GB2377406A

GB2377406A - Water storage and distribution apparatus

Info

Publication number: GB2377406A
Application number: GB0210500A
Authority: GB
Inventors: Alan Pow
Original assignee: BONDED BARRIERS Ltd
Current assignee: BONDED BARRIERS Ltd
Priority date: 2001-05-08
Filing date: 2002-05-08
Publication date: 2003-01-15
Also published as: GB0210500D0; GB0111211D0

Abstract

An apparatus is disclosed for use in water storage and water distribution systems. The apparatus comprises a main supporting structure in the form of a moulded body of a fibre reinforced thermoset plastic and a barrier layer on at least one surface of the structure. The barrier layer consists substantially of a thermoplastic material selected from the group of combinations consisting of (a) high density polyethylene and low density polyethylene, (b) polypropylene and linear low density polypropylene, (c) polypropylene and polypropylene copolymer, (d) nylon (RTM) and polypropylene copolymer and (e) Nylon (RTM) and low density polypropylene. The barrier layer prevents water contact with the thermoset plastic and is preferably chemically inert with respect to the type of chemicals normally found in water. Methods of manufacturing the apparatus are also disclosed, including heating and compressing the fibre-reinforced thermoset plastic material and barrier layer in a mould, and coating the barrier layer with a bonding agent before heating it and bringing it into contact with the fibre-reinforced thermoset plastic materal. The apparatus may be modular or a complete structure.

Description

WATER STORAGE AND DISTRIBUTION APPARATUS The present invention relates to water storage and distribution apparatus and to method of manufacturing the same. The present invention is particularly, but not exclusively, concerned with apparatus such as storage tanks and cisterns.

Water quality is dependent on many factors and the storage contact material is recognised as one of the most important. An extensive selection of materials has been employed in the manufacture of storage tanks and pipes ranging from iron and alloys to non-metallic materials.

Fitness of purpose of materials used in water storage and distribution apparatus and their effects on water is evaluated and tested in the United Kingdom by the Water Research Centre (WRC). Testing is currently carried out in the United Kingdom in accordance with the requirements of BS6920. Other nations have similar voluntary or statutory requirements, which are similarly supported by their own testing and evaluation facilities.

Generally, these tests are based on evaluating the material's inertness and will include the following tests: a) No taste imparted to water b) No change in the appearance of water c) No growth of micro-organisms in water in contact with the materials or on the surface of the material d) No release of substances into the water that may be of concern to public health.

Water authorities and also under ever increasing pressure to further improve water quality from resources that may contain quantities of industrial by-products including organochlorines. Organochlorines are substances containing chemically combined chlorine and carbon. Most are toxic, persistent and tend to bioaccumulate in the environment. Around

1000 organochlorines have been identified most of which are produced 1d released by industry it is therefore of increasing importance that water orage and distribution apparatus is rendered inert to the presence of such dustrial by-products.

In recent years materials derived from the plastics industry have een advocated and adopted in water treatment and distribution facilities. wo groups of plastics, in particular, have been used in the construction of quipment such as water storage tanks and piping: thermoplastic and lermoset materials.

Reference herein to thermoplastic material is intended to compass but not be restricted to Coex Nylon (including codes BNE, NG, NDS and NL), Coex & Monolayer Surlyn (including codes C, ESE, E, C and PFP), Coex Polypropylene (including codes EPN, PED, PEP and ) and htegraformTM (including codes VX40/70, VN50/75, EPN 150, NL 40, PO 150 and HDPE/S) all of Rexam Medical Packaging Materials. hermoset moulding compounds and thermoset resins are used in the manufacture of fibre reinforced polyester (FRP) that is also commonly referred to as glass reinforced polyester (GRP), sheet moulding impounds (SMC) or low pressure moulding components (LPMC). eference herein to fibre reinforced thermoset plastics material is intended 3 reference to this family of materials and specifically, but not exclusively intended to encompass LPMC formulations of Scot Bader Company pic, PMC formulations based on Crystic ImpregTM crystalline unsaturated oIyester resins and formulations of Gloucester Composites Ltd including rmulations based on GR103.

