Field of the Invention

The present invention relates to a protective film, and in particular to a protective film configured for attachment to rubber components.

Background to the Invention

Elastomeric materials, specifically rubber materials, are used in a variety of different industries due to their well-known material properties. For example, it is known to use rubber to produce belts and hoses.

However, rubber components often have low wear resistance, limiting their applicability to high wear applications.

Various solutions have been developed to overcome this problem. One solution is adaptation of the material structure of the rubber by use of a chemical additive, or specific processing, to improve wear resistance. Another solution is use of a protective coating to protect the rubber surface.

Coatings such as ultra-high molecular weight poly(ethylene) (UHMWPE) have been used due to their high abrasion resistance. UHMWPE also benefits from a low coefficient of friction.

However, UHMWPE has very high melt viscosity, so films are typically produced via skiving (cutting) compression moulded blocks. As a result of this manufacturing method, there is a limitation on the width and thickness of any UHMWPE film produced. UHMWPE also has poor adhesion to polar rubber materials, such as nitrile rubbers (NBR) which is a significant limitation to the use of UHMWPE as a film coating for rubber products.

There is therefore a need for improvements in coatings for rubber components.

Summary of the Invention

According to a first aspect of the invention, there is provided a method of manufacturing a component; the method comprising the steps of: providing a film, the film comprising : a protective sheet comprising a cross-linked poly(ethylene) material, a bonding sheet which can be bonded to both a polar and a non-polar substrate; and a first bond bonding the protective sheet to the bonding sheet, providing a rubber substrate;

bonding at least part of the bonding sheet of the film to at least part of the rubber substrate by means of heat and/or pressure.

The poly(ethylene) material has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. The percent by weight of cross-linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%.

The rubber substrate may be comprised in one or more of: a rubber hose; a timing belt; a transmission belt; a conveyor belt; a liner; a rubber component having a substantially constant cross-sectional shape in at least one direction.

The protective sheet may have a dynamic coefficient of friction between 0.165 and 0.175 and/or a static coefficient of friction between 0.180 and 0.190, as measured by International Organisation for Standardization standard ISO 8295.

The protective sheet may comprise one or more of: linear low density poly(ethylene), high density poly(ethylene) and medium density poly(ethylene).

The bonding sheet may be directly formed from a bonding fluid source, the bonding fluid source comprising one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, and ionomer compounds.

The bonding fluid source may comprise ethylene vinyl acetate and/or ethylene butyl acrylate.

The first bond bonding the protective sheet to the bonding sheet may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar- polar interaction bond, a hydrogen bond, a Van der Waals bond, a hydrophobic interaction.

According to a second aspect of the invention, there is provided a component comprising : a film comprising : a protective sheet comprising a cross-linked poly(ethylene) material, wherein the poly(ethylene) material has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060; a bonding sheet which can be bonded to both a polar and a non-polar substrate; and a first bond bonding the protective sheet to the bonding sheet; and

a rubber substrate;

wherein a second bond bonds the bonding sheet to at least part of the material of the rubber substrate.

The rubber substrate may be comprised in one or more of: a rubber hose; a timing belt; a transmission belt; a conveyor belt; a liner; a rubber component having a substantially constant cross-sectional shape in at least one direction.

The protective sheet may comprise one or more of: linear low density poly(ethylene), high density poly(ethylene) and medium density poly(ethylene). The percent by weight of cross-linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%.

The bonding sheet may comprise a polymeric material comprising one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, ionomer, polyamide and polyimine compounds.

The bonding sheet may comprise ethylene vinyl acetate and/or ethylene butyl acrylate.

The first bond bonding the protective sheet to the bonding sheet may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar- polar interaction bond, a hydrogen bond, a Van der Waals bond, a hydrophobic interaction.

According to a third aspect of the invention, there is provided a method of manufacturing a film, the method comprising the steps of:

directly forming a protective sheet from a fluid poly(ethylene) source such that the protective sheet comprises cross-linkable poly(ethylene) and a cross-linking agent, wherein the fluid poly(ethylene) source comprises one or more of: linear low density poly(ethylene), high density poly(ethylene) and medium density poly(ethylene); and bonding the protective sheet to a bonding sheet, the bonding sheet comprising a material which can be bonded to both a polar and a non-polar substrate by means of its chemical composition, the bonding sheet comprising at least 30 wt.% of one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, ionomer, polyamide and polyimine compounds.

The cross-linking agent may be silane and/or peroxide. The percent by weight of cross- linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%.

As a person skilled in the art will appreciate, the term "directly forming" may refer to a method in which the forming process at least partially defines the desired (i.e. suitable for its intended use) dimensions of the sheet. For example, the sheet may be directly formed such that it has a desired thickness, but may then be slit to form multiple sheets each having that same formed thickness. Methods of directly forming the sheet include but are not limited to: calendaring, blowing and casting. As a skilled person will appreciate, the term "fluid poly(ethylene) source" may refer to a molten poly(ethylene) source or a poly(ethylene) source in which the polymer is dissolved in a solvent. Preferably, the "fluid poly(ethylene) source" is a molten poly(ethylene) source. The term "linear low density poly(ethylene)" refers to poly(ethylene) having a significant number of short branches. Linear low density poly(ethylene) has a density in the range of 0.910 to 0.940 g/cm ³ . Medium density poly(ethylene) has a density in the range of 0.926 to 0.940 g/cm ³ . High density poly(ethylene) has a density in the range of 0.941 to 0.970 g/cm ³ . As a skilled person will appreciate, density may be determined by measuring the mass of the sheet, measuring the volume of the sheet, and dividing the mass by the volume of the sheet. The volume of the sheet may be determined by use of a suitable measuring technique, such as a gas pycnometer method such as the method used in test method BS EN ISO 1183-3. The mass of the sheet may be determined by use of a balance, scales or other appropriate measuring apparatus or method. High density poly(ethylene) may comprise linear poly(ethylene) chains, or may comprise non-linear poly(ethylene) chains. High density poly(ethylene) may comprise polymer chains having an average molecular weight in the range 40000 to 600000 g/mol. Medium density poly(ethylene) and linear low density poly(ethylene) may comprise polymer chains having an average molecular weight in the range 6000 to 60000 g/mol. As described above, molecular weight may be determined by a suitable technique such as gel permeation chromatography. As a skilled person will appreciate, molecular weight of a polymer can be determined, for example, by means of gel permeation chromatography, and mass spectrometry. Gel permeation chromatography may include size exclusion chromatography using a reference standard of poly(styrene) and a solvent of chloroform, conducted at room temperature and pressure. Molecular weight of a polymer may be determined using, for example a GPC/SEC system such as a "1260 Infinity II GPC/SEC system" as provided by Agilent Technologies. Medium density poly(ethylene) may comprise linear poly(ethylene) chains, or may comprise non-linear poly(ethylene) chains.

