EP0618848A4

EP0618848A4 - Improved gasket for an aerosol mounting cup.

Info

Publication number: EP0618848A4
Application number: EP93902734A
Authority: EP
Inventors: Charles S Radtke; Timothy O'toole
Original assignee: Precision Valve Corp
Current assignee: Precision Valve Corp
Priority date: 1991-12-26
Filing date: 1992-12-23
Publication date: 1995-05-10
Also published as: WO1993012901A1; CA2130352A1; EP0618848A1; TW245666B; GB9225688D0; GB2262742A; MX9207246A; ZA929464B; PT101150A; AU3420193A; CN1078423A

Abstract

A gasket material (24) for sealing a channel (20) of a mounting cup (10) to a container bead (12) is disclosed having a flexural modulus, 1 % secant, of at least about 70,000 psi, as measured by ASTM Method D 790, and a hardness no greater than about 60 Shore D, as measured by ASTM D 2240. Also disclosed is a gasket material (24) comprising a mixture of a stiffer plastic material and a softer plastic material wherein the mixture meets the above flexural modulus and hardness criteria. A preferred material and mixture are disclosed. Preferred dimensions for the gasket on the mounting cup are also disclosed.

Description

IMPROVED GASKET FOR AN AEROSOL MOUNTING CUP

Background

Aerosol dispensing containers have found widespread use in the packaging of fluid materials including a variety of both liquid and powdered particulate products. Such containers are provided with a valve-controlled discharge orifice and operate by the action of a volatile propellant which is confined within the container together with the product to be dispensed. Because the propellant has an appreciable vapor pressure at room temperature, the product in the closed container is maintained under superatmospheric pressure.

A typical aerosol unit comprises a hollow cylindrical container which is tightly closed at one end and is provided with an opening at its opposite end for receiving a dispensing valve assembly. A closure, commonly referred to as a mounting cup, serves as the closure for the container and as a support for the valve assembly. Typically, the mounting cup comprises a pedestal portion for mounting the valve unit, a panel portion extending from the pedestal portion, a skirt portion depending from the periphery of the panel, and an annular channel portion extending outwardly from the skirt. When the mounting cup is placed in sealing position on the container, the channel is positioned over the bead surrounding the container opening and the lower portion of the skirt adjacent to the channel is flared or clinched outwardly against the underside of the bead. To ensure adequate sealing between the closure and the container, the cup is provided with a gasket in the channel, or predominantly in the channel, of the cup.

In United States Patent Nos. 4,546,525 ("the '525 patent") and 4,547,948 ("the '948 patent"), a novel gasketed mounting cup system, including novel method and apparatus, is described wherein the gasket material is disposed on the mounting cup in the preferred position for effecting a seal between the mounting cup and the bead of the container, in an exceptionally rapid and efficient manner to form gasketed-mounting cups having excellent sealing characteristics. In general, the method of invention of the '525 and '948 patents comprises passing a tubular sleeve of gasket material onto a compressible mandrel; initially positioning and aligning the skirt of the mounting cup and the contiguous end of the mandrel such that the sleeve of gasket material may pass onto the skirt, said mandrel having fixed and moveable portions with respect to each^' other and to their movement toward and away from the mounting cup; urging the moveable portion of the gasket material bearing mandrel toward the mounting cup such that the gasket material passes onto the skirt of the cup; causing the moveable portion of the mandrel to retract to its initial position, cutting the sleeve at a point between the mounting cup and the mandrel to leave a band of gasket material; and subsequently, advancing the mounting cup to a station whereat the band of the gasket material is urged further onto the skirt of the mounting cup, whereby, the band of gasket material does not extend beyond the skirt of the mounting cup. Subsequently, the gasket is advanced to the desired position partially within the channel of the mounting cup. The '525 and ^,948 patents are incorporated by reference herein.

The dip tube of the container is usually slightly longer than the height of the container to insure that its end is positioned at the bottom of the container. As shown in Figure 1, when the mounting cup is positioned on the container bead, the dip tube is slightly bent. This can provide an upward force which can displace the mounting cup from the container bead, interfering with proper clinching. To ensure that the mounting cup is maintained on the container bead prior to clinching, protrusions are created around the skirt of the mounting cup which are below the container bead when the mounting cup is in position. Such protrusions 14a are also shown in Figure 1. The force provided by the bent dip tube is generally insufficient to overcome the retaining force provided by the protrusions. The protrusions are formed by a tool placed around, the pedestal of the mounting cup, which forces out particular sections of the skirt of the cup. In the United States, aerosol containers are typically filled by the undercap filling method. First, the product to be dispensed is deposited into the container. Then a mounting cup, including the valve and dip tube, is placed on the container such that the bead of the container is within the channel of the mounting cup. The filling head of an undercap filling machine then encompasses the top of the container, creating an airtight seal. Air is then evacuated from the container. The suction created during evacuation raises the mounting cup off of the container bead. Propellant is then forced into the container opening beneath the mounting cup and the mounting cup is repositioned and clinched to the container bead. During the filling process, suction during evacuation or the force of the propellant during filling can displace the gasket from its position within the channel of the mounting cup, preventing a proper seal on clinching. In some cases, the gasket can be completely displaced by the propellant filling the container, forcing the gasket into the container. This is referred to as a "blown" gasket.

