US2354855A

US2354855A - Container closure

Info

Publication number: US2354855A
Application number: US407957A
Authority: US
Inventors: Emanuel Edward Cornell
Original assignee: Armstrong Cork Co
Current assignee: Armstrong World Industries Inc
Priority date: 1941-08-22
Filing date: 1941-08-22
Publication date: 1944-08-01
Anticipated expiration: 1961-08-01
Also published as: GB560713A

Description

E. c. EMANUEL 2,354,855

CONTAINER CLOSURE Aug. l, 1944.

Filed Aug. 22, 1941 .ZI-7 E f'd/wara/ Corne// f'manue/ @MAW Patented Aug. 1, 1944 CONTAINER cLosUaE Edward Cornell Emanuel, Lancaster, Pa., assigner to Armstrong Cork Company, Lancaster, Pa., acorporation of Pennsylvania 'Application August 2z, 1941, serial No. 407,957

claims. (ci. 21a-4o) This invention or discovery relates to closures and, more particularly, to container closures having an improved liner therein; and it comprises i a container closure having a liner which includes an exposed surface of vinylidene chloride resin, all as more fully hereinafter set forth and as claimed.

In all types of container closures, whether they be of metal, rubber or synthetic resins, or whether they be cap type or screw type, it is essential that there be a liner of some material interposed between the inner surface ofthe closure shell and the container itself. The purpose of this liner is to effect a tight seal between the closure shell and the container and itsl contents. Such a seal is necessary to protect the contents of the container from atmospheric conditions from without, and to retain in original form the contents of the container and avoidv loss due to evaporation, or other means, and further to prevent contact between the closure shell a'nd the container contents which contact often' causes a chemicall reactionbetween the closure shell and the container contents resulting in damage to both. T hese lining materials therefore must possess certain physical properties such as flexibility and compressibility vwhich are highly desirableso that an effective seal\ may be had between the container. and the closure when pressure is applied to the closure itself. In` addition to these properties of flexibilityand compressibi1ity,.these' closure liners must be free from attack byany of a large number of materials such as acid, alkali, various solvents, or any compositions to be packaged which contain any of these substances in largef or small proportions.

Heretofore, the most widely used! lining material has been cork. This substance is particularly suitable for a liner because it possesses the necessary flexibility and compressibility which must be inherent in any material before it can be considered suitable for a liner of the type described above. However, though possessing the required flexibility, cork liners are by no means free from attack by acids, alkalis,` and many other substances, and because of the porosity ofthe cork, they permit the container. contents to come in contact with the closure shell which. in many cases, results in damage to the closure shell and contamination of the container contents. For these reasons, attempts have been made to substitute other liners in place of cork or to place a protective film over the exposed surface of the cork liner.

replacement for cork for use as a lining material. Such materials are rubber, rubber compositions, and variousv synthetic resins and compositions containing synthetic resins. Lining materials of rubber and compositions containing rubber, a1- though possessing the necessary flexibility and compressibility, are objectionable in that they possess a characteristic odor which is especially disadvantageous when employed in closures for containers of foods, beverages, and pharmaceuticals. Further, these liners are by no means resistant to certain materials such as organic solvents and, in addition, they become highly tacky at elevated temperatures which causes the liner to adhere to the container in war'm weather. Lining materials have been produced from various synthetic resins such as high molecular weight ethylene polymers which have proved to be resistant to a large number of materials but which are economically impractical because of 4the high cost of production and which are, therefore, commercially unavailable.

Among the materials which have been used as a protective-facing film for cork liners have been varioussynthetic resins, for example, those synthetic resins which are marketed under the trade name Viny1ite.." Closure liners containing these resins as a, facing lm offer some improvement in that the resistance of the liner to certain types of compounds is greatly increased, but there still remains a large field of compounds, particularly among the organic solvents, to which facing films ofthe type of Vinylite offer little or no resistance. Therefore, the fields in which this type of liner, that is a liner containing a Vinylite facing nlm, may be employed are fairly limited. lFor example, there are many pharmaceutical preparations which contain organic solvents such as chloroform and the like; closures in which the liner has a facing lm of a Vinylite resin are unsuitable for use in capping containers for such preparations. In addition, such closures containing Vinylite faced liners are inapplicable for capping many chemical preparations because of the poor resistance of the4 facing film to the chemical preparation.

