NZ619876B2 - Plastic aerosol container and method of manufacture - Google Patents
Plastic aerosol container and method of manufacture Download PDFInfo
- Publication number
- NZ619876B2 NZ619876B2 NZ619876A NZ61987612A NZ619876B2 NZ 619876 B2 NZ619876 B2 NZ 619876B2 NZ 619876 A NZ619876 A NZ 619876A NZ 61987612 A NZ61987612 A NZ 61987612A NZ 619876 B2 NZ619876 B2 NZ 619876B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- preform
- container
- neck finish
- thermally
- aerosol
- Prior art date
Links
- 239000000443 aerosol Substances 0.000 title claims abstract description 65
- 239000004033 plastic Substances 0.000 title claims abstract description 32
- 229920003023 plastic Polymers 0.000 title claims abstract description 32
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 7
- 238000000071 blow moulding Methods 0.000 claims abstract description 37
- 229920000642 polymer Polymers 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 14
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 14
- 239000003380 propellant Substances 0.000 claims description 10
- -1 polyethylene terephthalate Polymers 0.000 claims description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 229920000728 polyester Polymers 0.000 claims description 6
- 239000004952 Polyamide Substances 0.000 claims description 5
- 229920002647 polyamide Polymers 0.000 claims description 5
- 239000011528 polyamide (building material) Substances 0.000 claims description 5
- 238000002788 crimping Methods 0.000 claims description 4
- 230000003019 stabilising Effects 0.000 abstract 2
- 238000007789 sealing Methods 0.000 description 20
- 239000000463 material Substances 0.000 description 7
- 239000011324 bead Substances 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 239000004479 aerosol dispenser Substances 0.000 description 5
- 238000002425 crystallisation Methods 0.000 description 5
- 230000005712 crystallization Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000003860 storage Methods 0.000 description 3
- 239000004677 Nylon Substances 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive Effects 0.000 description 2
- 230000002708 enhancing Effects 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000001746 injection moulding Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229920001778 nylon Polymers 0.000 description 2
- 230000001105 regulatory Effects 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 238000005482 strain hardening Methods 0.000 description 2
- 229920001169 thermoplastic Polymers 0.000 description 2
- 239000004416 thermosoftening plastic Substances 0.000 description 2
- 239000004698 Polyethylene (PE) Substances 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000000295 complement Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 230000012447 hatching Effects 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000000977 initiatory Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 230000003278 mimic Effects 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 238000004642 transportation engineering Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B11/00—Making preforms
- B29B11/06—Making preforms by moulding the material
-
- B29B2911/1402—
-
- B29B2911/14326—
-
- B29B2911/14333—
-
- B29B2911/14913—
-
- B29C49/0073—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
- B29C49/06—Injection blow-moulding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/42—Component parts, details or accessories; Auxiliary operations
- B29C49/64—Heating or cooling preforms, parisons or blown articles
- B29C49/6409—Thermal conditioning of preforms
- B29C49/6436—Thermal conditioning of preforms characterised by temperature differential
- B29C49/6445—Thermal conditioning of preforms characterised by temperature differential through the preform length
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2077/00—Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D83/00—Containers or packages with special means for dispensing contents
- B65D83/14—Containers or packages with special means for dispensing contents for delivery of liquid or semi-liquid contents by internal gaseous pressure, i.e. aerosol containers comprising propellant for a product delivered by a propellant
- B65D83/38—Details of the container body
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
- Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
Abstract
plastic aerosol container (10) and method of manufacture is disclosed. The plastic container is made of a polymer which can be crystallised. The neck (16) of the container preform is thermally crystallized prior to blow moulding the body portion (13) of the container. This creates a pull point junction (19) from which strain orientation occurs begins during the blow moulding process. The neck finish (16) of the container is configured to receive an aerosol valve and closure (1). By thermally stabilising the neck finish (16) deformation in the neck region about the valve and closure (1) is prevented. junction (19) from which strain orientation occurs begins during the blow moulding process. The neck finish (16) of the container is configured to receive an aerosol valve and closure (1). By thermally stabilising the neck finish (16) deformation in the neck region about the valve and closure (1) is prevented.
