Even though today’s world is dominated by digital media, inks still play a significant role in several applications. They are the basis for branding packaging, posters, promotional materials, and clothing. Especially in applications like packaging, there has been a rise in the number of differentiated brands over the past decade to meet the growing number of consumer demands and niches. With this increase in new brands, a considerable amount of ink technology and formulation innovation has become necessary to help brand owners stand out when promoting their products.
The foundation for any good printing ink formulation includes binders and additives that provide precise control over rheological properties, excellent durability, and unmatched visual clarity. ETHOCEL™ polymers are ideal components in many printing inks used in several printing methods, including flexographic, gravure, inkjet, screen printing, and hot-melt inks.
ETHOCEL™ for Ink Formulations
ETHOCEL™ is a line of naturally derived ethylcellulose polymers commonly used as binders and additives in printing ink formulations. They are manufactured by extracting cellulose from wood pulp or cotton linters, then reacting with ethyl chloride, yielding ethylcellulose polymers that are insoluble in water but highly soluble in organic solvents. ETHOCEL™ is highly pure with low fiber, NaCl, and moisture content. The figure below displays the cellulose backbone of ETHOCEL™ polymer and its ethoxyl group substitution.
ETHOCEL™ polymers are invaluable in solvent-based ink formulations because they are:
- Outstanding film formers
- Pseudoplastic rheology modifiers
- Broadly compatible with different formulation components and soluble in many solvents
- Highly pure and form solutions with great clarity
Outstanding Film Formation
ETHOCEL™ provides great functionality as both a binder and additive in forming durable and defect-free films on various surfaces. ETHOCEL™ binders form films with high tensile strength, abrasion resistance, excellent adhesion and gloss, and extreme flexibility even at low temperatures. Ink films made with ETHOCEL™ also have reduced tack and enable faster solvent release. These properties increase the efficiency of ink-printing processes and the inks’ longevity. ETHOCEL™ also functions as a pigment-wetting additive, making it useful for addition during the pigment-grinding phase of ink formulation to form films with great color and consistency.
Pseudoplastic Rheology Modification
One of the most important additive functionalities of ETHOCEL™ is its role as a thickener that can precisely control viscosity and apply pseudoplastic flow properties in solvent-based inks. ETHOCEL™ is available in grades with tight viscosity specifications, allowing formulators to adjust viscosity finely within a broad range. This is significant for printing processes, as inks with too high of viscosity may have too much tack and poor transference onto substrates, and inks with too low of viscosity may cause a loss in distinctness of image. The pseudoplastic rheology that ETHOCEL™ imparts is key to applying the appropriate coat weight and achieving the proper ink definition for processes such as lithographic and screen printing. The figure below details the shear-thinning apparent viscosity data for several ETHOCEL™ grades of varying molecular weights. This data is based on ETHOCEL™ grades added to terpineol at 3 wt%.
Shear-Thinning Rheology of ETHOCEL™
Excellent Clarity and Purity
As mentioned previously, ETHOCEL™ is highly pure and contains low fiber, moisture, and salt. The absence of insoluble fibers helps create films with fewer defects and a better visual appearance. The picture below compares an ink film formed with ETHOCEL™ versus a competitive ethylcellulose polymer with a similar viscosity specification. These films were examined through cross-polarized imaging; the white spots represent cellulose fiber impurities that form ink films with poor visual quality.
Ink with ETHOCEL™
Ink with Competitive Ethylcellulose
Solutions made with ETHOCEL™ have low haze and high transparency. This helps formulators create inks that accurately convey the intended visual qualities on various substrates. Below are pictures that compare the clarity of solutions made with ETHOCEL™ versus a competitive ethylcellulose polymer.
Solutions in DOWANOL™ DB, 5 wt%
Solutions in Texanol™, 15 wt%
Broad Compatibility and Solvent Solubility
ETHOCEL™ is highly compatible with a variety of other resins, pigments, plasticizers, waxes, and other materials that constitute printing ink formulations. ETHOCEL™ is also soluble in many solvents, such as aliphatic alcohols, ether alcohols, aromatic hydrocarbons, chlorinated aliphatic and aromatic hydrocarbons, and natural oils. This broad solubility range provides flexibility to formulators when using ETHOCEL™ within various ink formulations. In many cases, ETHOCEL™ is used in solvent blends to customize and achieve lower viscosities than those obtained using only a single solvent. For example, solutions of ETHOCEL™ in toluene can benefit from the addition of a small quantity of alcohol to achieve lower minimum viscosities. Using ETHOCEL™ in these mixtures can also result in stronger films.
ETHOCEL™ is available in grades listed below, which exhibit tight viscosity specifications based on a broad range of values.
|ETHOCEL™ Standard 4 Industrial||3.0–5.5|
|ETHOCEL™ Standard 7 Industrial||6.0–8.0|
|ETHOCEL™ Standard 10 Industrial||9.0–11.0|
|ETHOCEL™ Standard 20 Industrial||18.0–22.0|
|ETHOCEL™ Standard 45 Industrial||41.0–49.0|
|ETHOCEL™ Standard 100 Industrial||90.0–110.0|
|ETHOCEL™ Standard 200 Industrial||180.0–220.0|
*(5 wt% in 80/20 toluene/alcohol mixture at 25°C)
Presented below are several types of ink formulations that benefit from ETHOCEL™ as either a binder or an additive. For instance, the flexographic and screen printing ink formulations leverage ETHOCEL™ as a rheology modifier, and the gravure and hot-melt ink formulations use ETHOCEL™ as a film-forming binder.
|ETHOCEL™ Standard 10||7|
|ETHOCEL™ Standard 10||30|
|Screen Printing Ink|
|ETHOCEL™ Standard 4, 45, or 100||2|
|ETHOCEL™ Standard 10||16|
ETHOCEL™ is an indispensable component of many solvent-based ink formulations. It is an excellent ink binder that forms solvent-based ink films with exceptional durability, gloss, clarity, flexibility, adhesion, and minimized defects. ETHOCEL™ may also be used as an ink additive to provide pigment wetting in the grind phase and allow formulators to thicken and create pseudoplastic rheology in their preferred viscosity range during the let-down phase. ETHOCEL™ is highly compatible with a variety of ink components and soluble in many solvents, making it easy to work with in a vast number of formulations.
ChemPoint is here to help with your ink formulation requirements. Click below to ask us a question or request a sample of ETHOCEL™ for your application.