GB2262742A - Polymeric gasket material for aerosol mounting cups - Google Patents

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

POLYMERIC GASKET MATERIAL FOR AEROSOL MOUNTING CUPS This invention relates to polymeric gasket materials for aerosol mounting cups, aerosol mounting cup gaskets made therefrom, and aerosol mounting cups and containers utilising such gaskets.

Aerosol dispensing containers have found widespread use in the packaging of fluid materials including a variety of both liquid and powdered particular 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 vapour pressure at room temperature the product in the closed container- is maintained under superatmospheric pressure.

A typical aerosol unit comprises a hollow cylindrical contained 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 closur-e 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 fron 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 port ion 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 xhannel, of the cup.

In United States Patent Nos. 4,546,525 ("the '525 patent") and 4, 547,948 ( " the 948 patent") a rinve gasketed mount 1 rig clip system, including novel method and apparatus, is described wherein t-he gasket material is disposed on the mounting ciip in the preferred position for' effecting a seal between the mounting cup and the bead of the container, in air exceptionally rapid and efficient manner to form gasketed-mounting cups having excellent seal j ng 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 '949 patents are incorporated b 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 ciip is maintained on the container bead prior- to clinching, prot r-us ions are created around the skirt oi 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 lient dip tube is generally insufficient to overcorne the retaining force provided by the protrusions.The protrusions an formed by a tool p]aced around the pedestal of the mounting cup, wh j cli forces out par-ticular- sections of the skirt of title cup.

In the United States, aerosol containers are r.ypical fillpl 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 under-cap filling machine then encompasses the top of tire container, creating an airtight seal. Air is then evacuated from the container. The suction created during evacuation raises tire 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 disp]acements are more likely with the low density polyethylene ("LDPE") commonly used to form such gaskets. Replacement of LDPE with iligh density polyethylene ("HDPE") yields a less effective seal because the HDPE is riot sufficiently resilient Lo adequately conform to the metal mounting cup.

In addition, various methods of forming gaskets are utilised in the art, yielding varying gasket thickness. This variant ion in gasket thickness among the several gasket systems, further compi icated by the fact that the channel portion of the mounting cups manufactured by tire valve assembly plans and tire annular beads of the aerosol container manufactured by contairrer 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 propel position for sealing. For example, in U.S. Patent No. 4,559,198, assigncd 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 adher-es the gasket to its final position partially within tire channel of the mounting cup.

In a previous application, published as GB-A-2246605 we disclosed and claimed 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. The middle laser 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.

In accordance with one aspect of the present invention, we have found that improved seals between an aerosol container and a valved mounting cup are obtainable using a plastic polymer having a flexural modulus, 1% secant, of at least about 70,000 psi (483 MPa) 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 (621 MPa) 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' is provided comprising 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 thermoplast cs In a preferred embodiment of the invention, the gasket material comprises a mixture of high density polyrthylene ("HDPE") and linear low density polyethylene ("LLDPE").The preferred HDPE is about 43% by weight of the gasket and the preferred LLDPE is atiout 57% iry weight of the gasket Ln ccc tain applications, it is also preferred I.o include a layer of thermal adhesive on the surface of the gasket material to lie in contact wi (ii the mounting cup.

In a further aspect. of the invention there is provided a gasketed mounting cup comprising a panel , a skirt integral with arrd depending from the per-iphery of the panel, the skirt. being outwardly flared lo florin an annular channel for receiving a container bead that defines a container opening; ancl a gasket disposed partially within the channel oE the 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 position on the mounting cup meet certain critical requirements.

Further aspect of the invention, including optimum values and ranges for critical dimensions of the position of the gasket on the mounting cup are discussed hereinafter with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a gasketed mounting cup provided with a polymeric gasket sea] in accordance with the present invent ion; Figure la is a cross-sectional view of the channel of tIIe gasketeci mounting cup of Figure 1, clinched to a container Ivead; 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 gasket ed mounting clip.

Referring to the deawings, Figure 1 shows a gasketed aerosol valve mount jug crip generally designated as 10 resting on a container bead 12 of F an aerosol container (not fully ly shown). Figure la j is an enlarged view of the channel portion 20 of the gasketed mounting cup 10 clinched In ttie container bead 12. The mounting cup ias a pedestal portion 14 which depends from the interior edge of a pane] portion 16.