The bonding sheet may comprise a polymeric material comprising one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, ionomer, polyamide and polyimine compounds.

The bonding layer may comprise a small amount of poly(ethylene), preferably less than 2 wt.%, preferably less than 1 wt.%, further preferably less than 0.1 wt.% of the overall composition by weight. This has the advantage of adding colour to the bonding layer. The step of bonding the protective sheet to a bonding sheet may comprise forming a direct bond between the protective sheet and the bonding sheet. The direct bond may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar-polar interaction bond, a hydrogen bond, a Van der Waals bond, a hydrophobic interaction.

The method may further comprise the step of cross-linking the poly(ethylene) source such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Other possible methods for measuring corresponding abrasion properties are ISO 4649 or ASTM D5963. Preferably the method of manufacturing the film comprises the step of cross-linking the poly(ethylene) source such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 8 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably the method of manufacturing the film comprises the step of cross-linking the poly(ethylene) source such that the resulting poly(ethylene) has a wear index in the range of 3 mg per 1000 cycles to 5 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. As a skilled person will appreciate, the term "cross-linking" refers to forming a series of bonds which link one polymer chain to another. Specifically, cross-linked polymer chains may be bonded such that a non- linear arrangement of polymer chains is produced. Cross-linked polymer chains may produce a three dimensional network of polymer chains. The series of bonds may be chemical (e.g. covalent) bonds, physical bonds, or a combination of both chemical and physical bonds. The terms "cross-linking" or "activating cross-linking" may involve combining a polymer source, such as a fluid poly(ethylene) source, with a catalyst. The terms "cross-linking" or "activating cross-linking" may involve initiation and/or promotion of cross-linking through the action of heat and/or light. The terms "cross- linking" or "activating cross-linking" may involve exposing a polymer source and catalyst to atmospheric gas. The terms "cross-linking" or "activating cross-linking" may involve exposing a polymer source and catalyst to water, such as water present in atmospheric gas. The terms "cross-linking" or "activating cross-linking" may involve spontaneous cross-linking, for example at room temperature and pressure.

The method may further comprise the step of providing the bonding sheet, wherein the bonding sheet comprises a material in a solid state at room temperature. As a skilled person will appreciate, references herein to "room temperature" refers to a temperature in the range of 15 °C to 25 °C.

The step of directly forming a protective sheet may comprise calendaring the fluid poly(ethylene) source.

The step of directly forming a protective sheet may comprise blowing the fluid poly(ethylene) source.

The step of directly forming a protective sheet may comprise directly casting a sheet from the fluid poly(ethylene) source.

The method may further comprise the step of providing the bonding sheet by directly forming the bonding sheet from a bonding fluid source.

The bonding fluid source may comprise one or more of: acetate; acrylate; methacrylate; acrylic acid; methacrylic acid; ionomer compounds. The bonding fluid source may comprise ethylene vinyl acetate. The bonding fluid source may comprise ethylene butyl acrylate.

The steps of: directly forming the protective sheet; and directly forming the bonding sheet, may be performed simultaneously.

The steps of: directly forming the protective sheet from a fluid poly(ethylene) source; and directly forming the bonding sheet from a bonding fluid source; and bonding the protective sheet to the bonding sheet, may be performed simultaneously.

The fluid poly(ethylene) source may be a molten poly(ethylene) source. The method may further comprise the step of rolling the film, wherein the film has only two layers of different materials per roll. One of the, or each of the, layers of material may have a plurality of sub-layers. The resulting roll may comprise a spiral arrangement, such that the spiral extends out from the centre of the roll to the outermost radial point of the roll. The roll may comprise alternating layers of protective sheet and bonding sheet in a radial direction of the roll. Each layer of protective sheet may be a single layer or have a plurality of sub-layers of protective sheet material. Equally, each layer of bonding sheet may be a single layer or have a plurality of sub-layers of bonding sheet material.

The film may consist of two main layers, with one main layer being the protective sheet and the other main layer being the bonding sheet. Each main layer may consist of a plurality of sub-layers of the main layer material. The roll may consist of the film.

According to a fourth aspect of the invention, there is provided a film comprising : a protective sheet comprising a cross-linked poly(ethylene) material, which is cross-linked by means of a cross-linking agent, wherein the poly(ethylene) material has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060; a bonding sheet which can be bonded to both a polar and a non-polar substrate, the bonding sheet comprising at least 30 wt.% of one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, ionomer, polyamide and polyimine compounds; and a first bond bonding the protective sheet to the bonding sheet.

The percent by weight of cross-linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%.