Description
Plastic Aerosol Container and Method of Manufacture
FIELD OF THE INVENTION
The present invention relates to aerosol containers and more particularly to a plastic
aerosol container able to withstand the elevated pressures and temperatures of testing and
storage.
BACKGROUND
Aerosol containers are subject to problems such as creep, burst, and leakage. These
problems may be encountered when the containers are subjected to high temperatures and
pressures during packing, testing and/or storage. For reasons of public safety, the containers must
be tested to ensure compliance with regulatory guidelines directed to structural integrity.
According to one test, the aerosol container is filled at 130 psig (9.14 kgf/cm kilograms
force/centimeters squared) and then heated to131° F (55°C), causing the headspace pressure to
rise to 140 psig (9.85 kgf/cm ), or higher; the sealed container must withstand these conditions
without leaking or bursting over a time period selected to mimic the conditions of actual use and
storage. The pressures and thermal requirements associated with aerosol containers are much
greater than for containers made for other applications, such as food and beverage containers.
[0002a] Where the terms “compromise”, “comprises”, “comprised” or “comprising are used in
this specification (including the claims) they are to be interpreted as specifying the presence of
the stated features, integers, steps or components, but not precluding the presence of one or more
other features, integers, steps or components, or group thereof.
SUMMARY OF THE INVENTION
The problems of creep, burst, and leakage in plastic aerosol containers are solved in
accordance with one embodiment of the invention by providing a container with two specific
regions that together allow the container to withstand the severe testing and use requirements.
More specifically, applicant has discovered that the neck finish and its transition to the enlarged
container diameter is a source of the leakage and bursting problems with plastic aerosol
containers. As a result, the prior art containers are deforming in these regions, leading to a
loosening of the closure and/or valve assembly. Applicant solves this problem by providing a
crystallized neck finish which not only thermally stabilizes the finish but also solves the problem
of stretching the preform material properly below the neck finish during the blow molding
process. More specifically, crystallizing the neck finish provides a means to control a point at
which orientation begins during blow molding of the plastic aerosol container.
[0003a] In accordance with the present invention there is therefore provided a plastic aerosol
container comprising:
a thermally crystallized neck finish having a crystallinity of at least 5% configured to
receive an aerosol valve and closure assembly;
an expanded strain oriented aerosol container body integral with the neck finish; the
container body including a thermally uncrystallized shoulder and sidewall;
a junction between the thermally crystallized neck finish and the strain oriented container
body defining a pull point at which strain orientation begins; and
wherein the plastic aerosol container can withstand a hot water bath test under 49 CFR §
173.306 (a)(3)(v) without leakage or permanent deformation when filled 60% (of container
volume) with water and 40% nitrogen (as propellant) pressurized to 130psig.
The neck finish of a preform is thermally crystallized by heating, wherein preferably at
least the outer surface and most preferably the entire thickness of the neck finish is crystallized.
On the other hand, the body of the container is strain oriented during the blow molding process.
Accordingly, a junction between the neck finish and the body is created. The junction between
the neck finish and the body defines a pull point at which strain orientation begins. Controlling
the location of
the pull point by way of crystallizing the neck finish helps to provide full strain orientation under
the neck finish. As a result, the invention provides one or more of the following benefits: (1)
reducing the weight of the container; (2) reducing thermal distortion of the neck finish and of the
area under the neck finish; and (3) reducing stress cracking of the neck finish and area under the
neck finish.
In one embodiment of the invention, there is provided an aerosol container having a
thermally crystallized neck finish configured to receive an aerosol valve and closure assembly,
and an expanded strain oriented aerosol container body integral with the neck finish. A junction
between the thermally crystallized neck finish and the strain oriented container body defines a
pull point at which strain orientation begins.
In one embodiment, the container comprises at least one of polyester and polyamide.