Gasket displacements are more likely with the low density polyethylene ("LDPE") commonly used to form such gaskets. Replacement of LDPE with high density polyethylene ("HDPE") yields a less effective seal because the HDPE is not sufficiently resilient to adequately conform to the metal of the mounting cup.

In addition, various methods of forming gaskets are utilized in the art, yielding varying gasket thickness. This variation in gasket thickness among the several gasket systems, further complicated by the fact that the channel portion of the mounting cups manufactured by the valve assembly plants and the annular beads of the aerosol container manufactured by container plants have nominal variations which are within quality control limits, often produce a defective seal in a completed aerosol product which may remain undetected until ultimately discovered by the consumer.

Therefore, a variety of methods have been tried to maintain the gasket in its proper position for sealing. For example, in U.S. Patent No. 4,559,198, assigned to the assignee of the present invention, annular or radial compressive deformations form ribs which improve the gasket's resistance to being dislodged during undercap filling or otherwise being repositioned on the mounting cup by the gasket returning to its initial position. In U.K. Patent No. GB 2,206,650, also assigned to the assignee of the patent invention, a thermal adhesive is disclosed which adheres the gasket to its final position partially within the channel of the mounting cup.

In U.S.S.N. 07/552,299, filed on July 18, 1990 and also assigned to the assignee of the present invention, a multi¬ layer gasket comprising a middle layer of a stiffer plastic material and inner and outer layers of softer plastic material adjacent both sides of the middle layer is disclosed. The middle layer is preferably HDPE while the inner and outer layers are preferably LLDPE. Such a gasket, while producing superior results, requires additional manufacturing steps, adding to the cost and time involved in making and positioning the gasket.

The seal between the mounting cup and the aerosol container remains of great concern to both the valve assembly plants and the filling plants since it must be capable of being air tight for a period of years. In addition, the seal between the mounting cup and the aerosol container must be low in cost to enable aerosol products to be competitive with non-aerosol products in the consumer market.

Summary of the Invention In one aspect of the present invention, a plastic polymer is disclosed having a flexural modulus, 1% secant, of at least about 70,000 psi as measured by ASTM method D 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240. A flexural modulus of at least about 90,000 psi and a hardness between about 53-56 is preferred. It is also preferred that the gasket be a sleeve type gasket and the polymer be a thermoplastic.

In another aspect of the invention, a gasket for sealing a channel of a mounting cup to a bead of a container comprises a mixture of a stiffer plastic material and a softer plastic material which mixture meets the flexural modulus and hardness limits described above. As above, the gasket is preferably a sleeve type gasket and the plastic materials are thermoplastics. In a preferred embodiment of the invention, the gasket material comprises a mixture of high density polyethylene ("HDPE") and linear low density polyethylene ("LLDPE") . The * preferred HDPE is about 43% by weight of the gasket and the 5 preferred LLDPE is about 57% by weight of the gasket. In certain applications, it is also preferred to include a layer of thermal adhesive on the surface of the gasket material to be in contact with the mounting cup. In a further aspect of the invention there is a 10 gasketed mounting cup comprising a panel, a skirt integral with and depending from the periphery of the panel, the skirt being outwardly flared to form an annular channel for receiving a container bead that defines a container opening; and a gasket disposed partially within the channel of the 15 mounting cup and partially along the skirt of the mounting cup, wherein the gasket material is as described above. In certain applications, it may be preferred to bond the gasket to the mounting cup by a layer of thermal adhesive. In preferred embodiments of the invention, the gasket's 20 position on the mounting cup meet certain critical requirements.

In a further aspect of the invention, optimum values and ranges for critical dimensions of the position of the _, gasket on the mounting cup are disclosed. 25 Description of the Figures Figure 1 is a cross-sectional view of a gasketed mounting cup in accordance with the present invention;

Figure la is a cross-sectional view of the channel of the gasketed mounting cup of Figure 1, clinched to a container bead;

Figure 2 is a cross-sectional view of a portion of a gasket prior to its being advanced into the channel of a mounting cup; and Figure 3 is a cross-sectional view of a portion of the punch preferred for use in manufacturing the gasketed mounting cup of the present invention.

