AU2008230015A1 - Non Woven Insulation Products - Google Patents

Description

NON WOVEN INSULATION PRODUCTS FIELD OF THE INVENTION 5 This invention relates to non woven insulation products, particularly to products formed from a mixture of organic and inorganic fibres. BACKGROUND TO THE INVENTION 0 The International Organisation for Standardisation (ISO) defines a non woven as: 'a manufactured sheet, web or batt of directionally or randomly oriented fibres, bonded by friction and/or cohesion and/or adhesion, excluding paper and products which are woven, knitted, tufted, stitch bonded, incorporating binding yarns or filaments, or felted by wet milling, whether or not additionally needled. The fibres may be of natural or man-made 5 origin. They may be staple or continuous filament or be formed in situ'. Fibre glass insulation has traditionally been formed by bonding glass fibres with a phenolic resin. An advantage of using glass fibre for insulation lies in the ability to achieve superior noise and thermal insulation because the finer fibres create more air spaces, when compared '0 to competitive materials such as polyester which are coarser in dimension. The disadvantages of glass fibre insulation are: use of carcinogenic materials (phenolic resin) to bind the fibres, extensive and expensive HSE requirements to control the side effect of using phenolic resins, and less user friendly final products prone to irritate the end user by causing itching. 25 One form of fibreglass is "E Glass", currently used in insulation of electrical conductors subjected to high temperatures. E-glass fibre is also used in both the textile industry and in composites as reinforcement. Benefits of E Glass include: mechanical strength, electrical insulation, incombustibility, dimensional stability, compatibility with organic matrices, non rotting, low thermal conductivity, dielectric permeability, resistance to chemical agents. 30 Thermoplastic materials or blends containing fibres may be thermally bonded. This involves heating the web with hot air. This technique involves heat bonding of fibres in the netlike structure of the web, at their points of intersection. The bonding agent is usually a heat fusible fibre, but thermoplastic powder adhesives are also used. Thermal bonding is possible 1/6 with: Carded webs, Air-laid webs, Wet-laid webs, Spun laid/melt blown webs. Heat fusible fibres have lower melting points than the fibres to which they are bonded. These may be bi component filament or staple fibres which have a high melting point core and a low melting point outer layer. The web is exposed to heat which will melt the outer layer of the fibre, 5 joining the fibres together at their points of intersection. Polyester insulation has traditionally been formed using regenerated polyester fibres, bonded by thermal bonding with a bi-component melt fibre. Advantages of using polyester for insulation manufacture include: higher resilience of the finished products, higher lofts, less 0 user irritation or itching, use of recycled polyester materials. The disadvantages of using polyester are less favourable thermal and noise performance due to a greater fibre diameter and less air spaces for a given overall volume or thickness of finished product. Regenerated polyester fibres are used primarily in the insulation industry as a virgin polyester 5 fibre replacement. They are made from discarded plastic bottles that are chopped up and made into bulk flake or chip that can be reprocessed (extruded) into cut length fibre types. Waste textile fibre is also reprocessed and blended in the extrusion process. Due to it being a regenerated fibre (recycle) it is a cheaper source of fibre for insulation. '0 In bi-component fibres the two polymer components may exist side by side in the fibre or in a segmented configuration. Core-sheath fibres are normally employed in melt-bonding. These core-sheath fibres have a core which has a high melting point while the outer layer has a lower melting point. When the fibres are heated the skin melts or softens and form bonds or spot welds with surrounding fibres, whilst the inner core of the fibre remains intact. The outer 25 layer generally forms 33% to 50% by weight of the total fibre. The sheath melts at 110 degrees while the core melts at 200 degrees C, for example. SUMMARY OF THE INVENTION 30 It is an object of the invention to provide a thermal insulation product with improved physical properties, or at least to provide an alternative to existing products. In one aspect the invention resides in a non woven fibrous product having a structure formed by bonded organic fibres and containing non-bonded or relatively weakly bonded inorganic 2/6 fibres. The inorganic fibres may be considered as trapped within the structure formed by the organic fibres. Preferably the structure of bonded organic fibres includes bi-component melt fibres and 5 mono-component fibres. Preferably the inorganic fibres include glass fibres such as E-glass. Preferably the product involves bi-component fibres at about 15-30%, polyester fibres at about 5 to 30% and glass fibres at about 50 to70%, all by weight. In another aspect the invention resides in a method of forming a non woven fibrous product 0 including: forming a mat having organic melt fibres and inorganic fibres, curing the mat to form a structure of bonded organic fibres, and controlling the curing to limit bonding between organic and inorganic fibres. Preferably the organic fibres include bi-component melt fibres such as sheath-core polymer 5 fibres, and mono-component fibres such as polyester. Preferably curing includes heating the mat to a temperature at which the bi-component fibres form bonds with other bi-component fibres and/or with the mono-component fibres. Preferably controlling the curing includes limited heating of the mat to prevent or reduce bonding of the bi-component fibres to the inorganic fibres. 10 The invention further resides in any alternative combination of features which are indicated in this specification. All alternatives to these features are deemed to be included whether or not explicitly set out. 25 LIST OF DRAWINGS Preferred embodiments of the invention will be described with respect to the accompanying drawings of which: Figures 1 to 4 show typical details of a fibre matrix in the product, 30 Figure 5 is a magnified image showing an actual fibre matrix, Figure 6 shows a profile for a sheath-core fibre, Figure 7 shows a bale opening system, Figure 8 shows an airlay system which creates a fibrous product from the opened bales, 3/6 Figure 9 shows an oven which may be used for curing the product, Figure 10 is a table indicating experimental results for control of the curing process, and Figure 11 is a table indicating properties of finished products. 5 DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings it will be appreciated that the invention may be implemented in a range of different ways to form a range of different products, using a range of different fibres. 0 The embodiments described here are given by way of example only. Figure 1 schematically shows a typical matrix or network of fibres in a product according to the invention. The matrix includes a bonded structure formed by one or more varieties of organic fibre 10, typically bi-component melt fibres and mono-component fibres, such as 5 sheath-core and polyester fibres respectively. These fibres are bonded by melting at their contact points during a curing process. Bonds 12 are shown in an exaggerated form. The matrix also includes inorganic fibres 11, typically a glass composition such as Eglass, which are relatively weakly bonded to the structure formed by the organic fibres, or are not bonded at all. The inorganic fibres are nevertheless tangled and trapped within the organic structure. '0 In general terms, the matrix is created by different bonding characteristics of the various fibre types which have been used. Figure 2 is a closer view of the bonds 12 between three organic fibres, showing a melt fibre 20 crossing two polyester fibres 21, tangled with non bonded glass fibres 22. Figure 3 shows 25 a single contact and bond 30 between organic fibres 31, with glass fibres 32 tacked to the contact region with relatively weak bonds. Figure 4 is an alternative view showing a relatively large number of non bonded glass fibres 40 tangled with relatively large organic fibres 41, and able to move to some extent with respect to the organic fibres. In these examples, the bonds are generally between bi-component and mono-component organic 30 fibres, but could also take place between two or more bi-component fibres or other types of organic fibres. Figure 5 is an electron micrograph indicating the nature of organic-organic and organic inorganic bonds in a real product. An organic-organic bond has been highlighted in this 4/6 example, being a relatively strong weld-type bond between three adjacent fibres. Several failed organic-inorganic bonds have also been highlighted. The curing process was controlled so that flow of molten material at the contacts between organic fibres was sufficient to form strong bonds, while the flow from organic to inorganic fibres was insufficient to form any 5 significant number of lasting bonds. These differences are generally caused by different surface properties of the organic and inorganic materials. Figure 6 is a cross section through a typical bi-component sheath-core fibre showing a temperature profile that is established in the fibre during the curing process. The process is 0 controlled in temperature and duration so that only an outer portion, typically just a few microns thick, of the sheath melts and flows to form bonds with other fibres. Limiting the volume of melted material on the bi-component fibres allows organic-organic bond formation in most cases, but reduces the likelihood that organic-inorganic bonds will form. The organic inorganic bonds generally require engulfment of the inorganic fibre and insufficient melt 5 material becomes available. The bi-component fibres typically have a polyester core and a polyethylene sheath, with thermal conductivities of about 0.15-0.4 and 0.42-0.51 W/mK respectively. Figure 7 shows a generally standard system for opening and blending bales of fibres. Fibre 0 bales are placed on a conveyor 70. As the conveyor moves forward a spike lattice picks up and drops slices of fibre onto an entry conveyor. The fibre then passes through a series of rollers with card wire which "open" large clumps. On exiting the opening process the fibre is in an individualised state is then typically delivered to a carding process as described below. A range of opening systems are available. 25 Ternary products with three primary fibre types (two organic and one inorganic) are currently preferred and require a blender having three feeders of this kind. A combination of bi component melt fibres and mono-component fibres is preferably used with E-glass as the inorganic fibre. A simpler binary system such as bi-component fibres with E-glass may also 30 be used. Products tested so far have involved bi-component fibres at 15-30%, polyester fibres at 5 to 30% and glass fibres at 50 to70% by weight. The inorganic fibres were Eglass with a diameter of 4 to 14 microns. 5/6 Figure 8 shows a generally standard airlay system which forms and cures a mat containing the required fibre types. Fibre is taken by conveyor 80 from an opening system such as described above. The fibre passes though the airlay system to form a mat on a further conveyor 81. The airlay system typically includes a nosebar and lickerin arrangement, and an 5 air current which throws the fibre onto a rotating drum, in a generally standard process which need not be described in detail. The nosebar is preferably a double nosebar combination. The thickness of the matt depends on the speed of the rotating drum and conveyor 81. A range of airlay systems are available. Alternatively carding and crosslapping systems may be used. 0 Figure 9 shows an oven which may be used to cure the mat from the airlay process described above. In this example the oven carries the mat through a temperature controlled zone using a pair of conveyors 90, 91. The temperature and duration of the curing process determines the bonding which takes place between the fibres in the mat. The process is controlled to limit the bonding between organic and inorganic fibres. Preferably the process creates a 5 product having a structure with relatively strongly bonded organic fibres and containing non bonded or relatively weakly bonded inorganic fibres. The structure of organic fibres thereby forms a matrix which contains the inorganic fibres and can offer useful physical properties. Figure 10 shows a range of experimental results for various curing processes which have '0 been tested to date. The table shows a series of oven temperature and oven dwell times for a blended fibre mat. In this example, acceptable matrix structures can be seen for oven temperatures of 110, 140, 170, 200 degrees C at corresponding dwell times of 12, 10, 8 and 6 minutes. At higher temperatures and/or longer times a larger number of organic-inorganic bonds begin to form, and eventually the bi-component fibres melt entirely. The range of 25 temperatures and dwell times will depend on the particular oven which is used and the particular combination of organic and inorganic fibres. Figure 11 shows thermal rating data for a range of products tested to date. Preferably these products have a loft between 50 and 200mm, and a weight of between 900 and 3000 gsm. 30 Their properties compare favourably with current market products. In general terms, the products can have higher loft and be more resilient than conventional products. It also incorporates glass fibres without the need for the noxious phenol bonding agents used with fibreglass products. 6/6

