WO2021007648A1

WO2021007648A1 - Polymeric membrane with graphene

Info

Publication number: WO2021007648A1
Application number: PCT/CA2020/000089
Authority: WO
Inventors: Vincent Philippe GUILLETTE
Original assignee: Solmax International Inc.
Priority date: 2019-07-17
Filing date: 2020-07-17
Publication date: 2021-01-21

Abstract

A geomembrane including an extruded polymeric layer including graphene and a stabilizer adapted to suppress polymer oxidation.

Description

POLYMERIC MEMBRANE WITH GRAPHENE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

MICROFICHE/COPYRIGHT REFERENCE

[0003] Not Applicable.

FIELD OF THE INVENTION

[0004] The present invention generally relates to geomembranes comprising one or more layers.

BACKGROUND OF THE INVENTION

[0005] Synthetic membranes, such as geomembranes and geosynthetics, are used around the globe in containment applications. They are commonly used to contain contaminants generated, for example, by the exploitation of mines, waste management, and petrochemistry. They may also be used to impound water or as structural barriers, among many other applications. [0006] Membrane integrity is key to environmental protection for multiple applications such as mining, waste management and aquaculture, to name a few. Such geomembranes are typically made from relatively thin continuous polymeric sheets.

[0007] Multilayered coextruded geomembranes have been developed and are known in the art. United States Patent No. US 5,221,570 discloses a geomembrane comprising three or more polymeric layers with outside layers consisting of high density polyethylene of at least 0.930 g/cm³ and a very low density polyethylene inner core layer that is less than or equal to 0.920 g/cm³, providing geomembranes exhibiting enhanced flexibility, ease of handling and welding that is superior to both high density polyethylene and low density polyethylene.

[0008] Such liner systems often comprise (from top to bottom) a gravel leachate collection layer, a geotextile protection layer, a 1.5-2 mm thick HDPE geomembrane, and either a geosynthetic clay liner (GCL) or a compacted clay liner. HDPE geomembranes have been shown to have good chemical resistance to the wide range of contaminants found in landfill leachate constituents. The long-term behaviour of geomembranes in landfill-based liners is initially controlled by the rate of extraction of antioxidants. This process involves the dissolution or chemical reaction of antioxidants at the surface of the geomembrane and their diffusion from the core structure to the surface due to concentration gradient. The loss of antioxidants leaves the geomembrane vulnerable to the second principal degradation mechanism of oxidative degradation (Rowe R. K. et a/.; Journal of geotechnical and geoenvironmental engineering (ASCE) 1090-0241 (2008) 134:1 (68)). [0009] United States Patent Application No. US 2014/0364545 Al describes a specific high temperature geomembrane liner and masterbatch composition made of additives such as: antioxidants (Irganox™ 1330; Irganox™ 1010; Irgafos™ 168), UV stabilizers (Hindered amine), acid neutralizer (hydrotalcite) and carbon black. These additives are well known for manufacturing pipes from polyolefin that are resistant to degradation (see, e.g., International Patent Publication No. WO 2008/040482; or other polyolefin articles such as geomembranes (see, for example, U.S. Patent No. US 6,774,170 B2 by Webster).

[0010] Chinese Patent Application No. CN 108342010A, International Patent Publication Nos. WO 2016/171615 A1 and WO 2014//144139 A1, United States Patent Publication Nos. US 2016/0122497 A1 and US 2017/0320303 and U.S. Patent Nos. 7,829,622, 10,150,850, 10,429,268, 10,488,293, 10,538,384 and 10,570,621 also disclose membranes and polymers for a variety of purposes.

[0011] High temperatures accelerate the degradation of membranes. Moreover, geomembrane mechanical properties degrade over time due to oxidation initiated from energy sources such as elevated temperatures and UV radiation. Stabilization systems (/.e., stabilizing additives or stabilizers) are commonly added to polymer geomembranes to intercept the oxidation reaction with the polymer.

[0012] Addition of stabilizers can minimize or eliminate the degradation of the geomembrane’s mechanical properties by interrupting the oxidation process. However, while stabilizers are consumed or depleted as they interrupt the oxidation process of geomembranes, the primary causes of stabilizer depletion are UV rays, the surrounding air, water, or other chemicals which extract the stabilizers from the geomembrane at a much faster rate than they are consumed by geomembrane protection. Thus, stabilizer systems preferably should not only provide protection from oxidation depletion but also protect against extraction of the protection (stabilizers) by physical means such as UV rays, air, etc.

[0013] There are two ASTM testing protocols which test stabilizer suitability (Oxidative Induction Time [OIT]):

a. ASTM D 3895 - 14 (Standard Test Method for Oxidative-Induction Time of Polyolefins by Differential Scanning Calorimetry)

b. ASTM D 5885 - 06 (Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by High-Pressure Differential Scanning Calorimetry).

