Hydrophilic foams and processes for their manufacture

Details Hydrophilic foams and processes for their manufacture Hydrophilic foams and processes for their manufacture

1993-10-04

1994-08-09

Welsh, Maurice J.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

521 99, 521137, 521159, 521174, 521905, 528 59, 528 76, 528 77, 4283044, 4283193, 4284231, C08G 1830

Patent

active

053366956

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

The present invention relates to hydrogel foams, especially those for medicinal applications, and to processes for their manufacture.
Hydrogels are natural or synthetic macromolecular substances whose high content of hydrophilic groups makes them capable of binding water by absorption. The water absorption capacity of many hydrogels is several times the intrinsic weight of the anhydrous substance.
Hydrogels are used in a variety of forms in medicine. They are particularly suitable in the care of wounds; they can cells.
Hydrogels can be used inter alia in the form of foams.
Foams for the care of skin wounds or surgical wounds are known per se, the principal foams used in this case being polyurethane foams or collagen foams.
However, the hydrogels of the state of the art have various disadvantages:
Due to their hydrophilicity, most of the substances in question are water-soluble. This is usually undesirable because such products are not dimensionally stable. Moreover, such products dissolve in undesirable manner at the site of use and are then no longer available for the intended purpose.
Other products are distinguished by a high degree of polymer crosslinking. Although this avoids some of the disadvantages of the above-mentioned class of substances, the swelling capacity of these substances is substantially reduced or lost. Furthermore, all the synthetic crosslinking agents used here are more or less toxic.
Self-adhesive gel foams are also known per se. Although these can generally be bonded very well to the skin, most of them have the disadvantage that their water absorption and release capacity are greatly reduced.
European patent application A-0 097 846 describes wound treatment compositions based on hydrogels. Here, gelatin in solid form, as powder, flakes or sheet, is reacted in a two-phase reaction with crosslinking agents such as formaldehyde, glyoxal, glutaric acid dialdehyde, dicarboxylic acid chlorides and/or diisocyanates.
The crosslinking agent acts in this case on the swollen undissolved gelatin. This process and the products obtained therefrom suffer from considerable disadvantages because the crosslinking agents used can cause appreciable cell damage.
In addition, the process cannot easily be reproduced, if at all. The crosslinking depends not only on the concentration of the crosslinking agents used, but also on parameters such as temperature and reaction time of the reactants. Furthermore, the effective surface area and the average molecular weight of the commercially available types of gelatin are subject to marked variations, so it is also difficult to predict the properties of the crosslinked hydrogel.
European patent application A-0 097 846 further describes a composite material made of hydrogels based on polyvinyl alcohol. The crosslinking agent used is formaldehyde, which, as mentioned at the outset, is physiologically harmful.
Foams made of polyvinyl alcohol or collagen are also known and in common use. However, as their matrix substances have the disadvantages described above, their suitability for wound care is at best limited.
Furthermore, hydrophilic foams made of polyurethane gels are known. PCT patent application WO-88/01878 describes self-adhesive polyurethane foams and polyurethane foam gels which inter alia can contain methacrylates.
Polyurethane gels based on a polyurethane matrix and higher-molecular polyols are also described in European patent application B-0 057 839. Self-adhesive two-dimensional structures made of polyurethane gels are known from European patent application B-0 147 588. However, the polyurethane gels disclosed in these last two documents are anhydrous and unfoamed.
The object of the invention was therefore to develop hydrogel foams which do not have the disadvantages of the state of the art and are suitable as wound care compositions. Moreover, it should be possible to manufacture the foams economically by reproducible processes.
Surprisingly, it has been found that the disadvantages of the state of the art are mitigated by hydrophilic fo

REFERENCES:
patent: 3978855 (1976-09-01), McRae et al.

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