US3390800A - Controlled torque gasket compositions for container closure elements containing a mixture of mineral oil and fatty acid amides - Google Patents

Description

c. w. SIMONS 3,390,800

NS FOR CONTAINER CLOSURE CONTROLLED TORQUE GASKET COMPOSITIO ELEMENTS CONTAINING A MIXTURE 0F MINERAL OIL AND FATTY ACID AMIDES Filed D90. 22, 1965 INVENTOR. 7 CHARLES W. SIMONS ATTORNEY United States Patent CONTROLLED TORQUE GASKET COMPOSITIONS FOR CONTAINER CLOSURE ELEMENTS CON- TAINING A MIXTURE OF MINERAL OIL AND FATTY ACID AMIDES Charles W. Simons, Bedford, Mass., 'assignor to W. R. Grace & Co., Cambridge, Mass., a corporation of Connecticut Filed Dec. 22, 1965, Ser. No. 515,631 6 Claims. (Cl. 215-40) ABSTRACT OF THE DISCLOSURE A gasket-forming composition for rotatable container closures comprising a plasticized vinyl resin which includes an additive composed of white mineral oil and a mixture of fatty acid amides to enhance the removal torque valves of the gasketed closure.

This invention relates to compositions suitable for use as gaskets in rotatable closures. In a particular aspect, it

relates to a vinyl resin sealing composition which includes an additive to endow the resulting gasket with controlled closing and opening torque values.

Rotatable closures are usually made of lacquered tinplate or aluminum and have gained extensive use in protecting and preserving foods in glass containers. To be effective, the closure requires a gasket to easily seal the contained food and it must not include any deleterious substance that might transfer to and contaminate the food. Typical rotatable closures include the screw type and lug type and they differ chiefly in the means by which the closure is held firmly in place on the container. Illustrative means include a continuous or discontinuous thread, projecting lugs, etc., located near the container opening and they are adapted to mate in threaded engagement with the closure as it is rotatably advanced to bring the gasket into sealing relationship with the mouth of the container.

In sealing a jar with a closure, air is generally exhausted from the headspace above the contents in closing machines which produces a vacuum either mechanically or by the condensation of steam. In closing the container, the torque must be sufficient to resist retractive movement during shipment and/or storage to avoid breaking the seal and causing leaks through which spoilage organis'ms can gain access to the contents in the container.

The torque which is required for closure removals on vacuum-packed containers varies widely, but it is well known that some containers, such as baby food jars, have their caps so firmly attached that it is necessary to resort to fairly drastic means to effect their removal. On the other hand, closures may be so loosely attached that only a slight twist is required to remove it from the container. A loosely-fitted closure may be accidentally jarred, causing the seal to be broken and concomitantly therewith result in exposure of the contents to contamination.

In closing certain containers, such as those filled with peanut butter, the standard method is to fill the container with peanut butter at 90 F. and then close the container without applying any vacuum other than that which results from cooling of the pack and absorption of oxygen into the peanut butter. A standard capper which is used includes a shaft, an adjustable clutch and a pad 3,390,800 Patented July 2, 1968 afiixed to the lower end of the shaft. The pad presses into the closure as it is rotated on to the container by the shaft. The clutch is adjusted to a predetermined torque to allow slippage when the closure has been firmly afiixed However, if the gasket will not permit rotation of the closure due to frictional forces between the gasket and the container mouth, the clutch may slip prematurely before the closure is secured and, consequently, the closure will remain loose when the container is moved from the capper.

It is, therefore, an object of this invention to provide a composition which is suitable for use as a gasket in a rotatable closure which assists in applying the closure and has low removal torque requirements but maintains a hermetic seal. This objective is achieved by incorporating into the composition an additive consisting of an admixture of (a) white mineral oil and (b) a mixture of fatty acid amides composed of a major amount of oleyl amide and minor amounts of stearylamide and linoleyl amide. An effective amide mixture consists of 91% oleyl amide, 6% stearyl amide, and 3% linoleyl amide. The mineral oil is a mixture of liquid hydrocarbons composed entirely of saturated aliphatic and naphthenic hydrocarbons. Its specific gravity ranges between about 0.84 to 0.94 at 60 F. The additive consists of 25 to of mineral oil and 75% to 25% of the mixed amides. The preferred admixture consists of 50% by weight of each component. All proportions are expressed on a weight basis.

Closure manufacturers design their gaskets with the prime consideration of preventing accidental dislodgment of the closure. This requires formulation of the gasketforming composition to be somewhat tacky so that the resulting gasket exhibits considerable friction to the closure and the container against rotational torque. But, this is precisely what makes these closures difiicult to open for the average consumer.

In the additive of this invention, the white oil provides lubricity to the gasket to assist application of the closure to the container. As the closure is rotated, the oil migrates out of the gasket and flows to and remains in the corner of the closure. Thus, while it eases closure application it does not interfere with the seal. concomitantly with closure application, the pressure of rotation causes a portion of the mixed amides to exude to the interface. The layer of mixed amides remains at the interface and provides lubrication to assist in removing the closure from the container.