The cross-linking agent may be silane and/or peroxide. Preferably, the poly(ethylene) material has a wear index in the range of 1 mg per 1000 cycles to 8 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the poly(ethylene) material has a wear index in the range of 3 mg per 1000 cycles to 5 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. The percent by weight of cross-linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%. Preferably, the cross-linked poly(ethylene) may comprise at least 90% by weight poly(ethylene). Further preferably, the cross-linked poly(ethylene) may comprise at least 95% by weight poly(ethylene). The bonding sheet may comprise a polymeric material comprising one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid ionomer, polyamide and polyimine compounds; and wherein the first bond is a direct bond which is one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar- polar interaction bond, a hydrogen bond, a Van der Waals bond, and a hydrophobic interaction.

The bonding sheet may comprise ethylene vinyl acetate. The bonding sheet may comprise ethylene butyl acrylate.

The film may consist of two layers of material, with one layer being the protective sheet and the other layer being the bonding sheet.

There may be provided a component comprising : a film as described above and a rubber substrate; wherein a second bond bonds the bonding sheet to at least part of the material of the rubber substrate.

According to a fifth aspect of the invention, there is provided a method of manufacturing a component; the method comprising the steps of: providing a rubber substrate; providing a protective sheet from a fluid poly(ethylene) source such that the protective sheet comprises cross-linkable poly(ethylene), wherein the fluid poly(ethylene) source comprises one or more of: linear low density poly(ethylene), high density poly(ethylene) and medium density poly(ethylene); activating cross-linking of the protective sheet; and bonding the protective sheet to at least part of the rubber substrate.

The percent by weight of cross-linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%.

The step of bonding the protective sheet to at least part of the rubber substrate may comprise forming a direct bond between the protective sheet and at least part of the rubber substrate. The direct bond may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar-polar interaction bond, a hydrogen bond, a Van der Waals bond, a hydrophobic interaction. The step of activating cross-linking of the poly(ethylene) source may involve activating cross-linking such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the step of activating cross-linking of the poly(ethylene) source involves activating cross-linking such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 8 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the step of activating cross-linking of the poly(ethylene) source involves activating cross-linking such that the resulting poly(ethylene) has a wear index in the range of 3 mg per 1000 cycles to 5 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. The step of activating cross-linking of the poly(ethylene) source may comprise exposing the poly(ethylene) source to an atmospheric environment. The step of activating cross-linking of the poly(ethylene) source may comprise exposing the poly(ethylene) source to moisture. Such moisture may be moisture typically present in the air. The step of activating cross-linking of the poly(ethylene) source may comprise steam curing the poly(ethylene) source. Steam curing may be carried out in an autoclave. Steam curing may be carried out for an hour.

The rubber substrate may be comprised in a rubber hose. The rubber substrate may be comprised in a timing belt. The rubber substrate may be comprised in a transmission belt. The rubber substrate may be comprised in a conveyor belt. The rubber substrate may be comprised in a liner. The rubber substrate may be comprised in a rubber profile.

According to a sixth aspect of the invention, there is provided a component comprising : a rubber substrate;

a protective sheet comprising cross-linked poly(ethylene) material having a wear index in the range of 1 mg / 1000 cycles to 12 mg / 1000 cycles; and

a bond bonding the protective sheet to at least part of the rubber substrate.

Preferably, the protective sheet comprising cross-linked poly(ethylene) material has a wear index in the range of 1 mg / 1000 cycles to 8 mg / 1000 cycles. Preferably, the protective sheet comprising cross-linked poly(ethylene) material has a wear index in the range of 3 mg / 1000 cycles to 5 mg / 1000 cycles. The percent by weight of cross- linked poly(ethylene) material in the protective sheet may be at least: 30 wt.%, 60 wt.%, 90 wt.%, or 95 wt.%.

The bond may be a direct bond between the protective sheet and at least part of the rubber substrate. The direct bond may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar-polar bond, a hydrogen bond, a Van der Waals bond, a hydrophobic interaction. The step of rolling the film may provide a continuous roll having two sheets disposed as layers in a spiral arrangement, such that the spiral extends out from the centre of the roll to the outermost radial point of the roll.

Brief Description of the Drawings

Embodiments of the present invention will now be described, by non-limiting example only, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic of a film according to an embodiment of the invention;

Figure 2 shows a schematic of a component according to an embodiment of the invention;

Figure 3 shows an apparatus being used for the manufacture of the film by a blown process;

Figure 4 is a schematic representing the method steps of the manufacture of figure 3; Figure 5 shows an apparatus being used for the manufacture of the film by a cast process;

Figure 6 is a schematic representing the method steps of the manufacture of figure 5; Figure 7 is a schematic of a component according to an embodiment of the invention; Figure 8 shows a method of applying the film to coat a rubber hose; and

Figure 9 shows a method of applying the film to a rubber sheet.

Description of Embodiments of the Invention

The following detailed description and figures provide examples of how the present invention can be implemented and should not be seen as limiting examples, rather illustrations of how the various features of the film disclosed herein can be combined, although other optional combinations will be evident upon a reading of the following description in light of the figures.

The film

As shown by the schematic in Figure 1, there is provided a film 1 comprising : a protective sheet 100 comprising a cross-linked poly(ethylene) material, and a bonding sheet 200 which can be bonded to both a polar and a non-polar substrate. The term "substrate" used herein, as a skilled person will appreciate, is not restricted in terms of shape or configuration. A first bond bonds the protective sheet 100 to the bonding sheet 200. Specifically, the bonding sheet 200 can be bonded to both polar and non-polar rubber substrates. Examples of such rubber substrates include, but are not limited to acrylic (ACM), butyl (HR, eg. a co-polymer of isobutylene and isoprene), epichlorohydrin (CO), ethylene acrylate (AEM), chlorinated polyethylene (CPE), chlorosulphonated polyethylene (CSM), ethylene propylene (EPM and EPDM), nitrile (NBR), natural (NR), butadiene (BR), chlorobutyl (CIIR), isoprene (IR), polychloroprene (CR), polysulphide (TR), styrene butadiene styrene (SBR), polyurethane (AU and EU) and hydrogenated nitrile (HNBR eg. a hydrogenated nitrile and butadiene co-polymer) rubbers.

