US2627341A - Aseptic package with steam permeable seal - Google Patents

Description

ASEZPTIC PACKAGE WITH STEAM PERMEABLE SEAL Filed Aug; 19, 1949 INVENTOR fia/Pm/v 0. 4/0 44 ATTO R N EY Patented Feb. 3, 1953 UNITED STATES PATENT OFFICE ASEPTIC PACKAGE WITH STEAM PERMEABLE SEAL Burton D. Morgan, Fords, N. J., assignor to Johnson & Johnson, a corporation of New Jersey 5 Claims.

This invention is directed to package unitsthat can be sterilized under heat so as to minimize danger of distortion or rupture during sterilization thereof. In one of its more specific aspects the invention is directed to novel methods and processes for sterilizing aseptic units such as surgical dressings under heat, steam and pressure.

In the art of handling aseptic materials and especially surgical dressings it has been found necessary to employ sealed envelope-type containers therefor to maintain the aseptic materials in proper physical and sterile condition. These containers are generally throw-away containers ordinarily composed of a material of sufficient density to prevent passage of microorganisms such as bacteria, but of sufiicient steam permeability, particularly at elevated temperatures, to permit penetration of steam into the container under conditions of steam sterilization. Paper is preferred, particularly sulfite Wrapper stock or glassine, either having a basic weight of from about fifteen to about forty pounds per ream of five hundred sheets measuring twenty-four by thirty-six inches and of a thickness of from about one to about four mils.

Containers of this type may be manufactured readily, dressings and other materials may be inserted therein with ease, and the containers may be sealed at high production speeds in any of the several manners known in the art. The main disadvantage under production conditions of such containers, is the weakness of their walls which are relatively thin and may be torn readily.

Particularly is this true as the sealed containers are placed in sterilizing chambers and heated to temperatures in the range of from about two hundred twenty to about two hundred sixty degrees Fahrenheit. The containers become distorted and rupture at times because the pres sure exerted at said elevated temperatures by the air in the sealed containers is frequently much greater than the pressure in the chambers surrounding the container particularly if vacuum is used in the process as is usual. Elevated ternperatures of the above indicated range are necessary and usual for satisfactory steam sterilization. The adhesive coatings necessary to bond the container walls for secure sealing of the containers due to their imperviousness add to the impermeability of the containers and in addition to increasing the tendency of the containers to burst, in some cases also decrease the steam penetration to a point where poor sterilization occurs.

It is an object of this invention to provide a container for packaging securely aseptic materials. Further objects of the invention are the provision of methods and containers for enclosing surgical dressings and the like wherein bursting under conditions of heat sterilization is minimized, and which are adapted to speedy and economical production methods.

Still further objects will be apparent from the following description of the invention which provides a container enclosing the aseptic material and having walls of sufiicient density to prevent passage of microorganisms such as bacteria, but of suflicient permeability, particularly at elevated temperatures, to permit penetration of steam into the container under sterilizing conditions, the insides of which walls are coated by a layer of discrete dots of heat sealing material. It is surprising to note that containers of this type may be sealed securely so as to prevent contamination after sterilization but retain sufficient porosity to permit passage of air from the container as the air within expands with rising temperature, thus preventing rupture of the container as sterilization proceeds.

Further details of the invention will be readily apparent from the following description and drawing wherein:

Fig. 1 is a plan view of a container holding an adhesive bandage with the top wall partially removed and illustrates the type of package that may be sterilized by practicing the present invention;

Fig. 2 is a vertical section through line 2-2 of g- Fig. 3 is a plan view of one of the two walls of the container illustrating a typical pattern of the adhesive coating on the container wall.

The drawing illustrates one example of a product that may be sterilized readily in accordance with this invention and in this instance, there is provided a container comprising a bottom wall 5! and a top wall l2. Between these two walls, a dressing or other aseptic material such as an adhesive bandage it is positioned. One of the walls or both may be coated with an adhesive coating 13 which is applied in the form of minute, discrete dots I4, e. g. in the form of rotogravure printing and by a rotogravure printing process. The exact sires of the individual dots of the coating and the intervals between these dots may be varied but it is noted for best results, particularly with papers of the glassine or sulfite wrapper stock type, the intervals between dots are preferably in the range of from about one tenth to about four ttnths of a millimeter and the diameters of the dots are preferably in the range of from about two-tenths to about seven-tenths of a millimeter. In preferred embodiments of the invention the combined areas of the dots amount to from about twenty to about fifty per cent of the total area wherein the coating is applied. The adhesive coating may be any conventional heat sealing adhesive coating, preferably one that is nontacky at normal room temperatures, but those adhesive coatings that are based on vinyl halide copolymers, vinyl ester and ether polymers and cellulose esters and ethers are preferred.

The container walls H and I2 are sealed after insertion of the aseptic article at marginal portions I5-l8 so as to enclose the article completely. After this sealing steam sterilization may be resorted to in the usual manner, substantially without bursting of containers. After sterilization the containers continue to enclose the aseptic materials securely and prevent access of bacteria and other microorganisms thereto.

In preferred embodiments the margins I5- l3 of the container around the aseptic unit In may be embossed as illustrated in Figs. 1 and 2 during or before sealing so as to insure better contact for the adhesive with both container walls at these sections. i

In order to illustrate the invention in even more detail and to simplify its understanding but I not to limit its scope two specific embodiments of the invention follow:

Example I Two mil white sulfite wrapper stock having a basis weight of twenty-six pounds is coated with an adhesive composition of the following formula:

Vinyl chloride acetate copolymer (ball and ring methochsoftening point 266 F.)

