US 3310225 A
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March 21, 1967 L. D. HOBLIT 3,310,225
RESEALABLE CONTAINER CLOSURE FROM SELF-ADHERENT CHLORINATED OLEFIN POLYMER FILMS Filed Aug. 6, 1965 Fig/.1
United States Patent RESEALABLE CONTAINER CLOSURE FROM SELF-ADHERENT CHLGRINATED OLEFKW PGLYMER FELMS Louis D. Hoblit and Harold A. Simms, both of Baton Rouge, La., assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed Aug. 6, 1965. Ser. No. 477,714 7 Claims. (Cl. 22962) This invention relates to a novel resealable closure means for containers, and more particularly to containers having opposed strips of self-adhering, inherently flexible chlorinated olefin polymers associated with the open end thereof, as reclosable sealing means.
In the packaging field there has been a long felt need for a resealable package which, when the package has been opened, can be easily resealed and thus function as a container to hold and protect the contents from the deleterious effects of moisture, dirt, foreign particles, and the like. To date, no practical sealing means has been provided to allow for the repeated reclosure of packages.
It has now been discovered, however, that by assocating individual strips of certain self-adhering, inherently flexible chlorinated olefin polymers with the open end of various containers, such as flexible plastic bags or pouches, in a manner whereby the container is in a closed condition when the surfaces of such individual strips are placed in overlying contact, e.g., as illustrated in the accompanying drawing, that resealable structures of greatly increased utility are obtained.
In the drawing:
FIGURE 1 is a perspective view of a pouch embodying the principles of the present invention, such pouch being shown in an opened condition; and
FIGURE 2 is a view of the same pouch in reclosed condition.
Referring now to FIGURES 1 and 2 of the drawing, a conventional bag or pouch is illustrated consisting of front and back walls 11 and 12, respectively, wherein the upper terminal of the back wall is extended to provide a lip or flap 13 adapted for covering the mouth of the bag or pouch. The present invention contemplates the application of an inherently flexible, self-adhering strip 14 of a chlorinated olefin polymer (as hereafter more fully described) along the inner surface of the flap 13 and an opposed strip 15 of similar composition along the margin of the front wall 11 adjacent the mouth of the bag, so that, when the flap is folded over the mouth of the bag and upon the front wall, the strips of self-ad- 'hering chlorinated olefin polymer are brought into releasably sealed contact with one another. It is to be understood, however, that the present invention is not restricted in scope to the pouch or bag structure specially illustrated in FIGURES 1 and 2 but encompasses any such structure utilizing the herein described resealable closing means. Further, the invention is not restricted to the utilization of containers made from flexible materials; but is intended to include containers made from rigid materials such as cardboard and the like.
Exemplary of flexible materials used to form the body portion 10 of the container employed in the present invention are materials which are preferably transparent and have a heat-scalable surface. Suitable materials include the polyolefins such as polyethylene, polypropylene, ethylenepropylene copolymers and similar heat-scalable, film-forming plastic materials such as nitrocellulose, vinylidene chloride polymer coated regenerated cellulose films and vinylidene chloride polymer coated polyester films, and the like, as well as resin coated webs having foil or paper substrates.
Patented Mar. 21, 1967 The individual strips of inherently flexible, self-adhering chlorinated olefin polymers comprising the re sealing means of the present invention are prepared from polymeric material obtained by chlorination of essentially linear finely divided polyethylene or interpolymers containing at least about mole percent of ethylene in the polymer molecule, which polymers have a molecular weight of less than about 1,000,000 and preferably between about 20,000 and 300,000.
More specifically, the preferred chlorinated olefin polymers utilized contain from about 25 and 50, and preferably between about 30 and 40, weight percent of chemically combined chlorine, Particularly preferred chlorinated olefin polymers are those prepared by chlorination in aqueous suspension, which are further characterized by having a relative crystallinity of between about 15 and 28 percent when containing about 25 weight percent chlorine, and a relative crystallinity of less than about 10 percent when containing about 34 Weight percent of chemically combined chlorine. Such preferred chlorinated polyolefins are readily obtained by practice of a chlorination procedure which comprehends the suspension chlorination in an inert medium of finely divided polymers and interpolymers of ethylene to a desired total of combined chlorine content, wherein such polyolefin is first chlorinated at a temperature of up to about C., and preferably between about 65 C. and 110C. for a period suificient to provide a chlorine content of not more than about 23 weight percent chlorine, based on the total weight of the polymer; followed by the sequential suspension chlorination of such polymer, in a substantially non-crystalline, particulate form, at a temperature above that employed for the herein described first chlorination and not more than about C., for a period suflicient to provide a combined chlorine content of between about 25 and 50 weight percent, based on the total weight of the polymer.
Preferably, the polyolefinic materials to be chlorinated are those distinct species and varieties of essentially linear and unbranched highly porous, finely divided polymers containing at least about 90 mole percent ethylene in the polymer molecule with any remainder being one or more ethylenically unsaturated comonomers. EX-
emplary of such comonomers are the non-aromatic hydrocarbon olefins having 3 or more carbon atoms such as propylene, butene-l and butene-2, and 1,7-octadiene and the like, cyclooctadiene and the like; substituted olefins such as acrylic acid and its esters; conjugated diolefins such as butadiene and the like; and the alkenyl aromatic compounds such as styrene and its derivatives, among many other polymerizable materials known to the art.
Advantageously, the polymers and interpolymers, described herein, are prepared under the influence of catalyst systems comprising admixtures of strong reducing agents such as triethyl aluminum and compounds of Groups IV-B, V-B and VI-B metals of the Periodic System, such as titanium tetrachloride, and the like and are characterized by having molecular weights below about 1,000,000 and preferably from about 20,000 to 300,000. It is to be pointed out, however, that conventionally prepared low density, branched polyolefins may also be advantageously chlorinated by the process of the present invention, providing such materials are available in finely comminuted form.
