Note: Descriptions are shown in the official language in which they were submitted.
WO 93/12901 PCr/US92/11184
2130~52
IMPROVED GASKET FOR AN AEROSOL MOUNTING CUP
Backaround
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
~15 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 rec~iving a
dispensing valve assembly. A closure, commonly referred to
~20 as a mounting cup, 6erves a~ the closure for the container
and a~ a ~upport 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 annul ar channel portion extending outwardly
from the skirt. When the mounting cup is placed in seàling
position on the container, the channel is positioned over
the bead surrounding the container opening and the lower
portion of the skirt ad~ acent to the channel i8 flared or
~30 clinched outwardly against the underside of the bead. To
`
WO 93/12901 PCI'/US92/11184
~ r ~
213035Z -2-
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
-5 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 aup in the preferred position for effecting a seal
between the mounting cup and tbe bead of the container, in
an exceptionally rapid and efficient manner to form
g~sketed-mounting cups having excellent sealing
characteristics In general, the method of invention of the
'525 and '948 patents comprises passing a tubular sleeve of
ga~ket material onto ~ compre~ible mandrel initially ~`
positioning ~nd aligning the skirt of th~ mounting cup and
th~ contiguou~ end of th~ mandr~l such that th~ sl~v~ of
ga~kot mat~rial m~y p~B8 onto the skirt, ~aid 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 slQeve at a point between the mounting
cup and the mandrQl to l-ave a band of gasket material and
subs-qu-ntly, advan¢ing the mounting cup to a station
whereat the band o~ the gasket material is urged further
'
W093/12901 PCT/US92/111~
2~30352
~ 3 ~ ~ r ~
onto the skirt of the mounting cup, whereby, the band of
gasket material does not extend beyond the skirt of the
mounting eup. Subsequently, the gasket is advaneed to the
desired position partially within the channel of the
mounting cup. The '52S and '948 patents are ineorporated by
referenee herein.
The dip tube of the eontainer is usually slightly
longer than the height of the eontainer to insure that its
end i~ position~d at the bottom of the eontain~r. As shown
in Figur- 1, wh-n th- mount~ng eup i- po~ition-d on th-
eontainer bead, the dip tube is slightly bent. This ean
provide an upward foree whieh ean displaee the mounting eup
from the eontainer bead, interfering with proper elinehing.
To ensure that the mounting eup is maintained on the
eontainer bead prior to elinehing, protrusions are ereated
.
around the skirt of the mounting eup whieh are below the
eontainer bead when the mounting eup is in position. Such
protrusions 14a are also shown in Figure 1. The force
provided by the bent dip tube is generally insuffieient to
overcome the retaining force provided by the protrusions.
The protrusions are formed by a tool placed around the
pedestal of the mounting eup, which forces out particular
seetions of the skirt of the eup.
~n the United States, aero~ol eontainers are typieally
filled by the undercap fill~ng m thod. First, the produet
to be di~pQnsed i8 d~posit~d lnto the eontainer. Then a
mounting cup, including the valve and dip tube, i8 plaeed on
WO 93/12901 PCI/US92/11184
~ r ~ . - 4 -
;~035?
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 encompasse6 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 iæ 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 ~blownn gasket.
Gasket displacements are more likely with the low
d~nsity polyet~ylene (nLDPE~) com~only used to form such
gaskets. Replacement of LDPE with high density polyethylene
(~HDPE~) yields a less effective seal because ~he 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 thickne~s.
Thi~ varlation in gasket thicXn-ss among the several gasket
~ystems, further complicated by the fact that the channel
portion of the mounting cups manufactured by the valve
WO93/12~1 PCT/US92/111~
Z~3035Z
-5-
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 undetect~d until ultimately di~covered 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. Patènt 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. G8 2,206,650, also assigned to the assignee of
the patent invention, a thermal adhesive is disclosed which
adheres the gasket to its ~inal position partially within
the channel of the mounting cup.