In one embodiment of the invention, the container comprises polyethylene terephthalate
(PET).
In one embodiment, the neck finish includes a flange. The valve and closure assembly
includes a crimp, configured to connect the valve and closure assembly to the neck finish. In
other embodiments, the closure assembly and neck finish have complementary threads (a
threaded connection) and/or the closure and neck finish are secured by adhesives or the like.
In another embodiment, a method of making a plastic aerosol container is provided. The
method includes creating a pull point between a neck finish of a preform of crystallizable
polymer by thermally crystallizing the neck finish, and blow molding the body from the pull
point to form an expanded strain oriented container body, wherein the plastic aerosol container
comprises the crystallized neck finish and the strain oriented aerosol container body.
There is, in accordance with this aspect of the invention, provided a method of making a
plastic aerosol container from a preform of crystallizable polymer, the preform comprising:
an upper preform portion and a lower preform portion;
the upper preform portion including a neck finish configured to receive an aerosol valve;
the lower preform portion including a tapered shoulder configured to be expanded by
blow molding to form an expanded strain oriented shoulder of an aerosol container body;
the lower preform portion further including a sidewall configured to be expanded by blow
molding to form an expanded strain oriented sidewall of the aerosol container body;
the method comprising steps of:
creating a pull point at which strain orientation begins below the neck finish of the preform
by thermally crystallizing the preform neck finish to a crystallinity of at least 5% while the
lower preform portion including the tapered preform shoulder and sidewall remain
thermally uncrystallized; and
blow molding the lower portion of the preform from the pull point to form an expanded
strain oriented container shoulder, formed from the thermally uncrystallized tapered
preform shoulder, and an expanded strain oriented container sidewall, formed from the
thermally uncrystallized preform sidewall;
wherein the plastic aerosol container so formed can withstand a hot water bath test under 49
§ CFR 173.306 (a)(3)(v) without leakage or permanent deformation when filled 60% (of
container volume) with water and 40% nitrogen (as propellant) pressurized to 130psig.
In another embodiment, a preform for blow molding a plastic aerosol container is
provided comprising:
an upper preform portion and a lower preform portion,
the upper preform portion being thermally crystallized and including a thermally
crystallized neck finish having a crystallinity of at least 5% configured to receive an aerosol
valve;
the lower preform portion not being thermally crystallized and including a thermally
uncrystallized tapered shoulder configured to be expanded by blow molding to form an
expanded strain oriented shoulder of an aerosol container body;
the lower portion further including a thermally uncrystallized sidewall configured to be
expanded by blow molding to form an expanded strain oriented sidewall of the aerosol
container body;
a junction between the thermally crystallized upper portion and the strain oriented lower
portion defining a pull point from which strain orientation will begin on expansion by blow
molding; and
wherein a plastic aerosol container blow moulded therefrom can withstand a hot water
bath test under 49 CFR § 173.306(a)(3)(v) without leakage or permanent deformation
when filled 60% (of container volume) with water and 40% nitrogen (as propellant)
pressurized to 130psig.
In another embodiment of the invention, the preform is provided comprising at least one
of polyester and polyamide.
In another embodiment of the invention, the preform is provided comprising polyethylene
terephthalate (PET).
The neck finish may include at least one of a flange and a thread.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and further advantages of the invention may be better understood by referring
to the following description in conjunction with the drawings in which:
is a schematic illustration of an unassembled aerosol dispenser including a plastic
aerosol container having a thermally crystallized neck finish and expanded strain oriented body
portion according to one embodiment of the invention;
is a schematic illustration of the aerosol dispenser of in an assembled state;
is a schematic illustration of one embodiment of a crystallized neck finish and
crimp closure;
is a schematic illustration of one embodiment of a method of thermally crystallizing
the neck finish of a preform for making the plastic aerosol container of
is a schematic illustration of a blow molding process for making the plastic aerosol
container of
is a pressure and temperature trace for a plastic aerosol container undergoing a test in a
hot water bath;
FIGS. 7A and 7B are schematic illustrations of an alternative embodiment of a threaded neck
finish and closure; and
is a schematic illustration of an alternative embodiment of a neck finish with a transfer
bead.
