Note: Descriptions are shown in the official language in which they were submitted.
20~9104
POLYVINYL CHLORIDE MEMlBRANE COMPOSlTION
AND METHOD FOR MAKING A
POLYVINYL CHLORIDE MEMBRANE
TECHNICAL FIELD
This invention generally relates to polyvinyl chloride compositions. More
particularly, the present invention relates to po~yvinyl chloride compositions useful for
l0 making a membrane. Specifically, the present invention relates to polyvinyl chloride
membrane compositions having a unique plasticizer system which substantially prevents
migration of the plasticizers from the membrane.
BACKGROUND OF THE INVENTION
lS It is known in the art to provide roofing membranes formed from a polyvinylchloride (hereinafter "PVC") resin composition. It is also known that the PVC resin
should be plasticized in order to render it flexible for its intended purpose. It has been
found that commonly used liquid plasticizers in PVC roofing membrane compositions
will often migrate from the PVC and into adjacent material layers, such as insulation,
20 backing, coatings or the like. Furthermore, the plasticiær will often migrate to the
surface of the membrane where it evaporates or is washed away by the weather. When
the plasticiær migrates from the PVC composition, the membrane becomes stiff and is
subject to shrinking and cracking.
In thepast, solutions to membrane shrinkage have included, for example, the
25 incorporation of highly elastic polyurethane as the main component in the membrane
composition. Unfortunately, polyurethane in such an application is very expensive.
One example of forming a "dimensionally stable" i.e., s~ resistant PVC
membrane composition is disclosed in U.S. Pat. No. 4,358,499. The PVC membrane
therein is formed by casting and gelling a plastisol layer, casting and gelling a second
30 plastisol layer thereon, and fusing the two layers. The plastisol includes PVC, a
plasticizer such as a diaLkyl phtha1ate, an emulsifier, a filler, and heat, processing and
UV stabilizers. It has been found, however, that without the complex plastisol casting
method of the invention in that patent, PVC membrane compositions which include
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plasticizers such as phthalate plasticizers, will result in membranes wherein the phthalate
migrates out of the PVC, resulting in shrinkage and cracking of the membrane over
periods of time.
However, phthalate plasticizers are known to effectively and efficiently
5 plasticize the PVC for roofing membrane applications. Therefore, a nesd exists for a
phthalate plasticiæd PVC roofing membrane composition, which possesses an increased
resistance to plasticizer migration from the PV~, and which is, therefore, resistant to
shrinkage and cracking caused thereby. Also, a useful membrane composition should
be highly resistant to ultraviolet light degradation and temperature fluctuation10 degradation.
j
SUMMARY OF INVEN~ON
It is therefore, an object of the present invention to provide a plasticized
polyvinyl chloride roofing membrane composition.
15It is another object of the present invention to provide a composition as
above, which when employed to form a membrane, is resistant to migration of the
plasticizers therein.
It is yet another object of the present invention to provide a roofing
membrane which is resistant to shrinking and cracking.
20It is still another object to provide a roofing membrane which is highly
resistant to ultraviolet light degradation.
It is yet another object to provide a roofing membrane which is resistant to
heat degradation.
It is a further object of the present invention to provide a method for forming
25a roofing membrane.
It is a still further object of the present invention to provide a method for
forming a roofing membrane which is resistant to shrinkage and weathering degradation.
At least one or more of the foregoing objects, together with the advantages
thereof over the known art relating to roofing membranes and compositions therefor,
30which shall become apparent from the specification which follows, are accomplished by
the invention as hereinafter described and claimed.
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In general, a polymer composition useful as a roofing membrane, according
to the present invention comprises (a) a polyvinyl chloride resin; (b) a carbon
monoxide/ethylene/vinyl acetate terpolymer plasticizer for (a); and (c) a phthalate
plasticizer for (a). The ratio of the plasticizers (b) to (c) is from about l.5 to 2.5:1.
There is also provided according to the present invention, a roofing
membrane which comprises a first layer and a second layer. The first layer is formed
from a polymer composition which comprises~-(a) a polyvinyl chloride resin; (b) a
carbon monoxide/ethylene/vinyl acetate terpolymer plasticizer for (a); and, (c) a
phthalate plasticizer for (a). The ratio of the plasticizers (b) to (c) is from about l.5 to
2.5:I by weight. The second layer comprises a fabric backing material.
A method of forming a roofing membrane comprises the step of forming a
membrane composition. The membrane composition comprises (a) a polyvinyl chloride
resin; (b) a carbon monoxide/ethylene/vinyl acetate terpolymer plasticizer for (a); and,
(c) a phthalate plasticizer for (a). The ratio of plasticizers (b) to (c), is from about 1.5
to 2.5:1 by weight. The method alsa includes the step of coating the membrane
composition onto a fabric backing material.
PREFERRED EMBODIMENT F~R CARRYING OUT-TIIE INVENIION
As will become apparent from the description which follows, the present
invention provides a novel composition useful for forming a membrane, and a novel
method for forming a roofing membrane. Membranes formed according to the presentinvention have increased resistance to,shrinking and cracking caused by plasticizer
migration. The membranes a1so exhibit increased resistance to ultraviolet light and other
weather induced degradation.
