WO2012140017A1

WO2012140017A1 - Barrier system

Info

Publication number: WO2012140017A1
Application number: PCT/EP2012/056461
Authority: WO
Inventors: Roelof Marissen; Dietrich Wienke
Original assignee: Dsm Ip Assets B.V.
Priority date: 2011-04-12
Filing date: 2012-04-10
Publication date: 2012-10-18
Also published as: CN103476994A; JP2014517164A; EP2697436A1; JP6175705B2; CN103476994B; US20140186118A1

Abstract

The invention relates to a barrier system comprising a barrier wall for stopping a flow of a substance to one side of said wall, wherein said barrier wall comprises a fabric impervious to the flow of said substance and containing high strength polyolefin fibers.

Description

BARRIER SYSTEM

The present invention relates to a barrier system comprising a barrier wall for stopping a flow of substance to one side of said wall, wherein said barrier wall comprises a fabric.

Such barrier systems are known in the art, for example from US 4,033, 137 wherein a barrier for containing oil spills or other debris on the surface of a body of water is disclosed. Said barrier may also comprise a flat rectangular panel which can be made up of an impervious fabric stretched on a rectangular frame.

It was observed however that the known barrier systems such as that presented hereinabove may be improved. Therefore an aim of the present invention may be to provide an improved barrier system and more in particular to provide a barrier system having an optimal strength and/or mechanical stability.

The invention provides a barrier system comprising a barrier wall for stopping a flow of a substance to one side of said wall, wherein said barrier wall comprises a fabric impervious to the flow of said substance and containing high strength polyolefin fibers.

It was observed that the barrier system of the invention may stop the flow of relatively large volumes of substances such as dirt, rocks, water, snow and the like without failure. Moreover, it was observed that the barrier system of the invention may maintain its original shape in spite of variations in temperature, humidity and other environmental factors. In particular, the barrier system of the invention may maintain its original shape even after encountering multiple loadings generated by flows of substances such as the ones mentioned hereinabove.

In one embodiment, the barrier system of the invention is used for stopping flows of rocks or snow as those occurring in e.g. rock or snow avalanches. The fabric utilized to manufacture the barrier wall of the system of this embodiment, needs to stop the flow of rocks and snow although it may be advantageous for reasons of energy dissipation that some of the rocks or some of the snow may go through the barrier wall. This may be achieved for example by using a fabric having openings therein.

In another embodiment, the barrier system of the invention is used for stopping flows of dirt. In yet another embodiment, the barrier system of the invention is a water barrier system, i.e. a system used to stop a flow of water. Preferably, the barrier wall contained by said system comprises a fabric containing high strength polyolefin fibers and also a thermoplastic material laminated on said fabric to form a water- impervious barrier wall.

An advantage of the barrier system according to the present invention may be its strength and/or its tear resistance. It was observed that even when the barrier is perforated locally, e.g. by floating debris, sharp rocks and the like, the damage remains mostly local.

In a preferred embodiment, the barrier system of the invention is a water barrier system comprising:

i. a base structure located on the seabed or on the ground to be protected ii. a float for providing a buoyancy force; wherein preferably said float is

accommodated on or inside of said base structure when said barrier system is not in used;

iii. a barrier wall interposed between and attached to the base structure and the float; the barrier wall comprising a fabric containing high strength polyolefin fibers and preferably a thermoplastic material laminated on said fabric to form a water-impervious barrier wall;

wherein when the float is accommodated on or inside of said base structure, said barrier wall is allowed to rest in a folded manner on or inside of said base structure. A similar barrier system is also known for example from US 5,154,537 included herein in its entirety by reference.

Tiedown means, e.g. ropes, metal or synthetic chains or cables, may be connected to the barrier wall and to a fixed point e.g. on the ground, seabed or base structure, in such a way that the loads exerted by the water on said wall are at least partially transferred to said means.

In another preferred embodiment, the barrier system of the invention is a water barrier system for presenting under flood risk an above-ground-level barrier wall spanning the space between at least two given spaced points to stop the water flow to one side of said barrier wall, said system comprising:

i. a housing structure having a float-receiving chamber and preferably at least one ground liquid inlet passageway having an inlet at the top of said housing and extending between the top of said housing structure to the bottom portion of said chamber so that ground liquid can fill said chamber when permitted to do so;

ii. a float structure for said chamber which is sized to be vertically movable therein from a bottommost position therein when there is no water build up therein to a given level and to an upper position when the water rises; and

iii. a barrier wall interposed between and attached to the float structure and to said chamber, said barrier wall being initially located at or below ground level when said float structure is in said bottommost position and is at least partially, preferably fully, above ground level when said float structure is in its upper position;

wherein said barrier wall comprises a fabric containing high strength polyolefin fibers and a thermoplastic material laminated on said fabric to form a water-impervious barrier wall. A similar barrier system is known from US 5,460,462, which is included herein in its entirety by reference.