DETAILED DESCRIPTION
Referring to the drawings, depicts an unassembled plastic aerosol dispenser 10 for
dispensing contents under pressure according to one embodiment of the invention. The dispenser 10
has three main parts; a container 12, a valve assembly 1, and a closure 30. Valve assembly 1 includes
discharge orifice 2, valve stem 3, actuator 4, dip tube 5, and a pump mechanism 6, mounted on
closure 30.
An aerosol propellant and an aerosol product are stored within the dispenser 10. The aerosol
propellant may be any of the propellants used for aerosol dispensers including liquefied propellants
such as hydrocarbons and hydrofluorocarbons and any of the compressed gases such as carbon
dioxide or nitrogen. The valve assembly 1 controls the flow of the aerosol product, which is pumped
via the pump mechanism 6 by means of actuator 4 from the container 12. The product enters the
valve assembly via dip tube 5 and travels through valve stem 3 for discharge through the discharge
orifice 2.
Container 12 includes an upper thermally crystallized portion 16 integral with a lower
biaxially strain oriented portion 13.
Upper crystallized portion 16 comprises a neck finish 18 having a top sealing portion 17. Pull
point 19 is a line of demarcation between upper crystallized portion 16 and lower oriented portion 13.
Top sealing portion 17 is provided at the top of the neck finish 18 for connecting the valve assembly
1 to the container 12 by means of the closure 30 (closure 30 is discussed in further detail in .
The neck finish 18 is substantially cylindrical and integral with a tapered shoulder 14, a cylindrical
sidewall 15 and a bottom wall 20 of lower oriented portion 13.
Lower oriented portion 13 includes a shoulder 14, a cylindrical sidewall 15, and bottom
portion 20. The top end of the shoulder 14 is integral with the neck finish 18. The tapered shoulder
14 generally increases in diameter in a downward direction and can be formed in any shape and
dimension as known in the art. The smallest diameter of the shoulder 14 at the pull point 19 is equal
to the diameter of the neck finish 18. The bottom end of the shoulder 14 is integral with the
cylindrical sidewall 15. The sidewall 15 is shown as having a cylindrical shape; however any shape
which accommodates a pressurized liquid or gas may be used. A bottom portion 20 is provided
integral with the bottom end of cylindrical sidewall 15 forming a closed bottom portion of the
container 12.
depicts the plastic aerosol dispenser 10 in the assembled state. As seen in the
closure 30 and valve assembly 1 is crimped to the top sealing portion 17 of the container 12.
Although illustrates a top sealing portion 17 having a flange, a flange is not required. Other
closure structures known in the art may be used. For example, instead of being crimped, the valve
assembly 1 may be fastened to the container 12 without crimping by means of an adhesive including,
but not limited to, glue, and/or by a threaded connection (see .
The upper crystallized portion 16 is thermally crystallized (see for further details
regarding crystallization of the neck finish), as indicated by the cross hatching. In the present
invention, the upper crystallized portion 16 has at least 5% crystallinity in order to provide thermal
and mechanical stability to ensure compliance with regulatory guidelines. More preferably, the upper
crystallized portion 16 is from about 20-40% crystallized. Most preferably, the upper crystallized
portion 16 is about 25-35% crystallized. The percent crystallinity is determined according to
American Society for Testing and Materials (ASTM) Standard D1505 as follows:
% crystallinity =[(ds-da) \ (dc-da)] x 100
where ds=sample density in g/cm , da =density of an amorphous film of 0% crystallinity (for PET
1.333 g/cm ), and dc =density of the crystal calculated from unit cell parameters (for PET 1.455
g/cm ).