In U.S.S.N. 07/552,299, filed on July 18, l990 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 so~ter plastic
material ad~acent both sides of the middle layer i8
dis~losed. The middle layer is preferably HDPE while the
inner and outer layers are preferably LLDPE. Such a gasket,
wbile producing ~uperior results, requires additional
W093/12901 ` PCT/US92/11184
21~35~ -6-
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 muQt be low in C08t to enable aerosol product~ to
b- competitive with non-aerosol products in tbe consumer
market.
Summary of the Invention
In one aspect of the present invention, a plastic
polymer is disclosed having a flexural modulus, 1% secant,
~15 of at least about 70,000 p8i as measured by ASTM method D
790 and a hardness no greater than about 60 Shore D as
measured by ASTN 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
softèr pla~tic material which mixture meets the flexural
;~ 25 modulu~ and hardnQss limits de~cribed above. As above, the
gasket i8~ preferably a 81eeve type gasket and the plastic
material~ are thermopla~tic~.
WO93/12901 2130352 PCT/US92/11184
-7- i';A~ &~
In a preferred embodiment of the invention, the gasket
material compri~es 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
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 a~pect of the invention there is a
gasket-d 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
lS 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
2Q position on the mounting cup meet certain critical
requirements.
In a further a~pect of the invention, optimum values
and ranges for critical dimensions of the position of the
gask~t on th- mounting cup ar di~clo~ed.
~ '
W093/12901 "i'~ ,' PCT/US92/111~
21~0352 -8-
Description of the Fiaures
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 i8 a cross-sectional view of a portion of a
gasket prior to its being advanced into the channel of a
mounting cup; and
Figuro 3 is a cros--sectional view of a portion of the
punch preferred for us- in manufacturing the gasketed
~ounting cup o~ th~ pre~Qnt invantion
Figure 1 ~how~ a ga~ketod 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 pèdestal portion 14 and is concentric thereto
The top portion of the skirt 18 CUrVQS into an annular
; 25 channel portlon 20 whlch term1natQs in an edge portion 22
,
Th~channol porti*n 20, odgo portion 22 and skirt 18 form an
annular concav- r-coptor for racei~ng the bead 12 of the
WO93/12901 2~30352 PCT~US92/111~
~ r,~ ,rDf ~
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 al80 has a second port~on 24b in
contact with the 6kirt 14 of the mounting cup 10. Al~o
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 nL-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 i5 most preferably
about 0.17~ inches. L-l is shown in Figure 1. It has baen
found that for optimum s~aling, it is necessary`to have
sealing material in the region between the skirt 18 and thQ
container bead 12 proxi~ate numeral ~18~ in Figure la.
These preferred lengths ensure that the second portion 24b
W093/12901 '~ ~ ~J ~: PCT/US92/11184
2~30352 -lo-
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 24~ 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.
~uch placement of the g~sket ~how~ improved res~stance to
dislodgement from the channel 20 of the mounting cup 10.
To achieve t~ preferred flare diam~ter, the length ~-
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 ~.250-0.285 inches.
See Figure 2.
The gasket 20 is preferably between about 0.013-0.016
inches thick. It i8 most preferably 0.014 inches thick.
-~ While it i~ preferred to utilize these dimensions with
the preferred gasket material described below, these
,
.~0 93/12901 2~.3035Z PCI/US92/11184
--1 1--
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 proce~s 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 p8i as measured by ASTM method D 790, and a
hardne~ no greater than about 60 Shore D a~ measured by
ASTM mQthod D 2240~ Such a material ha~ a ~tiffnes~
sufficiQnt to maintain th~ ga~k~t in position part$ally
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 hard~n on cooling,
retaining their shapo confor~ing to the chann~l of the cup.
Suitable thQrmoplastic ~aterials include polyethylenes,
polypropylenes, other polyolefinic compounds s=ch as
.
i;A~. ~t
W093/129~1 ~;ff~ , PCT/US92/111
2 ~ 30 3~2 -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 1~93
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 t~DEHD~), a polyethylene
available from Union Car~ide, 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 Carbidë. Typical property data for
DEHD follows:
DEHD
Test Typical
Property Method Value
Tensile Str~ngth ~br~ak),
pBi (MPa) D 638 3000 (20.?)
