Paper making and fiber liberation – Processes and products – Synthetic fiber
Patent
1995-11-30
1998-07-14
Czaja, Donald E.
Paper making and fiber liberation
Processes and products
Synthetic fiber
162 9, 162182, 811551, 81161, D21H 1120, D21H 1706, A61L 1516
Patent
active
057798575
DESCRIPTION:
BRIEF SUMMARY
This application is a national stage application under 35 U.S.CX. 371 of International Application Number PCT/SE94/00613, filed Jun. 21, 1994.
TECHNICAL FIELD
The present invention relates to a defibrated cellulose product, in particular fluff pulp, containing crosslinked cellulose fibres. The invention also relates to an absorptive body which consists, at least in part, of the said cellulose product, and also to a method for preparing a cellulose pad, in particular fluff pulp, which method includes defibration, i.e. individualizing the cellulose fibres with mechanical devices and crosslinking them.
STATE OF THE ART
There has for many years been an interest in chemically crosslinked fluff pulp and it has been proposed that this pulp should be used in absorbent hygiene products. This proposal has been based, in particular, on the favourable properties of the crosslinked cellulose, particularly as regards absorption capacity, wet specific volume and absorption rate, which properties are particularly important when producing absorbent hygiene products such as nappies (diapers), sanitary towels, etc.
In U.S. Pat. No. 3,224,926 (1965), Bernadin has described the use of formaldehyde for crosslinking cellulose in the dry and defibrated condition. In addition, the use of other crosslinking reagents has been proposed by, inter alia, Schoggen et al., U.S. Pat. No. 879,678 (1986) (bifunctional aldehydes); Herron, Cooper, U.S. Pat. No. 432,648 (1989) (polyfunctional carboxylic acids); and Norlander, International Patent Application PCT/SE93/00086 (derivatives of dihydroxyethyleneurea). Defibrated cellulose, i.e. individualized cellulose fibres, for example fluff pulp, which is produced in accordance with these methods exhibits a consistent improvement in absorption capacity, wet specific volume and absorption rate.
In addition, PA Graef, WO 88/04704, has reported that a cellulose product produced by treating cellulose with polyfunctional aldehydes, as cellulose crosslinking agents, in the presence of ethylene glycols, propylene glycols or polyether glycols possesses improved absorption properties, principally absorption rate. The crosslinking reaction, if such a reaction takes place, is carried out in a conventional drying machine with the cellulose fibres being in sheet-form, i.e. in the presence of fibre-to-fibre bonds and at temperatures which must not exceed 100.degree. C. The dry matter content associated with any crosslinking reaction which is carried out is stated to be 1-20 %, ie. the fibres are partially swollen by water. Sheet-fibrating is carried out in subsequent stages in a conventional manner in the dry state prior to shaping the absorptive bodies, which are designed to be used in babies' nappies, feminine products, etc. The increase in absorption capacity as compared with completely untreated fibres is reported to amount to approximately 15%.
A cellulose product having exposed, dry-crosslinked fibres is normally characterized by a high degree of resilience in the dry state, signifying that high pressures and high temperatures are required in order to compress the product to high densities, for example greater than 0.20-1.0 g/cm3. According to Sultze, PCT/US92/01668, pressures of between 800 and 115,000 psi (55-7930 bar) and temperatures of between 60.degree. C. and 180.degree. C. are needed in order to achieve this. For several reasons, the high degree of resilience represents a disadvantage. For instance, powerful, and consequently expensive, tools are required for compressing to high density.
BRIEF DISCLOSURE OF THE INVENTION
The object of the present invention is to make available a defibrated cellulose product of the type specified in the introduction, which product possesses a fibre structure having an improved, preferably controllable, compressibility. More particularly, the object of the invention is to make available a cellulose product for use in absorbent products, more particularly in absorbing pads designed to collect body fluids, for example those products which include babies' nap
REFERENCES:
patent: 3224926 (1965-12-01), Bernardin
patent: 3434918 (1969-03-01), Bernardin
patent: 4853086 (1989-08-01), Graef
patent: 4888093 (1989-12-01), Dean et al.
patent: 4889595 (1989-12-01), Herron et al.
patent: 4889596 (1989-12-01), Schoggen et al.
patent: 5009650 (1991-04-01), Bernardin
patent: 5124197 (1992-06-01), Bernardin et al.
patent: 5366591 (1994-11-01), Jewell
patent: 5384012 (1995-01-01), Hazard, Jr.
Czaja Donald E.
Fortuna Jose S.
Stora Kopparbergs Bergslags Aktiebolaf
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