U.S. patent application number 09/873729 was filed with the patent office on 2001-10-04 for method and apparatus for selectively curing a sheet of epdm material.
Invention is credited to Hubbard, Michael J., Kelly, Walter J., Verrocchi, Anthony, Weinert, Raymond J..
Application Number | 20010027224 09/873729 |
Document ID | / |
Family ID | 22730585 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010027224 |
Kind Code |
A1 |
Hubbard, Michael J. ; et
al. |
October 4, 2001 |
Method and apparatus for selectively curing a sheet of EPDM
material
Abstract
A method and apparatus for selectively curing a sheet of
ethylene-propylene diene termonomer (EPDM) material to form a
roofing membrane for installation on a roof deck. The method
includes the steps of providing a sheet formed of
ethylene-propylene diene termonomer, the sheet having a field and
longitudinal edge areas bordering the field; and then
simultaneously shielding at least one edge area of the EPDM sheet
and exposing at least the field to a source of radiation to cure at
least the field of the EPDM sheet and provide a selectively cured
EPDM roofing membrane. Also disclosed is the product formed by the
method of the present invention.
Inventors: |
Hubbard, Michael J.;
(Holland, OH) ; Kelly, Walter J.; (Wadsworth,
OH) ; Verrocchi, Anthony; (Akron, OH) ;
Weinert, Raymond J.; (Macedonia, OH) |
Correspondence
Address: |
Robert F. Rywalski
Omnova Solutions Inc.
175 Ghent Road
Fairlawn
OH
44333-3300
US
|
Family ID: |
22730585 |
Appl. No.: |
09/873729 |
Filed: |
June 4, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09873729 |
Jun 4, 2001 |
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09197742 |
Nov 20, 1998 |
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Current U.S.
Class: |
522/184 ;
264/340; 425/500 |
Current CPC
Class: |
Y10T 428/24355 20150115;
B29C 35/0266 20130101; B29C 2035/0822 20130101; B29K 2023/16
20130101; B29C 35/0805 20130101; Y10T 428/24405 20150115; B32B
2419/06 20130101; B32B 2250/24 20130101; B32B 25/042 20130101; E04D
5/06 20130101; B29C 35/0894 20130101; B32B 27/16 20130101 |
Class at
Publication: |
522/184 ;
425/500; 264/340 |
International
Class: |
B32B 031/00; C08F
002/46; B29B 015/00; B29D 009/00 |
Claims
What is claimed is:
1. A method for selectively curing a sheet of ethylene-propylene
diene termonomer (EPDM) material to form a roofing membrane for
installation on a roof deck comprising the steps of: providing a
sheet formed of ethylene-propylene diene ternonomer, the sheet
having a field and two longitudinal edge areas bordering the field;
and simultaneously shielding at least one edge area of the EPDM
sheet and exposing at least the field to a source of radiation to
cure at least the field of the EPDM sheet and provide a selectively
cured EPDM roofing membrane.
2. The method of claim 1 wherein the sheet is provided by milling,
calendering or extrusion.
3. The method of claim 1 wherein the sheet is from 5 to 200 mils
thick.
4. The method of claim 1 wherein two longitudinal edge areas of the
EPDM sheet are shielded.
5. The method of claim 1 wherein the at least one longitudinal edge
area of the EPDM sheet is shielded by operatively projecting at
least one screen over the at least one longitudinal edge area of
the sheet and shield the edge area of the sheet of EPDM.
6. The method of claim 1 wherein two longitudinal edge areas of the
EPDM sheet are shielded by operatively projecting a screen over
each longitudinal edge area of the sheet thereby shielding the edge
area of the sheet of EPDM.
7. The method of claim 1 wherein the source of radiation is
infrared radiation.
8. An apparatus for selectively curing a sheet of
ethylene-propylene diene termonomer (EPDM) material, the sheet
having a field and longitudinal edge areas bordering the field, the
apparatus comprising: a curing oven having a roof and a floor
interconnected by sidewalls, a front end and a back end, the front
end including an entrance and the back end including an exit, a
conveyor positioned between the front end and the back end of the
curing oven for continuously conveying the sheet of EPDM through
the curing oven; a radiation source located above the conveyor
within the curing oven; and at least one screen operatively
projecting from each sidewall of the curing oven and extending the
longitudinal length of the curing oven to cover at least one edge
area of the sheet and shield the edge area of the sheet of EPDM as
the sheet passes through the curing oven under the radiation
source.
9. The apparatus of claim 8 wherein the screen is a flat,
rectangular shape radiation reflective material.
