WO2005021252A1 - Multilayer electrofusion couplings - Google Patents

Multilayer electrofusion couplings Download PDF

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Publication number
WO2005021252A1
WO2005021252A1 PCT/GB2004/003628 GB2004003628W WO2005021252A1 WO 2005021252 A1 WO2005021252 A1 WO 2005021252A1 GB 2004003628 W GB2004003628 W GB 2004003628W WO 2005021252 A1 WO2005021252 A1 WO 2005021252A1
Authority
WO
WIPO (PCT)
Prior art keywords
sleeve
fusible
coupling according
fusible sleeve
electrofusion coupling
Prior art date
Application number
PCT/GB2004/003628
Other languages
French (fr)
Inventor
Paul Clive Roberts-Moore
Michael Bull
David John Hill
Keith Andrew Wilson
Original Assignee
Glynwed Pipe Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Glynwed Pipe Systems Ltd filed Critical Glynwed Pipe Systems Ltd
Priority to JP2006524415A priority Critical patent/JP2007504017A/en
Priority to EP04768184A priority patent/EP1660311A1/en
Publication of WO2005021252A1 publication Critical patent/WO2005021252A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D23/00—Producing tubular articles
    • B29D23/001—Pipes; Pipe joints
    • B29D23/003—Pipe joints, e.g. straight joints
    • B29D23/005—Pipe joints, e.g. straight joints provided with electrical wiring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3404—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the type of heated elements which remain in the joint
    • B29C65/342—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the type of heated elements which remain in the joint comprising at least a single wire, e.g. in the form of a winding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3472—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint
    • B29C65/3476—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint being metallic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/01—General aspects dealing with the joint area or with the area to be joined
    • B29C66/05—Particular design of joint configurations
    • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
    • B29C66/112—Single lapped joints
    • B29C66/1122—Single lap to lap joints, i.e. overlap joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
    • B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
    • B29C66/52—Joining tubular articles, bars or profiled elements
    • B29C66/522—Joining tubular articles
    • B29C66/5221—Joining tubular articles for forming coaxial connections, i.e. the tubular articles to be joined forming a zero angle relative to each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
    • B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
    • B29C66/52—Joining tubular articles, bars or profiled elements
    • B29C66/522—Joining tubular articles
    • B29C66/5229—Joining tubular articles involving the use of a socket
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
    • B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
    • B29C66/7234—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered comprising a barrier layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L47/00—Connecting arrangements or other fittings specially adapted to be made of plastics or to be used with pipes made of plastics
    • F16L47/02—Welded joints; Adhesive joints
    • F16L47/03—Welded joints with an electrical resistance incorporated in the joint
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3468—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special electrical connectors of windings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/71—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/739—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/7392—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic
    • B29C66/73921—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic characterised by the materials of both parts being thermoplastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2310/00—Treatment by energy or chemical effects
    • B32B2310/14—Corona, ionisation, electrical discharge, plasma treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B38/00—Ancillary operations in connection with laminating processes
    • B32B38/0008—Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation

Definitions

  • the present invention relates to electrofusion couplings and their manufacture.
  • multilayer electrofusion couplings for use in environments where organic solvents are present, for example in service station forecourts.
  • Electrofusion is widely used to connect electrofusion couplings to plastics pipes and involves the electrical heating of a thermoplastics polymer in an electrofusion coupling thereby melting the thermoplastics polymer which fuses with and forms a seal between a plastics pipe, inserted into one end of the electrofusion coupling, and the electrofusion coupling.
  • an electrofusion coupling includes any coupling or adapter wherein at least one end is configured to receive an end of a pipe and can include, but Is not strictly limited to, straight couplings, elbows or bends (to facilitate changes in direction of a pipe system), adapters, flange adapters, T-fittings or Y-fittings (adapted to connect three pipe ends), saddle fittings (adapted to connect a smaller, branch pipe to a larger plastics pipe at the region of an aperture formed in the larger pipe), reducers and metal to plastic transition fittings.
  • Pipe systems comprising polyethylene are often used to transport fluids. Some fluids, for example liquid organic solvents, in time permeate through the walls of the pipe systems. If the pipe system is buried in the ground, this can lead to contamination of the surrounding ground. Alternatively if the pipe system is buried in contaminated ground, the contaminants may permeate through the walls of the pipe system and contaminate the fluid being transported through the pipe system.
  • fluids for example liquid organic solvents
  • permeability of a plastics is reduced by increasing its degree of crystallinity leading to closer packing of molecular chains.