Additionally, crystallizing the upper portion 16 improves the ability to achieve strain
orientation of the container 12 below the upper crystallized portion 16 during the blow molding
process.
illustrates an expanded view of one embodiment of an upper crystallized portion 16 of
container 12 and a schematic, cross sectional view of one embodiment of a closure 30. Closure 30
includes outer sealing rim wall 31, inner sealing rim wall 32, and top sealing rim wall 33, which
together form a cup-shaped sealing portion for attachment to the top portion of the neck finish 18.
The enclosure further includes, radially inwardly of the sealing portion, an annular depression or
trough 34, including opposing trough sidewalls 35A and 35B, connected by bottom wall 36. Radially
inwardly of the trough is an upwardly extending central projection 41 extending from wall 37, having
a central aperture 38, for attachment to the valve assembly.
In this embodiment the upper crystallized container portion 16 has a top sealing surface 22
with serrations 23. The serrations are formed during fabrication, e.g. while injection molding the
preform neck finish. The outer sealing wall 31, inner sealing wall 32, and top sealing wall 33 at the
rim of closure 30 fit around the flange 17 on the top of the neck finish 18. The outer wall 31 is then
deformed to wrap around the top flange 17 on the neck finish to form a hermetic seal. A resilient
(e.g. rubber or similar thermoplastic materials) gasket 27 is preferably provided between the top wall
33 and serrated top surface 22 of the finish to enhance the compressive seal.
Closure 30 also connects the valve assembly to the container 12. The valve assembly fits into
aperture 38 and may be attached by crimping (deforming) the closure wall35B to engage the valve
stem assembly.
Preform 44 of comprises an upper portion 45 and a lower portion 46. The upper
portion 45 comprises neck finish 18 with top sealing portion 17, same as in the container shown in
FIGS. 1-3. Lower portion 46 comprises a perform sidewall 47, a base 48, and a tapered shoulder 49.
According to the present invention, the upper portion 45 of the preform 44 is thermally crystallized,
while the lower portion 46 is not. The lower boundary line of crystallization of the upper portion 45
defines, at pull point 19, the initiation of stretching of the preform material below the neck finish 18
during the blow molding process.
depicts one method of thermally crystallizing the upper preform portion 45 before
the lower portion 46 is inflated during the blow molding process. The preform 44 is passed by a
heating element 43 to thermally crystallize the neck finish 18 (which includes the top sealing
portion 17). A thermal shield 42 prevents the lower portion 46 from exposure to heat, such that
the lower portion 46 of the preform 44 is not thermally crystallized. As thermal crystallization
will interfere with orientation due to stretching, this line of demarcation (the pull point 19)
between the crystallized upper portion 45 and the uncrystallized lower portion 46 of the preform
44 is highly desirable.
The neck finish 18 may be crystallized by any of the methods known in the art.
Generally, a finish portion may be thermally crystallized by placing the portion adjacent to a
heating element, such as a radiant heater, at a suitable temperature and for sufficient time to
crystallize the material in the area desired. In one embodiment, the heater may be positioned in a
range of from about 3/8 inches (0.95 cm) to about 2 inches (5.08 cm) from the neck finish, the
heater being at a temperature of from about 500°F (260°C) to about 1250°F (677°C), and the
crystallizing taking about 30 to 75 seconds. Adjustments to the time and temperature can be
made depending on preform materials and dimensions, including the desired depth and area of
crystallization. In accordance with the present invention, it is preferred to crystallize the entire
upper portion 45 of the preform 44 in order to control the point at which orientation begins
during the blow molding process.
The lower portion 46 of preform 44 may be any of the known shapes of preforms in the
art. Here it includes a tapered shoulder 49, a cylindrical sidewall portion 47 and a
semihemispherical, closed base 48. As is made clear by after the preform lower portion
46 is biaxially oriented during the blow molding process, the tapered shoulder 49 of the preform
44 corresponds with the shoulder 14 of the container 12, the body 47 of the preform 44
corresponds with the sidewall 15 of the container 12, and the base 48 of the preform 44
corresponds with the bottom 20 of the container 12.