The protective sheet 100 comprises poly(ethylene) material having a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the protective sheet 100 comprises poly(ethylene) material having a wear index in the range of 1 mg per 1000 cycles to 8 mg per 1000 cycles. Preferably, the protective sheet 100 comprises poly(ethylene) material having a wear index in the range of 3 mg per 1000 cycles to 5 mg per 1000 cycles.

The bonding sheet 200 may comprise a polymeric material comprising one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, ionomer, polyamide and polyimine compounds. The bonding sheet 200 may comprise ethylene vinyl acetate. The bonding sheet 200 may comprise ethylene butyl acrylate.

The first bond may be a direct bond which is one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar-polar interaction bond, and a hydrogen bond, a Van der Waals bond, a hydrophobic interaction.

The film 1 may consist of two layers of material, in which one layer is the protective sheet 100 and the other layer is the bonding sheet 200.

There may be provided a layer of a suitable polymer such as poly(ethylene) and/or poly(propylene) between the protective sheet 100 and the bonding sheet 200. As a skilled person will appreciate, a layer of another suitable polymer material could be provided between the protective sheet 100 and the bonding sheet 200. Method of manufacturing the film

As a skilled person will appreciate, there may be more than one method of manufacturing the film described above. Herein there is provided a method of manufacturing an embodiment of the film, the method comprising the steps of:

1) directly forming a protective sheet 100 from a fluid poly(ethylene) source; and

2) bonding the protective sheet to a bonding sheet 200.

The fluid poly(ethylene) source of the first step comprises cross-linkable poly(ethylene), and the fluid poly(ethylene) source comprises one or more of: linear low density poly(ethylene), high density poly(ethylene) and medium density poly(ethylene).

The bonding sheet 200 comprises a material which can be bonded to both a polar and a non-polar substrate by means of its chemical composition. The bonding sheet 200 may comprise a polymeric material comprising one or more of: acetate, acrylate, methacrylate, acrylic acid, methacrylic acid, ionomer, polyamide and polyimine compounds.

The step of bonding the protective sheet to the bonding sheet 200 may comprise forming a direct bond between the protective sheet 100 and the bonding sheet 200. The direct bond may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a polar-polar interaction bond, a hydrogen bond, a Van der Waals bond, a hydrophobic interaction. As used herein, the term "direct bond" may refer to a bond on a molecular scale, as opposed to a macroscopic adhesive. The method may further comprise the step of cross-linking the poly(ethylene) source such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the method further comprises the step of cross-linking the poly(ethylene) source such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 8 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the method further comprises the step of cross-linking the poly(ethylene) source such that the resulting poly(ethylene) has a wear index in the range of 3 mg per 1000 cycles to 5 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Chemical Precursors

As used herein, the term "precursor" refers to any component which is present at a starting or intermediate stage of the manufacturing process. The term "precursor" may for example, refer to a reagent or catalyst.

As starting materials, there may be provided a primary precursor 110, a secondary precursor 112, a tertiary precursor 120 and a bonding material 202, as represented in Figure 3.

The primary precursor 110 referred to herein may comprise poly(ethylene) fluid such as LLDPE, MDPE or HDPE. The secondary precursor 112 may comprise a cross-linking agent such as silane and/or peroxide compounds. The primary precursor 110 and the secondary precursor 112 may be mixed. The mixture may then comprise a thermally cross-linkable poly(ethylene), such as a silane cross-linkable poly(ethylene). As a skilled person will appreciate, the term "thermally cross-linkable" indicates a material which can become cross-linked upon application of heat. This may be by means of a cross-linking agent, which is activated or facilitated by heat.

Equally or alternatively, a thermally cross-linkable poly(ethylene), such as a silane cross- linkable poly(ethylene) may be provided. The silane cross-linkable poly(ethylene) may have a density of 0.952 g/cm ³ , according to test method BS EN ISO 1183-3. The silane cross-linkable poly(ethylene) may, in a cross-linked state, have a tensile strength of 20 to 30 N/mm ² , preferably 23 to 27 N/mm ² , preferably 24 N/mm ² according to test method IEC 60811-501. The silane cross-linkable poly(ethylene) may, in a cross-linked state, have an elongation at break of 300 to 600%, preferably 500 to 550%, preferably 540% according to test method IEC 60811-501. The silane cross-linkable poly(ethylene) may, in a cross-linked state, have a gel content in the range of 60% to 80%, preferably 70% according to ASTM D2765-11. The primary, secondary and tertiary precursors 100, 112 and 120 may be combined and are hereafter referred to in the process as the "protective sheet mixture". Specifically, the protective sheet mixture may comprise a mixture of 95 wt.% PEXIDAN (RTM) CT17 and 5 wt.% CM488 catalyst masterbatch as provided by Saco AEI Limited.

As a skilled person will appreciate that the term "masterbatch" refers to a mixture of pigments and/or additives which has been encapsulated by means of a heat process into a carrier resin. The protective sheet mixture may comprise a mixture of between 92 wt.% and 95 wt.% PEXIDAN (RTM) CT17, between 3 wt.% and 7 wt.% CM488 catalyst masterbatch as provided by Saco AEI Limited and between 1 wt.% and 2 wt.% colour masterbatch. The protective sheet mixture may comprise a mixture of 93.5 wt.% PEXIDAN (RTM) CT17, 5 wt.% CM488 catalyst masterbatch as provided by Saco AEI Limited and 1.5 wt.% colour masterbatch.

