydrogen carbonate, carbonate, such as sodium carbonate,
and ammonium carbonate, nitrite, such as sodium nitrite, and
ammonium nitrite, borohydride, such as sodium borohydride, and
other known inorganic foaming agents, such as azides. In some
aspect, hydrogen carbonate may be used. In other aspects, sodium
hydrogen carbonate may be used. The inorganic foaming agents listed
above may be used alone or in any combination of two or more. The
inorganic foaming agent can be used in an amount of from about 0.1
wt % to about 40 wt %, from about 5 wt % to about 30 wt %, from
about 5 wt % to about 20 wt %, from about 10 wt % to about 30 wt %,
or from about 1 wt % to about 10 wt % based on the total weight of
the polymer blend.
[0081] Physical blowing agents that may be used include, for
example, supercritical carbon dioxide, supercritical nitrogen,
butane, pentane, isopentane, cyclopentane. In some aspects, various
minerals or inorganic compounds (e.g., talc) may be used as a
nucleating agent for the supercritical fluid. The physical foaming
agent can be used in an amount of from about 0.1 wt % to about 40
wt %, from about 5 wt % to about 30 wt %, from about 5 wt % to
about 20 wt %, from about 10 wt % to about 30 wt %, or from about 1
wt % to about 10 wt % based the total weight of the polymer
blend.
Optional Additional Components
[0082] The silane-crosslinked polyolefin elastomer may optionally
include one or more fillers. The filler(s) may be extruded with the
silane-grafted polyolefin and in some aspects may include
additional polyolefins having a crystallinity greater than 20%,
greater than 30%, greater than 40%, or greater than 50%. In some
aspects, the filler(s) may include metal oxides, metal hydroxides,
metal carbonates, metal sulfates, metal silicates, clays, talcs,
carbon black, and silicas. Depending on the application and/or
desired properties, these materials may be fumed or calcined.
[0083] With further regard to the filler(s), the metal of the metal
oxide, metal hydroxide, metal carbonate, metal sulfate, or metal
silicate may be selected from alkali metals (e.g., lithium, sodium,
potassium, rubidium, caesium, and francium); alkaline earth metals
(e.g., beryllium, magnesium, calcium, strontium, barium, and
radium); transition metals (e.g., zinc, molybdenum, cadmium,
scandium, titanium, vanadium, chromium, manganese, iron, cobalt,
nickel, copper, yttrium, zirconium, niobium, technetium,
ruthernium, rhodium, palladium, silver, hafnium, taltalum,
tungsten, rhenium, osmium, indium, platinum, gold, mercury,
rutherfordium, dubnium, seaborgium, bohrium, hassium, and
copernicium); post-transition metals (e.g., aluminum, gallium,
indium, tin, thallium, lead, bismuth, and polonium); lanthanides
(e.g., lanthanum, cerium, praseodymium, neodymium, promethium,
samarium, europium, gadolinium, terbium, dysprosium, holmium,
erbium, thulium, ytterbium, and lutetium); actinides (e.g.,
actinium, thorium, protactinium, uranium, neptunium, plutonium,
americium, curium, berkelium, californium, einsteinium, fermium,
mendelevium, nobelium, and lawrencium); germanium; arsenic;
antimony; and astatine.
[0084] The filler(s) of the sponge silane-crosslinked polyolefin
elastomer or blend may be present in an amount of from greater than
0 wt % to about 50 wt %, including from about 1 wt % to about 20 wt
% and from about 3 wt % to about 10 wt %.
[0085] The sponge silane-crosslinked polyolefin elastomer and/or
the respective articles formed (e.g., dynamic sealing members 12)
may also include waxes (e.g., paraffin waxes, microcrystalline
waxes, HDPE waxes, LDPE waxes, thermally degraded waxes, byproduct
polyethylene waxes, optionally oxidized Fischer-Tropsch waxes, and
functionalized waxes). In some embodiments, the wax(es) are present
in an amount of from about 0 wt % to about 10 wt %.
[0086] In some aspects, the silane-crosslinked polyolefin elastomer
may include one or more filler polyolefins having a crystallinity
greater than 20%, greater than 30%, greater than 40%, or greater
than 50%. The filler polyolefin may include polypropylene,
poly(ethylene-co-propylene), and/or other ethylene/.alpha.-olefin
copolymers. In some aspects, the use of the filler polyolefin may
be present in an amount of from about 5 wt % to about 60 wt %, from
about 10 wt % to about 50 wt %, from about 20 wt % to about 40 wt
%, or from about 5 wt % to about 20 wt %. The addition of the
filler to the polyolefin may increase the Young's modulus by at
least 10%, by at least 25%, or by at least 50% for the final
silane-crosslinked polyolefin elastomer.
[0087] Tackifying resins (e.g., aliphatic hydrocarbons, aromatic
hydrocarbons, modified hydrocarbons, terpens, modified terpenes,
hydrogenated terpenes, rosins, rosin derivatives, hydrogenated
rosins, and mixtures thereof) may also be included in the
silane-crosslinked polyolefin elastomer/blend. The tackifying
resins may have a ring and ball softening point in the range of
from 70.degree. C. to about 150.degree. C. and a viscosity of less
than about 3,000 cP at 177.degree. C. In some aspects, the
tackifying resin(s) are present in an amount of from about 0 wt %
to about 10 wt %.
[0088] In some aspects, the silane-crosslinked polyolefin elastomer
may include one or more oils. Non-limiting types of oils include
white mineral oils and naphthenic oils. In some embodiments, the
oil(s) are present in an amount of from about 0 wt % to about 10 wt
%.
[0089] In some aspects, the silane-crosslinked polyolefin elastomer
of the present disclosure may include one or more stabilizers
(e.g., antioxidants). The sponge silane-crosslinked elastomer may
be treated before grafting, after grafting, before crosslinking,
and/or after crosslinking. Other additives may also be included.
Non-limiting examples of additives include antistatic agents, dyes,
pigments, UV light absorbers, nucleating agents, fillers, slip
agents, plasticizers, fire retardants, lubricants, processing
aides, smoke inhibitors, anti-blocking agents, and viscosity
control agents. The antioxidant(s) may be present in an amount of
less than 0.5 wt %, including less than 0.2 wt % of the
composition.
