Single hinge interlocking closure profile configuration

An interlocking closure fastening device comprising an omega-shaped closure element and a co-acting clamping closure element. The co-acting clamping closure element may have a profile portion comprising two generally parallel arm portions wherein one of the arm portions terminates in an inwardly curved hook portion, and the other arm portion curves slightly inward prior to terminating in an outwardly extending clamp portion; or the profile portion may comprise two outwardly curved arm portions wherein one of the arm portions terminates in an inwardly curved hook portion, and the other arm portion curves inwardly prior to terminating in a slightly outwardly curved hook portion; or the profile portion may comprise one inwardly curved arm portion terminating in an inwardly curved hook portion, and one generally straight arm portion.

CROSS REFERENCE TO RELATED APPLICATION 
This application is a continuation-in-part application of prior application 
Ser. No. 567,240 filed Dec. 30, 1983 for Single Hinge Interlocking Closure 
Profile Configuration, and is related to copending application Ser. No. 
567,242 filed Dec. 30, 1983 for Interlocking Closure Bag for use in High 
Temperature Environment. 
FIELD OF THE INVENTION 
This invention relates to an interlocking closure fastening device, and 
more particularly, to an interlocking closure fastening device comprising 
an omega-shaped closure element and a co-acting clamping closure element. 
BACKGROUND OF THE INVENTION 
In general, closure fastening devices for use in connection with plastic 
bags and the like are known. Furthermore, manufacturing methods for 
closure fastening devices made of plastic material are generally 
well-known. 
In operation, a closure fastening device for use in connection with a 
flexible container should be relatively easy to open from the outside, but 
relatively difficult to open from the inside. Generally, such a container 
can be used with its interior either under relatively high pressure or 
under relatively low pressure. The closure fastening device should provide 
a satisfactory seal for either condition. 
Preferably, the closure fastening device should be suitable for economical 
manufacturing and should be relatively simple in design. In addition, the 
design should provide for variations in order to meet different needs. For 
example, it may be desirable to have a closure fastening device which is 
relatively difficult to open both from the inside and the outside. In 
general, the closure fastening device, however, should always be 
relatively easy to close. 
In addition, when the closure fastening device is employed with a 
container, the container may be made from a thermoplastic material and the 
closure device and sidewalls of the container can be made integrally by 
extrusion as a unitary piece or can be made as separate components which 
are subsequently permanently connected together. 
However, the thermoplastic resin materials heretofore found practical for 
the extrusion of interlocking closure devices, and their attachment to 
films, such as in making containers, have resulted in shrinkage and 
distortion problems during their use at elevated temperatures. Typical 
resin materials employed for interlocking closure devices and container 
films have included polyethylene, polyvinyl chloride copolymers, and 
synthetic rubbers. However, none of these construction materials have 
sufficient thermal tolerance for many commercial uses. Further, both 
occlusion and deocclusion of the interlocking closure device is generally 
difficult for the user when the device is made from resin materials having 
high temperature tolerances due to their associated high flexural moduli. 
Thus, in selecting a resin composition for the profile portions and the 
flange portions of a closure fastening device which is employed on a bag 
or container for use in a high temperature environment, such as in a 
microwave oven or boiling water, the resin composition must meet several 
criteria. These criteria include high heat resistance, relatively low 
flexural modulus at low temperatures, acceptable extrusion 
characteristics, and convertibility of the film into end products such as 
bags or containers. High heat resistance is necessary because when the bag 
or container is equipped with the interlocking closure fastening device 
and is used in a microwave oven where food temperatures can reach about 
300.degree. F., or in boiling water where the temperature of the cooking 
vessel can exceed 212.degree. F., the closure fastening device must retain 
proper occlusion and deocclusion forces. The resin composition must also 
be flexible at low temperatures because such bags or containers are often 
used in a freezer for food storage, and when removed from the freezer, the 
closure fastening device must be sufficiently flexible so that the bags or 
containers can be easily opened when such is desired as to remove food 
therefrom. In addition, the resin composition for the interlocking closure 
fastening device must have acceptable extrusion characteristics so that it 
can be easily processed in production and make a reliable, reproducible 
product. 
In the extrusion of such interlocking closure fastening devices, it is 
desirable to extrude closure elements having base and profile portions 
onto a common flange portion, separate the closure elements, and then 
attach the closure elements to the bags or containers. This operation 
presents a problem in the closure extrusion phase because some of the 
closure elements are near the outer edges of the flange portion which is 
an area conducive to "neck-in" of the resin material. "Neck-in" may be 
described as a decrease in an article's dimensions transverse to the 
take-off or elongation direction of the article. In such event, the edges 
of the flange portion exiting from the die will shrink toward the center 
of the flange portion in a curved path. When the edge of a flange portion 
"necks-in" toward the center of the flange portion, a closure element 
positioned near the flange edge will travel with the edge of the flange 
portion. The result is that the closure element is not extruded in a 
straight line as desired, but follows the curved path of the edge of the 
flange portion. This result causes distortion of the closure element due 
to the two dimensional path followed by the closure element. Therefore, in 
choosing a resin composition for the flange portion of a closure fastening 
device as described herein, it is highly desirable to employ a resin 
composition that suffers a minimum of "neck-in" so that the closure 
elements extruded near the outer edges of the flange portion travel in as 
close to a straight line as possible which minimizes closure distortion. 
On the other hand, when choosing a resin composition for the closure 
elements, i.e., the base and profile portions, of the interlocking closure 
fastening device, the main concern is to employ a composition that will 
retain the intricate profile shapes of the closure elements during the 
extrusion process and during the cooling process. This concern is more 
important than limiting "neck-in" tendencies of the resin composition. 
