Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Patent
1995-09-15
1999-11-09
Clardy, S. Mark
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
424445, 428288, 428292, 428293, 428300, A61L 1500
Patent
active
059809302
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to improved absorbency alginate fibres, a process for their preparation and their application in the preparation of alginate fabrics and wound dressings.
Alginate fibres have been known for some time as being useful in the preparation of wound dressings. A number of methods for producing conventional alginate fibres are described in the art. The extrusion of alginate solutions into an aqueous solution containing calcium ions to form calcium alginate filaments is known, for example, from British Patent Specifications Nos. 567641, 568177, 571657 and 624987. The replacement of a proportion of the calcium ions in calcium alginate by sodium ions to produce a more soluble fibre is known from British Patent Specification No. 653341.
A fabric prepared from known calcium alginate fibres can typically absorb 3 to 5 times its own weight of water, and this absorbency can be increased by increasing the proportion of sodium ions to calcium ions in the fabric. In this way, fabrics having an absorbency of approximately 20 times their own-weight of water have been produced, for example, Kaltostat (trademark), a haemostatic wound dressing comprising a carded and needle-tacked web of calcium/sodium alginate fibres. Other factors which affect absorbency of alginate fibres are the nature of the source material and staple length.
We have now found that alginate fibres can be produced which are very much more absorbent than conventional alginate fibres. This is a considerable advantage for use in environments where high absorption coupled with biodegradeability is desired, for example in wound dressings such as dressings for ulcers or burns. The high rate of absorption achieved with fibres of this invention is a further advantage, particularly for use in dressings.
The fibres according to the invention may be characterised by reference to their unique thermal properties.
The present invention thus provides an alginate fibre characterised in that a plot of the first order derivative of percentage weight loss of the fibre with temperature against temperature has two maxima in the range of 100 to 400.degree. C.
In general, the two maxima in the plot of the first order derivative of percentage weight loss with temperature against temperature for a fibre according to the invention will fall within the range 200 to 300.degree. C., preferably 220 to 290.degree. C.
FIG. 1 shows the thermogravimetric analysis (TGA) of an 80:20 calcium:sodium alginate fibre prepared by conventional methods.
FIG. 2 shows the thermogravimetric analysis (TGA) of a fibre according to the invention, prepared from the same source material as the fibre of FIG. 1.
FIG. 3 shows the variation of heat flow with temperature for a conventional 80:20 calcium:sodium alginate fibre and a corresponding fibre in accordance with the present invention.
FIG. 4 shows the thermogravimetric analysis of a conventional fibre, a high absorbency fibre according to this invention and such a fibre treated with calcium ions.
FIG. 5 shows apparatus suitable for determining absorbency.
Thermogravimetric analysis was performed using a 2950TGA manufactured by TA Instruments, Delaware, U.S.A. Differential scanning calorimetry (DSC) was performed using a DSC7 manufactured by Perkin-Elmer.
FIG. 1 shows the percentage weight loss of a conventional alginate fibre with increasing temperature, and the first order derivative of that function. The derivative shows a single maximum at approximately 240.degree. C. In contrast, the first order derivative of percentage weight loss with temperature for a corresponding fibre according to the present invention, shown in FIG. 2, has two peaks, one at a lower temperature than the maximum observed for the conventional fibre (approximately 225.degree. C.), and one at a higher temperature than the maximum observed for the conventional fibre (approximately 280.degree. C.). This "splitting" of the derivative maximum for the conventional fibre of the same composition is characteristic of fibres according to the present invention.
FIG
REFERENCES:
patent: 1814981 (1931-07-01), Thornley et al.
patent: 4421583 (1983-12-01), Aldred et al.
patent: 4562110 (1985-12-01), Tong
patent: 5238685 (1993-08-01), Wren
patent: 5256477 (1993-10-01), Mahoney
Database WPI, Section Ch, Week 8705, Derwent Publications Ltd., London, Agency of Ind Sci Tech et al., Dec. 19, 1986; AN 87-033299.
Fenton John Charles
Griffiths Bryan
Mahoney Peter Michael John
Bristol--Myers Squibb Company
Clardy S. Mark
Furman Jr. Theodore R.
Kilcoyne John M.
Shelborne Kathryne E.
LandOfFree
Fibres does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fibres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fibres will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1452102