For a typical polyester aerosol container of about 100 ml to about 1000 ml in volume, a
suitable planar stretch ratio is about 8:1 to about 13:1, with a hoop stretch of about 2:1 to about
4:1 and an axial stretch of about 2:1 to about 4:1. The container sidewall is about .015 inches
(0.038 cm) to about .025 inches (0.0635 cm) thick. The base may be thicker and require less
orientation. Also, the orientation in the tapered shoulder will vary from that in the cylindrical
sidewall due to differences in the geometry (e.g. amount of hoop stretch).
depicts the step 50 of inflating the lower portion 46 of the preform 44 using a mold
58. As illustrated in the preform 44 has a neck finish 18 including a top sealing portion
17 that has been strengthened through thermal crystallization. The preform 44 is placed inside a
blow mold cavity 56. Air is injected through the core rod 52 until the lower portion 46 of the
preform 44 takes the shape of the cavity, thereby creating the lower expanded portion 13 of
container 12. The neck finish 18 having the top sealing portion 17 remains substantially
unchanged during the process. Through this process, the polymer material is stretched from the
pull point 19 defined in the previous step of thermally crystallizing the neck finish 18, resulting
in strain hardening of the resin in the lower container portion. Therefore, biaxial strain
orientation begins from the bottom of the neck finish 18 at the pull point 19. Accordingly, the
lower container portion is strain oriented, while the neck finish 18 is thermally crystallized.
When the container 12 is cooled, the mold halves 58a and 58b are opened and the container is
ejected from the blow molding machine; it now comprises the container 12 seen in FIGS. 1 and
2, for example.
Although the above paragraphs describe thermally crystallizing the upper portion 45
before the container 12 is blown, the upper portion 45 can be thermally crystallized after the
container 12 is blown. However, it is preferred that the upper portion 45 is thermally crystallized
prior to the inflation of the container 12 in order to be able to provide the desired pull point 19
for orientation during blow molding.
In accordance with the present invention, the plastic containers must conform to a hot
water bath test for leak detection under 49 CFR § 173.306(a)(3)(v) (United States Code of
Federal Regulations, Chapter 1 (201006 edition), U.S. Department of Transportation Rules
and Regulations). The requirements of the hot water bath test under 49 CFR § 173.306(a)(3)(v)
are:
(v) Each container must be subjected to a test performed in a hot water bath; the
temperature of the bath and the duration of the test must be such that the internal
pressure reaches that which would be reached at 55°C (131°F) (50°C (122°F) if
the liquid phase does not exceed 95% of the capacity of the container at 50°C
(122°F)). If the contents are sensitive to heat, the temperature of the bath must be
set at between 20°C (68°F) and 30°C (86°F) but, in addition, one container in
2,000 must be tested at the higher temperature. No leakage or permanent
deformation of a container may occur.
illustrates the temperature and pressure conditions of a test according to one
embodiment. A 405ml PET aerosol container (0.022 inch (0.0559cm) sidewall thickness, planar
stretch ratio of 11, hoop stretch of 3.3 and axial stretch of 3.3) was filled 60% (of container
volume) with water and 40% nitrogen (as the propellant) pressurized to 130 psig (9.14 kgf/cm ),
and submerged in a hot water bath of 153°F (67.2°C) for 30 minutes. The dispenser 10 did not
leak at the closure and showed no signs of distortion. As indicated in the graph, the dispenser 10
is able to withstand the aforementioned temperature 60 and pressure 61 requirements for a
duration well beyond the time requirements established in the guidelines. In this test, the
container was sealed with a closure of the type illustrated in including the valve
assembly; the closure unit (metal cup, rubber-like gasket and valve assembly) are sold as a unit
by Summit Dispensing Systems, Inc., Manchester, NH, USA. After removal from the hot water
bath tank, the pressure was measured, having dropped to about 110-115 psig (7.74-8.09 kgf/cm )
due to expansion of the container. The container is then equilibriated and placed in a stability
chamber having a temperature of 50°C and 50% relative humidity. The container may continue
to be monitored for pressure for, e.g., 6 months to one year.