87% vinyl chloride "1f 50 13% vinyl acetate Vinyl chloride acetate interpolymers (ball and ring method, softening point 270 F.)

86% vinyl chloride 13% vinyl acetate "i 50 1% maleic acid The coating is arranged so as to produce heatsealing dots having average dimensions of 0.475 millimeter, the average space between dots amounting to 0.300 millimeter. The arrangement is systematic and fairly regular so that there are no dots varying fifty per cent in either of these dimensions. The surgical dressing is placed upon a strip made from the above described coated sheet in the manner shown in the drawing and a second similarly coated strip is laid over the surgical dressing. The package is then sealed as illustrated in Fig. 1. The product undergoes sterilization without difficulty or rupture of the package and remains sterile throughout several months storage up to the point of use when the package is opened by the user.

Example I] and having a basis weight of twenty-five pounds and the adhesive has the formula:

Parts by weight Cellulose nitrate '70 Plasticizer 30 The preferred cellulose nitrate has a viscosity of 50 centipoises resulting in a solution comprising 12.2 per cent cellulose nitrate, 22 per cent ethyl alcohol, 17.5 per cent ethyl acetate, and 48.3 per cent toluene. Any plasticizer for cellulose nitrate (although tricresyl phosphate is preferred in this particular formula) may be used.

In this case the dots of the coating have average diameters of 0.520 millimeter and the average space between dots is approximately 0.350 millimeter.

No difiiculties were experienced during sterilization and containers formed appeared to be well stabilized and retained their stability for some time.

It is, of course, realized that wide variations may be made within the broad concepts stated earlier and satisfactory results are obtained if the examples are varied in accordance with the spirit of the invention. The development has proven of great economy in the manufacture, sterilization, storage, sale, and use of surgical dressings and provides a sterile sealed surgical dressing at very low cost and with assurance of sterility.

Many other variation of the invention illustrated and described herein will be apparent to those skilled in the art and are included in the inventive concept.

What is claimed is: V

1. An aseptic package comprising two sheet portions of material of sufficient density to prevent passage of microorganisms but of sufiicient steam permeability to permit passage of steam under heat sterilizing conditions, said sheet portions being disposed in face-to-face contacting relation and sealed to each other around the entire edge of said package to prevent entry of microorganisms into said package, aseptic material enclosed between said sheet portions near the center of said package, a substantial part of said edge seal being formed by densely spaced discrete dots of heat-sealing adhesive material joining together said edge portions of said sheet material to permit escape of gases from within said package during steam sterilization without rupture of said sheets.

2. A substantially flat aseptic package comprising two sheet portions of material of sufficient density to prevent passage of microorganisms but of sufficient steam permeability to permit passage of steam under heat sterilizing conditions, said sheet portions being disposed in faceto-face contacting relation and sealed to each other around the entire edge of said package to prevent entry of microorganisms into said package, aseptic material enclosed between said sheet portions near the center of said package, a major part of said edge seal being formed by densely, regularly spaced discrete dots of heat-sealing adhesive material joining together said edge portions of said sheet material to permit escape of gases from within said package during steam sterilization without rupture of said sheets.

3. A substantially fiat aseptic package comprising two sheets of material of sufiicient density to prevent passage of microorganisms but of sumcient steam permeability to permit passage of steam under heat sterilizing conditions, said sheets being disposed in face-to-face contacting relation and sealed to each other around the entire edge of said package to prevent entry of microorganisms into said package, aseptic material enclosed between said sheets near the center of said package, said edge seal being formed throughout by densely, regularly spaced discrete dots of heat-sealing adhesive material, non-tacky at normal room temperature, joining together said edge portions of said sheet material to permit escape of gases from within said package during steam sterilization without rupture of said sheets.

4. A substantially flat aseptic package co..- prising two sheets of white sulfite wrapper paper stock of sufficient density to prevent passage of microorganisms but of sufiicient steam permeability to permit passage of steam under heat sterilizing conditions, said sheets being disposed in face-to-face contacting relation and sealed to each other around the entire edge of said package to prevent entry of microorganisms into said package, aseptic material enclosed between said sheets near the center of said package, said edge seal being formed throughout by densely, regularly spaced discrete dots of heat-sealing adhesive material, non-tacky at normal room temperature, joining together said edge portions of said sheet material to permit escape of gases from within said package during steam sterilization without rupture of said sheets, said dots occupying from about twenty to about fifty per cent of the sealed area of said edge.

5. A substantially flat aseptic package comprising two sheet portions of glassine paper of suflicient density to prevent passage of microorganisms but of sufficient steam permeability to permit passage of steam under heat sterilizing conditions, said sheet portions being disposed in faee-to-face contacting relation and sealed to each other around the entire edge of said package to prevent entry of microorganisms into said package, aseptic material enclosed between said sheet portions near the center of said package, a major part of said edge seal being formed by densely, regularly spaced discrete dots of heatsealing adhesive material joining together said edge portions of said sheet material to permit escape of gases from within said package during steam sterilization without rupture of said sheets.

BURTON D. MORGAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,387,839 Davis Aug. 16, 1921 1,992,215 Kellet Feb. 26, 1935 2,249,424 Hanington July 15, 1941 2,256,024 Hill Sept. 16, 1941 2,291,149 Connor July 28, 1942 2,335,159 Salfisberg Nov. 23, 1943 2,361,344 Yates Oct. 24, 1944 2,391,094 Karg Dec. 18, 1945 2,475,241 Hermanson July 5, 1949 2,476,740 Krall July 19, 1949 FOREIGN PATENTS Number Country Date 430,067 Great Britain June 12, 1935

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