[0014] The two tests essentially differ in that the ASTM D5885 test is conducted at a lower temperature (150 degrees C) with elevated pressures relative to the ASTM D3895 test. The tests involve placing a small sample of the material in an apparatus that measures heat and energy, with the apparatus then heated and oxygen introduced into the system whereby the sample material begins to oxidize, suppressed by the stabilization system. Eventually the stabilizers are completely consumed, whereby the material sample begins to combust, and additional energy is given off.

[0015] Early in the industry’s history, the stabilization system used was a combination of hindered phenolic stabilizers (referred to as primary antioxidants) and phosphate compounds (referred to as secondary antioxidants). The quantity of stabilizers present in the various geomembrane materials of this type could be accurately measured with ASTM 3895.

[0016] In the 1990’s, Hindered amines (sometimes called HALS, or Hindered Amine Light Stabilizers), a new type of stabilizer, was found to improve the performance and durability of geomembranes. However, because HALS are active from low temperatures to 150 degrees C, the existing laboratory test (ASTM 3895) did not do a good job of measuring stabilizer levels of HALS systems because the HALS and the byproducts that HALS produce while performing their stabilization function have a tendency to evaporate and volatize during the OIT testing which is conducted at artificially elevated temperatures (200 degrees C). Because there was a very poor correlation between the OIT (ASTM 3895) results, the level of HALS present in the geomembrane, and the actual performance of the materials, this issue was addressed by ASTM 5885 wherein the pressure within the test vessel is increased.

[0017] Geomembranes having stabilization systems which resist oxidation for a longer period of time such as may be demonstrated by such tests will have extended lives, including in projects that have harsh chemical and / or temperature conditions. However, if the stabilizers are not resistant to extraction by physical means, then it does not matter how well the stabilizer resists oxidation because it will end up being removed by physical extraction before it can protect the geomembrane. The OIT retention rate defines how well the stabilization system will defend against oxidation and physical extraction in laboratory accelerated age testing. The higher the retention rate, the more resistant that stabilization system is to physical extraction by these processes, and the longer the mechanical properties of the geomembrane are protected.

SUMMARY OF THE INVENTION

[0018] The present invention relates to a new geomembrane including graphene and a method of manufacturing a membrane in order to include graphene particles in any polymeric membrane.

[0019] In one aspect of the disclosure, graphene particles are added to at least one polymeric layer of the membrane.

[0020] In a further aspect of the disclosure, the graphene content in the membrane is between approximately 1 % and 20 % (by weight).

[0021] In yet another aspect of the disclosure, the membrane is at least one layer of polymeric material, each layer being made from, but not limited to, a given amount of a polypropylene (PP), polyethylene (PE) or polyvinyl chloride (PVC) masterbatch composition comprising a resin and additives, wherein graphene particles are included as an additive to at least one of the membrane layers.

[0022] In a further aspect of the disclosure, geomembranes according to the invention may be made by mixing a masterbatch composition comprising a resin and additives including graphene and extruding the masterbatch to form a single layer membrane layer. Alternatively, the graphene may be sprayed onto the membrane layer during or after the extrusion step. [0023] In another aspect of the disclosure, the method comprises co-extruding at least two polymeric layers, wherein graphene particles are added to at least one polymeric layer. In an alternative to this aspect, graphene particles may be sprayed onto the membrane during the manufacturing process.

[0024] Other and further aspects and advantages of the present invention will be better understood upon reading of the illustrative embodiments about to be described and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

[0025] Other objects, features, and advantages of the invention will become apparent from a review of the entire specification, including the appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A is a cross-sectional illustration of a geomembrane installed in an example geotechnical site wherein the geomembrane is under a fill material;

[0027] Figure 1 B is a partial perspective view of a multi-layer membrane with one membrane layer being as described herein; and

[0028] Figures 2A to 2D are tables showing ASTM 3895 and ASTM 5885 test results for sample membranes of K306 polyethylene resin including 0.5%, 1.5%, 2% and 5% graphene, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] An improved stabilized polymeric geomembrane having improved life is described herein.

[0030] The terminology used herein is in accordance with definitions set out below.

[0031] As used herein, “% (by weight)” refers to weight % as compared to the total weight percent of the phase or composition that is being discussed.

[0032] By "about",“approximate” or“approximately”, it is meant that the value of % (by weight), time, pH or temperature can vary within a certain range depending on the margin of error of the method or device used to evaluate such % (by weight), time, pH or temperature. A margin of error of 10% is generally accepted.

[0033] For purposes of this application, the terms “membrane” or “polymeric membrane" include a liner, sheet, layer or any other material generally corresponding to a membrane, as would be understood by one of skill in the art.

