More particularly, the invention relates to insulating material which can be used as thermal or acoustic insulation.

In the building industry in Australia and other countries, the most common form of thermal insulation used is fibreglass batts. The main reason for this is that they are relatively cheap. There are, however, health hazards associated with the use of fibreglass including, but not limited to, irritation of skin and eyes.

There have been attempts to use other materials for insulation as an alternative to fibreglass. Paper or bonded cellulose is a logical alternative because it is relatively inexpensive and can be made into insulating material which has high thermal and acoustic resistance. The thermal resistance is a function of the density and the thickness of the product. The thickness of the product is normally referred to as"height"or"loft"of the product because it is formed as a horizontal layer where the height or loft of the product constitutes the thickness of the insulating material. Relatively low densities can be achieved when the height, loft or thickness of the product is small. At the present time an insulating batt, roll or blanket made from or including cellulose fibres has not been commercially available because it has not been possible to achieve a sufficient thickness of the product whilst maintaining the density relatively low. Higher density products are uncompetitive because of higher raw material costs and the additional weight makes their use unattractive to installers of the insulation.

Another problem which has occurred in previous attempts to produce batts, rolls or blankets of insulating material which include cellulose fibres at low density is that the original loft is reduced after package and cartage. Initially low density cellulose batts have either collapsed or re-densified resulting in a reduction of their thermal and acoustic resistance.

An object of the present invention is to provide insulating material which includes cellulose fibres which are stable and are of relatively low density so that thermal and acoustic resistance properties are maintained.

According to the present invention there is provided a method of making insulating material including the steps of : (i) forming a web of fibrous material including cellulose fibres and spring fibres; (ii) forming the web so that it is corrugated, lapped or wave shaped; and (iii) treating the web so that it remains corrugated, or lapped or wave shaped.

Preferably, the spring fibres constitute approximately 10% to 25% by weight of the web.

Preferably further, the step of treating the web so that it remains corrugated includes the step of bonding adjacent corrugated or lapped or wave shaped parts of the web together.

Preferably further, the bonding is effected by adding bonding material to the web and heating the web to a temperature which exceeds the melt point of the bonding material so that said adjacent corrugated or lapped or wave shaped parts of the web are bonded together.

Preferably, the density of the web is in the range lOkg/m3 to 50kg/m3 and preferably less than 20kg/m3.

Preferably, the density of the insulating material is in the range 1 Okg/m3 to 5Okg/m3 and preferably less than 20kg/m3.

Preferably further, the web has a thickness in the range from 1mm to 70mm and

more preferably in the range 20mm to 70mm.

The invention also provides apparatus for making insulating material, the apparatus including means for forming a web of fibrous material including cellulose fibres and spring fibres, forming means for forming the web so that it is corrugated or lapped or wave shaped, and treating means for treating the web so that it remains corrugated or lapped or wave shaped.

The invention also provides insulating material including a web of fibrous material which includes cellulose fibres and spring fibres, the web being treated so that it is bonded into a corrugated or lapped or wave shaped configuration.

The insulating material can be in the form of a batt, roll or blanket.

The shape of the corrugations can be adjusted so as to vary the effective thickness of the batt, roll or blanket. The thickness of the batt, roll or blanket determines its thermal and/or acoustic resistance. The batt, roll or blanket can be appropriately sized so that it can be fitted in various cavities normally found in buildings including wall cavities, and spaces between floor joists, between rafters or ceiling joists.

The corrugating lapping or wave shaping of the web is applicable to fibrous material which does not necessarily include cellulose fibres. Accordingly, a further object of the invention is to provide a novel method of making insulating material from webs which include cotton, fibreglass and/or polyester.

The invention also provides insulating material including a web of fibrous material which includes insulating fibres and spring fibres, the web being treated so that it is bonded into a corrugated or lapped or wave shaped configuration.

The invention will now be further described with reference to the accompanying drawings, in which:

Figure 1 is a fragmentary view of insulating material made in accordance with the invention; Figure 2 is a schematic drawing showing apparatus suitable for making the insulating material of the invention; Figure 3 is a more detailed schematic view of part of the apparatus of Figure 2; Figure 4A diagrammatically shows a web laminated on both sides prior to folding; Figure 4B is a diagrammatic cross-section through a laminated product; Figure 4C is an enlarged view of a laminated product; Figure SA is an enlarged view of another form of laminated product; Figure 5B is an enlarged fragmentary view of the modified product; Figure 6A is a schematic view of another form of laminated product; Figure 6B is an enlarged fragmentary view of another form of laminated product; Figure 7A is a schematic view of a still further form of laminated product; and Figure 7B is an enlarged fragmentary view of the further form of enlarged product.

