Eastman Solus™ for Nitrocellulose-Free Ink Formulations

Nitrocellulose has long been used as a binder or additive in solvent-based packaging inks because it can support fast drying, film formation, pigment wetting, and compatibility with common flexographic and gravure ink systems. However, formulators are increasingly evaluating nitrocellulose alternatives due to supply volatility, handling complexity, limited recyclability, and regulatory scrutiny in packaging applications. 

Eastman Solus™ performance additives provide cellulose ester-based alternatives to nitrocellulose-free ink formulations for packaging applications. For formulators working in ester- or alcohol-rich solvent systems, Solus™ grades can serve as the primary film-forming binder or as part of a modified acrylic or polyurethane ink system, helping maintain practical ink properties such as adhesion, viscosity control, color quality, solvent release, and lamination performance. 

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Replacing Nitrocellulose with Eastman Solus™  

Solus™ is a cellulose ester-based performance additive that forms clear films and dissolves in solvent blends used in solvent-based ink systems. They give ink formulators a non-nitrocellulose resin platform that can be modified with acrylic resins or solvent-based polyurethane systems, depending on the target substrate, print method, viscosity window, and end-use requirements. 

Below are starting formulations using Solus™ in ester-rich acrylic and polyurethane systems. For these systems, Solus™ 1100 and Solus™ 1250 are the primary grades to evaluate. 

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Ester-Rich Ink Starting Formulations with Eastman Solus™  

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Alcohol-Rich Ink Starting Formulations with Eastman Solus™ 

For alcohol-rich systems, the grade set expands to include Solus™ 1150, 1175, 1200, 1225, 1250, and 1425, with viscosity differences that allow formulators to select a grade based on solids, solvent package, application method, and press viscosity requirements.
 

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Key Performance Benefits

Improved Adhesion versus Nitrocellulose 

The ester-rich ink formulation above, using Solus™ 1100, demonstrated strong adhesion to common packaging substrates, including BOPP, LDPE, PET, aluminum foil, and tin. Adhesion was evaluated using ASTM D3359 tape testing, and the results show that Solus™ systems can meet a critical formulation requirement for packaging inks: maintaining ink integrity through printing, converting, handling, and downstream packaging use.
 

In another data set, alcohol-rich systems were produced using Solus™ and evaluated against Nitrocellulose for adhesion data on polypropylene films via ASTM D3359. The results indicate that all Solus™ samples exhibited better adhesion than nitrocellulose.

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Better Color Performance

Color performance is another important selection driver. The Solus™ 1100 system showed improved optical density versus a nitrocellulose + polyurethane formulation, indicating that Solus™ can support effective pigment wetting and dispersion. For ink makers, this matters because color density, pigment efficiency, and consistency across cyan, magenta, yellow, and black inks influence both formulation economics and print quality.
 

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More Consistent Viscosity Control

Viscosity control is also central to the value proposition. Both ester-rich and alcohol-rich Solus™-based inks showed consistent CMYK viscosity behavior and more stable viscosity over time in elevated-temperature testing compared with nitrocellulose-based systems. Below, the first graph shows the results for ester-rich inks formulated with NC versus Solus™, and the second shows the results for alcohol-rich inks formulated with NC versus Solus™. Stable viscosity can reduce dilution variation between colors, help maintain color density on press, and support more predictable runnability during production.
 

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Higher Bond Strength for Laminations 

For laminated packaging, Solus™ 1100 also showed strong green and cured lamination bond strength using ADCOTE™ 548 adhesive on BOPP. This is relevant to flexible packaging structures in which ink layers must withstand adhesive lamination, conversion, and package handling without delamination, ink lift, or loss of visual quality.
 

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Greater Recyclability

Recycling performance is also a growing concern for formulators seeking nitrocellulose alternatives, given the risks of discoloration and nitrosamine formation. In extrusion testing with recycled PE film, Solus™ 1100 retained its original color and did not form nitrosamines, as evidenced by data showing no discoloration associated with nitrocellulose-containing systems. For converters and brand owners evaluating polyolefin packaging, this makes NC-free ink design a practical part of recyclability-focused formulation work.
 

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Product Grades, Systems, and Selection Guidance

Grade selection should start with the solvent package and the target viscosity range. For ester-rich solvent-based inks, Eastman’s model formulations focus on Solus™ 1100 and Solus™ 1250 in ethanol/ethyl acetate systems. Solus™ 1100 is positioned as a lower-viscosity option, while Solus™ 1250 is positioned for higher-viscosity requirements. Both can be used in acrylic-modified or polyurethane-modified ink formulations.
For alcohol-rich inks, multiple Solus™ grades can be used to tune viscosity and handling. In a 25% resin, 55% ethyl alcohol, and 20% ethyl acetate varnish system, the reported viscosity range increases from Solus™ 1150 at the low end to Solus™ 1250 at the high end, giving formulators a practical way to choose a grade based on the viscosity profile required for a specific flexographic or gravure process.
 

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Summary

Eastman Solus™ performance additives are nitrocellulose alternatives for packaging inks, especially for formulators working in ester- and alcohol-rich systems. Available formulation and testing data show relevant performance in adhesion, pigment dispersion, viscosity stability, lamination bond strength, OPV compatibility, and recycling-related color retention. For flexible packaging inks, label inks, and packaging inks where nitrocellulose raises sourcing, handling, regulatory, or recyclability concerns, Solus™ grades provide technical teams with a structured path to evaluate NC-free ink formulations without abandoning familiar acrylic- or polyurethane-modified ink design approaches. Click below to discuss your ink formulation with one of our technical experts alongside Eastman to help you reformulate.