U.S. patent application number 15/836417 was filed with the patent office on 2018-06-14 for roofing membranes, 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 | 20180162109 15/836417 |
Document ID | / |
Family ID | 60857179 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180162109 |
Kind Code |
A1 |
Gopalan; Krishnamachari ; et
al. |
June 14, 2018 |
ROOFING MEMBRANES, COMPOSITIONS, AND METHODS OF MAKING THE SAME
Abstract
A roofing membrane and a method of making the same is provided.
The roofing membrane includes a top layer having a flame retardant
and a first silane-crosslinked polyolefin elastomer with a density
less than 0.90 g/cm.sup.3; a scrim layer; and a bottom layer having
a flame retardant and a second silane-crosslinked polyolefin
elastomer with a density less than 0.90 g/cm.sup.3. The top and
bottom layers of the roofing membrane both 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.).
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: |
60857179 |
Appl. No.: |
15/836417 |
Filed: |
December 8, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62497954 |
Dec 10, 2016 |
|
|
|
62497959 |
Dec 10, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E04D 5/10 20130101; B32B
2266/08 20130101; C08L 43/04 20130101; B32B 2307/4026 20130101;
C08F 210/06 20130101; C08J 2203/04 20130101; C08L 23/0815 20130101;
A43B 13/04 20130101; C08F 8/00 20130101; C08J 2203/06 20130101;
B32B 2305/72 20130101; C08F 2810/20 20130101; C08J 2323/12
20130101; C08F 2800/20 20130101; C08J 2423/06 20130101; C08J 3/24
20130101; C08J 2203/08 20130101; C08L 23/20 20130101; B32B 27/12
20130101; C08K 5/5419 20130101; C08F 8/12 20130101; B32B 3/263
20130101; C08J 9/122 20130101; C08L 23/06 20130101; C08J 2423/14
20130101; C08F 210/02 20130101; C08J 5/18 20130101; C08J 9/0061
20130101; B32B 2437/02 20130101; C08J 2383/10 20130101; C08L 23/12
20130101; C08J 2205/052 20130101; C08J 2323/08 20130101; B32B 5/028
20130101; B32B 2266/10 20161101; C08G 77/442 20130101; A43B 13/187
20130101; B32B 2419/06 20130101; C08J 9/32 20130101; C08J 2300/26
20130101; C08L 2205/02 20130101; C08K 5/0025 20130101; C08L 23/08
20130101; B32B 5/18 20130101; B32B 27/26 20130101; C08J 2423/12
20130101; C08K 3/22 20130101; E04D 5/06 20130101; C08F 2500/21
20130101; B32B 2307/56 20130101; C08F 255/02 20130101; C08J 3/246
20130101; C08J 9/06 20130101; C08J 2323/16 20130101; C09K 2200/0617
20130101; B32B 27/32 20130101; D06N 5/00 20130101; C08J 2423/16
20130101; C08L 23/16 20130101; C08J 2201/03 20130101; C08F 230/08
20130101; B32B 2307/3065 20130101; C08F 2500/08 20130101; C08L
101/00 20130101; B32B 2266/0207 20130101; B32B 2274/00 20130101;
C08L 23/14 20130101; C08L 2312/08 20130101; C09K 3/1006 20130101;
C08J 2207/00 20130101; C08L 53/00 20130101; B29D 35/122 20130101;
B32B 2307/51 20130101; C08L 51/06 20130101; C08K 5/00 20130101;
B32B 37/15 20130101; B32B 2307/50 20130101; B32B 2307/536 20130101;
B32B 2307/72 20130101; B32B 2307/704 20130101; C08J 2201/026
20130101; C08J 2423/08 20130101; C08F 255/02 20130101; C08F 230/08
20130101; C08F 8/00 20130101; C08F 8/12 20130101; C08F 255/02
20130101; C08L 23/0815 20130101; C08L 23/0815 20130101; C08L
23/0815 20130101; C08L 23/14 20130101 |
International
Class: |
B32B 27/32 20060101
B32B027/32; C08J 5/18 20060101 C08J005/18; C08J 3/24 20060101
C08J003/24; B32B 5/02 20060101 B32B005/02; B32B 37/15 20060101
B32B037/15; E04D 5/10 20060101 E04D005/10; E04D 5/06 20060101
E04D005/06 |
Claims
1. A roofing membrane comprising: a top layer comprising a flame
retardant and a first silane-crosslinked polyolefin elastomer
having a density less than 0.90 g/cm.sup.3; a scrim layer; and a
bottom layer comprising a flame retardant and a second
silane-crosslinked polyolefin elastomer having a density less than
0.90 g/cm.sup.3, wherein the top and bottom layers of the roofing
membrane both 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.).
2. The roofing membrane of claim 1, wherein the compression set is
from about 10% to about 30%.
3. The roofing membrane of claim 1, wherein the first and second
silane-crosslinked polyolefin elastomers both exhibit a
crystallinity of from about 5% to about 25%.
4. The roofing membrane of claim 1, wherein the first and second
silane-crosslinked polyolefin elastomers have a glass transition
temperature of from about -75.degree. C. to about -25.degree.
C.
5. The roofing membrane of claim 1, wherein the first and second
silane-crosslinked polyolefin elastomers each comprise a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
6. The roofing membrane of claim 1, wherein the density is from
about 0.85 g/cm.sup.3 to about 0.89 g/cm.sup.3.
7. The roofing membrane of claim 1, wherein the roofing membrane
exhibits a weathering color difference of from about 0.25 .DELTA.E
to about 2.0 .DELTA.E, as measured according to ASTM D2244.
8. The roofing membrane of claim 1, wherein the first
silane-crosslinked polyolefin elastomer and the second
silane-crosslinked polyolefin elastomer are chemically distinct
from each other.
9. A method of making a roofing membrane, the method comprising:
extruding a first silane-crosslinkable polyolefin elastomer to form
a top layer; extruding a second silane-crosslinkable polyolefin
elastomer to form a bottom layer; calendaring a scrim layer between
the top and the bottom layers to form an uncured roofing membrane
element; and crosslinking the silane-crosslinkable polyolefin
elastomers of the top and the bottom layers in the uncured roofing
membrane element at a curing temperature and a curing humidity to
form the roofing membrane, wherein the top and bottom layers of the
roofing membrane both 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.).