Method for Making the Silane-Grafted Polyolefin Elastomer
[0090] The synthesis/production of the dynamic or foamed
silane-crosslinked polyolefin elastomer may be performed by
combining the respective components in one extruder using a
single-step Monosil process or in two extruders using a two-step
Sioplas process which eliminates the need for additional steps of
mixing and shipping rubber compounds prior to extrusion.
[0091] Referring now to FIG. 5, the general chemical process used
during both the single-step Monosil process and two-step Sioplas
process used to synthesize the dynamic silane-crosslinked
polyolefinelastomer is provided. The process starts with a grafting
step that includes initiation from a grafting initiator followed by
propagation and chain transfer with the first and second
polyolefins. The grafting initiator, in some aspects a peroxide or
azo compound, homolytically cleaves to form two radical initiator
fragments that transfer to one of the first and second polyolefins
chains through a propagation step. The free radical, now positioned
on the first or second polyolefin chain, can then transfer to a
silane molecule and/or another polyolefin chain. Once the initiator
and free radicals are consumed, the silane grafting reaction for
the first and second polyolefins is complete.
[0092] Still referring to FIG. 5, once the silane grafting reaction
is complete, a mixture of stable first and second silane-grafted
polyolefins is produced. A crosslinking catalyst may then be added
to the first and second silane-grafted polyolefins to form the
silane-grafted polyolefin elastomer. The crosslinking catalyst may
first facilitate the hydrolysis of the silyl group grafted onto the
polyolefin backbones to form reactive silanol groups. The silanol
groups may then react with other silanol groups on other polyolefin
molecules to form a crosslinked network of elastomeric polyolefin
polymer chains linked together through siloxane linkages. The
density of silane crosslinks throughout the silane-grafted
polyolefin elastomer can influence the material properties
exhibited by the elastomer.
[0093] Referring now to FIGS. 6 and 7A, a method 300 for making a
dynamic seal, such as the dynamic sealing member 12, using the
two-step Sioplas process is shown. The method 300 may begin with a
step 304 that includes extruding (e.g., with a twin screw extruder
182) the first polyolefin 170 having a density less than 0.86
g/cm.sup.3, the second polyolefin 174, and a silan cocktail 178
including the silane crosslinker (e.g., vinyltrimethoxy silane,
VTMO) and the grafting initiator (e.g. dicumyl peroxide) together
to form a silane-grafted polyolefin blend. The first polyolefin 170
and second polyolefin 174 may be added to a reactive twin screw
extruder 182 using an addition hopper 186. The silan cocktail 178
may be added to the twin screws 190 further down the extrusion line
to help promote better mixing with the first and second polyolefin
170, 174 blend. A forced volatile organic compound (VOC) vacuum 194
may be used on the reactive twin screw extruder 182 to help
maintain a desired reaction pressure. The twin screw extruder 182
is considered reactive because the radical initiator and silane
crosslinker are reacting with and forming new covalent bonds with
both the first and second polyolefins 170, 174. The melted
silane-grafted polyolefin blend can exit the reactive twin screw
extruder 182 using a gear pump 198 that injects the molten
silane-grafted polyolefin blend into a water pelletizer 202 that
can form a pelletized silane-grafted polyolefin blend 206. In some
aspects, the molten silane-grafted polyolefin blend may be extruded
into pellets, pillows, or any other configuration prior to the
incorporation of the condensation catalyst 210 (see FIG. 7B) and
formation of the final article.
[0094] The reactive twin screw extruder 182 can be configured to
have a plurality of different temperature zones (e.g., Z0-Z12 as
shown in FIG. 7A) that extend for various lengths of the twin screw
extruder 182. In some aspects, the respective temperature zones may
have temperatures ranging from about room temperature to about
180.degree. C., from about 120.degree. C. to about 170.degree. C.,
from about 120.degree. C. to about 160.degree. C., from about
120.degree. C. to about 150.degree. C., from about 120.degree. C.
to about 140.degree. C., from about 120.degree. C. to about
130.degree. C., from about 130.degree. C. to about 170.degree. C.,
from about 130.degree. C. to about 160.degree. C., from about
130.degree. C. to about 150.degree. C., from about 130.degree. C.
to about 140.degree. C., from about 140.degree. C. to about
170.degree. C., from about 140.degree. C. to about 160.degree. C.,
from about 140.degree. C. to about 150.degree. C., from about
150.degree. C. to about 170.degree. C., and from about 150.degree.
C. to about 160.degree. C. In some aspects, Z0 may have a
temperature from about 60.degree. C. to about 110.degree. C. or no
cooling; Z1 may have a temperature from about 120.degree. C. to
about 130.degree. C.; Z2 may have a temperature from about
140.degree. C. to about 150.degree. C.; Z3 may have a temperature
from about 150.degree. C. to about 160.degree. C.; Z4 may have a
temperature from about 150.degree. C. to about 160.degree. C.; Z5
may have a temperature from about 150.degree. C. to about
160.degree. C.; Z6 may have a temperature from about 150.degree. C.
to about 160.degree. C.; and Z7-Z12 may each have a temperature
from about 150.degree. C. to about 160.degree. C.
[0095] In some aspects, the number average molecular weight of the
silane-grafted polyolefin elastomers may be in the range of from
about 4,000 g/mol to about 30,000 g/mol, including from about 5,000
g/mol to about 25,000 g/mol and from about 6,000 g/mol to about
14,000 g/mol. The weight average molecular weight of the grafted
polymers may be from about 8,000 g/mol to about 60,000 g/mol,
including from about 10,000 g/mol to about 30,000 g/mol.
[0096] Referring now to FIGS. 6 and 7B, the method 300 next
includes a step 308 of extruding the silane-grafted polyolefin
blend 206, the condensation catalyst 210, and the foaming agent 214
together to form a foamed silane-crosslinkable polyolefin blend
212. In some aspects, one or more optional additives may be added
with the silane-grafted polyolefin blend 206 and the condensation
catalyst 210 to adjust the final material properties of the sponge
silane-crosslinked olefin blend. In step 308, the silane-grafted
polyolefin blend 206 is mixed with a silanol forming condensation
catalyst 210 to form reactive silanol groups on the silane grafts
that can subsequently crosslink when exposed to humidity and/or
heat. In some aspects, the condensation catalyst can include a
mixture of sulfonic acid, antioxidant, process aide, and carbon
black for coloring where the ambient moisture is sufficient for
this condensation catalyst to crosslink the foamed
silane-crosslinkable polyolefin blend over a longer time period
(e.g., about 48 hours). The silane-grafted polyolefin blend 206 and
the condensation catalyst 210 may be added to a reactive single
screw extruder 218 using an addition hopper and an addition gear
pump 226. The combination of the silane-grafted polyolefin blend
206 and the condensation catalyst 210, and in some aspects one or
more optional additives 214, may be added to a single screw 222 of
the reactive single screw extruder 218. The single screw extruder
218 is considered reactive because crosslinking can begin as soon
as the silane-grafted polyolefin blend 206 and the condensation
catalyst 210 are melted and combined together to mix the
condensation catalyst 210 thoroughly and evenly throughout the
melted silane-grafted polyolefin blend 206. The melted foamed
silane-crosslinkable polyolefin blend 212 can exit the reactive
single screw extruder 218 through a die that can inject the molten
foamed silane-crosslinkable polyolefin blend into an uncured
dynamic sealing element.