SUMMARY OF THE INVENTION 
The foregoing criteria for a closure fastening device are met by this 
invention wherein the closure fastening device comprises a first closure 
element and a second closure element which are adapted to interlock by 
pressing the first closure element into the second closure element, and 
wherein the closure fastening device is made from a thermoplastic material 
comprising a polypropylene polymer. In one suitable fastening device 
includes a first closure element having a general omega shape comprising 
an apex portion, and a profile portion extending from the apex portion, 
said apex portion being generally flat or slightly arcuate, and said 
profile portion comprising two inwardly curved arm portions terminating in 
two outwardly facing, curvilinear hook portions. The closure device 
includes a second closure element having a generally flat or slightly 
arcuate apex portion, and a profile portion extending from the apex 
portion. The profile portion of the second closure element comprises first 
and second generally parallel arm portions wherein one of the arm portions 
terminates in an inwardly curved hook portion, and the other arm portion 
curves slightly inward prior to terminating in an outwardly extending 
clamp portion. The first closure element and the second closure element 
are adapted to disengage and engage each other by means of rotation of one 
closure element with respect to the other closure element, such as by a 
hinging action so as to form a straddling type of occlusion. A straddling 
type of occlusion occurs when one arm portion of the second closure 
element is lodged between the two arm portions of the first closure 
element, while the other arm portion of the second closure element is 
outside one of the arm portions of the first closure element when the 
closure device is occluded. 
In another embodiment of this invention, the fastening device includes a 
first closure element having a general omega shape comprising an apex 
portion, and a profile portion extending from the apex portion, said apex 
portion being generally flat or slightly arcuate, and said profile portion 
comprising two inwardly curved arm portions terminating in two outwardly 
curving hook portions. The closure device includes a second closure 
element having a generally flat or slightly arcuate apex portion, and a 
profile portion extending from the apex portion. The profile portion of 
the second closure element comprises two outwardly curved arm portions 
wherein one of the arm portions terminates in an inwardly curved hook 
portion, and the other arm portion curves inwardly prior to terminating in 
a slightly outwardly curved hook portion. The first closure element and 
the second closure element are adapted to disengage and engage each other 
by means of rotation of one closure element with respect to the other 
closure element, such as by a hinging action so as to form an overlapping 
type of occlusion. An overlapping type of occlusion occurs when both arm 
portions of the first closure element are within, or inside of, both arm 
portions of the second closure element when the closure device is 
occluded. 
In a further modification of the preceding embodiment, the profile portion 
of the second closure element comprises two outwardly curved arm portions 
wherein one of the arm portions terminates in an inwardly curved hook 
portion, and the other arm portion curves progressively inwardly as to 
make contact with one of the arm portions of the first closure element 
when the fastening device is occluded, prior to terminating in a slightly 
outwardly curved hook portion. 
In a further embodiment of this invention, the fastening device includes a 
first closure element having a general omega shape comprising an apex 
portion, and a profile portion extending from the apex portion, said apex 
portion being generally flat or slightly arcuate, and said profile portion 
comprising two inwardly curved arm portions, an outwardly extending arm 
portion from each of said inwardly curved arm portions, each of said 
outwardly extending arm portion terminating in an outwardly curved hook 
portion. The closure device includes a second closure element having a 
generally flat or slightly arcuate apex portion, and a profile portion 
extending from the apex portion. The profile portion of the second closure 
element comprises one inwardly curved arm portion terminating in an 
inwardly curved hook portion, and one generally straight arm portion 
extending from said apex portion in a generally perpendicular direction 
therefrom. The first closure element and the second flexible closure 
element are adapted to disengage and engage each other by means of 
rotation of one closure element with respect to the other closure element, 
such as by a hinging action so as to form a straddling type of occlusion 
as earlier described. During deocclusion of the aforedescribed closure 
fastening devices, one closure element must be rotated between about 30 
degrees to about 50 degrees with respect to the other closure element to 
disengage the arm portions thereof located closer to the exterior portion 
of a container, and further rotated between about 70 degrees to about 120 
degrees with respect to the other closure element to disengage the arm 
portions thereof located closer to the interior portion of the container.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The closure fastening device of the instant invention may be made from a 
thermoplastic material selected from the group consisting of polyolefins 
such as polyethylene, polypropylene, and polybutylene; polyamides such as 
nylon; or other thermoplastic materials, including combinations thereof. 
The closure fastening device is preferably made from a thermoplastic resin 
composition comprising polypropylene, or a mixture of polypropylene resin 
and ethylene-propylene-diene monomer elastomer, or a mixture of 
polypropylene resin and ethylene-propylene copolymer elastomer. In the 
preferred mode, the closure fastening device of this invention is made 
from a polypropylene copolymer, or a blend selected from (a) a 
polypropylene copolymer and a polypropylene homopolymer, (b) a 
polypropylene copolymer and a polybutene copolymer, (c) a polypropylene 
copolymer and an elastomer, and (d) mixtures of (a), (b), and (c). More 
specifically, it is preferred that the closure elements comprise a 
poly(propylene-ethylene) copolymer having an ethylene content of less than 
about 5 percent by weight of the copolymer because too much ethylene will 
lower the melting point of the copolymer and cause distortion of the 
closure profile during extrusion, and between about 100 ppm and about 2000 
ppm of a slip agent based on the weight of the polypropylene copolymer. 
The slip agent is preferably selected from fatty acid amides such as 
erucamide. Suitable alternative compositions for the closure elements 
comprise a blend of (a) from about 85 to about 95 percent by weight of 
polypropylene homopolymer and from about 5 to about 15 percent by weight, 
preferably about 10 percent by weight, of a poly-1-butene copolymer 
containing up to about 5 percent by weight of ethylene; (b) from about 85 
to about 95 percent by weight of polypropylene homopolymer and from about 
5 to about 15 percent by weight, preferably about 10 percent by weight, of 
ethylene-propylene-diene monomer elastomer; (c) from about 85 to about 95 
percent by weight of polypropylene homopolymer and from about 5 to about 
15 percent by weight, preferably about 10 percent by weight, of 
ethylene-methyl acrylate copolymer; (d) from about 10 to about 50 percent 
by weight of polypropylene homopolymer and from about 50 to about 90 
percent by weight, preferably about 70 percent by weight, of a 
poly(propylene-ethylene) copolymer selected from the group of 
poly(propylene-ethylene) copolymers having a melt flow rate of between 
about 1.5 and about 8, and preferably, about 7 grams/10 minutes as 
determined by ASTM test method D-1238, Condition "L", and a flexural 
modulus of between about 100,000 and about 132,000 psi or an MPa value of 
between about 690 and about 924 as determined by ASTM test method D-790; 
and (e) from about 85 to about 95 percent by weight of 
poly(propylene-ethylene) copolymer and from about 5 to about 15 percent by 
weight, preferably about 10 percent by weight, of a copolymer selected 
from the group consisting of (1) a poly-1-butene copolymer containing up 
to about 5 percent by weight of ethylene; (2) an ethylene-propylene-diene 
monomer elastomer; and (3) an ethylene-methyl acrylate copolymer. As in 
the best mode compositions employed to make the closure fastening devices 
herein, all of the alternative compositions preferably contain between 
about 100 ppm and about 2000 ppm of a slip agent selected from fatty acid 
amides based on the weight of the blends. 
The foregoing resin materials are all commercially available. For example, 
the poly(propylene-ethylene) copolymer material may be obtained from 
Himont Inc., Wilmington, Del. under the tradename Pro-Fax.RTM. SA-861; the 
polypropylene homopolymer may be obtained from Shell Chemical Company 
under the tradename Shell Polypropylene 5225; the poly-1-butene copolymer 
containing up to about 5 percent by weight of ethylene may be obtained 
from Shell Chemical Company under the tradename Shell Polybutylene 8640; 
the ethylene-propylene-diene monomer elastomer may be obtained from 
Uniroyal Chemical, Naugatuck, Conn. under the tradename Royalene IM 7565 
as a 65/35 weight blend of the elastomer (high density polyethylene; the 
ethylene-methyl acrylate copolymer is available from Gulf Oil Chemicals 
Company under the tradename PE 2205; the poly(propylene-ethylene) 
copolymer may also be obtained from Cosden Oil Company under the 
tradenames Dypro W-431 and Dypro K-122, and from Himont Inc., Wilmington, 
Del. under the tradename Pro-Fax.RTM. SA-752. 
It has been found that when interlocking closure elements are made from the 
foregoing resin compositions, the profile portions of the closure elements 
retain their shapes and have a low flexural modulus under the extreme 
temperature conditions thereby meeting the aforementioned criteria for an 
interlocking closure fastening device. The poly(propylene-ethylene) 
copolymer enhances the extrudability of the closure elements because they 
retain their shapes better during manufacture than when made from other 
materials. The dimensions of the closure fastening device may vary in 
accordance with intended use, and depending upon the materials used in 
their manufacture because of the variations in physical properties, such 
as flexural moduli. 
The closure fastening device of this invention can be manufactured by known 
methods such as by extrusion, by the use of molds or other known methods 
of producing such devices. The closure fastening device can be 
manufactured as a strip for later attachment to a film or it can be 
manufactured integral with the film. In addition, the closure device can 
be manufactured with or without flanges on one or both of the closure 
elements, depending upon intended use or expected additional manufacturing 
operations. 
Thus, when the closure device is connected to a container, it is preferred 
that the closure device be manufactured with flanges on each of the 
closure elements so that the flanges can be used to connect the closure 
elements to the container or to a film to be formed into a container. The 
flanges of the closure device may be made from a thermoplastic material 
selected from the group consisting of a polypropylene homopolymer, a 
poly-1-butene copolymer, an ethylene-propylene-diene monomer elastomer, 
and an ethylene-methyl acrylate copolymer. However, in the best mode of 
this invention, the flanges of the closure device are made from a blend of 
a polypropylene homopolymer and a poly-1-butene copolymer. More 
specifically, it is preferred that the flanges comprise from about 85 to 
about 95 percent by weight of polypropylene homopolymer and from about 5 
to about 15 percent by weight of poly-1-butene copolymer containing up to 
about 5 percent by weight of ethylene. More preferably, the flanges 
comprise about 90 percent by weight of polypropylene homopolymer and about 
10 percent by weight of poly-1-butene copolymer containing up to about 5 
percent by weight of ethylene. Less preferred, but suitable, alternative 
material compositions for the flanges comprise (a) from about 85 to about 
95 percent by weight of polypropylene homopolymer and from about 5 to 
about 15 percent by weight of ethylene-propylene-diene monomer elastomer; 
or (b) from about 85 to about 95 percent by weight of polypropylene 
homopolymer and from about 5 to about 15 percent by weight of 
ethylene-methyl acrylate copolymer, or (c) mixtures of (a) and (b). 
The foregoing resin materials are commercially available. For example, the 
polypropylene homopolymer material may be obtained from Shell Chemical 
Company under the tradename Shell Polypropylene 5225; the poly-1-butene 
copolymer containing up to about 5 percent by weight of ethylene may be 
obtained from Shell Chemical Company under the tradename Shell 
Polybutylene 8640; the ethylene-propylene-diene monomer elastomer may be 
obtained from Uniroyal Chemical, Naugatuck, Conn., under the tradename 
Royalene IM 7565 as a 65/35 weight blend of the elastomer/high density 
polyethylene; and the ethylene-methyl acrylate copolymer is available from 
Gulf Oil Chemicals Company under the tradename PE 2205. 
It has been found that when the flange portions of the interlocking closure 
fastening device of this invention are made from the foregoing resin 
compositions, distortion of the closure elements is significantly reduced 
since the flange portions of the closure device experience minimal neck-in 
during extrusion. It has been found that the polypropylene homopolymer 
reduces neck-in of the flange portions during extrusion, and that the 
presence of poly-1-butene reduces the flexural modulus of the 
polypropylene homopolymer making the device suitable for use after storage 
in a freezer. In preferred practice, the flanges and the closure elements 
are coextruded, however, the flanges and the closure elements may be 
extruded separately and then attached to each other by conventional means. 
The closure elements can be connected to a container or to a film to be 
formed into a container by the use of many known methods. For example, a 
thermoelectric device can be applied to a film opposite a closure element 
to cause a transfer of heat through the film to produce melting at the 
interface of the film and the closure element. After cooling, the 
interface region joins the film and the closure element. 