However, both of these materials have their drawbacks. In the case r thermoset plastics, the material is subject to a cross-linking process via a italyst initiator. The moulding conditions are therefore extremely iportant to ensure a good cure of the material which is vital to the

inertness of the finished product with respect to water contact. Undercured thermoset plastics are vulnerable to chemical attack and may provide suitable conditions to promote microbial growth and to the development of leachates within the storage tank environment. Unfortunately, as a result of the commercial pressures placed on manufacturers of water storage and distribution apparatus, there is a concern that the curing conditions adopted for thermoset plastics are not always optimised which can have a very concerning and very direct effect on water quality. This can be of particular concern in countries where the apparatus will be exposed to extremes of temperature. Thermoplastic materials, however, are not sufficiently strong to be suitable for use in anything other than smaller components of a water distribution system. In particular, thermoplastics materials are not suitable in the construction of large storage tanks.

The present invention seeks to provide improved water storage and distribution apparatus that overcomes the disadvantages described above with existing materials used in the manufacture of water storage and distribution apparatus.

The present invention provides apparatus for use in water storage or water distribution systems, the apparatus comprising a main supporting structure being a moulded body of a fibre reinforced thermoset plastics material and a barrier layer on at least one surface of the main supporting structure, the barrier layer substantially consisting of a thermoplastics material selected from the group of combinations consisting of: (i) high density polyethylene and low density polyethylene, (ii) polypropylene and linear low density polypropylene, (iii) polypropylene and polypropylene copolymer, (iv) Nylon and polypropylene copolymer and (v) Nylon and low density polypropylene.

With the present invention the thermoplastics material is used to provide a barrier layer to what would otherwise be a water-contacting

rface of the thermoset plastics material. The thermoplastics barrier layer ovides a surface that is substantially chemically inert, with respect to the e of chemicals normally found in water, and that is substantially inert to drolysis. Whilst it is preferred for the thermoset plastics material to be lIy cured, with this invention it is possible for the themoset plastics aterial not to be fully cured without this being detrimental to the suitability the apparatus in water storage and distribution systems.

With the present invention, the properties of thermoset and ermoplastics materials can be blended and bonded to suit the various ter and chemical resistant properties desired by regulatory water thorities. Moreover, within the thermoset/thermoplastic laminate matrix the present invention, the positioning of the two materials can be lected to ensure that the materials are positioned strategically with spect to the needs of a particular water storage/distribution structure. ius, the load bearing properties of the fibre reinforced thermoset plastics aterial is retained and enhanced by providing a thermoplastic water irriter film to the water contact side of the fibre reinforced thermoset astics material. Use of this multi-laminar material for water storage and 3tribution applications provides significant and improved assurance of rtness to water in comparison to existing water systems.

Preferably the apparatus is a modular element adapted to erconnect with further modular elements in the construction of a water ) rage or water distribution system. For example, the modular panels may adapted for construction of a water tank.

Ideally, the thermoset plastics material has glass fibre and/or glass ads as the reinforcing fibre, fillers such as china clays and calcium rbonates, shrink controllers, catalysts, inhibitors and release initiators, juments, lubricants and dyes. The barrier layer may comprise a single 'er of thermoplastic material or multiple or mixed layers. In the case of

multiple or mixed layers of thermoplastics materials, where each layer may be the same or different thermoplastics materials, an adhesive bonding resin may be used to bond individual layers of the stack together. Such multiple or mixed layers of thermoplastics material are generally supplied pre-bonded as a single film sheet, by companies such as Rexam Medical Packaging.

In an alternative aspect the present invention provides a method of manufacturing apparatus for use in water storage or water distribution systems comprising placing in a mould tool fibre reinforced thermoset plastics material and a tensioned sheet of thermoplastics film, heating the materials within the mould and closing the mould tool to compress the materials within the mould tool for a predetermined time period.

Ideally, the tensioning of the sheet of thermoplastics film is adjusted during closure of the mould tool and one or more segments of the sheet of thermoplastics material may be removed to reduce creasing and overlapping of the thermoplastics material during compression.

In a preferred embodiment the mould tool comprises respective male and female moulds capable of movement relative to one another and the closing movement of the mould tool is performed in two stages with the relative movement of the moulds in the second stage being slower than in the first stage.

In an alternative aspect the present invention provides a method of manufacturing apparatus for use in water storage or water distribution systems comprising providing a sheet of thermoplastics film, one surface of which is coated in a bonding agent; positioning the sheet of thermoplastics film over a moulded element of fibre reinforced thermoset plastics material with the coated surface of the thermoplastics film facing the moulded element; heating the sheet of thermoplastics material; and then bringing the

moulded element in contact with the coated surface of the thermoplastics m. The bonding agent may be an adhesive resin such as that manufactured by Rexam Medical PackagingTM.

An embodiment of the present invention will now be described by ay of example with reference to the accompany drawings, in which: Figure 1 is a partially cut-away illustration of a sectional panel . orage tank in accordance with the present invention; Figures 2a and 2b illustrate a domed modular panel in accordance ith the present invention; Figures 3a and 3b illustrate a sump/drain modular panel in qcordance with the present invention; Figures 4a and 4b illustrate profiled modular side panels in Dcordance with the present invention; Figures 5a and 5b illustrate flat modular panels in accordance with te present invention; Figures 6a and 6b illustrate alternative mould orientations in ocordance with the present invention; and Figures 7a and 7b illustrated features of a tensioning frame used in se production moulding tool in accordance with the present invention.

Water storage tanks and cisterns are generally based on either a ne-piece'construction or a'sectional modular panel'construction. As a result of their modular structure, a sectional tank construction has storage capabilities ranging from below 500 litres up to and exceeding 4,500, 000 res nominal capacity. The use of a modular structure provides greater 3xibility in terms of tank dimensions, storage capacity and choice in the method of site location of the tank.

In Figure 1 an example of a sectional water tank 1 is illustrated. ach of the four walls 2 of the tank is constructed using nine separate side anels 5, arranged three square and similarly the top 3 and bottom 4 of the

tank are each constructed using nine separate roof panels 6 and base panels 7 respectively. The panels are bolted together through their flanges and the joins are sealed with a conventional gasket to provide a durable watertight seal or with a sealant such as a butyl or polyurethane material.

Within the tank stainless steel tie rods 9 and/or other conventional bracing structure is used to support the walls and ceiling of the tank, such as the uPVC support columns 10 illustrated. Instead of internal supporting structure, external corsetry usually of steel may be employed. The interior of the tank may additionally be partitioned using modular partitioning panels 8 that are in turn supported by partition panel supports 11.

Other features of the sectional tank construction illustrated, that are conventional features to be found with most large water storage systems include manway access hatches 12, overflow and warning pipes 13, internal access ladder 14, external access ladder 15, screened air vents 16 and float valve chambers 17. The tank also requires a foundation usually, as illustrated, in the form of a grid of steel supports mounted over sleeper supporting walls.

Details of the modular panels are illustrated in Figures 2a, 2b, 3a, 3b, 4a, 4b, 5a and 5b. The domed modular panel illustrated in Figures 3a and 3b is suited for use as a roof or floor panel 6,7. The domed panel consists of a central domed region 18 that has structure reinforcement 19 at regions where the dome is most sharply curved and a rim 20 in the form of a flanged edge that extends away from the interior of the dome. The domed panel may be installed in two opposing orientations: with the domed region presenting a convex surface to water within the tank or with the domed region presenting a concave surface to the water within the tank.

The profile of the domed panel is such that it is self-draining with water flowing over the curved surface of the dome to the edges of the panel. At the apex of the domed portion holes may be provided for connection to air

nts 16, for example, as illustrated in Figure 1. Domed panels are rticularly useful in forming the roof of a tank where the tank is at a site ere it is exposed to the environment, as illustrated in Figure 1. In this ientation the rim 20 projects into the interior of the tank and the domed gion of the panel presents a concave surface to the water within the tank.

The sump or drain panel that is illustrated in Figures 3a and 3b is so suited as a roof or base panel 6,7 and is similar in construction to the med panel and so like reference numerals have been used for like parts. the case of a sump/drain panel, however, the rim 20 is turned back and rrounds the domed portion so that the centre of the domed region lies thin the plane of the edge of the rim 20. Conveniently, drain holes may drilled through the centre of the panels and connected to outlet pipes d valve controls etc.