It was observed that a water barrier system according to the invention may be accommodated in a relatively small volume cavity due to its flexibility and thinness and may also be folded in a compact way. In case protection is needed, said system may be deployed by unfolding in a relatively short amount of time. The small volume of the cavity containing the barrier allows for storage without significantly disturbing the environment or the surrounding architecture, and alternatively it may be included in shore structures, dikes, etc. It may also be stored under water, e.g. on the seabed at a convenient distance from the shore, without substantially reducing local water depth, thus not impairing ship moving possibilities or coastal leisure activities. Yet in cases of danger, e.g. announced tsunami arrivals, the barrier system of the invention may be deployed and provide adequate protection. It was observed that existing water barrier systems are rigid and bulky and requiring a relatively large storage cavity and thus having the potential of interfering with local architecture and other functionalities. Such disadvantages may however be alleviated by the water barrier system of the invention.

According to the invention, the barrier wall contains high strength polyolefin fibers. By fiber is herein understood an elongated body having a length dimension and transverse dimensions, e.g. a width and a thickness, wherein the length dimension is much greater that the transverse dimensions. The term fiber also includes various embodiments e.g. a filament, a ribbon, a strip, a band, a tape and the like having regular or irregular cross-sections. Preferably, the fiber has a continuous length unlike staple fibers which have discontinuous lengths. A yarn for the purpose of the invention is an elongated body containing a plurality of fibers.

In a preferred embodiment, the polyolefin fibers are polyethylene fibers. Good results may be obtained when the polyethylene fibers are high molecular weight polyethylene (HMWPE) fibers, more preferably ultrahigh molecular weight polyethylene (UHMWPE) fibers. Polyethylene fibers may be manufactured by any technique known in the art, preferably by a melt or a gel spinning process. If a melt spinning process is used, the polyethylene starting material used for manufacturing thereof preferably has a weight-average molecular weight between 20,000 g/mol and 600,000 g/mol, more preferably between 60,000 g/mol and 200,000 g/mol. An example of a melt spinning process is disclosed in EP 1 ,350,868 incorporated herein by reference. Most preferred polymeric fibers are gel spun UHMWPE fibers, e.g. those sold by DSM Dyneema under the name Dyneema®. When the gel spinning process is used to manufacture said fibers, preferably an UHMWPE is used with an intrinsic viscosity (IV) of preferably at least 3 dl/g, more preferably at least 4 dl/g, most preferably at least 5 dl/g. Preferably the IV is at most 40 dl/g, more preferably at most 25 dl/g, more preferably at most 15 dl/g. Preferably, the UHMWPE has less than 1 side chain per 100 C atoms, more preferably less than 1 side chain per 300 C atoms.

Preferably the UHMWPE fibers are manufactured according to a gel spinning process as described in numerous publications, including EP 0205960 A, EP 0213208 A1 , US 44131 10, GB 2042414 A, GB-A-2051667, EP 0200547 B1 , EP 04721 14 B1 , WO 01/73173 A1 , EP 1 ,699,954 and in "Advanced Fibre Spinning Technology", Ed. T.

Nakajima, Woodhead Publ. Ltd (1994), ISBN 185573 182 7.

In a special embodiment, the polyolefin fibers used in accordance to the invention have a tape-like shape, or in other words said polyolefin fibers are polyolefin tapes. Preferably said polyolefin tapes are UHMWPE tapes. A tape (or a flat tape) for the purposes of the present invention is a fiber with a cross sectional aspect ratio, i.e. ratio of width to thickness, of preferably at least 5: 1 , more preferably at least 20:1 , even more preferably at least 100: 1 and yet even more preferably at least 1000: 1. The tape preferably has a width of between 1 mm and 600 mm, more preferable between 1.5 mm and 400 mm, even more preferably between 2 mm and 300 mm, yet even more preferably between 5 mm and 200 mm and most preferably between 10 mm and 180 mm. The tape preferably has a thickness of between 10 μηι and 200 μηι and more preferably between 15 μηι and 100 μηι. By cross sectional aspect ratio is herein understood the ratio of width to thickness.