Claims (14)

1. A non woven fibrous product having a structure formed by bonded organic fibres and containing non-bonded or relatively weakly bonded inorganic fibres. 5

2. A product according to claim 1 wherein the structure of bonded organic fibres includes bi-component melt fibres and mono-component fibres.

3. A product according to claim 1 wherein the organic fibres include bi-component melt 0 fibres and the inorganic fibres include glass fibres.

4. A product according to claim 1 wherein the inorganic fibres are trapped within the structure formed by the organic fibres.

5 5. A product according to claim 1 including bi-component fibres at 15-30%, polyester fibres at 5 to 30% and glass fibres at 50 to70%, all by weight.

6. A product according to claim 1 having a loft between 50 and 200mm, and a weight of between 900 and 3000 gsm. 10

7. A product according to claim 1 wherein the inorganic fibres are Eglass with a diameter of 4 to 14 microns.

8. A method of forming a non woven fibrous product including: 25 forming a mat having organic melt fibres and inorganic fibres, curing the mat to form a structure of bonded organic fibres, and controlling the curing to limit bonding between organic and inorganic fibres.

9. A method according to claim 8 wherein the organic fibres include bi-component melt 30 fibres such as sheath-core polymer fibres, and mono-component fibres such as polyester.

10. A method according to claim 9 wherein curing includes heating the mat to a temperature at which the bi-component fibres form bonds with other bi-component fibres and/or with the mono-component fibres. 1/2

11. A method according to claim 8 wherein controlling the curing includes limiting heating of the mat to prevent or reduce bonding of the bi-component fibres to the inorganic fibres. 5

12. A method according to claim 8 wherein the inorganic fibres include E glass.

13. A product according to any one of claims 1-7 and substantially as herein described with reference to the drawings. 0

14. A method according to any one of claims 8-12 and substantially as herein described with reference to the drawings. 2/2