WO2006079340A1

WO2006079340A1 - A composite material

Info

Publication number: WO2006079340A1
Application number: PCT/DK2006/000037
Authority: WO
Inventors: Mia Katharina Andersen Podlech; Birgit Kjærside STORM; Solvej Jensen
Original assignee: Viking Life-Saving Equipment A/S; Aalborg Universitet Esberg
Priority date: 2005-01-26
Filing date: 2006-01-23
Publication date: 2006-08-03
Also published as: DK200500128A

Abstract

The present invention relates to a composite material comprising at least a first layer substantially made of polyethylene (PE) , and a second layer consisting of a textile made of fibres. A coupling component containing functional groups are applied as an intermediate layer arranged between the first layer and the second layer, hereby enabling a chemical and/or physical bonding be tween the first layer and the second layer.

Description

A COMPOSITE MATERIAL

Field of the Invention

The present invention relates to a composite material comprising at least a first layer substantially made of polyethylene ( PE ) and a second layer consisting of a textile made of fibres .

Background Art

Many products are exposed to multivarious influences or actions which may have severe consequences related to the material said products being made of . Said influences or actions being for instance of environmental character or actions which are being exerted on the product during use or handling .

When the products are being used in an outdoor envi- ronment it may be exposed to both high and/or low temperatures , high and/or low humidity, UV-light , ozone , water, salt , etc . All these environmental characters may over time influence the properties of the material of the products and may as well influence the properties of the material during a short period of time . The latter may be the case if the product for instance is being exposed to UV-light and/or ozone or temperatures below -40°C . UV- light and/or ozone will cause a deterioration in the material and thereby decreasing the mechanical properties of the product . If the material is not inherently flexible at temperatures below -1O⁰C the material and thereby the product will become brittle at these low temperatures . This can likewise cause failure in form of cracking . This may cause failure in the intended use or appli- cation .

The products may also be exposed for physical actions either during use or handling . These actions may for instance be a high load or pressure on a local area of the product, a high tear or tensile force also being exerted on a local area of the product as well as if the product is being bent or folded . These actions may also influence the properties of the material of the product and in some cases the actions may be so large that when they are exerted on the product, the product may be damaged .

Furthermore, the combination of the above mentioned influences or actions may further limit the usability of the product . In addition, today it is important that the material used to different products are environmentally friendly with respect to disposal . Which often is not compatible with the required built-in properties of the products .

If the products are inflatable it is furthermore of importance that the material is in some degree impermeable to gasses and/or liquids .

Products which are exposed for the above mentioned influences and actions are inflatable life-saving equipment, such as floatable units like inflatable platforms , liferafts or evacuation slides . Especially in this case the properties of the material used in manufacturing of the equipment are exposed to extreme conditions , which partly is due to the marine environment and partly to the life-saving situations , wherein the equipment is exposed to high isolated loads and actions .

There are furthermore high statutory requirements for products being used as life-saving equipment .

In the prior art natural rubber is often used as a material for inflatable life-saving equipment . This is due to the fact that natural rubber posses the properties that satisfies the safety requirements for life rafts . These are such as low permeability to gas , a certain puncture resistance, high tensile strength, tear strength, adequate ozone resistance, adequate UV resis- tance and flexibility in a temperature range from -30 to 65⁰C . Another choice is known to be polyurethane , however, polyurethane is known to be less flexible at lower temperatures . However, both natural rubber and polyurethane are expensive materials compared to other polymer materi- als , such as for instance polyethylene . Furthermore, natural rubber is non-weldable and both polyurethane and natural rubber have a high density, which result in a high weight of the end-product .

Summary of the Invention

An obj ect of the present invention is to overcome wholly or partly the above disadvantages and drawbacks of the prior art . More specifically, it is an obj ect to provide a composite material wherein one or more of the fol- lowing properties are inherent : flexible in a temperature range from -6O⁰C to 8 O⁰C, impermeable to gas , UV/ozone resistant, good strength, puncture and abrasion resistance, blocking resistant, low density or environmentally compatible . A further obj ect is to provide a composite material , which has a tensile strength of at least 2200 N/50mm.

A further obj ect is to provide a composite material , where the layers are substantially inseparable .

It is also an obj ect of the present invention to provide a composite material , wherein a high coating adhesion between the layers is obtained .

Another obj ect of the present invention is to provide a composite material , which has a low density, inexpensive raw material and which is inexpensive to manufac- ture .

