An air-laid non-woven fibre product comprising fibres of recycled material

All patent and non-patent references cited in the present application are also hereby incorporated by reference in their entirety.

The present invention relates to air-laid non-woven fibre product manufactured by a dry forming process and a method of manufacturing such product.

From US-A-5, 516,580 an insulation batt is known, where the material contains a portion of cellulose fibres, and longer bonding synthetic fibres. These synthetic fibres are so-called bi-component fibres that have an outer sheath which is heat-fused with outer sheaths of other synthetic fibres at crossing contact points thereof to form a matrix having pockets for retaining loose fill cellulose fibres therein. This matrix eliminates the need of an adhesive binder to retain the cellulose fibres in the matrix.

The drawback of this insulation board is that the fibre batt obtained hereby is not particularly resilient and the use of longer bi-component synthetic bonding fibres makes the product very expensive to manufacture.

A method of making a resilient mat is known from US-A-5, 554, 238. The insulation mat according to this method comprises cellulosic and thermoplastic fibres. A mat is formed in an air-laying process and subsequently the surface is flame-treated to melt the thermoplastic component on the surface forming a skin which keeps the cellulosic fibres intact. The thermoplastic fibres in the interior of the mat remains unmelted, whereby the mat is provided with a spring-back characteristic, which allows the mat to retain most of its original shape after it has been compressed, e.g. for shipping.

However, this resilient mat has a "crisp" exterior surface reducing the resiliency of the mat as a whole and not homogeneously bonded throughout the product, which does not allow for easy handling since the product may easily delaminate or otherwise break up. The insulation effect is moreover reduced due to the more compact structure of the fibre product.

From WO 01/48330 a recyclable insulating mat comprising shredded waste paper or cardboard mixed with natural fibres and 5-50 % polyester is known.

In DE 196 02 551 C1 , there is described a mat for manufacturing self-supporting form parts by heat treatment. The mat comprises long natural fibres and thermoplastic binding means provided as synthetic fibres. The thermoplastic binding means are provided synthetic material with a high melting point and a low melting point.

It is an object of the present invention to provide a resilient fibrous product which is recyclable and inexpensive to manufacture from waste material.

This object is achieved by an air-laid non-woven fibre product manufactured by a dry forming process, said product comprising a first portion of up to 98 % recycled shredded material, where the shredded material is a mixture of shredded fabric textile material fibres from automotive tires or the like and residues of rubber and other components from the shredded tires, and a second portion of 1 - 30 %, preferably 1 - 5 %, bi-component fibres having a length between 2 - 50 mm.

According to a second aspect of the invention, there is provided a method of manufacturing a non-woven product by dry forming a product of fibrous material, said method comprising the steps of advancing fibrous material into a forming box having a bottom outlet positioned over a forming wire to form a web of dry-laid fibres on the forming wire, where said fibrous material comprises a first portion of up to 98 % recycled shredded material, where the shredded material is a mixture of shredded fabric material fibres from automotive tires or the like and residues of rubber and other components from the shredded tires, and a second portion of 1 - 30 %, preferably 1 - 5 %, bi-component fibres with a length between 2 - 50 mm and comprising a core and an outer sheathing, said outer sheathing having a first melting temperature which is lower than the second melting temperature of the core; heating the web of fibres formed on the forming wire to a temperature above the first melting temperature; and advancing the fibrous web through a pressing section whereby a fibrous product web with a predetermined density is formed.

According to the invention, an air-laid fibrous product is obtained based on recycled fibres from waste material from recycled tires. These tires are among the largest and most problematic sources of waste, due to the large volume produced and their durability. Those same characteristics which make waste tires such a problem also

make them one of the most re-used waste materials, as the rubber is very resilient and can be reused in other products. Thus, the rubber of the scrap tires may be recycled, but by the present invention, it is realised that also the other material components of the scrap tires may be recycled.

When a scrap tire is to be recycled, the tires are shredded and the rubber components are separated from the rest of the waste material and collected for reuse in other products. However, the remaining waste material comprising shredded textile material cannot be recycled. This waste tires textile material also contains residues of rubber and metal wires.

By the invention, it is realised that the shredded tires fabric material can be recycled in an advantageous manner by utilising this material in an air-laid fibre mat which is obtainable by using the manufacturing technology disclosed in WO2005/044529. The fibre mat product according to the invention is furthermore advantageous since the product is water repellent and provided with resilience whereby the mat raises again after compression and resumes its original shape.

This advantageous characteristic of the product according to the invention is also achieved by the use of short bi-component fibres so that the resulting fibrous mat is very flexible as the short bi-component fibres acting as binding means in the product are short. The bi-co fibres become hard when cured after having been heated above the melt temperature, so by using short bi-co fibres the bi-co fibres do not adversely affect the resulting product with respect to flexibility and elastic properties when cured due to their short length.