The tertiary precursor 120 referred to herein may comprise a colour masterbatch and/or a catalyst masterbatch. The catalyst masterbatch may comprise CM488 as provided by Saco AEI Limited.

The bonding material 202 referred to herein is a material which can be bonded to both a polar and a non-polar substrate by means of its chemical composition. The bonding material 202 may comprise a material which is in a solid state at room temperature. The bonding material 202 may be provided as a fluid source. The bonding material 202 may be provided as a molten source. The bonding material 202, specifically the bonding fluid source may comprise one or more of: acetate; acrylate; acrylic acid; methacrylate; methacrylic acid; ionomer compounds. The bonding material 202, specifically the bonding fluid source may comprise ethylene vinyl acetate. The bonding material 202, specifically the bonding fluid source may comprise ethylene butyl acrylate. Specifically, the bonding material 202 may comprise a mixture of Elvax (RTM) 3170 ethylene vinyl acetate and between 5 and 10 wt.%, preferably 7 wt.% Elvax (RTM) CE-9619 anti- blocking agent, as provided by DowDuPont (RTM).

As a skilled person will appreciate, use of an anti-blocking agent has the advantage of allowing separation of film layers from each other, during or after processing. The anti- blocking agent may allow separation of film layers from each other by forming micro bumps on the surface of the film, and restricting adhesion of two film layers (for example, the bonding of a bonding layer of one film sheet to the protective layer of another film sheet, when the two film sheets are stacked one on top of the other). As a skilled person will equally appreciate, various different anti-blocking agents could be used. The anti-blocking agent may comprise an organic or an inorganic material. The type and quantity of anti-blocking agent chosen for a blowing manufacturing process (described below) will depend on the specific blowing process machinery used, and temperature of bubble formed, as described below. Method of manufacture

The step of directly forming a protective sheet may comprise calendaring the fluid poly(ethylene) source. The step of directly forming a protective sheet may comprise blowing the fluid poly(ethylene) source, or directly casting a sheet from the fluid poly(ethylene) source. The bonding sheet 200 may be provided by directly forming the bonding sheet from a bonding fluid source.

Blowing manufacture process

The step of directly forming a protective sheet may comprise blowing the fluid poly(ethylene) source, as shown in the schematics of Figures 3 and 4.

At a first stage 510, primary and secondary precursors 100 and 112 may be provided. The primary precursor 110 may be the fluid poly(ethylene) source. The secondary precursor 112 may comprise one or more of silane compounds or peroxide compounds (e.g. dicumyl peroxide). These precursors may be mixed during the first stage 510.

At a second stage 520, a tertiary precursor 120 may be added to the primary and secondary precursors 100 and 112. The tertiary precursor 120 may be one or both of a catalyst or colour masterbatch. The primary, secondary and tertiary precursors 100, 112 and 120 may be combined during the second stage 520, and are hereafter referred to in the process as the "protective sheet mixture".

At a third stage 530, which may be performed simultaneously with the second stage 520, a bonding material 202 which can be bonded to both a polar and a non-polar substrate by means of its chemical composition is provided. The third stage may also be performed simultaneously with the first stage 510.

The second and third stages 520, 530 may be carried out simultaneously so as to provide a continuous process, and the first stage 510 may be carried out separately. Equally, the first, second and third stages 510, 520, 530 may be carried out simultaneously so as to provide a continuous process.

At a fourth stage 540, the protective sheet mixture may be extruded through a die 10 to provide a protective sheet 100. The die 10 may be maintained at a temperature such that the protective sheet mixture does not exceed or fall below the temperature range of 140 °C to 190°C, preferably 150 °C to 170 °C, when passing through the die 10. The bonding material 202 may be extruded through the die 10, or through a separate die 12 to provide a bonding sheet 200, such that the "protective sheet mixture" and the bonding material 202 are extruded together. At this stage, air may be blown through the centre of the die to expand the film into a bubble. The die 10 and the die 12 may be the same component, such that the "protective sheet mixture" and the bonding material 202 are extruded together. The die 10, 12 may be configured so as to bring the two polymer compositions together.

Formation of the protective sheet 100 and formation of the bonding sheet 200 may be performed simultaneously.

At the fourth stage 540, the protective sheet 100 may be bonded to the bonding sheet 200. The step of bonding the protective sheet 100 to the bonding sheet 200 may be performed simultaneously with formation of the protective sheet 100 and formation of the bonding sheet 200.

At a fifth stage 550, the protective sheet 100 and the bonding sheet 200 may be passed away from the die 10 following extrusion. In particular, the protective sheet and the bonding sheet may be pulled vertically upwards away from the die 10, as represented in Figure 3. This may result in a sheet of protective sheet mixture and a sheet of bonding material, which may be separated from each other by an air gap to define the bubble. Specifically, one of the protective sheet and bonding sheet may form an outer layer, and the other of the protective sheet and bonding sheet may form an inner layer. The inner and outer layers may be next to each other by virtue of their extrusion through the die 10. Each of the outer and inner layers may have a tubular configuration, or a bubble configuration. The tubular configuration may be arranged so as to extend having a central axis aligned vertically with the die 10.

At a sixth stage 560, the tubular film may be passed through rollers 20. Each layer of the tubular film has one layer of the protective sheet 100 and one layer of the bonding sheet 200, as represented in figure 1. At this stage the bubble formed from air being extruded through the die 10 may be collapsed, which may comprise cutting the bubble. This may give two sheets of material, each comprising a protective sheet 100 and a bonding sheet 200 as represented in Figure 1. The sheets of material may then be slit into an appropriate width of film. The two sheets of material, or "films" 1, may then, in a seventh stage 570, each be rolled up into a roll arrangement 30. There may be provided a continuous roll having two layers: one layer of the protective sheet 100 and one layer of the bonding sheet 200. The roll 30 may consist of two layers of material, with one layer being the protective sheet 100 and the other layer being the bonding sheet 200.