Various materials have been suggested as a rubber, and the like or by cutting a layer of vinylidene chloride resin to the desired shape and thickness. Such a liner may be easily incorporated in closures of all types, such as screw closures, lug closures, friction closures, and closures of the crown type. Such liners possess unusual properties of resistance to the corrosive and destructive effects of all type compositions such as acids, alkalis, salts, solvents and the like.

The vinylidene chloride resins which form the facing films and the liners of my invention may be vinylidene chloride polymers or copolymers of vinylidene chloride monomers with monomers of vinyl compounds such as acrylic acid esters, allyl esters of organic acids, unsaturated esters of chlorinated organic acids, vinyl chloride, and the like.y In thelatter cases, that is where the copolymers of vinylidene chloride are employed as A. facing film or liner, it is advantageous that the vinylidene chloride monomer be in excess. When the copolymer contains over about 40% of the vinyl compound, the facing fllm or liner of my invention is soft and gelatinous and therefore less desirable in that it is not as resistant to pressure as desired. Further, copolymers containing more than 40% vinyl compound are less resistant to the action of solvents, in that as the amount of vinyl compound present in the copolymer increases, the solubility of the compound increases. These liners are, however, included within the scope of my invention for they may be used in closures for containers of materials which do not -fxert an excessive pressure upon the cap and nner, and which do not exhibit excessive solvent action. Copolymers in which the vinyl compound content is less than 40% are excellent lining materials within the scope of my invention. A parfrom the polymerized film is highly important but which is not a solvent for polymeric vinylidene chloride. I

The step of removing the orthodichlorobenzene from the point of view of my invention in that a closure liner must be odorless, and the orthodichlorobenzene imparts a disagreeable odor to the polymer which must be removed. It is more become distorted Lat temperatures in the neighborhood of '100 C. This shrinkage and distortion ticularly advantageous'lining material may be cilitate the manufacture of the lining materials.

An advantageous method of preparing polymeric vinylidene chloride is disclosed in United States Patent 2,160,937 to Reilly. According to this patent, substantially pure monomeric vinylidene chloride is diluted with from 1 to 2 parts by weight of orthodichlorobenzene per part of monomeric vinylidene chloride. 'I'he mixture is then covered with a layer of water, which serves as a sealing agent, and is allowed to stand, with or without agitation, at a temperature between room temperature and about 90 C. until polymerization is substantially complete. The polymerization can be made to progress more rapidly by agitating the mixture. The sealing layer of water is then decanted from the mixture, which is in the form of a gel. The gel is heated to liquefaction temperature, that is, to about 145' C., and is poured out onto a. plane surface, suitably in a lrn casting device, and is thereafter freed from remaining solvent. 'I'he orthodichlorobenzene may be removed from the lm either by blowing a stream of warm air thereover while keeping the temperature of the film at or near 13G-145 C., or by washing the film after part of the inert liquid has been evaporated therefrom, with a solvent such as ether, alcohol, acetone, chloroform, trichloroethylene, etc., or mixtures of these solvents. Any solvent mayloev used which is miscible with orthodichlorobenzene may be due to relief of strains imparted to the polymer during the formation of the lnis. Although, this shrinkage or distortion is somewhat insignificant in manyiields, it is highly important in the liner field due to the high requirements of flexibility and compressibility that are set upon lining materials. Further, a distorted film cannot be properly adhered to a backing layer. For these reasons, any step in the preparation of the vinylidene chloride polymeric lms which would tend to cause even the slightest distortion of the lm should be avoided, and therefore the solvent method of removing the odoriferous orthodichlorobenzene from the polymeric lm is more desirable.

I have found that the most advantageous method of deodorizing the vinylidene chloride polymer is to immerse the polymeric lm in one ofthe above mentioned solvents for a period of more than about 2 minutes. It is advantageous that the solvent be of a volatile nature so that any solvent adhering to the polymer may be easily removed by warming at low temperatures. A shorter immersion period may be used but the resulting Washed film still possesses a slight odor.