Referring first to Figure 1, there is shown a fragmentary perspective of a piece of insulating material 2 of the invention. The insulating material can be used for thermal and/or acoustic insulation. As will be described in more detail hereinafter, the insulating material 2 is first formed as a web 4 of insulating material which is then corrugated or lapped or formed into a wave shape as shown. The corrugated or lapped or wave shaped web is then treated so that it maintains its shape so that the height H thereof determines the thickness of the insulating material 2. The insulating material 2 can be cut into batts, or into blankets or formed into rolls.

In the preferred process of the invention, the web 4 includes bonding material in the form of thermoplastic bonding fibres and spring fibres as described in more detail below.

The thermoplastic bonding fibres are heated above their melt point so as to form the web 4 and maintain its integrity as a web. The web 4 is then corrugated or lapped or formed into a wave shape and is again heated above the melt point of the bonding material so that bonded regions 6 are formed between adjacent convolutions 8, as shown in Figure I.

Figure 2 schematically illustrates the preferred apparatus 10 for forming the insulating material 2. The apparatus includes a cellulose preparation stage 12, fibre mixing stage 14, web forming stage 16, corrugating stage 18 and cutting and packing stage 20.

The cellulose preparation stage 12 includes a hopper 22 which receives waste material which includes or consists of cellulose fibres. Typically the waste material would include waste paper or cardboard material. It is preferred that newspaper stock and/or used telephone directories are used as the source of the cellulose fibres. The fibres pass to a shredder 24 which tears or cuts the paper into relatively small pieces. This is typically done using spinning knives or blades. The pieces of paper then pass to a hammermill 26.

The piece of paper can be transported by means of a stream of air. The hammermill 26 reduces the pieces of paper to fibre and hammermilling or fibreizing takes place until the cellulose fibres are small enough to pass through a screen 28 of a predetermined hole size.

Preferably, the hole size of the screen 28 is in the range from 2mm to 1 Smm for producing fibre having a relatively high R value, the R value being a measure of the thermal resistance. The hole size for the screen 28 would depend on the type of hammermill and fan used for conveying the fibres. In a prototype apparatus a Williams serial number 12686 hammermill is used with a 150HP motor and in this case the preferred hole size for the screen is 8mm. A high proportion of individual fibres compared to the number of flakes of paper usually yields a higher R value. Depending on the type of paper, there is a point where if the holes in the screen 28 are too small, they tend to break the fibres down too much resulting in a web which does not have sufficient loft or height. The screening could be done within the hammermill 26.

Where the insulating material 2 is to be used in buildings, it is normal for a fire retarding material to be added so as to reduce fire risk. Accordingly, the cellulose preparation stage includes a hopper 27 for adding fire retardant 29 to the fibres emerging from the screen 28. Preferably the fire retardant is borax or boric acid and is added so that it constitutes about 7% to 17% by weight of the insulating material 2.

The fibre mixing stage 14 is for the purpose of adding to the fibreized cellulose

material from the screen 28, bonding fibres 31 and spring fibres 36.

The fibre mixing stage 14 includes a bonding fibre hopper 30 which receives bonding fibre 31. The bonding fibres 31 are thermoplastic fibres having a length in the range from 2mm to 25mm and a thickness in the range 3 to 28 denier. The fibres are thermoplastic and have a melt point at about 110°C. The preferred material for the bonding fibre is a mix of PE/PET fibres. The melt point of the bonding fibres 31 is less than the combustion point of the fibreized paper and less than the melting point of the spring fibres, as discussed below.

The fibres 31 pass from the hopper 30 to a carding or fibre opening unit 32 so as to separate the fibres and avoid balling of the fibres.

The fibre mixing stage also includes a spring fibre hopper 34 into which spring fibres 36 are introduced. The spring fibres 36 are preferably synthetic fibres having a length in the range from 12mm to 100mm and a diameter from 15 to 150 decitex. The fibres also have a melt point which is above the melt point of the bonding fibres.

Preferably the melt point of the spring fibres is greater than 150°C. The preferred material for the spring fibres is PET. The spring fibres 36 can be of the type which is used in upholstering furniture or in the manufacture of pillows and are sometimes referred to as pillow fibres. Recycled spring fibres are often made from textile waste such as that produced as offcuts in the manufacture of sporting footwear or pet bottles, the material usually being melted down and re-extruded as spring fibre. The fibres are crimped so as to give them bulk and inherent resilience.