Casting manufacture process

The step of directly forming a protective sheet may comprise directly casting a sheet from the fluid poly(ethylene) source, as shown in the schematics of Figures 5 and 6.

Similar to the blowing manufacture process, at a first stage 610, first and second precursors 110 and 112 may be provided. The primary precursor 110 may be the fluid poly(ethylene) source. The secondary precursor 112 may comprise one or more of silane or peroxide. These precursors may be mixed during the first stage 610.

At a second stage 620, a tertiary precursor 120 may be added to the primary and second precursors 110 and 112. The tertiary precursor 120 may be a colour and/ or catalyst masterbatch. The catalyst masterbatch may for example be CM488 as provided by Saco AEI Limited. The primary, secondary and tertiary precursors 110, 112 and 120 may be combined during the second stage 620, and are hereafter referred to in the process as the "protective sheet mixture".

At a third stage 630, which may be performed simultaneously with second stage, 620, a bonding material 202 which can be bonded to both a polar and a non-polar substrate by means of its chemical composition is provided. The third stage 630 may be performed simultaneously with the first stage 610.

The second and third stages 620, 630, may be carried out simultaneously so as to provide a continuous process, and the third stage may be carried our separately. Equally, the first, second and third stages 610, 620, 630, may be carried out simultaneously so as to provide a continuous process.

At a fourth stage 640, the protective sheet mixture may be extruded through a die 11 to give a protective sheet. The bonding material 202 may also be passed through a die 11 to give a bonding sheet. The protective sheet and the bonding sheet may bond together to form the film 1. The bonding together of the protective sheet and the bonding sheet may occur as the protective sheet mixture and the bonding material 202 are extruded through the die 11.

At a fifth stage 650, the film 1 may be passed between a first pair of rollers 15. The rollers 15 may be chilled rollers. Specifically, the rollers 15 may be actively cooled such that they have a temperature below room temperature.

At a sixth stage 660, the film 1 may be passed through a second pair of rollers 16. There may be provided several rollers 16. Several rollers 16 may act as a guide to direct film 1.

At a seventh stage 670 the resulting film 1 may be rolled up into a roll. The film 1 may be cut so as to provide neat edges of the film in this stage.

Component comprising the film and a substrate

There may be provided a component 2 comprising a protective sheet 100, a bonding sheet 200 and a rubber substrate 300, as represented in the schematic of figure 2. The protective sheet 100 and bonding sheet 200 may form the film 1 as described previously.

The film 1 may have a low coefficient of friction, and high wear resistance. The film 1 therefore finds potential uses as a coating to rubber substrates in various industries.

The rubber substrate 300 may be comprised in one or more of: a rubber hose; a timing belt; a transmission belt; a conveyor belt; a liner; a rubber profile.

Rubber hoses may include but are not limited to: industrial hoses; and hydraulic hoses.

As a skilled person will appreciate, a timing belt may be a flexible belt with teeth moulded onto a surface. A timing belt may run over matching toothed pulleys or sprockets. It may be used to transfer motion for timing purposes, and is often used instead of chains or gears because no lubrication needed and there is less resulting noise. Timing belts may be used in different applications, including but not limited to: sewing machines, photocopiers, driving camshafts, balancer shafts, fuel injection pumps or water pumps, and high power transmissions. The film 1 may be applied to the toothed side of a timing belt. Use of the film 1 on a timing belt may reduce the coefficient of friction of the belt, which is particularly advantageous as the belt meshes with pulley teeth. Use of the film 1 provides a surface having improved wear resistance. Use of the film 1 in this way may extend the life of the timing belt, leading to smoother teeth engagement, lower noise, and lower energy consumption.

As a skilled person will appreciate, a conveyor belt may be a continuous band of moving rubber used for transporting objects from one place to another. Conveyor belts are typically used in assembly lines (including but not limited to: food processing, automotive manufacturing, electronics production, packaging, recycling, agricultural, printing, pharmaceutical, mining industries, and mail sorting) and display lines such as baggage display lines in airports. Use of the film 1 on a conveyor belt may extend wear resistance of the component, lower noise in use and may lower energy consumption. Use of the film 1 may also provide a chemically resistant barrier on the conveyor belt surface.

A transmission belt may refer to any elastomeric component suitable for power transmission.

A liner is used in applications where low friction and high abrasion resistance are required. This includes but is not limited to: industrial liners for chutes, hoppers, bins and bunkers and also truck bed liners.

Rubber profiles may refer to any component which is provided having a constant cross- sectional profile in at least one direction. This may be a result of the manufacture of the rubber profile, which may be formed by extrusion. Uses of rubber profiles include but are not limited to uses in the automotive industry, the building and construction industry, the marine industry and agriculture. In the automotive industry, rubber profiles may be used any place where an interior compartment must be sealed from the environment. Such sealing may keep interior air inside a vehicle for example, thus saving energy that would otherwise be spent on heating or air conditioning. Examples include uses around coach (and haulage vehicle) windows, doors, floors and any interior trim. A rubber profile in such an application must be flexible so as to accommodate vibrations and movement, endure varying temperatures, withstand sun exposure, and be chemically resistant automotive liquids (e.g. oil, petrol, cleaning fluids), sealing noise. In the building and construction industry, rubber profiles may be used to seal: doors and /or windows, roofing, cladding, and drainage systems. Such rubber profiles may seal a building from an exterior environment, thus increasing interior comfort, lowering utility bills and reducing noise from outside the building. Rubber profiles may be used in the marine industry to provide water-tight seals. Such seals find uses sealing passenger and cargo areas external environments, and providing a watertight seal where required. Rubber profiles may be used in agriculture for sealing barns and silos, and gaskets for farm machinery.