The profiled side panel illustrated in Figures 4a and 4b is very similar the sump/drain panel and in many cases side panels are used as sump mets. However, dedicated sump panels ideally have a larger flat area at e base of the sump for enabling secure attachment of a drainage Innection. The profiling of the side panel ensures that deflection of the tnet under full hydrostatic load is reduced and preferably minimised. The It panel, illustrated in Figures 5a and 5b, may be used at any position of 9 tank and consists of a flat surface 21 from which a rim 20 depends lain in the form of a flange.

Although the modular panels illustrated in the accompanying figures ve a square footprint, it will be apparent that other shapes may be plemented that are capable of repeated interconnection such as triangles d hexagons. When constructing a tank, the panels are arranged to abut e another along their edges and with the rims of the panels projecting her inwardly or outwardly, as desired.

Unlike conventional modular panels used in tank construction, the panels illustrated and described herein are moulded from a fibre reinforced thermoset plastics material to which has been added a covering thermoplastic film on one or both sides of the panel. Owing to the structural strength provided by the reinforced thermoset plastics material, the modular panels may comprise only the moulded, reinforced thermoset plastics material and the thermoplastic films. The thermoplastic film is added at least to those surfaces of the panel which will be in contact with water. Hence, the thermoplastic film is applied not only to the flat or domed portion of the panels but also to the surfaces of the rim 20. Thermoplastic material offers greater chemical resistance and resistance to hydrolysis than a conventional thermoset material and so the thermoplastic film acts as a water barrier film on the water contact side of the fibre reinforced thermoset plastics material and ensures that the panel presents an inert surface to the water irrespective of any variations in the curing conditions under which the panel may have been moulded. The thermoplastics material may be selected from one or more of the group comprising polyethylene (high and low molecular weight), NylonTM, polyamide, ethylene vinyl alcohol, polypropylene, homopolymers and ethylene polypropylene copolymers. Preferably, the thermoplastics material is selected from the group of combinations consisting of: (i) high density polyethylene and low density polyethylene, (ii) polypropylene and linear low density polypropylene, (iii) polypropylene and polypropylene copolymer, (iv) Nylon and polypropylene copolymer and (v) Nylon and low density polypropylene.

Whilst the above description makes particular reference to modular panels for a water storage tank, it will be appreciated that other apparatus suitable for water storage and water distribution, which can be moulded from a reinforced thermoset plastics material, e. g. pipes, are anticipated.

As the reinforced thermoset plastics material is capable of acting as Ie supporting structure or matrix, the modular panels and other apparatus lay be constructed only of a main body of moulded reinforced thermoset lastics material having a barrier layer of thermoplastic material.

There are two main methods for manufacturing a laminated panel aving at least a layer of fibre reinforced thermoset material and a termoplastics film : 'in-mould'manufacture or'post-bond'manufacture. oth of these methods are described below.

The'in-mould'method enables the thermoplastic barrier film to be laced in the production mould during the actual manufacturing cycle of the ink panel. The production mould is thus charged with both the termoplastics film material and the fibre reinforced thermoset plastics material and produces a complete panel product in a single stroke of the hydraulic press. This process is reliant on heat transfer to ensure the lermoplastics material bonds and seals to the fibre reinforced thermoset astics material and as such a hot compression moulding method is Jopted. The post-bond'method is used where the panels are moulded sing conventional methods such as resin transfer moulding, spray lay-up r open moulding (hand laminating).

The main body of the modular panels comprises a fibre reinforced ermoset plastics material of the type commonly used in water tank manufacture. In this respect the fibre reinforced thermoset plastics material he substrate material) encompasses sheet moulding compounds (SMC) id low pressure moulding compounds (LPMC) and is formulated either Dm a chemically or physically thickened compounding process. The fibre ) ntent of the material is preferably not less than 20% by weight for the Jrpose of compliance to the hydrostatic tests specified in the current rsion of BS EN 13280: 2001. A surface portion of the substrate material, hich is intended to be in contact with the thermoplastics material, may be

of a different formulation to the rest of the substrate material. Such a surface portion may contain a peroctate initiator and a thermoplastic resin in order to assist in bonding the thermoplastics material to the substrate material. The use of an initiator, however, is not essential as in many cases the thermoplastics film is capable of reliably bonding to the substrate material without any additional activating compounds.