Preferably, the polyolefin fibers employed by the invention have deniers in the range of from 0.5 to 20, more preferably from 0.7 to 10, most preferably from 1 to 5 dpf. The yarns containing said fibers preferably have deniers in the range of from 100 to 3000, more preferably from 200 to 2500, most preferably from 400 to 1000 dtex.

By high strength polyolefin fibers is understood herein polyolefin fibers that have a high tensile strength of e.g. at least 0.5 GPa. The tensile strength of the polyolefin fibers is preferably at least 1.2 GPa, more preferably at least 2.5 GPa, most preferably at least 3.5 GPa. Preferably, the polyolefin fibers are polyethylene fibers, more preferably UHMWPE fibers having a tensile strength of preferably at least 1.2 GPa, more preferably at least 2.5 GPa, most preferably at least 3.5 GPa. A barrier system containing strong polyethylene fibers has a better mechanical stability, is lighter in weight and stronger than any other systems having a similar construction but which contain fibers manufactured from e.g. polyester, nylon or aramid.

Preferably the polyolefin fibers have a tensile modulus of preferably at least 30 GPa, more preferably of at least 50 GPa, most preferably of at least 60 GPa. Preferably the polyolefin fibers are polyethylene fibers, more preferably UHMWPE fibers, wherein tensile modulus of the polyethylene fibers and in particular of the

UHMWPE fibers is at least 50 GPa, more preferably at least 60 GPa, most preferably at least 80 GPa. It was observed that when such high strength polyethylene and more in particular such high strength UHMWPE fibers are used in accordance with the invention, the barrier system of the invention may have good mechanical stability, good lifetime and may be able to successfully withstand rather large external loads acting thereupon.

In a preferred embodiment of the invention, at least 80 mass%, more preferably at least 90 mass%, most preferably about 100 mass% of the fibers contained by the barrier wall are high strength polyolefin fibers. More preferably, at least 80 mass%, more preferably at least 90 mass%, most preferably 100 mass% of the fibers contained by the barrier wall are polyethylene fibers and more preferably UHMWPE fibers. The remaining mass% of fibers may consist of other polymeric fibers. It was observed that by using barrier walls containing an increased mass% of polyethylene fibers and in particular barrier walls wherein all polymeric fibers are polyethylene fibers, the barrier system of the invention may show a good resistance to sun light and UV degradation, high tear strength and low weight.

The high strength polyolefin fibers contained by the barrier wall used in accordance to the invention are forming a fabric. Said fabric may be of any construction known in the art, e.g. woven, knitted, plaited, braided or non-woven or a combination thereof. Knitted fabrics may be weft knitted, e.g. single- or double-jersey fabric or warp knitted. An example of a non-woven fabric is a felt fabric or a fabric wherein the fibers run substantially along a common direction in a substantially parallel fashion. Further examples of woven, knitted or non-woven fabrics as well as the manufacturing methods thereof are described in "Handbook of Technical Textiles", ISBN 978-1-59124-651-0 at chapters 4, 5 and 6, the disclosure thereof being

incorporated herein as reference. A description and examples of braided fabrics are described in the same Handbook at Chapter 11 , more in particular in paragraph 1 1.4.1 , the disclosure thereof being incorporated herein by reference.

Preferably the fabric used in accordance to the invention is a woven fabric. Preferably said woven fabric is constructed with a small weight per unit length and overall cross-sectional diameter. Preferred embodiments of woven fabrics include plain (tabby) weaves, rib weaves, matt weaves, twill weaves, basket weaves, crow feet weaves and satin weaves although more elaborate weaves such as triaxial weaves may also be used. More preferably the woven fabric is a plain weave, most preferably, the woven fabric is a basket weave. Preferably, the fibers used to manufacture the woven fabric are tapes, more preferably they are fibers having a rounded cross-section, said cross section having preferably an aspect ratio of at most 4: 1 , more preferably at most 2: 1.