Ultimate Elongation, ~ D638 ~800
Flexural ~odulus, psi (NPa) D 790 100,000 ~690)
WO 93/t2901 Z13035~ PCT/US92/111~
DEHD ~Cont~
Test Typical
Property Method Value
Tensile Strength (yield),
psi (MPa) D 638 2750 (l9.0)
Brittleness Temperature, ~C D 746 ~-95
Melt Index, g/lO minutes D 1238 0.
Deflection Temperature at 66 psi
(0.46 MPa) F (C) D 648 140 (60)
Vicat Softening Temperature,
F (-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
lO lgap, ~20 Hours
(AS~M D 1693 cond. B)
Durometer Hardness, Short ~D~ D 2240 56
Linear Thermal Coefficient of
`Expansion D ~95 1.20 x 10-4
in/in/-C(-30C to +30~C)
Izod impact, ft - lbs/in (j/m)
notch 23~C D 258 2.3 (123)
M~ltin~ Point, ~C 126.3
Cry~talliz~tion Point, C 112.8
The gasket can also comprisa a mixture o~ 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 pro~ide a reliable seal between the
WOg3/12901 PCT/US921111~
2130352
-14-
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
- 5 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 d eeve gasket, the polymers forming the
:
mixture arQ prefQrably thermoplastics. The mixture should
have sufficient resistance to environmental stress to
withstand the pressure and compression forces endured by
a-rosol cont~iner gaskQt~. As above, environmental stress
crack resi~tanc- of at lea~t about 400 ~8 pref-rrQd. The
plastio ~u-t b- r--1-tant to cold ~low, a~ w ll.
Suitable stiffer materials include ~DPE, 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 æofter materials include
æome polyethylenes and other polyolefins, ethylene-ethyl
ac ylate copolymer, poly-sters, polyurethanes and most other
the plastic lastomers. The hardne~s of the softer
mat-rials is 1-8~ than 60 as ~easured as described above,
; and i8 pr-f-rably below 56.
WO93/12901 PCT/US92/111~
2~30 ; . ., !
-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
t~erefore vary depending on the application. Suitable
S mixturs~ 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
mcdulus of at lsast about 140,000 psi. A higher flexural
modulus is even more preferred. The preferred HDPE is
Altav n~ 6200B HDPE, available from Plastics Del Logo, C.A.
Venezuela. Preferably, the LLDP~ has a hardness no greater
WO93/12901 ~ PCT/US92/111
2 ~ 30 3r~Z -16-
than about 55 and more preferably no greater than about 50.
The prefQrred LLDPE is DNDA-7340 Natural 7 (~DNDA-7340~),
available from Union Carbide.
Typical property data for the preferred HDPE and LLDPE
appear below:
Altav~n~ 6200B
Covenin ASTM Typical
Properties Method Method Value
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
Tensi}e strength
at break 1357 D 638 320 Kg/cm2
:Elongation at break 1357 D 638 >500%
-~ Izod Impact strength 822 D 256 12 Xg. cm/cm
; Environmental cracking
resistance - D 693 >400 hours
Flexural Modulus
1% Secant D 790 . 145,000
Hardness D 2~40 ~66
DNDA-7340
Propertv Test Method ~vpical Values
Melt Index D 1238 0.8 g/10 minutes
Density D 1505 0.920 g/cm
Flexural Modulu~
.1% Secant D 638 34,000 psi;234
Mpa
Tensil~ Strength D 638 2,250 psi:l5.5
Mpa
,~ .
