Applications of polyethylenimine（PEI） in Film Coatings 9002-98-6

1.Preface EPOMIN (Polyethylenimine, PEI) is a highly polar, high-charge-density polyamine compound with a branched structure containing primary, secondary and tertiary amines. Owing to its structural characteristics, it is a water-soluble polymer with versatile reactivity.

In the past, synthetic resins and other materials were coated on plastic films to impart various functionalities. However, poor adhesion between the film and coating has been a common issue. EPOMIN can now be used as a primer to improve adhesion between plastic films and coatings.

2. General Physical Properties EPOMIN features the branched structure shown below

EPOMIN is divided into the SP series with molecular weights ranging from 300 to 10,000 and P-1050 with a molecular weight of 70,000. Among them, high-molecular-weight P-1050 is the most widely used grade.

Trade Name: EPOMIN P-1050
Appearance: Transparent viscous liquid
Molecular Weight: Approx. 70,000
Solid Content: 50% aqueous solution
Viscosity (mPa·s, 25°C): 10,000~20,000

3.Application Examples

3.1 Adhesion-promoting & Printable Films Background:

Untreated OPP, PET and other films exhibit poor adhesion due to their non-polar nature. Incorporation of polar polymers such as PEI enables in-line coating and lamination. Film Structure: EPOMIN P-1000 / OPP, PET

• Refer to Technical Document J-008-7 for blocking issues.

Performance: EPOMIN improves the bonding strength of polyethylene (extruded laminate). Mechanism: The active hydrogen groups in EPOMIN bond with polar groups generated by oxidation of molten PE as well as polar groups on the film surface, thereby enhancing bonding strength.

3.2 Heat-sealable Films Background:

Following the implementation of waste recycling regulations, heat-sealable films have attracted attention to reduce packaging film consumption for waste reduction, or to realize low-temperature heat sealing for higher productivity. Film Structure: Acrylic emulsion / EPOMIN P-1050 / OPP

Performance: EPOMIN increases the bonding strength between the acrylic resin layer and the film to achieve low-temperature heat sealing. Mechanism: Acrylic groups in the resin component react with amine groups ⇔ EPOMIN ⇔ Polar groups on the film surface combine with active hydrogen groups.

3.3 Gas Barrier Films Background:

Due to dioxin concerns, there is a trend toward halogen-free gas barrier coatings, and alternative polymers such as PVA and EVOH are promoted.

Film Structure: PVA / EPOMIN P-1000 / OPP

Performance: EPOMIN improves the adhesion strength between oxidized barrier layers such as polyvinyl alcohol and the film. It is especially effective for carboxylic acid-modified PVA. In addition, POLYMENT, a similar product, is recommended as a primer for PVDC.

Mechanism: Hydroxyl groups of PVA combine with active hydrogen ⇔ EPOMIN ⇔ Polar groups on the film surface combine with active hydrogen

3.4 Inkjet Films Background:

This type of film is coated with PVA or polyvinylpyrrolidone as an ink-receiving layer, yet it suffers from poor feathering resistance and water resistance.

Film Structure: PVA + EPOMIN P-1050 / PET, OPP

Performance: It rapidly immobilizes ink to prevent feathering and improves the water resistance of printed areas.

Mechanism: Cationic EPOMIN binds with anionic dyes to form polymer-dye complexes. Thanks to the high cationicity of EPOMIN, ionic reactions often occur with anionic dyes, anchoring the dyes within the ink-receiving layer.

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