Note: Descriptions are shown in the official language in which they were submitted.
~ 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
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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
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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.
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