Polymeric Color and Antioxidant Technologies

Polymeric Color and Antioxidant Technologies Accelerating Growth in the PU Foam Industry The polyurethane (PU) industry has developed significantly over the past decade thanks to continuous innovation and demand for more sustainable, higher-quality materials. Manufacturers use raw materials produced around the world, starting with the main components of polyols and isocyanates to make a single mattress. Other additives used in PU formulations also play a critical role in enhancing the foaming reaction and providing the final quality and aesthetics required of the foam. We all want a comfortable mattress that provides good sleep. Continuous industry innovation, largely driven by advances in polyols and foam quality improvements, has established polyurethane as a material capable of meeting the most critical consumer requirements. PU foam has become a material preferred by millions of consumers because of its technical advantages. These developments have enabled the creation of multilayered viscoelastic, ultra-soft and highly elastic foams with superior quality, durability, breathability, comfort, thermal regulation and body support for mattress construction. Its growing success is linked to advanced foam quality and durability that makes mattresses more resistant, comfortable and breathable. While efforts continue to create a circular economy, companies in the value chain are working to make PU foam more sustainable. Additionally, certification programs such as Certipur or European REACH regulations help ensure the use of safer, healthier materials with reduced emissions. Improvements in processes and production over the past decade have provided both cost reductions and improvements in foam quality. These changes include greater transition to automation, digitalization in facilities and processes, and waste reduction. The growth of e-commerce has revolutionized the polyurethane sector with new mattress concepts such as "Bed in a Box." These mattresses delivered to the customer's door are the fastest-growing trend in the mattress industry and require the use of high-quality foams with superior shape recovery properties.   Color Technology It is well known that consumers choose what appeals to the eye, and color is an important sensory component in this decision-making process. The value provided by color is related to foam quality and the characteristics the foam manufacturer or brand owner wants to emphasize. Moreover, in a continuously evolving and renewing industry, the use of color is a perfect way to highlight the value of each layer in a mattress. Color can enable everyone in the value chain—from foam manufacturer to brand owner to end consumer—to fully understand the value and quality behind each foam layer. Mattress manufacturers have long used color to help differentiate their products. However, there are significant opportunities to take greater advantage of this feature to maximize how quality and branding are conveyed across the supply chain. Milliken's Reactint® colorants for polyurethane are at the forefront of this trend. Milliken invented Reactint polymeric colorants specifically for coloring polyurethane and other thermoset resins. These reactive polymeric liquid colorants consist of chromophores chemically bonded to polyols. This innovative colorant reacts in the polyurethane polymer matrix to create deep, vibrant foam shades. Unlike pigment pastes, which are dispersions of solid particles in a liquid carrier, Reactint colorants are 100% homogeneous liquids that dissolve in polyol and do not settle over time, preserving final quality (see Figures 1 and 2). To help manufacturers leverage the value of color, Milliken announced its ColorDirection 2022 trend report, Emerging Confidence, for PU mattresses featuring prominent trend colors. Additionally, to help you create the perfect color combination, Milliken launched a new, digital Reactint Color Studio that allows customers to find a Reactint formulation for any Pantone number or any shade in a photograph using the color wheel. This is a special feature that allows you to create your own mattress. The primary colorant principle is one of the benefits of Reactint colorants. This means you can produce PU foam in any shade using only five primary colorants through simple in-line mixing before the mixing head. Additionally, the colorant's low viscosity and high efficiency allow you to achieve rich tones without affecting the formulation or foam quality. [caption id="attachment_141412" align="aligncenter"] Figure 1: Reactint's polymeric structure helps maintain color quality and stability for the long term.[/caption]

Antioxidant and Scavenging Technology Background

Milliken's Chemical Division has focused over the past several years on developing additives that can meet both OEMs' stricter automotive requirements for emissions and consumers' improved product quality perceptions. Milliken designed Milliguard® AOX-1 to reduce decomposition byproducts by stabilizing carbon-centered radicals generated by the exothermic nature of the flexible PU foam production process without causing VOC, FOG and/or odor. Additionally, Milliken recently developed Milliguard AS 270 as an aldehyde scavenger aimed at reducing acetaldehydes and formaldehydes generated during the foaming process, a permanent strict requirement for the automotive industry.

Technology Overview

Polyurethanes are particularly susceptible to radical attack. During the curing process, which results from thermal decomposition and oxidation during the exothermic foam manufacturing process, there is a tendency for aldehydes and related other compounds to form (See Figure 2). The problem is further complicated by the fact that PU foam is an excellent insulator and retains heat within the module or part for a relatively long time. This same heat generation can also degrade auxiliary additives such as catalysts and surfactants used to make and stabilize the foam. [caption id="attachment_141413" align="aligncenter"] Figure 2: Auto-oxidation cycle[/caption] Milliken's first initiative in the stabilizer market involved the development of a unique, polymer-bonded benzofuran technology. Milliguard AOX-1 addresses the initial stage of the oxidation cycle by stabilizing carbon-centered radicals before they react with oxygen and further continue the decomposition process. Conventional antioxidants provide minimal protection at this point and only become effective once oxygen-centered radicals are well-established in the oxidation cycle. Milliguard AOX-1 protects the polymer backbone (main chain) from constant attack by various radical species, enabling reduced aldehyde production and emissions from degraded catalysts and surfactants. Milliguard AOX-1 enables the use of amine-free antioxidant packages in polyol stabilization, which helps reduce yellowing of PU foam after exposure to ultraviolet light or nitrogen oxide fumes. Its completely reactive nature also allows the foam to meet VDA-278 requirements in terms of VOCs and FOG (See Figure 3). [caption id="attachment_141414" align="aligncenter"] Figure 3: Milliguard AOX-1 antioxidant provides reduced VOC emissions[/caption] Milliguard AS-270 is a water-based polymer designed to scavenge aldehyde substrates with high efficiency. It is compatible with a wide variety of PU applications in both flexible and molded foams for automotive seating.

Conclusion

Therefore, it is no coincidence that polyurethane foam's continued popularity in the market for products such as mattresses stems from the chemistry and technologies behind its production continuing to evolve and improve; advanced polymeric colorant and additive technologies developed by Milliken's Chemical Division play a significant role in this. Both Reactint liquid polymer colorants that provide high-quality, long-lasting stable colors to PU foam and Milliguard AOX-1 antioxidant and scavenging technologies that help reduce decomposition, VOC emissions and aldehydes serve to improve the overall aesthetics and performance of polyurethane foam.       Herbert De Breuck Global Polyurethane Technical Leader Milliken