W093/12901 2130352 PCT/US92/111~
--17-- ~,, 1', tr ! X~;
DNDA-73~0 ~oont~)
Property Test Nethod Typical Values
s Ultimate Elongation D 638 500 %
Bent Strip
Craek Resistanee,
hrs~X~ F
100% ~Igepal~ D 1693 >500
10% ~Igepal~ >soo
Brittleness Temperature D 746Below -
lOO-C
Flex. Life, Cyeleæ
to Fail UCC Method 140,000
20Minimum Shear Rate
To Melt Fraeture,
see~1 UCC Nethod 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
eurrently 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 organie base material, as is known in the
art.
In eertain applieations, sueh as where propellant is
inserted into the eontainer at high pressure after the
produet has been-inserted, an adhesive is preferably used to
W093/12901 ~ $ PCT/US92/1t184
213035Z -18-
further secure the gasket of the invention to the mounting
cup If the gasket is of the sleeve type, applied in
accordance with the proceæs 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
lO 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 h at ourc-, the temp-rature of th~ mounting cup drops
to room temperature and the thermal adhesiv~ bonds the
gasket to the mounting cup
Pr~f~rably, tho adhe~ive is a mlxture Or about 64 67%
Exxon Escor acid terpolymer ATX 325 (~ATX 325~), about
35 67% DNDA-7340 and O 66% H Xohnstamm 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 Typicai property
data for ATX 325 appear below
AT~ 325
25PROPERTIES TM METHOD VA~UES
Molt Ind~x D 1238(E) 20
- g/10 ~ln
, ;, ~ .
93/12901 2~30352 PCT/USg2/11184
-19- ~a`~
ATX 325 (cont~
PROPERTIES ~STM METHOD VALUES
Acid Number Exxon Method 45
Milligrams KOH/gm polymer
Density ~ ~ 792 0.942
10 g/cc
Tensile Strength D 638 1200
psi (MPa) (8)
15Elongation % D 638
~Compression Molded
Type IV specimens,
crosæhead speed 2
in/min (5.1 cm/min)) 1800
Flexural Modulus D 790 1300
psi (MPa) (9)
Tensile Impact, D 1822(S)
25ft-lb /in2 (XJ/m2)~
73-F (23-C) 350
(735)
-43-F (-40-C) 255
(535)
Hardness, Shore D D 2240 21
DSC Melting Point D 3417 149 (65)
F (-C)
Viscat Softening Point D 1525 140 (60)
F (-C), 200 g load (Rate B)
To form the preferred gasket of the invention, about 57%
by weight of DND~-7340 LLDPE and about 43% by weight of
Altaven~ HDPE 6200B were added to a lD Banbury Mixer with a
capacity of 30 pounds and mixed for about 2.5 minutes. Such
a mixQr i~ available from Farrel Machinery, for example.
The mixing ~tarted at room temperature and reached 380-
400-F by the end o~ the mixing period. The mixture wa~ then
conveyed to a Farrel 4t inch extruder, preh-ated to about
WO 93/12901 r ~ PCr/US92/1 1 184
2i3035Z
-20-
400-420F. 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
- 5 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.
~;~ 10 To form the preferred thermal adhesive, about 64.67% by
weight of ATX 325, about 35.67% by weight of DNDA-7340 LLDPE
and O.S5% by weight of H. Xohnstamm PB 3962 blue colorant
were ~dded 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 rat~ of about 600 pounds per hour at
between 300-320'F. It was then pelletized as above. The
thermal adhe~ive and sleeve gasket were coextruded into a
tool where the layers were merged, as is known in the art.
The gasket material wa~ approximately 0.014 inche~ thicX
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 i~ prefer~bly positioned on
the mounting cup a8 g~n rally de~cribed in the '525 and '948
patents. a singl~ station gagket ~ounting cup assembly
~:'
W~93~12901 2130352 PCT~USg2/~
-21-
machine is utilized instead of the six station assembly
machine shown in Figure 3 of the '948 pat~nt It has been
found that the sleeve gasket material may be positioned on a
single mounting cup faster and more accurately than if
- 5 sleeve gasket material is concurrently positioned on BiX
mounting cups In addition, higher temperatures are
curr~ntly used than those disclosed in thQs~ patQnts
A mounting cup temperature of at least about 150 F and
pr~f~rably about 170 F, a- m asurod o~ th- rac-way about l
foot from the punch station, les~ 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 exten~ion 30a for engaging th~
end o~ tb- first portion 24a of th gasket 24 as it is being
adv~anc~d into the cbann~l 20 of th- mounting cup lO as shown
in Figure 3 The xtension 30a ensures that the gask t is
.