[0097] During step 308, as the silane-grafted polyolefin blend 206
is extruded together with the condensation catalyst 210 and foaming
agent to form the foamed silane-crosslinkable polyolefin blend 212,
a certain amount of crosslinking may occur. In some aspects, the
foamed silane-crosslinkable polyolefin blend 212 may be about 25%
cured, about 30% cured, about 35% cured, about 40% cured, about 45%
cured, about 50% cured, about 55% cured, about 60% cured, bout 65%
cured, or about 70% cured, where a gel test (ASTM D2765) can be
used to determine the amount of crosslinking in the final foamed
silane-crosslinked polyolefin elastomer.
[0098] Still referring to FIGS. 6 and 7B, the method 300 further
includes a step 312 of molding the foamed silane-crosslinkable
polyolefin blend 212 into the uncured dynamic sealing element. The
single screw extruder 218 melts and extrudes the foamed
silane-crosslinkable polyolefin through a die that can inject the
molten foamed silane-crosslinkable polyolefin blend 212 into the
uncured dynamic sealing element, for example, uncured or partially
cured versions dynamic sealing members 12, such as the hood seal
134, front pillar margin seal 138, and headlamp seal 142.
[0099] Referring again to FIG. 6, the method 300 can further
include a step 316 of crosslinking the foamed silane-crosslinkable
polyolefin blend 212 or the dynamic sealing member 12 in an uncured
form (i.e., an uncured dynamic sealing member element) at an
ambient temperature and/or an ambient humidity to form the dynamic
sealing member 12 (see FIGS. 1-3) having a density from about 0.50
g/cm.sup.3 to about 0.59 g/cm.sup.3. More particularly, in this
crosslinking process, the water hydrolyzes the silane of the foamed
silane-crosslinkable polyolefin elastomer to produce a silanol. The
silanol groups on various silane grafts can then be condensed to
form intermolecular, irreversible Si--O--Si crosslink sites. The
amount of crosslinked silane groups, and thus the final polymer
properties, can be regulated by controlling the production process,
including the amount of catalyst used.
[0100] The crosslinking/curing of step 316 of the method 300 may
occur over a time period of from greater than 0 to about 20 hours.
In some aspects, curing takes place over a time period of from
about 1 hour to about 20 hours, 10 hours to about 20 hours, from
about 15 hours to about 20 hours, from about 5 hours to about 15
hours, from about 1 hour to about 8 hours, or from about 3 hours to
about 6 hours. The temperature during the crosslinking/curing may
be about room temperature, from about 20.degree. C. to about
25.degree. C., from about 20.degree. C. to about 150.degree. C.,
from about 25.degree. C. to about 100.degree. C., or from about
20.degree. C. to about 75.degree. C. The humidity during curing may
be from about 30% to about 100%, from about 40% to about 100%, or
from about 50% to about 100%.
[0101] In some aspects, an extruder setting is used that is capable
of extruding thermoplastic, with long L/D, 30 to 1, at an extruder
heat setting close to TPV processing conditions wherein the
extrudate crosslinks at ambient conditions becoming a thermoset in
properties. In other aspects, this process may be accelerated by
steam exposure. Immediately after extrusion, the gel content (also
called the crosslink density) may be about 60%, but after 96 hrs at
ambient conditions, the gel content may reach greater than about
95%.
[0102] In some aspects, one or more reactive single screw extruders
218 may be used to form the uncured dynamic sealing element and
corresponding dynamic sealing member that have one or more types of
silane-crosslinked polyolefin elastomers. For example, in some
aspects, one reactive single screw extruder 218 may be used to
produce and extrude a foamed (also referred to as a sponge or
dynamic) silane-crosslinked polyolefin elastomer while a second
reactive single screw extruder 218 may be used to produce and
extrude a dense or micro-dense silane-crosslinked polyolefin
elastomer. The complexity and architecture of the final dynamic
sealing member 12 will determine the number and types of reactive
single screw extruders 218 employed according to the process
depicted in FIGS. 6-7B.
[0103] It is understood that the description outlining and teaching
the various dynamic sealing members 12, and their respective
components and compositions, can be used in any combination, and
applies equally well to the method 300 for making the sponge
sealing member using the two-step Sioplas process as shown in FIGS.
6-7B.
[0104] Referring now to FIGS. 8 and 9, a method 400 for making a
dynamic seal, such as dynamic sealing member 12, using the one-step
Monosil process is shown. The method 400 may begin with a step 404
that includes extruding (e.g., with a single screw extruder 230)
the first polyolefin 170 having a density less than 0.86
g/cm.sup.3, the second polyolefin 174, the silan cocktail 178
including the the silane crosslinker (e.g., vinyltrimethoxy silane,
VTMO) and grafting initiator (e.g. dicumyl peroxide), and the
condensation catalyst 210 together to form the crosslinkable
silane-grafted polyolefin blend. The first polyolefin 170, second
polyolefin 174, and silan cocktail 178 may be added to the reactive
single screw extruder 230 using an addition hopper 186. In some
aspects, the silan cocktail 178 may be added to a single screw 234
further down the extrusion line to help promote better mixing with
the first and second polyolefin 170, 174 blend. In some aspects,
one or more optional additives 214 may be added with the first
polyolefin 170, second polyolefin 174, and silan cocktail 178 to
tweak the final material properties of the foamed
silane-crosslinkable polyolefin blend 212. The single screw
extruder 230 is considered reactive because the radical initiator
and silane crosslinker of the silan cocktail 178 are reacting with
and forming new covalent bonds with both the first and second
polyolefin blends 170, 174. In addition, the reactive single screw
extruder 230 mixes the condensation catalyst 210 in together with
the melted silane-grafted polyolefin blend. The melted foamed
silane-crosslinkable polyolefin blend 212 can exit the reactive
single screw extruder 230 using a gear pump (not shown) and/or die
that can eject the molten foamed silane-crosslinkable polyolefin
blend into the form of an uncured dynamic sealing element.
