Patent GB-1474102-A (GB)
Title: Non-woven fabrics
IPC: D04H1/54
Filed: 1974-04-26
Abstract: 1474102 Embossing IMPERIAL CHEMICAL INDUSTRIES Ltd 11 April 1975 [26 April 1974 20 Sept 1974 7 Feb 1975] 18369/74 41066/74 and 5282/75 Heading B6J [Also in Division D1] A non-woven fabric comprising a web of fibres which includes distributed thermoplastic material has on each face patterns of bonded areas at least some of which in one face overlap bonded areas on the opposite face, the material of the web between opposed portions of bonded areas being depressed and formed into coherent bonds and the bonded areas on at least one face being discrete discontinuous areas distributed over this face, the fibres in the bonded areas being bonded by the thermoplastic material. The fabric may be produced as described in Specification 1,474,101 or by passing a web comprising or consisting of thermally bondable fibres through the nip between co-operating calender rolls at least one of which is heated and which have different surface land patterns, wherein some irregularity of land pattern is provided by the surface pattern or one roll consisting of continuous lands, i.e. lands which extend around substantially the full circumference or along substantially the full length of a roll, and the surface pattern on the other roll consisting of lands which are isolated projections and the centroids of area of those projections concurrently in the nip are disposed at differing distances from the longitudinal axis of the nearest continuous land surface so that lands which oppose each other in the nip overlap to differing extents. The continuous lands may be uniformly spaced circumferential circular rings (Figs, not shown), elliptical rings, helices or longitudinal splines. The 'isolated lands' are small points with flat or slightly domed tip surfaces and of square rectangular circular or other crossection of area a few tenths or hundredths of a square millimetre. A pattern of crossing broken lines is obtained by etching; an echelon pattern of rectangular lands is machined. If the spacing of the patterns on the two rolls is not the same the differing relative disposition of opposed land surfaces is achieved by selecting the size and disposition of the pattern of isolated lands. If the spacing is the same one pattern may be skewed relative to the other by 5 degrees. The land patterns of produced by skew angles of 2 degrees and 8 degrees between the echelon pattern and the circumferential lands pattern are also disclosed. Preferably the distances in the nip between each isolated land and the nearest continuous land varies from zero to half the continuous land spacing. Preferably both rolls are heated. Where the lands overlap compressed primary bonds are produced. Where a land does not overlap with a land on the other roll a weaker secondary land is produced. One or both rolls may be compliant and provided with a back up roll. Preferably the product of the land areas of the two rolls is between 2% and 20% and the ratio is less than 5 to 1. In example 1 freshly spun continuous nylon sheath /nylon 66 core in bicomponent filaments (35/65 sheath/core by weight) are drawn and sprayed by an air ejector onto a foraminous conveyor. The randomly laid web is calendered between a Fig 3 pattern roll and a roll having lands in the form of continuous longitudinal splines, both rolls being at 200‹C. The remaining examples are concerned with air laid staple fibre webs although corded and wet laid webs are also specified. In example 2 polyethylene terepthalate fibres having 3À5 crimps 1 cm are blended with an equal weight of polyethylene terephthalate core/is mole% ethylene isophthalate/terephthalate copolyester sheath, air laid, needled and calendered with the rolls of example. In example 3 the fibres are a blend of equal weights of wool fibres and staple fibres of of the same composition as the example 1 filaments. In example 4 the fibres are of nylon 6, and in example 5, a blend of nylon 6 and nylon 66 fibres.