The spring fibres 36 from the hopper 34 pass to a carding or fibre opening unit 38 to again ensure that the fibres are as separate or open as possible and that balling thereof is avoided.

The bonding fibres 31 and spring fibres 36 pass to a dosing control unit 40 which controls the rate at which these fibres are introduced into a fibre mixer 42 which also

receives cellulose fibres from the screen 28. The dosing control unit 40 controls the rate of addition of the bonding fibres 31 and spring fibres 36 relative to the rate of the cellulose fibres added to the fibre mixer 42. The dosing control unit 40 can be used to adjust the relative ratios of the weights of materials added to the fibre mixer 42 and hence of the mixed fibre which forms the web 4. Table 1 below sets out the various weight percentages of the components.

TABLE 1 Ingredient Length Decitex Melt Screen % of % of Preferred Range Denier Point Size mm Mix Low Mix % of mm Celsius High Produce Bonding Fibre 2-25 3-28 110 NA 5 20 7 Denier Spring Fibre 15-150 Above 12-100 Decitex 150 NA 10 25 17 Borax/Boric acid NA 7 17 9 Cellulose Paper NA 2-15 78 38 67 Totals NA NA NA NA 100% 100% 100% The web forming stage 16 includes a web forming apparatus 44 which forms the mixed fibrous material from the fibre mixer 42 into a generally uniform layer of a predetermined height on a conveyer belt (not shown). The web forming apparatus 44 may be of known type such as a chute, air-lay, vacuum belt, or combination of these known types of equipment. Alternatively, the web forming apparatus 44 could be of the type disclosed in International Publication WO 99/36622. Apparatus of this type forms a generally uniform layer of mixed fibrous materials moving on a conveyer belt. The web forming stage 16 also includes a bonding oven which includes convection or radiant heaters for heating the fibrous material conveyed therethrough. The bonding oven 46 is arranged to heat the fibrous material to a temperature which is above the melt point of the bonding fibre 31 but below the melt point of the spring fibre 36. Accordingly, the bonding oven 46 heats the materials to a temperature greater than 110°C and less than 180°C and

preferably 145°C. This heating causes the bonding fibres 31 to reach their melt point in which they adhere to one another as well as to the cellulose and spring fibres. The material so heated is then conveyed to a cooler 48 which reduces the temperature to below the melt point of the bonding fibre. The formed web 4 therefore emerges on the conveyer from the cooler 48. The bond fibres thus hold the web into a structurally coherent web of fibrous material. The spring fibres will be randomly oriented and bonded to the cell fibres and to each other. The spring fibres add resilience to the web 4 and ensure that the loft in the web is maintained.

The web 4 then passes to the corrugating stage 18. The stage 18 includes a forming stage 50 which causes the web 4 to be corrugated, lapped or wave shaped. The forming stage 50 can be implemented in a number of different ways. Figure 3 diagrammatically illustrates one way in which the forming stage is implemented. In this diagram the forming stage includes nip rollers 52 which partly compress in order to enable the web to be pulled through the apparatus. The nip rollers 52 compress the web 4 by an amount in the range from 5 to 50% so as to consolidate the web somewhat but without destroying the inherent loft which is maintained by virtue of the spring fibres 36. Typically, the layer 4 may be about 4mm in thickness at this stage and the rollers 52 compress the web 4 to about half its thickness. The thickness will, however, increase somewhat after leaving the rollers by virtue of the resilience provided by the spring fibres 36. After the web 4 has been formed so as to define the adjacent convolutions, the web thickness is of the order of say 50% of its thickness prior to passing through the nip rollers 52. The web 4 is then fed to shaping rollers 54 which are opposed to one another so as to define a wave shaped travel path for the web 4, as shown. The rollers 54 are preferably driven so that they assist in feeding the web therethrough. Also the spacing of the rollers in the upstream/downstream direction can be adjusted as well as the relative spacing in the transverse direction can be adjusted so as to produce the required wave shape. The rollers 54 drive the wave shaped web 4 into a compression zone defined by upper and lower variable speed conveyors 56 and 58 so as to define the adjacent convolutions 8. The conveyors 56 and 58 are surrounded by an oven 60 which serves as a bonding oven to remelt the bonding fibres so as to form the bonded region 6, as shown in Figure 1, between adjacent convolutions 8 in

the insulating material 2. The temperature in the oven 60 heats the material to a temperature between 110°C and 180°C and preferably 145°C. The material so bonded is then conveyed to a cooling zone 62 which cools the material 2 below the melt point of the bonding fibre, i. e. below 110°C, so that the bonded regions 6 serve to maintain the web in its corrugated shape, as shown in Figure 1.