Following this immersion the lm is removed andv warmed at temperatures of less than 50 C. to rid the lm of the adhering solvent. Should tembe unsuitable for incorporation into a closurel liner as a facing lm.

I'he copolymers of vinylidene chloride and vinyl compounds may be prepared by heating together a mixture of the copolymen'zable materials at temperatures from about room temperature up to about 100 C. Suitable catalysts may be employed to expedite the reaction such as tetraethyl lead, poly-halo phenols, and organic peroxides, for example, benzoyl peroxide.

These films of vinylidene chloride resins may be adhered to any suitable backing such as cork, paper or felt to form a closure liner which is essentially all-purpose in its nature. A relatively thick. and compressible sheet of vinylidene chloride resin may be prepared in a manner similar to that outlined above for the preparation of lfilms. From this sheet liners may be cut and inserted in a closure without the need of backing are essential characteristics of liners for, food container closures.

To these' vinylidene chloride resins may be added certain plasticizers such as the methallyl 2,354,855 lemen: ef pnenyiphenols. 'maandloon er these plasticizers increases the workability of the resins and thereby assists in the preparation of the nners er-my invention. Further., the 'addition of plasticizers makes the vinylidene'chloride resins more nexible and hence more apt to take up any for the liner to lose its cushion-like characteristics. and etfective sealing may not be obtained. A liner having a greater or lesser thickness may be employed within the scope of my invention,

butV more advantageous results are obtained when the'llner thickness is in the above disclosed range.

. v Also within the scope of my invention is a liner in which a iilm of vinylidene chloride resin is united .to both sides of a compressible backing material. A liner having such a structure is v particularly advantageous for use in high speed of 4-tert-butyl-Z-phenylphenol, the 2-methallyl ethers of A 2,4-dichloro-ii-phenylphenol, 4-bromo- -phenylphenol, Z-chloro-i-tert-butyl-6-phenylphenol, 4-iodo 6 phenylphenol, 2chloro4 phenylphenol, 222,6 trichloro-4-phenylphenol, 4 sec-butyl 6 phenylphenol, 4-oyclohexyl-6- phenylphenol, 2,6 dimethyl 5 phenylphenol. These plasticizers when added should be added in very small amounts for the vinylidene chloride resins are compatible with but few plasticizers and then only when these plasticizers are added in small portions. e

By the term "vinylidene chloride resins as used throughout this specificationl and the appended claims I mean to includethose resins prepared by the polymerization of vinylidene chloride monomers alone and those resins prepared bythe copolymerization of vinylidene chloride monomers and small amounts of vinyl compounds in monomeric form.' These resins are well known in the chemical arts and may be clearly defined by the term "vinylidene chloride resins. This term is also meant to include resins containing plasticizers and pigments which are known to be capable of incorporation with the vinylidene chloride resins, and which upon incorporationl with the resins do not cause any odor or taste in the lining material which cannot be easily removed before the liner is positioned .in the closure.

The liners of my invention may be prepared in the following manner: The vinylidene chloride resin may be cut to the desired size and shape from extruded rods, sheets or ribbons and adhered by means of a suitable adhesive such as rubber cement, synthetic resinous cement and the like directly to a relatively thick and compressible substance such as cork, cork composition, rubber, rubber composition, pulpboard. newsboard, kraft paper, cotton linter blotting paper, felt and the like. The liners thus prepared are inserted in the closure by any means known to the art.

