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NECESSITY
OF OBTAINING CLOSURE SAMPLES AND INFORMATIONPRIOR TO A PLASTIC BOTTLE
PRODUCTION RUN
by
Stuart Feen, President, Plastic Bottle Corporation
Virtually
all manufactured parts have a plus or minus (+/-) range of dimensional
acceptability (tolerances), and plastic bottles and closures are
no different, except that their ranges may be greater than some
types of products and less than some other types. Because closures
and bottle necks represent a variety of manufacturing variabilities
and tolerances, even if they are within specifications, which can
affect mating possibilities of one to the other, we always need
to know what closures, sprayers or finger tip sprayers/pumps are
to be used on our bottles. When we receive the order, we ask for
the closure, sprayer, or finger tip sprayer/pump manufacturer’s
specifications and ask for samples of the closure, sprayer or pump
to be used on our bottle.
Definitions
and Discussion
- CT
means a regular screw cap with a continuous thread. This is the
most common type of cap or closure, having smooth or ribbed sides
(skirts) and a rough or smooth top. They come in virtually any
color and are commonly designated as 400, 410, and 415, as in,
24-415. This type of closure is usually lined with a paper, plastic,
foil, film or combination liner in order to provide the best sealing
of the product within the bottle for product integrity and to
avoid leakage in shipment. The Plastic Bottle Institute, a division
of The Society of the Plastics Industry, Inc., has published Dimensions
and Tolerances for Plastic Bottles for a number of years and these
dimensions and tolerances cover most of the 400, 410, and 415
standard necks plus some others. For a variety of reasons there
should never be an assumption of what is standard without all
parties of and suppliers to the transaction being aware of what
the other’s dimensions and tolerances are.
- CRC
means a Child Resistant Closure which may be of a single piece
or two piece design. If a two piece CRC, it usually has a CT inner
cap with the palm or push down and turn outer shell. There is
also a two piece pull up and turn CRC. CRCs usually have special
“H” requirements that are not standard 400 or 410, even
though they may be designated as 28-400 or 24-410 etc. The two
piece push down style especially requires careful attention to
the “H”, since even if the neck is too short the closure
can usually be applied to the neck. But when the end user tries
to push down to take the closure off of the bottle, the closure
bottoms out on the bottle shoulder and the outer shell cannot
properly engage the inner cap, leaving the consumer with a very
well sealed bottle that they cannot open. This is not a good situation.
- An
ORIFICE REDUCER is an injection molded piece that fits
into the neck of the bottle to reduce the size of the opening
from a river to a very small streamlet. Each neck I.D. (inside
diameter) must be carefully set and maintained for each type,
style, and size of orifice reducer to be used. Because of the
tremendous possible variety there is no such thing as a standard
I.D.
- A
LINED closure is one that has a paper, plastic, metal foil,
film or combination liner. Dispensing closures are sometimes lined
and other types of usually unlined closures are sometimes lined
for various reasons.
- A
LINERLESS non-dispensing closure is usually a closure that
has been designed to be used without a liner because it has some
sort of anti-leaking feature molded into the inside top of the
cap. A crabs claw is such a feature. LINERLESS closures were first
developed as a way to reduce the closure cost by not having the
dual expenses of the liner material and the application of the
liner. LINERLESS closures represent a greater possibility for
leaking than lined closures. Even though we are regularly measuring
the necks during manufacture, there may be certain anomalies that,
while they might be picked up with visual and physical inspection,
might show up faster and easier with actual checking the specific
closure on the specific bottle.
- An
UNLINED CT closure is sometimes one that was designed to
be used with a liner, but which, for whatever reason, does not
have a liner. This is a very risky situation, especially for leakage
of liquid products and is not, except for very special situations,
acceptable.
- DISPENSING
closures are those that via a pull/push, spout, twist, or flip
top allow products to be dispensed. Dispensing closures are usually
linerless closures with some sort of sealing mechanism such as:
crabs claw, valve seal, land seal or some combination of the seals,
but not always. The land is the surface at the top of the neck.
The land seal is riskiest from a leaking point of view and we
absolutely must have cap samples for testing with the bottle necks
when we run the bottles. Some dispensing closures have a “valve”,
which is a partial cone that fits into the neck of the bottle
and seals against the inside of the neck. Here, and with the valve/land
seal as well, we must have the closure manufacturers’ neck
I.D. specifications and tolerances and lots of samples for testing
while running. The valve seal/land seal combination is the least
risky, but there is still risk.
- TRIGGER
SPRAYERS, FINGER TIP SPRAYERS, ANTI-ROTATIONAL or RATCHET
CAP SPRAYERS OR DISPENSING CLOSURES represent special actual
and potential problems and need to be looked at individually with
reference to all applicable manufacturer’s specifications.
When
taking any order we first need to ask what closure is to be used
with the bottle. We need to know the closure size and manufacturer.
If the closure is a regular, non-dispensing 400, 410, or 415 size
with a non-induction seal or pressure sensitive liner, then we might
be o.k. without getting samples from the customer as long as we
get all of the dimensional specs. However, to be entirely safe we
should still ask for samples of these least problematic of closures
for testing.
For
any other closure, pump, or sprayer we need to have 200 samples
for testing bottles while we run,
and we also need to have the specified NECK FINISH print for that
closure. We should also have the closure print, but we absolutely
must have the print or printed numerical specifications for the
neck finish. We need to know, among other things the REQUIRED:
- “H”
- “S”
- “T”
- “E”
- “I”
- I.D.
lead-in radius
- Min
land thickness
- Any
other neck specs the closure manufacturer wishes to call out
If
the closure has an induction seal or pressure sensitive liner, then
we MUST be certain to obtain from the closure manufacturer the MINIMUM
LAND their closure requires for use with induction seal or pressure
sensitive liners. This will in turn define the I.D.
Lastly,
while talking about the neck, it is always nice to know the diameter
of the customer’s fill tubes. The buyer or purchasing agent
may not know this, so it is especially important to ask them if
they have checked the samples we sent to them on their filling lines
and especially with their fill tubes. An I.D. that is consistent
with all of the above requirements is then specified on orders for
that customer for that bottle with the particular closure.
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Technical
Article: The Necessity of Obtaining Closure Samples and Information
Prior to a Plastic Bottle Production Run
Child
Resistant Closure Specifications
Labeling
Material
Codes/Recycling Symbols
Freight
Classifications
Properties
of Resins
SPI
Neck Finish Specifications
Technical
Article: The Blow Molding
Process Closures & Containers Magazine
Technical
Article: The Market Share
Closures & Containers Magazine
Third
Party Packaging Certification Agencies
Trigger
Sprayer Specifications
Torque
Guidelines for Closures
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