The rubber substrate 300 may be used in noise reduction applications, for example to reduce noise when components are in frequent contact and may rub against each other and create noise or wear during movement. Such contact may compromise the function and/or life of the materials. Possible applications related to noise reduction include automobile applications (for example for seat belt buckles, damping vibrations in dashboards, doors and roofs), industrial liners, conveyor chutes and drawers and cabinet slides.

The component 2 may be configured such that a second bond bonds the bonding sheet 200 of the film 1 to at least part of the material of the rubber substrate 300.

Method of manufacturing the component

There is provided a method comprising the steps of:

providing a rubber substrate;

providing a protective sheet from a fluid poly(ethylene) source such that the protective sheet comprises cross-linkable poly(ethylene), wherein the fluid poly(ethylene) source comprises one or more of: linear low density poly(ethylene), high density poly(ethylene) and medium density poly(ethylene);

activating cross-linking of the protective sheet; and

bonding the protective sheet to at least part of the rubber substrate.

The step of bonding the protective sheet to at least part of the rubber substrate may comprise forming a direct bond between the protective sheet and at least part of the rubber substrate. The direct bond may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a Van der Waals bond, a hydrophobic interaction.

The step of activating cross-linking of the poly(ethylene) source may involve activating cross-linking such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the step of activating cross-linking of the poly(ethylene) source involves activating cross-linking such that the resulting poly(ethylene) has a wear index in the range of 1 mg per 1000 cycles to 8 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060. Preferably, the step of activating cross-linking of the poly(ethylene) source involves activating cross-linking such that the resulting poly(ethylene) has a wear index in the range of 3 mg per 1000 cycles to 5 mg per 1000 cycles, as measured by the American Standard for Testing and Materials (ASTM) D4060.

As specified above, the rubber substrate 300 may be comprised in one or more of: a rubber hose; a timing belt; a transmission belt; a conveyor belt; a liner; a rubber profile.

The method of manufacturing the component 2 may comprise the steps of manufacturing a film 1 as described previously, and may also comprise the steps of: providing a rubber substrate; and

bonding at least part of the bonding sheet of the film to at least part of the rubber substrate by means of heat and/or pressure.

A method of using the film 1 to coat a rubber hose is shown in Figure 8. In figure 8, there is provided a first process drum 801, a second process drum 802 and a roll of the film 810. The first process drum 801 may comprise an uncoated, uncured rubber hose. In between the first and second process drums 801, 802, the rubber hose is coated with the film 1, which is provided by unrolling a roll of the film 810. The film 1 may be coated around a rubber hose in a spiral or helical arrangement, such that the spiral extends along a longitudinal direction of the roll as demonstrated in Figure 8. The film 1 may equally be coated around the rubber hose in a cigarette (longitudinal) arrangement. As represented in figure 8, the coated, uncured hose may then be rolled onto the second process drum 802.

The rubber hose on the second process drum 802 may then be cured so as to show elastomeric properties. The drum 802 may be put inside an autoclave and heated at a temperature above room temperature and a pressure above atmospheric pressure, in a water saturated atmosphere. Typically, the preferred temperature range is 140 °C to 190°C, preferably 150 to 170°C and the preferred time for curing is in the range of 30 and 120 minutes, preferably 60 to 80 minutes. As a skilled person will appreciate, the preferred curing time and temperature may depend on the specific rubber substrate used. During this curing stage bonds form between the bonding layer and the rubber material.

A method and apparatus for applying the film 1 to a rubber substrate 300 in the form of a rubber sheet is shown in Figure 9. The rubber sheet may be, or may be used to produce a product such as a conveyor belt. As shown in figure 9, there may be provided a first roll 901 which comprises an uncoated rubber sheet. There may also be provided a second roll 902 which comprises the film 1. There may also be provided a hydraulic press 920 comprising an upper heating block 922 and a lower heating block 924. The hydraulic press 920 may also comprise a pressure block 926. The upper and lower heating blocks may be heated to a temperature in the range of 140 °C to 190°C, preferably 150 °C to 170 °C. The pressure block 926 may be configured to exert a pressure sufficient to hold the rubber sheet and the bonding layer together. As shown in Figure 9, the first roll 901 and the second roll 902 may be unrolled simultaneously. The film 1 and the rubber sheet unrolled from the first and second rolls 901, 902 respectively may be passed between the upper and lower heating blocks 922, 924 of the hydraulic press 920. Pressure and heat may be applied to the film 1 and the rubber sheet, so as to fix the film 1 to the rubber sheet. Specifically, the bonding layer 200 of the film 1 is pressed against the rubber sheet, and the film 1 and the rubber sheet are heated at a pressure sufficient to hold the film 1 and the rubber sheet together, so as to fix the film 1 to the rubber sheet. A component comprising a protective layer 100, a bonding layer 200 connected to the protective layer by a first bond, and a rubber substrate connected to the bonding layer 200 by means of a second bond, is then passed out of the hydraulic press 920.

There may be provided a component 3 comprising :

a rubber substrate 300;

a protective sheet 100 comprising cross-linked poly(ethylene) material having a wear index in the range of 1 mg / 1000 cycles to 12 mg / 1000 cycles; and

a bond bonding the protective sheet to at least part of the rubber substrate.

The bond may be a direct bond between the protective sheet 100 and at least part of the rubber substrate 300. The direct bond may be one or more of: a physical interaction at the molecular level, a chemical (e.g. covalent) bond, a Van der Waals bond, a hydrophobic interaction.

Example

Hereinafter, an example of the present invention will be specifically described. This example applies to the blown film manufacturing method, however as a skilled person will appreciate, various factors outlined for this method are appropriate for the other methods described herein. 95 Kg of PEXIDAN (RTM) CT17 and 5 Kg of CM488 catalyst masterbatch as provided by Saco AEI Limited were mixed in to give the protective sheet mixture. The protective sheet mixture was passed through an extruder at around 170°C, to form the "protective sheet mixture".