The insulating material 2 then passes to a cutting and packing stage 20 which includes a cutting station 64 for cutting the material 2 into its desired width and length.

The material then passes to a packing stage 66 for compressing the material into a form suitable for storage and packaging. Normally the material would be compressed in a longitudinal direction and placed in a plastic bag (not shown) for packing. Generally speaking, compression in a direction in the height or thickness direction of the insulating material 2 is undesirable because it could prevent the product from resiliently returning to its position having the predetermined height H. Compression is thus preferred in a direction normal to the planes of the convolutions 8.

Preliminary testing has demonstrated that the insulating material 2 has an R factor of 1 at a height H of 30-40mm when the density is approximately 15 to 20kg/m3. In Australia most ceiling batts are regulated at between R2.5 and R3.5 (referring to Australian R values).

Therefore, the approximate R factor relative to the height of the product is: R1=40mm R2=80mm R3=120mm R4=160mm Batts or webs of insulating material of the invention may be laminated prior to the packing stage 66 with a variety of laminates including foil if it were to be used for roof insulation where the foil would provide a reflective insulative surface that would primarily protect the insulation from moisture.

Figure 4A shows the web 4 laminated with upper and lower sheets 70 and 72 of laminating material such as a synthetic polymer film. The laminating material could be heat seamed at its edges in order to form a sealed envelope. The sheets 70 and 72 of laminating material are applied prior to passing to the corrugating/folding lapping stage 18.

This has the result that the laminating material extends between the adjacent convolutions.

The upper and lower laminating layer 70 and 72 could be in the form of an open weave scrim which generally serve to maintain the structural integrity of the web 4 and prevent fibres or particles of fibres falling away from the material. The open weave of the scrim enables the bonding fibres to hold the corrugations together because the melted bonding fibres will adhere to one another through the scrim. Alternatively, the layers may be in the form of plastic sheet metal such as polyethylene or the like and, after corrugation, the oven 60 causes partial melting of the layers 70 and 72 so that they adhere to each other and maintain the corrugated, folded or lapped shape, as shown in Figure 4B. Figures 4B and 4C show in more detail the modified laminated material 76.

Figures 5A and 5B show side views of a modified insulating product 80. In this arrangement a laminating sheet 82 is applied to the material 2 after corrugating and, before or after it has left the cutting station 64. The laminating sheet 82 may comprise a sheet of reflective aluminium foil which is bonded to the upper layer of corrugations, as shown.

Alternatively, the laminating layer 82 may comprise a coated metallic coil.

Figures 6A and 6B show side views of a further laminated product 86 which is generally the same as the product 80 except that it includes a lower laminating sheet 88 which may again be in the form of an aluminium foil or coated foil bonded to the lower side of the material.

Figures 7A and 7B show side views of a still further modified laminated product 90. The product 90 is similar to the product 80 except that it has a scrim 92 bonded to the lower side of the corrugated or folded material, as shown. The scrim 92 helps to maintain the structural integrity of the insulating material. In an alternative embodiment, the

laminating sheet 82 may be omitted and the scrim 92 bonded to the upper and lower sides of the insulating material. In a further modification, the scrim may be wrapped around and bonded to a body of the insulating material in order to maintain the shape thereof as an insulating batt. The scrim has a very open mesh and may be made from PET or cotton or the like.

The length and width of the batt of material 2 can be selected to be suitable for ceiling/wall construction in each market. Roof insulation is usually produced in blanket forms and on rolls, the length and width of which is a function of roof design.

In the illustrated arrangement, the fire retardant 29 is added in powder or liquid form to the cellulose fibre. It is possible, however, that the fire retardant may be separately applied in liquid form to one or more of the cellulose fibres, spring fibres and/or bonding fibres. Alternatively, the fire retardant material can be added, say in liquid form, prior to the web forming stage 44.

The insulating material of the invention can also be recycled because of the relatively high content of cellulose fibres, thus making it very environmentally friendly because it is initially made from recycled paper and then can be recycled again after its useful life.

Many modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention.