Package and seal
US 3123210 A
Description (OCR text may contain errors)
March 1964 w. A. HERMANSON ETAL 3,123,210
PACKAGE AND SEAL Filed Aug. 10, 1961 Fig. I.
INVENTORS William A. Hermunson Edward J. Cosqrove ATTORNEY United States Patent 3,123,210 PACKAGE AND SEAL William A. Hermanson, Brookline, Mass., and Edward J. Cosgrove, Broolrfield, Conn., assignors, by direct and mesne assignments, to Bard-Parker Company, Inc.,
Danbury, Conn., a corporation of New York Filed Aug. 10, 1961, Ser. No. 130,573
4 Claims. (Cl. 206-63.2)
This invention relates to expendable packages and more particularly to seals for expandable packages.
The general purpose of this invention is to provide expendable packages, made of flexible porous sheet material, which are capable of being readily opened after the contents have been sealed therein without contaminating the contents or the surfaces over which the contents are moved and which do not fail in their heat bonded zones when subjected to sterilization conditions.
Various items, including surgical items such as surgeons blades, hypodermic needles, hypodermic syringes, sutures, catheters, dressings, gloves, etc. have been packaged in sterilized or sterilizable form, some of these being in sealed envelope type packages. In order to open the package, the envelope is broken, for instance, by tearing the walls thereof. Such packages, in many instances, are unacceptable since the required method of opening may tend to contaminate the sterilized contents by contact thereof with the torn edges of the package material. Other expendable packages, particularly for surgical items, have been fabricated from rather heavy, resin coated, metal foils. Metal foil type packages in many instances are unattractive from an economic viewpoint, particularly where the package contents comprise relatively low cost items. Still other surgical items have been packaged in coated papers or like materials having relatively low melting resin or wax type coatings and these can not be satisfactorily sterilized.
The primary object of this invention is to provide an expendable package in which items, including surgical items or other objects, may be sealed and sterilized for temporary storage purposes, prior to use, including use in surgical operations and other treatment of patients, where it is of primary importance that such items or other objects be free from bacterial organisms.
Another object of the invention is to provide an expendable heat bonded package for items, including surgical items: which is made of a material that is sufiiciently porous to allow for the sterilization of items carried therein, but of close enough texture as to inhibit the passage of pathogenic organisms therethrough after the sterilization process and during storage under normal storage conditions, and which does not fail in its heat bonded zones during and after the sterilization process.
Still another object of the invention is to provide an expendable heat sealed package for surgical items which is made of a porous base material and which has a cohesive nature in its heat sealed portions during and after sterilization in order that it will adhere to itself or like materials and yet be of such tackiness as to be separated by a predetermined stress without tearing.
Other objects, uses and advantages will become apparent from a reading of the following specification when considered in the light of the attached drawings, in which:
FIGURE 1 is a plan view of a sealed package of the invention containing a surgeons blade; and
FIGURE 2 is an enlarged section along 2-2 of FIG- URE 1 showing a section of the strippable seal zone of the sealed package.
While a surgeons blade is illustrated and described as the item to be packaged in accordance with the invention, it will be understood that the invention is not limited to use with a surgeons blade but may be used for packaging other items, including surgical items.
Describing the invention in detail and referring to FIG- URE 1, the container or package is generally indicated at 10 and is comprised basically of two superposed sheets 12 and 14 of porous material, as described hereinafter, heat sealed to one another along the sealing zone 16 which surrounds and is spaced from enclosed blade 18 and which forms the space 20 between the two sheets within the sealing zone 16. The sealing zone 16 comprises two parallel side seal lines 22 which are connected together with transverse seal line 24. At the end opposite transverse line 24, sealing zone 16 is formed along converging seal lines 26 coming to the apex 28. These converging seal lines allow the two sheets 12 and 14 to be easily separated with a small amount of force.