  • the permeability is also reduced by modifying the chemical characteristics of plastics by, for example, the inclusion of polar groups leading to closer and stronger interactions between adjacent molecular chains leading to improved permeation resistance to non-polar fluids such as paraffins, cyclo-paraffins, benzene, toluene and xylene.
  • an electrofusion coupling comprising an inner polyethylene layer and an outer polyamide layer wherein the two layers are bonded together through the use of a tie layer comprising a plastics material which has an affinity for polyethylene and polyamide.
  • GB 2 319 496 discloses an electrofusion coupling which incorporates a barrier layer, either comprising a blend between two plastics, one of which has better permeation performance, or comprising a discrete and separate layer.
  • Barrier layers comprising a blend show some adhesion to adjacent layers of the coupling.
  • impermeability is limited by the discontinuous nature of the less permeable plastics in the barrier.
  • Barrier layers comprising a discrete and separate layer show improved impermeability relative to barrier layers comprising a blend because of the continuous nature of the barrier. Such barrier layers show poor adhesion to adjacent layers in the coupling because of lack of chemical affinity.
  • tie layers are introduced to join the barrier layer to other layers in the coupling.
  • one problem with the introduction of tie layers is the greatly increased complexity of the manufacturing process and therefore increased unit costs.
  • a multi-layer electrofusion coupling comprising an inner layer of thermoplastics polymer over which is moulded a barrier layer encapsulated by a further layer of plastics.
  • Tie layers can be optionally included either side of the barrier layer to improve adhesion to adjacent layers and thereby improve the mechanical integrity of the coupling.
  • Such couplings may be formed from an extruded multilayer pipe, in which case the couplings are limited to simple shapes such as straight couplers.
  • tie layer whilst being effective, makes very significant demands on the moulding process.
  • Means need to be provided for incorporating the tie layer into the structure by moulding or other means. Whilst moulding a tie layer construction may be practical for simple shapes, it is difficult and expensive to incorporate the tie layer in more complex shapes such as tees and elbows.
  • the present method seeks to overcome some of the deficiencies mentioned above by eliminating the need for tie layers adjacent to the barrier layer.
  • the present invention provides a method of manufacturing an electrofusion coupling comprising the steps of: a) providing a fusible sleeve comprising an electrically conductive coil or layer and one or more thermoplastics, the electrically conductive coil or layer disposed at or on the surface of the fusible sleeve bore; and b) providing a barrier layer over at least a portion of the exterior surface of the fusible sleeve, the barrier layer comprising one or more plastics with improved resistance to organic solvents compared to the thermoplastics; wherein the method additionally comprises a step of chemical pre- treatment of the exterior surface of the fusible sleeve thereby improving the adhesion of the barrier layer to the said exterior surface.
  • the chemical pre-treatment step modifies the surface chemistry of the fusible layer more compatible with the surface chemistry of the barrier layer to which bonding is desired. A coupling is thereby produced with acceptable mechanical integrity, through enhanced adhesion between the barrier and fusible layers, and a complete external barrier layer.
  • the present method reduces the required number of layers from 3-5 to two layers thereby greatly simplifying the manufacturing process leading to lower unit costs.
  • the present method permits more complex coupling shapes such as T-fittings, reducers or elbows to be produced whereas previously this was not always possible.
  • the complex shaped couplings can now be produced with the same ease and at the same low cost as simple couplings.
  • the method may additionally comprise the step of providing a preform fusible sleeve around which the fusible sleeve is provided, the preform fusible sleeve comprising one or more thermoplastics.
  • the compositions of the fusible sleeve and the preform fusible sleeve are identical or not identical.
  • the fusible sleeve may be provided by cutting a slot ' in the surface of the fusible sleeve bore and pressing the electrically conductive coil into the slot.
  • the method may include an additional step of providing a tie layer over the fusible sleeve before the step of chemical pre-treatment of the exterior surface of the fusible sleeve and step ⁇ b', the tie layer comprising one or more tie plastics with chemical affinity for both the exterior surface of the fusible sleeve and the barrier layer.
  • any one of the fusible sleeve, the preform fusible sleeve, the tie layer or the barrier layer may be manufactured by any one of spraying, injection moulding or by application of a pre-formed film.
  • the thermoplastics may be a melt processable homopolymer or copolymer such as polyethylene, functionalised polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl chloride, acrylonitrile - butadiene - styrene (ABS) terpolymer, poly(ethylene - vinyl alcohol), poly(ethylene - vinyl acetate), poly(ethylene - acrylic acid), poly(ethylene - ethyl acrylate), or a homopolymer or copolymer of ethylene, propylene, vinylidene fluoride, vinyl chloride, vinyl alcohol, ethyl acrylate or acrylic acid.