According to some embodiments of the invention, the barrier wall may also contain a thermoplastic material, in particular when the barrier system of the invention is used as a water barrier system. It is preferred however that for all embodiments of the invention the barrier wall contains the thermoplastic material. Non- limiting examples of suitable thermoplastic material include polyolefins such as low density polyethylene and high density polyethylene, ethyl vinylacetate, polyurethanes, polyvinyls, polyacrylics, polybutyleneterephthalate (PBT), polyamides, polycarbonates or thermoplastic elastomeric block copolymers such as polyisopropene-polyethylene- butylene-polystyrene or polystyrene-polyisoprene-polystyrene block copolymers. Other suitable thermoplastic materials are enumerated in, for example, WO 91/12136 A1 (pages 15-21) included herein by reference. The thermoplastic material is laminated onto the fabric contained by the barrier wall to make said wall impervious to a flow of a substance such as water, snow, dirt, rocks and the like. Preferably the thermoplastic material is a plastomer, said plastomer preferably being a semi-crystalline copolymer of ethylene or propylene and one or more C2 to C12 a-olefin co-monomers and wherein said plastomer has a density as measured according to IS01 183 of between 860 and 930 kg/m³.

Preferably, the barrier wall contains a fabric, wherein a plastomer is preferably impregnated throughout said fabric. The impregnation may be carried out in various forms and ways, for example by lamination or by forcing the plastomer through the yarns and/or the fibers of the fabric in e.g. a heated press. Examples of processes for the manufacturing of impregnated fabrics are disclosed for instance in US

5,773,373; US 6,864, 195 and US 6,054, 178 included herein by reference. These processes can be routinely adapted for the materials, e.g. fibers, plastomer, utilized by the present invention.

Good results may be obtained when the plastomer has a tensile modulus of at most 0.6 GPa, more preferably of at most 0.4 GPa, most preferably of at most 0.2 GPa. Preferably, said plastomer has a tensile modulus of at least 0.01 GPa, more preferably of at least 0.05 GPa, most preferably of at least 0.1 GPa.

It was observed that when using such impregnated fabrics as the barrier wall of the barrier system of the invention, the mechanical stability of said system was improved. In particular the elongation of the system under external loads and/or its shrinkage in time were minimized.

A preferred example of a barrier wall suitable for the invention is a barrier wall comprising a woven fabric containing high strength polyethylene fibers, more preferably high strength UHMWPE fibers and which is impregnated with a plastomer which is a semi-crystalline copolymer of ethylene or propylene and one or more C2 to C12 a-olefin co-monomers and wherein said plastomer has a density as measured according to IS01 183 of between 860 and 930 kg/m³. When the barrier system of the invention comprises such a barrier wall, said system may show enhanced tear resistance; good handling; and excellent chemical and fire resistance. In particular impregnated woven fabrics containing polyethylene fibers and/or yarns show an excellent weight to strength ratio, they are lightweight and stronger than any impregnated fabric containing e.g. polyester, nylon, or aramid fibers. In a preferred embodiment of the invention, the barrier wall comprises:

(i) a fabric, preferably a woven fabric, comprising yarns containing

polyethylene fibers, preferably UHMWPE fibers;

(ii) a plastomer layer adhered to at least one surface of said woven fabric

wherein said plastomer is a semi-crystalline copolymer of ethylene or propylene and one or more C2 to C12 a-olefin co-monomers and wherein said plastomer has a density as measured according to IS01 183 of between 860 and 930 kg/m³.

It was noticed by the present inventors that when the barrier system of the invention comprises such a barrier wall, said system may show in addition to the above mentioned advantages, a proper resistance to shrinkage especially during long term use. It was also observed the said system is lightweight, has a good tear resistance and a high strength to break. It was furthermore observed that during its utilization in cold environments, said system is less affected by low temperature induced damages, e.g. cracks and the like.

Preferably, the barrier wall comprises:

(i) a woven fabric comprising yarns containing polyethylene fibers, preferably UHMWPE fibers;

(ii) a plastomer layer having a first part adhered to one surface of said woven fabric and a second part impregnated between the yarns and/or the fibers of said fabric, the second part extending throughout said fabric and being cohesively connected to said first part; and wherein said plastomer is a semi-crystalline copolymer of ethylene or propylene and one or more C2 to C12 a-olefin co-monomers and wherein said plastomer has a density as measured according to IS01 183 of between 860 and 930 kg/m³..

It was further noticed that yet a better shrinkage resistance for the barrier system of the invention may be obtained when the plastomer layer adheres to both surfaces of the woven fabric, therefore encapsulating said fabric. Therefore, in a preferred embodiment, the barrier wall comprises:

(i) a woven fabric having an upper surface and a lower surface and comprising yarns containing polyethylene fibers, preferably UHMWPE fibers; (ii) a plastomer layer encapsulating said fabric, said plastomer layer having a first part adhered to said upper surface; a third part adhered to said lower surface; and a second part which is impregnated between the yarns and/or the fibers of said fabric and extends throughout said fabric, said second part being cohesively connected to said first and third part of said plastomer layer; wherein said plastomer is a semi-crystalline copolymer of ethylene or propylene and one or more C2 to C12 a-olefin co-monomers and wherein said plastomer has a density as measured according to IS01 183 of between 860 and 930 kg/m³.