10. The method of claim 9, wherein the first silane-crosslinkable
polyolefin elastomer and the second silane-crosslinkable polyolefin
elastomer are chemically distinct from each other.
11. The method of claim 9, wherein the curing temperature is an
ambient temperature.
12. The method of claim 9, wherein the curing humidity is an
ambient humidity.
13. The method of claim 9, wherein the first and second
silane-crosslinkable polyolefin elastomers each comprise a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
14. The method of claim 9, wherein the roofing membrane exhibits a
weathering color difference of from about 0.25 .DELTA.E to about
2.0 .DELTA.E, as measured according to ASTM D2244.
15. The method of claim 9, wherein the roofing membrane exhibits a
flame retardance rating of classification D as measured in
accordance with the EN ISO 11925-2 surface exposure test.
16. A method of making a high-load flame retardant thermoplastic
polyolefin (TPO) roofing membrane, the method comprising: adding a
silane-grafted polyolefin elastomer, a flame retardant, and a
condensation catalyst to a reactive single screw extruder to
produce a silane-crosslinkable polyolefin elastomer; calendaring
the silane-crosslinkable polyolefin elastomer to form a top layer
and a bottom layer; calendaring a scrim layer between the top and
the bottom layers to form an uncured roofing membrane element; and
crosslinking the silane-crosslinkable polyolefin elastomers of the
top and the bottom layers in the uncured roofing membrane element
at an ambient temperature and an ambient humidity to form the
thermoplastic polyolefin (TPO) roofing membrane, wherein the top
and bottom layers of the thermoplastic polyolefin (TPO) roofing
membrane both 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.).
17. The method of claim 16, wherein the top and bottom layers are
chemically equivalent to each other.
18. The method of claim 16, wherein the single ply roofing membrane
exhibits a flame retardance rating of classification D as measured
in accordance with the EN ISO 11925-2 surface exposure test.
19. The method of claim 16, wherein the silane-grafted polyolefin
elastomer comprises a first polyolefin having a density less than
0.86 g/cm.sup.3, a second polyolefin, a silane crosslinker, a
grafting initiator.
20. The method of claim 16, wherein the high-load flame retardant
thermoplastic polyolefin (TPO) roofing membrane exhibits a
weathering color difference of from about 0.25 .DELTA.E to about
2.0 .DELTA.E, as measured according to ASTM D2244.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. 119(e) to
U.S. Provisional Patent Application No. 62/497,959, filed Dec. 10,
2016, entitled "HOSE, COMPOSITION INCLUDING SILANE-GRAFTED
POLYOLEFIN, AND PROCESS OF MAKING A HOSE," and 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," both of which are herein
incorporated by reference in their entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure generally relates to compositions
that may be used to form thermoplastic roofing membranes, and more
particularly, to silane-grafted polyolefin elastomer compositions
used to form thermoplastic roofing membranes and methods for
manufacturing these compositions and roofing membranes.
BACKGROUND OF THE DISCLOSURE
[0003] Thermoplastic roofing membranes may be a single layer or may
be composed of multiple layers and may contain a reinforcing fabric
or scrim reinforcement material in the center between any two of
the layers of the roofing membrane. Each of the respective layers
in the roofing membrane needs to demonstrate a variety of different
material properties in order to be suited for use on a roof where
the material will be exposed to the sun and the elements. The
material properties of the polymer layers should exhibit good
adhesion, UV resistance, weatherability (durability), flame
retardance, flexibility, chemical resistance and longevity. In
addition, roofing membranes should preferably be capable of forming
hot-air welded seams.
[0004] Many different polymer systems are available to be used for
roofing membranes. The most commonly used polymer systems include
thermoplastic polyolefin (TPO), ethylene propylene diene monomer
(EPDM), and polyvinyl chloride (PVC). Depending on the material(s)
selected, different advantages and disadvantages are typically
observed. TPO membranes are widely available, affordable, and
typically white, but are susceptible to deterioration when exposed
to high heat and/or solar UV radiation. EPDM membranes are made
from the readily available EPDM synthetic rubber, but roughly 95%
of all EPDM roofing membranes produced are black while federal and
state building regulators are starting to push for white roofing
membranes. Lastly, PVC membranes are widely available and offer
excellent puncture, heat-weldability, colorability, and heat
resistant qualities, but these membranes can be expensive to
manufacture and suffer from variability in properties as produced
by different manufacturers.
[0005] Mindful of the advantages and drawbacks for the various TPO,
EPDM, and PVC materials used to make roofing membranes,
manufacturers have a need for the development of new polymer
compositions and methods of making roofing membranes that are
simpler with less production variability, lighter in weight and
color, and have superior durability over a longer period of
time.
SUMMARY OF THE DISCLOSURE
[0006] According to one aspect of the present disclosure, a roofing
membrane is disclosed. The single ply roofing membrane includes a
top layer comprising a flame retardant and first silane-crosslinked
polyolefin elastomer having a density less than 0.90 g/cm.sup.3; a
scrim layer; and a bottom layer comprising a flame retardant and a
second silane-crosslinked polyolefin elastomer having a density
less than 0.90 g/cm.sup.3. The top and bottom layers of the roofing
membrane both 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.).
[0007] According to another aspect of the present disclosure, a
method of making a roofing membrane is provided. The method
includes: extruding a first silane-crosslinkable polyolefin
elastomer to form a top layer; extruding a second
silane-crosslinkable polyolefin elastomer to form a bottom layer;
calendaring a scrim layer between the top and the bottom layers to
form an uncured roofing membrane element; and crosslinking the
silane-crosslinkable polyolefin elastomers of the top and the
bottom layers in the uncured roofing membrane element at a curing
temperature and a curing humidity to form the roofing membrane. The
top and bottom layers of the roofing membrane both 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.).