FIGS. 7A and 7B illustrate another embodiment of a container 12 and a closure 70. Here,
the neck finish 18 does not have a top sealing flange. Instead, the neck finish 18 has external
threads 11 and a nylon collar 90 having internal threads 91 is screwed onto the finish thread(s) to
attach the collar 90 to the neck finish 18. Optionally, the collar can also be glued to the neck
finish. A valve cup closure 70 is then placed on top of the collar; the valve cup includes a
rounded sealing rim 73, which is crimped (deformed) at outer wall 75A of trough 74 (as shown
in Fig. 7B) for attachment to a top portion 92 of the collar 90. Again, the valve assembly fits into
central aperture 78 of wall 77 and may be attached by crimping (deforming) the inner closure
wall 75B (as shown in Fig. 7B) to engage the valve stem assembly.
shows another embodiment of an upper crystallized portion 16 and partial
shoulder 14. In this embodiment, a transfer bead 100 is provided toward the lower end of the
neck finish 18. The transfer bead 100 is used to carry the preform 44 through the reheat blow
molding machine. Preferably, the pull point 19 is 2-4 mm below the transfer bead 100.
The term "plastic" will be understood herein to encompass a thermoplastic crystallizable
polymer. Although PET is used throughout the disclosure as an example, other polymers include
other polyesters such as polyethylene napthalate (PEN), polyamide (Nylon), and copolymers,
mixtures or blends thereof.
Blow molding techniques are well known in the art, and the plastic aerosol container can
be formed by any known blow molding technique. Plastic aerosol containers may be made by a
stretch blow molding process (also called orientation blow molding). For example, in a stretch
blow molding process, the plastic is first molded into a preform using the injection molding
process. Typically, preforms are packaged, and fed later (after cooling) into a reheat stretch blow
molding machine. A preform is produced with a neck which includes a finish of the container on
one end, which may have a transfer bead that is used to carry the preform through the heating
process. In the stretch blow molding process, the preforms are heated (typically using infrared
heaters) above their glass transition temperature Tg, then blown (using high pressure air) into
hollow containers in a metal blow mold. Usually, the preform is stretched with a core rod as part
of the process. The expansion of some polymers, for example, PET (polyethylene terephthalate)
results in strain hardening of the resin. This allows the containers to better resist deformation
when used to contain a pressurized product.
The crystallized finish allows the blow molder to more thoroughly heat the lower preform
area (especially right below the neck finish) prior to blow molding, because one need not avoid
all heating of the preform neck finish as would be required with an amorphous finish. An
amorphous finish will soften if heated and then distort in the blow molding process, which
produces one or more problems of: 1) nonuniform expansion of the lower preform portion in the
blow mold; 2) inability to eject the distorted finish from the blow mold and/or 3) inability to seal
with a closure (e.g. a threaded closure).
Thus, by allowing heating of the thermally crystallized neck finish area of the preform,
the present invention greatly enhances the ability of the lower preform body area to uniformly
expand because the crystalline region will not stretch and will provide a much sharper transition
at the pull point.
While it may be more convenient and beneficial in one embodiment to thermally
crystallize the entire finish, both throughout the finish thickness and throughout the finish height,
in other embodiments it may be sufficient to preferentially thermally crystallize only select
portions of the neck finish (in addition to the area of the neck finish immediately adjacent the
pull point which must be crystallized). Thus, in one embodiment the top sealing portion where
the closure is attached, and the lower neck finish (e.g. below the transfer bead) are crystallized,
while other portions of the neck finish are not.
Although several preferred embodiments of the invention have been specifically
illustrated and described herein, it is to be understood that variations may be made in the preform
and container construction, materials, and method of forming the same without departing from
the scope of the invention as defined by the appended claims.