Description of the Invention Figure l shows a gasketed aerosol valve mounting cup of the present invention generally designated as 10 resting on a container bead 12 of an aerosol container (not shown) . Figure la shows the channel portion 20 of the gasketed mounting cup 10 clinched to the container bead 12. The mounting cup has a pedestal portion 14 which depends from the interior edge of a panel portion 16. A skirt 18 depends from the exterior edge of the panel portion 16 opposite the pedestal portion 14 and is concentric thereto. The top portion of the skirt 18 curves into an annular channel portion 20 which terminates in an edge portion 22.

The channel portion 20, edge portion 22 and skirt 18 form an annular concave receptor for receiving the bead 12 of the aerosol container, as shown. The gasket 24 of the invention is positioned partially within the channel 20 of the mounting cup 10. The gasket 24 has a first portion 24a in contact with part of the channel portion 15 of the mounting cup 10. The gasket 24 also has a second portion 24b in contact with the skirt 14 of the mounting cup 10. Also shown are dimples 26 which retain the gasket 24 and mounting cup 10 on the container bead prior to undercap filling. Such dimples are described in more detail in U.S.S.N. 07/814,370, filed on the same day as the present application and assigned to the same assignee. U.S. Serial No. 07/814,370 is incorporated by reference herein.

The mounting cup 10 is preferably a standard mounting cup for use in a standard one inch opening of an aerosol container. The radius "r" of the bead 12 of the container is 0.06 inches. Optimum ranges for certain critical dimensions for the gasket's 24 position on the mounting cup 10 have been ascertained and are one aspect of the invention. In such a standard cup, the length "L-l" of the gasket as measured from the center of the channel 20 of the mounting cup to the end of the second portion 24b. is preferably at least 0.150 inches and is most preferably about 0.175 inches. L-l is shown in Figure 1. It has been found that for optimum sealing, it is necessary to have sealing material in the region between the skirt 18 and the container bead 12 proximate numeral "18" in Figure la. These preferred lengths ensure that the second portion 24b of the gasket material 24 is properly positioned along the skirt 18 of the mounting cup 11 to provide sealing material in this critical region. If the radius r of the container bead 19 is larger then 0.06 inches, a larger length L-l would be required. If the radius r is smaller than 0.06 inches, a shorter length L-l would be acceptable.

The gasket material 24 should be positioned far enough into the channel 20 of the mounting cup such that the diameter "d" of the gasket flare, as measured at the end of the first portion 24a of the gasket 24 through the center of the mounting cup 10, as shown in Figure 1, is preferably greater than about 1.100 inches. It is more preferably greater than about 1.180 inches. It is most preferably about 1.200 inches. Such a flare diameter places the end of the first portion 24a of the gasket 20 at approximately the 10 o'clock position within the annular convex receptor. Such placement of the gasket shows improved resistance to dislodgement from the channel 20 of the mounting cup 10.

To achieve the preferred flare diameter, the length "L- 2" of the gasket material after being cut from the sleeve

(as described in the '525 and '948 patents), referred to as its "cut length, should be between about 0.250-0.285 inches. See Figure 2.

The gasket 20 is preferably between about 0.013-0.016 inches thick. It is most preferably 0.014 inches thick.

While it is preferred to utilize these dimensions with the preferred gasket material described below, these dimensions can improve the performance of any gasket material on a standard mounting cup. In addition, the optimum dimensions and positioning of the gasket can improve sealing in non-sleeve type gaskets, applied by processes other than the preferred process described herein.

The gasket material 24 of the invention is a plastic polymer having a flexural modulus, 1% secant, of at least about 70,.000 psi as measured by ASTM method D 790, and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240. Such a material has a stiffness sufficient to maintain the gasket in position partially within the channel 20 of a mounting cup and is sufficiently soft to provide an adequate seal between the channel 20 of the mounting cup 10 and a container bead 12 when clinched. Preferably, the flexural modulus is at least about 90,000 psi and the hardness is 56 or less, as measured above.

