Three Ways to Prepare Cotton and Viscose Fabrics for Brighter, Sharper and more Cost-effective Inkjet Printing
Demand for printed textiles continues to rise globally, with leading brands embracing the design flexibility and low environmental impact that digital inkjet printing offers.
At the same time, mills worldwide are expanding their capabilities by taking advantage of advances in printing technology and techniques and the availability of high-quality ink formulations that not only deliver outstanding results, but also ensure print reliability and reproducibility. For popular cotton and viscose fabrics, reactive inks deliver the best results and highest wash-fastness.
Even though more mills are embracing digital printing workflows, many still underestimate the value of fabric preparation. As is the case for traditional dyeing and screen printing, fabric must be clean and free of impurities like oil, wax and any sizing agents used during weaving. But digital printing also requires additional steps to achieve the best end result.
A good start is half the battle
Proper fabric preparation can maximize the intensity and brilliance of the printed colors and control how the ink spreads on the fabric, optimizing printing definition and delivering a better-looking end product to delight brands and consumers. What’s more, selecting the right preparation recipe also makes it possible to decrease ink consumption while maintaining high color strength, resulting in substantial cost savings.
As a company with decades of technical expertise and application knowhow dating back to the very earliest days of the digital textile printing revolution, Huntsman Textile Effects recommends mills take the following three steps to improve fabric preparation for higher-value output at reduced cost:
1. Choose the right thickener/anti-migrant
Thickeners, like the LYOPRINT® product range, are widely used in screen printing, but can be applied in inkjet preparation recipes, too, to enhance color strength. Anti- -migrant, like PREPAJET®, lets you control ink penetration to optimize wicking and drop absorption, maximizing color strength and definition.
The choice of which polymer to use is largely driven by price and the mill’s familiarity with the technology, but end-article performance and total cost of ownership (TCO) should also be taken into account.
Natural thickeners tend to improve color yield, but their use may limit image quality in terms of definition and brilliancy. They are also more susceptible to fermentation during storage or when applied on a fabric. On the other hand, synthetic polymers—whether thickeners or anti-migrants—are more versatile, improving definition and brilliancy. Depending on the type of polymer, they may also make it possible to control ink penetration and consequently color yield.
Moving on to TCO, the right thickener/anti-migrant can help mills maximize productivity and safeguard their bottom line. It is important to calculate the cost of the entire process, including ink consumption.
Here is an example illustrating the costs associated with two anti-migrants (A and B). Anti-migrant A is used at a lower concentration than B (and costs less) but requires more ink to deliver the same color strength on the fabric. Anti-migrant B costs more due to its higher concentration, but requires significantly less ink.
The substantial ink savings with anti-migrant B lead to considerable significant cost savings, even when we factor in the higher purchase cost of anti-migrant B. Additionally, the more-concentrated anti-migrant B delivers greater color yield, making it a better choice all round.
2. Choose the right alkali
Sodium carbonate (soda ash) and sodium bicarbonate are both used extensively in inkjet printing to increase alkalinity for better reactive dye fixation. It is common knowledge that soda ash provides faster dye fixation, resulting in higher color yield, while sodium bicarbonate is ideal when a milder alkalinity is demanded by the chemistry of the ink.
In any case, it is useful to consider both the fabric and ink choice to evaluate whether soda ash can be included in the alkaline pretreatment recipe. Even a small percentage of soda ash in the mix with sodium bicarbonate can increase color yield and save ink cost without making the recipe unsafe for delicate fabrics.
However, it is important to note that some applications require unadulterated sodium bicarbonate, such as when printing with inks based on black vinyl sulfone dyes to achieve intense deep black shades.
3. Add a de-aerating agent
Although largely underestimated, a de-aerating agent introduced into the preparation recipe can dramatically reduce the potential for foam formation during padding, particularly at high speed.
By definition, foam decreases wet pick-up—the amount of preparation chemicals picked up by the fabric—in the area where it sits, thus resulting in patchy, non-homogeneous fabric preparation. Adding a proper de-aerating agent keeps air out the recipe to prevent foam from forming.
Some de-aerating agents, such as LYOPRINT ®AP, function as penetrating agents to also increase ink penetration on fabric during printing.
Taking these three steps, mills can improve their inkjet preparation and achieve better outcomes in terms of image definition, color gamut and color vibrancy and levelness, as well as cost savings that help make them more economically viable.
Mattia Perri, Global Application Specialist Inkjet, Huntsman Textile Effects