[0008] According to a further aspect of the present disclosure, a
method of making a high-load flame retardant thermoplastic
polyolefin (TPO) roofing membrane is provided. The method includes:
adding a silane-grafted polyolefin elastomer, a fire retardant, and
a condensation catalyst to a reactive single screw extruder to
produce a silane-crosslinkable polyolefin elastomer; calendaring
the silane-crosslinkable polyolefin elastomer to form a top layer
and a bottom layer; calendaring a scrim layer between the top and
the bottom layers to form an uncured roofing membrane element; and
crosslinking the silane-crosslinkable polyolefin elastomers of the
top and the bottom layers in the uncured roofing membrane element
at an ambient temperature and an ambient humidity to form the
thermoplastic polyolefin (TPO) roofing membrane. The top and bottom
layers of the thermoplastic polyolefin (TPO) roofing membrane both
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.).
[0009] These and other aspects, objects, and features of the
present disclosure 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
[0010] In the drawings:
[0011] FIG. 1 is a cross-sectional view of a roofing membrane
according to some aspects of the present disclosure;
[0012] FIG. 2 is a schematic reaction pathway used to produce a
silane-crosslinked polyolefin elastomer according to some aspects
of the present disclosure;
[0013] FIG. 3 is a flow diagram of a method for making a single ply
roofing membrane with a silane-crosslinked polyolefin elastomer
using a two-step Sioplas approach according to some aspects of the
present disclosure;
[0014] FIG. 4A is a schematic cross-sectional view of a reactive
twin-screw extruder according to some aspects of the present
disclosure;
[0015] FIG. 4B is a schematic cross-sectional view of a
single-screw extruder according to some aspects of the present
disclosure;
[0016] FIG. 5 is a flow diagram of a method for making a single ply
roofing membrane with a silane-crosslinked polyolefin elastomer
using a one-step Monosil approach according to some aspects of the
present disclosure;
[0017] FIG. 6 is a schematic cross-sectional view of a reactive
single-screw extruder according to some aspects of the present
disclosure;
[0018] FIG. 7 is a graph illustrating the stress/strain behavior of
a silane-crosslinked polyolefin elastomer, according to aspects of
the disclosure, as compared to conventional EPDM compounds;
[0019] FIG. 8 is a relaxation plot of an exemplary
silane-crosslinked polyolefin elastomer, suitable for a roofing
membrane according to aspects of the disclosure, and comparative
EPDM cross-linked materials; and
[0020] FIG. 9 is a compression set plot of an exemplary
silane-crosslinked polyolefin elastomer suitable for a roofing
membrane, and a comparative EPDM cross-linked material.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0021] For purposes of description herein the terms "upper,"
"lower," "right," "left," "rear," "front," "vertical,"
"horizontal," and derivatives thereof shall relate to the roofing
membranes of the disclosure as shown in FIG. 1. However, it is to
be understood that the device 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.
[0022] 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/or values.
[0023] 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."
[0024] 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.
[0025] Referring to FIG. 1, a roofing membrane 10 is disclosed. The
roofing membrane 10 includes a top layer 14 having a flame
retardant and a first silane-crosslinked polyolefin elastomer with
a density less than 0.90 g/cm.sup.3; a scrim layer 26; and a bottom
layer 38 having a flame retardant and a second silane-crosslinked
polyolefin elastomer with a density less than 0.90 g/cm.sup.3. The
top and bottom layers of the roofing membrane both 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.).
[0026] A TPO roofing membrane must exhibit at least the following
mechanical properties as outlined by the ASTM specification for TPO
roofing membranes: 1) a tensile strength (CD and MD) greater than
10 MPa; 2) an elongation at break (CD and MD) greater than 500%; 3)
an elastic modulus (CD and MD) of less than 100 MPa; and 4) a flame
retardance rating of classification D as measured in accordance
with the EN ISO 11925-2 surface exposure test.
[0027] Referring again to FIG. 1, a cross-sectional view of the
single ply roofing membrane 10 is provided. The single ply roofing
membrane 10 includes the top layer 14 with a first and a second
surface 18, 22. The scrim layer 26 (also referred to as scrim 26)
has a third and a fourth surface 30, 34 where the third surface 30
of the scrim 26 is coupled to the second surface 22 of the top
layer 14. The single ply roofing membrane 10 additionally includes
a bottom layer 38 with a fifth and a sixth surface 42, 46, where
the fifth surface 42 of the bottom layer 38 is coupled to the
fourth surface 34 of the scrim 26. In some aspects, the roofing
membrane 10 may include the single ply roofing membrane, a double
ply roofing membrane, or a higher number of plies. Unless otherwise
denoted, roofing membrane 10 and single ply roofing membrane 10
both mean a single ply made from the top layer 14, scrim layer 26,
and bottom layer 38.
[0028] The scrim layer 26 disposed between the top and bottom
layers 14, 38 can serve as a reinforcement in the roofing membrane,
thus adding to its structural integrity. Materials that can be used
for the scrim layers 26 may include, for example, woven and/or
non-woven fabrics, fiberglass, and/or polyester. In some aspects,
additional materials that can be used for the scrim layers 26 can
include synthetic materials such as polyaramids, KEVLAR.TM.,
TWARON.TM., polyamides, polyesters, RAYON.TM., NOMEX.TM.,
TECHNORA.TM., or a combination thereof. In some aspects, the scrim
layer 26 may include aramids, polyamides, and/or polyesters. In
some aspects, a tenacity of the scrim layer 26 may range from about
100 to about 3000 denier. In other aspects, the scrim layers 26 may
have a tenacity ranging from about 500 to about 1500 denier. In
still other aspects, scrim layers 26 may have a tenacity of about
1000 denier. In some aspects, scrim layers 26 may have a tensile
strength of greater than about 14 kN per meter (80 pounds force per
inch). In other aspects, the scrim layers 26 may have a tensile
strength of greater than about 10 kN per meter, greater than about
15 kN per meter, greater than about 20 kN per meter, or greater
than about 25 kN per meter. Depending on the desired properties of
the final single ply roofing membrane 10, the scrim layers 26 may
be varied as needed to suit particular roofing membrane designs.
One of ordinary skill in the art would appreciate that such
characteristics can be varied without departing from the present
disclosure.
[0029] The single ply roofing membranes 10 disclosed herein may
have a variety of different dimensions. In some aspects, single ply
roofing membranes 10 may have a length from about 30 feet to about
200 feet and a width from about 4 feet to about 12 feet. In some
aspects, the roofing membranes 10 may have a width of about 10
feet. Variations in the width may provide for various advantages.