If the gasket material is in the preferred form of a sleeve gasket, then the plastic is preferably a thermoplastic polymer. Sleeve gaskets are preferably positioned in accordance with the process described in the '525 and '948 patents, and U.S. Serial No. 07/814,370. Thermoplastics are preferred for use with sleeve gaskets because they soften when heated, easing placement within the channel of the mounting cup, and harden on cooling, retaining their shape conforming to the channel of the cup. Suitable thermoplastic materials include polyethylenes, polypropylenes, other polyolefinic compounds such as -12-

ethylvinylacetate ("EVA") copolymers, ethyl vinyl alcohol copolymers, polypropylene and ethylene copolymers, and polyethylene modified by elastomers such as rubber. In addition, polyurethanes, polyesters, ionomers, polycarbonates and some polyamides such as nylon 11, can be used. The particular plastic chosen needs to be chemically resistant to the product and propellant in the aerosol container and could, therefore, vary depending on the application. The plastic also needs to have sufficient resistance to environmental stress to withstand the pressure and compression forces endured by aerosol gaskets. Environmental stress crack resistance as measured by D 1693 of at least about 400 hours is preferred. The plastic needs to be resistant to cold flow as well.

It is believed that DEHD 1796 ("DEHD") , a polyethylene available from Union Carbide, will provide satisfactory performance. DEHD is a commodity material used by Union Carbide to form other plastics, such as DHDA 2463, also available from Union Carbide. Typical property data for DEHD follows:

DEHD

Property

Tensile Strength (break) , psi (MPa)

Ultimate Elongation, %

Flexural Modulus, psi (MPa) -13-

DEHD (Cont'd.)

The gasket can also comprise a mixture of a first plastic material providing sufficient stiffness to maintain the gasket in position partially within the channel 20 of the mounting cup 10 and a softer plastic material providing sufficient softness to provide a reliable seal between the channel 20 of the mounting cup 10 and the container bead 12 when clinched such that the mixture has a flexural modulus, 1% secant, of at least about 70,000 psi, as measured by ASTM method D 790, and preferably at least about 90,000 psi. The mixture has a hardness no greater than about 60 Shore D, as measured by ASTM method D 2240, and is preferably 56 or less. Generally, the stiffer material will have higher density than the softer material. As above, if the gasket is the preferred sleeve gasket, the polymers forming the mixture are preferably thermoplastics. The mixture should have sufficient resistance to environmental stress to withstand the pressure and compression forces endured by aerosol container gaskets. As above, environmental stress crack resistance of at least about 400 is preferred. The plastic must be resistant to cold flow, as well.

Suitable stiffer materials include HDPE, other stiff polyethylenes such as LLDPE of suitable molecular weight, polyamides, polycarbonates, polypropylenes, polyesters, acrylonitrilebutadienstyrenes ("ABS") , or acetyls. The flexural modulus of the stiffer materials is greater than

70,000 psi as measured as described above, and is preferably greater than 90,000 psi. Suitable softer materials include some polyethylenes and other polyolefins, ethylene-ethyl acrylate copolymer, polyesters, polyurethanes and most other thermoplastic elastomers. The hardness of the softer materials is less than 60 as measured as described above, and is preferably below 56. -15-

The plastics chosen must be compatible in order to form a homogenous mixture. The materials chosen also need to be chemically resistant to the product and propellant and could therefore vary depending on the application. Suitable mixtures include HDPE and LLDPE or LDPE, or polyethylene and polypropylene.

The relative quantity of the softer and stiffer plastic materials combined to form the mixture having the characteristics described above depends on their softness and stiffness. For example, if the soft material and stiff material are each close to the desired hardness and flexural modulus values, mixtures of between about 60% of one to 40% of the other may be utilized to yield mixtures having the characteristics of hardness and flexural modulus described above. If either or both of the hardness and flexural modulus values of either material are far from the desired values, larger quantities of one material may be required to yield the desired values in the mixture. For example, mixtures of between about 60%-70% of one to about 40%-30% of the other, about 70%-80% of one to about 30%-20% of the other or even greater than 80% of one and less than 20% of the other, may be utilized.

The preferred stiffer material is HDPE having a flexural modulus of at least about 140,000 psi. A higher flexural modulus is even more preferred. The preferred HDPE is

Altaven™ 6200B HDPE, available from Plastics Del Logo, C . Venezuela. Preferably, the LLDPE has a hardness no greater -16-

than about 55 and more preferably no greater than about 50, The preferred LLDPE is DNDA-7340 Natural 7 ("DNDA-7340") , available from Union Carbide.

Typical property data for the preferred HDPE and LLDPE appear below:

Altaven™ 620OB

-17-

DNDA-7340 (cont' d)

Property Test Method Typical Values

Ultimate Elongation D 638 500 %

Bent Strip

Crack Resistance, hrs^(x), F 100% "Igepal" D 1693 >500 10% "Igepal" >500

Brittleness Temperature D 746Below - 100°C

Flex. Life, Cycles to Fail UCC Method 140,000

Minimum Shear Rate To Melt Fracture, sec^"1 UCC Method 4,000

Hardness D 2240 ~45

With the preferred HDPE and LLDPE described above, mixtures within the range of about 62%-52% LLDPE to about

38%-48% HDPE are preferred. A mixture of 57% by weight of the DNDA-7340, 43% by weight of the Altaven™ 6200B, is currently being used.