Preferably said second part is impregnated between both the yarns and the fibers. The second part of the plastomer layer also extends throughout said fabric meaning that the plastomer is distributed along the lateral dimensions of the fabric as well as along the vertical dimension of the fabric between the surfaces thereof. Preferably, the impregnation is carried out such that said second part of the plastomer layer extends along the vertical dimension from one surface of the fabric all the way to the opposite surface thereof.

By a plastomer layer adhered to a surface of a fabric is herein understood that the plastomer grips by physical forces to the fibers of the fabric with which it comes into contact. It is however not essential for the invention that the plastomer actually chemically bonds to the surface of the fibers. It was observed that the plastomer used according to the invention has an increased grip on e.g. the polyethylene fibers as compared with other types of thermoplastic materials. In a preferred embodiment the surface of the polyethylene fibers is corrugated, have protrusions or hollows or other irregular surface configurations in order to improve the grip between the plastomer and the fiber.

By two cohesively connected parts of the plastomer layer is herein understood that said parts are fused together into a single body such that preferably no line of demarcation is formed therein between and preferably no substantial variations of mechanical or other physical properties occur throughout the plastomer layer.

It also goes without saying that the terms "upper surface" and "lower surface" are merely used to identify the two surfaces which are characteristic to a woven fabric and should not be interpreted as actually limiting the woven fabric to facing a certain up or down positioning. Preferred woven fabrics for use according to the invention are fabrics having a cover factor of at least 1.5, more preferably at least 2, most preferably at least 3. Preferably, said cover factor is at most 30, more preferably at most 20, most preferably at most 10. It was observed that the use of such fabrics lead to an optimum impregnation of the woven fabric minimizing the amount of voids or air pockets contained by e.g. the barrier wall. It was furthermore observed that a more

homogeneous barrier wall is obtained which in turn imparted the barrier system of the invention with less local variations of its mechanical properties and better shape stability. The impregnation with a plastomer can be carried out for example by forcing under pressure the molten plastomer through said fiber and/or yarns.

The plastomer used in accordance with the invention is a plastic material that belongs to the class of thermoplastic materials. According to the invention, said plastomer is preferably a semi-crystalline copolymer of ethylene or propylene and one or more C2 to C12 a-olefin co-monomers, said plastomer having a density of between 860 and 930 kg/m³. It was observed that a barrier wall containing such plastomer showed a good shrinkage resistance when the plastomer was manufactured by a single site catalyst polymerization process, preferably said plastomer being a metallocene plastomer, i.e. a plastomer manufactured by a metallocene single site catalyst. Ethylene is in particular the preferred co-monomer in copolymers of propylene while butene, hexene and octene are being among the preferred α-olefin co-monomers for both ethylene and propylene copolymers.

In a preferred embodiment, said plastomer is a thermoplastic copolymer of ethylene or propylene and containing as co-monomers one or more a- olefins having 2-12 C-atoms, in particular ethylene, isobutene, 1-butene, 1-hexene, 4- methyl-1-pentene and 1-octene. When ethylene with one or more C3 - C12 a -olefin monomers as co-monomers is applied, the amount of co-monomer in the copolymer usually is lying between 1 en 50 wt.%, and preferably between 5 and 35 wt. %. In case of ethylene copolymers, the preferred co-monomer is 1-octene, said co-monomer being in an amount of between 5 wt% and 25 wt%, more preferably between 15 wt% and 20 wt%. In case of propylene copolymers, the amount of co-monomers and in particular of ethylene co-monomers, usually is lying between 1 en 50 wt.%, and preferably between 2 and 35 wt%, more preferably between 5 and 20 wt.%. Good results in terms of shrinkage may be obtained when the density of the plastomer is between 880 and 920 kg/m³, more preferably between 880 and 910 kg/m³. Better resistance to shrinkage may be obtained when the plastomer used according to the invention has a DSC peak melting point as measured according to ASTM D3418 of between 70°C and 120°C, preferably between 70°C and 100°C, more preferably between 70°C and 95°C.