The thermoelectric device can be heated by rotary discs, or resistance 
heated wires, or traveling heater bands, or the like. 
The connection between the film and the closure element can also be 
established by the use of hot melt adhesives, or hot jets of air to the 
interface, or ultrasonic heating, or other known methods. 
Generally, the present closure fastening device can be made from a heat 
sealable material and then attached to a heat sealable film so that a 
container can be formed economically by heat sealing surfaces to form the 
container. 
The instant closure fastening device provides many advantages for consumers 
when used on containers. For instance, it is easy to open and close a 
container because the closure elements hinge or rotate with respect to 
each other from the deoccluded to the occluded position, and from the 
occluded position to the deoccluded position with little effort, even 
though the closure device is made from high flexural moduli resins having 
high temperature resistance. An important aspect of the closure fastening 
device of this invention is its ability to function properly when made 
with materials which are less flexible than those employed in the prior 
art. That is, prior art closures are generally made of polyethylene having 
a low flexural modulus, and engage and disengage by a flexing action, 
whereas the instant closures are different therefrom in that they function 
by a hinging action or operation since they are made from high temperature 
resistant resin materials having high flexural modulus properties, i.e., 
at least about 50,000 psi. The action contrasts with prior art structures 
such as arrow type of closures where, in the female elements, the hooked 
sides have to be bent or otherwise distorted for occlusion or deocclusion. 
In a prior art channel closure a base portion has to be bent to accomplish 
occlusion or deocclusion. And still another structure made very stiff, 
requires longitudinal displacement to a non-hooked end before the male and 
female elements can be pried apart by elastic bending of portions of each 
element. 
For a fuller understanding of the nature of the invention, reference should 
be had to the following detailed description, taken in conjunction with 
the accompanying drawings. 
FIG. 1 is a cross-sectional view of one embodiment of the closure fastening 
device in accordance with this invention, in an occluded position. As 
shown therein, a first closure element 10 having a general omega shape is 
connected to a flange portion 11 for use in connection to a thermoplastic 
film. Closure element 10 has an apex portion 12 which is typically flat or 
slightly arcuate, and extending from apex portion 12 is a profile portion 
which comprises two inwardly curved arm portions 13 and 13' which 
terminate in two outwardly curving hook portions 14 and 14', respectively. 
A second closure element 15 is shown connected to a flange portion 16, and 
it comprises an apex portion 17 which may have a flat or slightly arcuate 
configuration. Extending from apex portion 17 is a profile portion 
comprising two generally parallel arm portions 18 and 18'. Arm portion 18' 
terminates in an inwardly curved hook portion 19, whereas arm portion 18 
curves slightly inwardly prior to terminating in an outwardly extending 
clamp portion 20. As shown in FIG. 1, when the closure fastening device is 
in an occluded position, hook portion 14' of closure element 10 and hook 
portion 19 of closure element 15 are interlocked, and arm portion 18 and 
clamp portion 20 of closure element 15 are in locked contact with arm 
portion 13 of closure element 10. It can also be seen from FIG. 1 that arm 
portion 18' terminating in inwardly curved hook portion 19 is adapted to 
engage in a hinging contact with arm portion 13' terminating in outwardly 
curving hook portion 14', and arm portion 18 terminating in outwardly 
extending portion 20 is adapted to engage in a clamping contact with arm 
portion 13 terminating in outwardly curving hook portion 14. As can be 
seen from FIG. 1, closure element 10 and closure element 15 form a 
straddling occlusion wherein arm portion 18 and clamp portion 20 of 
closure element 15 are positioned between arm portions 13 and 13' of 
closure element 10. When the closure fastening device is connected to a 
plastic container, arm portion 13 and hook portion 14 are positioned 
closest to the mouth or outside portion of the container, and arm portion 
18' is positioned closest to the interior or inside portion of the 
container. 
FIG. 2 is a cross-sectional view of another embodiment of the closure 
fastening device in accordance with this invention, in an occluded 
position. It may be seen therefrom that the first closure element 21 has a 
general omega shape, and that it may be connected to a flange portion 22 
for connection to a thermoplastic film. Closure element 21 has an apex 
portion 23 which is slightly arcuate or generally flat, and extending from 
apex portion 23 is a profile portion which comprises two inwardly curved 
arm portions 24 and 24' which terminate in two outwardly curving hook 
portions 25 and 25', respectively. A second closure element 26 is shown 
connected to a flange portion 27, and it comprises an apex portion 28 
which has a flat or slightly arcuate configuration. Extending from apex 
portion 28 is a profile portion comprising two outwardly curving arm 
portions 29 and 29'. Arm portion 28' terminates in an inwardly curved hook 
portion 30, and arm portion 29 curves inwardly prior to terminating in a 
slightly outwardly curved hook portion 31. From FIG. 2, it may be seen 
that when the closure fastening device is in an occluded position, hook 
portion 25' of closure element 21 and hook portion 30 of closure element 
26 are interlocked, while arm portion 29 and hook portion 31 of closure 
element 26 are in contact with hook portion 25 of closure element 21. It 
can also be seen from FIG. 2 that arm portion 29' terminating in inwardly 
curved hook portion 30 is adapted to engage in a hinging contact with arm 
portion 24' terminating in outwardly curving hook portion 25', and arm 
portion 24 terminating in outwardly curving hook portion 25 is adapted to 
engage in a clamping contact with arm portion 29 terminating in outwardly 
curved hook portion 31. It can further be seen from FIG. 2 that closure 
element 21 and closure element 26 form an overlapping type of occlusion 
wherein hook portion 30 of closure element 26 overlaps hook portion 25' of 
closure element 21, and arm portion 29 and hook portion 31 of closure 
element 26 overlap hook portion 25 of closure element 21. When thus 
occluded, arm portion 29 and hook portion 31 of closure element 26, and 
hook portion 25 of closure element 21, together form an easily 
disengagable structure, while hook portion 30 of closure element 26 and 
hook portion 25' of closure element 21 form a hinge structure which is 
strongly resistant to deocclusion without considerable rotation. 