Alternatively, a soft material, such as LLDPE, can be stiffened, increasing its flexural modulus by the addition of inorganic filler or fiber. Fiberglass fiber, glass beads, talc, or calcium carbonate are suitable additives.

Coupling agents may be required to bond the inorganic filters to the organic base material, as is known in the art.

In certain applications, such as where propellant is inserted into the container at high pressure after the product has been inserted, an adhesive is preferably used to further secure the gasket of the invention to the mounting cup. If the gasket is of the sleeve type, applied in accordance with the process of the '525 and '948 patents, it is further preferred to use a thermal adhesive. The thermal adhesive prevents the gasket from prematurely bonding to the mounting cup, preventing its advancement into its final position partially within the channel 20 of the mounting cup

10. Heating of the mounting cup prior to the final advancement of the gasket in the gasket placement process melts the thermal adhesive, activating the adhesive. After the gasket is advanced and the mounting cup is removed from the heat source, the temperature of the mounting cup drops to room temperature and the thermal adhesive bonds the gasket to the mounting cup. Preferably, the adhesive is a mixture of about 64.67%

Exxon Escdr acid terpolymer ATX 325 ("ATX 325") , about

35.67% DNDA-7340 and 0.66% H. Kohnstamm PB 3962 blue dry colorant. The blue colorant is added to enable the visible inspection of the sleeve gasket to determine if the adhesive is evenly distributed. It also eases identification of the gasket on the mounting cup. The thermal adhesive layer is preferably about 0.00075 inches thick. Typical property data for ATX 325 appear below:

ATX 325 PROPERTIES ASTM METHOD VALUES

Melt Index D 1238(E) 20 g/10 min -19-

ATX 325 (cont'd.)

PROPERTIES ASTM METHOD VALUES

Acid Number Exxon Method 45

Milligrams KOH/gm polymer

Density D 792 0.942 g/cc

Tensile Strength psi (MPa)

Elongation %

Flexural Modulus psi (MPa)

Tensile Impact, ft-lbs/in² (KJ/m²) §

73 ° F (23 ^β C) (735)

-43 ° F (-40 "C) (535)

Hardness, Shore D

DSC Melting Point °F (°C)

Viscat Softening Point °F (°C), 200 g load (Rate B)

To form the preferred gasket of the invention, about 57% by weight of DNDA-7340 LLDPE and about 43% by weight of Altaven™ HDPE 6200B were added to a ID Banbury Mixer with a capacity of 30 pounds and mixed for about 2.5 minutes. Such a mixer is available from Farrel Machinery, for example. The mixing started at room temperature and reached 380- 400^βF by the end of the mixing period. The mixture was then conveyed to a Farrel 41 inch extruder, preheated to about 400-420°F. The mixture was discharged from the extruder at a rate of about 600 pounds per hour to a cooling trough and a Cumberland Strand Pelletizer, available from Cumberland, Inc. The pelletized mixture was later converted into a sleeve gasket by extrusion, as is known in the art. The sleeve gasket should be visually inspected to ensure that the gasket thickness is uniform. Thinned areas of the sleeve can interfere with the integrity of the seal, causing displacement of the gasket prior to clinching, or leaks. To form the preferred thermal adhesive, about 64.67% by weight of ATX 325, about 35.67% by weight of DNDA-7340 LLDPE and 0.55% by weight of H. Kohnsta m PB 3962 blue colorant were added to the Banbury mixer and mixed for 2 minutes, up to 300-320°F. The mixture was then conveyed to an extruder and extruded at a rate of about 600 pounds per hour at between 300-320"F. It was then pelletized as above. The thermal adhesive and sleeve gasket were coextruded into a tool where the layers were merged, as is known in the art. The gasket material was approximately 0.014 inches thick while the layer of thermal adhesive, which is located on the inside surface of the sleeve gasket material, was approximately 0.00075 inches thick. The.sleeve gasket should be visually inspected to ensure that the thermal adhesive has been applied evenly. The gasket of the invention is preferably positioned on the mounting cup as generally described in the '525 and '948 patents. A single station gasket mounting cup assembly machine is utilized instead of the six station assembly machine shown in Figure 3 of the '948 patent. It has been found that the sleeve gasket material may be positioned on a single mounting cup faster and more accurately than if sleeve gasket material is concurrently positioned on six mounting cups. In addition, higher temperatures are currently used than those disclosed in these patents.