The apex 28 is spaced from the ends of the sheets 12 and 14 to form free end tabs 30 and 32 therein. The sheet 14 (as shown) may be greater in length than the sheet 12 so as to allow tab 62 to protrude beyond the free end tab 30 thereby permitting easy separation of these tabs when grasped to separate sheets 12 and 14.
In accordance with the invention, the package as illustrated in FIGURE 1 is formed of two sheets of impregnated and coated web material which is sufiiciently porous to allow for sterilization of items carried therein, but of close enough texture as to resist the passage of pathogenic organisms therethrough after the sterilization process and during storage of the package under normal storage conditions. The impregnated and coated web material is schematically illustrated in FIGURE 2 and is essentially comprised of: a base sheet 34; and a bicomponent heat scalable resin coating 36.
The base sheet 34 may be comprised of an uncompressed low density web formed from relatively long natural cellulosic fibers, such as virgin abaca fibers or the like. A long fiber-low density uncompressed web results in a base sheet (before further treatment) having an extremely rough texture with prominent fiber crests and depressions and large interfiber interstices.
The uncompressed fiber web may be heavily saturated or impregnated with a blended unvulcanized latex dispersion whereby the finished weight of the base sheet may be as much as 2 to 2 /2 times the weight of the unsaturated fiber web without appreciable increase in the web thickness. The term latex dispersion as used herein shall mean any colloidal system of natural or synthetic rubber solids and/or synthetic emulsion polymers in the colloidal range which are capable of coagulation and which exhibit elastomeric properties. The fiber web may also be impregnated with a resin (such as phenolic, melamine formaldehyde, urea formaldehyde or modifications thereof, or regenerated cellulose) to provide wet strength to the web. These resins, when introduced into the fiber web (either with the latex dispersion or subsequent thereto) in an amount equal to about A to 3% by weight of the virgin fibers and cured, are found to preferentially solidify at the fiber crossing junctions. For the most part, the areas of solidified wet strength resin are within the web and below the top surface thereof because of their contraction during cure. As a result of the foregoing, the base sheet 34, as described, has high flexural and edge tear strength and great bursting strength to resist puncture and has a wet strength almost equal to its dry strength thereby to withstand long periods of immersion in liquids such as germicidal solutions or submission to dry or wet steam during autoclaving or submission to sterilizing gases such as ethylene oxide or propylene oxide. The surfaces of such a base sheet remain irregular because the great length of the web fibers, low initial web density and uncompressed condition of the web cause the latex dispersion and wet strength resin to substantially migrate and contract within the web during saturation and impregnation thereof. The low density and microporosity of such a base sheet make point temperature of about 120 F. and an optimum film forming temperature of about 250 to 260 F.; the film being such that, when subjected to temperatures ranging from its distortion point to its optimum film forming point or optimum coalescence point, it will slip or fiow.
The second component of the dual-acting bicomponent mixture forming coating 36 comprises a material which acts in the nature of a thermosetting resin, i.e., sets-up or cures upon the application of heat and becomes irreversible. Such component may be a non-vulcanized synthetic rubber latex of an acrylonitrilebutadiene copolymer which has elastomeric properties and which cures to a three dimensional structure.
Where a porous base 34 is utilized to form the packaging material, the hydrophilic coating 36 may be deposited on, and adhered to, the base sheet in such a manner as to leave a substantial number of the base sheet pores unblocked whereby steam, sterilizing gases and/ or germicidal solutions may pass through the coated sheet. To accomplish this objective the bicomponent coating 36 may be lightly printed on the base sheet as by a roll which has been engraved so as to print an interrupted pattern of the coating material or such coating may be applied by conventional coating means such as by a doctor roll or blade. The resulting low caliper bicomponent coating is thereby, for the most part, deposited on the crests of the surface fibers of the base sheet with the secondary (latex) component being absorbed into the lower strata of the fiber web of the base sheet.
It has been found that the low caliper deposit of bicomponent coating on one side of the base sheet (about 1% ounces to about 1% ouncesof coating per square yardof base sheet) will yield a discontinuous coating of greater thicknesses on the fiber crests than on the sides of the fibers of the web. The coating, therefore, does not block any significant number of the interfiber interstices of the base sheet.