Plastisols are frequently used to form gaskets for closures. These compositions basically comprise a vinyl resin dispersed in a plasticizer in which the resin is insoluble at room temperature but which is capable of solvating the resin at an elevated temperature. The properties of these compositions may be modified by the addition of conventional ingredients, such as fillers, stabilizers, pigments and other additives.

In the drawing:

FIG. 1 is a perspective sectional view showing the application of a gasket-forming composition by means of a nozzle in the peripheral channel of an inverted lugtype closure.

FIG. 2 is a fragmentary vertical sectional view of a closure in sealed relationship with a container.

The closure, shown generally at 10, comprises a circular panel 11 and a skirt 12 depending from the periphery of the panel. A gasket-receiving channel 13- is provided in the perimetrical margin of the panel adjacent 3 the lower edged the skirt. The upper edge of the skirt is curved inwardly to form a bead 14 into which are formed a series of spaced lugs 15. These lugs register with the thread 16 (shown in FIG. 2) formed on the neck of the container 17 and lock the closure in place.

The inner surface of the closure is usually coated with a protective film of a varnish or a lacquer and the gaskets are generally formed from h'quid compositions by a lining technique. In the lining operation (FIG. 1) the closure positioned over a rotating chuck (not shown) and the composition 18 flows through a nozzle 19 into the channel 13. The closure is spun by the chuck and the. composition is distributed as a narrow band in the channel. The lined closures are then passed to a heated oven maintained at a temperature sufiiciently high to flux the composition which, when cooled, solidifies to a permanent rubber-like gasket 20 (as shown in FIG. 2). The fiuxing step is generally carried out by continuously advancing the lined closures through an oven on a wire mesh belt,

and the advance is so synchronized that a residence time in the oven of about 60 seconds is sufiicient to flux the composition.

In applying a gasketed closure to a container, the gasket surface is initially dry to the touch, and as the closure is progressively advanced on the container, the increased pressure results in a corresponding increase in the exudation of additive to the surface. The greater the pressure the greater is the exudation, and migration of the additive continues until the closure is brought into sealing contact with the container. The surface layer of mixed amides, shown as an exaggerated film 21 in FIG. 2, remains on the gasket so long as the sealing relationship is maintained. Thus, it acts as a lubricant by reducing the frictional forces which exist between the gasket and the container and consequently, less torque is required to remove the closure. After the closure is removed the layer of mixed amides is gradually reabsorbed into the body of the gasket.

Vinyl resin plastisols are particularly suitable for use in forming the gaskets. These include plasticized homopolymers of vinyl chloride and copolymers of vinyl chlo ride with up to 20% by weight of another monomer copolymerizable therewith. Suitable monomers include acrylonitrile, vinylidene chloride, vinyl acetate, and dialkyl maleates. Typical copolymers include 95 percent vinyl chloridevinyl acetate; 95 percent vinyl chloride- 5% dialkyl maleate; and 94 percent vinyl chloride-6% vinylidene chloride. The preferred resin is plasticized polyvinyl chloride.

The plasticizers which may be used in the gasket-forming compositions include dialkyl phthalates, alkyl phthalyl alkyl glycolates, dialkyl esters of alkane dicarboxylic acids, acetyl trialkyl citrates, and trialkyl and triaryl phosphates. Particular plasticizers include dioctyl phthalate (di-Z-ethylhexyl phthalate), octyl decyl ph-thalate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, diisobutyl :adipate, dibutyl sebacate, acetyl dibutyl citrate, trioctyl phosphate and tricresyl phosphate. Other useful plasticizers include alkyl esters of fatty acids, such as octyl stearate; epoxidized triglycerides, such as epoxidized soybean oil; and polymeric polyester plasticizers, such as polymeric glycol adipate.

Various other additives may be included to modify the plastisol compositions. These include fillers, such as anhydrous calcium sulfate, talc, wood flour, diatomaceous earth and asbestos; stabilizers, such as tetrasodium pyrophosphate, tribasic lead silicate, calcium stearate, zinc stearate, dibasic lead stearate and organo-tin complexes; pigments, such as carbon black, titanium dioxide and aluminum powder; and dispersing agents such as zinc resinate, lecithin, glycol stearate, propylene glycol laurate and glycerol monooleate.

The proportions of the torque control additive are included in the gasket-forming composition in amounts sufiicient to insure a proper balance of lubricating properties in the gasket and will vary with the relative proportions and properties of the other components. In' general, the amount of additive should range between about 6 and 20, preferably between about 9 and 15, parts by weight per hundred parts of resin. As a rule, no additive will be observed on the surface of the fiuxed, uncompressed gasket, but it will appear when compression of the gasket exceeds 20 pounds per square inch. Unless an excessive amount of additive is used, the amount that will migrate with time is negligible, and the surface of the gasket will remain dry-and tack-free.

