Paper making and fiber liberation – Processes and products – Pore forming in situ
Patent
1997-01-15
1998-12-29
Chin, Peter
Paper making and fiber liberation
Processes and products
Pore forming in situ
162190, D21H 1300, D21H 2516
Patent
active
058535381
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of producing a nonwoven material by hydroentangling a fibre web, and to a nonwoven material produced according to the method.
BACKGROUND OF THE INVENTION
Hydroentangling or spunlacing is a technique which was introduced in the 1970's, see e.g. CA patent No. 841,938. The method involves forming a fibre web, either dry-laid or wet-laid, whereafter the fibres are entangled, i.e. tangled together by means of very fine water-jets under high pressure. A plurality of rows of water-jets are directed at the fibre web which is supported by a moving wire. The entangled fabric is then dried. The fibres which are used in the material can be constituted by staple fibres, e.g. polyester, rayon, nylon, polypropylene and the like, by cellulosic fibres or by mixtures of cellulosic and staple fibres. Spunlace material can be produced cheaply and presents high absorption characteristics. Amongst other things they are used as drying materials for households or industrial use and as disposable materials within the field of health-care etc.
Foam-forming techniques, i.e. where a fibre web is formed from a dispersion of fibres in a foamed liquid, are used today for the production of paper and other fibre-based nonwoven materials as well as for the production of glass-fibre mats for compression molding of various products for use within i.a. the car industry. The technique is described i.a. in GB 1.329,409 and U.S. Pat. No. 4,443,297. The thus-produced fibre webs present a high degree of uniformity in the fibre forming.
A method of forming a hydroentangled nonwoven fabric is disclosed in U.S. Pat. No. 5 106 457 in which a foamed fibre furnish is formed by dispersing fibres in a foamed liquid comprising water and a surface active agent, as described in U.S. Pat. No. 4 498 956, and thereafter subjecting the thus formed web to a hydroentanglement step.
OBJECT AND FEATURES OF THE INVENTION
An object of the present invention is to achieve a simplified method of producing a nonwoven material with high absorption characteristics, strength and uniformity.
This object is achieved by a method according to claim 1.
By this method, a flexible, space-saving and energy-economical process has been achieved, with which spunlace material of a surprisingly high quality can be produced.
DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to two embodiments shown in the accompanying drawings.
FIG. 1 is a flow diagram of the method according to the invention.
FIG. 2 shows a modified design of the dispersion vessel and the foam tank.
DESCRIPTION OF EMBODIMENTS
FIG. 1 shows a process solution for a foam forming process according to the invention. The foam is generated by means of a tenside being added to the water in a pulper 111 where an intensive agitation and air intake occurs. Additional foam generation occurs in the process due to the turbulence which is created in the pumps as well as at the wire 118. A condition for foam generation is however that there is access to air.
The tenside can be of any suitable type; anionic, cationic, non-ionic or amphoteric. GB patent 1,329,409 describes tensides suitable for foam forming of fibre webs. There are however many other available tensides suitable for the purpose. The choice of tenside can for example be affected by factors like the chemical composition of possible other additives to the fibre furnish, like wet-strengtheners, binders, creping chemicals, etc.
A suitable tenside metering in order to achieve a relatively stable foam which is able to maintain a substantially uniform dispersion of fibres in the foam is adjusted for each individual case and is dependent on such factors as the type of tenside, the degree of hardness of the water, the water temperature as well as the type of fibres. A suitable tenside content in the water lies within the range 0.02-1.0 weight-%, preferably however below 0.2 weight-%.
The characteristics of the foam vary with the amount of bound air. At an air con
REFERENCES:
patent: 4443297 (1984-04-01), Cheshire et al.
patent: 4488932 (1984-12-01), Eber et al.
patent: 4498956 (1985-02-01), Cheshire et al.
patent: 5102501 (1992-04-01), Eber et al.
patent: 5106457 (1992-04-01), Manning
Chin Peter
Leavitt Steven B.
SCA Hygiene Paper AB
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