Where the base sheet is formed as described above, the interfiber interstices preferably range from 5 to 150 microns in diameter while the fibers preferably range in diameter from 16 to 32 microns. Thus,'it can be readily seen that the fibers, having a mean diameter of 24 microns, cannot close up all the interfiber interstices (pores).
When the bicomponent coating of packaging sheets 12 and 14 are brought into intimate face to face contact by heated, pressure sealing, elements, a sealing zone 16 of the bicomponent bonding material is created whereby the packaging sheets are bonded together. Because of the nature of the coating, the sealing zone (in fact) consists of a multiplicity of strong, intermediate and Weakly bonded points. Thus, when a package, such as shown in FIGURE 1, if formed by peripheral bonding of the packaging sheets of the invention, the packaging sheets will, when pulled apart (as by tabs and 32), release without delaminating the inner strata or coating 36 from the base material 34. Prior to separation, the sealed sheets will (due to the presence of a sufiicient number of strong bonding points in the sealing zone) constitute a completely satisfactory closed package having good shelf life.
The strong interface bonds in the sealing zone must be strong enough to maintain the sealed relationship of the packaging sheets while in contact with steam during autoclaving, with gases during gas sterilization, or while in contact with germicidal solutions, yet not so strong as to cause delamination of the bicomponent coating during opening of the package formed by such sheets.
The coating comprises one component yielding a suitable dry bond after heat sealing of the packaging sheets which weakens when subjected to autoclaving temperatures because of its thermoplastic property and a second component which initially has weak bonding characteristics in its dry state but develops substantially stronger bonding characteristics when subjected to elevated temperatures since it acts in the nature of an irreversible thermosetting adhesive which cures or sets-up upon heating. Also, such bonds have been found to withstand long periods of immersion in common germicidal solutions, such as the alcohol-formaldehydes and quaternary-am moniums, even though such solutions cause some solvation of the bonds.
To illustrate the improvement in packaging achieved by incorporation of package and bond features of the present invention, bond values for representative surgeons blade packages (made in accordance with the invention and as shown in FIG. 1) were measured before and after autoclaving.
Package for stainless steel surgeons blades:
Two superimposed Average bond value before autoclaving of 10 product packages Average bond value after autoclaving (250 F. for 30 minutes) of 10 product 0.848 lbs.
packages 1.070 lbs. Percent increase in bond value 22.6 percent.
Autoclaved surgeons blade packages similar to those tested in the above illustration were found to have resisted contamination under normal storage conditions with the enclosed surgeons blade found to be sterile when tested in accordance with conventional procedures (U.S. Pharmacopoeia) The above described package and packaging material is completely adequate where the package is to contain sterilizable non-corrosive items such as plastic sutures, catheters, etc. or stainless steel items such as stainless steel blades. Where the package is to contain items which are subject to corrosion in the presence of wet steam of germicidal solutions, the impregnated fiber web comprising the base sheet 34 may be coated with a corrosion inhibitor which, when dried, receives the bicomponent coating 36. The corrosion inhibitor, which must be compatible with the bicomponent coating, for the most part permeates the pores of the base sheet leaving the base sheet with the previously described irregular surface configuration and open pore structure whereby the bicomponent coating 36 has an interface bonding struc ture similar to that described above.
The heat seal bonds of the packages described have been found to be strong enough to stand-up, without the package opening, during 30 minutes of steam autoclaving at 250 F. at 15 psi. Further, although the thermoplastic sealing component softens during such autoclaving, the second component of the sealing mixture cures to provide the relatively strong bond desired for packaging of the nature described. The packaging material and bonds described have also been found to resist destruction during soaking in common germicidal solutions for 30 minutes or more. The packaging maerials and construction disclosed permit uniform, non-delaminating, release of the sheet from which the package is formed when such sheets are pulled apart.