The above obj ects , together with numerous other obj ects , advantages and features , which will become evident from the below description, are accomplished by a solution in accordance with the present invention where a coupling component containing functional groups are applied as an intermediate layer arranged between the first layer and the second layer, hereby enabling a chemical and/or physical bonding between the first layer and the second layer .

According to the invention the coupling component may comprise a material , which in part is polar and in part is non-polar . Hereby it is possible for the coupling component to provide chemical and/or physical bonds to the layers between which it is arranged under the circumstance that one of said layers are polar and the other is non-polar . Advantageously, according to the invention the coupling component may comprise at least a PE copolymerised with one or more polar functional groups . The polar functional groups are advantageously, according to the invention, selected from the groups of : acid, epoxy, ester, anhydride, hydroxyl , ionomers , acrylate . By applying a coupling component containing polar functional groups , these groups are able to provide a strong adhesion to the polar layer, i . e . the second layer, and the non-polar part adheres to the non-polar layer, i . e . the first layer .

Furthermore, according to the invention one or more functional groups may be acrylic acid and/or maleic anhydride and/or glycidyl m-acrylate and/or butyl acrylate . In an expedient embodiment according to the inven- tion the first layer may comprise one or more grades of metallocene catalysed PE derivative ( s ) . In addition to the properties previously described which PE inherently possesses , metallocene catalysed PE-derivatives exhibits special properties . This is caused by the fact that met- allocenes among all polymerisation catalysts are the only catalysts , which enable control over the molecular weight, tacticity, regioregularity and comonomer distribution of polyethylene over a very wide range, cf . Sinn, H; Kaminsky, W . ; Advances in organometallic chemistry, vol .18 , 1980 Academic press , Inc . In addition, an important feature of metallocene catalysed PE-derivatives is their high compositional uniformity . Consequently, these types of PE thus produced, provide a set of unique properties that differentiate them from all other PE .

The term metallocene has since the discovery of the ferrocene, evolved and a large number of metallocenes have been prepared . At present the term includes "a wide variety of organometallic structures including those with substituted cyclopentadienyl ligands (Cp) rings , those with bent sandwich structures , and even the half sandwich or mono-Cp complexes" , cf . www . chem. ucalgary . ca 120904. Metallocene based polyethylenes range from crystalline to elastomeric materials and they have been commercially available since 1991. They possess properties such as increased impact strength and toughness . Due to the fact that the molecular structure is controlled, these polymers also have better melting characteristics . Within the group of metallocene catalysed PE-derivatives are metalocene catalysed linear low density PE (mLLDPE) , metallocene catalysed medium density PE (mMDPE) and polyethylenes copolymerised with alkenes ( PE-co-alkenes ) . mMDPE, mLLDPE and PE-co-alkenes are more branched than high density PE (HDPE) . This would generally lower the degree of crystallinity and thereby amongst other properties the tensile strength of the material . However, due to afore mentioned uniformity of the branches it is possible to produce mMDPE, mLLDPE and PE-co-alkenes with strengths comparable to that of HDPE .

PE-co-alkenes are likewise produced with metallocene polymerisation . In this last mentioned group it is possible to obtain a very broad range of mechanical character- istics by merely varying the comonomer content, as is the case of ethylene-1-octene copolymers in which a classical thermoplastic behaviour is observed for low comonomer content to an elastomeric behaviour if the comonomer is especially high, cf . Bensason, S ; Stepanov, E .V. ; Chum, S . ; Hiltner, A. ; Baer, E . ; Macromolecules, 1997 , vol .30 ( 8 ) , pp . 2436-2444. When copolymer content is up to 20% octene the resulting polymer is termed a "plastomer" . When the copolymer content is above 20% the copolymer falls into the range of elastomers , cf . Thayer, A. M . ; Chemical & Engineering News, 1995 , American Chemical Society. This elastomeric behaviour is especially important as it amongst other properties provides improved puncture resistance and dart drop impact strength . "An average dart impact strength of 37μm film made from ethylene-1- butene copolymer is about 100-15Og, whereas the same pa- rameter for ethylene-1-hexene and ethylene-1-octene copolymers of the same density is about 300-35Og", cf . Kissing; Kirk-Othmer Encyclopedia of Chemical Technlogy 4^th ed. ; Ex . ed . Kroschwitz , J . I . ; ed . Howe-Grant, M . ; vol . 17 , pp 702-784 ; John Wiely and Sons 1996, NY . Thus , the first layer may comprise one or more grades of a metallocene catalysed PE-derivative .

