> Frequently Asked Question
- What is "Soarnol™"
- "Soarnol™" is the trademark for ethylene-vinyl alcohol copolymer (EVOH) resin manufactured by The Nippon Synthetic Chemical Industry Co., Ltd. (Nippon Gohsei). 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.
- What are the properties of "Soarnol™"?
- Gas barrier properties, solvent resistance, oil resistance, solvent barrier properties, high transparency, weatherability, fragrance preservation, printability, high luster, environmental preservation performance, and others.
- What kind of method is used to manufacture "Soarnol™"?
- "Soarnol™" is manufactured by polymerizing vinyl acetate monomer and ethylene monomer and hydrolyzing the resulting poly-(ethylene-vinyl acetate).
- What is the chemical structure of "Soarnol™"?
- "Soarnol™" is a random copolymer of ethylene and vinyl alcohol.
- What is "Soarnol™"s shape?
- "Soarnol™" is manufactured in cylindrical pellet form.
- Does "Soarnol™" contain any lubricants?
- Yes, depending on the grade. Customers may choose grades that either include or do not include lubricants.
- What does "MFR" mean?
- "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.
- What is the regulatory status of "Soarnol™"?
- "Soarnol™" complies with the food law regulations of various countries.
Hygienic properties of "Soarnol™"
For more information, please contact us.
- How does one go about selecting the proper grade of "Soarnol™"?
- 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.
- Does Nippon Gohsei market "Soarnol™" film?
- Nippon Gohsei markets "Soarnol™" only in resin pellet form. If you would like to purchase "Soarnol™" film, please contact Nippon Gohsei.
Basic Properties/Barrier Properties
- How should "Soarnol™" be handled?
- "Soarnol™" is hydrophilic and will absorb moisture if unprotected. High moisture uptake will not degrade the polymer but can cause voids during processing. After use, be sure to protect remaining "Soarnol™" from moisture uptake by sealing it in its original (moisture proof) container. 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.
Drying conditions and water absorption
- How transparent is "Soarnol™" film?
- "Soarnol™" film has extremely high transparency.
- Do barrier properties of "Soarnol™" depend on the humidity?
- Barrier properties decrease as the humidity increases. Normally "Soarnol™" is used in a multilayer configuration with other resins with moisture barrier properties.
Relative humidity and oxygen permeability
- How does one determine the thickness of "Soarnol™" that one needs?
- Many factors come into play when determining thickness required, such as shelf life, "Soarnol™" grade type, storage conditions, etc. Please contact us for assistance in making this determination. We can provide calculations using Nippon Gohsei's proprietary simulation program, GTR2000.
GTR Simulator Lite
- Are barrier properties of "Soarnol™" dependent on thickness?
- There is an inverse relationship between thickness and the quantity of transmitted gas. As the thickness increases, the barrier properties become high as well.
Molding and Film Processing
- How is "Soarnol™" processed?
- 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.
General advice on molding
- What is the recommended screw design?
- You should avoid using rapid compression type screws such as those used for nylon. There should be at least four turns 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 turns in the compression zone. The recommended percentage of turns in each zone should be as follows: 30-40 % in the feed zone, 20-25 % in the compression zone and 35-50 % in the metering zone.
General advice on molding
- What kind of molding equipment is needed?
- 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.
- Is any special equipment needed for "Soarnol™" molding?
- 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.
- What kind of adhesive resins are appropriate for "Soarnol™"?
- Most resin manufacturers market adhesive resins for use with EVOH. For details, contact these manufacturers or Nippon Gohsei.
- What is heat sealability of "Soarnol™"?
- Since "Soarnol™" has a higher melting point than other resins, it is normally not used as a heat sealing layer.
- Are barrier properties of "Soarnol™" reduced by boiling or retort treatment?
- 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.
- What is the procedure for purging before disassembly and cleanup?
- When processing is complete, immediately replace with LDPE of approximately MFR=1.
Precautions for Molding
- How can I prevent bubbling of the "Soarnol™" layer?
- Check the following:
- If the "Soarnol™" has absorbed moisture, dry it in an air circulation type dryer or hopper type dryer at 90-110deg C.
- If the processing temperature has risen to 240deg C or more for some reason, reduce the temperature of the cylinder and die.
- The screw design may be inappropriate.
- The processing conditions may be inappropriate.
If the bubbling continues even after you have checked these items, contact Nippon Gohsei.
- What are the tiny gels produced during processing?
- 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.
- 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.
- Low molding temperature
This occurs on rare occasion when the processing temperature is low.
- How can the size of the neck-in be reduced?
- EVOH tends to be easier to form neck-ins than polyethylene. Check the following:
- Make the air gap as narrow as possible.
- Reduce the die temperature.
- Make sure there is a balance between the extruder output and the line speed.