The substrate material requires a lower moulding temperature to that of conventional moulding formulations of 140 to 1500C to enable the thermoplastics barrier film to bond effectively to the substrate material.

This ensures that the various thermoplastics film deflection temperatures are not reached or exceeded and so enabling a greater range of thermoplastics compounds to be employed. The preferred moulding compounds have a moulding temperature of 100 to 125'C, although compounds with moulding temperatures as low as 800C may also be used as they are capable for forming an effective homogeneous bond at the materials interface between the substrate material and the thermoplastics film. Thus, the preferred temperature range of the compounds in the inmoulding process is 80-145 C.

The thermoplastics barrier film is made up from thermoplastic laminate stacks bonded together by tie layers. These laminate stacks may include a variety of thermoplastics materials in dependence upon the service conditions. However, the thermoplastics layer that is in contact with the substrate material is produced from a cast or blown film formulation and likewise the thermoplastics layer that is to be in contact with the water is specifically chosen with regard to the particular environmental conditions it is expected to encounter. The laminate stacks therefore form a sandwich with the central layer acting as a bonding block to meet the requirement of ensuring effective bonding between the outer laminate layers of the stack.

A heated production mould tool, such as the ones schematically ustrated in Figures 6a and 6b, is used in the manufacture of the modular anels. The production mould tool is arranged to effect compression of the ubstrate material and the thermoplastics film to achieve the predetermined ite of compound material flow and ratio of consolidation of the thermoset 1aterial and the thermoplastics material. A hydraulic press is illustrated Ithough low pressure moulding utilising vacuum pumps may alternatively e employed.

The production tool has two opposing platens, one on the top 22 and ne on the bottom 23, to support and hold the production mould tool. The latens 22,23 may be heated (not shown) so that the material within the moulds can be heated during moulding. The production mould tool insists of matched male female 24 and male 25 moulds with, each mould 3cured to its respective platen. Where the platens are not heated, the moulds of the production tool are heated directly. The top platen 22 is mounted so as to be capable of moving from an upper position, in which Ie production mould tool is open, to a lower position, in which the roduction mould tool is closed and applying pressure to any material ithin the moulds. Movement of the top platen is preferably controlled vdraulically but alternative powered drives, such as an electric motor, may 3 utilised, where appropriate.

As illustrated in Figures 6a and 6b, either of the male and female moulds may be mounted on the bottom platen 23 with the other of the two moulds supported and moving with the top platen. Thus, in Figure 6a it is se female mould 24 that is mounted on the top platen 22 whereas in gure 6b it is the male mould 25 that is mounted on the top platen 22. The Section of which of the two moulds is to be moved relative to the other is ade on the basis of the type, size and profile of the particular product 3ing manufactured.

A thermoplastic tensioning frame 26 is provided with the bottom platen 23 and is used to restrain the thermoplastics material 27during the loading sequence. The tensioning frame is positioned around the outside of the mould mounted on the bottom platen and is preferably constructed to accommodate the features of the moulds used to produce each type of modular panel or other moulded article. The use of a separate tensioning frame for the thermoplastics material enables the method described herein to be retro-fitted to existing conventional thermoset moulding tools.

Details of the thermoplastic tensioning frame 26 can be more clearly seen in Figures 7a and 7b. The tensioning frame 26 illustrated in Figure 7a has four sides 28 forming a generally rectangular open structure. Each of the four sides 28 consists of three tensioning rollers 29,30, 31 at least one of which is mounted for controlled rotation about its axis. Preferably all three rollers are capable of controlled rotation. The second of the three rollers, 30, has a surface that holds the thermoplastics film so that rotation of the second roller 30 draws the thermoplastics film 27 between the rollers. Once the edges of the thermoplastics film are secured in the tensioning frame, rotation of rollers on one or more sides of the frame will apply tension to the film extending across the frame. A tension controller may be used to control the rotation of the rollers and so the amount of tension applied to the thermoplastics film.