10. The apparatus of claim 8 wherein the curing oven includes an
actuating member to operatively position the screen between an
extended position over the edge area of the sheet of EPDM to a
retracted position.
11. The apparatus of claim 10 wherein the actuating member includes
a piston member and an arm attached to the screen.
12. The apparatus of claim 8 wherein the radiation source provides
a desired dose of high-energy radiation to cure at least the
exposed field of the sheet of EPDM.
13. The apparatus of claim 12 wherein the radiation source is
selected from infrared radiation, gamma rays, x-rays, or beta
rays.
14. The apparatus of claim 12 wherein the radiation source includes
an array of infrared heat lamps positioned above the conveyor
within the curing oven.
15. A method of joining selectively cured sheets of EPDM membrane
comprising the steps of: providing at least two sheets formed of
ethylene-propylene diene termonomer, the sheets having a field
defined by a cured planar surface portion and a noncured
longitudinal edge area bordering the field defined by the extent of
overlap of adjacent roofing membranes when installed on a roof
deck; and then overlapping and pressing the noncured edge areas of
two EPDM roofing membranes together and then vulcanizing the edge
areas to splice the edge areas together.
16. A roofing membrane comprising: a sheet formed of
ethylene-propylene diene termonomer (EPDM) material, the sheet
having a field defined by a cured planar surface portion and a
noncured longitudinal edge area bordering the field and defined by
the extent of overlap of adjacent roofing membranes when installed
on a roof deck.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a method and apparatus for
selectively curing a sheet of ethylene-propylene diene termonomer
(EPDM) material and the product formed thereby. More particularly,
this invention relates to a method and apparatus for selectively
curing at least the field portion of a sheet of EPDM material for
use as a roofing membrane and to a method of joining the roofing
membranes and the product formed thereby.
BACKGROUND OF THE INVENTION
[0002] EPDM membranes are used as a single ply roofing material for
industrial and commercial flat roofs. Such membranes are generally
applied to the roof surface in a vulcanized or cured state. Because
of outstanding weather resistance and flexibility, cured EPDM
roofing membrane material has rapidly gained acceptance. The
material is typically prepared by vulcanizing the composition in
the presence of sulfur or sulfur containing compounds such as
mercaptans or by using radiation cross linking promoters in the
EPDM material which can be cured by ionizing radiation, for
example, see U.S. Pat. No. 4,803,020, incorporated herein by
reference.
[0003] Notwithstanding the usefulness of radiation curing and
sulfur curing of a sheet of EPDM, a disadvantage of utilizing EPDM
material is the lack of adhesion of cured EPDM to itself
Accordingly, it is usually necessary to splice the cured EPDM
roofing membranes together with an adhesive to bond the cured EPDM
membranes together to form a continuous EPDM membrane to cover the
roof. It will be appreciated that the use of an adhesive for
splicing cured EPDM membranes together requires that the adhesive
and the resulting bond must meet a number of requirements which are
extremely difficult to satisfy. The adhesive must provide
sufficient seam peel and shear strength to permit the splice formed
by bonding the cured EPDM membranes together to resist both the
short-term and long-term stresses experienced by the spliced EPDM
roofing membrane.
[0004] In view of the foregoing, it is an object of the present
invention to provide a method and apparatus for selectively curing
only the field of a sheet of EPDM. It is another object of the
present invention to provide a method and apparatus for selectively
curing only the field of a sheet of EPDM with radiation, preferably
infrared radiation, and to a method of joining at least two
selectively cured EPDM membranes to form a larger membrane. Yet
another object of the present invention is to provide a method of
splicing selectively cured EPDM membranes having a cured field and
uncured longitudinal edge area which eliminates the need for a
solvent based or non-solvent based splicing adhesive along the
overlapping edge area and the related labor and hardware necessary
for mixing and application thereof. It is another object of the
present invention to provide a method and apparatus for curing only
the field of a sheet of EPDM that is simple and economical.
SUMMARY OF THE INVENTION
[0005] Briefly, according to the present invention there is
provided a method and apparatus for selectively curing a sheet of
EPDM to form a roofing membrane for installation on a roof deck.
The method includes the steps of providing a sheet formed of
ethylene-propylene diene termonomer, the sheet having a field and
longitudinal edge portions bordering the field. The field is
defined by a planar surface portion exclusive of the longitudinal
edge portions. The longitudinal edge portions are defined by the
extent of overlap of adjacent roofing membranes when installed on a
roof deck. The sheet is then selectively cured such that at least
only the field is cured thereby leaving at least one longitudinal
edge portion of the sheet uncured.