Claims (15)
1. A plastic aerosol container comprising: a thermally crystallized neck finish having a crystallinity of at least 5% configured to receive an aerosol valve and closure assembly; an expanded strain oriented aerosol container body integral with the neck finish; the container body including a thermally uncrystallized shoulder and sidewall; a junction between the thermally crystallized neck finish and the strain oriented container body defining a pull point at which strain orientation begins; and wherein the plastic aerosol container can withstand a hot water bath test under 49 CFR § 173.306 (a)(3)(v) without leakage or permanent deformation when filled 60% (of container volume) with water and 40% nitrogen (as propellant) pressurized to 130psig.
2. The aerosol container set forth in claim 1, wherein the container comprises at least one of polyester and polyamide.
3. The aerosol container set forth in claim 1, wherein the container comprises polyethylene terephthalate (PET).
4. The aerosol container set forth in any one of claims 1 to 3 wherein the neck finish has a crystallinity of between 20% to 40%.
5. The aerosol container set forth in any one of claims 1 to 4, wherein the neck finish includes at least one of a flange and a thread.
6. The aerosol container set forth in any one of claims 1 to 5, further comprising an aerosol valve and closure assembly including a crimp configured to connect the valve and closure assembly to the neck finish.
7. The aerosol container set forth in any one of claims 1 to 5 further comprising an aerosol valve and closure assembly including a thread configured to connect the valve and closure assembly to the neck finish.
8. A method of making a plastic aerosol container from a preform of crystallizable polymer, the preform comprising: an upper preform portion and a lower preform portion; the upper preform portion including a neck finish configured to receive an aerosol valve; the lower preform portion including a tapered shoulder configured to be expanded by blow molding to form an expanded strain oriented shoulder of an aerosol container body; the lower preform portion further including a sidewall configured to be expanded by blow molding to form an expanded strain oriented sidewall of the aerosol container body; the method comprising steps of: creating a pull point at which strain orientation begins below the neck finish of the preform by thermally crystallizing the preform neck finish to a crystallinity of at least 5% while the lower preform portion including the tapered preform shoulder and sidewall remain thermally uncrystallized; and blow molding the lower portion of the preform from the pull point to form an expanded strain oriented container shoulder, formed from the thermally uncrystallized tapered preform shoulder, and an expanded strain oriented container sidewall, formed from the thermally uncrystallized preform sidewall; wherein the plastic aerosol container so formed can withstand a hot water bath test under 49 CFR § 173.306 (a)(3)(v) without leakage or permanent deformation when filled 60% (of container volume) with water and 40% nitrogen (as propellant) pressurized to 130psig.
9. The method set forth in claim 8, wherein the container comprises at least one of polyester and polyamide.
10. The method set forth in claim 8, wherein the container comprises polyethylene terephthalate (PET).
11. The method set forth in any one of claims 8 to 10 wherein the neck finish of the preform is thermally crystallized to a crystallinity of between 20% to 40%.
12. The method set forth in any one of claims 8 to 11 , wherein the neck finish includes at least one of a flange and a thread.
13. The method set forth in any one of claims 8 to 12, further comprising: crimping an aerosol valve and closure assembly onto the neck finish.
14. The method set forth in any one of claims 8 to 12, further comprising: threading an aerosol valve and closure assembly onto the neck finish.
15. A preform for blow molding a plastic aerosol container comprising: an upper preform portion and a lower preform portion, the upper preform portion being thermally crystallized and including a thermally crystallized neck finish having a crystallinity of at least 5% configured to receive an aerosol valve; the lower preform portion not being thermally crystallized and including a thermally uncrystallized tapered shoulder configured to be expanded by blow molding to form an expanded strain oriented shoulder of an aerosol container body; the lower portion further including a thermally uncrystallized sidewall configured to be
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201161513911P | 2011-08-01 | 2011-08-01 | |
US61/513,911 | 2011-08-01 | ||
PCT/US2012/048956 WO2013019784A1 (en) | 2011-08-01 | 2012-07-31 | Plastic aerosol container and method of manufacture |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ619876A NZ619876A (en) | 2015-06-26 |
NZ619876B2 true NZ619876B2 (en) | 2015-09-29 |
Family
ID=
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