[0034] Also for purposes of this application, the term “graphene” means any suitable form of graphene, including without limitation, graphene particles, nanoparticles, nanofillers, nanocomposites, nanoplates, graphene nanoplatelets (GNPs), graphene powder, graphene oxide (GO), reduced graphene oxide (rGO), and any other material generally corresponding to graphene, as would be understood by one of skill in the art. Graphene nanoplatelets (GNPs) often represent the final form of graphene that is used as an additive in the manufacture of material composites. Graphene may also be dispersed in a polymeric matrix which may then be used to produce advanced composites or films.

[0035] In one aspect of the disclosure herein, a geomembrane membrane with stabilizer additives includes at least one layer of a polymeric material including stabilizers and graphene.

[0036] Fig. 1A illustrates an example use of a geomembrane 10 according to the present invention at a geotechnical site, where the membrane 10 includes stabilizing additives and graphene 14 (see Fig. 1 B). In such an example use, the membrane 10 may be advantageously laid over a containment area 16 and, commonly, covered with material 18.

[0037] The membrane 10 may have one or more layers, with Fig. 1 B showing by way of example a membrane 10 with three layers 10a, 10b, 10c, with stabilizers and graphene 14 included in one or more sheets (one of the layers 10a in the Fig. 1 B example). (Note that discrete visible particles 14 are shown in Fig. 1 B for illustration purposes, though in application such particles 14 only be powder particles may not be so discretely visible.) Multilayer membranes are known in the art, such as illustrated in Patent Application No. US 2017/0320303, the full disclosure of which is hereby incorporated by reference in its entirety.

[0038] ASTM 3895 and ASTM 5885 testing such as illustrated in Figs. 2A-2D demonstrate the advantage of including graphene in a stabilized membrane. The below table comparatively shows the retention of stabilizers from the different ASTM tests of Figs. 2A-2D where the tested samples differed by the amounts of graphene (0.5%,

1.5%, 2% and 5%) included in the sample.

[0039]

[0040] It should be appreciated that while the retained stabilizers in these tests fell slowly as graphene content was increased with the ASTM D3895 Oven Aging OIT STD test, and was relatively unaffected by the graphene content in the ASTM D3895 Oven Aging HPOIT test, the retained stabilizers increased significantly with increases in graphene with the ASTM D5885 UV HPOIT test (from 69% with 0.5% graphene to 88.2% with 5.0% graphene).

[0041] As Applicant found and confirmed in this testing, graphene increases the retention of the stabilizers, thereby increasing the interception of polymer oxidation of the membrane polymer (/.e., decreasing the oxidation reaction of the membrane polymer) and increasing the integrity and life of the membrane.

[0042] It should be appreciated that membranes as described herein may be made by the following steps: a. mixing a given amount of a masterbatch composition comprising a resin and additives including stabilizers; and

b. extruding the formulation formed in step a) to form a polymeric membrane layer,

c. wherein graphene particles are added to the membrane layer.

[0043] The graphene particles may be added to a master batch prior to extrusion, or may be sprayed on a layer during or after extrusion of the polymer membrane.

[0044] One or more additional membrane layers may be extruded without graphene, with such additional membrane layer(s) may be joined with the layer(s) having graphene.

[0045] The polymeric membrane 10a may advantageously be formed of a polymeric material selected, without limitation, from polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyethylene of raised temperature (PE-RT) or any other polymeric material that may be used to manufacture a membrane. The PE resin may be selected, without limitation, from the group consisting of Linear Low Density PE (LLDPE), Low Density PE (LDPE), Medium Density PE (MDPE) and High Density PE (HDPE).

[0046] Further, advantageously, the graphene content in the membrane may vary between approximately 1 % and 20 % (by weight).

[0047] Still further, the presence of graphene in the membrane may be used to either improve the characteristics of the membrane or to reduce the material requirements for a given membrane property or characteristic, thus potentially reducing costs associated with the manufacturing and installation of membranes.

[0048] It should be appreciated that suitable stabilized membranes 10 as disclosed herein may be readily formed by incorporating graphene as described into existing membrane formulations, including membranes available from many sources such as Geonets, Geocomposites, Geogrids and Geotextiles. Such membranes are available, for example, from Solmax International (see, e.g., https//www.solmax.com) of Varennes (Quebec), Canada, including, but not limited to, the following polyethylene (PE) geomembranes liners:

[0049] HDPE (High Density Polyethylene) Liner Series,

[0050] LLDPE (linear Low Density Polyethylene) Liner Series,

[0051] Premium HD Liner Series,

[0052] Premium LL Liner Series,

[0053] Sekoia HD Liner Series,

[0054] LiteEarth™ Synthetic T urf Earth Capping System,

[0055] HLR (Hot Liquid Rated) Liner Series,

[0056] BioCoverPro Liner Series,

[0057] EZ-Fix Liner Series,

[0058] F3 Liner Series, or

[0059] R3 Liner Series,

[0060] and including, but not limited to, the following polyvinyl chloride (PVC) geomembrane liners: [0061] PVC Fish Grade Series,

[0062] FGM 115 Series,

[0063] PVC Potable Grade Series, or

[0064] XR5 Liner Series 8130 & 8138,

[0065] the membrane densities of which are typically approximately 1.20 g/cm³, and wherein the membrane thicknesses of which may typically vary between 0.5 mm and 5 mm.