  • ABS acrylonitrile - butadiene - styrene
  • the plastics may be a crystalline polar thermoplastics such as a polyamide, poly(vinylidene fluoride), poly(vinylidene chloride), a polyurea, a polyurethane, a polyacrylonitrile, a polymethacrylonitrile, poly(vinyl alcohol), or a homopolymer or copolymer of an amide, vinylidene fluoride, vinylidene chloride, a urea, a urethane, acrylonitrile, methacrylonitrile or vinyl alcohol.
  • a crystalline polar thermoplastics such as a polyamide, poly(vinylidene fluoride), poly(vinylidene chloride), a polyurea, a polyurethane, a polyacrylonitrile, a polymethacrylonitrile, poly(vinyl alcohol), or a homopolymer or copolymer of an amide, vinylidene fluoride, vinylidene chloride, a ure
  • the tie plastics may be selected from maleic anhydride grafted polyethylene, acrylate grafted polyethylenes, poly(ethylene - vinyl acetate), poly(ethylene - vinyl alcohol), or a homopolymer or copolymer of ethylene, vinyl acetate, vinyl alcohol, ethyl ' acrylate or maleic anhydride.
  • Maleic anhydride provides reactive sites that promote adhesion with the barrier layer and polyethylene provides compatibility with the fusible sleeve.
  • the chemical pre-treatment may comprise at least one of treatment with an acid such as chromic acid, treatment by corona discharge, treatment by fluorination, flame treatment, treatment by ozone, atmospheric plasma treatment or low pressure plasma treatment with desirably at least one of oxygen, nitrogen, hydrogen or argon.
  • an acid such as chromic acid
  • corona discharge treatment by corona discharge
  • fluorination treatment by fluorination
  • flame treatment treatment by ozone
  • atmospheric plasma treatment or low pressure plasma treatment with desirably at least one of oxygen, nitrogen, hydrogen or argon.
  • Chemical pre-treatment increases the concentration of polar groups on the exterior surface of the fusible sleeve by oxidation or fluorination and thereby improves the chemical compatibility of the fusible sleeve for the barrier layer.
  • Another aspect of the present invention is the provision of an electrofusion coupling manufactured according to the preceding method.
  • the ratio of the thickness of the fusible layer to the outside diameter of the coupling may be in the range 5: 1 to 10:1 and is desirably 7.5: 1.
  • the ratio of the thickness of the preform fusible layer to the outside diameter of the coupling may be in the range 75:1 to 150:1 and is desirably about 100:1.
  • the ratio of the thickness of the tie layer to the outside diameter of the coupling may be in the range 100:1 to 500:1 and is desirably 200: 1.
  • the ratio of the thickness of the barrier layer to the outside diameter of the coupling may be in the range 10:1 to 200:1 and is desirably 50:1.
  • Figure 1 shows a longitudinal cross-section of a first embodiment of electrofusion coupling in accordance with the invention.
  • FIG. 2 which shows a longitudinal cross-section of a second embodiment of electrofusion coupling in accordance with the invention.
  • the electrofusion coupling illustrated in Figure 1 is adapted to receive a first pipe end (113) at a first coupling end (111) and a second pipe end
  • the electrically conductive wire (103) which assumes a helical configuration, comprises a first sleeve (101) received within a second sleeve (102), a third sleeve (115) which receives the second sleeve (102), and an electrical resistance wire (103) positioned between an exterior surface of the first sleeve (104) and an interior surface of the second sleeve (105).
  • the electrically conductive wire (103) which assumes a helical configuration, comprises a first
  • the inside diameter of the coupling is 63 mm.
  • the wall thicknesses of the first (101), second (102) and third sleeves (115) are respectively 1 mm, 6 mm and 1.5 mm.
  • the first and second sleeves (101, 102) comprise a polyethylene of molecular weight range 100 000 to 200 000.
  • the third sleeve (115) comprises Nylon (RTM).
  • the first (101), second (102) and third (115) sleeves additionally include pigments, fillers and processing additives.
  • the electrical resistance wire (103) comprises an alloy of copper and nickel, or copper and tin.
  • the electrofusion pipe coupling illustrated in Figure 2 is adapted to receive a first pipe end (213) at a first coupling end (211) and a second pipe end (214) at a second coupling end (212) and comprises a first sleeve (201) received within a second sleeve (202), and an electrical resistance wire (203) positioned at an interior surface of the first sleeve (204).
