| Frequently Asked
Questions |
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Basic
Knowledge |
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What is "Soarnol®"? |
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"Soarnol®"
is the trademark for ethylene-vinyl
alcohol copolymer (EVOH) resin
manufactured by Nippon Gohsei
(UK) Limited. Polyethylene, polypropylene,
nylon, polystyrene, polyester
and other materials can be combined
to form multilayer films, sheets,
bottles, tubes, pipes and so on.
Using "Soarnol®"
with these molded materials creates
a product with excellent gas barrier
properties, solvent barrier properties
and fragrance preservation properties,
suitable for use in a wide array
of packaging products that include
food packaging, medical packaging,
cosmetic packaging, and agrochemical
containers. |
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What are the properties of "Soarnol®"? |
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Gas barrier properties,
solvent resistance, oil resistance,
solvent barrier properties, high
transparency, weatherability,
fragrance preservation, printability,
high luster, environmental preservation
performance, and others. |
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What kind of method is used to manufacture
"Soarnol®"? |
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"Soarnol®"
is manufactured by polymerizing
vinyl acetate monomer and ethylene
monomer and hydrolyzing the resulting
poly-(ethylene-vinyl acetate). |
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What is the chemical structure of
"Soarnol®"? |
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"Soarnol®"
is a random copolymer of ethylene
and vinyl alcohol. |
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What is "Soarnol®"'s
shape? |
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"Soarnol®"
is manufactured in cylindrical
pellet form. |
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Does "Soarnol®" contain
any lubricants? |
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Yes, depending on
the grade. Customers may choose
grades that either include or
do not include lubricants. |
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What does "MFR" mean? |
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"MFR"
stands for "melt flow rate"
and indicates the quantity of
resin that flows out from a cylinder
during a ten-minute period at
a prescribed temperature and load.
A high MFR value indicates a low
melt viscosity. |
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What are the hygienic properties of
"Soarnol®"? |
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"Soarnol®"
complies with the Self-Restrictive
Requirements on Food-Contacting
Articles made of Polyolefins and
Certain Polymers, noted in Ministry
of Health and Welfare Announcement
No. 370. it also complies with
overseas hygienic regulations
such as FDA 21CFR, §177,§175
and EC Directive 90/128/EEC. For
more information, please contact
Nippon Gohsei. |
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Grade |
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How does one go about
selecting the proper grade of "Soarnol®" |
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You should select
the grade of "Soarnol"
by the required barrier properties
and the processing method to be
used. For example, grades with
a low ethylene content (for example,
29 mol%) offer better barrier
properties at normal humidity
than the grades with a high ethylene
content (for example, 44 mol%).
On the other hand, grades with
a high ethylene content have a
lower melting point than those
with a low ethylene content and
can generally be molded easily
even at low processing temperatures.
Other selection criteria include
the melt flow rate (MFR). You
should select the ideal MFR for
the molding conditions. |
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Does Nippon Gohsei (UK) Limited market
"Soarnol®" film? |
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Nippon Gohsei markets
"Soarnol" only in resin
pellet form. If you would like
to purchase "Soarnol"
film, please contact Nippon Gohsei. |
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Basic
Properties/Barrier Properties |
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How should "Soarnol®"
be handled? |
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Like nylon, "Soarnol®"
is a resin with high moisture
absorption. After use, be sure
to store the remaining resin in
a moisture-proof bag. If it has
absorbed moisture, dry it until
the moisture content is 0.3% or
less. Please see the separate
technical references for the proper
drying conditions. |
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How transparent is "Soarnol®"
film? |
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"Soarnol®"
film has extremely high transparency. |
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Do barrier properties of "Soarnol®"
depend on the humidity? |
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Barrier properties
decrease as the humidity increases.
