Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Hydroentangled nonwoven fabric
Patent
1997-10-14
2000-01-25
Copenheaver, Blaine
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Hydroentangled nonwoven fabric
162141, 162146, 162158, D21H 1100, D04H 146, D04H 148
Patent
active
060178337
DESCRIPTION:
BRIEF SUMMARY
This application claims priority to International Application No. PCT/SE96/00200, filed Feb. 15, 1996.
BACKGROUND OF THE INVENTION
The present invention relates to a nonwoven material produced by hydro-entanglement of a wet- or foam-formed fibre web.
Hydro-entanglement or spunlacing is a method which was introduced in the 1970s, see for example Canadian patent no. 841,938. The method involves forming either a dry-laid or wet-laid fibre web, whereafter the fibres are entangled by means of very fine water jets under high pressure. A plurality of rows of water jets are directed towards the fibre web which is carried on a moving wire. The entangled web is thereafter dried. Those fibres which are used in the material can be synthetic or regenerated staple fibres, e.g. polyester, polyamide, polypropylene, rayon and the like, pulp fibres or a mixture of pulp fibres and staple fibres. Spunlace material can be produced to a high quality at reasonable cost and display high absorption capability. They are used inter alia as wiping materials for household or industrial applications, as disposable materials within health care, etc.
The pulp fibres used in spunlace materials are mainly chemically exposed softwood pulp from different kinds of wood. The use of chemically exposed hardwood pulp and pulp produced from recycled fibres is also described in the literature, see EP-A-0,492,554.
Chemical pulp is produced by impregnating wood chips with chemicals and by subsequent boiling of the chips so that lignin, resins and hemicellulose are transferred to the boiling liquid. When the boiling is completed, the pulp is filtered and washed before it is bleached. The lignin content of such pulp is very close to zero and the fibres, which essentially consist of pure cellulose, are relatively long and slender. The fibres show a certain degree of flexibility, which is an advantage when the fibres are entangled by the hydro-entanglement process. Furthermore, the cellulose in the fibres form hydrogen bonds, which increases the strength of the finished material. A high degree of hydrogen bonding of the material does, however, impair the softness and decrease the bulk of the material.
SUMMARY OF THE INVENTION
The object of the present invention is to produce a spunlace material which presents improved absorption properties, softness and bulk. In accordance with the invention, this is accomplished with a material containing at least 5%, by weight of the total fibre weight, of wood pulp of chemical-thermomechanical type which has been mixed with other fibres, such as chemical pulp fibres, vegetable fibres, synthetic fibres or regenerated cellulosic fibres in a wet- or foam-formed fibre web which has been hydro-entangled with sufficient energy to produce a dense absorbent material.
The proportion of pulp fibres of chemical-thermomechanical type should be at least 5 and preferably at least 10% by weight of the total fibre weight. The material may additionally contain a wet strength agent or a binding agent. The invention is also directed to a method for producing the nonwoven material in question.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows in the form of a diagram the effect of the CTMP on the bulk and the total water absorption for some foam-formed spunlace materials.
DESCRIPTION OF THE INVENTION
The spunlace material according to the invention contains at least 5%, by weight of the total fibre weight, of pulp fibres of chemical-thermomechanical type.
Mechanical pulp is produced by grinding or refining and the principle for mechanical pulp production is to mechanically disintegrate the wood. All of the wood material is used and the lignin thus remains in the fibres, these being comparatively short and stiff. Production of thermomechanical pulp (TMP) is carried out by refining in a disc refiner at elevated steam pressure. Also in this instance the lignin remains in the fibres.
A thermomechanical pulp can be modified by addition of small amounts of chemicals, usually sulphite, which are added before the refining. Such pulp is
REFERENCES:
patent: 5607546 (1997-03-01), Hoglund et al.
"Hydroentanglement Technology Applied to Wet-formed and Other Precursor Webs", Tappi Journal, Jun. 1990, C.F. White, pp. 187-192.
Holm Ulf
Lammers Gerhard
Reiner Lennart
Copenheaver Blaine
Juska Cheryl
SCA Hygiene Paper AB
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