U.S. Pat.  No.  5,674,524 describes and claims an alginate dressing which is needle punched onto a non-alginate backing web so that fibres from the alginate layer penetrate into and are interlocked with the backing web.  In the fabric described in that specification there is clearly a backing layer on one side of the product which is a non-alginate layer and an alginate dressing on the front side of the product.  All of the description is concerned with the penetration of the alginate fibres into the backing layer to produce a continuous product.  In column 5, lines 25 to 32, it is specified that a particular advantage of the alginate dressing containing a backing is the ease with which an adhesive strip can be placed on the backing and hold the alginate dressing in place.  Because alginate becomes hydrocolloidal, i.e. gels, in an exudating wound the adhesive strip would become moist and easily disassociated from the alginate dressing should the alginate material have penetrated the backing.  Thus, the US patent is clearly directed to a two-layer structure in which the backing does not have alginate on its exterior. 
WO-A-99/67456 describes the formation of a three-layer structure for a fabric composite comprising two outer gel-forming fibre layers which sandwich a central core or reinforcing layer.  The three-layer structure is produced by needling first and second webs of gel-forming fibre to a textile fibre scrim so as to produce a fabric with the gel-forming fibres on both sides.  As described in Example 2 of WO-A-99/67456, the fabric composite can be made by laying up cross-laid, carded and needled webs of a gelling fibre such as carboxymethyl cellulose on either side of a spun-bonded fabric, typically a polypropylene fabric.  The assembly is then needled together to produce the fabric. 
GB-A-1,394,742 discloses surgical dressing material comprising a layer of knitted alginic material adhered to one side of a layer of flexible backing material by damping followed by drying. 
WO-A-90/01954 discloses a wound dressing comprising a wound contact pad of a mixed salt alginate and a backing layer which may be bonded to the wound contact pad by adhesive. 
U.S. Pat.  No.  5,340,363 discloses a wound dressing comprising as wound-contacting surface a porous hydrophobic layer composed of an elastic net-like porous reinforcing component substantially completely encapsulated by a soft and elastic hydrophobic gel such as silicone gel whilst retaining the porosity of the net-like reinforcing component, so that the layer includes openings which permit wound exudate to pass through the hydrophobic layer to be absorbed in an outer absorbent layer attached to the hydrophobic layer. 
U.S. Pat.  No.  5,489,262 discloses a wound dressing containing a hydrogel material in a gel-like phase adhesively bonded to a support layer which is adhesively bonded to a backing layer. 
WO-A-96/13282 discloses a wound dressing comprising a wound-contacting layer having a positive effect on the healing of the wound, for example an alginate layer, and a second layer of greater hydrophilicity than the first layer, for example an alginate or carboxymethyl cellulose layer.