[0105] During step 404, as the first polyolefin 170, second
polyolefin 174, silan cocktail 178, and condensation catalyst 210
are extruded together, a certain amount of crosslinking may occur
in the reactive single screw extruder 230 (see FIGS. 8 and 9). In
some aspects, the foamed silane-crosslinkable polyolefin blend 212
may be about 25% cured, about 30% cured, about 35% cured, about 40%
cured, about 45% cured, about 50% cured, about 55% cured, about 60%
cured, bout 65% cured, or about 70% as it leaves the reactive
single screw extruder 230. The gel test (ASTM D2765) can be used to
determine the amount of crosslinking in the final foamed
silane-crosslinked polyolefin elastomer.
[0106] The reactive single screw extruder 230 can be configured to
have a plurality of different temperature zones (e.g., Z0-Z7 as
shown in FIG. 9) that extend for various lengths along the
extruder. In some aspects, the respective temperature zones may
have temperatures ranging from about room temperature to about
180.degree. C., from about 120.degree. C. to about 170.degree. C.,
from about 120.degree. C. to about 160.degree. C., from about
120.degree. C. to about 150 .degree. C., from about 120.degree. C.
to about 140.degree. C., from about 120.degree. C. to about
130.degree. C., from about 130.degree. C. to about 170.degree. C.,
from about 130.degree. C. to about 160.degree. C., from about
130.degree. C. to about 150.degree. C., from about 130.degree. C.
to about 140.degree. C., from about 140.degree. C. to about
170.degree. C., from about 140.degree. C. to about 160.degree. C.,
from about 140.degree. C. to about 150.degree. C., from about
150.degree. C. to about 170.degree. C., and from about 150.degree.
C. to about 160.degree. C. In some aspects, Z0 may have a
temperature from about 60.degree. C. to about 110.degree. C. or no
cooling; Z1 may have a temperature from about 120.degree. C. to
about 130.degree. C.; Z2 may have a temperature from about
140.degree. C. to about 150.degree. C.; Z3 may have a temperature
from about 150.degree. C. to about 160.degree. C.; Z4 may have a
temperature from about 150.degree. C. to about 160.degree. C.; Z5
may have a temperature from about 150.degree. C. to about
160.degree. C.; Z6 may have a temperature from about 150.degree. C.
to about 160.degree. C.; and Z7 may have a temperature from about
150.degree. C. to about 160.degree. C.
[0107] In some aspects, the number average molecular weight of the
silane-grafted polyolefin elastomers may be in the range of from
about 4,000 g/mol to about 30,000 g/mol, including from about 5,000
g/mol to about 25,000 g/mol and from about 6,000 g/mol to about
14,000 g/mol. The weight average molecular weight of the grafted
polymers may be from about 8,000 g/mol to about 60,000 g/mol,
including from about 10,000 g/mol to about 30,000 g/mol.
[0108] Still referring to FIGS. 8 and 9, the method 400 further
includes a step 408 of molding the foamed silane-crosslinkable
polyolefin blend into an uncured dynamic sealing element. The
reactive single screw extruder 230 can melt and extrude the foamed
silane-crosslinkable polyolefin through the die that can eject the
molten foamed silane-crosslinkable polyolefin blend into the
uncured dynamic sealing element to then be cured into the dynamic
sealing member 12 (see FIGS. 1-3), for example, the hood seal 134,
front pillar margin seal 138, and headlamp seal 142.
[0109] Still referring to FIG. 8, the method 400 can further
include a step 412 of crosslinking the foamed silane-crosslinkable
polyolefin blend 212 of the uncured dynamic sealing element at an
ambient temperature and an ambient humidity to form the element
into the dynamic seal, such as dynamic sealing member 12 having a
density from about 0.50 g/cm.sup.3 to about 0.59 g/cm.sup.3. The
amount of crosslinked silane groups, and thus the final polymer
properties, can be regulated by controlling the production process,
including the amount of catalyst used.
[0110] The step 412 of crosslinking the foamed silane-crosslinkable
polyolefin blend may occur over a time period of from greater than
0 to about 20 hours. In some aspects, curing takes place over a
time period of from about 1 hour to about 20 hours, 10 hours to
about 20 hours, from about 15 hours to about 20 hours, from about 5
hours to about 15 hours, from about 1 hour to about 8 hours, or
from about 3 hours to about 6 hours. The temperature during the
crosslinking and curing may be about room temperature, from about
20.degree. C. to about 25.degree. C., from about 20.degree. C. to
about 150.degree. C., from about 25.degree. C. to about 100.degree.
C., or from about 20.degree. C. to about 75.degree. C. The humidity
during curing may be from about 30% to about 100%, from about 40%
to about 100%, or from about 50% to about 100%.
[0111] In some aspects, an extruder setting is used that is capable
of extruding thermoplastic, with long LID, 30 to 1, at an extruder
heat setting close to TPV processing conditions wherein the
extrudate crosslinks at ambient conditions becoming a thermoset in
properties. In other aspects, this process may be accelerated by
steam exposure. Immediately after extrusion, the gel content (also
called the crosslink density) may be about 60%, but after 96 hrs at
ambient conditions, the gel content may reach greater than about
95%.
[0112] In some aspects, one or more reactive single screw extruders
230 (see FIG. 9) may be used to form the uncured sealing element
and corresponding dynamic sealing member that have one or more
types of silane-crosslinked polyolefin elastomers. For example, in
some aspects, one reactive single screw extruder 230 may be used to
produce and extrude the foamed silane-crosslinked
polyolefinelastomer while a second reactive single screw extruder
230 may be used to produce and extrude a dense or micro-dense
silane-crosslinked polyolefin elastomer. The complexity and
architecture of the final dynamic sealing member 12 will determine
the number and types of reactive single screw extruder 230.
[0113] It is understood that the description outlining and teaching
the various dynamic sealing members 12, and their respective
components and compositions, can be used in any combination, and
applies equally well to the method 400 for making the sponge
sealing member using the one-step Monosil process as shown in FIGS.
