AU760893B2 - A polymer composite - Google Patents

Description

CD99256018.9 1A A POLYMER COMPOSITE Field of the Invention The invention relates to a method of forming a material from polyester or other organic (as herein defined) fibres. The invention has a particular application to the production of an insulation material suitable for pipework (and the like) for both heat and sound. In particular, the insulation material also includes heat bonding fibres before curing.

Background Pipes are a common means used for transporting flowable materials over relatively short distances, such as less than 1 kilometre, although there are of course many longer "pipelines". In many instances, there is a need for thermal insulation between the pipe and its environment in order to minimise the transfer of thermal energy between the fluid within the pipe and the environment. The purpose of doing so may be to minimise the impact of the fluid's temperature on 15 the temperature of the environment or vice-versa. In addition, the passage of fluid along a pipe may generate sound energy which is not desirable in the environment of the pipe. In these circumstances, acoustic insulation around the pipe is desirable.

It is usual to install the insulation around the external surface of the pipe, 20 although it is, in some cases, possible to locate the insulation either on the internal surface of the pipe or within the construction of the pipe itself.

Known pipe insulation materials are generally manufactured from different materials depending upon whether the usual operating temperature will be significantly above the normal atmospheric temperature or significantly below.

Where the temperature will be significantly above ("hot pipework"), mineral fibres are used, such as fibreglass or rockwool. Where the temperatures are substantially below, polystyrene, organic nitrile or polyolefin foams are used.

These materials have known disadvantages.

CD/99256018.9 2 Fibreglass and rockwool products may raise occupational health and safety problems. Products made from these mineral fibres are subject to regulations controlling their use on construction sites because of their potential dangers of fibre fragments to the health of workers. There is an industry and regulatory pressure to avoid the use of these materials where safe alternatives are available.

However, at present, for insulation of pipes operating substantially above atmospheric temperatures, alternatives are not readily available.

Where the temperatures are significantly below atmospheric temperature, fibreglass and rockwool products have also been used. However, given the dangers described above, it is now more common to use polystyrene or other organic foam products as the insulating material. These materials are, however, unsuitable for applications in temperatures significantly above usual atmospheric temperatures.

Typically, these products are used in cost-sensitive situations. Accordingly, the cost of production is important in the feasibility of a new product for insulation in this manner.

To achieve a particular thermal performance, both the thickness and density of the insulation material are relevant. Greater insulation is achieved by greater thickness and density. Traditional fibreglass and rockwool products are manufactured in densities over 80kg/m 3 and with a minimum thickness of about 25mm. This is due to the limitations in the ability to process the input raw materials. Thus, this provides a relatively high minimum amount of insulation performance which may be significantly more than is required for a particular application. Significantly improved thermal insulation performance can only be achieved (in the range of densities of material used, ie. over 40kg/m 3 by increasing the thickness of the insulation material on the pipe, in other words using a greater amount of raw material. Thus, a pipe insulation material which could be made of a lower density and/or thinner thickness than these minimums would enable a greater variation in insulation product specifications so that there is less usage of raw materials where they are not required.

CD/99256018.9 3 Pipe insulation materials of fibreglass or rockwool may be made by either a manual or an automatic process. The manual process may be described as follows (with some of the attendant disadvantages): a "blanket" of uncured phenolic/urea formaldehyde resin and fibreglass must be manufactured (usually in the form of a roll) with a nominal weight/m 2 percent residual moisture content, percent binder/resin content and dimensions (which product only has a useful shelf life of about one week); the resin/fibreglass material is mechanically wrapped by an operator, who is inevitably exposed to the uncured wool and its off-gases of formaldehyde and ammonia, around an oil and release-agent coated pipe mandrel to the approximate weight and thickness necessary to achieve the **insulation specified (by density and thickness) a proportion of the release agent may contaminate the pipe insulation which may affect the insulating properties and also require excessive consumption of the release agent; S(c) due to the inherent nature of the uncured blanket (which may vary due to density variations, excessive stretching and lack of dimensional definition), achievement of a particular insulation density within a narrow range in the finished product is extremely difficult, and thus particularly small diameter pipe products are made at significantly "over specification" to achieve a product with sufficiently even insulation properties throughout its length often, the operator must patch and roll extra fibreglass/resin material onto the mandrel during the roll-up process rather than being able to use a set length of input resin/fibreglass blanket; the mandrel/blanket assembly is loaded onto a trolley and moved into an oven to cure for a least 1 to 2 hours pollutants (such as formaldehyde, phenol and ammonia) are produced from this process and must be disposed of or released; CD/99256018.9 4 the mandrel/blanket assemblies are then withdrawn from the oven to cool in the case of mineral wool products that have not been wrapped in paper at the end of steps or they may then be sanded down to a final product thickness; the cured pipe insulation material is then mechanically pushed from the pipe mandrel and the fibreglass insulation is simultaneously slit along its length; and the pipe insulation material is then trimmed to the required length, its quality checked by weight, dimensional specification and visual requirements (such as softness brought about by uneven density or poor cure due to high moisture levels) and then packed, usually in cardboard 000. boxes due to the friable nature of the product. Excess material is usually disposed of (eg, landfill).

In an automatic process, the uncured blanket is wrapped around a mandrel which has been pre-heated and, once wrapped, the assembly is run over heated rollers which, together with the amount of blanket used, set the thickness of the finished product. The assembly is then passed through an oven to cure as in the o manual process and then trimmed and packed.

In this specification and the appended claims: the term "melt fibre" is used to mean a fibre, which may be mono or bi component, located within a mat with a melting point significantly lower than that of the other fibres and which is included for the principal purpose of melting upon curing to bind the bulk of the fibres in the mat together, in a manner known to one skilled in the art; and the term "organic" when used in respect of a fibre refers to a fibre which is primarily polymeric and carbon-based to distinguish it from the glass fibres and mineral fibres used in the prior art, but does not necessarily imply that the fibre may be found naturally.

Investigations have been carried out into the formation of an insulation product for hot pipework which is manufactured from a material, which may be fibres, which are occupationally safe for both manufacturers and installers, without significantly lowering performance as an insulating material. A further object of these investigations was to develop a method for producing such a material in a cost-effective manner.

Summary of the invention According to one form of the invention, there is provided an insulation product for pipes including a mat of organic (as herein defined) fibres, the mat including melt fibres (as herein defined). The mat is a blend of the organic fibres and melt fibres. Preferably, the product insulates against thermal energy.

Alternatively, it insulates against sound energy, or both.

Preferably, the insulation product is manufactured in the form of a tube.

More preferably, this is achieved by wrapping the product around a mandrel before curing.

Advantageously, the organic fibre may be selected from one or more of the S: group polyester, polyolefin, nylon, aramid and para-aramid.

Preferably, the organic fibres have a denier of between 2 and 24.

Preferably, the insulation product has a density in the range of 32 kg/m 3 to 96 kg/m 3 Preferably, the ratio of organic fibres to melt fibres is about 3:1.

The invention also provides a method for producing an insulation material for pipes including the steps of: CD/99256018.9 6 wrapping a mat of carbon-based polymer fibre containing a melt fibre (as herein defined) around a mandrel; separating the mandrel from the mat; curing the mat in an oven.

Preferably, the insulation material will have been trimmed. More preferably, the insulation material is also slit along its length to facilitate location over a pipe in situ.

In another form of the invention, an insulation product is provided which has been manufactured according to method described above.

o 10 Brief Description o :The invention will now be described with reference to the illustrations in which: Figure 1 is a perspective schematic view of a pipe insulated by a material in accordance with a preferred embodiment of the invention.

Figure 2 is a perspective schematic view of the wrapping machine used as explained below in the manufacture of an insulation material according to an embodiment of the invention.

Figure 3 is a perspective schematic view of the compression rollers described below in the manufacture of an insulation material according to the invention.

Figures 4 and 5 are graphs of thermal conductivity relationships as explained below.

Figures 6 and 7 are graphs of acoustic conductivity relationships as CD/99256018.9 7 explained below.

In the illustrations, for convenience only, like components are referred to by the same reference numeral.

In order to overcome the potentially dangerous side-effects of using fibreglass or rockwool products, the insulation material of the invention is manufactured from a polyester or other organic (as herein defined) fibre. The process for manufacturing the pipe insulation material of the invention is as follows: a blanket is manufactured from an organic fibre by known carding and cross lapping methods into which is also blended a melt fibre; o:oo go a predetermined length of the blanket of known weight or density and dimensions is wrapped around a pipe mandrel so as to achieve the required insulation density and product thickness the mandrel does not require pre-treatment with a release agent; 15 a non-woven scrim may then be wrapped (usually one to two times) around the blanket (usually commencing with the last two metres of the blanket) to set the thickness of the finished product as well as its surface finish the scrim may be adhered to itself (eg. by melting a polyethylene coating on the scrim which overlaps the previous layer or by use of a polyvinyl acetate adhesive) to tighten and thereby define the diameter of the wrapped blanket; remove the mandrel from the rolled blanket; the blanket retains its tube shape and is bonded in an oven in thetraditional way and then, once cooled, trimmed as described above; the tube of insulation material is then slit lengthways to enable it to CD/99256018.9

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8 be located around a pipe in situ and trimmings from step can be shredded for re-use.

It is significant that the manufacturing process does not involve exposure to materials which have been shown to have deleterious effects on workers' health, such as formaldehyde. Further, by reason of the nature of the textile "raw material" used, trimmings of the product after it has been cured in the oven are recyclable as they are able to be shredded and used as a raw material in the manufacture of the blanket in step Of course, the insulation product may then be faced with aluminium foil or a paper vapour barrier as is known, particularly for thermal insulation.

Alternatively, in step the mandrel and wrapped blanket may be finally wrapped with a non-woven textile to facilitate achieving an even thickness and even presentation of the finish or external surface of the insulation product.

It will be apparent that a pipe insulation product made in this way has a 15 number of benefits. The use of a blended input raw material (ie, one with a melt fibre) enables greater range and control of the thickness and density of the finished product which allows greater tailoring of the product to the insulation specifications required by its end use. Further, the use of organic fibres allows the options of manufacturing insulation products for different temperature ranges by 20 selection of the appropriate base organic fibre according to its characteristics.

Further, coloured fibres may be used to identify products intended for specific applications without the need for colour to be added as a separate step, thereby decreasing the cost of production of the product. Finally, insulation products made from these raw materials are much safer to use as they do not give off the fibre "dust" of mineral and glass fibres which has been shown to be deleterious to human health.

The relationship between density to thermal conductivity of both fibreglass CD/99256018.9 9 insulation material and polyester insulation material is shown in Figure 4 for densities ranging from 15kg/m 3 to nearly 50kg/m 3 It can be seen that the reduction in thermal conductivity with increasing density (for a given thickness) becomes relatively small with densities over about 40 kg/m 3 The thermal conductivity of pipe insulation made from polyester was compared with that of insulation made from fibreglass. Figure 5 plots the results of the thermal conductivity at several temperatures for polyester pipe (at 80 kg/m 3 density) compared with fibreglass (at 96 kg/m 3 density). It will be seen that, as a general rule, the fibreglass had a lower thermal conductivity for the same given temperature, and this would not be due to any significant extent to the greater density (as shown in Figure 4).

Where acoustic conductivity is concerned, insulation is improved by *I increasing the wall thickness and/or the weight per square metre of the cladding.

:9 .9The relevance of weight per square metre is demonstrated in Figure 6 where, overall, the acoustic insulation provided by the higher weight product provided the greater insulation. In Figure 7, the advantages of the invention are apparent where polyester sound insulation provides better insulation over a range of o frequencies (other than 900 to about 2000 Hz) with half the wall thickness compared with fibreglass cladding of the same weight.

*99999 Examples 99 A blanket is manufactured of 200 g/m 2 density in a width of about 1250mm and 60m long with a specific blend of textile fibres, being 75% 6 denier polyester and 25% polyester melt fibres (melting point 1800C). The blanket composition is formulated to meet the maximum anticipated surface temperature of the pipe for which the insulation is intended and from which insulation is required. The blend of fibres is then carded and cross-lapped to form a blanket, which is then thermally bonded using a through air process. It will be appreciated that this product has a shelf life which, in practical terms, is indefinite.

CD/99256018.9 As shown in Figure 1, the length of blanket 1 is fed via conveyor 7 to mandrel 2 in rolling machine 3. The blanket 1 is wrapped around mandrel 2 to commence formation of a roll of blanket. After the initial feed, mandrel 2 is lowered and the remainder of the blanket rolls between compression rollers 4 as illustrated in Figure 2. The length of blanket to be rolled is pre-set. Once the complete length of blanket is wrapped around the mandrel 5 (as shown in Figure the mandrel and blanket combination is raised from between the compression rollers 4 so that the compressed roll of blanket 6 can be further processed (eg. by adding a scrim) and then cured. Such polyester blanket manufacture and rolling is known in the art and has been used for other purposes.

A specific length of the bonded blanket is then cut in view of the ultimate desired thickness and density of the insulation material to be manufactured. In this example, 2.1 metres of the blanket of width 1250mm is selected. The specific *too 15 length is stored on an unlined stand. A pipe mandrel (which may have a diameter of between 12 and 210mm as required by the external diameter of the pipe in the end use required) is mounted in between two compression rollers located between the unlined stand and the mandrel. The set length of blanket is then wrapped o: around the mandrel at the required density and thickness by controlling the tension in the blanket during the wrapping process, for example a density of kg/m 3 can be achieved at a tension of 1 000kPa. The width of the set length of blanket is slightly greater than the ultimate pipe length desired to allow for trimming after curing. The blanket is rolled on under an appropriate tension for an appropriate length to achieve the calculated thickness and density required for the insulation specifications of the insulation product to be manufactured. If desired, a non-woven scrim or non-woven tissues (such as a polyethylene coated non-woven scrim) may be rolled on to the blanket to improve the outer surface of the insulation product. The mandrel is then removed easily and safely by hand, as no toxic release agent is required.

The rolled blanket placed on a trolley. Preferably, the rolled blanket is left on the trolley until the trolley is full when it can be inserted into an oven at 1800C for 1.5 hours. Once removed from the oven, the insulation material is allowed to CD/99256018.9 11 cool. The insulation material can then be slit down its length and trimmed to the appropriate length by a band saw.

Referring to the blanket which is the raw material in the process described in this example, the fibre content must be appropriate to achieve the insulation product performance requirements of thermal non-conductivity, dimensional stability and surface temperature suitability. The fibre blends must therefore contain either polyester, polyolefin (melting point around 1350C), nylon (melting point around 2600C), aramid (up to 3700C), acrylic or para-aramid (such as

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fibres (up to 3700C) or mixtures thereof. The denier range is from 2 (for maximum thermal performance per unit of density) to 24 (for maximum compressive strength and more moderate thermal performance). These fibres are mixed with a "low" melt fibre (melting point over 1300C). The preferred melt fibre is a polyester co-polymer of the core and sheath type with the outer sheath having a melting point of greater than 13000 and the core around 2500C. Melt fibres with a melting point greater than 900C may also be used in some applications of the present invention.

:t In this manner, a pipe insulation material can be manufactured with a density of as low as 32kg/m 3 and a wall thickness as low as 9mm.

ease Pipe insulation materials were manufactured according to the invention as set out above for a pipe of nominal bore of 40mm, which required insulation because it was carrying water at an operating temperature of 850C. Insulation product was made with a polyester fibre which was faced with an aluminium foil laminate (as known in the art). The nominal product density of the polyester blanket was 80kg/m 3 and the thickness of the insulation material was 25mm. The purpose of the insulation material was to reduce the external surface temperature of the pipe to below 650C, which was required for occupational health and safety requirements. The installation of the insulation material reduced the surface temperature to 570C. By comparison, an aluminium foil faced fibreglass pipe insulation product with the same thickness of 25mm but a higher density of 96kg/m 3 reduced the surface temperature to 5500. Although this is marginally CD/99256O18.9 12 lower than the insulation material of the invention, it was significantly more expensive to produce, given the higher density of material incorporated.

It will be apparent that there is an upper limit to the temperature range which an insulation material manufactured by this process can be used. This upper limit is determined by the melting point of the binder fibre of the blanket, of which some examples of possible different fibres and their melting points are given above.

The insulation material of the invention may also be used as acoustic insulation around the external surface of a pipe. Noise isolation of liquid filled pipework such as plastic (eg PVC sewer pipes) and copper is currently undertaken with polyurethane foam faced with an outer layer added to the rolled blanket) loaded vinyl/PVC (a PVC resin and plasticiser) sheet or ethyl vinyl acetate (usually a Barium salt) sheet of 2 to 8 kg/m 2 weight but only several millimetres thickness, both of which are known commercially available products. These add a dense outer layer to improve acoustic insulation properties. The required length for insulating the pipe must be cut from rolls and then wrapped and taped around the pipework.

e• e Pipe insulation made according to this invention faced with loaded vinyl type products has been shown with sound insertion loss testing to provide a leooe S 20 significant improvement in the acoustic isolation of pipework compared to S°traditional systems. In addition, the insulation, being preformed to the pipe size, can be installed rapidly without cumbersome cutting and wrapping and the durability of polyester type fibres will allow the product to remain in service for the life of the pipes. In contrast, polyurethane foams have been shown to degrade over time. A scrim of the loaded vinyl/PVC or EVA sheets may also be added to the insulation made according to the invention to improve the acoustic insulation performance.

It will be apparent to one skilled in the art that the advantages of such an insulation material include the following. The manufacturing process minimises or CD/99256018.9 13 avoids exposure of operators to dangerous materials, such as formaldehyde, phenols and mineral fibres during the manufacturing process. Further, such undesirable pollutants are not produced during the curing process. The use of bonded blankets in the wrapping process enables greater control of the density and thickness of the finished product. Insulation products made in this way are more safely handled on site as the nature of the fibres is such that they are not prone to endanger the health of workers. Trimmings during the manufacturing process can be recycled into the feed stock. Different fibres can be used in the bonded blanket for different applications. The product manufactured in this way is more plastic and is more securely bonded and thus the resulting product is less friable and does not disintegrate on handling and storage. This reduces packaging and handling requirements and cost.

SIt will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the o: 15 individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

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Claims (1)

1. 22. 24 An insulation product substantially as herein described with reference to, or with reference to and as illustrated in, the accompanying drawings. A method for producing an insulation product substantially as herein described with reference to, or with reference to and as illustrated in, the accompanying drawings. Pacific Brands Clothing Pty Ltd By its Registered Patent Attorneys Freehills Carter Smith Beadle 22 January 2003