  • the electrically conductive wire (203) which assumes a helical configuration, comprises a first (206) and second (207) end, each end terminating at a first (208) and second (209) terminal respectively and located at an exterior surface of the second sleeve (210).
  • the inside diameter of the coupling is 63 mm.
  • the wall thicknesses of the first (201) and second (202) sleeves are respectively 7 mm and 1.5 mm.
  • the first sleeve (201) comprise a polyethylene of molecular weight range 100 000 to 200 000.
  • the second sleeve (202) comprises Nylon (RTM).
  • the first (201) and second (202) sleeves additionally include pigments, fillers and processing additives.
  • the electrical resistance wire (203) comprises an alloy of copper and nickel, or copper and tin.
  • a variant of the electrofusion couplings illustrated in Figures 1 and 2 includes a tie layer between the polyethylene sleeve and the Nylon (RTM) sleeve.
  • the tie layer comprises maleic anhydride grafted polyethylene which is available under the trade name Orevac.
  • the electrofusion coupling of the form illustrated in Figure 1 was manufactured by injection moulding the first polyethylene sleeve over a cylindrical mould core thereby forming a pre-form.
  • the cylindrical mould core was then removed from the pre-form and the electrical resistance wire wound in helical fashion around the pre-form to form a wound preform.
  • the second polyethylene sleeve was then injection moulded over the wound pre-form.
  • the radially exterior surface of the second polyethylene sleeve then underwent low pressure plasma treatment by exposing the said surface to an ionised gas mixture comprising nitrogen and hydrogen under a partial vacuum for a period of time necessary to modify the chemical nature of the surface to promote optimum adhesion to the nylon sleeve.
  • the Nylon (RTM) sleeve was then injection moulded over the chemically pre-treated second polyethylene sleeve.
  • the electrofusion coupling of the form illustrated in Figure 2 was manufactured by winding an electrical resistance wire around a cylindrical mould core in helical fashion thereby forming a wound core.
  • the polyethylene sleeve was injection moulded over the wound core.
  • the radially exterior surface of the polyethylene sleeve then underwent low pressure plasma treatment by exposing the said surface to an ionised gas mixture comprising nitrogen and hydrogen under a partial vacuum for a period of time necessary to modify the chemical nature of the surface to promote optimum adhesion to the nylon sleeve.
  • the Nylon (RTM) sleeve was then injection moulded over the treated sleeve of polyethylene.
  • the electrofusion coupling of the form illustrated in Figure 2 was also manufactured by injection moulding the polyethylene sleeve over a cylindrical mould. Treating the radially exterior surface of the polyethylene sleeve to low pressure plasma treatment by exposing the said surface to an ionised gas mixture comprising nitrogen and hydrogen under a partial vacuum for a period of time necessary to modify the chemical nature of the surface to promote optimum adhesion to the nylon sleeve.
  • the Nylon (RTM) sleeve was then injection moulded over the treated polyethylene sleeve.
  • the cylindrical mould core was then removed from the polyethylene sleeve.
  • the electrical resistance wire was then inserted into the polyethylene sleeve by cutting a slot into the radially inner surface thereof and pressing the electrical resistance wire into the slot.
  • the variant electrofusion couplings including a tie layer were manufactured in the same manner as described hereinabove but additionally including a step of injection moulding the tie layer over the chemically treated polyethylene sleeve prior to injection moulding the Nylon (RTM) sleeve.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Branch Pipes, Bends, And The Like (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)

Abstract

A method of manufacturing an electrofusion coupling comprising the steps of: a. providing a fusible sleeve (101, 102) comprising an electrically conductive coil (103) or layer and one or more thermoplastics, the electrically conductive coil or layer disposed at or on the surface of the fusible sleeve bore; and b. providing a barrier layer (115) over at least a portion of the exterior surface of the fusible sleeve, the barrier layer comprising one or more plastics with improved resistance to organic solvents compared to, the thermoplastics; wherein the method additionally comprises a step of chemical pretreatment of the exterior surface of the fusible sleeve thereby improving the adhesion of the barrier layer (115) to the said exterior surface.

Description

MULTILAYER ELECTROFUSION COUPLINGS
The present invention relates to electrofusion couplings and their manufacture. In particular to multilayer electrofusion couplings for use in environments where organic solvents are present, for example in service station forecourts.