It has also been unexpectedly found, that compositions and membranes
according to the present invention, have increased compatibility with polystyrene
materials, such as Styrofoam brand insulation available from the Dow Chemical
Company, and AMOCOR-PB4 protection board from AMOCO Foam Products.
The present invention is directed toward a polymeric membrane and a
30 composition therefor. While the invention is useful in any application wherein a
membrane is re~uired, it has particular application to membranes used to provide
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weathering protection to roofs or the like. Hence, while all membrane applications are
within the scope of the invention, the present disclosure will make reference to roofing
applications for exemplary purposes only.
Similarly, the present invention has application to a variety of membrane
5 composition polymers. However, PVC resin is the preferred membrane polymer. Anexample of a useful PVC resin is Geon 30 available from B.F. Goodrich. Other PVCresins may also be useful, as will be apparent ~om the discussion to follow.
As noted hereinabove, when properly plasticized, PVC possesses excellent
membrane forming characteristics, such as structural integrity and weather resistance.
10 The drawback heretofore has been in regard to the migration of the plasticizer from the
PVC after a period of time.
According to the present invention, the PVC resin is plasticized with a
phthalate type, liquid plasticizer, such as Palatinol 711P from BASF Wyandotte Corp.
of Parsippany, New Jersey. Palatinol 711P is known to be based upon C7 to Cll
15 alcohols. Liquid phthalate plasticizers are known to effectively plasticize PVC resins
in a manner suitable for membrane applications. Other useful phthalate plasticizer
include diisodecylphthalate types.
- The composition of the present invention also includes a carbon
monoxide/ethylenelvinyl acetate terpolymer plasticizer for the PVC resin. An example
20 of such a terpolymer is Elvaloy 741 from DuPont, which has a molecular weight greater
than about 250,000. It has been found, that when the terpolymer is employed in a ratio
with the phthalate plasticizer, of from about 1.5 to 2.5:1 to 1, and more preferably at
a ratio of about 2:1, the resulting plasticized PVC composition shows improved
resistance to plasticizer migration. As will be further exemplified hereinbelow,25 membranes formed from such a composition uill possess resistance to shrinkage and
cracking.
When employing a PVC resin such as Geon 30, which is known to have a
molecular weight of about 65,000 and an inherent viscosity of 1.02 according to ASTM
D1243, the composition preferably includes from about 30 to about 60 parts by weight
30 of the carbon monoxide/ethylenelvinyl acetate terpolymer, per 100 parts by weight of
PVC resin (hereinafter referred to às "phrn). Furthermore, the composition preferably
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includes from about 15 to about 30 phr of the phthalate plasticiær. As will be
appreciated by one skilled in the membrane art, when a PVC resin having a different
molecular weight is employed, which resin would have a different inherent viscosity,
different amounts of the two types of plasticiærs might be employed in order to provide
5 a suitably plasticiæd composition. Such amounts might also vary depending upon the
nature of the membrane to be formed. All sueh compositions, having the plasticiær
amounts in the prescribed ratios, are within the~scope of the present invention.The carbon monoxide/ethylene/vinyl acetate terpolymer is less stable when
exposed to ultraviolet (hereinafter referred to as "UVn) light radiation than most PVC
10 resins. Hence, it has been found that compositions according to the present invention
may be provided with UV-protecting filler or pigments. As an example, a useful
composition according to the present invention, employing a PVC resin such as Geon
30, includes from about 15 to about 25 phr of titanium dioxide. This provides
unexpectedly high UV protection for membranes according to the present invention.
Compositions according to the invention may also contain other conventional
additives, such as processing aids or the like. For example, the compositions may
include other fillers such as calcium carbonate; heat stabiliærs such as barium/zinc;
lubricants such as stearic acid; acid acceptors such as epoxidized soybean oil; other W-
protectors such as substituted hydroxyphenyl benzotriazole; antioxidants; biocides; anti-
20 slipping agents; and the like.
An exemplary formulation according to the present invention is listed in
Table I hereinbelow.
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TABLE I
EXEMPLARY FORMULATION
Component Amounta
Geon 30b 100
Plasticizer for Polyvinyl ChlorideC 45
Titanium Dioxide ~ 25
Phthalate Plasticizerd 20
Calcium Carbonate Filler 10
Epoxidized Soybean Oil S
Barium/Zinc Heat Stabilizere 3
Stearic Acid 0.5
UV Stabilizerf 0.5
Antioxidant 0.5
Biocide 1.5
Kemamide Eg 0.2
Advawax 280h 0.1
a) parts per 100 parts of the polyvinyl chloride component
20 b) polyvinyl chloride from BF Goodrich
c) such as a carbon monoxide/ethylene/vinyl acetate terpolymer, for example,
Elvaloy 741 from DuPont
d) Palatinol 711 P from BASF
e) Mark 4737 from Witco Chemical Corp., New York
25 f) Tinuvin 622 from Ciba-Geigy, a substituted hydroxyphenyl benzotrazole
g) anti-slip agent from Witco Chemical Corp., New York
h) anti-blocking agent from Carlisle Chemical Works, Brunswick, New Jersey
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While it is understood that other additives such as processing aids are
optional, and that amounts of each component may vary with the type of PVC resinemployed, Table II lists exemplary useful ranges of each component, if employed. It
is also understood that the actual components listed are examples of numerous such
5 components useful in the practice of the present invention, and that amounts of the
components may vary other than as listed hereinbelow, depending upon the actual
component employed.