A liner of vinylidene chloride resin without any backing material is also within the scope of my invention. These liners may be prepared in any suitable manner such as extruding a relatively thick layer of vinylidene chloride resin and punching a liner of the desired shape from the .preformed sheet. These liners may be adheredby means of a suitable adhesive to the inner surface of the closure shell. In the case of these unbacked vinylidene chloride resin liners, it is necessary that the resin sheet from which the liners are cut b e relatively thick so that the liner will possess the cushion-like characteristics necessary in the art. An unbacked liner of vinylidene chloride resin is advantageously about 0.020 inch to about 0.0'75inch in thickness. A liner having such a thickness has been found to exhibit the necessary compressibility and fiexibility and cushion-like qualities which must be inherent in a closure liner. If a liner thinner than 0.020 inch is employed, there is a tendency machinery in that it is unnecessary to carefully feed the liners to the pressure exerting mechanism as is the case when a liner is faced on only 4one surface and requires great care in the feeding 4step to assure that the liner will be positioned in the cap with the faced surface exposed.

In the most advantageous modification of my invention a film of vinylidene chloride resin of the desired thickness is adhered to a relatively thin reinforcing layer such as paper, for example, white sulflte paper, .kraft paper, and the like, Cellophane, metal foil,l and thel like by means of a suitable adhesive. The reinforcing layer is advantageously paper because of its cheapness, and the 'fact that itis more easily handled and is more readily united to the vinylidene chloride resin film.` Further, it possesses a-higher degree of toughness which aids its reinforcing action.

The duplex sheet thus formed is then adhered to a suitable compressible substance, which is advantageously cork, by means of any adhesive known to the liner art. A three-ply liner possesses an advantage over a two-ply liner in that the facing iilm of vinylidene chloride resin remains flat, and is adhered to the intermediated layer at every portion of its inner surface. It is not distorted by the rough surface of the backing material and it is less likely to become detached from the backing material because of poor adhesion brought about -by failure to adhesively contact the indentations of the backing layer.

By the term a relatively thin reinforcing layer as used in the specication and appended claims is meant a layer or sheet of flexible material having a thickness of about 0.001 inch to about 0.004 inch used to reinforce the vinylidene chloride resin film. When metal foils such as aluminum foil, tin foil, and the like are employed as a reinforcing material the layer or sheet may be as thin as 0.0005 inch.

In lieu of the use of an adhesive in the preperation of a paper-vinylidene chloride resin duplex layer, the film of vinylidene chloride resin may be calendered directly to the sheet of paper. However, because of the thinness of the' resin lm, which ordinarily varies from about 0.0012 inch to about 0.0025 inch in thickness, great care must be taken in the calendering operation for should a filament of the paper be in an upright position, it may puncture the resin film causing what is known to the art as a pin hole and thereby reduce its value as a lining material.

'I'he resin film may possess a greater or lesser thickness than about 0.00.12 inch to about 0.0025 inch and still be within the scope of my invention. However, a facing film much thinner than 0.0012 inch is very diflicult to handle and apply to the backing material. Should the film be thicker than 0.0025" inch, an unnecessary expense would be added to the production of the lining material, for the sealing properties are not improved by thick iilms, and thick facing films are undesirablefor use with lining machinery. It should be understood, therefore, that the term facing film as used in this specification and the appended claims is meant to include a relatively thin film of sheet material which is exposed to the contents of the container when a closure having the liner of my invention is in place on a. container. The film may cover` the entire surface of the backing material or may be of smaller diameter; i. e., in the form of a spot.

Closures containing liners having facing films of a vinylidene chloride resin have been sub- Jected to strenuous tests to determine how well they stand up under various types of solutions. The liners were punched in the 28 mm. size and liner tests were conducted for forty-eight hours at 120 F. using one-ounce bottles and 28 mm. caps with the liner inserted. The caps were applied using 33 pounds tangential force, and the samples were inverted during the period of test exposure. The liners of my invention were found to hold up under subjection to concentrated acids and alkalis, organic solvents and various pharmaceutical preparations such as tincture of iodine, mercurochrome, milk of magnesia, Listerine, Teel and the like. In all cases neither the liner nor the solution was noticeably attacked. In addition to the above disclosed corrosion resistancel my liners possess remarkable properties of iiexibility and compressibility which are highly desirable. When pressure is applied to either a screw cap or crown cap the pressure is transmitted through the cap to the liner which must be both fiexible and compressible to effect a tight seal which is necessary to protect the container contents from deterioration. The liner must be able to withstand this application pressure and in addition, any pressure to which it might be `subjected because of the nature of the container contents. My liners have been found to withstand carbonation pressures of 115 pounds per square inch or more. Such pressures are greatly in excess of any pressure to which a liner would be subjected under ordinary conditions. The liners which constitute my discovery are, therefore, suitable for use in closures for containers of lpressure foods and beverages such asr carbonated beverages, ,for example, soft drinks,

beers and the like.