Electrofusion is widely used to connect electrofusion couplings to plastics pipes and involves the electrical heating of a thermoplastics polymer in an electrofusion coupling thereby melting the thermoplastics polymer which fuses with and forms a seal between a plastics pipe, inserted into one end of the electrofusion coupling, and the electrofusion coupling. For the purposes of the present description, an electrofusion coupling includes any coupling or adapter wherein at least one end is configured to receive an end of a pipe and can include, but Is not strictly limited to, straight couplings, elbows or bends (to facilitate changes in direction of a pipe system), adapters, flange adapters, T-fittings or Y-fittings (adapted to connect three pipe ends), saddle fittings (adapted to connect a smaller, branch pipe to a larger plastics pipe at the region of an aperture formed in the larger pipe), reducers and metal to plastic transition fittings.
Pipe systems comprising polyethylene are often used to transport fluids. Some fluids, for example liquid organic solvents, in time permeate through the walls of the pipe systems. If the pipe system is buried in the ground, this can lead to contamination of the surrounding ground. Alternatively if the pipe system is buried in contaminated ground, the contaminants may permeate through the walls of the pipe system and contaminate the fluid being transported through the pipe system.
It is known that high density materials have low permeability. Thus the permeability of a plastics is reduced by increasing its degree of crystallinity leading to closer packing of molecular chains. The permeability is also reduced by modifying the chemical characteristics of plastics by, for example, the inclusion of polar groups leading to closer and stronger interactions between adjacent molecular chains leading to improved permeation resistance to non-polar fluids such as paraffins, cyclo-paraffins, benzene, toluene and xylene.
It has been observed that organic solvents such as petroleum based fluids permeate through the walls of pipe systems comprising polyethylene. The permeability of such solvents through plastics such as polyamide, which have high degrees of crystallinity and polar chemical groups, is significantly lower than that through polyethylene. Thus pipes for conveying petroleum based fluids and other organic solvents are formed with an inner layer of polyamide and an outer layer of polyethylene.
In GB 2 351 257 A, an electrofusion coupling is disclosed comprising an inner polyethylene layer and an outer polyamide layer wherein the two layers are bonded together through the use of a tie layer comprising a plastics material which has an affinity for polyethylene and polyamide.
GB 2 319 496 discloses an electrofusion coupling which incorporates a barrier layer, either comprising a blend between two plastics, one of which has better permeation performance, or comprising a discrete and separate layer.
Barrier layers comprising a blend show some adhesion to adjacent layers of the coupling. However one problem with such a barrier layer is that impermeability is limited by the discontinuous nature of the less permeable plastics in the barrier.
Barrier layers comprising a discrete and separate layer show improved impermeability relative to barrier layers comprising a blend because of the continuous nature of the barrier. Such barrier layers show poor adhesion to adjacent layers in the coupling because of lack of chemical affinity. In order to improve the mechanical integrity of the coupling, tie layers are introduced to join the barrier layer to other layers in the coupling. However one problem with the introduction of tie layers is the greatly increased complexity of the manufacturing process and therefore increased unit costs.
In GB 2 351 257 a multi-layer electrofusion coupling is disclosed comprising an inner layer of thermoplastics polymer over which is moulded a barrier layer encapsulated by a further layer of plastics. Tie layers can be optionally included either side of the barrier layer to improve adhesion to adjacent layers and thereby improve the mechanical integrity of the coupling. Such couplings may be formed from an extruded multilayer pipe, in which case the couplings are limited to simple shapes such as straight couplers.
The provision of a tie layer, whilst being effective, makes very significant demands on the moulding process. Means need to be provided for incorporating the tie layer into the structure by moulding or other means. Whilst moulding a tie layer construction may be practical for simple shapes, it is difficult and expensive to incorporate the tie layer in more complex shapes such as tees and elbows.
The present method seeks to overcome some of the deficiencies mentioned above by eliminating the need for tie layers adjacent to the barrier layer.
Summary of the Invention
In a first aspect, the present invention provides a method of manufacturing an electrofusion coupling comprising the steps of: a) providing a fusible sleeve comprising an electrically conductive coil or layer and one or more thermoplastics, the electrically conductive coil or layer disposed at or on the surface of the fusible sleeve bore; and b) providing a barrier layer over at least a portion of the exterior surface of the fusible sleeve, the barrier layer comprising one or more plastics with improved resistance to organic solvents compared to the thermoplastics; wherein the method additionally comprises a step of chemical pre- treatment of the exterior surface of the fusible sleeve thereby improving the adhesion of the barrier layer to the said exterior surface.
The chemical pre-treatment step modifies the surface chemistry of the fusible layer more compatible with the surface chemistry of the barrier layer to which bonding is desired. A coupling is thereby produced with acceptable mechanical integrity, through enhanced adhesion between the barrier and fusible layers, and a complete external barrier layer.
Furthermore the present method reduces the required number of layers from 3-5 to two layers thereby greatly simplifying the manufacturing process leading to lower unit costs.
In addition, the present method permits more complex coupling shapes such as T-fittings, reducers or elbows to be produced whereas previously this was not always possible. The complex shaped couplings can now be produced with the same ease and at the same low cost as simple couplings.
The method may additionally comprise the step of providing a preform fusible sleeve around which the fusible sleeve is provided, the preform fusible sleeve comprising one or more thermoplastics. The compositions of the fusible sleeve and the preform fusible sleeve are identical or not identical. The fusible sleeve may be provided by cutting a slot'in the surface of the fusible sleeve bore and pressing the electrically conductive coil into the slot.
The method may include an additional step of providing a tie layer over the fusible sleeve before the step of chemical pre-treatment of the exterior surface of the fusible sleeve and step λb', the tie layer comprising one or more tie plastics with chemical affinity for both the exterior surface of the fusible sleeve and the barrier layer.
Any one of the fusible sleeve, the preform fusible sleeve, the tie layer or the barrier layer may be manufactured by any one of spraying, injection moulding or by application of a pre-formed film.
The thermoplastics may be a melt processable homopolymer or copolymer such as polyethylene, functionalised polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl chloride, acrylonitrile - butadiene - styrene (ABS) terpolymer, poly(ethylene - vinyl alcohol), poly(ethylene - vinyl acetate), poly(ethylene - acrylic acid), poly(ethylene - ethyl acrylate), or a homopolymer or copolymer of ethylene, propylene, vinylidene fluoride, vinyl chloride, vinyl alcohol, ethyl acrylate or acrylic acid.
The plastics may be a crystalline polar thermoplastics such as a polyamide, poly(vinylidene fluoride), poly(vinylidene chloride), a polyurea, a polyurethane, a polyacrylonitrile, a polymethacrylonitrile, poly(vinyl alcohol), or a homopolymer or copolymer of an amide, vinylidene fluoride, vinylidene chloride, a urea, a urethane, acrylonitrile, methacrylonitrile or vinyl alcohol.
The tie plastics may be selected from maleic anhydride grafted polyethylene, acrylate grafted polyethylenes, poly(ethylene - vinyl acetate), poly(ethylene - vinyl alcohol), or a homopolymer or copolymer of ethylene, vinyl acetate, vinyl alcohol, ethyl ' acrylate or maleic anhydride.
Maleic anhydride provides reactive sites that promote adhesion with the barrier layer and polyethylene provides compatibility with the fusible sleeve.
The chemical pre-treatment may comprise at least one of treatment with an acid such as chromic acid, treatment by corona discharge, treatment by fluorination, flame treatment, treatment by ozone, atmospheric plasma treatment or low pressure plasma treatment with desirably at least one of oxygen, nitrogen, hydrogen or argon.
Chemical pre-treatment increases the concentration of polar groups on the exterior surface of the fusible sleeve by oxidation or fluorination and thereby improves the chemical compatibility of the fusible sleeve for the barrier layer.
Another aspect of the present invention is the provision of an electrofusion coupling manufactured according to the preceding method.
The ratio of the thickness of the fusible layer to the outside diameter of the coupling may be in the range 5: 1 to 10:1 and is desirably 7.5: 1. The ratio of the thickness of the preform fusible layer to the outside diameter of the coupling may be in the range 75:1 to 150:1 and is desirably about 100:1. The ratio of the thickness of the tie layer to the outside diameter of the coupling may be in the range 100:1 to 500:1 and is desirably 200: 1. The ratio of the thickness of the barrier layer to the outside diameter of the coupling may be in the range 10:1 to 200:1 and is desirably 50:1.
Brief Description of the Figures
The invention will now be described in detail with reference to: Figure 1 which shows a longitudinal cross-section of a first embodiment of electrofusion coupling in accordance with the invention; and
Figure 2 which shows a longitudinal cross-section of a second embodiment of electrofusion coupling in accordance with the invention.
Detailed Description of the Invention
The electrofusion coupling illustrated in Figure 1 is adapted to receive a first pipe end (113) at a first coupling end (111) and a second pipe end
(114) at a second coupling end (112) and comprises a first sleeve (101) received within a second sleeve (102), a third sleeve (115) which receives the second sleeve (102), and an electrical resistance wire (103) positioned between an exterior surface of the first sleeve (104) and an interior surface of the second sleeve (105). The electrically conductive wire (103), which assumes a helical configuration, comprises a first
(106) and second (107) end, each end terminating at a first (108) and second (109) terminal respectively and located at an exterior surface of the third sleeve (115).