A plastomer manufactured by a single site catalyst polymerization process and in particular a metallocene plastomer is distinguished from ethylene and propylene copolymers that have been manufactured with other polymerization techniques, e.g. Ziegler-Natta catalysation, by its specific density. Said plastomer also differentiates itself by a narrow molecular weight distribution, Mw/Mn, the values thereof preferably being between 1.5 en 3.0 and by a limited amount of long chain branching. The number of long chain branches preferably amounts at most 3 per 1000 C-atoms. Suitable plastomers that may be used in the barrier wall utilized in

accordance with the invention and obtained with the metallocene catalyst type are manufactured on a commercial scale, e.g by DEXPIastomers, ExxonMobil, Mitsui and DOW under brand names as Exact, Exceed, Vistamaxx, Tafmer, Engage, Affinity and Versify, respectively. A description of plastomers and in particular of metallocene plastomers as well as an overview of their mechanical and physical properties can be found for instance in Chapter 7.2 of "Handbook of polypropylene and polypropylene composites" edited by Harutun G. Karian (ISBN 0-8247-4064-5) and more in particular in subchapters 7.2.1 ; 7.2.2; and 7.2.5 to 7.2.7 thereof, which are included herein by reference.

It is also possible to use compositions comprising the plastomer used in accordance with the invention and other thermoplastic materials and/or even other plastomer grades. In a preferred embodiment, a blend containing the plastomer and a functionalized polyolefin are used in accordance with the invention. Preferably the functionalized polyolefin is in an amount of between 1 wt% and 99 wt% of the blend weight, more preferably between 2.5 wt % and 50 wt%, more preferably between 5 wt% and 25 wt%. The functionalized polyolefin is preferably functionalized with a bifunctional monomer, the amount of the bifunctional monomer being between 0.1 wt% and 10 wt%, more preferably between 0.35 wt% and 5 wt%, most preferably between 0.7 wt% and 1.5 wt% of the weight of the polyolefin. Preferably the polyolefin used for functionalisations is also a plastomer, more preferably said polyolefin is the plastomer used in accordance with the invention. Preferably the polyolefin is functionalized with a bifunctional monomer such as maleicanhydride (MA) or vinyltrimethoxysilane (VTMOS). MA and VTMOS functionalized polyolefin's are commercially available products and the functionalization of the polyolefin may be carried out in accordance with known methods in the art, e.g. in an extrusion process, using peroxide as initiator. The advantage of using a functionalized polyolefin, preferably a functionalized plastomer is that the mechanical stability of the barrier wall used in accordance with the invention may be improved.

Good shrinkage resistance may be obtained when the barrier wall used in accordance with the invention contains a fabric, preferably a woven fabric, and wherein the amount of plastomer was chosen to yield a barrier wall having an areal density (AD) that is with at least 20%, more preferably at least 50% higher than the AD of the fabric utilized therein. Preferably the barrier wall has an areal density (AD) that is with at most 500%, more preferably at most 400%, most preferably at most 300% higher than the AD of the fabric, preferably of the woven fabric, utilized therein. Good results may be obtained when the plastomer encapsulates the fabric which is preferably a woven fabric and the amount of plastomer was chosen as indicated hereinabove. AD is expressed in kg/m² and is obtained by weighing a certain area, e.g. 0.01 m² and dividing the obtained mass by the area of the sample.

The plastomer used in accordance with the invention may also contain various fillers and/or additives as defined hereinafter. In a preferred

embodiment, the barrier wall comprises a woven fabric, a plastomer layer as defined hereinabove and optionally various fillers and/or additives as defined hereinafter added to the plastomer. Preferably, however, the plastomer is free of any filler and/or additive. It was observed that when the barrier system of the invention comprises a barrier wall in accordance with this embodiment, said system may show a reduced shrinkage while being strong and lightweight. Moreover, said system wall may easily be sealed along a seam by heat welding, which provides a strong seal and results in overall time and cost savings.

Examples of fillers include reinforcing and non-reinforcing materials, e.g. carbon black, calcium carbonate, clay, silica, mica, talcum, and glass. Examples of additives include stabilizers, e.g. UV stabilizers, pigments, antioxidants, flame retardants and the like. Preferred flame retardants include aluminum tryhidrate, magnesium dehydrate, ammonium polyphosphate and others. The amount of flame retardants is preferably from 1 to 60, more preferably from 5 to 30 by weight percent of the amount of thermoplastic material contained by the barrier wall. Most preferred flame retardant is ammonium phosphate, e.g. supplied by Budenheim (Budit) and Clariant (Exolit)

A laminated fabric can be manufactured according to known methods in the art. Examples of such methods are disclosed in US 5,773,373 and US 6,054,178 included herein by reference. Preferably, the laminated fabric is manufactured by a lamination method as for example the one disclosed in US 4,679,519 included herein by reference, said method being routinely adapted to the materials used in the present invention.