FIG. 3 is a free body diagram showing a cross-sectional view of the closure 
fastening device shown in FIG. 2. The first closure element 21 shown 
therein is the same as that shown in FIG. 2. However, the second closure 
element 26 has been modified, whereby hook portion 31 may be positioned 
progressively laterally inward, as depicted by alternate hook portion 31' 
and alternate hook portion 31" shown in free body, toward arm portion 24 
of closure element 21 until hook portion 31 makes contact with said arm 
portion 24 or is even deflected outwardly by arm portion 24. When the 
closure fastening device is thus constructed, the successively inward 
curvature of arm portion 29 and hook portion 31 to the positions shown by 
hook portion 31' and hook portion 31" results in gradually increasing the 
opening force required to separate and deocclude closure element 26 and 
closure element 21. It has been found that successively inwardly curving 
hook portion 31 to the position depicted by hook portion 31" results in 
increasing the external opening force required in deoccluding closure 
element 26 and closure element 21 from a force of about 0.5 pound to a 
force of about 2.0 pounds. It was also found that hook portion 31' and 
hook portion 31" result in increased interference between these hook 
portions and hook portion 25, thereby requiring bending of these parts 
during deocclusion of closure element 26 and closure element 21. In 
operation, hook portions 31, 31' and 31" act as a clamp in maintaining 
occlusion of the closure device. By the same token, hook portion 25' and 
hook portion 30 provide a hinge action during deocclusion of closure 
element 26 and closure element 21 whereby hook portion 25' rotates with 
respect to hook portion 30 as shown in FIG. 4. 
FIG. 3-A is a cross-sectional view of the closure fastening device shown in 
FIG. 3 wherein the second closure element is modified pursuant to 
alternate hook portion 31". The typical physical dimensions of a closure 
fastening device in accordance with FIG. 3-A are as follows: 
1. A may be from about 0.050 to about 0.140 inch, preferably about 0.120 
inch; 
2. B may be from about 0.040 to about 0.100 inch, preferably about 0.080 
inch; 
3. C may be from about 0.040 to about 0.100 inch, preferably about 0.080 
inch; 
4. D may be from about 0.007 to about 0.015 inch, preferably about 0.009 
inch; 
5. E may be from about 0.008 to about 0.015 inch, preferably about 0.011 
inch; 
6. F may be from about 0.008 to about 0.015 inch, preferably about 0.013 
inch; 
7. G may be from about 0.008 to about 0.015 inch, preferably about 0.012 
inch; 
8. H may be from about 0.008 to about 0.015 inch, preferably about 0.011 
inch; 
9. I may be from about 0.007 to about 0.012 inch, preferably about 0.008 
inch; 
10. K may be from about 0.008 to about 0.015 inch, preferably about 0.011 
inch; 
11. L may be from about 0.008 to about 0.015 inch, preferably about 0.012 
inch; 
12. M may be from about 0.009 to about 0.020 inch, preferably about 0.017 
inch; 
13. R may be from about 0.050 to about 0.130 inch, preferably about 0.140 
inch; and 
14. S may be from about 0.034 to about 0.224 inch, preferably about 0.116 
inch. 
As indicated in FIG. 3-A, A represents the height dimension of the closure 
fastening device in an occluded position as measured from the apex portion 
of the first closure element to the apex portion of the second closure 
element. 
B represents the height dimension of the second closure element as measured 
from the apex portion of the second closure element to the tip of the 
second arm portion of the second closure element. 
C represents the height dimension of the first closure element as measured 
from the apex portion of the first closure element to the highest part of 
the profile portion of the first closure element. 
R represents the width dimension of the second closure element as measured 
from the widest part of the first arm portion of the second closure 
element to the widest part of the second arm portion of the second closure 
element. 
S represents the width dimension of the first closure element as measured 
between the tips of the outwardly facing hook portions of the first 
closure element. 
FIG. 4 is a cross-sectional view of the closure fastening device shown in 
FIG. 2 in an occluded position, in a partially deoccluded position, and in 
a deoccluded position. It has been found that during occlusion and 
deocclusion of the closure fastening device of this invention, one or both 
of the closure elements of the fastening device experience a gradual 
rotating or hinging operation spread over a significant length of the 
closure on either side of the point of initial force application. The 
spreading action of this hinging operation reduces stress levels, thereby 
reducing force. During deocclusion of the fastening device, this rotating 
or hinging operation continues until the hook portions of the closure 
elements have disengaged from each other. 
FIG. 4 shows in detail some of the operational steps during deocclusion of 
a closure fastening device as described with respect to FIG. 3 wherein the 
second closure element is modified pursuant to alternate hook portion 31'. 
More specifically, when said closure fastening device is in the occluded 
position, hook portion 31' of closure element 26 is in contact with arm 
portion 24 of closure element 21, or hook portion 25 of closure element 21 
is in contact with arm portion 29 of closure element 26. Typically, for 
deocclusion of the closure fastening device, an external release force is 
exerted on hook portion 31' and arm portion 29 of closure element 26, and 
on hook portion 25 and arm portion 24 of closure element 21, to cause 
release of hook portion 31' and arm portion 29 of closure element 26, from 
hook portion 25 and arm portion 24 of closure element 21. The 
afore-mentioned parts of the fastening device are rotated over an arc of 
about 35.degree. C. to a position generally designated as A, as shown by 
the arrows in FIG. 4. In order to obtain full release of the closure 
elements and deocclusion of the fastening device, rotation of the closure 
elements is continued over an arc of between about 100.degree. C. and 
120.degree. C. to a position generally designated as B, as shown by the 
arrows in FIG. 4. During the continued rotation, arm portion 24' and hook 
portion 25' of closure element 21, disengage from hook portion 30 of 
closure element 26, while rotating around hook portion 30 of closure 
element 26 until the parts are separated from each other. 