At each corner of the frame a restraining plate 32 is provided. The restraining plates 32 are secured to the platen so as to prevent movement of the tensioning frame 26 relative to the moulds. Furthermore, at each corner of the tensioning frame or junction where two sets of rollers meet, the thermoplastics film has a substantially triangular portion removed so as to ensure that the edges abut and do not overlap when applied to the material being moulded. Preferably, a template is used to cut the thermoplastics film to size for use in the tensioning frame 26, such a template would include provision for the corner cuts to prevent creasing of

se thermoplastics film during moulding As illustrated in Figures 6a and 6b, where the substrate material 33 , placed in the male mould 25 and the female mould 24 is brought down, bout the male mould, the tensioning frame 26 is normally arranged so that Ie thermoplastics film 27 is positioned over the substrate material 33. In Ie case of the female mould 24 being charged with the substrate material 3 and the male mould being brought down and into the female mould, the msioning frame is preferably arranged so that the thermoplastics film 27 is Icated beneath the substrate material 33. In the case where a panel or ther article is being moulded that requires a barrier layer of thermoplastics material on both sides, two tensioning frames may be employed to position termoplastics film both above and below the substrate material before moulding.

In use, the production mould tool is charged with a predetermined mount of substrate material and with a sheet of thermoplastics film either bove, below or on both sides of the substrate material. The temperature f the moulds are set to the preferred temperature and the upper mould is 'were down on the bottom mould, compressing the substrate material nd the thermoplastics film therebetween. The initial downward stroke is referably rapid, for example less than two minutes and ideally less than ne minute to approximately 50 mm from mould closure. A final, slow Dwnward stroke for the last 50 mm is then performed taking between 10 nd 30 seconds to complete closure. This final slow stroke is required to revent air becoming trapped during the compression. Ideally, the jbstrate material and the thermoplastics film are not in contact with the loulds for longer than approximately 2 minutes during the mould closure 3quence.

As the moulds 24,25 are closed the thermoplastics film comes nder increasing tension and the rollers 29,30, 31 are arranged to respond

to the forces exerted on the thermoplastics film. To prevent tearing of the film during the mould closure sequence, the rollers provide a predetermined amount of slippage. The actual degree of slippage is determined through trials and is dependent upon the shape of the article being moulded, the thickness of the film, the formulation of the film and the temperature of the moulds.

Once the mould tool is closed, the moulds stay closed and the material inside remains subject to the desired pressure for sufficient time to ensure material flow and material consolidation is completed and the material is fully cured. Typically, the time taken from closure of the mould to completing curing is between 5 and 15 minutes. This time is dependent upon the material formulations, the reactivity of the catalyst, the mould temperature and the size and thickness of the material charge pack. The addition of the thermoplastics barrier layer does not alter the curing time from the durations expected with conventional compression moulding of thermoset materials.

When the moulding cycle time is completed, the moulds are opened and the moulded product is ejected. Product release and removal is usually achieved either with hydraulic ejectors built into the moulds or a combination of pneumatic air valve controls and pneumatic or hydraulic ejection pins. The flash edge and the film edge excess are removed using a right angle machined hardened steel bar and then lightly abraded to finish the edges of the moulded product.

The thermoplastics barrier film may alternatively be post bonded to modular thermoset panels produced using conventional mould techniques.

In post bonding, the face and flanges of the thermoset product are abraded, with the grit rating of the abrasive disc or abrasive wash being determined by the hardness of the moulded product. To enable the thermoplastics film to turn and bond to the product's corner angles

ffectively, the corners are abraded to provide a minimum radius of 1.5 im. After abrading the product is washed to remove all lose grit and rease and then dried. The product is then placed in a restraining mould iat corresponds in shape to the profile of the product. Preferably the 3straining mould is heated and is sited in a controlled environment cabinet.

The thermoplastics films that may be used in post bonding are lentical to those suitable for in mould processes. However, a lermo/pressure reactive adhesive is also employed and is applied to the urface of the thermoplastics film that will be contacting the surface of the ) ou) ded product. Ideally, the thermoplastics film is supplied with the dhesive pre-applied to one surface of the film. As described previously ith respect to the in-mould process, the thermoplastics film is cut using a plate so that its shape matches the profile of the product and so as to revent creasing and overlapping of edges of the film.