8 and 9.
[0114] Non-limiting examples of articles that the foamed
silane-crosslinked polyolefin elastomer of the disclosure may be
used to manufacture include dynamic sealing members 12 (see FIGS.
1-3), such as weatherstrip seals (e.g., glass run channels
including molded details/corners), sunroof seals, convertible top
seals, mirror seals, body-panel interface seals, stationary window
moldings, glass encapsulations, cut-line seals, greenhouse
moldings, occupation detector system sensor switches, rocker seals,
outer and inner belts, auxiliary and margin seals, edge
protector/gimp seals, and below-belt brackets and channels;
automotive hoses such as coolant hoses, air conditioning hoses, and
vacuum hoses; anti-vibration system (AVS) components such as mounts
(e.g., engine, body, accessory, component), dampers, bushings,
strut mounts, and isolators; coatings such as coatings for brake
lines, fuel lines, transmission oil cooler lines, brackets, cross
members, frame components, body panels and components, suspension
components, wheels, hubs, springs, and fasteners; air deflectors,
spoilers, fascia, and trim; building, window, and door seals;
boots, bellows, and grommets; gaskets (e.g., pneumatic and/or
hydraulic gaskets); wire and cable sheathing; tires; windshield
wipers and squeegees; floor mats; pedal covers; automotive belts;
conveyor belts; shoe components; marine bumpers; O-rings; valves
and seals; and springs (e.g., as substitutes for mechanical metal
springs).
Dynamic Silane-Crosslinked Polyolefin Elastomer Physical
Properties
[0115] A "thermoplastic", as used herein, is defined to mean a
polymer that softens when exposed to heat and returns to its
original condition when cooled to room temperature. A "thermoset",
as used herein, is defined to mean a polymer that solidifies and
irreversibly "sets" or "crosslinks" when cured. In either of the
Monosil or Sioplas processes described above, it is important to
understand the careful balance of thermoplastic and thermoset
properties of the various different materials used to produce the
final thermoset dynamic silane-crosslinked polyolefin elastomer or
sponge sealing member. Each of the intermediate polymer materials
mixed and reacted using a reactive twin screw extruder, a reactive
single screw extruder, and/or a reactive single screw extruder are
thermosets. Accordingly, the silane-grafted polyolefin blend and
the silane-crosslinkable polyolefin blend are thermoplastics and
can be softened by heating so the respective materials can flow.
Once the silane-crosslinkable polyolefin blend is extruded, molded,
pressed, and/or shaped into the uncured sealing element or other
respective article, the silane-crosslinkable polyolefin blend can
begin to crosslink or cure at an ambient temperature and an ambient
humidity to form the sponge sealing member and dynamic
silane-crosslinked polyolefin blend.
[0116] The thermoplastic/thermoset behavior of the
silane-crosslinkable polyolefin blend and corresponding dynamic
silane-crosslinked polyolefin blend are important for the various
compositions and articles disclosed herein (e.g., dynamic sealing
members 12 shown in FIGS. 1-3) because of the potential energy
savings provided using these materials. For example, a manufacturer
can save considerable amounts of energy by being able to cure the
silane-crosslinkable polyolefin blend at an ambient temperature and
an ambient humidity. This curing process is typically performed in
the industry by applying significant amounts of energy to heat or
steam treat crosslinkable polyolefins. The ability to cure the
inventive silane-crosslinkable polyolefin blend with ambient
temperature and/or ambient humidity are not properties necessarily
intrinsic to crosslinkable polyolefins, but rather is a property
dependent on the relatively low density (i.e., as compared to EPDM
and/or TPV) of the silane-crosslinkable polyolefin blend. In some
aspects, no additional curing overs, heating ovens, steam ovens, or
other forms of heat producing machinery other than what was
provided in the extruders are used to form the dynamic
silane-crosslinked polyolefin elastomers.
[0117] The specific gravity of the dynamic silane-crosslinked
polyolefin elastomer of the present disclosure may be lower than
the specific gravities of existing TPV and EPDM formulations used
in the art. The reduced specific gravity of these materials can
lead to lower weight parts, thereby helping automakers meet
increasing demands for improved fuel economy. For example, the
specific gravity of the dynamic silane-crosslinked polyolefin
elastomer of the present disclosure may be from about 0.40
g/cm.sup.3to about 0.59 g/cm.sup.3, from about 0.50 g/cm.sup.3to
about 0.59 g/cm.sup.3, from about 0.40 g/cm.sup.3to about 0.49
g/cm.sup.3, less than 0.60 g/cm.sup.3, less than 0.55 g/cm.sup.3,
less than 0.50 g/cm.sup.3, or less than 0.45 g/cm.sup.3 as compared
to existing TPV materials which may have a specific gravity of from
0.95 to 1.2 g/cm.sup.3 and EPDM materials which may have a specific
gravity of from 1.0 to 1.35 g/cm.sup.3. The low specific gravity or
density of the dynamic silane-crosslinked polyolefin elastomer is
attributable to the low crystallinity of the found in the Examples
described below. In some aspects, the percent crystallinity of the
dynamic silane-crosslinked polyolefin elastomer is less than 10%,
less than 20%, or less than 30%.
[0118] Referring now to FIG. 10, the stress/strain behavior of an
exemplary dynamic silane-crosslinked polyolefin elastomer of the
present disclosure (i.e., the "Silane-Crosslinked Polyolefin
Elastomer" in the legend) relative to two conventional EPDM
materials (i.e., the "EPDM compound A" and "EPDM compound B") is
provided. In particular, FIG. 10 shows that the area between the
stress/strain curves for a sponge/foamed/dynamic silane-crosslinked
polyolefin of the disclosure is significantly smaller than the
respective areas between the stress/strain curves for EPDM
compounds A and B. This smaller area between the stress/strain
curves for the silane-crosslinked polyolefin elastomer can be
desirable for dynamic sealing members, such as weatherstrip seals,
used with automotive glass applications. Elastomeric materials
typically have non-linear stress-strain curves with a significant
loss of energy when repeatedly stressed. The silane-crosslinked
polyolefin elastomers of the present disclosure may exhibit greater
elasticity and less viscoelasticity (e.g., have linear curves and
exhibit very low energy loss). Embodiments of the
silane-crosslinked polyolefin elastomers described herein do not
have any filler or plasticizer incorporated into these materials so
their corresponding stress/strain curves do not have or display any
Mullins effect and/or Payne effect. The lack of Mullins effect for
these silane-crosslinked polyolefin elastomers is due to the lack
of any reinforcing fillers (e.g., carbon black) or plasticizer
added to the silane-crosslinked polyolefin blend so the
stress-strain curve does not depend on the maximum loading
previously encountered where there is no instantaneous and
irreversible softening. The lack of Payne effect for these
silane-crosslinked polyolefin elastomers is due to the lack of any
filler or plasticizer added to the silane-crosslinked polyolefin
blend so the stress-strain curve does not depend on the small
strain amplitudes previously encountered where there is no change
in the viscoelastic storage modulus based on the amplitude of the
strain.