WO 93/12901 ! `' ~ PCI/US92/11184
2~30352 -22-
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. Eurther
details concerning the process and preferred puncb 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
con~entional gaskets of LLDPE have ~;hown that the gasket of
the present invention i~ more resistant to blown gasket
failure and has more consistent performance. The forces
applied to a gasket in the channel of th~ 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 WZIS placed on
the fixture and a cap E~eal, pres~ure 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 Imd cap seal
on the mounting cup, th mounting cup rose. Air then passed
between th~ channel of the mounting cup and the fixture,
, ~
W093/12901 ~30352 PCT/uS92/~
-23- ~ t
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
failed (~Pl~) and the minimum pressure that caused all 12 to
fail (~P2~) were det~rmin~d. A failure is a blown gasket.
A higher Pl indicates better resistance to blown qasket
failure while a ~mall difference between Pl and P2 indicates
consist~nt product porformanc~. The pre~sur~ of the cap
~eal wa~ varied ~uoh that if all 12 ga~kets did not pa~s the
tost, the pre~ure was lower~d. If all 12 p~ d, th-
pressure was raised until Pl was determined. Then the
pressure was increased until all 12 gaskets failed. Pl and
P2 can be converted into load forces by multiplying the
lS 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
600 psi, Pl = 14 psi (175 lbs) and P2 = 28 psi (350 lbs).
At a fillinq pressure of 800 psi, Pl = lO psi (125 lbs) and
P2 = 24 psi (300 lbs).
For gaskets of Altaven~ 6200B and DNDA-7340 of 43$ and
- 57%, respectively~ bonded to th~ ~ounting cup by the th~rmal
adhe~lv~ de~cr~b d a~ ve, at a filling pro~ure of 600 p8i,
both Pl and n - 28 p8i (350 lb~). At a ~illing pr~ure of
800 p~i, Pl - 26 p~i (325 lbs) and P2 - 28 p~i (3S0 lb~).
WO93/12901 PCT/US921111~
2~303SZ -24-
These results demonstrate that the gasket material of the
present invention is far superior to conventional ga6k~ts of
~DPE 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 imprQved 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, Pl s 10 psi (125 lbs) and P2 =
28 psi (350 lbs). At a filling pressure of 800 psi, Pl = 8
;; psi (100 lbs) and P2 = 26 psi (325 lbs).
- A~ a height of 0.250 inche~, all other variables being
the ~ame as above, at a filling pre~sure of 600 psi, Pl 5 14
psi (175 lbs) and P2 3 28 psi (350 lbs). At a filling
pressure of 800 psi, Pl = 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, Pl = 14
psi (175 lbs) and P2 = 28 psi (350 lbs). At a filling
pressure of 800 psi, Pl - 12 psi (150 lbs) and P2 = 18 psi
(225 lbs).
~omparative t~t~ varying th~ d~sign o~ the punch show~d
improved result~ with a one piec~ punch including an
extQnsion 30a for engaging the gaaket as shown in Figure 3,
;~ over a two piece punch. For a LLDPE gasket with a cut
.
W093/12901 PCT/US92/11184
21303S~
-25~ c~;
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, Pl = 14 psi (175 lbs) and P2 - 28 psi (350 lbs).
At a filling pressure of 800 psi, Pl z 12 pBi (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, Pl = 16 psi (200
lbs) and P2.= 26 psi (325 lbs). At a filling pressure of
800 psi, Pl = 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 togather, the preferred characteristics
yield a superior gasketed mounting cup.