93 Kg of Elvax (RTM) 3170 ethylene vinyl acetate and 7 Kg of Elvax (RTM) CE-9619 anti- blocking agent, as provided by DowDuPont (RTM), were mixed to give a bonding material 202. The bonding material was passed through an extruder at 170°C to form the fluid bonding material 202.

The protective sheet mixture and the fluid bonding material 202 were passed through a die having an extrusion diameter in the range of 20 mm to 3000 mm to form the protective sheet 100 and the bonding sheet 200, respectively. By means of the die, the protective sheet 100 and the bonding sheet 200 are pressed together. The protective sheet 100 and the bonding sheet 200 are then arranged as specified above in relation to the blown film manufacturing process.

Wear testing

Using American Standard for Testing and Materials (ASTM) D4060 as applied to the protective sheet 100 side of the film manufactured as directed in the Example given above, the wear index of the protective sheet 100 was found to be in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles.

Advantageous Properties

Abrasion resistance

As explained above, a film manufactured as directed herein has advantageous abrasion resistance. In one example, the film has a wear index in the range of 1 mg per 1000 cycles to 12 mg per 1000 cycles.

Chemical resistance

A film manufactured as directed herein also has advantageous chemical resistance.

The film manufactured according to the present invention has been tested against various substances, and has demonstrated chemical resistance at at least 25°C to at least each of: organic solvents; oils; organic acids; inorganic acids; foodstuffs; oxidants; and reducing agents.

Examples of organic solvents tested include: methanol; benzene; and ethanol. Examples of oils include: amyl acetate; nitrobenzene; fish oil and colza oil. Examples of organic acids tested include: acetic acid; citric acid; and formic acid. Examples of inorganic acids tested include: sulphuric acid; hydrochloric acid; and hydrofluoric acid. Examples of foodstuffs tested include: animal fats; beer; and butter. Examples of oxidants tested include: hydrogen peroxide; ozone; and nitric acid. Examples of reducing agents tested include carbon monoxide.

The protective sheet manufactured according to the present invention has been found to have a better chemical resistance than UHMWPE to various chemical substances.

The following chemical resistance test method was used to assess the chemical resistance of UHMWPE and the chemical resistance of a protective sheet manufactured according to the present invention.

A sample of the tested material was immersed into a chemical substance. A visual test, as well as a mass comparison test, was used to determine whether the material would be suitable for use in contact with that substance, suitable for limited use with that substance, or not suitable for use in contact with that substance.

Specifically, if the sample of test material showed no change in appearance, the sample was judged to be suitable for use in contact with that substance. If the sample of test material showed a change in appearance such as swelling or cracking, it was judged to be not suitable for use in contact with that substance. If the sample of test material showed a slight change in appearance, such as minor swelling, it was judged to be acceptable only for limited use.

When tested at 25°C, according to the method specified above, UHMWPE was judged according to the principles described above to only be acceptable for limited use, while the protective sheet manufactured according to the present invention was judged according to the principles described above to be suitable for use, with each of the following substances: alkyl benzene; bromoform; butyl bromide; carbon disulphide; chlorine gas dry; difluorodichloromethane; ethyl benzene; Freon 12; javelle water; methyl bromide; naphthenic acid; ortho-dichlorobenzene; and tetrahydronaphthalene. When tested at 25°C, according to the method specified above, UHMWPE was found to be not suitable for use, while the protective sheet manufactured according to the present invention was found to be suitable for use, with aqua regia.

When tested at 70°C, according to the method specified above, UHMWPE was found to be only be acceptable for limited use, while the protective sheet manufactured according to the present invention was found to be suitable for use, with each of the following substances: sulphuric acid 50%; and sulphuric acid 92%.

Coefficient of friction

A film manufactured as directed herein also has a low coefficient of friction.

The film may have a dynamic coefficient of friction between 0.165 and 0.175 and/or a static coefficient of friction between 0.180 and 0.190, as measured by International Organisation for Standardization standard ISO 8295.

Application to component

In one embodiment, the film described herein is applied to a transmission belt. By applying the film described herein to a transmission belt, a transmission belt having a low coefficient of friction by means of the film is provided. Specifically, the outer surface of the transmission belt, which comprises the film, has the low coefficient of friction of the film.

Use of the film having a low coefficient of friction has various associated advantages when applied to a component having a rubber substrate. These advantages are particularly apparent when the film is applied to a component having a dynamic rubber substrate. Examples of a component having a dynamic rubber substrate include belts, such as transmission belts, timing belts and conveyor belts, in which the rubber substrate is designed to move in use.

One advantage of using the film described herein on a component having a rubber substrate is that energy savings may be made. Due to the low coefficient of friction of the film, some energy that would otherwise be lost to friction during movement of the belt may be saved. Another advantage of using the film described herein on a component having a rubber substrate is that the useful life of the component may be increased. This may be a result of less heating due to friction of the component, which in turn improves the expected life of the component, specifically any rubber part of the component.

In one embodiment, the film when applied to a conveyor belt has been found to significantly improve the life of the conveyor belt. As a skilled person will appreciate, certain conveyor belts can be arranged to move in a cyclical path between an outer area, and in inner area, which may be located within a housing, and may be below the outer area. When moving through the inner area, the belt may come into contact with surrounding parts, which may cause friction between the belt and the surrounding part. By applying the film described herein to the belt, the belt has a lower coefficient of friction than a belt without the film applied. By using the film, which provides a belt having a lower coefficient of friction, less heat is generated by friction between the belt and any surrounding parts. It has been deduced that since heating can reduce the lifetime of the rubber belt, use of the film, which reduces heating, therefore increases the expected life of the belt.