Preferably, the thickness of the barrier wall is between 0.2 mm and 10 mm, more preferably between 0.3 mm and 5 mm. The AD of said barrier wall is preferably between 0.2 kg/m² and 3 kg/m², more preferably between 0.2 kg/m² and 2 kg/m².

When the barrier wall comprises a woven fabric encapsulated by the plastomer, said fabric can be positioned in the center of said barrier wall or off center. Good results in terms of shrinkage may be obtained when the fabric was positioned as close as possible to the center of the barrier wall.

Preferably, the barrier wall has a total shrinkage, i.e. the average shrinkage in the warp and the weft directions of the woven fabric, of less than 1.5%, more preferably of less than 1.2%, even more preferably of less than 1.0%, yet even more preferably of less than 0.8%, yet even more preferably of less than 0.6%, most preferably of less than 0.45% when measured according to the methodology disclosed hereinafter in the "METHODS OF MEASUREMENT" section of the present document. Preferably, the barrier wall has a shrinkage in the warp direction of less than 1 %, more preferably less than 0.6%. Preferably, the barrier wall has a shrinkage in the weft direction of less than 1 %, more preferably less than 0.5%.

The invention will be further explained with the help of the following examples without being however limited thereto.

METHODS OF MEASUREMENT IV: the Intrinsic Viscosity of UHMWPE is determined according to method PTC-179 (Hercules Inc. Rev. Apr. 29, 1982) at 135°C in decalin, the dissolution time being 16 hours, with DBPC as anti-oxidant in an amount of 2 g/l solution, by extrapolating the viscosity as measured at different concentrations to zero concentration. Cover factor: of a woven fabric is calculated by multiplying the average number of individual weaving yarns per centimeter in the warp and the weft direction with the square root of the linear density of the individual weaving yarns (in tex) and dividing by 10.

An individual weaving yarn may contain a single yarn as produced, or it may contain a plurality of yarns as produced said yarns being assembled into the individual weaving yarn prior to the weaving process. In the latter case, the linear density of the individual weaving yarn is the sum of the linear densities of the as produced yarns.

The cover factor (CF) can be thus computed according to formula:

wherein m is the average number of individual weaving yarns per centimeter, p is the number of as produced yarns assembled into a weaving yarn, t is the linear density of the yarn as produced (in tex) and T is the linear density of the individual weaving yarn (in tex).

Dtex: of a fiber was measured by weighing 100 meters of fiber. The dtex of the fiber was calculated by dividing the weight in milligrams by 10.

Shrinkage: a square sample of 0.4 m length and 0.4 m width, was placed in the drum of a laundry machine and rotated in the absence of water at a rotating speed of 60 rot/min for 72 hours at a temperature of about 23°C and humidity of about 65% together with a number of 5 clay balls. Each clay ball had a mass of 0.22 Kg and a diameter of about 50 mm, the surface of each ball being covered with a cotton fabric by placing the ball in a cotton bag which tightly accommodates the ball. The dimensions of the sample were measured before and after the treatment and the difference thereof (expressed in %) was considered representative for the shrinkage of the sample.

Tensile properties, i.e. strength and modulus, of polymeric fibers were determined on multifilament yarns as specified in ASTM D885M, using a nominal gauge length of the fibre of 500 mm, a crosshead speed of 50%/min and Instron 2714 clamps, of type Fibre Grip D5618C. For calculation of the strength, the tensile forces measured are divided by the titre, as determined by weighing 10 metres of fibre; values in GPa for are calculated assuming the natural density of the polymer, e.g. for

UHMWPE is 0.97 g/cm³.

The tensile properties of polymeric tapes: tensile strength and tensile modulus are defined and determined at 25 °C on tapes of a width of 2 mm as specified in ASTM D882, using a nominal gauge length of the tape of 440 mm, a crosshead speed of 50 mm/min.

The tensile strength and modulus of inorganic fibers and in particular of glass fibers was measured according to ASTM D4018-81 at 22°C.

Tensile modulus of thermoplastic materials was measured according to ASTM D-638(84) at 25°C.