[0119] The silane-crosslinked polyolefin elastomer or dynamic
sealing members of the disclosure can exhibit a compression set of
from about 5.0% to about 30.0%, from about 5.0% to about 25.0%,
from about 5.0% to about 20.0%, from about 5.0% to about 15.0%,
from about 5.0% to about 10.0%, from about 10.0% to about 25.0%,
from about 10.0% to about 20.0%, from about 10.0% to about 15.0%,
from about 15.0% to about 30.0%, from about 15.0% to about 25.0%,
from about 15.0% to about 20.0%, from about 20.0% to about 30.0%,
or from about 20.0% to about 25.0%, as measured according to ASTM D
395 (22 hrs @ 23.degree. C., 70.degree. C., 80.degree. C.,
90.degree. C., 125.degree. C., and/or 175.degree. C.).
[0120] In other implementations, the silane-crosslinked polyolefin
elastomer or the dynamic sealing members of the disclosure can
exhibit a compression set of from about 5.0% to about 20.0%, from
about 5.0% to about 15.0%, from about 5.0% to about 10.0%, from
about 7.0% to about 20.0%, from about 7.0% to about 15.0%, from
about 7.0% to about 10.0%, from about 9.0% to about 20.0%, from
about 9.0% to about 15.0%, from about 9.0% to about 10.0%, from
about 10.0% to about 20.0%, from about 10.0% to about 15.0%, from
about 12.0% to about 20.0%, or from about 12.0% to about 15.0%, as
measured according to ASTM D 395 (22 hrs @ 23.degree. C.,
70.degree. C., 80.degree. C., 90.degree. C., 125.degree. C., and/or
175.degree. C.).
[0121] The silane-crosslinked polyolefin elastomers and dynamic
sealing members of the disclosure may exhibit a crystallinity of
from about 5% to about 40%, from about 5% to about 25%, from about
5% to about 15%, from about 10% to about 20%, from about 10% to
about 15%, or from about 11% to about 14% as determined using
density measurements, differential scanning calorimetry (DSC),
X-Ray Diffraction, infrared spectroscopy, and/or solid state
nuclear magnetic spectroscopy. As disclosed herein, DSC was used to
measure the enthalpy of melting in order to calculate the
crystallinity of the respective samples.
[0122] The silane-crosslinked polyolefin elastomers and dynamic
sealing members of the disclosure may exhibit a glass transition
temperature of from about -75.degree. C. to about -25.degree. C.,
from about -65.degree. C. to about -40.degree. C., from about
-60.degree. C. to about -50.degree. C., from about -50.degree. C.
to about -25.degree. C., from about -50.degree. C. to about
-30.degree. C., or from about -45.degree. C. to about -25.degree.
C. as measured according to differential scanning calorimetry (DSC)
using a second heating run at a rate of 5.degree. C./min or
10.degree. C./min.
[0123] The silane-crosslinked polyolefin elastomers and sponge
sealing members may exhibit a weathering color difference of from
about 0.25 .DELTA.E to about 2.0 .DELTA.E, from about 0.25 .DELTA.E
to about 1.5 .DELTA.E, from about 0.25 .DELTA.E to about 1.0
.DELTA.E, or from about 0.25 .DELTA.E to about 0.5 .DELTA.E, as
measured according to ASTM D2244 after 3000 hrs exposure to
exterior weathering conditions.
EXAMPLES
[0124] The following non-limiting examples are provided as
exemplary embodiments of the dynamic sealing members, compositions
and methods of making the same outlined in the disclosure.
Materials
[0125] All chemicals, precursors and other constituents were
obtained from commercial suppliers and used as provided without
further purification.
Example 1
[0126] Example 1 (Ex. 1) or ED108-2A was produced by extruding
48.70 wt % ENGAGE 8842 and 48.70 wt % XUS38677.15 together with 2.6
wt % SI LAN RHS 14/032 or SILFIN 13 to form a silane-grafted
polyolefin elastomer. The Example 1 silane-grafted polyolefin
elastomer was then extruded with 1.7 wt % Hydrocerol 1170 foaming
agent, 2 wt % Ambicat LE4472 condensation catalyst, and 360 ppm
dioctyltin dilaurate (DOTL) condensation catalyst to form a
silane-crosslinkable polyolefin elastomer, which was then extruded
into an uncured dynamic sealing member. The Example 1
silane-crosslinkable polyolefin elastomer of the uncured dynamic
sealing member was then cured at ambient temperature and humidity
to form a silane-crosslinked polyolefin elastomer, consistent with
the elastomers of the disclosure. The composition of Example 1 is
provided in Table 1 below and its material properties are provided
in Table 2 below.
Example 2
[0127] Example 2 (Ex. 2) or ED108-2B was produced by extruding
48.70 wt % ENGAGE 8842 and 48.70 wt % XUS38677.15 and 2.6 wt %
SILAN RHS 14/032 or SILFIN 13 together with Exact 9061/SpectraSyn
10 (70/30) to form the silane-grafted polyolefin elastomer. The
Example 2 silane-grafted polyolefin elastomer was then extruded
with 1.7 wt % Hydrocerol 1170 foaming agent, 2 wt % Ambicat LE4472
condensation catalyst, and 360 ppm dioctyltin dilaurate (DOTL)
condensation catalyst to form a silane-crosslinkable polyolefin
elastomer, which was then extruded into an uncured dynamic sealing
member. The Example 2 silane-crosslinkable polyolefin elastomer of
the uncured dynamic sealing member was then cured at ambient
temperature and humidity to form a silane-crosslinked polyolefin
elastomer, consistent with the elastomers of the disclosure. The
composition of Example 2 is provided in Table 1 below and its
material properties are provided in Table 2 below. Also provided
below in Table 2 are properties associated with a comparative EPDM
material ("EPDM").