It is further to be pointed out that other ingredients such as pigments, stabilizers, lubricants and the like may be incorporated in the chlorinated olefin polymers, if desired.
Exemplary of particularly useful stabilizers are those materials conventionally employed in the preparation a of vinyl polymer and copolymer film compositions, e.g. organic complexes and/or salts of lead, barium, cadmium, zinc, sodium, etc., and particularly the sulfur containing organo tin compounds including the alkyl tin merca-ptides as well as dibutyl tin maleate, among others.
Although the chlorinated olefin polymers utilized to prepare the reclosable sealing means of the present invention are inherently flexible and self-adhering, it may, in some instances, be desirable to include in such chlo rinated olefin polymer compositions from between about 1 and 15 parts per 100 parts of polymer, of a plasticizing agent to enhance the blocking or self-sealing characteristics of films prepared therefrom, and/or to enhance the ability of such films to adhere, in the absence of adhesives and the like, to the substrate of which the bag or pouch is composed. Suitable plasticizers include those materials conventionally employed for vinyl polymers, e.g. dioctyl phthalate and dibutyl sebacate, among many others known to the art.
Films or strips prepared from such chlorinated olefin polymers have been found to be uniquely self-adherent under normal conditions of temperature and pressure, and may in fact, be firmly but releasably sealed together by application of normal digital pressure, e.g. the manual pressure employed for sealing of a conventional envelope used for the mailing of letters, etc.
Further, the films or strips may be easily applied in essentially non-releasable contact with flexible, heat-sealable surfaces of the materials forming the body of the bag or pouch structures described herein by application thereto under conditions of temperature and pressure normally employed for heat sealing of such materials. Further, when applying the sealing strips described herein to relatively rigid, non-heat-sealable materials, such as cardboard and the like, use may be made of conventional adhesives including organic solvent dispersions of the chlorinated olefin polymers described herein, or other securing means.
By way of example, a chlorinated polyethylene having a chlorine content of about 36 weight percent and a relative crystallinity of about 3.5 percent, was prepared by the chlorination, in aqueous suspension, of an essentially linear polyethylene having a melt index of about 1.0, utilizing the chlorination procedures as hereinbefore specifically described. The so-formed chlorinated polymer was then extruded through a film die having a thickness of about 0.001 of an inch, then cooled without substantial orientation and cut into individual strips about 6 inches in length and about 0.5 of an inch wide. The strips were then joined to a conventional polyethylene pouch, in the positions as illustrated in FIGURES l and 2 of the drawing, by passing the opposed surfaces of the strips and pouch between heating elements operating at a temperature of about 190 (1., wherein such surfaces were subjected to pressures of from about to 75 psi, for periods of from about 1 to 3 minutes. Following application, and after cooling of the film materials, it was found that the chlorinated polyethylene strips could not be manually separated from the polyethylene pouch. It was also found that the pressing together of the opposed surfaces of the chlorinated polyethylene strips, using normal finger pressure, resulted in a firm union which could be easily separated and reclosed many times without loss in sealing eificiency.
It is to be understood that the sealing conditions described herein will vary somewhat according to the nature and composition of the sealing strips and the bag or pouch material employed.
It is to be understood that the foregoing description has been given in detail without thought of limitation, other than as set-forth in the appended claims, since the inventive principles involved are capable of assuming other forms without departing from the spirit or scope of the invention.
What is claimed is:
1. Reclosable sealing means for containers comprising: individual inherently flexible, self-adherent film strips each of which is permanently attached to an external surface of said container, said film strips being formed from an essentially linear chlorinated olefin polymer containing from about 25 to about 50 weight percent of chemically combined chlorine, said film strips being positioned on said container so that the container is in a closed condition when the exposed surfaces of said film strips are in overlying contact.
2. The sealing means of claim 1 wherein said chlorinated olefin polymer is chlorinated polyethylene prepared in aqueous suspension and is characterized by having a relative crystallinity of between about 15 and 28 percent when containing about 25 weight percent chlorine and a relative crystallinity of less than 10 percent when containing about 34 weight percent chlorine.
3. A container having reclosable sealing means thereof, said sealing means comprising: individual inherently flexible, self-adherent film strips each of which is permanently attached to an external surface of said container,
said film strips being formed from an essentially linear chlorinated olefin polymer containing from about 25 to about 50 weight percent of chemically combined chlorine, said film strips being positioned on said container so that the container is in a closed condition when the exposed surfaces of said film strips are in overlying contact.
4. The container of claim 3 wherein said container is a reclosable flexible pouch.
5. The container of claim 4 wherein said reclosable flexible pouch has front and back opposed walls wherein the back wall is extended to provide a sealing flap and wherein at least one film strip is positioned along the inner sealing margin of the flap and at least one film strip is positioned on the front wall adjacent the mouth of the pouch.
6. The container of claim 5 wherein said flexible pouch is a polyethylene pouch and said film strips are formed from chlorinated polyethylene prepared in aqueous suspension and characterized by having a relative crystallinity of between about 15 and 28 percent when containing about 25 weight percent chlorine and a relative crystallinity of less than 10 percent when containing about 34 weight percent chlorine.
7. The container of claim 6 wherein said film strips are in heat-sealed lamination with said polyethylene pouch.
References Cited by the Examiner UNITED STATES PATENTS 2,215,989 9/1940 Wolf 229- 2,536,773 1/1951 Saidel 20641 3,070,280 12/1962 Richmond 229-80 3,154,239 10/1964 Madsen 229-62.
JOSEPH R. LECLAIR, Primary Examiner. DAVID M. BOCKENEK, Examiner.
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