A skirt 18 depends from the exterior- edge of the parlel portion 16 opposite the pedestal portion 14 and is concentric thereto. The top portion of the skirt 14 curves into an annular channel portion 20 which terminates in an edge portion 22. The channel portion 20, edge port: i on 22 and skirt 18 form an annular convex receptor for receiving the bead 12 of tile 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.K. Application Number filed simultaneously herewith.

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 (1.524 mm). 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-1" of the gasket as measured from the centre of the channel 20 of the mounting cup to the end of the second portion 24b is preferably at least 0.150 inches (3.81 mm) and is most preferably about 0.175 inches (4.445 mm). 1-1 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 numer-al "18" in Figur-e 1a. These preferred lengths ensure that the second portion 24b of Lhe gasket material 24 is properly positioned along the skirt 18 of the mounting cup 11 to provide seal.ing material in this critical region. If the radius r of the container bead 19 is larger than 0.06 inches (1.524 mm), a larger length D-1 would be required. If the radius r is smaller than 0.06 inches (1.524 mm), a shor-ter- length 1.-1 would be acceptable.

The gasket material 24 should be positioned far enough into the channel 20 of the mounting cup such tha t the diameter "d" o of the gasket flare, as measured at. title rnd of the firs portion 24a of ire gasket 24 through the centre of the mounting cup 10, as shown it Figure 1, is preferably greater than about 1.100 inches (2.794 cms). It is more preferably about 1 .200 inches (3.048 cms).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 clescr-ibecl in tire '525 and '948 patents) , referred to as its "cut length should be between about 0.250-0.285 inches (6.35-7.24nm). See Figure 2.

The gasket 20 is preferably between about 0.013-0.016 inches (0.33-0.41 mm) thick. It is most preferably 0.014 inches (0.356 mm) 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 70,000 psi (483 MPa) as measured by ASTM method D 790, and a hardness no gr-eater 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 the mounting cup 10 arid a container bead 12 when clinched. Preferably, the flexural modulus is at least about 90,000 psi (621 MPa) 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 thermoplast ic polymer. Sleeve gaskets are preferably positioned in accordance with the pr-ocess described in the i25 and '948 patents. Thermoplastics are preferred because they soften when heated arrd harden on cooling thus easing placement of the gasket witliiii the channel of the mounting cup arid the subsequent moulding of tht' gasket to conform with tlit' channel of the cup.

Suitable thermoplastic materials include polyethylenes, polypropylenes, other polyolefinic compounds such as 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 applical ion. The plastic also needs to have sufficient resistance to environmental stress to withstand the pressure and conipression forces endured by aerosol gaskets.Env i roilmrdnval stress crack resistances as measured by D 1693 of at yeast about 400 hours is preferred. The plastic needs to lie 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 Test Typical Property Method Value Tensile Strength (break), psi (MPa) D 638 3000 (20.7) Ultimate Elongation, % D638 > 800 Flexural Modulus, psi (MPa) D 790 100,000 (690) Tensile Strength (yield), psi (MPa) D 638 2750 (19.0) Brittleness Temperature, 'C D 746 < -95 Melt Index, g/10 minutes D 1238 0.6 Deflection Temperature at 66 psi (0.46 MPa) F ( C) D 648 140 (60) Vicat Softening Temperature, oF ( C) D 1525 244 (118) Bulk Density, lbs/ft (g/cm3) D 1895 35-37 (0.56-0.59) Density at 73 F (23 C), g/cm3 (compound) D 1505 0.939 Environmental Stress Crack Resistance D 1693 > 2000 10 lgap, F20 Hours (ASTM D 1693 cond. B) Durometer Hardness, Short "D" D 2240 56 Linear Thermal Coefficient of Expansion D 895 1.20 x 10- in/in/ C(-30 C to +30 C) Izod impact, ft - lbs/in (j/m) notch 230C D 258 2.3 (123) Melting Point, 'C 126.3 Crystallization Point, 'C 112.8 The gasket can also comprise a mixture of a fir-st plastic material providing sufficient stiffness to maintain Lhe 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 (483 MPa), as measured by ASTM method D 790, and preferably at least about 90,000 psi (621 MPa). 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 wil] have higher- density than the sofLer 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 str-ess to withstand the pressure and compression forces endured bv aer-oso] container gaskets. As above, environmental stress crack resistance orat least about 400 is preferred. The plastic much be resist-ant to cold flow, as well.