Furthermore, according to the invention the metallocene catalysed PE derivative may be selected from the following groups MDPE, LLDPE and PE-co-alkenes . In addition to the inherent PE properties and the outstanding properties of metallocene based PE, MDPE possesses good blocking resistance properties . This property is especially important to inflatable products . MDPE further possesses good strength and stiffness . LLDPE pos- sesses good strength properties . PE-co-alkenes possesses good puncture resistance, strength and toughness . It is hereby made clear that the first layer when comprised of metallocene catalysed PE benefit from this elastomeric ' behaviour thereby obtain properties e . g . Puncture resis- tance and toughness , which a layer of non-metallocene catalysed PE would not posses . In a preferred embodiment according to the invention the preferred PE-co-alkenes are polyethylene copolymerisered with the alkenes from butene to octadecene (C₄-Ci₈) • In another preferred embodiment the alkenes may be selected from butene, hexene, octene, nonene, decene , preferably octene or hexene . In a further preferred embodiment the alkenes may be an octene .

In another preferred embodiment the first layer may comprise 0-20% MDPE, 0-80% LLDPE and 20-100% PE-co- alkenes , preferably the PE-co-alkene is a PE-co-octene. Advantageously, according to the invention the fibres of the textile, of the second layer, may be made of polyamide ( PA) , polyaramide ( PAA) , polyester ( PET) , ultra high molecular weight polyethylene (UHMWPE) , or a combi- nation thereof . The textiles made of such materials provide the composite with a very good tensile strength and tear resistance property . In a preferred embodiment according to the invention the textiles may be polyester or polyamide . In a further preferred embodiment according to the invention the textile is a polyester textile .

Furthermore, in an additional preferred embodiment according to the invention the textiles , the second layer, may be manufactured by knitting or weaving . Both knitting and weaving provides a high tensile strength and tear strength to the second layer . Advantageously, the textiles may be warp or weft knitted .

Additionally, a third layer, substantially made of PE, may be provided on the opposite side of the second layer in relation to the first layer and a coupling com- ponent containing functional groups are applied as an intermediate layer arranged between the second layer and the third layer, hereby enabling a chemical and/or physical bonding between the second layer and the third layer . By applying a further layer to the composite material the properties arising from PE e . g . flexibility, impermeability to gas and puncture resistance will be increased, ensuring these properties are sufficient to meet the demands of the severe conditions in which the product must perform. According to the invention the first layer and the third layer may substantially be made of the same material . Furthermore, according to the invention the intermediate layers may be arranged between the first and second layer and the second and third layer substantially are made of the same material . In another preferred embodiment according to the invention the composite material is made by extrusion . Extrusion is an expedient way of processing polymer materials in the exact thickness of each layer and a chemical and/or physical bonding will take place at the processing of the material . In a further preferred embodiment the composite material is made by coextrusion .

In an advantageous embodiment according to the invention the composite material may posses puncture resistance above 360 N (according to FED-STD-191A, method 5120 ) .

Furthermore, the thickness of the composite material according to the invention may be between 300μm and lOOOμm, preferably between 400 and 700 μm.

In an expedient embodiment according to the inven- tion the composite material posses coating adhesion between the first and second layer above 75N/50 mm according to ISO 2411.

The invention also relates to an use of the composite material mentioned above for products having inflat- able compartments , such as life-saving equipment , such as floatable units like inflatable platforms, liferafts or inflatable evacuation slides . Especially in these cases the invention is advantageous as the material possesses the properties flexible in a temperature range from -60°C to 8O⁰C, impermeable to gas or liquid, UV/ozone resistant , good strength, puncture and abrasion resistance, blocking resistant , low density and even being environmentally compatible .

However, the material according to the invention may as well be used for protection against for instance liquids , coast securing, tarpaulins , geo textiles , under cover for roofs or waterproof clothes . Additionally, the material according to the invention may expediently also be used for playground products such as trampolines , inflatable j umping castles and the like . Another use of the composite material according to the invention may be for a sailcloth .

Brief description of the drawings

The invention and its many advantages will be de- scribed in more detail below with reference to the accompanying schematic drawings , which for the purpose of illustration show some non-limiting embodiments and in which

Fig . 1 shows a cross-section of a preferred embodi- ment of the composite material according to the invention,

Fig . 2 shows a cross-section of an alternative embodiment of composite material of the invention, and

Fig . 3 shows a diagram, wherein the effect of vari- ous intermediate layers on Maximum Load for different composite materials are shown .