If a closure fastening device is preferred requiring a smaller arc of 
rotation resulting in earlier deocclusion of the closure elements, then 
closure element 21 and closure element 26 may be modified as described 
with respect to FIG. 5. In FIG. 5 is shown the closure elements described 
with respect to FIG. 4 with the following modifications having been made 
thereto. More particularly, the inside radius of curvature of hook portion 
30 is decreased. During deocclusion of the closure fastening device, after 
hook portion 31' and arm portion 29 of closure element 26 are released 
from hook portion 25 and arm portion 24 of closure element 21, continued 
rotation of the closure elements results in hook portion 30 of closure 
element 26 having a camming or leverage effect upon arm portion 24' and 
hook portion 25' of closure element 21 to provide release of these parts 
at an arc of about 75.degree. . The contact point between hook portion 30 
of closure element 26 and arm portion 24' of closure element 21 is 
generally designated in FIG. 5 as point L, and the contact point between 
hook portion 30 of closure element 26 and hook portion 25' of closure 
element 21 is generally shown therein as point M. It has been found that 
the aforedescribed closure elements provide deocclusion of the occluded 
fastening device more quickly by requiring a lesser amount of rotation of 
the closure elements without affecting good occlusion. 
It should be noted at this point that the actions discussed and illustrated 
for deocclusion apply in the reverse order to occlusion, which re-engages 
the hook elements forming the hinge structure, releases torsionally 
rotated elements and, by further movement, re-establishes the clamping 
action. This is predicated upon portions of the closure being maintained 
in an occluded position at the terminal ends of the closure device. Such a 
condition exists when a length of such a closure device is incorporated in 
a plastic bag having sealed side edges. 
FIG. 6 is a cross-sectional view of another embodiment of the closure 
fastening device in accordance with this invention in a deoccluded 
position. As shown therein, the closure fastening device includes a first 
closure element 40 having a general omega shape, and comprises a generally 
flat or slightly arcuate apex portion 41 and a profile portion extending 
from the apex portion. The profile portion comprises two inwardly curved 
arm portions 42 and 42', respectively, with arm portions 43 and 43' 
outwardly extending from said inwardly curved arm portions, respectively, 
and with said outwardly extending arm portions terminating in outwardly 
curving hook portions 44 and 44', respectively. The closure fastening 
device includes a second closure element 45 having a generally flat or 
slightly arcuate apex portion 46 and a profile portion extending from said 
apex portion. The profile portion of said second closure element comprises 
one inwardly curved arm portion 47 terminating in an inwardly curved hook 
portion 48, and one generally straight arm portion 49 extending in a 
generally perpendicular direction from said apex portion. 
FIG. 7 is a cross-sectional view of the closure fastening device described 
with respect to FIG. 6, but shown herein in an occluded position. It can 
be seen from FIG. 7 that when the instant closure fastening device is in 
an occluded position, arm portion 49 of closure element 45 is located 
between and in contact with outwardly extending arm portions 43 and 43' of 
closure element 40, and hook portion 44 of closure element 40 is 
interlocked with hook portion 48 of closure element 45. It can also be 
seen from FIG. 7 that arm portion 43 terminating in outwardly curving hook 
portion 44 is adapted to engage in a hinging contact with arm portion 47 
terminating in inwardly curved hook portion 48, and arm portion 49 is 
adapted to engage in a clamping contact with either arm portion 43 or arm 
portion 43', or both arm portion 43 and arm portion 43', but in any event, 
with at least one of said arm portions. When this closure fastening device 
is employed with a container, hook portion 44' and arm portion 49 are 
preferably located toward the outside portion of the container, and hook 
portion 44 and hook portion 48 are located toward the inside portion of 
the container. When thus located on a container, the closure fastening 
device of this invention provides a fastening device which is relatively 
easy to deocclude or open from the outside of the container even though 
the closure device is made from high flexural modulus materials and the 
device is used in a low temperature environment such as a freezer, but 
which is relatively difficult to deocclude or open from the inside of the 
container. Accordingly, when thus employed on a container, the closure 
fastening device provides easy access to the contents of the container, 
and also provides improved security to contents stored in said container. 
FIG. 8 is a cross-sectional view of the closure fastening device shown in 
FIG. 7 in a partially deoccluded position such as during deocclusion of 
the fastening device. It may be seen from FIG. 8 that during deocclusion 
of closure element 45 and closure element 40, arm portions 43 and 43' of 
closure element 40 first separate from arm portion 49 of closure element 
45. As closure element 40 and closure element 45 are further rotated with 
respect to each other for separation, hook portion 44 of closure element 
40 will rotate around and then slip away from hook portion 48 of closure 
element 45, thereby resulting in their separation and in the complete 
deocclusion of the closure fastening device. 
Some of the preferred closure fastening devices of this invention were 
evaluated for opening loads for comparison with several commercial plastic 
container products having a closure fastening device. In all the 
evaluations, each occluded closure fastening device was cut into a six 
inch long sample. The closure fastening device samples were tested by 
attaching a piece of one inch wide scotch tape doubled over to grip the 
inside and/or outside flange portions of the fastening device. Each sample 
was tested independently as described herein. The male portion of the 
closure fastening device was mounted in the upper jaw, and the female 
portion of the closure fastening device was mounted in the lower jaw, of 
an Instron.RTM. tensile tester. The force required to deocclude the 
closure fastening device was recorded on a strip chart recorder as the 
maximum force registered. The average value was listed as the average of 
five test specimens and it was recorded as release force. The jaw 
separation (deocclusion ) rate was 20 inches per minute and the full scale 
load was 20 pounds. Each of 5 identical samples was reoccluded and 
retested for a total of 5 tests. The value reported was thus the average 
of 25 tests for each sample. 
The Instron instrument was a tensile tester Model No. 1130, using a "B" 
load cell with a zero to 20 pound range. The Instron tester is initially 
calibrated in the following manner. The pen and chart recorder are turned 
on. The zero button is pressed and held, and the zero adjust knob is 
positioned for a 0.00 reading on the recorder. The zero button is then 
released. The range switch is then turned to the setting of 1 on its 1, 2, 
5, 10, 20 scale. The coarse balance control is turned so that if the pen 
is all the way over to the left, it starts coming towards zero on the 
right. The coarse balance control is left at this position. Then the fine 
balance control is turned so that the pen is at a setting of 0.00. A 20 
pound weight is placed in the upper jaw of the Instron instrument and the 
calibration control is adjusted for a full-scale recorder reading. After 
removing the weight, the recorder should again read 0.00. The zero button 
is pressed and held, and the recorder should again read 0.00. 