Suitable stiffer materials include HDPE, other stiff polyethylenes such as LLDPE of suitable molecular weight, polyamides, p o l y c a r b o n a t e s, p o l y p r o p y l e n e s, p o l y e s t e r s, acrylonitrilebutadienstyrenes ("ABS"), or acetyls.The flexural modulus of the stiffer materials is greater than 70,000 psi (48 'l!a) as measured as described alcove and is preferably greater that 90 ,()0() psi (621 MPa). Suitable softer materials ls 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, arid is pi-eferably below 56.

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

The relative quantity of the softer and stiffer plastic materials combined to form the mixtrire 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 utilised 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% to 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 utilised.

The preferred stiffer material is HDPE having a flexural modul.us of at least about 140,000 psi (965 MPa). A higher flexural modulus is even more preferr-ed. The preferred IIDPE is Altavene 6200B I1DPE, available from Plastics Del Logo, C.A. Venezuela. Preferably, the LLDPE has a hardness no greater than about 55 and more pr-eferahly no greater than about 50. The preferred LLDPE is DNDA-7340 Natur-al 7 ("DNDA-7340"), available from Union Car-bide.

Typical property data for the preferr-ed HDPE and LLDPE appear below: Altaven, R 6200B Properties Covenin ASTM Typical Value Method Method Melt Index 1552 D 1238 0.40 g/10 min Density - D 1505 0.0958 g/cm3 Yield Strength 1357 D 638 280 Kg/cm2 Tensile strength at 1357 D 638 320 Kg/crn2 break Elongation at break 1357 D 638 .500% Izod Impact Strength 822 D 256 12 Kg. cm/cm Environmental - D 693 > 400 hours cracking resistance Flexural Modulus 1% D 790 145,000 psi; 1000 Mpa Secant Hardness D 2240 66 DNDA-7340 PROPERTY TEST METHOD TYPICAL VALUES Melt Index D 1238 0.8 g/10 minutes Dens i ty D 1505 0.920 g/cm Flexural Modulus 1% D 638 34,000 psi; 234 MPa Secant Tensile Strength D 638 2,250 psi;15.5 MPa Ultimate Elongation D 638 500% PROPERTY TEST METHOD TYPICAL VALUES Bent Strip Crack resistance hrs ,F 100% "Igepal" D 1693 > 500 10% "Igepal" > 500 Brittleness D 746 Below -1000C Flex. Life, Cycles to UCC Method 140,000 Fail Minimum Shear Rate To UCC Method 4,000 Melt Fr-acture, sec Hardness D 2240 -45 With the preferred HDPE and LLDPE described above, mixtures within the range 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 R 6200B, is currently being used.

Alternatively, a soft material, such as LLDPE, cari lie stiffened, increasing its flexur-al modulus by the addition of inorganic filler or filier. Fiberglass fiber, glass beads, talc, or calcium carbonate are suitable additives. Coupling agents may be requiljtl lo bond the inorganic filers to the organic base material as is known in aae art.

