CA1040150A - Peelable, autoclavable packaging - Google Patents

Abstract

PEELABLE, AUTOCLAVABLE PACKAGING

Abstract of the Disclosure A web of selected sheet materials for conversion into packages for carrying sterile objects such as medical and/or surgical devices, accessories and the like; such packages being initially subjected to dry and steam autoclaving to sterilize the contents thereof and thereafter peelable to allow for access to the contents thereof. The web is coated with a heat sealable composition of a character which has its normal peel character-istic unchanged despite the initial autoclaving operation at elevated temperatures.

Description

~ G~o~n 07 r~v ~ 0~
Packages for carrying sterile articles such as dress-ings, surgical devices 7 or the like~ are ~requently rendered sterile by subjacting the package and ~ts con~ents to autoclav-ing temperatures o~ the order of at least 250 F. It .is desir-able that such packages bepeelable to deliver the contents thareo~ in a sterile ~ialdt Since such packages are normally formed from a web or webs with a coating of peelable heat seal-ing composition between panel portio~s of such webs; it has been found that a subsequent autoclaving operation ~ends to im-pair or nulli~y the peel characteristic of th~ heat sealing compositlon.
It has been proposed to o~ercome the undesirable in-crease in bonding of peelable packaging due to the autoclaving temperatures~ by elther (1) redu¢ing ths ~nltial sealing tem-peratures~ or (2) decreasing pressure of the sealing operation~
or (3) shortening the dwell timo at the point of seal.
However such expedients~ in effect~ produce under-sealed packages which tend to exhiblt leakage in the original seal and impair the maintenance of sterility in the final auto-claved package, If the usual sealing temperatures~ pressures and dwell periods are used; the subsequent autoclaving temperatures can increase the bond o~ the heat seals~ ~hich impairs the peela~le characteristiG of the autoclaved package.
Accordingly~ an object of this invention is to provide a package of the type which must b~ subject to autocla~ing to render the contents thereof sterile; where the peripheral portions Or the panels ~orming the package are secured together by a heat sealing composition which on the one hand ~orms a uniform tight~ non-leaking seal; and on the other hand, such seal is still subject to easy peeling when opening the autoclaved package to gain access to the sterile contents thereof.
The invention provides a heat sealed peelable package sterilized by autoclaving at elevated temperatures comprising a pair of substrates, at least one of said substrates having at least a continuous generally peripheral coating securing said substrates together, said coating comprising about 18.75 parts polyvinyl chloride and about 4.25 parts nitrocellulose, all by weighk, said coating retaining its normal peelable adhesive characteristic despite exposure thereof to said autoclaving temperature.

DESCRIPTION OF THE DRAWING
Figure 1 is a top plan view of a package embodying the invention;
with parts broken away;
Figure 2 is a sectional view showing superposed panel portions of the package; and Figure 3 is a partial sectional view showing an alternati~e form of web for forming the package.

DESCRIPTION OF THE PREFERRED ~MBODIMENTS
The packaging of the instant invention comprises essentially, a substrate in the form of metal foil~ suppo~ted metal foil or suitable plastic films alone or in combination form to suit the need of the i~ems being packaged and the conditions of use.