Description of embodiments First layer : PE-matrix According to a preferred embodiment of the present invention the first layer is made of polyethylene possessing the following properties : flexibility in a temperature range from -60 to +80°C, impermeability to gas , high UV resistance and ozone resistance, puncture resis- tance, blocking resistance and having low density .

Furthermore , the first layer comprises MDPE (medium density polyethylene) , LLDPE (liner low density polyethylene ) , PE-co-octene or a combination thereof . Moreover, the first layer preferably comprises 0-20% MDPE, 0-80% LLDPE and 0-100% PE-co-octene .

In the following six examples properties for various films ( PE-matrix) are presented . The films are blow- extruded to a thickness of 50μm on a extrusion pilot- plant .

Example 1. LLDPE

Property Test method Result

Tensile strength ISO 1421 11 , 0 N/6mm

Blocking resis- ISO 5978 4 , 0 MPa tance

Density ISO 1183 0 , 918 g/cm³

Puncture resis- ASTM D 1709-03 2500 g tance

Impermeable to air ISO/DIS 9650-2 0 bubbles

Low bend flex test ISO 4675 0 cracks

Example 2. MDPE

Property- Test method Result

Tensile _strength ISO 1421 10 , 2 N/6mm

Blocking resis- ISO 5978 0 MPa tance

Density ISO 1183 o, 937 g/cm³

Puncture resis- ASTM D 1709-03 250 g tance

Impermeable to air ISO/DIS 9650-2 0 bubbles

Low bend flex test ISO 4675 0 cracks

Example 3. PE-co-octene

Example 4

In a first embodiment of the invention the first layer comprises 15% MDPE, 15% LLDPE and 70% PE-co-octene

The composition of the first layer in this embodiment possesses the following properties :

Example 5

In this embodiment of the invention the first layer comprises 10% MDPE, 10% LLDPE and 80% PE-co-octene .

Example 6

In this embodiment of the invention the first layer comprises 0% MDPE, 70% LLDPE and 30% PE-co-octene .

Second layer : Textile

The second layer is preferably mainly consisting of a textile made of fibres . More preferably the second layer is made of PET being a polar material . Furthermore, the second layer may according to invention be processed into a web either by knitting or weaving, more preferably by warp knitting .

In the preferred embodiment the PET is a high tenacity polyethylene therephtalate with a breaking tenacity of 63cN/tex, 4 , 33 picks/cm and 2200 dtex .

In another embodiment the PET is a high tenacity PET with a breaking tenacity of 84cN/tex, 4 , 33 picks/cm and 2200 dtex .

Intermediate layers influence on composite materials

In the following the intermediate layers influence on the composite material will be described . The compos- ite material 1 comprises in this embodiment a first layer 2 and a third layer 2 , said first and third layers 2 substantially being made of the same material , two intermediate layers A₁ and one second layer 3 as shown in Fig . 1. Seven various functionalised polymers have been applied in composites as intermediate layers , listed in the table 1 below . All seven intermediate layers have been applied on more than four different warp knitted PET textiles . The composition of the PE-matrix were in all experiments as stated in example 4 for the first layer of an embodiment of the invention . The effects of the intermediate layer on the tensile strength measured as maximum load of the composite is presented in the following table 1 below and in Fig . 3 . Table 1 :

Intermediate layer 0- no intermediate layer is applied in the composite

Intermediate layer 1 = Ethylene grafted with acrylic acid Intermediate layer 2 = Ethylene grafted with maleic anhydride Intermediate layer 3 = Ethylene grafted with maleic anhydride Intermediate layer 4 = Ethylene copolymerised with acrylic acid Intermediate layer 5 = Ethylene copolymerised with acrylic acid Intermediate layer 6 = Ethylene copolymerised with acrylic acid Intermediate layer 7 = A terpolymer with Ethylene, butyl-acrylate and glycidyl methacrylate

In Fig . 3 a diagram is shown, wherein the effects of various intermediate layers on Maximum Load for different composite materials are presented .

From the above results it is evident that the modified functionalised polyethylenes investigated contribute positively to the final strength of the composite measured as maximum load and stress . In fact , all the applied intermediate layers , i . e . the modified functionalised polyethylenes , ensure that the strength of the composite material is increased sufficiently to fulfil the requirement of a tensile strength above 2200 N/50mm. Furthermore, it is evident that composite materials produced including intermediate layer 6, which includes ethylene-co-acrylic acid averagely yields the strongest composite material , when the respective textile is taken into consideration . In addition it is concluded that the intermediate layer 7 , a terpolymer with ethylene, butyl-acrylate and glycidyl methacrylate yields composite materials with a very high average strength .