Sample 1 represents a closure fastening device employed with a container 
available from Dow Chemical Company, Midland, Mich. under the Tradename 
ZIPLOC.RTM.. The closure fastening device is believed to have been made 
with low density polyethylene having a density of about 0.921 grams per 
cubic centimeter. 
Sample 2 represents a closure fastening device employed with a container 
available from Dow Chemical Company, Midland, Mich. under the tradename 
ZIPLOC.RTM. Microfreez. 
Sample 3 represents a closure fastening device produced by Union Carbide 
Corporation and commercially available with a container identified as SNAP 
LOCK.RTM.. The closure fastening device was made with low density 
polyethylene, that is, having a density of about 0.923 grams per cubic 
centimeter. 
Sample 4 represents a closure fastening device prepared in accordance with 
this invention and as described herein with respect to FIG. 3, wherein the 
second closure element was modified pursuant to alternate hook portion 
31'. 
Sample 5 represents a closure fastening device prepared in accordance with 
this invention and as described herein with respect to FIG. 3, wherein the 
second closure element was modified pursuant to alternate hook portion 
31". 
The closure fastening devices of sample 4 and sample 5 were made with a 
thermoplastic resin composition comprising about 84 percent by weight of 
polypropylene homopolymer, about 15 percent by weight of an 
ethylene-propylene-diene monomer elastomer, and about 1 percent by weight 
of a slip agent, all weight percentages being based on the weight of the 
fastening device. 
Both external release forces and internal release forces were recorded. By 
external release forces is meant the forces required to deocclude the 
closure fastening device from the outside portion of a container. By 
internal release forces is meant the forces required to deocclude the 
closure fastening device from the inside portion of a container. 
The test results are given below in Table 1. 
TABLE 1 
______________________________________ 
Release Force (lbs) Force Ratio 
Sample Internal External (Internal:External) 
______________________________________ 
1 3.8 1.5 2.5:1.0 
2 3.3 1.6 2.1:1.0 
3 4.5 2.5 1.8:1.0 
4 10.0 0.5 20.0:1.0 
5 12.0 2.0 6.0:1.0 
______________________________________ 
From the above results in Table 1, it can be seen that the closure 
fastening devices of this invention, i.e., samples 4 and 5, provide 
internal release resistance forces which are between two and three times 
as high as those of some commercial closure fastening devices, while 
manipulative external deocclusion forces may be held to a minimum, thereby 
providing easy and gentle deocclusion of the closure fastening devices of 
this invention. Further, the external deocclusion forces of the closure 
devices of samples 4 and 5 were low despite the fact that they were made 
from a high flexural modulus material, i.e., polypropylene homopolymer, 
while the closure devices of samples 1, 2, and 3 were made from a 
relatively low flexural modulus material, i.e., polyethylene 
Nine resin materials were evaluated for use in the closure fastening 
devices of this invention. These materials were evaluated to compare 
polypropylene materials having a high melting point and a high flexural 
modulus to measure closure deocclusion forces required and their thermal 
stability. Resin material no. 1 (Shell 5225) was a polypropylene 
homopolymer having a flexural modulus of about 190,000 psi, a flow index 
of about 0.6 gram/10 minutes, and a melting point of about 325.degree. F. 
Resin material no. 2 (Shell DX 6020) was a poly(propylene-ethylene) random 
copolymer having a flexural modulus of about 110,000, a flow index of 
about 2.0 grams/10 minutes, and a melting point of at least 270.degree. F. 
Resin material no. 3 (Cosden Dypro K-122) was a poly(propylene-ethylene) 
random copolymer having a flexural modulus of about 120,000, a melt index 
of about 1.5 grams/10 minutes, and a melting point of about 297.degree. F. 
Resin material no. 4 (Cosden Dypro W-431) was a poly(propylene-ethylene) 
random copolymer having a flow index of about 3.0 grams/10 minutes, and a 
melting point of about 275.degree. F. Resin material no. 5 (Norchem 7300 
GF) was a poly(propylene-ethylene) random copolymer having a flexural 
modulus of about 120,000 and a flow index of about 2.0 grams/ 10 minutes. 
Resin material no. 6 (Norchem 1510 LC) was a poly(propylene-ethylene) 
random copolymer having a flexural modulus of about 120,000, a flow index 
of about 1.0 gram/10 minutes, and a melting point of about 330.degree. F. 
Resin material no. 7 (Cosden Dypro X-7350) was a poly(propylene-ethylene) 
random copolymer having a flexural modulus of about 75,000, a flow index 
of about 1.5 grams/10 minutes, and a melting point of about 264.degree. F. 
Resin material no. 8 (Himont SA-752) was a poly(propylene-ethylene) random 
copolymer having a flexural modulus of about 132,000, a flow index of 
about 3.0 grams/10 minutes, and a melting point of about 275.degree. F. 
Resin material no. 9 (Himont SA-861) was a polypropylene block copolymer 
having a flexural modulus of about 120,000 psi, a flow index of about 7.0 
grams/10 minutes, and a melting point of about 315.degree. F. 
After extrusion into closure fastening devices having the structural 
configuration of FIG. 2, the resin materials were evaluated for opening 
forces required from the outside and from the inside of a container, and 
also for peel force. Peel force is a measure of the force required to pull 
the two closure elements apart after they have been partially deoccluded 
to form an initial opening in the closure device. A high peel force is 
desirable to enable opening a container only to a small extent. Such a 
small opening can act as a vent to either squeeze the air out of the 
container before freezing, or let steam escape from the container during 
cooking. The peel force is measured by placing a partially opened closure 
device in the jaws of a tensile tester available from Instron Corp., 
Canton, Mass., with the first closure element in one jaw and the second 
closure element in the other jaw. The tensile tester pulls the two closure 
elements apart at a speed of about 20 inches per minute, and the peel 
force of the closure device is measured. These results are tabulated in 
Table 2 which follows. In addition, the resin materials were evaluated for 
heat resistance in a boiling water test, as well as for shrinkage and 
general appearance. In this test, six-inch long samples are placed in 
boiling water for about 30 minutes. These results are tabulated in Table 3 
which follows. The resin materials were further evaluated for heat 
resistance in a hot oil bath test at 250.degree. F. and 300.degree. F. and 
shrinkage measurements were taken. In this test, seven-inch long samples 
are placed in the hot oil batch for about three minutes. The results of 
this test are shown in Table 4 which follows. 
