Specially modified polyvinyl alcohols (PVOH,PVA): Grades, features, and uses

PVOH are synthetic resins with various functions such as water solubility, solvent resistance, adhesion, film forming ability, surface active properties, gas barrier properties, and biodegradability. These functions can be adjusted by varying the degree of saponification (ratio of hydroxy to acetyl groups) and molecular weight (degree of polymerization) to provide products for a wide range of applications such as adhesives and binders, paper processing agents, emulsifiers and dispersants, and raw materials for films.

At the same time, there have been many demands from the market for even higher or new functions. To meet these demands, we have carried out extensive research into specially modified PVOH, in which modifying groups are introduced into the conventional polyvinyl alcohol structure.

The industrialization of manufacturing methods such as copolymerization with vinyl acetate monomer followed by saponification and the introduction of modifying groups via post reaction of polyvinyl alcohol provides specially modified PVOH for all kinds of applications.

Illustrative structure of specially modified PVOH polymers is shown here.

With a long history of research in this field, Mitsubishi Chemical has commercialized a variety of specially modified PVOH by utilizing our proprietary modification techniques. These specially modified materials have found use in new applications for which conventional PVOH are unsuitable.

Our specially modified PVOH and their features and usages are introduced below.

Nichigo G-Polymer™ adds melt processing capability to general PVOH features such as water solubility, gas barrier property, and biodegradability.

In particular, since it provides a higher oxygen barrier than conventional barrier materials at low humidities, Nichigo G-Polymer™ is increasingly being used as a barrier material for foodstuff barrier packaging and contributing to overcoming food loss.

Nichigo G-Polymer™ is also attracting attention as a barrier coating agent due to its parallel features of aqueous solution processability (solution stability, low viscosity, ability to use with alcohols, etc.) and high gas barrier properties.

We recommend Nichigo G-Polymer™ for customers who are looking for barrier materials that can be melt processed or coated as aqueous solutions.

More details about Nichigo G-Polymer™ can be found here.

The water solubility that is a feature of PVOH can also be a drawback for some applications.

For example, it may be necessary that a PVOH can be handled as an aqueous solution during processing but be insoluble (or difficult to dissolve) after drying and film formation.

The acetoacetyl groups in GOHSENX™ Z give high reactivity and are easily crosslinked, providing water resistant films as well as aqueous processing. These features are utilized for applications such as topcoat layers for thermal paper, emulsifiers for water resistant polyvinyl acetate emulsions, and water resistant adhesives.

We recommend GOHSENX™ Z for customers who are concerned about the reactivity and water resistance of PVOH.

More details about GOHSENX™ Z can be found here.

GOHSENX™ L is a PVOH that contains strongly anionic sulphonic acid groups (sodium sulfonate base). The electrical repulsion effect of the sulphonic acid groups deters particle reagglomeration and stabilizes dispersions of hydrophobic fine particles, making GOHSENX™ L useful as a dispersant for the dyes and developers used in the coloring layers of thermal paper.

GOHSENX™ L is also used as an emulsifier (polymer protective colloid) for the emulsion polymerization of acrylic emulsions.

We recommend GOHSENX™ L for customers who are concerned about the dispersiveness of PVOH.

More details about GOHSENX™ L can be found here.

GOHSENX™ K is a PVOH that contains cationic quaternary ammonium base groups.

It exhibits good adhesion to anionic materials such as natural fibers and pulp, and also has antibacterial properties.

As well as uses as an emulsifier and binder, GOHSENX™ K suppresses the swelling in water of layered inorganic materials such as clays, and is also used as an additive for drilling mud.

We recommend GOHSENX™ K for customers with an interest in cationic PVOH.

More details about GOHSENX™ K can be found here.

The polyethylene oxide groups in GOHSENX™ LW and GOHSENX™ WO plasticize the PVOH, so these products form extremely flexible water soluble films.

Since polyethylene oxide has an excellent affinity for water, its introduction enables the preparation of high concentration aqueous solutions even from originally water-insoluble, low-saponified PVOH. At Mitsubishi Chemical, we have successfully made high-concentration aqueous solutions of low-saponified polyethylene oxide modified PVOH and are using them as secondary dispersants for the suspension polymerization of polyvinyl chloride.

We recommend GOHSENX™ WO for customers with concerns about the flexibility of PVOH.

More details about GOHSENX™ WO can be found here.

We recommend GOHSENX™ LW for customers with an interest in low-saponified PVOH that can be handled as aqueous solutions.

More details about GOHSENX™ LW can be found here.

GOHSENX™ T is a PVOH that contains an anionic carboxy group (sodium carboxylate base).

Since it is water soluble and highly suitable for coating, GOHSENX™ T is widely used for applications such as paper coatings.

It can also be crosslinked with special crosslinking agents to increase the molecular weight and improve the water resistance.

We recommend GOHSENX™ T for customers who are searching for PVOH with excellent water solubility.

More details about GOHSENX™ T can be found here.

Since our founding in 1927, Mitsubishi Chemical has continued to apply research and engineering to develop numerous specialty products.

With a long history of research into PVOH, we have commercialized a variety of specially modified PVOH by utilizing our proprietary modification techniques.

Please contact Mitsubishi Chemical for inquiries about our specially modified PVOH.