For composite materials produced, including textile 11 intermediate layers 3 , 4 , 5 , 6 and 7 including such functionalised polyethylenes as ethylene grafted with acrylic acid, ethylene copolymerised with acrylic acid and terpolymer with ethylene, butyl-acrylate and glycidyl methacrylate, respectively all have a very positive ef- feet yielding composite materials with tensile strengths above 2400 N/50mm averagely . In one preferred embodiment said first and third layer consists of 120μm PE-matrix, second layer, the textile, consists of a PET material . The intermediate layer applied between said first layer and second layer and again between second and third layer consists of 20μm material . Said intermediate layer contains an acrylic acid .

The mechanical, chemical and physical test of said material yields the following results :

ISO 7854 * except the distance between the grips were 38mm

ISO 1431/2** except the duration of exposure were extended to 72 hours instead of 8 hours .

ISO 2411*** preparation of samples according to 4.3

In Fig . 2 is shown another embodiment of the invention wherein the composite material 1 comprises only one first layer 2 and a second layer 3 as well as an intermediate layer 4 applied therein between .

Although the invention above has been described in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims .

Claims

1. A composite material comprising at least a first layer substantially made of polyethylene ( PE ) , and a sec- ond layer consisting of a textile made of fibres , wherein a coupling component containing functional groups are applied as an intermediate layer arranged between the first layer and the second layer, hereby enabling a chemical and/or physical bonding between the first layer and the second layer .

2. Composite material as claimed in claim 1 , wherein the coupling component comprising at least a PE copoly- merised with one or more functional groups selected from the groups of : acid, epoxy, ester, anhydride, hydroxyl , ionomers , acrylate .

3. Composite material as claimed in claim 2 , wherein one or more functional groups are acrylic acid and/or maleic anhydride and/or glycidyl m-acrylate and/or butyl acrylate . 4. Composite material as claimed in any one of the preceding claims , wherein the first layer comprises one or more grades of metallocene catalysed PE derivatives .

5. Composite material as claimed in claim 4 , wherein the metallocene catalysed PE derivatives are selected from the following groups MDPE, LLDPE and PE-co-alkenes . β . Composite material as claimed in claim 5 , wherein the alkenes are selected from butene, hexene , octene , nonene , decene, preferably octene or hexene .

7. Composite material as claimed in any of the claims 4-6, wherein the first layer comprises 20-100% PE- co-alkenes , 0-20% MDPE and/or 0-80% LLDPE .

8. Composite material as claimed in any one of the preceding claims , wherein the fibres of the textile of the second layer are made of polyamide ( PA) , polyaramide ( PAA) , polyester ( PET ) , ultra high molecular weight polyethylene (UHMWPE ) , or a combination thereof . 9. Composite material as claimed in any of the preceding claims , wherein a third layer, substantially made of PE, is provided on the opposite side of the second layer in relation to the first layer and a coupling com- ponent containing functional groups are applied as an intermediate layer arranged between the second layer and the third layer, hereby enabling a chemical and/or physical bonding between the second layer and the third layer .

10. Composite material as claimed in claim 9 , wherein the first layer and the third layer substantially are made of the same material .

11. Composite material as claimed in claim 9 or 10 , wherein the intermediate layers arranged between the first and second layer and the second and third layer substantially are made of the same material .

12. Composite material as claimed in any of the preceding claims , wherein said composite material is made by extrusion .

13. Composite material as claimed in any one of the preceding claims, wherein the composite material comprises a puncture resistance above 360 N (according to FED-STD-191A, method 5120 ) .

14. Composite material as claimed in any one of the preceding claims , wherein the thickness of the composite material is between 300μm and lOOOμm, preferably between 400 and 700 μm.

15. Composite material as claimed in any one of the preceding claims , wherein the composite material comprises a coating adhesion between the first and second layer above 75N/50mm (according to ISO 2411 ) .

16. Use of the composite material according to claims 1-15 for products having inflatable compartments , such as life-saving equipment , such as floatable units like inflatable platforms , liferafts or evacuation slides .

17. Use of the composite material according to claims 1-15 for protection against liquids , coast secur- ing, tarpaulins , geo textiles , under cover for roofs , waterproof clothes or sailcloth .

18. Use of the composite material according to claims 1-15 for play ground products such as trampolines , inflatable j umping castles and the like .