EXAMPLE AND COMPARATIVE EXPERIMENT EXAMPLE

A barrier wall was manufactured from a basket woven fabric having an AD of 0.193 kg/m², a thickness of about 0.6 mm and a width of about 1.72 m, and containing 880 dtex polyethylene yarns known as Dyneema® SK 65 which was impregnated with Exact® 0203. Exact® 0203 is plastomer from DEXPIastomers and is an ethylene based octane plastomer with about 18% octane, a density of 902 kg/m³ and a DSC peak melting point of 95°C.

The plastomer was molten at a temperature of about 145°C and discharged on a surface of the fabric.

A pressure of about 45 bars was applied to impregnate the plastomer into the fabric at a temperature of about 120°C.

The above process was repeated in order to coat both surfaces of the woven fabric. The obtained barrier wall had a thickness of about 0.8 mm, an AD of 0.550 kg/m² and less than 40% voids. The AD of the wall was 280% larger than the AD of the woven fabric. The plastomer layer was devised into:

· a first part of AD of about 0.175 kg/m² covering one surface;

• a second part impregnated through the fabric between the yarns and fibers thereof; and

• a third part having an AD of about 0.175 kg/m² covering the other surface. The results are presented in Table 1.

Shrinkage in warp Shrinkage in weft Total shrinkage

Sample

direction (%) direction (%) (%)

Example 0.96 0.42 0.69

Claims

A barrier system comprising a barrier wall for stopping a flow of a substance to one side of said wall, wherein said barrier wall comprises a fabric impervious to the flow of said substance and containing high strength polyolefin fibers The barrier system of claim 1 wherein said system is a water barrier system comprising:

i. a base structure located on the seabed or on the ground to be

protected;

ii. a float for providing a buoyancy force; wherein preferably said float is accommodated on or inside of said base structure when said barrier system is not in used;

wherein when the float is accommodated on or inside of said base structure, said barrier wall is allowed to rest in a folded manner on or inside of said base structure.

The barrier system of claim 1 wherein said system is a water barrier system for presenting under flood risk an above-ground-level barrier wall spanning the space between at least two given spaced points to stop the water flow to one side of said barrier wall, said system comprising:

III. a barrier wall interposed between and attached to the float structure and to said chamber, said barrier wall being initially located at or below ground level when said float structure is in said bottommost position and is at least partially, preferably fully, above ground level when said float structure is in its upper position; ...

wherein said barrier wall comprises a fabric containing high strength polyolefin fibers and a thermoplastic material laminated on said fabric to form a water- impervious barrier wall

The barrier system of any one of the preceding claims wherein the polyolefin fibers are polyethylene fibers, in particular high molecular weight polyethylene (HMWPE) fibers or ultrahigh molecular weight polyethylene (UHMWPE) fibers. The barrier system of any one of the preceding claims wherein the polyolefin fibers have a tape-like shape.

The barrier system of any one of the preceding claims wherein the polyolefin fibers have a tensile strength of at least 0.5 GPa.

The barrier system of any one of the preceding claims wherein the polyolefin fibers have a tensile modulus of at least 30 GPa.

The barrier system of any one of the preceding claims wherein the fabric is chosen from the group consisting of woven, knitted, plaited, braided and non- woven fabrics and a combination thereof.

The barrier system of any one of the preceding claims wherein the fabric is a woven fabric chosen from the group consisting of a plain weave and a basket weave fabric.

The barrier system of any one of the preceding claims wherein the fabric is laminated with a thermoplastic material, preferably a plastomer.

The barrier system of any one of the preceding claims wherein the fabric is laminated with a plastomer having a tensile modulus of at most 0.6 GPa.

The barrier system of any one of the preceding claims wherein the fabric is a woven fabric having a cover factor of at least 1.5.

The barrier system of any one of the preceding claims wherein the fabric is laminated with a plastomer, the plastomer being a thermoplastic copolymer of ethylene or propylene and containing as co-monomers one or more a-olefins having 2-12 C-atoms, in particular ethylene, isobutene, 1-butene, 1-hexene, 4- methyl-1-pentene and 1-octene.

14. The barrier system of any one of the preceding claims wherein the fabric is preferably a woven fabric, said fabric being laminated with a plastomer and wherein the amount of plastomer is chosen to yield a barrier wall having an areal density (AD) that is with at least 20%, more preferably at least 50% higher than the AD of said fabric, preferably of said woven fabric.

15. The barrier system of any one of the preceding claims wherein the thickness of the barrier wall is between 0.2 mm and 10 mm.