A mounting cup temperature of at least about 150°F and preferably about 170"F, as measured on the raceway about 1 foot from the punch station, less than one second after the final positioning of the gasket within the channel of the mounting cup, is utilized. This is a convenient point to measure the temperature. It is believed that the temperature of the mounting cup is 20°- 30°F higher while the gasket is being advanced to its final position on the mounting cup. At 170°F, the gasket's increased pliability further eases its advancement into the channel of the cup, as does the wetting provided by melting the thermal adhesive. At higher temperatures, the gasket could degrade and become too soft. However, mixtures including higher percentages of HDPE can tolerate higher temperatures. A one piece punch 30 is preferred for advancing the gasket 24 into the channel 20 of the mounting cup. The punch preferably includes an extension 30a for engaging the end of the first portion 24a of the gasket 24 as it is being advanced into the channel 20 of the mounting cup 10 as shown in Figure 3. The extension 30a ensures that the gasket is advanced to its preferred position within the channel 20 of the cup, yielding the preferred gasket flare d, as shown in Figure 1. A shoulder 34 is provided to engage the top of the second portion 24b of the gasket 24 and to advance the gasket to its final position. The punch further includes a series of lugs 32 formed by pins 32a pressfit into the punch 30. These lugs form the dimples 26 shown in Figure 1 and described further in U.S. Serial No. 07/814,370. Further details concerning the process and preferred punch utilized in manufacturing the gasketed mounting cup of the present invention are described in U.S.S.N. 07/814,370.

Comparative tests of the gasket in accordance with the preferred embodiments of the present invention with conventional gaskets of LLDPE have shown that the gasket of the present invention is more resistant to blown gasket failure and has more consistent performance. The forces applied to a gasket in the channel of the mounting cup during undercap filling were simulated by a bench device comprising a fixture shaped like a container bead positioned within an airtight chamber. The mounting cup was placed on the fixture and a cap seal, pressure loaded by an air cylinder, was pressed down on the mounting cup with an adjustable force. Air was pumped into the chamber at a desired pressure. When the pressure within the chamber overcame the force exerted by the air cylinder and cap seal on the mounting cup, the mounting cup rose. Air then passed between the channel of the mounting cup and the fixture, past the gasket, just as propellant is forced through the channel into a container during undercap filling.

12 gaskets are considered a representative test sample. The maximum pressure where none of the 12 test gaskets 5 failed ("PI") and the minimum pressure that caused all 12 to fail ("P2") were determined. A failure is a blown gasket. A higher PI indicates better resistance to blown gasket failure while a small difference between PI and P2 indicates consistent product performance. The pressure of the cap

10 seal was varied such that if all 12 gaskets did not pass the test, the pressure was lowered. If all 12 passed, the pressure was raised until PI was determined. Then the pressure was increased until all 12 gaskets failed. PI and P2 can be converted into load forces by multiplying the

15 pressure values in the air cylinder providing the force against the cap seal, by 12.5, which is the approximate area of the cylinder in inches.

For gaskets of LLDPE, adhered to the mounting cup by the thermal adhesive described above, at a filling pressure of

20 600 psi, PI = 14 psi (175 lbs) and P2 = 28 psi (350 lbs) .

At a filling pressure of 800 psi, PI = 10 psi (125 lbs) and P2 = 24 psi (300 lbs) .

For gaskets of Altaven™ 6200B and DNDA-7340 of 43% and 57%, respectively, bonded to the mounting cup by the thermal

25 adhesive described above, at a filling pressure of 600 psi, fl both PI and P2 = 28 psi (350 lbs) . At a filling pressure of 800 psi, PI = 26 psi (325 lbs) and P2 = 28 psi (350 lbs) . These results demonstrate that the gasket material of the present invention is far superior to conventional gaskets of LLDPE in resistance to blown gasket failure and in consistency of performance. Comparative tests varying the cut length of the gasket, which effects the flare diameter of the gasket within the channel of the mounting cup, showed improved results as the cut length was increased. For gaskets of a height of 0.225 inches, comprised entirely of LLDPE and adhered to the mounting cup by the thermal adhesive described above, at a filling pressure of 600 psi, PI = 10 psi (125 lbs) and P2 = 28 psi (350 lbs) . At a filling pressure of 800 psi, PI = 8 psi (100 lbs) and P2 = 26 psi (325 lbs) .

At a height of 0.250 inches, all other variables being the same as above, at a filling pressure of 600 psi, PI = 14 psi (175 lbs) and P2 = 28 psi (350 lbs) . At a filling pressure of 800 psi, PI = 10 psi (125 lbs) and P2 = 24 psi (300 lbs) .