In certain applications, such as where propellant is inserted into the container at lri.gh pressure after the product has been inserted, an adhesive is preferably used to further secure the gadked of the invention to the mounting cup. If t.he gasket is of the sleeve type, applied iti accordance with the process of the v ri)?) and 9l8 patents, it is further preferred to use a thermal adhesive. The thermal adhesive prevents the gasket from prematurely bonding to the mounting cup, prevent ing its advancement into its final pos i I ion partially within the channel 20 of the mounting cup 10.Heating of Lhe mounting cup pr-ior 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 Escor acid terpolymer ATX 325 ("ATX 325"), about 35.67% DNDA-7340 and 0.66% G, 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 (0.019 mm) thick.Typical property data for ATX 325 appear below: ArX 325 PROPERTIES ASTM METHOD VALUES Melt Index D 1238 (E) 20 g/10 min Acid Number- Exxon Method 45 Milligrams KOH/gm polymer Density D 792 0.942 g/cc Tensile Strength D 638 1200 psi (MPa) (8) Elongation % 1)638 (Compression Molded Type IV specirnens, cross head speed 2 in/min (5.1 cm/min)) 1800 Flexural Modulus D790 1300 psi (MPa) (9) Tensile Impact, ft-lbs/inZ (KJ/m)&commat;; 730F (230C) 350 (735) -430F (-400C) 255 (535) Hardness, Shore D D 2240 21 PROPERTIES ASTM METHOD VALUES DSC Melting Point D 3417 149 (65) oF (0C) Viscat Softening Point D 1525 140 (60) F (0C), 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 Atlaven" HDPE 6200B were added to a 1D Banbury Mixer with a capacity of 30 pounds (13.62 Kg) 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 F (193-204 C) by the end of the mixing period. The mixture was then conveyed to a Farrel 41/2 inch (11 .4cm) extruder, preheated to about 400-420 F (204-216 C).The mixture was discharged from the extruder at a rate of about 600 pounds per hour (272 kg/hr) 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 suspected 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% liy weight of ATX 325, about 35.67% by weight of DNDA-7430 LLDPE and 0.55% liy weight of H.Kohnstamm PB 3962 blue colorant were added to the Banbury mixer and irtixed for 2 minutes, up to 300-320 F (149-160 C). Tlte mixture was then conveyed to an extruder and extruder at a rate of about 600 pounds per hour 272 Kg/hr at between 300-320 F (149-160-C). [t was then pelletized as above. The thermal adhesive and sleeve gasket we-e coextruded into a tool where the layers were nierged, as is known iri the art. The gasket material was approximately 0.014 inches (0.36mm) thick while the layer of thermal adhesive, which is local wed on the Inside surface of the sleeve gasket material, was approximately 0.00075 inches (0.019 mm) 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 utilised 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 1500F (65.50C) and preferably about 1700F (76.70C) as measured on the raceway about 1 foot (30.5 cm) from the punch station, less than one second after the final positioning of the gasket within the channel of the mounting cup, is utilised. This is a convenient point to measure the temperature. It is believed that the temperature of the mounting cup is 20 - 300F (11 170C) higher while the gasket is being advanced to its final position on the mounting cup. At 1700F (76.70C) the gaskets 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 income too soft.

However, mixtures including higher percentages of IODIZE 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 wilhin the channel 20 of the cup, yielding the pr-c fer-red gasket flare d, as shown irk Figure 1. A shoulder 34 is provided to engage the top of the second portion 241) 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 for-ni the dimples 26 shown in Figure 1 and described further in the said application filed simultaneously linrewi th.

Comparative tests of the gasket in accordance with the preferred embodiments oE the pr-esent invention with conventional gaskets of LLDPE have shown that the gasket of the present invention is mor-e 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 consider-ed a representative test sample. The maximum pressure where none of the 12 test gaskets failed ("P1") and the minimum pressure that causcd all 12 to fail ("P2") were determined A failure is a blown gasket. A higher P1 indicates better resistance to blown gasket failure while a small difference between P1 arid P2 indicates consistent product performance. The pressure of the cap 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 P1 was determined. Then the pressure was increased until all 12 gaskets failed.P1 and P2 can be converted into load for-ces by multiplying the pressure values in the air cylinder providing the voice against the cap seal liy 12.5, which is the approximate are of the cylinder in inches.

For gaskets of LLDPE, adrered to the mounting cup by the therma adhesive described above, at a filling pressure of 600 psi; 4.14 MPa P1 = 14 psi; 96.5 kPa (175 lbs; 79.5 kg) and P2 - 28 psi;193 kPa (3)0 lbs;159 kg). At a filling pressure of 800 psi;5.5 MPa P1 = 10 psi 69kPa (125 lbs;57 kg) and P2 = 24 psi; 165 kPa (300 lbs;136 kg).

For gaskets of Altaven R 6200B and i)NDA-7340 of 43% and 57%, respectively, bondetl to t:he mounting cup by tlre thermal adhesive described above, at a filling pressure of 600 psi 4.14 MPa; both P1 and P2 = 28 psi;1 93kPa (350 lbs; 159 kg).

These results demonstrate that the gasket mater-ial 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 (5.7 mm), comprised entirely of LLDPE and adhered to the mounting cup by the thermal adhesive described above, at a filling pressure of 600 psi;4.14MPa P1 = 10 psi;6.9kPa (125 lbs;57kg) and P2 = 28 psi;193kPa (350 lbs;159kg). At a filling pressure of 800 psi;5.5MPa P1 = 8 psi;55kPa (100 lbs) 45.4kg) and P2 = 26 psi; 179kPa (325 lbs;148kg).