Although any of the adhesives known to the liner art may be used in adhering the vinylidene chloride resin film to both the backing material and the intermediate reinforcing layer, I have found that a particularly desirable liner is ob.-

tained when a semi-pressure sensitive adhesive is used. By semi-pressure sensitive adhesive is meant an adhesive which develops sufficient tack upon the application of pressure to cause slight adhesion between two bodies, and then upon application of heatcauses excellent adhesion. The use of a semi-pressure sensitive adhesive greatly lessens the danger of distortion of the vinylidene chloride resin film during the step of adhering the lm to the backing material and to the reinforcing layer, for there is sufiicient adhesion developed between the backing and/or reinforcing layer and vinylidene chloride resin film upon application of pressure or the application of pressure at slightly elevated temperatures so that upon application of heat there is a sufficient reinforcement' by the backingmaterial and/or reinforcing layer to prevent any distortion of the film.

f the semi-pressure sensitive adhesives, a composition comprising polyisobutylene, hydrogenated rosin and terpene polymer is very suitable for use in adhering the vinylidene chloride resin films to the backing material and to the intermediate paperlayer.

I have found that a composition comprising 25-30% by weight polyisobutylene, Zio-35% by weight hydrogenated rosin and 30-35% by weight of a terpene polymer such as polymerized dipentene, polymerized pinene, polymerized turpentine and the like, is particularly suitable for use in adhering the vinylidene chloride resin films to the backing material and to the intermediate paper layer. This adhesive may include small amounts of fillers such as zinc oxide. When this adhesive is used, the vinylidene chloride resin films are in excellent.A adhesion with the backing material or the intermediate layer, and there is no leakage through or tearing of the facing lm because of any distortion thereof during the manufacture of the liner.

The liners of my invention are suitable for use in crown caps or screw type closures. They may be used in metal or resinous closures, may be cut to any desired size or shape, and may comprise a layer of unbacked vinylidene chloride resin or may comprise anyfnumber of layers of material aslong as the base material is a relatively thick and compressible substance and the facing film is vinylidene chloride resin. Because of the remarkable properties exhibited, by the liners of my invention, they may be successfully employed in closures for containers for all types of substances, for example, pharmaceutical preparations, foods, beverages, chemicals and the like. In short, the liners of my invention are not limited to closures of any specific design, make-up or material. By way of example, but not by limitation, there are shown in the accompanying drawing various embodiments of my invention.

In the drawing, in which like parts are represented by like numerals,

Figure 1 represents a sheet of my lining material having three plies;

Figure 2 represents a two-ply sheet of my lining material;

Figures 3 and 4 are sectional views taken on the lines III-III and IV-IV of Figures 1 and 2 respectively;

Figure 5 represents in elevation a liner in which a film of vinylidene chloride resin is united to both sides yof a relatively thick and compressible material;

Figure 6 is a front sectional view of a molded screw type cap containing the liner of my invention;

Figure 7 is a front sectional view of a metallic lug type cap containing the liner of my invention;

Figure 8 is a view in front section showing the liner of my invention disposed in a metallic crown cap;

Figure 9 is a bottom plan view of a crown cap in [which the facing lm of my liner is in the form of a spot; and

Figure 10 illustrates a crown cap having an unbacked liner of vinylidene chloride resin.

Referring more particularly to the drawing,

lin Figures 1 and 3 which illustrates an advantag'eou's form of my invention, number IIJ represents a facingfilm of vinylidene chloride resins' which is adhered by means of a semi-pressure sensitive adhesive Il to a sheet of white sulflte' layer of white sulte paper is in turn adhered by means of a suitable adhesive i3 to a relatively thick and compressible material I4 such as cork. Felt, heavy paper, and similar materials may be employed in place of the cork illustrated.