For example, in some aspects, roofing membranes 10 having smaller
widths may advantageously allow for greater ease in assembly of a
roofing structure. Smaller widths may also advantageously allow for
greater ease in rolling or packaging of a manufactured membrane.
Larger widths may advantageously allow for greater structure
integrity, fast installation and/or improve the stability of a
roofing structure comprising these membranes.
[0030] Numerous different flame retardants may be used in
combination with the first and second silane-crosslinkable
polyolefin elastomer employed in the top and bottom layers 14, 38
of the roofing membrane 10. For example, magnesium hydroxide may
provide flame retardant properties in the layers 14, 38. Magnesium
hydroxide may be extruded or blended with the silane-grafted
polyolefin elastomer to ensure complete dispersal in the
composition blend. In some aspects, the magnesium hydroxide is
blended with the silane-grafted polyolefin elastomer in an amount
up to 70 wt % magnesium hydroxide. In another exemplary embodiment,
the magnesium hydroxide in the silane-grafted polyolefin elastomer
can make up between about 20 wt % and 75 wt % of the roofing
membrane composition.
[0031] The disclosure focuses on the composition, method of making
the composition, methods of making roofing membranes with these
compositions, and the corresponding material properties for the
silane-crosslinked polyolefin elastomer used to make single ply
roofing membranes 10 (as depicted in FIG. 1), along with other
roofing membranes 10 consistent with the principles of this
disclosure. The roofing membrane 10 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
silane-crosslinked polyolefin elastomer or blend. In aspects, the
silane-crosslinked polyolefin elastomer or blend includes the first
polyolefin having a density less than 0.90 g/cm.sup.3, the second
polyolefin having a crystallinity of less than 40%, the silane
crosslinker, the graft initiator, and the condensation
catalyst.
First Polyolefin
[0032] 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.TM.
6102 grades (Exxon Mobil Chemical Company), TAFMER.TM. XM (Mitsui
Chemical Company), and VERSIFY.TM. (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 %.
[0033] 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 wt
%to about 12 wt % based on the weight of the polyolefin, including
from greater than 0 wt % to about 9 wt %, and from greater than 0
wt % 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.
[0034] 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 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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 wt
% 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 %.
[0039] 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.
[0040] 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.
[0041] 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.3 to about 0.89
g/cm.sup.3, from about 0.85 g/cm.sup.3 to about 0.88 g/cm.sup.3,
from about 0.84 g/cm.sup.3 to about 0.88 g/cm.sup.3, or from about
0.83 g/cm.sup.3 to 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.
[0042] 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
[0043] 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 %.
[0044] 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 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.3 to about
0.89 g/cm.sup.3, from about 0.85 g/cm.sup.3 to about 0.88
g/cm.sup.3, from about 0.84 g/cm.sup.3 to about 0.88 g/cm.sup.3, or
from about 0.83 g/cm.sup.3 to 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.
[0051] 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%.
[0052] As noted, the silane-crosslinked polyolefin elastomers or
blends, e.g., as employed in roofing membranes 10 (e.g., within the
top and bottom layers 14, 38 as shown in FIG. 1), 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.
[0053] 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.
[0054] 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-crosslinker polyolefin
elastomer/blend.
Grafting Initiator
[0055] 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-isopro-
pyl)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.).
[0056] 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.
[0057] 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 begins 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
[0058] 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.
[0059] 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.
[0060] 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.3 or
--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.
[0061] 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 or a 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
C.sub.2-6 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.
[0062] 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.
[0063] In some aspects, the alkylsilane compound may be selected
from triethoxyoctylsilane, trimethoxyoctylsilane, and a combination
thereof.
[0064] 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.
[0065] 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.
[0066] 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
[0067] 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 %, including from about 0.25 wt % to about 8 wt %,
based on the total weight of the silane-grafted polyolefin
elastomer/blend composition.
[0068] 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 %.
Optional Additional Components
[0069] 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.
[0070] With further regard to the fillers, 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.
[0071] The filler(s) of the 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 %.
[0072] The silane-crosslinked polyolefin elastomer and/or the
respective articles formed (e.g., single ply roofing membranes 10
as depicted in FIG. 1) 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 %.
[0073] 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-crosslinker 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 %.
[0074] In some aspects, the silane-crosslinker 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
%.
[0075] 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 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.
[0076] In some aspects, the silane-crosslinker polyolefin elastomer
of the present disclosure may include one or more stabilizers
(e.g., antioxidants). The silane-crosslinked polyolefin 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.
[0077] In some aspects, titanium dioxide, a white pigment, may be
added to the formulation to provide opacity and color. In addition,
the titanium dioxide also may provide ultraviolet light protection.
In some aspects, the titanium dioxide may be pre-blended with the
first and/or second polyolefins (of the type set forth above) to
ensure complete dispersal of the titanium dioxide throughout the
composition. In some aspects, to ensure complete dispersal of the
titanium dioxide into the composition prior to extrusion or other
formation techniques, the titanium dioxide may be pre-blended with
the first and/or second polyolefins in an amount up to 30 wt %, up
to 20 wt %, or up to 10 wt %.
Method for Making the Silane-Grafted Polyolefin Elastomer
[0078] The synthesis/production of the 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.
[0079] Referring now to FIG. 2, the general chemical process used
during both the single-step Monosil process and two-step Sioplas
process used to synthesize the silane-crosslinked polyolefin
elastomer 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.
[0080] Still referring to FIG. 2, 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.
[0081] Referring now to FIGS. 3 and 4A, a method 200 for making the
roofing membrane 10, using the two-step Sioplas process is shown.
The method 200 may begin with a step 204 that includes extruding
(e.g., with a twin screw extruder 252) a first polyolefin 240
having a density less than 0.86 g/cm.sup.3, a second polyolefin
244, and a silan cocktail 248 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 240 and second polyolefin
244 may be added to a reactive twin screw extruder 252 using an
addition hopper 256. The silan cocktail 248 may be added to the
twin screws 260 further down the extrusion line to help promote
better mixing with the blend of the first and second polyolefins
240, 244. A forced volatile organic compound (VOC) vacuum 264 may
be used on the reactive twin screw extruder 252 to help maintain a
desired reaction pressure. The twin screw extruder 252 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 240, 244. The melted
silane-grafted polyolefin blend can exit the reactive twin screw
extruder 252 using a gear pump 268 that injects the molten
silane-grafted polyolefin blend into a water pelletizer 272 that
can form a pelletized silane-grafted polyolefin blend 276. In some
aspects, the molten silane-grafted polyolefin blend 276 may be
extruded into pellets, pillows, or any other configuration prior to
the incorporation of the condensation catalyst 280 (see FIG. 4B)
and formation of the final article (e.g., a roofing membrane 10 as
depicted in FIG. 1).