The inside diameter of the coupling is 63 mm. The wall thicknesses of the first (101), second (102) and third sleeves (115) are respectively 1 mm, 6 mm and 1.5 mm.
The first and second sleeves (101, 102) comprise a polyethylene of molecular weight range 100 000 to 200 000. The third sleeve (115) comprises Nylon (RTM). The first (101), second (102) and third (115) sleeves additionally include pigments, fillers and processing additives. The electrical resistance wire (103) comprises an alloy of copper and nickel, or copper and tin.
The electrofusion pipe coupling illustrated in Figure 2 is adapted to receive a first pipe end (213) at a first coupling end (211) and a second pipe end (214) at a second coupling end (212) and comprises a first sleeve (201) received within a second sleeve (202), and an electrical resistance wire (203) positioned at an interior surface of the first sleeve (204). The electrically conductive wire (203), which assumes a helical configuration, comprises a first (206) and second (207) end, each end terminating at a first (208) and second (209) terminal respectively and located at an exterior surface of the second sleeve (210).
The inside diameter of the coupling is 63 mm. The wall thicknesses of the first (201) and second (202) sleeves are respectively 7 mm and 1.5 mm.
The first sleeve (201) comprise a polyethylene of molecular weight range 100 000 to 200 000. The second sleeve (202) comprises Nylon (RTM). The first (201) and second (202) sleeves additionally include pigments, fillers and processing additives. The electrical resistance wire (203) comprises an alloy of copper and nickel, or copper and tin.
A variant of the electrofusion couplings illustrated in Figures 1 and 2 includes a tie layer between the polyethylene sleeve and the Nylon (RTM) sleeve. The tie layer comprises maleic anhydride grafted polyethylene which is available under the trade name Orevac.
The electrofusion coupling of the form illustrated in Figure 1 was manufactured by injection moulding the first polyethylene sleeve over a cylindrical mould core thereby forming a pre-form. The cylindrical mould core was then removed from the pre-form and the electrical resistance wire wound in helical fashion around the pre-form to form a wound preform. The second polyethylene sleeve was then injection moulded over the wound pre-form.
The radially exterior surface of the second polyethylene sleeve then underwent low pressure plasma treatment by exposing the said surface to an ionised gas mixture comprising nitrogen and hydrogen under a partial vacuum for a period of time necessary to modify the chemical nature of the surface to promote optimum adhesion to the nylon sleeve. The Nylon (RTM) sleeve was then injection moulded over the chemically pre-treated second polyethylene sleeve.
The electrofusion coupling of the form illustrated in Figure 2 was manufactured by winding an electrical resistance wire around a cylindrical mould core in helical fashion thereby forming a wound core. The polyethylene sleeve was injection moulded over the wound core.
The radially exterior surface of the polyethylene sleeve then underwent low pressure plasma treatment by exposing the said surface to an ionised gas mixture comprising nitrogen and hydrogen under a partial vacuum for a period of time necessary to modify the chemical nature of the surface to promote optimum adhesion to the nylon sleeve. The Nylon (RTM) sleeve was then injection moulded over the treated sleeve of polyethylene.
The electrofusion coupling of the form illustrated in Figure 2 was also manufactured by injection moulding the polyethylene sleeve over a cylindrical mould. Treating the radially exterior surface of the polyethylene sleeve to low pressure plasma treatment by exposing the said surface to an ionised gas mixture comprising nitrogen and hydrogen under a partial vacuum for a period of time necessary to modify the chemical nature of the surface to promote optimum adhesion to the nylon sleeve. The Nylon (RTM) sleeve was then injection moulded over the treated polyethylene sleeve. The cylindrical mould core was then removed from the polyethylene sleeve. The electrical resistance wire was then inserted into the polyethylene sleeve by cutting a slot into the radially inner surface thereof and pressing the electrical resistance wire into the slot. The variant electrofusion couplings including a tie layer were manufactured in the same manner as described hereinabove but additionally including a step of injection moulding the tie layer over the chemically treated polyethylene sleeve prior to injection moulding the Nylon (RTM) sleeve.

Claims

Claims
1. A method of manufacturing an electrofusion coupling comprising the steps of: a. providing a fusible sleeve comprising an electrically conductive coil or layer and one or more thermoplastics, the electrically conductive coil or layer disposed at or on the surface of the fusible sleeve bore; and b. providing a barrier layer over at least a portion of the exterior surface of the fusible sleeve, the barrier layer comprising one or more plastics with improved resistance to organic solvents compared to the thermoplastics; wherein the method additionally comprises a step of chemical pre- treatment of the exterior surface of the fusible sleeve thereby improving the adhesion of the barrier layer to the said exterior surface.