TABLE-US-00001 TABLE 1 Ingredients Ex. 1 Ex. 2 ENGAGE XLT8677/XUS
38677.15 48.7 46.25 ENGAGE 8842 48.7 46.25 SILAN RHS 14/032 or
SILFIN 29 2.6 2.5 Exact 9061/SpectraSyn 10 (70/30) -- 5 TOTAL 100
100
TABLE-US-00002 TABLE 2 Property Test Method Units/Output Ex. 1 Ex.
2 EPDM Structural Density ASTM D297 g/cc 0.52 0.55 0.66 Tensile
ASTM D412 MPa 2.6 2.0 2.9 Die C Elongation ASTM D412 % 230 209 354
Die C 100% Modulus ASTM D412 MPa 1.5 1.4 0.80 Die C Tear C ASTM
D624 N/mm 8.0 9.6 8.8 Die C Compression Plied C/S ASTM D395 % 29.4
35.4 47.4 Set (22 h/80.degree. C.) Method B (50% Plied C/S ASTM
D395 % 37.6 58.9 56.4 compression) (96 h/80.degree. C.) Method B
Plied C/S ASTM D395 % 67.0 69.6 67.8 (168 h/80.degree. C.) Method B
Plied C/S ASTM D395 % 76.4 -- 73.5 (500 h/80.degree. C.) Method B
Plied C/S ASTM D395 % 78.6 -- 97.3 (1000 h/80.degree. C.) Method B
Miscellaneous Water Absorption GM9888P % 0.16 -- 0.21
[0128] Referring now to FIG. 11, a load vs. position plot is
provided for the Ex. 1 ED108-2A resin (i.e., as prepared above in
Example 1), as crosslinked with 2% catalyst ("Ex. 1 with 2% cat"),
3% catalyst (Ex. 1 with 3% cat"), and 2% catalyst with a slip coat
("Ex. 1 with 2% cat and slip coat"). A comparative example load v.
position plot is provided for a traditional EPDM sponge material
("EPDM''). The Ex. 1 materials (i.e., dynamic silane-crosslinked
polyolefin elastomers according to the disclosure) display a
smaller area between the load/position curves as compared to the
areas between the load/position curves for the comparative EPDM
compound. This smaller area between the load/position curves for
the dynamic silane-crosslinked polyolefin elastomers can be
desirable for dynamic sealing members, e.g., weatherstrips, that
can be used for various sealing applications. Further, the Ex. 1
polyolefin blends do not contain any filler or plasticizer
incorporated so each of corresponding load/position curves for
these blends do not have or display any Mullins effect and/or Payne
effect.
[0129] The selection of the condensation catalyst may have an
influence on the final material properties for a sample. For
example, the Example 2 ED108-2B silane-grafted polyolefin elastomer
was produced by extruding 48.70 wt % ENGAGE 8842 and 48.70 wt %
XUS38677.15 and 2.6 wt % SILAN RHS 14/032 or SILFIN 13 together
with Exact 9061/SpectraSyn 10 (70/30) to form the silane-grafted
polyolefin elastomer. These Example 2 silane-grafted polyolefin
elastomers were then extruded with two different condensation
catalysts: (a) with 1.7 wt % Hydrocerol 1170 foaming agent, 2 wt %
Ambicat LE4472 condensation catalyst, and 360 ppm dioctyltin
dilaurate (DOTL) condensation catalyst; and (b) with 1.7 wt %
Hydrocerol 1170 foaming agent, 2 wt % Ambicat LE4472 condensation
catalyst, and 360 ppm dibutyltin dilaurate (DBTDL) condensation
catalyst. Accordingly, two silane-crosslinkable polyolefin
elastomers were formed (identified as "DOTL" and "DBTDL"), which
were then extruded into an uncured dynamic sealing member. The
difference in material properties of these crosslinkable elastomers
are given below in Tables 3 and 4.
TABLE-US-00003 TABLE 3 22 h/80 C. 96 h/80 C. Elastomer Tube C/S
Tube C/S 168 h/80 C. Group (%) (%) Tube C/S DOTL 38.9 42.1 52.3
DBTDL 25.9 27.9 34.0
TABLE-US-00004 TABLE 4 100% Auburn Tensile Elongation Modulus
Density TC Group Duro MPa (%) (Mpa) (g/cc) (N/mm) DOTL 43 2.8 294
1.3 0.52 9.3 DBTDL 39 2.9 170 1.9 0.51 7.6
[0130] Referring now to FIG. 12, cross-sectional views are provided
for a silane-crosslinked polyolefin elastomer foamed used
supercritical gas injection and chemical foaming agents. As
provided by the images, the pore size resulting from the chemical
foaming agent is from 20 .mu.m to 147 .mu.m while the pore size
resulting from the supercritical gas injection is from 46 .mu.m to
274 .mu.m. Depending on the type of foaming agent selected to foam
each of the respective silane-crosslinkable polyolefin elastomer
disclosed herein, a variety of different pore sizes can be obtained
which will affect the final density of the foamed
silane-crosslinked polyolefin elastomer. In some aspects, the pore
size may be from 20 .mu.m to 200 .mu.m, from 25 .mu.m to 400 .mu.m,
or from 25 .mu.m to 300 .mu.m.
[0131] For purposes of this disclosure, the term "coupled" (in all
of its forms, couple, coupling, coupled, etc.) generally means the
joining of two components directly or indirectly to one another.
Such joining may be stationary in nature or movable in nature. Such
joining may be achieved with the two components and any additional
intermediate members being integrally formed as a single unitary
body with one another or with the two components. Such joining may
be permanent in nature or may be removable or releasable in nature
unless otherwise stated.
[0132] It is also important to note that the construction and
arrangement of the elements of the device as shown in the exemplary
embodiments is illustrative only. Although only a few embodiments
of the present innovations have been described in detail in this
disclosure, those skilled in the art who review this disclosure
will readily appreciate that many modifications are possible (e.g.,
variations in sizes, dimensions, structures, shapes and proportions
of the various elements, values of parameters, mounting
arrangements, use of materials, colors, orientations, etc.) without
materially departing from the novel teachings and advantages of the
subject matter recited. For example, elements shown as integrally
formed may be constructed of multiple parts or elements shown as
multiple parts may be integrally formed, the operation of the
interfaces may be reversed or otherwise varied, the length or width
of the structures and/or members or connector or other elements of
the system may be varied, the nature or number of adjustment
positions provided between the elements may be varied. It should be
noted that the elements and/or assemblies of the system may be
constructed from any of a wide variety of materials that provide
sufficient strength or durability, in any of a wide variety of
colors, textures, and combinations. Accordingly, all such
modifications are intended to be included within the scope of the
present innovations. Other substitutions, modifications, changes,
and omissions may be made in the design, operating conditions, and
arrangement of the desired and other exemplary embodiments without
departing from the spirit of the present innovations.