[0082] The reactive twin screw extruder 252 can be configured to
have a plurality of different temperature zones (e.g., Z0-Z12 as
shown in FIG. 4A) that extend for various lengths of the twin screw
extruder 252. 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.; Z7 may have a temperature from about
150.degree. C. to about 160.degree. C.; and Z8-Z12 may have a
temperature from about 150.degree. C. to about 160.degree. C.
[0083] 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.
[0084] Referring now to FIGS. 3 and 4B, the method 200 next
includes a step 208 of extruding the silane-grafted polyolefin
blend 276 and the condensation catalyst 280 together to form a
silane-crosslinkable polyolefin blend 298. In some aspects, one or
more optional additives 284 may be added with the silane-grafted
polyolefin blend 276 and the condensation catalyst 280 to adjust
the final material properties of the silane-crosslinkable
polyolefin blend 298. In step 208, the silane-grafted polyolefin
blend 276 is mixed with a silanol forming condensation catalyst 280
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 280 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 280 to crosslink the silane-crosslinkable
polyolefin blend 298 over a longer time period (e.g., about 48
hours). The silane-grafted polyolefin blend 276 and the
condensation catalyst 280 may be added to a reactive single screw
extruder 288 using an addition hopper (similar to addition hopper
256 shown in FIG. 4A) and an addition gear pump 296. The
combination of the silane-grafted polyolefin blend 276 and the
condensation catalyst 280, and in some aspects one or more optional
additives 284, may be added to a single screw 292 of the reactive
single screw extruder 288. The single screw extruder 288 is
considered reactive because the silane-grafted polyolefin blend 276
and the condensation catalyst 280 are melted and combined together
to mix the condensation catalyst 280 thoroughly and evenly
throughout the melted silane-grafted polyolefin blend 276. The
melted silane-crosslinkable polyolefin blend 298, as formed in step
208, can exit the reactive single screw extruder 288 through a die
that can inject the molten silane-crosslinkable polyolefin blend
298 into the form of an uncured roofing membrane element.
[0085] During step 208, as the silane-grafted polyolefin blend 276
is extruded together with the condensation catalyst 280 to form the
silane-crosslinkable polyolefin blend 298, a certain amount of
crosslinking may occur. In some aspects, the silane-crosslinkable
polyolefin blend 298 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 silane-crosslinked polyolefin
elastomer.
[0086] Referring to FIGS. 3 and 4B, the method 200 further includes
a step 212 of extruding and/or calendaring the silane-crosslinkable
polyolefin elastomer or blend 298 to form the top and bottom layers
14, 38, as comprising the uncured silane-crosslinkable polyolefin
elastomer. The silane-crosslinkable polyolefin elastomer or blend
298 is in a melted or molten state where it can flow and be shaped
as it exits the reactive single screw extruder 288. A calendar
system 302 is a device having two or more rollers (the area between
the rollers is called a nip) used to process the melted
silane-crosslinkable polyolefin elastomer blend 298 into a sheet or
film. As the melted silane-crosslinkable polyolefin elastomer blend
298 leaves the reactive single screw extruder 288, it forms a pool
of silane-crosslinkable polyolefin elastomer 306 at a first nip
point of the calendar system 302. The pool of silane-crosslinkable
polyolefin elastomer 306 is then pressed or rolled into the top or
bottom layer 14, 38 respectively. The scrim layer 26 may be added
to the top or bottom layer 14, 38, respectively, at any point
during the calendaring process using a scrim roll 318. The scrim
layer 26, as coupled to the top or bottom layer 14, 38, forms a
partial scrim membrane 322. The partial scrim membrane 322 may be
further calendared and pressed with the respectively missing top or
bottom layer 14, 38 to form the uncured roofing membrane
element.
[0087] Referring again to FIG. 3, the method 200 can further
include a step 216 of crosslinking the silane-crosslinkable
polyolefin blend 298 or the roofing membrane element in an uncured
form at an ambient temperature and/or an ambient humidity to form
the roofing membrane 10 (see FIG. 1) having a density from about
0.85 g/cm.sup.3 to about 0.89 g/cm.sup.3. More particularly, in
this crosslinking process, the water hydrolyzes the silane of the
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.
[0088] The crosslinking/curing of step 216 of the method 200 (see
FIG. 3) 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%.
[0089] 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%.
[0090] In some aspects, one or more reactive single screw extruders
288 may be used to form the uncured roofing membrane element (and
corresponding single ply roofing membrane 10) that has one or more
types of silane-crosslinked polyolefin elastomers. For example, in
some aspects, one reactive single screw extruder 288 may be used to
produce and extrude a first silane-crosslinked polyolefin elastomer
associated employed in a top layer 14 of a roofing membrane 10 (see
FIG. 1), while a second reactive single screw extruder 288 may be
used to produce and extrude a second silane-crosslinked polyolefin
elastomer employed in a bottom layer 38 of the roofing membrane 10.
The complexity, architecture and property requirements of the
roofing membrane 10 will determine the number and types of reactive
single screw extruder 288 necessary to fabricate it.
[0091] It is understood that the prior description outlining and
teaching the various roofing membranes 10, and their respective
components and compositions, can be used in any combination, and
applies equally well to the method 200 for making the roofing
membrane 10 using the two-step Sioplas process as shown in FIGS. 3,
4A and 4B.
[0092] Referring now to FIGS. 5 and 6, a method 400 for making the
roofing membrane 10 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 444) the first polyolefin 240
having a density less than 0.86 g/cm.sup.3, the second polyolefin
244, the silan cocktail 248 including the silane crosslinker (e.g.,
vinyltrimethoxy silane, VTMO) and grafting initiator (e.g. dicumyl
peroxide), and the condensation catalyst 280 together to form the
crosslinkable silane-grafted polyolefin blend 298. The first
polyolefin 240, second polyolefin 244, and silan cocktail 248 may
be added to the reactive single screw extruder 444 using an
addition hopper 440. In some aspects, the silan cocktail 248 may be
added to a single screw 448 further down the extrusion line to help
promote better mixing with the first and second polyolefin 240, 244
blend. In some aspects, one or more optional additives 284 may be
added with the first polyolefin 240, second polyolefin 244,
condensation catalyst 280 and silan cocktail 248 to adjust the
final material properties of the silane-crosslinkable polyolefin
blend 298. The single screw extruder 444 is considered reactive
because the grafting initiator and silane crosslinker of the silan
cocktail 248 are reacting with and forming new covalent bonds with
both the first and second polyolefins 240, 244. In addition, the
reactive single screw extruder 444 mixes the condensation catalyst
280 in together with the melted silane-grafted polyolefin blend
comprising the first and second polyolefins 240, 244, silan
cocktail 248 and any optional additives 284. The resulting melted
silane-crosslinkable polyolefin blend 298 can exit the reactive
single screw extruder 444 using a gear pump (not shown) and/or die
that can eject the molten silane-crosslinkable polyolefin blend 298
into the form of an uncured roofing membrane element.
[0093] During step 404, as the first polyolefin 240, second
polyolefin 244, silan cocktail 248, and condensation catalyst 280
are extruded together, a certain amount of crosslinking may occur
in the reactive single screw extruder 444 to the
silane-crosslinkable blend 298. In some aspects, the
silane-crosslinkable polyolefin blend 298 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 444.
The gel test (ASTM D2765) can be used to determine the amount of
crosslinking in the final silane-crosslinked polyolefin
elastomer.
[0094] The reactive single screw extruder 444 can be configured to
have a plurality of different temperature zones (e.g., Z0-Z7 as
shown in FIG. 6) 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.
[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 to FIGS. 5 and 6, the method 400 further includes
a step 408 of extruding and/or calendaring the silane-crosslinkable
polyolefin elastomer or blend 298 to form the top and bottom layers
14, 38, as comprising the uncured silane-crosslinkable polyolefin
elastomer. The silane-crosslinkable polyolefin elastomer or blend
298 is in a melted or molten state where it can flow and be shaped
as it exits the reactive single screw extruder 444. As previously
mentioned, the calendar system 302 is a device having two or more
rollers (the area between the rollers is called a nip) used to
process the melted silane-crosslinkable polyolefin elastomer blend
298 into a sheet or film. As the melted silane-crosslinkable
polyolefin elastomer blend 298 leaves the reactive single screw
extruder 444, it forms a pool of silane-crosslinkable polyolefin
elastomer 306 at a first nip point of the calendar system 302. The
pool of silane-crosslinkable polyolefin elastomer 306 is then
pressed or rolled into the top or bottom layer 14, 38,
respectively. The scrim layer 26 may be added to the top or bottom
layer 14, 38 respectively at any point during the calendaring
process using a scrim roll 318. The scrim layer 26, as coupled to
the top or bottom layer 14, 38, forms a partial scrim membrane 322.
The partial scrim membrane 322 may be further calendared and
pressed with the respectively missing top or bottom layer 14, 38 to
form an uncured roofing membrane element.
[0097] Still referring to FIG. 5, the method 400 can further
include a step 412 of crosslinking the silane-crosslinkable
polyolefin blend 298 of the uncured roofing membrane element at an
ambient temperature and an ambient humidity to form the element
into the roofing membrane 10 (see FIG. 1) having a density from
about 0.85 g/cm.sup.3 to about 0.89 g/cm.sup.3. The amount of
crosslinked silane groups, and thus the final polymer properties of
the roofing membrane 10, can be regulated by controlling the
production process, including the amount of catalyst used.
[0098] The step 412 of crosslinking the silane-crosslinkable
polyolefin blend 298 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%.
[0099] 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%.
[0100] In some aspects, one or more reactive single screw extruders
444 may be used to form the roofing membrane 10 that has one or
more types of silane-crosslinked polyolefin elastomers. For
example, in some aspects, one reactive single screw extruder 444
may be used to produce and extrude a first silane-crosslinked
polyolefin elastomer associated with the top layer 14 of the
roofing membrane 10 (see FIG. 1), while a second reactive single
screw extruder 444 may be used to produce and extrude a second
silane-crosslinked polyolefin elastomer associated with the bottom
layer 38 of the roofing membrane 10. The complexity, architecture
and required properties of the final roofing membrane 10 will
determine the number and types of reactive single screw extruders
444 employed according to the method 400 depicted in FIG. 5.
[0101] It is understood that the prior description outlining and
teaching of the various roofing membranes 10, and their respective
components and compositions, can be used in any combination, and
applies equally well to the method 400 for making the roofing
membrane 10 using the one-step Monosil process as shown in FIGS. 5
and 6.
Silane-Crosslinked Polyolefin Elastomer Physical Properties
[0102] 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 silane-crosslinked polyolefin elastomer or roofing
membrane 10. Each of the intermediate polymer materials mixed and
reacted using a reactive twin screw extruder, and/or a reactive
single screw extruder are thermosets. Accordingly, the
silane-grafted polyolefin blend 276 and the silane-crosslinkable
polyolefin blend 298 are thermoplastics and can be softened by
heating so the respective materials can flow. Once the
silane-crosslinkable polyolefin blend 298 is extruded, molded,
pressed, and/or shaped into the uncured roofing membrane element or
other respective article, the silane-crosslinkable polyolefin blend
298 can begin to crosslink or cure at an ambient temperature and an
ambient humidity to form the roofing membrane 10 (or other end
product form), as comprising one or more silane-crosslinked
polyolefin blends.
[0103] The thermoplastic/thermoset behavior of the
silane-crosslinkable polyolefin blend 298 and corresponding
silane-crosslinked polyolefin blend are important for the various
compositions and articles disclosed herein (e.g., roofing membrane
10 shown in FIG. 1) 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 298 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 298. The ability to cure
the inventive silane-crosslinkable polyolefin blend 298 with
ambient temperature and/or ambient humidity is not a capability
necessarily intrinsic to crosslinkable polyolefins. Rather, this
capability or property is dependent on the relatively low density
of the silane-crosslinkable polyolefin blend 298. 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 silane-crosslinked polyolefin
elastomers.
[0104] The specific gravity of the 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 facilitating additional ease-of-assembly for
roofers and other individuals charged with installing the roofing
membranes 10 of the disclosure. For example, the specific gravity
of the silane-crosslinked polyolefin elastomer of the present
disclosure may be from about 0.80 g/cm.sup.3 to about 1.50
g/cm.sup.3, from about 1.25 g/cm.sup.3 to about 1.45 g/cm.sup.3,
from about 1.30 g/cm.sup.3 to about 1.40 g/cm.sup.3, about 1.25
g/cm.sup.3, about 1.30 g/cm.sup.3, about 1.35 g/cm.sup.3, about
1.40 g/cm.sup.3, about 1.45 g/cm.sup.3, about 1.50 g/cm.sup.3, less
than 1.75 g/cm.sup.3, less than 1.60 g/cm.sup.3, less than 1.50
g/cm.sup.3, or less than 1.45 g/cm.sup.3, as compared to
conventional TPV materials which may have a specific gravity
greater than 2.00 g/cm.sup.3and conventional EPDM materials which
may have a specific gravity of from 2.0 g/cm.sup.3 to 3.0
g/cm.sup.3.
[0105] The stress/strain behavior of an exemplary
silane-crosslinked polyolefin elastomer of the present disclosure
(i.e., "silane-crosslinked polyolefin elastomer") relative to two
existing EPDM materials is provided. In particular, FIG. 7 displays
a smaller area between the stress/strain curves for the
silane-crosslinked polyolefin of the disclosure (labeled as "Silane
Cross-linked Polyolefin Elastomer" in FIG. 7), as compared to the
areas between the stress/strain curves of EPDM compound A and EPDM
compound B. This smaller area between the stress/strain curves for
the silane-crosslinked polyolefin elastomer can be desirable for
roofing membranes 10. 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
filler 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.
[0106] The silane-crosslinked polyolefin elastomer or roofing
membrane 10 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.).
[0107] In other implementations, the silane-crosslinked polyolefin
elastomer or roofing membrane 10 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.).
[0108] The silane-crosslinked polyolefin elastomer or roofing
membrane 10 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.
[0109] The silane-crosslinked polyolefin elastomer or roofing
membrane 10 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.
[0110] The silane-crosslinked polyolefin elastomer or roofing
membrane 10 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. In some embodiments, the roofing membrane
10 may be a high-load flame retardant thermoplastic polyolefin
(TPO) having the above weathering properties.
EXAMPLES
[0111] The following non-limiting examples are provided as
exemplary embodiments to further outline aspects of the
disclosure.
Materials
[0112] All chemicals, constituents and precursors were obtained
from commercial suppliers and used as provided without further
purification.
Example 1
Preparation of the Silane-Grafted Polyolefin Elastomer
[0113] Example 1 (Ex. 1) or ED76-4A was produced by extruding 82.55
wt % ENGAGE.TM. 8842 and 14.45 wt % MOSTEN.TM. TB 003 together with
3.0 wt % SILAN RHS 14/032 or SILFIN 29 to form a silane-grafted
polyolefin elastomer, according to one of the foregoing methods
outlined in the disclosure. The Example 1 silane-grafted polyolefin
elastomer was then extruded using various condensation catalysts
and fillers to form a silane-crosslinkable polyolefin elastomer, as
suitable for top and bottom layers 14, 38 of a roofing membrane (as
described below in Example 2). The composition of the Example 1
silane-grafted polyolefin elastomer is provided in Table 1
below.
TABLE-US-00001 TABLE 1 Ingredients Example 1 ENGAGE 8842 82.55
MOSTEN TB 003 14.45 SILFIN 29 3.00 TOTAL 100
Example 2
Preparation of the Roofing Membrane
[0114] In this example, identical top and bottom layers 14, 38 were
used to produce an embodiment of a single ply roofing membrane 10.
In particular, the top and bottom layers 14 38 were produced by
extruding 29.0 wt % silane-grafted polyolefin elastomer (from
Example 1) and 70.0 wt % vinyl silane coated magnesium dihydroxide,
Mg(OH).sub.2 (MDH), together with 1.0 wt % dioctyltin dilaurate
(DOTL) condensation catalyst to form a silane-crosslinkable
polyolefin elastomer blend. The blend was then extruded and
calendared to provide the respective top and bottom layers 14, 38
of an uncured roofing membrane element. The silane-crosslinkable
polyolefin elastomer of the layers 14, 38 of the uncured roofing
membrane element was then cured at ambient temperature and humidity
to form the roofing membrane 10. The composition of the roofing
membrane 10 formed in this example is provided in Table 2
below.
Example 3
Preparation of the Roofing Membrane
[0115] In this example, identical top and bottom layers 14, 38 were
used to produce another embodiment of a single ply roofing membrane
10. In particular, the top and bottom layers 14, 38 were produced
by extruding 29.0 wt % silane-grafted polyolefin elastomer (from
Example 1) and 70.0 wt % stearic acid coated magnesium dihydroxide,
Mg(OH).sub.2 (MDH), together with 1.0 wt % dioctyltin dilaurate
(DOTL) condensation catalyst to form a silane-crosslinkable
polyolefin elastomer blend. The blend was then extruded and
calendared to provide the respective top and bottom layers 14, 38
of an uncured roofing membrane element. The silane-crosslinkable
polyolefin elastomer of the layers 14, 38 of the uncured roofing
membrane element was then cured at ambient temperature and humidity
to form the roofing membrane 10. The composition of the roofing
membrane 10 formed in this example is also provided in Table 2
below.
TABLE-US-00002 TABLE 2 Comparison of Roofing Membranes Vinyl Silane
Stearic Acid DOTL ED 76-4A coated MDH coated MDH Catalyst Example
Sample (wt %) (wt %) (wt %) (wt %) Example 2 Top Layer 29 70 -- 1
Example 2 Bottom 29 70 -- 1 Layer Example 3 Top Layer 29 -- 70 1
Example 3 Bottom 29 -- 70 1 Layer
[0116] Referring now to FIG. 8, the thermal stability of Example 1
is provided with respect to a comparative EPDM peroxide crosslinked
resin and a comparative EPDM sulfur crosslinked resin. As shown,
Example 1 can retain nearly 90% of its elastic properties at
150.degree. C. for greater than 500 hrs. The retention of elastic
properties as provided in Example 1 is representative of each of
the inventive silane-crosslinked polyolefin elastomers disclosed
herein. The roofing member made from these silane-crosslinked
polyolefin elastomers may retain up to 60%, 70%, 80%, or 90% of its
elastic properties as determined by using Stress Relaxation
measurements at 150.degree. C. for greater than 100 hrs, greater
than 200 hrs, greater than 300 hrs, greater than 400 hrs, and
greater than 500 hrs.
[0117] Referring now to FIG. 9, the compression set values are
provided across a time period of 4,000 hrs for Ex. 1 that
demonstrates the superior long term retention of elastic properties
of the silane-crosslinked polyolefin elastomer material used to
make the roofing membrane 10. As provided, the Ex. 1
silane-crosslinked polyolefin elastomer material maintains a
compression set of 35% or lower as measured according to ASTM D 395
(30% @ 110.degree. C.). The ability of these silane-crosslinked
polyolefin elastomer materials used in roofing membranes 10 to
retain its elasticity (compression set %) over a long period of
time upon exposure to heat that simulates exterior weathering or
aging is provided by this representative example of these roofing
membrane 10 materials.
[0118] 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.
[0119] 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.
[0120] 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.
[0121] The above description is considered that of the illustrated
embodiments only. 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
[0122] Embodiment A is a roofing membrane comprising: a top layer
comprising a flame retardant and a first silane-crosslinked
polyolefin elastomer having a density less than 0.90 g/cm.sup.3; a
scrim layer; and a bottom layer comprising a flame retardant and a
second silane-crosslinked polyolefin elastomer having a density
less than 0.90 g/cm.sup.3, wherein the top and bottom layers of the
single ply roofing membrane both 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.).
[0123] The roofing membrane of Embodiment A wherein the compression
set is from about 10% to about 30%.
[0124] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first and second
silane-crosslinked polyolefin elastomers both exhibit a
crystallinity of from about 5% to about 25%.
[0125] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first and second
silane-crosslinked polyolefin elastomers have a glass transition
temperature of from about -75.degree. C. to about -25.degree.
C.
[0126] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first and second
silane-crosslinked polyolefin elastomers each comprise a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
[0127] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the density is from about
0.85 g/cm.sup.3 to about 0.89 g/cm.sup.3.
[0128] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the single ply roofing
membrane exhibits a weathering color difference of from about 0.25
.DELTA.E to about 2.0 .DELTA.E, as measured according to ASTM
D2244.
[0129] The roofing membrane of Embodiment A or Embodiment A with
any of the intervening features wherein the first
silane-crosslinked polyolefin elastomer and the second
silane-crosslinked polyolefin elastomer are chemically distinct
from each other.
[0130] Embodiment B is a method of making a roofing membrane, the
method comprising: extruding a first silane-crosslinkable
polyolefin elastomer to form a top layer; extruding a second
silane-crosslinkable polyolefin elastomer to form a bottom layer;
calendaring a scrim layer between the top and the bottom layers to
form an uncured roofing membrane element; and crosslinking the
silane-crosslinkable polyolefin elastomers of the top and the
bottom layers in the uncured roofing membrane element at a curing
temperature and a curing humidity to form the single ply roofing
membrane, wherein the top and bottom layers of the single ply
roofing membrane both 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.).
[0131] The method of Embodiment B wherein the first
silane-crosslinkable polyolefin elastomer and the second
silane-crosslinkable polyolefin elastomer are chemically distinct
from each other.
[0132] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the curing temperature is an ambient
temperature.
[0133] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the curing humidity is an ambient
humidity.
[0134] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the first and second
silane-crosslinkable polyolefin elastomers each comprise a first
polyolefin having a density less than 0.86 g/cm.sup.3, a second
polyolefin, a silane crosslinker, a grafting initiator, and a
condensation catalyst.
[0135] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the single ply roofing membrane
exhibits a weathering color difference of from about 0.25 .DELTA.E
to about 2.0 .DELTA.E, as measured according to ASTM D2244.
[0136] The method of Embodiment B or Embodiment B with any of the
intervening features wherein the single ply roofing membrane
exhibits a flame retardance rating of classification D as measured
in accordance with the EN ISO 11925-2 surface exposure test.
[0137] Embodiment C is a method of making a high-load flame
retardant thermoplastic polyolefin (TPO) roofing membrane, the
method comprising: adding a silane-grafted polyolefin elastomer, a
flame retardant, and a condensation catalyst to a reactive single
screw extruder to produce a silane-crosslinkable polyolefin
elastomer; calendaring the silane-crosslinkable polyolefin
elastomer to form a top layer and a bottom layer; calendaring a
scrim layer between the top and the bottom layers to form an
uncured roofing membrane element; and crosslinking the
silane-crosslinkable polyolefin elastomers of the top and the
bottom layers in the uncured roofing membrane element at an ambient
temperature and an ambient humidity to form the thermoplastic
polyolefin (TPO) roofing membrane, wherein the top and bottom
layers of the thermoplastic polyolefin (TPO) roofing membrane both
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.).
[0138] The method of Embodiment C wherein the top and bottom layers
are chemically equivalent to each other.
[0139] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the single ply roofing membrane
exhibits a flame retardance rating of classification D as measured
in accordance with the EN ISO 11925-2 surface exposure test.
[0140] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the silane-grafted polyolefin
elastomer comprises a first polyolefin having a density less than
0.86 g/cm.sup.3, a second polyolefin, a silane crosslinker, a
grafting initiator.
[0141] The method of Embodiment C or Embodiment C with any of the
intervening features wherein the high-load flame retardant
thermoplastic polyolefin (TPO) roofing membrane exhibits a
weathering color difference of from about 0.25 .DELTA.E to about
2.0 .DELTA.E, as measured according to ASTM D2244.
* * * * *