At a height of 0.275 inches, all other variables being the same as above, at a filling pressure of 600 psi, PI = 14 psi (175 lbs) and P2 = 28 psi (350 lbs) . At a filling pressure of 800 psi, PI = 12 psi (150 lbs) and P2 = 18 psi (225 lbs) .

Comparative tests varying the design of the punch showed improved results with a one piece punch including an extension 30a for engaging the gasket as shown in Figure 3, over a two piece punch. For a LLDPE gasket with a cut length of 0.270 inches bonded to the mounting cup by the thermal adhesive described above, and a cup temperature of 154°F, applied with a two piece punch, at filling pressure of 600 psi, PI = 14 psi (175 lbs) and P2 = 28 psi (350 lbs). At a filling pressure of 800 psi, PI = 12 psi (150 lbs) and P2 = 18 psi (225 lbs) .

With the one piece punch of Figure 3, all other variables being equal, at a filling pressure 600 psi, PI = 16 psi (200 lbs) and P2 = 26 psi (325 lbs) . At a filling pressure of 800 psi, PI = 14 lbs) psi (175 lbs) and P2 = 24 psi (300 lbs) .

The preferred characteristics of material, thermal adhesive, cut length and punch design each demonstrated improved resistance to dislodgement and consistency of performance. Taken together, the preferred characteristics yield a superior gasketed mounting cup.

Claims

We claim:

1. A plastic polymer for use as a gasket material for sealing a channel of a mounting cup to a bead of a container having a flexural modulus, 1% secant, of at least about

70,000 psi as measured by ASTM method D 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240.

2. The plastic polymer of claim 1 having a flexural modulus greater than about 90,000 psi.

3. The plastic polymer of claims 1 or 2 having a hardness of about 56 or less.

4. The plastic polymer of claim 1 wherein the polymer is a thermoplastic. 5. The gasket material of claims 1 or 4 wherein the gasket has a cut length of about 0.250-0.285 inches.

6. The gasket material of claim 1 further comprising a layer of thermal adhesive.

7. A thermoplastic polymer for use as a sleeve gasket material for sealing a channel of a mounting cup to a bead of a container having a flexural modulus, 1% secant, of at least about 70,000 psi as measured by ASTM method D 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240. 8. The thermoplastic polymer of claim 7 having a flexural modulus greater than about 90,000 psi. 9. The thermoplastic polymer of claims 7 or 8 having a hardness of about 56 or less.

10. The gasket material of claim 7 chosen from the group consisting of polyethylenes, polypropylenes,

5 polyolefinic compounds, ethylvinylacetate (EVA) copolymers, ethyl vinyl alcohol copolymers, polypropylene and ethylene copolymers, polyethylene modified by elastomers, polyamides, nylon 11,. polyurethanes, polyesters, ionomers and polycarbonates.

10 11. A gasket material for sealing a channel of a mounting cup to a bead of a container comprising a mixture of a first plastic material and a second plastic material mixed in proportion such that the mixture has a flexural modulus, 1% secant, of at least about 70,000 psi as measured

15 by ASTM method D 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240.

12. The gasket material of claim 11 wherein the first material is chosen from the group consisting of HDPE, stiff polyethylenes, polycarbonates, polypropylenes, polyesters,

20 acrylonitrilebutadienstyrenes ("ABS") , and acetyls, and the second plastic material is chosen from the group consisting of soft polyethylenes, soft polyolefins, ethylene-ethyl acrylate copolymer, polyesters, polyurethanes and thermoplastic elastomers.

25 13. A gasket material for sealing a channel of a a mounting cup to a bead of a container comprising a mixture of high density polyethylene and linear low density polyethylene, the gasket material having a flexural modulus, 1% secant, of at least about 70,000 psi as measured by ASTM method D 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240. 14. The gasket material of claims 11 or 13 having a flexural modulus is greater than 90,000 psi.

15. The gasket material of claims 11 or 13 having a hardness .of about 56 or less.

16. The gasket material of claim 13 wherein the high density polyethylene is in a range of about 38%-48% by weight and the linear low density polyethylene material is in a range of about 52%-62% by weight.

17. The gasket material of claim 13 wherein the high density polyethylene is about 43% by weight of the gasket and the linear low density polyethylene is about 57% by weight of the gasket.

