Regenerated cellulose sponge

#This invention relates to the production of artificial sponges and more specifically to artificial sponges adapted for use in surgical procedures and as topical wound dressings, feminine hygiene devices, for industrial purposes such as filters and desiccants and the like.

#The sponges of this invention are based upon the well known artificial sponges comprising regenerated cellulose. As is well known the regenerated cellulose sponges are formed from a mixture of viscose, reinforcing fibers such as linen, jute, cotton, regenerated cellulose fibers and the like, and a pore forming constituent, generally crystals of sodium sulfate decahydrate or other alkali metal salt high in water of crystallization such as sodium acetate trihydrate, sodium carbonate decahydrate, trisodium phosphate dodecahydrate, disodium phosphate dodecahydrate, potassium sodium tartrate tetrahydrate and the like. In general, the viscous solution of viscose contains from 5 to 8% cellulose, 6 to 100% fibers, based on the cellulose, as reinforcing means and 900 to 2500% of the inorganic pore forming salt, based on the cellulose. The final pore size will be dependent upon the size of the pore forming inorganic salt crystals. The mixture is then introduced into desired molds or extruded through desired shaped orifices and the cellulosic solution coagulated and regenerated. After regeneration, the shaped mass is subjected to washing with water to remove the soluble salt and other constituents, desulphurized, bleached and, in general, finally treated with a solution of a plasticizer such as glycerol or propylene glycol. In view of the fact that the production of this type of artificial sponge is well known, it is deemed unnecessary to describe in further detail the production of such product.

#There are at present several so-called surgical sponges which are utilized in various surgical procedures to absorb blood and body fluids. One of such devices formed of a polyurethane foam for use in ophthalmological surgical procedures is cut to a small spear-like shape from a sheet of the foam. Its principal disadvantage is the low rate of absorption of body fluids and blood and a relatively low liquid absorption characteristic. One of the advantages, however, is that in use this type of sponge is relatively free of lint along its surfaces. One type of surgical sponge of the common regenerated cellulose type is apparently formed by a thorough washing of regenerated cellulose sponge material to remove all soluble material including the plasticizer and after drying, compressing the sponge and cutting it to the desired size and shape, such as, a small spear-like or triangular shape. The spear type consists of a sponge head, triangular in shape about 3/4 inch long, about 3/8 inch at its base, tapering to a rather fine point having a thickness of about 1/16 to 1/8 inch and having a molded plastic or wood handle secured to the base. These types of sponges absorb fluids including blood rapidly and have an appreciably higher absorbence than does the polyurethane type sponge. The principal disadvantage in the use of these types of sponges is that in the course of the cutting operation lint fragments are formed and, subsequently upon wetting, lint particles develop along the surfaces of the sponge. When used as in eye or ear surgery and in other surgical procedures and medical uses very fine particles of this lint frequently become dislodged and remain at the site of the sponge and thereby deposit at that site undesired foreign material (cellulose) which may not be visible to the naked eye.

#Further objects and advantages of the invention will become apparent from the description which follows considered in conjunction with the drawing which is a graph illustrating the critical relationship between the liquid ab sorption properties of the sponges and the polymer concentration of the impregnating solutions or dispersions.

#The patent to Orlando A. Battista, U.S. Pat. No. 3,649,347, discloses structures having a self-adherent coating of a water-insoluble, water-dispersible, high molecular weight, hydrophylic, film-forming polymer, specifically, a water-insoluble, ionizable, partial acid salt of collagen having a bound ionizable acid content of from about 50 to about 90% of the stoichiometric bound acid content (microcystalline collagen). Regenerated cellulose sponges were prepared in accordance with the disclosure of this patent.

#Sheets of commercially available white regenerated cellulose sponge of medium pore size (pores approximately 0.5 mm. to 3.5 mm.), compressed as received from a supplier, were immersed in water to thoroughly saturate the sponge sheets. The saturated sheets were washed with water so as to remove any soluble constituents. Each washed, water saturated sheet was then placed between sheets of aluminum foil and passed between rubber rollers of a hand wringer with its springs set at 3 inches so as to remove excess water. The sheets were then oven dried in a circulating air oven at a temperature of 75.degree. C. for 90 minutes. The dried sponge sheets had an average thickness of approximately 7.5 mm. The dried sponge sheets were conditioned by maintaining them in the ambient atmosphere for 6 hours at a temperature of about 73.degree. F. and a relative humidity of about 50%. The sponge sheets were subsequently compressed to an average thickness of approximately 1.2 mm. by pressing at about 24,000 psi in a Carver Press.

#Triangular samples, designated as Samples A in Table 1, were cut with a scalpel from one of such compressed sponge sheets. The samples were approximately 3/4 inch in length, about 3/8 inch at the base and tapered to a point.