A representative gasket-forming composition whichiincluded the torque control additive of this invention was prepared for comparative purposes with al'c'ornposition which contained no additive, The formulations were: composed as follows: I

Example N o.

l The mixed amides consisted of 91% oleyl amide, 6% stearyl amide, and 3% linoleyl amide, by weight. 1

2 The mineral oil was a representative sample of a mixture of liquid hydrocarbons composed entirely of saturated aliphatic and naphthenic hydrocarbons, having a specific gravity of between 0.84 to 0.875 at 60 F and aviscosity of 25 to 55 cps. at 12 r.p.m. as measured on a Brookfield viscosimeter, Model LV4, No. 1 spindle.

Each composition was deposited in the annular channel at an 83 mm. rotatable lug-type metal closure and fluxed in an oven at a temperature of 400 F. and a residence time of one'minute. 1 l

Each closure containing the fluxed gasket was placed on a 12 oz. glass jar containing peanut butter heated at F. The turndown torque to seal each container was 50 inch-lbs. which is customarily employed in commercial closure-applying machines. The closed containers were stored for one day at room temperature and the closures were then tested for ease of removal. Test results of three closures of each of Examples 1 and 2 are shown in Table I.

TABLE I Example No.: Removal torques (inch-lbs.) 1 Q. 60, 65, 63 2 50, 50, 50

It is noted that the torque necessary to remove closures having gaskets which included the torque control additive of this invention was the same as the closing torque while the torque necessary to remove the closure from containers without the use of the additive in the gasket was about 25% higher than its closing torque. This is significant in that the frictional forces are reduced without adversely affecting the seal between the gasketed closure and container.

Examples 3 and 4 show the closing advantageof including the white mineral oil in gasket-forming compositions which were formulated as follows: I I

1 These ingredients are the same as describedaud used in the composit on otExample 2. I

TABLE II No. of failures Example 3 Example 4 Appllgcation Torque (inch-lbs.):

romeo OD-IW The high number of failures of gaskets formed from the composition of Example 3 indicates that the friction between the gasket and the mouth of the container was sufliciently high to prevent adequate rotation to elfect a reliable seal. On the other hand, the presence of the mineral oil in the gasket formed from the composition of Example 4 allowed the gasket to slide freely on the glass and thus permitted more rotation of the closure at each torque. As a result, no failures occurred when a torque of 25 inch-lbs. was applied. Since the normal application torque for 83 mm. closures varies between 25 to 50 inch-lbs, the gaskets prepared from the composition of Example 4 performed satisfactorily.

The examples show that the inclusion of the mixture of mineral oil and mixed amides in gasket-forming compositions enhances both closing and opening torques of rotatable closures. The accrual of these advantages does not detract from the sealing efliciency of the gasket.

I claim:

1. A closure comprising a cap adapted to be rotatwbly attached to a container opening and a rubber-like gasket positioned in the cap to register in sealing relationship withthe lip of the container, said gasket comprising a fluxed plastisol of a vinyl resin containing between about 6la rid" 20. parts by weight based on 100 parts by weight of the resin of a torque control additive consisting of (a) 25-75 percent by weight of white mineral oil,

and

(b) -25 percent by weight of a mixture of fatty acid amides composed of 91 percent oleyl amide, 6 percent stearyl amide and 3 percent linoleyl amide, said proportions being expressed on a weight basis.

2. A closure according to claim 1 wherein the resin is polyvinyl chloride and the additive is composed of 6 parts by weight of white mineral oil and 6 parts by Weight of mixed amides based on parts by weight of the resin.

3. A gasket-forming composition comprising a vinyl resin, a plasticizer therefor, and between about 6 and 20 parts by weight based on 100 parts by weight of the resin of a torque control additive consisting of (a) 25-75 percent by weight of white mineral oil,

and

(-b) 75-25 percent by Weight of a mixture of fatty acid amides composed of 91 percent oleyl amide, 6 percent stearyl amide and 3 percent linoleyl amide, said proportions being expressed on a weight basis.

4. A composition according to claim 3 wherein the resin is polyvinyl chloride and the additive is composed of 6 parts by weight of white mineral oil and 6 parts by weight of the mixed amides based on 100 parts by weight of the resin.

5. A torque control additive for gasket-forming compositions of which consists of (a) 25-75 percent by weight of white mineral oil,

and

(b) 75-25 percent by weight of a mixture of fatty acid amides composed of 91 percent oleyl amide, 6 percent stea ryl amide and 3 percent linoleyl amide, said proportions being expressed on a weight basis.

6. A composition according to claim 5 which consists of 50 percent by weight of white mineral oil and 50 percent by weight of the mixed amides.

References Cited UNITED STATES PATENTS 3,142,401 7/1964 Foss et al. 260-325 3,231,529 l/l966 Kuhn et al. 260-41 MORRIS LIEBMAN, Primary Examiner.

L. T. JACOBS, Assistant Examiner.

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