18. The gasket material of claim 17 or 18 wherein the LLDPE is DNDA.

19. The gasket material of claim 17 wherein the HDPE is Altaven" 6200B.

20. The gasket material of claim 15 further comprising a layer of thermal adhesive.

21. The gasket material of claim 15, wherein the gasket has a cut length of 0.250-0.285 inches. 22. A gasketed mounting cup comprising a panel, a skirt integral with and depending from the periphery of the panel, the skirt being outwardly flared to form an annular channel for receiving a container bead that defines a container opening; and a gasket material disposed partially within the channel of the mounting cup and partially along the skirt of the mounting cup, the gasket comprising a plastic polymer 5 having a flexural modulus, 1% secant, of at least about

23. The gasketed mounting cup of claim 22 wherein the 10 gasket has a flexural modulus of at least about 90,000 psi.

24. The gasketed mounting cup of claims 22 or 23 wherein the gasket material has a hardness of about 56 or less.

25. A gasketed mounting cup comprising a panel, a skirt 15 integral with and depending from the periphery of the panel, the skirt being outwardly flared to form an annular channel for receiving a container bead that defines a container opening; and a gasket material disposed partially within the channel of the mounting cup and partially along the skirt of

20 the mounting cup, the gasket comprising a mixture of a first thermoplastic material and a second thermoplastic material, the first material having a higher flexural modulus than the second, and the second material being less hard than the ϊ» first, the first and second materials being mixed in

25 proportion such that the mixture has a flexural modulus, 1% secant, of at least about 70,000 psi as measured by ASTM method D 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240.

26. The gasketed mounting cup of claim 25 wherein the first material is high density polyethylene and the second material is linear low density polyethylene.

27. The gasketed mounting cup of claim 26 wherein the first material is in a range of about 38%-48% by weight and the second material is in a range of about 62%-52% by weight. 28. The gasketed mounting cup of claim 26 wherein the high density polyethylene is about 43% by weight of the gasket and the linear low density polyethylene is about 57% by weight of the gasket.

29. The gasketed mounting cup of claim 25 further comprising a layer of thermal adhesive between the gasket and the mounting cup.

30. The gasketed mounting cup of claim 25 wherein the gasket has a cut length of about 0.250-0.285 inches.

31. The gasketed mounting cup of claims 25 wherein the gasket is adhered to the mounting cup by a thermal adhesive.

32. A gasket material for sealing a channel of a mounting cup to a bead of a container comprising a mixture of a first plastic material having sufficient stiffness to maintain the gasket in position partially within the channel of the mounting cup and a second plastic material having sufficient softness to provide the seal. 33. A gasket for sealing a channel of a mounting cup to a bead of a container comprising a mixture of a stiffer thermoplastic material and a softer thermoplastic material.

34. A gasket for sealing a channel of a standard

5 mounting cup to bead of a standard container, the gasket having a cut length of between about 0.250-0285 inches.

35. A standard gasketed mounting cup comprising a panel, a-skirt integral with and depending from the periphery of the panel, the skirt being outwardly flared to

10 form an annular channel for receiving a container bead that defines a container opening, the annular channel having a center and a gasket material having a first portion partially disposed within the channel of the mounting cup and a second portion partially disposed along the skirt of

15 the mounting cup, the first and second portions each having an end, the gasket having a length as measured from the center of the annular channel of the mounting cup to an end of the gasket along the skirt of the mounting cup, of at least about 0.150 inches.

20 36. The gasketed mounting cup of claim 36 wherein the length of the gasket is about 0.175 inches.

37. The gasketed mounting cup of claims 35 or 36 wherein the diameter of the gasket as measured at the end of the first portion of the gasket through a center of the

25 mounting cup is at least about 1.100 inches. »

38. The gasketed mounting cup claims 35 or 36 wherein a diameter of the gasket as measured at the end of the first portion of the gasket through a center of the^' mounting cup is at least about 1.180 inches.

39. The gasketed mounting cup of claims 35 or 36 wherein the diameter of the gasket as measured at the end of the first portion of the gasket through a center of the mounting cup is about 1.200 inches.

40. The gasketed mounting cup of claims 35 or 36 wherein he end of the first portion of the gasket is at about the 10 o'clock position within the annular channel of the mounting cup.

41. A gasketed mounting cup comprising a panel, a skirt integral with and depending from the periphery of the panel, the skirt being outwardly flared to form an annular channel for receiving a container bead that defines a container opening, the annular channel having a center and a gasket material having a first portion partially disposed within the channel of the mounting cup and a second portion partially disposed along the skirt of the mounting cup, the first and second portions each having an end, the gasket having a length as measured from the center of the annular channel of the mounting cup to an end of the gasket along the skirt of the mounting cup of at least about 0.150 inches and a diameter of the gasket as measured at the end of the first portion through a center of the mounting cup is about 1.200 inches.