2. A method of manufacturing an electrofusion coupling according to claim 1 wherein the method additionally comprises the step of providing a preform fusible sleeve around which the fusible sleeve is provided, the preform fusible sleeve comprising one or more thermoplastics.
3. A method of manufacturing an electrofusion coupling according to claim 2 wherein the compositions of the fusible sleeve and the preform fusible sleeve are identical or not identical.
4. A method of manufacturing an electrofusion coupling according to claim 1 wherein the fusible sleeve is provided by cutting a slot in the surface of the fusible sleeve bore and pressing the electrically conductive coil into the slot.
5. A method of manufacturing an electrofusion coupling according to any one of the preceding claims including an additional step of providing a tie layer over the fusible sleeve' before the step of chemical pre-treatment of the exterior surface of the fusible sleeve and step λb', the tie layer comprising one or more tie plastics with chemical affinity for both the exterior surface of the fusible sleeve and the barrier layer.
6. A method of manufacturing an electrofusion coupling according to any one of the preceding claims wherein any one of the fusible sleeve, the preform fusible sleeve, the tie layer or the barrier layer is manufactured by any one of spraying, injection moulding or by application of a pre-formed film.
7. A method of manufacturing an electrofusion coupling according to any one of the preceding claims wherein the thermoplastics is a melt processable homopolymer or copolymer such as polyethylene, functionalised polyethylene, polypropylene, polyvinylidene fluoride, polyvinyl chloride, acrylonitrile - butadiene - styrene (ABS) terpolymer, poly(ethylene - vinyl alcohol), poly(ethylene - vinyl acetate), poly(ethylene - acrylic acid), poly(ethylene - ethyl acrylate), or a homopolymer or copolymer of ethylene, propylene, vinylidene fluoride, vinyl chloride, vinyl alcohol, ethyl acrylate or acrylic acid.
8. A method of manufacturing an electrofusion coupling according to any one of the preceding claims wherein the plastics is a crystalline polar thermoplastics such as a polyamide, poly(vinylidene fluoride), poly(vinylidene chloride), a polyurea, a polyurethane, a polyacrylonitrile, a polymethacrylonitrile, poly(vinyl alcohol), or a homopolymer or copolymer of an amide, vinylidene fluoride, vinylidene chloride, a urea, a urethane, acrylonitrile, methacrylonitrile or vinyl alcohol.
9. A method of manufacturing an electrofusion coupling according to any one of claims 5-8 wherein the tie plastics is selected from maleic anhydride grafted polyethylene, acrylate grafted polyethylenes, poly(ethylene - vinyl acetate), poly(ethylene - vinyl alcohol), or a homopolymer or copolymer of ethylene, vinyl acetate, vinyl alcohol, ethyl acrylate or maleic anhydride.
10. A method of manufacturing an electrofusion coupling according to any one of the preceding claims wherein the chemical pre- treatment comprises at least one of treatment with an acid such as chromic acid, treatment by corona discharge, treatment by fluorination, flame treatment, treatment by ozone, atmospheric plasma treatment or low pressure plasma treatment with desirably at least one of oxygen, nitrogen, hydrogen or argon.
11. An electrofusion coupling manufactured in accordance with any one of the preceding claims.
12. An electrofusion coupling according to claim 11 wherein the ratio of the thickness of the fusible layer to the outside diameter of the coupling is in the range 5:1 to 10:1 and is desirably 7.5:1.
13. An electrofusion coupling according to claim 11 or claim 12 wherein the ratio of the thickness of the preform fusible layer to the outside diameter of the coupling is in the range 75:1 to 150:1 and is desirably 100: 1.
14. An electrofusion coupling according to any one of claims 11-13 wherein the ratio of the thickness of the tie layer to the outside diameter of the coupling is in the range 100:1 to 500:1 and is desirably 200:1.
5. An electrofusion coupling according to any one of claims 11-14 wherein the ratio of the thickness of the barrier layer to the outside diameter of the coupling is in the range 10: 1 to 200: 1 and is desirably 50:1.
PCT/GB2004/003628 2003-08-29 2004-08-25 Multilayer electrofusion couplings WO2005021252A1 (en)

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JP2007504017A (en) 2007-03-01
GB2405375B (en) 2006-01-11
GB0320289D0 (en) 2003-10-01
GB2405375A (en) 2005-03-02

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