Figures 2 and 4 represent a two-ply liner in which the facing film I of vinylidene chloride resin is directly adhered by a semi-pressure sensitive adhesive Il such as a composition comprising 25-30% by weight polyisobutylene, 30- 35% by weight hydrogenated rosin, and Sil-35% by weight of a terpene polymer to a relatively thick and compressible material I4 such as cork, felt or heavy paper.

Figure 5 illustrates a closure liner in which a film of vinylidene chloride resin l0 is adhered to both sides of a relatively thick and compressible substance I4 such as cork, felt, heavy paper. and the like by means of a semi-pressure sensitive adhesive Il.

Figure 6 illustrates the liner of Figures 1 and 3 in a Vmolded screw type cap. The liner represented by |5 is frictionally held in the cap I1 which may be of any molded plastic such as polystyrene, phenol formaldehyde condensation products and the like. The liner may also be attached to the cap by means of a suitable cement.

Figure 7 represents the liner of Figures l and 3 represented by i5 inserted in lug type metal cap I8.

Figures 8 and 9 show my liner in a crown metal cap. In Figure 8 the liner I5 is attached to the cap I9 by suitable means. In Figure 9 the facing film l0 assumes the form of a spot.

Figure 10 represents an unbacked liner 22 positioned in a crown cap i9.

It can be readily seen that the liners of my invention may be cut to any desired shape, such as a circle, hexagon, square, etc. Further, there is no limitation as to the size of the liner for example, they may be of very small size suitable for use in closures for collapsible tubes or they may be of large size suitable for use in Jar closures.

The facing lms of vinylidene chloride resin either reinforced with paper, foil or similar relatively thin material or without any reinforcing material may assume the form of a spot. In the manufacture of closures containing a vinylidene chloride resin facing film which is in the form of a spot, the vinylidene chloride resin may be united by a thin layer of adhesive, which is advantageously a semi-pressure sensitive adhesive, to the reinforcing material which is in turn provided with a suitable adhesive stratum whereby spots formed from the vinylidene chloride resin facing film may be adhered to the cushion-like base material in the cap. The strips or sheets thus formed have the desired overall thinness and may be satisfactorily fed by high speed spotting machines. A sheet of vinylidene chloride resin of suitable thinness may be coated with a semi-pressure sensitive adhesive, cut to discs of the desired diameter and adhered directly to the cushion-like liner to form a spot of vinylidene chloride resin, or the sheet may be first cut into ribbons from which discs of the desired diameter may be punched and united to thelcushion-like liner in the cap. f

I claim:

l. A container closure including a sealing element comprising a base of relatively thick and compressible material and a facing film of vinylidene chloride resin adhered to said base by means of an adhesive comprising polyisobutylene, hydrogenated rosin, and a terpene polymer.

`2. A container closure including a sealing element comprising a base of relatively thick and compressible material and a facing film of vinylidene chloride resin adhered to said base by means of an adhesive comprising 25-30% by weight polyisobutylene, 30-35% by weight hydrogenated rosin and 30-35% by weight terpene polymer.

3. A container closure including a sealing element comprising a base of relatively thick and compressible material, an intermediate layer of relatively thin reinforcing material and a facing film of a vinylidene chloride resin adhered to said intermediate layer by means of an adhesive comprisingY polyisobutylene, hydrogenated rosin, and a terpene polymer.

4. A container closure including a sealing element comprising a base of relatively thick and compressible material, an intermediate layer of relatively thin reinforcing material and a facing film of a vinylidene chloride resin adhered to said intermediate layer by means of an adhesive comprising 25-30% by weight polyisobutylene, 3035% by weight hydrogenated rosin and Sil-35% by weight terpene polymer.

5. A container closure including a sealing element comprising a base of relatively thick and compressible material, an intermediate layer of paper and a facing film of a vinylidene chloride resin adhered to said intermediate layer by means of an adhesive comprising polyisobutylene, hydrogenated rosin, and a terpene polymer.

EDWARD CORNELL EMANUEL.