Normally "Soarnol®"
is used in a multilayer configuration
with other resins with moisture-proof
properties. |
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How does one determine the thickness
of "Soarnol®" that one
needs? |
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You should determine
the required barrier properties
and mechanical properties from
the type of packaging system,
the shelf life and the allowable
oxygen concentration. Then determine
the thickness from the grade that
matches these conditions. |
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GTR Simulator
Lite (Link to Simulation
Page) |
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Are barrier properties of "Soarnol®"
dependent on thickness? |
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There is an inverse
relationship between thickness
and the quantity of transmitted
gas. As the thickness increases,
the barrier properties become
high as well. |
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Molding
and Film Processing |
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How is "Soarnol®"
molded? |
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Recommended screws
for "Soarnol" have LD=24-30
and CR=3-3.5. Temperature conditions
are generally 190-230deg C(374-446deg
F). In order to prevent thermal
decomposition, please make sure
the temperature does not exceed
250deg C(482deg F). For more information,
see the Processing
Technique page. |
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What is the recommended screw design? |
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You should avoid
using rapid compression type screws
such as those used for nylon.
There should be at least four
threads in the compression zone;
this number will vary slightly
depending on the L/D and compression
ratio. Trouble is particularly
likely to occur on high revolution
extruders equipped with rapid
compression type screws with 1
- 3 threads in the compression
zone. If the total number of threads
is 100, the standard number of
threads should be 30-40 for the
feed zone, 20-25 for the compression
zone and 35-50 for the metering
zone. |
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What kind of molding equipment is
needed? |
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To make co-extruded
molded products using "Soarnol",
normally at least two extruders
are needed: one for "Soarnol"
and one for the base material.
If necessary, an adhesive resin
extruder should also be used. |
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Is any special equipment needed for
"Soarnol®" molding? |
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No. However, to
prevent trouble during processing,
the screw design should be selected
so no molten resin is left and
no resin staying parts are formed.
In addition, the discharge capacity
should be chosen so no resin remains
in the extruder, and consideration
should be given to the plating
and other parts of the resin flow
path. |
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What kind of adhesive resins are appropriate
for "Soarnol®"? |
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Most resin manufacturers
market adhesive resins for use
with EVOH. For details, contact
these manufacturers or Nippon
Gohsei. |
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What is heat sealability of "Soarnol®"? |
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Since "Soarnol"
has a higher melting point than
other resins, it is normally not
used as a heat sealing layer. |
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Are barrier properties of "Soarnol®"
reduced by boiling or retort treatment? |
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It is possible to
prevent a decline in barrier properties
by adjusting the conditions. After
processing, sometimes the barrier
properties decline temporarily,
and this may result in whitening
or other poor appearance problems.
In such cases, we recommend that
you use a special grade of "Soarnol"
designed for retort use. |
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What is the procedure for purging
before disassembly and cleanup? |
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When processing
is complete, immediately replace
with LDPE of approximately MFR=1. |
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Troubleshooting |
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How can I prevent bubbling
of the "Soarnol®" layer? |
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Check the
following:
(1) If the "Soarnol®"
has absorbed moisture, dry it
in an air circulation type dryer
or hopper type dryer at 90-110deg
C.
(2) If the processing temperature
has risen to 240deg C or more
for some reason, reduce the temperature
of the cylinder and die.
(3) The screw design may be inappropriate.
(4) The processing conditions
may be inappropriate.
If the bubbling continues even
after you have checked these items,
contact Nippon Gohsei. |
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What are the tiny gels produced during
processing? |
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(1) Inadequate mixing
These are produced when the screw
is too short or when a large-sized
extruder is operated at low speed
and so on.
(2) Decomposed EVOH
Since EVOH is a heat-sensitive
resin, it may decompose or gel
when left at high molding temperature
for an extended period of time.
(3) Low molding temperature
This occurs on rare occasion when
the processing temperature is
low. |
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How can the size of the neck-in be
reduced? |
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EVOH tends to be
easier to form neck-ins than polyethylene.
Check the following:
(1) Make the air gap as narrow
as possible.
(2) Reduce the die temperature.
(3) Make sure there is a balance
between the extruder output and
the line speed. |
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