~ 3 -s0 The substrate is provided on one ~lde thereof with a coating of a heat seallng compos~tion having a th~rmoplastic re~in base and a modifier whieh is noncompatible with the resin base. Such coating provides the means ~or sealing peripheral portions of substrate panels superposed and forming the package.
The nature of the heat sealing composition i~ ~uch that it may be utili~ed under normal sealing conditions including sealing temperatures, sealing pre~sures, and sealing dwells~
which are productive of a seal in ~he fin~shed package which is proof against l~akage which would render the lnterior of the package non-sterile~ yet allows ~or easy peeling of ~he panels to open the package and to gain access to the contents thereof.
Further, such sealin~ composition allows for autocla~
ing of the sealed packages at temperatures of at leas~ 250 F.
to thereby sterilize the contents thereof, yet lea~ing the package heat seals substantially unaffected to thereby permit easy peeling of the autocla~ed package.
Thus, as shown in Fig. 1, 10 designates a package mad~
in accordance with the instant invention. Package 10 is formed from a flexible web or webs such as metal foil or the like;
with opposed panels of such webs indicated at 11, 12~ The panels ll~ 12 are precoated on the inner surface or surfaces or~
only along peripheral portions 13, 14 thereof with a thermo-plastic seal coating l~o The peripheral portion~ 13, 14 may include chevron portions ~ndicated at 16, 17, at one end o~ the package; leaving un~ecured tab portions 18, 18A to provide means for peeling panels 117 12 apart when the contents of the package lO~ not shown are to be exposed for removal from the package.
The thermoplastic seal coating 15 is ~ormed by mixing polyvinyl chloride with a plastlc non-compatible therawith, more p~rtlcularly nitrocellulos~. Thus~ the polyvinyl chloride dissolved in m~thyl ethyl ketone ls mixed with a solutivn of .~
30 second nitrocellulose in a mixture o~ toluol and methyl ethyl ketone or other suitable sol~ent.
The PVC solution contains 25~ solid~ by weight while the nitrocellulose solut~on conta~ns 17% solids by weightc From 70~ to 80~ of the PVC solution is mixed with from 30~0 to 20~ of the nitrocellulose solutlon~ Preferably 75% of the PVC solution is mixed with 25~ of the nitrocellulose solut~o~.
5ince the `solvents evaporate a:Eter the solution of mixed PVC and nitrocellulose is applied to the substrates 11, 12; the coating 15 is constituted o~ ~rom 17.5 to 20 0 parts of PVC solids and ~rom 5.1 to 3.4 parts o~ nltrocellulose solids~ all by weight. Preferably~ the proportion ls 18. 7~
parts o~ PVC and 4.25 parts of nitrocellulose~ all by weight.
The panels 11, 12 are sealed togethor after disposing the desired ob~ect~ not shown? therebetween9 by applying heat and pressure to the peripheral portions of the package, in a co~entional manner~ using the usu~lpressure sealing dies. The thus sealed packages are autoclaved in dry heat or by steam in the usual manner and~ generally at temperatures o~ from 250 to 275 F.
Despite the relatively high temperatures of the auto-claving operation, the package 10 may be readily opened by peel-ing panels 11, 12 ~part by way of tabs 18, 18A. Thus~ the elevated autoclaving temperatures do not increase the adhesion characteristlcs of the coat~ng 15 beyond the normal~ leakage proof property of said coating~
It is understood that other substrates may be used ln forming packages 10. Thus~ as shown in Flg. 3, a web 19 may be used to provld0 a substrate for package lO~ The same comprises a very thin met~l foil 20, supported on a paper 21 and adhesively se~ured thereto by suitable adhesives known in the art.
Other ~ubstrates may be used including polyester and or selectea polyole~in fllms ~ polypropylene or high density poly-ethylene films~ in unsupported or laminated form. The coating 15 may also include suitable plasticizers such as dioctyl phthalate and the like.
The coating 15 may be applied over the entire surface o~ the substrate from which panels 119 12 are derived~ rather then being limited to the peripheral areas, as descrlbed above.
The seal coating 15 may also be derivea from a composi-tion constituted o~ a ma~or proportion o~ polyvinyl acetate and a mlnor proport-lon of nitrocellulose. Such composition may be used in forming package lO and will show good peel properties despite exposure of the package to elevated autoclaving tempera-tures.
Thus, seal ~ormulations were prepared~ as follows:
~1) 70.6% polyvinyl acetate or 17.5 parts 2029.4% nitrocellulose (30 second) 7.28 parts

(2) 80.0~ polyvinyl ~cetate or 20.0 parts 20.0% nitrocellulose 5.0 parts

(3) 76~2% polyvinyl acetate or 18.75 parts 23.~% nitrocellulose 5.86 parts 2~ The foregoing are all in percentages and parts by weight; formulation (3) being preferred.
Packages prepared as previously described; the seal coating 15 ha~ing a compositlon made up of polyvinyl acetate and nitrocellulose~ in accordance with formulations (l) ; (2) ~
and (3); were sub~ected to elevated autoclaving temperatures to --6_ render the contents o:e the packages sterile.
The autoclaved packages were tested :Eor peel~bility and found to be within acceptable peel valu~s.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A heat sealed peelable package sterilized by autoclaving at elevated temperatures comprising a pair of substrates, at least one of said substrates having at least a continuous generally peripheral coating securing said substrates together, said coating comprising about 18.75 parts polyvinyl chloride and about 4.25 parts nitrocellulose, all by weight, said coating retaining its normal peelable a adhesive characteristic despite exposure thereof to said autoclaving temperature.

2. A package as in claim 1 wherein at least one of said pair of substrates comprises metal foil.

3. A package as in claim 1 wherein at least one of said pair of substrates comprises metal foil and a supporting layer adhesively secured to said foil.