TABLE II
COMPOSITION RANGES
Componenti PHR RangeJ
Polyvinyl Chloride 100
Plasticizer for Polyvinyl Chloride 30 - 60
Titanium Dioxide15 - 25
Phthalate Plasticizer 15 - 30
Calcium Carbonate FiUer 0 - 15
Epoxidized Soybean Oil 4 - 6
Barium/Zinc Heat Stabilizer 2 - 4
Stearic Acid 0.25 - 1.0
UV Stabilizer0.2 - 0.6
Antioxidant 0.2 - 0.6
Biocide 1 - 2
Anti-Slip Agent0.2 - 0.4
AntiblockAgent0.1 - 0.2
i) for an explanation of components, see Table I
j) parts per 100 parts of the polyvinyl chloride component
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As noted hereinabove, the compositions according to the present invention
are useful for forming membranes such as for roofing applications or the like. Any
method known in the art for forming membranes or sheeting from plasticized polymer
,- compositions is considered to be within the scope of the present invention.
5For example, the component ingredients can be admixed, utilizing an internal
mixer (such as a Banbury mixer), an extruder, and/or a two-roll mill, or other mixer
suitable for forming a viscous relatively unifor~ admixture. The resulting admixture
is then sheeted to thicknesses ranging preferably from about 5 to 200 mils, and more
preferably from about 35 to 100 mils, by conventional sheeting methods, for example,
10milling, calendaring, or extrusion. The sheeting can be cut to desired length and width
dimensions at this time.
The present invention has particular application to multi-ply roofing
membranes which include a first layer formed from a composition as discussed
hereinabove, coated onto a backing layer such as a fabric material. A second layer of
15a membrane according to the present invention may be bonded to the fabric backing
material, such that the fabric backing material is sandwiched between two layers of the
invention composition.
Preferably, the fabric backing or reinforcing material is a "mesh" type
material, such as 62006 from Highland Industries, Inc., of Westwood, New Jersey.20This material is fabricated from a yarn made from polyester filaments, at 1000 denier.
General Experimental
In order to demonstrate the effectiveness of the present invention in
25accomplishing the objectives thereof, a composition according to the present invention,
and containing the ingredients as in Table I listed hereinabove, was tested employing a
QW Weatherometer, as manufactured by Q-Panel. The device was run at 70C using
UVB-313 bulbs for 8 hrs/50C condensate for four hours, repetitive for 5,000 hours of
total exposure. For comparison, similar Weatherometer tests were conducted upon
30commerciatly available roofing membranes including UltraPly 78+ available from the
Assignee of record; Fibretite available from Seaman Corp., Sarasota, Florida; Sarnafil
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available from Sarnafil, Inc., Canton, Massachusetts; Trocal SR-60 available from Huls
America, Piscataway, New Jersey; and, Genflex available from Gencorp Polymer
Products, Toledo, Ohio.
The Weatherometer tests simulated weather conditions and specificaUy,
S ultraviolet exposure for the various membranes. The membranes were then examined
under magnification for cracking therein. The results of the experiments are listed in
Table III hereinbelow.
TABLE m
WEATHERING TEST
Membrane Result
Inventionk No cracks visible
UltraPly 78+ No cracks visible
Fibretite Cracks visiblel
Sarnafil Cracks visiblem
Trocal SR-60 Cracks visiblem
Genflex Cracks visiblem
20 k) a composition according to Table I hereinabove
1) at 30 power magnification
- . m) at 7 power magnification
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Thus, it has been shown, that the composition according to the present
invention performs as well as the best performing commercial membrane evaluated in
this weathering test, and is therefore, clearly useful in forming a membrane composition
which is resistant to migration of the plasticizers therein. The membrane is useful, as
5 for example, a roofing membrane, because of its particular resistance to shrinking and
cracking, when compared to other commercially avai1able membranes. Also, the
present invention has greater resistance to ~IJV induced degradation than many
commercially used membrane compositions.
The tests performed herein are for exemplary purposes only and do not
10 necessary limit the scope of the present invention. Furthermore, it is to be understood
that the invention is not limited to these specific polyvinyl chloride resins, terpolymers,
or phthalate plasticizers as noted hereinabove. Furthermore, the composition according
to the present invention may comprise various other additives and processing aids
without departing from the scope of the invention. Those skilled in the art may readily
15 select other polymers, plasticizers, and the like according to the disclosure made
hereinabove. Similarly, the invention is not necessarily limited to the particular methods
of forming a membrane as exemplified hereinabove.
Thus, it is believed that any of the variable disclosed herein can readily be
determined and controlled without departing from the scope of the invention herein
20 disclosed and described. Moreover, the scope of the invention shall include all
modifications and variations that fall within the scope of the attached claims.
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