[0006] The apparatus for selectively curing a sheet of
ethylene-propylene diene termonomer (EPDM) defined by a field and
longitudinal edge areas bordering the field includes a curing oven,
a radiation source and at least one screen. The curing oven has a
roof and a floor interconnected by sidewalls, a front end and a
back end. The front end includes an entrance and the back end
includes an exit. A conveyor is positioned between the front end
and the back end of the curing oven for continuously conveying the
sheet of EPDM through the curing oven. The radiation source is
located above the conveyor within the curing oven. At least one
screen operatively projects from each sidewall of the curing oven
and extends the longitudinal length of the curing oven to cover at
least one edge area of the sheet and shield the edge area of the
sheet of EPDM as the sheet passes through the curing oven under the
radiation source.
[0007] The resulting roofing membrane from the process of the
present invention is a sheet formed of ethylene-propylene diene
termonomer. The sheet has a field defined by a cured planar surface
portion and at least one noncured longitudinal edge area bordering
the field and defined by the extent of overlap of adjacent roofing
membranes when installed on a roof deck.
[0008] The selectively cured sheets of EPDM membrane may be joined
by providing at least two sheets formed of ethylene-propylene diene
termonomer, the sheets having a field defined by a cured planar
surface portion and at least one noncured longitudinal edge area
bordering the field defined by the extent of overlap of adjacent
roofing membranes when installed on a roof deck. The noncured edge
areas of two EPDM roofing membranes are then overlapped and pressed
together and then the edge areas are vulcanized to splice the edge
areas together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Further features and other objects and advantages of this
invention will become clear from the following detailed description
made with reference to the drawings in which:
[0010] FIG. 1 is a perspective view of the apparatus for
selectively curing a sheet of EPDM;
[0011] FIG. 2 is an end view of the apparatus of FIG. 1; and
[0012] FIG. 3 is a partial end view of the apparatus of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] Referring to the figures, wherein like reference characters
represent like elements there is shown an apparatus for selectively
curing a sheet of EPDM to form a roofing membrane for installation
on a roof deck. The sheet includes a field and longitudinal edges
bordering the field. The term "field" refers to the planar surface
center area of the sheet of EPDM that is adjacent the longitudinal
edge area of the membrane that forms the splice. It will be
appreciated that the longitudinal edge area that forms the splice
may extend 2-3 inches from the edge of the sheet of EPDM. The term
"EPDM" is intended to mean a terpolymer of ethylene-propylene and
diene monomer. Illustrative methods for preparing such terpolymers
are found in U.S. Pat. No. 3,280,082, the disclosure of which is
incorporated herein by reference. The preferred polymers have from
about 60 to about 95 weight percent ethylene and from about 0 to
about 12 weight percent, preferably about 4 to about 6 weight
percent of the diene with the balance of the polymer being
propylene or some other similar olefin type polymer.
[0014] The diene monomer utilized in forming the EPDM terpolymer is
preferably a non-conjugated diene. Illustrative examples of
non-conjugated dienes which may be employed are dicyclopentadiene,
alkyldicyclopentadiene, 1,4-pentadiene, 1,4-hemadiene,
1,5hexadiene, 1,4-heptadiene, 2-methyl-1,5-hexadiene,
cyclooctadione, 1,4-octadiene, 1,7-octadiene,
5-ethylidene-2-nor-bornene, 5-n-propylidene-2-norbornene,
5-(2-methyl-2-butenyl)-2-norbornene and the like. A typical EPDM is
Vistalon.RTM. MD-744 (Exxon Chemical Co.) a terpolymer having a
Mooney Viscosity (ML/4 at 125 C.) of about 52; an
ethylene/propylene (E/P) ratio of 61/39 weight percent and about
2.7 weight percent of unsaturation.
[0015] Particularly useful and preferred in preparing a sulfur
curable EPDM composition is Royalene.RTM. 3180 (Uniroyal Chemical
Co.) which has a Mooney Viscosity (ML/4 at 120.degree. C.) of about
54; an ethylene/propylene ratio of about 67/33 weight percent;
about 2.2 weight percent of unsaturation
(5-ethylidene-2-norbornene); about 2.7 percent by weight of
crystallinity and a weight average molecular weight of
approximately 313,000 to 355,000. Also useful are thermoplastic
heat seamable sheeting materials, i.e., EPDM's having a high degree
of crystallinity as opposed to amorphous (non-crystalline) EPDM's.
Examples thereof include Royalene.RTM. 375 (Uniroyal Chemical Co.);
and EPsyn.RTM. 5508.