At a height of 0.250 inches (6.35 mm), all other variables being the same as above, at a filling pressure of 600 psi;4.14MPa lil = 14 psi; 96.5 kPa (175 lbs; 79.5 kg) and P2 = 28 psi;193kPa (350 lbs;159kg).

At a filling pressure of 800 psi; 5.5 MPa P1 = 10 psi;68.9 kPa (125 ll)s;57kg) and P2 = 24 psi;165kPa (300 lbs;136kg).

AL a height of 0.275 inches (7 mm), all other variables being the same as above, at a filling pressure of 600 psi;4.14MPa P1 = 14 psi;96.5 kPa (175 lbs; 80.5 kg) and P2 = 28 psi;193kPa (350 ]bs;1i9kg).

At a filling pressure of 800 psi; 5.5 MPa) P1 = 12 psi; 82.5 kPa (150 lbs;68kg) and P2 = 18 psi; 124 kPa (225 lbs;102kg).

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 (6.9 mm) bonded to the mounting cup by the thermal adhesive described above, and a cup temperature of 154 F (68 C), applied with a two piece punch, aL filling pressure of 600 psi; or 4.14 MPa P1 = 14 psi; 96.5 kPa (175 ll)s 179.5kg) and P2 = 28 psi; 193 kPa (350 lbs; 159 kg). At a filling pressure of 800 psi; 5.5 MPa P1 - 12 psi; 82.5 kPa (150 lbs;68kg) and P2 = 18 psi;124 kPa (225 lbs; 102 kg).

With the one piece punch of Figure 3, all other variables being equal, at a filling pressure 600 psi;4.14kPa P1 - 16 psi; 110 kPa (200 ibs;91kg) and P2 = 26 psi;179kPa (325 lbs;148kg). At a filling pressure of 800 psi; 5.5 MPa jl = 14 lbs; 6.4 kg) 14 psi;95.5kPa (175 lbs; 79.5 kg) and P2 = 24 psi; 165 kPa (300 lbs;136kg).

The preferred characteristics of material, thermal adhesive, cut 1 length and punch design each demonstrated improved resistance to dislodgement and consistency of perforntaroce. Taken together, the preferred characteristics yield a superior gasketed mounting cup.

Claims (31)

1. A polymeric gasket for use in sealing an aerosol mounting cup to the bead of an aerosol container and which is constructed from a polymeric material having a flexural modulus, 1% secant, of at least about 70,000 psi (483 MPa) 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. A gasket according to claim 1, wherein said polymeric material has a flexural modulus greater than 90,000 psi (621 MPa).

3. A gasket according to claim 1 or 2, wherein said polymeric material has a hardness of about 56 or less.

4. A gasket according Lo claim 1, 2 or 3, wherein tire polymeric material is thermoplastic.

5. A gasket according to any one of claims 1 to 4, wherein the gasket is in the form of a sleeve.

6. A gasket according to claim 5, wherein the sleeve has a length of from 0.250-0.285 inches (6.35-7.24 mm).

7. A gasket according Lo any one of the preceding claims coated on at least one surface by a layer- of thermal adhesive.

8. A gasket according to any one of the preceding claims, wherein said polymeric material is polyethylene, polypropylene, ethylvinylacetate (EVA) copolymer, ethyl vinyl alcohol copolymer, propylene ethylene copolymer, elastomer modified polyethylene, a polyamide, polyurethane, polyester, ionomer or polycarbonate.

9. A gasket according to any one of claims 1-7 in which the polymeric material is a mixture of a first polymer arid a second polymer in proportion such that the mixture has a flexur-al modulus 1% secant, of at least about 70,000 psi as measured by ASTM method I) 790 and a hardness no greater than about 60 Shore D as measured by ASTM method D 2240.

10. A gasket according to claim 9, wherein said first polymer is HDPE, a stiff polyethylene, a polycarbonate, polypropylene, polyester, acrylonitrilebutadienstryrene, copolymer or an acetal, and the second polymer is a soft polyethylene, an ethylene-ethyl acrylate copolymer, or a polyester, polyurethane or thermoplastic elastomer.

11. A gasket according to claim 9, wherein said polymeric material is a mixture of a high density polyethylene (HDPE) and a linear low density polyethylene (LLDPE).