[0066] Graphene enhances the mechanical and chemical properties of a membrane as well as the membrane’s resistance to UV light. Advantageously, the presence of graphene may result in the reduction of the material requirements for specifically-targeted membrane properties. Consequently, the presence of graphene in a membrane composition may significantly reduce costs associated with the manufacturing and installation of membranes. Additionally, the presence of graphene may also render the membrane conductive, thinner, lighter and stronger.

[0067] It should be appreciated that graphene has the ability to render a membrane more efficient by minimizing or reducing the material requirements for a targeted membrane property. For example, a membrane having graphene protecting against the loss of stabilizers may allow for a reduced membrane thickness compared to a membrane without the presence of graphene to achieve similar mechanical strength properties.

[0068] It should also be appreciated that membranes according to the invention detailed herein may be suitable for use in the following applications: mining, petrochemical, coal ash, coal seam gas, shale gas, biogas, aquaculture, agriculture, waste management, water, landscaping, floating cover applications and geomembrane panels. The membranes may also be used as geomembrane liners in applications such as bioreactors landfills, hot liquid storage, coal seam gas brine ponds, geothermal wastewater ponds, and the like.

[0069] While illustrative and presently preferred embodiments of the invention have been described in detail hereinabove, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.

Claims

1. A membrane comprising a polymeric material and one or more additives, wherein at least one additive is graphene.

2. The membrane of claim 1 , wherein the polymeric material is chosen from polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS) and polyethylene of raised temperature (PE-RT).

3. The membrane of claim 2, wherein the graphene is selected from graphene particles, nanoparticles, nanofillers, nanocomposites, nanoplates, graphene nanoplatelets (GNPs), graphene powder, graphene oxide (GO), and reduced graphene oxide (rGO).

4. The membrane of claim 1 , wherein said membrane is a geomembrane for use at a geotechnical site.

5. The membrane of claim 4, wherein the geotechnical site includes mining, petrochemical, coal ash, coal seam gas, shale gas, biogas, aquaculture, agriculture, waste management, water, landscaping, floating cover applications or geomembrane panels.

6. The membrane of claim 1 , wherein the graphene content is between approximately 1 % and 20% (by weight).

7. The membrane of claim 6, wherein said membrane comprises a plurality of membrane layers, at least one of said layers not including graphene, wherein the layers other than said at least one layer include between 1% and 20% graphene by weight.

8. A geomembrane comprising an extruded polymeric layer including graphene and a stabilizer adapted to suppress polymer oxidation.

9. The geomembrane of claim 8, wherein the polymeric material is chosen from polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS) and polyethylene of raised temperature (PE-RT).

10. The geomembrane of claim 9, wherein the graphene is selected from graphene particles, nanoparticles, nanofillers, nanocomposites, nanoplates, graphene nanoplatelets (GNPs), graphene powder, graphene oxide (GO), and reduced graphene oxide (rGO).

11. The geomembrane of claim 8, wherein said membrane is a geomembrane for use at a geotechnical site.

12. The geomembrane of claim 11 , wherein the geotechnical site includes mining, petrochemical, coal ash, coal seam gas, shale gas, biogas, aquaculture, agriculture, waste management, water, landscaping, floating cover applications or geomembrane panels.

13. The geomembrane of claim 8, wherein the graphene content is between approximately 1% and 20% (by weight).

14. The geomembrane of claim 13, wherein said geomembrane comprises a plurality of membrane layers, at least one of said layers not including graphene, wherein the layers other than said at least one layer include between 1 % and 20% graphene by weight.

15. A method of manufacturing a selected area of polymeric geomembrane comprising the steps of:

selecting from a plurality of master batches of polymers and a stabilizer adapted to suppress polymer oxidation;

selecting a graphene content to include in said selected area, wherein at least one of the polymers and stabilizer in the master batches for the selected area decreases as the selected graphene content increases; and extruding the selected master batch to form a geomembrane;

wherein said formed geomembrane includes said selected graphene.

16. The method of claim 15 manufacturing a polymeric membrane comprising one or more layers, wherein graphene is added to at least one layer of the membrane during the manufacturing process.