Moreover, it is realised by the invention that the short bi-component fibres mix better with the recycled fibres whereby a substantially small proportion of bi-co fibres are needed to provide sufficient coherence of the product. This further enhances the flexibility of the fibrous product.

In a preferred composition of the fibre product, 80-90 % recycled shredded tire material fibres are used together with 10-20 % bonding fibres. The bonding fibres are bi- component fibres substituted or supplemented with polyester fibres, polypropylene and/or other plastic fibres having bonding characteristics.

The product according to the invention is found particularly advantageous since it is flexible and whether and water resistant and may thereby substitute e.g. foam sheets in the building industry. Other useful purposes may be vibration or noise damping, e.g. of wooden floors, use in noise screens in road constructions, etc.

Preferably, the fibre length of the shredded material in the first portion is 1 -100 mm, and the grammar weight of the air-laid product according to the invention is between 20 kg/m ³ and 200 kg/m ³ .

In an embodiment of the invention, addition fibres, such as recycled glass fibres, carbon fibres or the like, may be added to the first portion.

In a preferred embodiment of the invention, at least 50 % of the bi-component fibres are crimped fibres with a length between 2 to 50 mm. By using short and crimped fibres, e.g. of a helical shape extra flexibility and resilience is achieved in the product allowing the product to appear softer and having good properties with respect to raising again after compression and resuming its original shape.

In a preferred embodiment, the fibres are provided with fire-retarding chemical, such as Borax, Boric acid, Ammonium sulphate or aluminium sulphate, mixed with the fibres, e.g. in the forming box before being laid on the forming wire. In another embodiment, the dry-formed fibre mat may be sprayed with fire-retarding chemical, e.g. after the mat is formed and heated.

If extra bonding of the fibres is required, an additional fluidized binder may be sprayed into the forming box and onto the fibres therein. The fluidized binder may alternatively be sprayed onto the fibres. As a further alternative or as a supplement, binder in pulverised form may be mixed with the fibres before the mixture is forwarded to the forming box.

The invention is further explained with reference to the accompanying drawing which shows a diagram of an embodiment of the manufacturing process for producing a product according to the invention.

Waste material from shredded tires mainly consisting of tire fabric shredded into fibres in a length below 100 mm. Although mainly consisting of fabric from the tires, the shredded waste fibres also contain residues of rubber and some pieces of metal wire which have not been recovered from the shredded tire material for immediate reuse.

This shredded fabric fibre material including residue material constitutes a first fibre portion which is mixed with bi-component fibres. These bi-component fibres comprise a core and an outer sheathing, said outer sheathing having a first melting temperature which is lower than the second melting temperature of the core. The purpose these bi- component fibres serve is to provide bonding between the fibres in the first portion of fibres. The bi-component fibres become hard when cured after having been heated above the melt temperature, so by using short bi-co fibres the bi-co fibres do not adversely affect the resulting product with respect to flexibility and elastic properties when cured due to their short length. Moreover, the short bi-component fibres blend very well with the fibres of the first portion ensuring a more homogeneous bonding throughout the product.

The mixture of fibres are forwarded to a forming box, preferably of the kind described in WO2005/044529, where the box is provided with a revolving belt screen allowing for an even distribution of fibres irrespective of their size.

The fibres are introduced into the forming box and laid on the forming wire beneath the forming box. The web of fibres is forwarded in a continuous motion through a heating station where the bi-component fibres are activated and the fibrous web is provided with its coherence.

The web is then cured as the heated bi-component fibres are cooled and the web may be forwarded through a pressing station for providing the resulting mat product with a predetermined density.

The fibrous web may be sprayed with a fire-retarding substance, such as Borax, Boric acid, Ammonium sulphate or aluminium sulphate, for providing the product with fire- retarding properties. Alternative to spraying the formed web, this substance could also be sprayed into the forming box and thereby priming the fibres before the fibres are laid onto the forming wire.

Example:

Example I:

A material for forming an insulation fibre mat is mixed by provided the following components:

90 % shredded scrap tire fabric fibres of recycled tires. 10 % bi-component fibres of approx. 6 mm length having a coated polyester core.

The fibres are laid by the forming box and heated to a temperature of 130 ⁹ C and then primed with a fire retardant.

Hereby, a cost effective fibre product having a grammar weight of 20-200 kg/m ³ is provided, which has a good spring elastic effect and insulation properties.

By the present invention, it is realised that the variations of the above-mentioned example may be performed without departing from the scope of the invention as defined in the accompanying claims.