[0016] The composition employed to form the sheeting material
comprises 100 parts by weight of EPDM or other similar olefinic
type polymers, including mixtures of two or more types, to which
are added fillers and processing materials as well as curatives as
well known in the art. The curatives include, for example, organic
polyamines, organic polyacids, organic polyesters, organic
polyanhydrides, organic polysulfides and precursors thereof.
[0017] With respect to the fillers, suitable fillers are selected
from the group consisting of reinforcing and non-reinforcing
materials, and mixtures thereof, as are customarily added to
rubber. Examples include such materials as carbon black, ground
coal, calcium carbonate, clay, silica, cryogenically ground rubber
and the like. Preferred fillers include carbon black, ground coal
and ground recycled rubber or cryogenically ground rubber. Carbon
black is used in an amount of about 20 parts to about 300 parts per
100 parts of polymer (phr), preferably about equal to the amount or
carbon black normally used in preparing sulfur cured EPDM roof
sheeting. The carbon black useful herein is any carbon black.
Preferred are furnace blacks such as GPF (general purpose furnace),
FEF (fast extrusion furnace) and SRF (semi-reinforcing
furnace).
[0018] The ground coal employed as a filler in the compositions of
the invention is a dry, finely divided black powder derived from a
low volatile bituminous coal. The ground coal has a particle size
ranging from a minimum of 0.26 microns to a maximum of 2.55 microns
with the average particle size of 0.69.+-.0.46 as determined on 50
particles, using Transmission Electron Microscopy. The ground coal
produces an aqueous slurry having a pH of about 7.0 when tested in
accordance with ASTM D-15 12. A preferred ground coal of this type
is designated Austin Black which has a specific gravity of
1.22.+-.0.03, an ash content of 4.58% and a sulfur content of
0.65%. Austin Black is commercially available from Coal Fillers,
Inc., P.O. Box 1063, Bluefield, Va. Amounts range from about 5 to
65 p.about. with about 15 to 35 being preferred.
[0019] Finally, essentially any ground recycled rubber may be
employed as a filler in the composition of the invention. The
preferred ground recycled rubbers are cryogenically ground EPDM,
butyl, neoprene and the like. A preferred cryogenically ground
rubber is a cryogenically ground EPDM rubber. The preferred
cryogenically ground EPDM rubber is a fine black rubbery powder
having a specific gravity of 1.129.+-.0.015 and a particle size
ranging from about 30 to about 300 microns with an average particle
size ranging from about 50 to about 80 microns. Amounts range from
about 5 to 40 phr with about 10 to 25 phr being preferred.
[0020] Mixtures of Austin black and cryogenically ground rubber
useful herein may be utilized as a partial replacement for carbon
black. Where mixtures of these two fillers are employed the
relative amounts thereof can be widely varied; the overall total
not exceeding about 60 phr. The ratio of Austin black to
cryogenically ground rubber may range from a desired ratio of 2:1
to perhaps even a ratio of 3:1. Again, as noted hereinabove, other
filler materials can be employed. Amounts of these filler materials
fall within the range of amounts normally employed in preparing
sulfur cured conventional roof sheeting.
[0021] With respect to the processing material, it is included to
improve the processing behavior of the composition (i.e. reduce
mixing time and increase rate of sheet forming and includes
processing oils, waxes and the like). The processing oil is
included in an amount ranging from about 20 parts to about 150
parts process oil per 100 parts EPDM ingredient phr, preferably in
an amount ranging from about 60 to about 100 phr. A preferred
processing oil is a paraffinic oil, e.g. Sunpar 2280 which is
available from the Sun Oil Company. Other petroleum derived oils
including naphtheuic oils may be used.
[0022] Optional ingredients include, for example, other elastomers
(e.g., butyl elastomer, neutralized sulfonated EPDM, neutralized
sulfonated butyl) in place of minor amounts of the EPDM, secondary
inorganic fillers (e.g., talc, mica, clay, silicates, whiting) with
total secondary filler content usually ranging from about 10 to
about 150, about 0.3 to 2 phr. It is a feature of the present
invention that the roof sheeting compound is selectively cured
prior to application.
[0023] The compounding ingredients can be admixed, utilizing an
internal mixer (such as a Banbury mixer), an extruder, and/or a
two-roll mill, or other mixers suitable for forming a viscous
relatively uniform admixture. When utilizing a type B Banbury
internal mixer, in a preferred mode, the dry or powdery materials
such as carbon black are added first followed by the liquid process
oil and finally the polymer (this type of mixing can be referred to
as an upside-down mixing technique).
[0024] The resulting admixture is continuously sheeted to a
thickness ranging from 5 to 200 mils, preferably from 35 to 60
mils, by conventional sheeting methods, for example, milling,
calendering or extrusion. Preferably, the admixture is sheeted to
at least 40 gauge (0.040 inches) which is the minimum thickness
specified in standards set by the Roofing Council of the Rubber
Manufacturers Association for non-reinforced black EPDM rubber
sheets for use in roofing applications. In many cases, the
admixture is sheeted to 40-45 gauge thickness since this is the
thickness for a large percentage of "single-ply" roofing membranes
used commercially.
[0025] Referring to FIGS. 1-3, the apparatus 10 includes a curing
oven 12 having a radiation source 14 and at least one screen 16. It
will be appreciated that most any suitable curing oven design may
be used to selectively cure at least the field of a sheet 18 of
EPDM. The curing oven 12 may be formed of most any suitable
material to withstand the high temperatures experienced in the
curing oven. In a preferred embodiment, the curing oven 12 includes
a means to continuously convey the sheet 18 of EPDM through the
oven, a radiation source 14 and a screen 16 to shield at least a
portion of the radiation from the sheet 18 of EPDM.
[0026] The apparatus 10 includes a curing oven 12 having a roof 20
and a floor 22 interconnected by sidewalls 24, a front end 26 and a
back end 28. The front end 26 of the curing oven 12 includes an
entrance 30 and the back end 28 of the curing oven includes an exit
32. Positioned between the front end 26 and the back end 28 of the
curing oven 12 is an endless conveyor 34 of a type well known in
the art for continuously conveying the sheet 18 of EPDM through the
curing oven. Operatively projecting from each sidewall 24 of the
curing oven 12 is at least one screen 16. The screen 16 may extend
the longitudinal length of the curing oven 12 or a plurality of
screens may project from each sidewall to form a continuous shield
as further described herein. The screen 16 is a flat, rectangular
shape radiation reflective material of a type well known in the art
to cover the edge area 36 of the sheet 18 of EPDM forming the
splice. The screen 16 acts to shield the edge area 36 of the sheet
18 of EPDM as the sheet passes through the curing oven 12 under the
radiation source 14. In a preferred embodiment, the curing oven 12
includes an actuating member 38 to operatively position the screen
16 between an extended position over the edge area 36 of the sheet
18 of EPDM as shown in FIG. 1 to a retracted position as shown in
FIG. 3. The actuating member 38 includes a piston member and an arm
attached to the screen. However, it will be appreciated that the
actuating member 38 may be most any suitable mechanical linkage of
a type well known in the art to move the screen 16 from an extended
position to a retracted position and back.
[0027] Located above the conveyor 34 within the curing oven 12 is a
radiation source 14. The radiation source 14 provides a desired
dose of high-energy radiation to cure at least the exposed field 40
of the sheet 18 of EPDM. Typically, useful high-energy sources of
radiation include infrared radiation, gamma rays, x-rays, beta rays
and the like. In a preferred embodiment, the radiation source 14
includes an array of infrared heat lamps of a type well known in
the art located above the conveyor 34 within the curing oven 12.
The intensity of the high energy radiation must be sufficient to
crosslink the polymers within the sheet 18. Preferably, the
intensity of the high energy radiation must be such that that the
surface temperature of the sheet 18 is at least about 204.degree.
C.
[0028] In operation, the sheet 18 of EPDM is conveyed from a roller
head die extruder 42 or similar device to manufacture the sheet, to
the curing oven 12. The sheet 18 of EPDM then enters the entrance
30 of the front end 26 of the curing oven 12 and is conveyed
through the curing oven beneath the radiation source 14. At least
one, and preferably two, of the screens 16 are positioned above the
edge areas 36 of the sheet of EPDM to shield the area. The
radiation source 14 continuously cures at least the field 40 of the
sheet 18 of EPDM as the sheet is conveyed through the curing oven
12. The selectively cured sheet 18 of EPDM exits the back end 28 of
the curing oven 12 to a take-up roll as well known in the art.
[0029] The selectively cured sheet 18 of EPDM forming a roofing
membrane may be spliced together by overlapping and pressing the
noncured edge areas 36 of two EPDM roofing membranes together and
then vulcanizing the edge areas to splice the edge areas together.
It will be appreciated that by selectively curing at least the
field 40 of the sheet 18 of EPDM, the EPDM roofing membranes may be
spliced together without using an adhesive.
[0030] The patents and documents described herein are hereby
incorporated by reference.
[0031] Having described presently preferred embodiments of the
invention, the invention may be otherwise embodied within the scope
of the appended claims.
* * * * *