The thermoplastics film is mounted in a tensioning frame similar to ! e one used in the in-moulding process and is positioned above the moulded product that is in the restraining mould on a movable platform ithin a controlled environment cabinet. The thermoplastics film is then 3ated through control of the temperature within the cabinet. As the ermoplastics film is heated the centre of the film droops and at this stage 3flection of the thermoplastics, the platform is raised lifting the moulded 'oduct up towards the thermoplastics film. The initial contact of the oulded product with the thermoplastics film is thus approximately in the entre of the surface of the moulded product. As the moulded product is 3ing raised, the tension of the thermoplastics film in the tensioning frame increased and the thermoplastics film is gradually draped over the irface of the moulded product. Once the thermoplastics film approaches e edges of the moulded product the movement of the platform is slowed ) that any air trapped between the film and the moulded product can ; cape.

Once the edges of the moulded product have been covered by the thermoplastics film, the film extending beyond the edges of the moulded product are cut either mechanically or manually. The fibre reinforced thermoset product with the thermoplastics barrier layer is then held in the same cabinet or a different temperature controlled cabinet whilst there is a slow and controlled reduction in the temperature to room temperature.

Thus, with both the in-mould process and the post bonding process, a laminate matrix of a fibre reinforced thermoset plastics material and a thermoplastics material is produced which provides excellent load bearing capabilities as well as a high degree of chemical and hydrolysis resistance.

Whilst the invention has been described with reference to modular panel units it will be apparent that the invention may be applied to any apparatus used in water storage and distribution. In particular, the apparatus need not be modular and may be a complete structure, for example but not limited to, tanks, cisterns or pipes.

The methods of manufacturing multi-laminar products of the type described herein are not intended to be limited to the particular embodiments described. Alternative manufacturing methods may be utilised whilst still requiring the application of a thermoplastic film to one or more surfaces of a fibre reinforced thermoplastics material either before or after moulding.

Claims

LAIMS Apparatus for use in water storage or water distribution systems, the Dparatus comprising a main supporting structure being a moulded body of fibre reinforced thermoset plastics material and a barrier layer on at least ie surface of the main supporting structure, the barrier layer substantially insisting of a thermoplastics material selected from the group of ) mbinations consisting of: (i) high density polyethylene and low density ) Iyethylene, (ii) polypropylene and linear low density polypropylene, (iii) Jlypropylene and polypropylene copolymer, (iv) Nylon and ) Iypropylene copolymer and (v) Nylon and low density polypropylene.

Apparatus as claimed in claim 1, comprising a modular element adapted for attachment to further modular elements in the construction of a ater storage or water distribution system.

Apparatus as claimed in claim 2, comprising a plurality of terconnectable modular elements.

Apparatus as claimed in claim 3, wherein the plurality of erconnectable modular panels are adapted for construction of a water nk.

Apparatus as claimed in any one of the preceding claims, wherein e thermoset plastics material has glass fibre as the reinforcing fibre.

Apparatus as claimed in any one of the preceding claims, wherein e thermoset plastics material is a low pressure moulding compound sed on unsaturated polyester resins with or without release agents.

Method of manufacturing apparatus for use in water storage or water stribution systems comprising placing in a mould tool fibre reinforced

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thermoset plastics material and a tensioned sheet of thermoplastics film, heating the materials within the mould and closing the mould tool to compress the materials within the mould tool for a predetermined time period.

8. Method as claimed in claim 7, wherein sheets of thermoplastics material are provided on opposing surfaces of the thermoset plastics material.

9. Method as claimed in claims 7 or 8, wherein the tensioning of the sheet of thermoplastics film is adjusted during closure of the mould tool.

10. Method as claimed in any one of claims 7 to 9, wherein one or more segments of the sheet of thermoplastics material are removed to reduce creasing and overlapping of the thermoplastics material during compression.

11. Method as claimed in any one of claims 7 to 10, wherein the mould tool comprises respective male and female moulds capable of movement relative to one another and wherein the closing movement of the mould tool is performed in two stages with the relative movement of the moulds in the second stage being slower than in the first stage.

12. Method of manufacturing apparatus for use in water storage or water distribution systems comprising providing a sheet of thermoplastics film, one surface of which is coated in a bonding agent; positioning the sheet of thermoplastics film over a moulded element of fibre reinforced thermoset plastics material with the coated surface of the thermoplastics film facing the moulded element; heating the sheet of thermoplastics material; and then bringing the moulded element in contact with the coated surface of the thermoplastics film.