The build-in microporous structure of the packaging material of this invention permits sterilization of the contents of the package (after being sealed therein) by wet or dry steam, gases such as ethylene oxide and propylene oxide, or germicidal bath methods without damage to the package or its contents with the packaging material thereafter acting as a micropore filter resistant to permeation of pathogenic organisms under ordinary storage conditions. Further, it should be understood that the packaging material of this invention may be used with other packaging materials which have a compatible heat bonding surface or zone. Thus, one of the sheets of packaging material might be comprised of glassine type transparent material coated (at least in the area of heat seal) with the cohesive bicomponent bond material; or a polyester film such as the polymeric ester of ethylene glycol and terephthalic acid, commonly referred to as Mylar, coated with the cohesive bicomponent coating applied in the intended heat bond areas or zones. It may also be convenient to form packages of the nature described of but a single sheet of the porous, adhesive coated, material described with such sheet folded to provide face to face contact of the adhesive coating in the seal zone surrounding the packaged contents.
While the invention has been described in its preferred form, other modifications may be resorted to without departing from the spirit thereof, and the scope of the invention will be best defined in the appended claims.
1. A package resistant to tearing and puncture and to the passage of microorganisms and sterilizable by steam autoclaving or gas permeation which comprises: a surgical blade; an envelope encasing said surgical blade and formed of two layers of sheet material disposed on opposite sides of said surgical blade with marginal portions extending beyond said surgical blade and disposed in contacting relationship, each of said layers being a web of between approximately 0.003" and 0.017 in thickness and resistant to tear and puncture and formed of fibers of between approximately 16 and 32 microns in diameter with interfiber interstices of between 5 and 150 microns so that steam and gas may permeate therethrough but so as to resist the passage of microorganisms; and bicomponent adhesive coatings on the confronting faces of said layers arranged in a discontinuous pattern with the major portions being located on the fiber crests and with a substantial number of said interfiber interstices free from said adhesive coating and unblocked and said hicomponent coating being formed of a major portion of a thermoplastic material having a softening point below 250 F. and a minor portion of a nonvulcanized synthetic rubber latex having elastomeric and heat curing properties, said contacting marginal portions being bonded together along at least one continuous line extending around said surgical blade by heat reversible bonds of said thermoplastic material and when subjected to autoclaving, heat irreversible bonds are formed in said synthetic rubber latex component of the coatings along said continuous line, all of said bonds being rupturable without tearing said webs.
2. A package resistant to tearing and puncture and to the passage of microorganisms and sterilizable by steam autoclaving or gas permeation as set forth in claim 1 in which the thermoplastic component is polyvinyl chloride and comprises between approximately and by weight of the adhesive mixture and the synthetic rubber latex is acrylonitrile-butadiene copolymer and comprises between approximately 40% and 30% by weight of the mixture.
3. A package resistant to tearing and puncture and to the passage of microorganisms and sterilizable by steam autoclaving or gas permeation as set forth in claim 1 in which the two layers project beyond the marginal seal line at one marginal portion of the package with the projecting portion of one layer extending beyond the other layer so that said projecting portions may be readily and separately grasped to open the package.
4. A package resistant to tearing and puncture and to the passage of microorganisms and sterilizable by steam autoclaving or gas permeation as set forth in claim 1 in which the webs are saturated with a nonvulcanized latex dispersion and impregnated with a wet strength resin.
References Cited in the file of this patent UNITED STATES PATENTS 2,330,353 Henderson Sept. 28, 1943 2,414,833 Osborne Ian. 28, 1947 2,552,904 Newberg et al. May 15, 1951 2,684,351 Williams July 20, 1954 2,724,675 Williams Nov. 22, 1955 2,866,542 Svirchev Dec. 30, 1958 2,947,415 Garth Aug. 2, 1960 2,969,872 Chambers Jan. 31, 1961 2,997,224 Stannard Aug. 22, 1961 2,998,880 Ladd Sept. 5, 1961