12. A gasket according to claim 11, wherein the polymeric material containers from 38%-48% by weight: HDPE and from 52%-62% by weight LLDPE.

13. A gasket according to claim 11, wherein the polymeric material contains about 43% by weight HDPE and about 57% by weight. LLDPE.

14. A gasket according to claim 12 or 13, wherein the LLDPE component is an LLDPE having the properties hereinbefore set out under the Trade Name DNDA-7340.

15. A gasket according to claim 12, 13 or 14, wherein tlte HDPE component is an HDPE having the properties hereinbefore set out under the Trade Name Altaven 6200n.

16. A gasket va]ve mountillg cup for an aerosol container, said cup comprising a panel, a skirt integral with an depending from the periphery of the panel, the skirt being outwardly flared to form an annular channel for receivirig a container bead that defines a contained opening; arid a polymeric gasket disposed at least partially within the channel of the mounting cup wherein the gasket is a polyrtier-ic gasket as claimed in any one of the preceding claims.

17. A gasketed valve mounting cup according to claim 15 or- 16, wherein tween the gasket is secured to the mounting cup by a layer of thermal adhesive.

18. An aerosol container having a valve mounting cup mounted o the rim of the container and sealed thereon by means of a polymeric gasket located between the cup and the rim of the container, wherein there is used a polymeric gasket as claimed in any one of claims 1-14.

19. An aerosol container having a gasketed valve mounting cup sealingly engaged on the rim of the container, wherein the gasketed mounting cup is a gasketed mounting cup as claimed in claim 15, 16 or 17.

20. A polymeric material for use in the construction of a gasket according to c]aim 1, said polymeric material having a flexural modulus 1% serant, of at least 483 MPa, as measured by ASTM method D 790 and a hardness no greater than about 60 Shore D, as measured by ASTM method D 2240.

21. A polymeric material according to claim 20 having the properties or composition as required hy any one of claims 2-4 or 7-14.

22. A gasket material for sealing a channel of a valve mounting cup to the head of an aerosol container, said material comprising a mixture of a Fl r-st plastic material having sufficient stiffness to maintain I the gasket in position partially within the channel of the mounting cup and a second plastic material having sufficient softness to provide the sea].

23. \ gasket for sealing a chancre 1 of a ' it ve mounting cup Lo the bead of an aerosol container, said material compr-ising a mixture of a stiffer thermoplastic material and a softer thermoplastic material.

24. A sleeve gasket for- sealing a channel of a valve mounting cup to the bead of an aerosol container, the gasket having a cut length of from 0.250-0.285 inches (6.35-7.24 mm).

2r. A gasketed valve mounting cup For air aer-osol container, said cup comprising a panel, a skirt integral with arid depending from the periphery of the panel, the skirt being outwardly flared to form an annular channel for receiving any bead formed around the rim of the container, the annular channel having a polymeric gasket positioned therein for forming a seal with the rim of the container, the gasket 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 centre 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 (3.8 mm).

26. A gasketed mounting cup according to claim 25, wherein the length of the gasket is about 0.17 inches (4.5 mm).

27. A gasket mounting cup according to claim 25 or- 26, wherein the diameter of the gasket is measured at the end of the first portion of the gasket through a centre oE the mounting cup is at least 1.100 inches (2.79 cms).

28. A gasketed mounting cup according to claim 27, wherein said diameter is at least about 1.180 inches (3 cms).

29. A gaske I.ed mounting cup accord irig to claim 28, wherein sa id diameter is about 1 .200 inches (3.05 cms).

30. A gasketed mounting cup according to any one of claims 25-29, wherein the end of the first port ion of the gasket is at. about ttie 10 o'clock position within the annular channel of the mounting cup.

31. A gasketed valve mounting cup for an aerosol container, said cup comprising a panel, a skirt integral with and depending from the periphery of the panel, the skirt being outwardly flared to arid from an annular channel for receiving a bead formed around the rim of the aer-osol container, the annular channel having a polymeric gasket positioned ther-cin, said gasket having a first portion partially disposed within the channel of the mounting cup and a second por-tioro partially disposed along the skirt of the mounting cup, the first ad second portions each having an end, the gasket having a length measured from the centre 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 (3.8 mm) and a diameter, as measured at the end of the first portion through the centre of the mounting cup, of about 1.200 inches (3.05 cms).