[0133] It will be understood that any described processes or steps
within described processes may be combined with other disclosed
processes or steps to form structures within the scope of the
present device. The exemplary structures and processes disclosed
herein are for illustrative purposes and are not to be construed as
limiting.
[0134] The above description is considered that of the illustrated
embodiments only.
[0135] Modifications of the device will occur to those skilled in
the art and to those who make or use the device. Therefore, it is
understood that the embodiments shown in the drawings and described
above is merely for illustrative purposes and not intended to limit
the scope of the articles, processes and compositions, which are
defined by the following claims as interpreted according to the
principles of patent law, including the Doctrine of
Equivalents.
Listing of Non-Limiting Embodiments
[0136] Embodiment A is a sponge sealing member comprising: a
composition comprising a silane-crosslinked polyolefin elastomer
having a density less than 0.60 g/cm.sup.3, wherein the sponge
sealing member exhibits a compression set of from about 5.0% to
about 35.0%, as measured according to ASTM D 395 (22 hrs @
70.degree. C.).
[0137] The sponge sealing member of Embodiment A wherein the
silane-crosslinked polyolefin elastomer comprises a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin having a percent crystallinity less than 40%, a silane
crosslinker, a grafting initiator, a condensation catalyst, and a
foaming agent.
[0138] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features wherein the compression set is
from about 15.0% to about 35.0%, as measured according to ASTM D
395 (22 hrs @ 70.degree. C.).
[0139] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features wherein the density is from
about 0.50 g/cm.sup.3 to about 0.59 g/cm.sup.3.
[0140] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features wherein the silane-crosslinked
polyolefin elastomer exhibits a crystallinity of from about 5% to
about 25%.
[0141] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features wherein the silane-crosslinked
polyolefin elastomer exhibits a glass transition temperature of
from about -75.degree. C. to about -25.degree. C.
[0142] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features wherein the composition is a
thermoset, but exhibits thermoplastic properties during
processing.
[0143] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features wherein the sponge sealing
member exhibits a weathering color difference of from about 0.25
.DELTA.E to about 2.0 .DELTA.E, as measured according to ASTM
D2244.
[0144] The sponge sealing member of Embodiment A or Embodiment A
with any of the intervening features further comprising: a coloring
agent.
[0145] Embodiment B is a foamed silane-crosslinked polyolefin blend
comprising: a first polyolefin having a density less than 0.86
g/cm.sup.3; a second polyolefin having a percent crystallinity less
than 40%; a silane crosslinker; and a foaming agent, wherein the
foamed silane-crosslinked polyolefin blend exhibits a compression
set of from about 5.0% to about 35.0%, as measured according to
ASTM D 395 (22 hrs @ 70.degree. C.), and wherein the foamed
silane-crosslinked polyolefin blend has a density less than 0.60
g/cm.sup.3.
[0146] The foamed silane-crosslinked polyolefin blend of Embodiment
B wherein the first polyolefin comprises an ethylene octene
copolymer from about 60 wt % to about 97 wt %.
[0147] The foamed silane-crosslinked polyolefin blend of Embodiment
B or Embodiment B with any of the intervening features wherein the
second polyolefin comprises a polypropylene homopolymer from about
10 wt % to about 35 wt % and/or a poly(ethylene-co-propylene).
[0148] The foamed silane-crosslinked polyolefin blend of Embodiment
B or Embodiment B with any of the intervening features wherein the
silane crosslinker comprises a vinyltrimethoxy silane from about 1
wt % to about 4 wt %.
[0149] The foamed silane-crosslinked polyolefin blend of Embodiment
B or Embodiment B with any of the intervening features further
comprising a non-metal condensation catalyst that comprises a
sulfonic ester from about 1 wt % to about 4 wt %.
[0150] The foamed silane-crosslinked polyolefin blend of Embodiment
B or Embodiment B with any of the intervening features wherein the
blend has a density from about 0.85 g/cm.sup.3 to about 0.89
g/cm.sup.3.
[0151] The foamed silane-crosslinked polyolefin blend of Embodiment
B or Embodiment B with any of the intervening features wherein the
blend exhibits a crystallinity of from about 5% to about 25%.
[0152] The foamed silane-crosslinked polyolefin blend of Embodiment
B or Embodiment B with any of the intervening features wherein the
blend exhibits a glass transition temperature of from about
-75.degree. C. to about -25.degree. C.
[0153] Embodiment C is a method for making a sponge sealing member,
the method comprising: extruding a first polyolefin having a
density less than 0.86 g/cm.sup.3, a second polyolefin having a
crystallinity less than 40%, a silane crosslinker and a grafting
initiator together to form a silane-grafted polyolefin blend;
extruding the silane-grafted polyolefin blend, a condensation
catalyst, and a foaming agent together to form a foamed
silane-crosslinkable polyolefin blend; molding the foamed
silane-crosslinkable polyolefin blend into an uncured sponge
sealing element; and crosslinking the foamed
crosslinkable-polyolefin blend of the uncured sponge sealing
element at an ambient temperature and an ambient humidity to form
the element into a sponge sealing member having a density from
about 0.85 g/cm.sup.3 to about 0.89 g/cm.sup.3 comprising a foamed
silane-crosslinked polyolefin blend, wherein the sponge sealing
member exhibits a compression set of from about 5.0% to about
35.0%, as measured according to ASTM D 395 (22 hrs @ 70.degree.
C.).
[0154] The method of Embodiment C wherein the silane-grafted
polyolefin blend and the crosslinkable-polyolefin blend are
thermoplastics, and the foamed-silane crosslinked polyolefin blend
is a thermoset.
[0155] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the first polyolefin is an
ethylene/.alpha.-olefin copolymer and the second polyolefin is a
polypropylene homopolymer and/or a poly(ethylene-co-propylene).
* * * * *