TABLE 2 
______________________________________ 
Opening Forces, 
Resin Pounds, Mean Peel Force, 
Material Outside Inside Grams, Mean 
______________________________________ 
1 2.0 12.0 70 
2 4.2 4.6 52 
3 7.9 3.0 73 
4 2.1 11.3 32 
5 0.9 3.5 14 
6 1.7 5.8 27 
7 3.6 9.1 67 
8 1.2 12.3 14 
9 1.3 9.5 19 
______________________________________ 
TABLE 3 
______________________________________ 
Water Boil Test 
Resin 
Material Shrinkage* 
Appearance 
______________________________________ 
1 0 by 0 Good 
2 0 by 0 Good 
3 0 by 1 Good 
4 8 by 4 Good 
5 Not tested 
Not tested 
6 5 by 1 Good 
7 0 by 1 Poor 
8 Not tested 
Not tested 
9 0 by 0 Small waves in 
flange portion 
______________________________________ 
*Shrinkage values are dimensions in length by width measured in 64ths of 
one inch. 
TABLE 4 
______________________________________ 
Hot Oil Bath Test 
Resin Shrinkage* 
Material 250.degree. F. 
300.degree. F 
______________________________________ 
1 4.0 8.7 
2 0.0 31.0 
3 2.7 24.0 
4 4.7 destroyed 
5 not tested 
not tested 
6 4.0 8.5 
7 19.5 destroyed 
8 2.7 10.0 
9 0.0 15.2 
Ziploc 4.0.sup.(1) 
12.3.sup.(2) 
Microfreeze 
______________________________________ 
*Shrinkage values are length dimensions only measured in 64ths of one 
inch. 
.sup.(1) The closure profiles sealed together. 
.sup.(2) The closure profiles and flange Portions sealed together. 
From the preceding test results, it was determined that resin materials 1, 
6, and 9 unexpectedly possessed preferred properties in terms of closure 
opening forces and thermal stability required for the closure fastening 
devices of this invention. In addition, it was found that these resin 
materials had excellent extrudability, and also laminated well to the film 
material employed to make the food containers. 
It has further been found that the closure fastening devices of this 
invention are particularly suitable for use with a container for food, 
wherein the container is employed to store food in a freezer, and 
subsequently placed in a cooking vessel, such as a pot containing boiling 
water, or placed in a microwave oven for cooking the food. Significantly, 
the closure fastening devices of this invention have high resistance to 
heat, while possessing satisfactory low temperature flexing properties. 
Further, some of the preferred closure fastening devices of this invention 
were evaluated for end-use application along with a commercial container 
available from Dow Chemical Company, Midland, Mich., under the tradename 
Ziploc.RTM. Microfreez bags. The closure fastening devices of this 
invention were laminated to a multilayer film to provide a series of 
containers. The containers were evaluated in a microwave oven by placing 
food in the containers and cooking the food for a time sufficient to raise 
the temperature of the food to about 300.degree. F. Generally, speaking, 
it was found that the closure fastening devices of this invention were 
still intact when the containers were removed from the microwave oven and 
had only minimal distortion. However, the closure fastening device of the 
Ziploc.RTM. Mocrofreez bag, believed to be made from low density 
polyethylene having a melting point of about 220.degree. F., melted during 
this cooking test even though food did not contact the closure fastening 
device. The Ziploc closure device was not functional after the cooking 
test. 
In addition, the following closure fastening device compositions were 
evaluated. Test composition No. 1 consisted of a blend of about 90 parts 
by weight of a polypropylene homopolymer (Shell 5225) having a flexural 
modulus of about 190,000 psi, a melt index of about 0.6 gram/10 minutes, 
and a melting point of about 325.degree. F., and about 10 parts by weight 
of a polybutylene copolymer containing up to about 5 percent by weight of 
ethylene (Shell 8640) wherein the blend was employed for the flange 
portion of the closure device. The profile portion of the closure device 
was made with a poly(propylene-ethylene) copolymer (Himont SA-861) having 
a melt flow rate of about 7 decigrams/minute, and a tensile modulus of 
between 90,000 and 95,000 psi. In addition, the poly(propylene-ethylene) 
copolymer employed to make the profile portion contained about 800 ppm of 
erucamide as a slip agent. This combination of resin materials was found 
to have good temperature tolerance at both hot and cold temperatures, as 
well as providing satisfactory opening and peel forces to the instant 
closure fastening devices. 
In addition to its use with a container, the closure fastening device can 
be used to electrically insulate wire leads or bind together a group of 
wires. The closure device can also be used as a flexible straw because a 
good seal at the engaged surface is possible and the compartment defined 
by the elements provides a passageway which does not collapse when the 
closure fastening device is bent. 
Generally, the closure device of the invention can be manufactured in a 
variety of forms to suit the intended use. In addition to the embodiments 
shown herein the elements can be positioned on opposite sides of a film. 
Such an embodiment would be suited for enwrapping an object or a 
collection of objects such as wires. Generally, the elements on a film 
should be parallel to each other but this would depend on the intended 
use. 
Although the present invention has been described and set forth in some 
detail, it should be further understood that the same is susceptible to 
changes, modifications and variations without departing from the scope and 
spirit of the invention as set forth in the appended claims. That is, 
although emphasis has been given herein to describing specific structures 
of a closure fastening device, it should be understood that the resin 
materials of this invention may be employed to make other closure 
fastening devices having any suitable configuration or structure. Such 
changes, modifications and variations are within the scope of this 
invention.