Historically, raw materials are the largest component cost for adhesives. This makes them particularly vulnerable to the negative effects of rising crude prices, which also negatively impact the disposable hygiene industry. Fortunately, recent innovations in polyolefin technologies are not only helping to reduce pricing volatility, they also offer a more stable supply while overcoming processing and performance challenges for hygiene adhesives.

Polyolefins Defined

A simple definition of Polyolefins is a polymer obtained from "olefins" as monomers. Olefins are typically ethylene, propylene, butylene, etc. Polyethylene is the number one product of the petrochemical industry. As a consequence, beyond production of gasoline, petrochemical plants are geared toward producing ethylene, in terms of process settings and choice of feedstock.

Petrochemistry starts with the process of “cracking” a feedstock to produce base chemicals and fuel, or fractions. Depending on the feedstock that is used in the refinery, it can lead to a quite different pool of molecules. The feedstock can either be crude oil or light gas. The cracking process of crude oil typically provides what the plants are designed to make, ethylene and propylene, as a major fraction. But this heavy feedstock also provides a smaller but valuable fraction of heavier olefins and aromatic compounds. These are typically used in the production of synthetic rubber and tackifying resins. If the feedstock becomes natural gas rather than crude oil, the cracking process leads essentially to ethylene.

Formulated with polymers based on ethylene as the core, an adhesive can capitalize on the fact that this raw material can be derived from both natural gas and crude oil processing. So no matter what material is being cracked, there will be raw materials for polyolefins remaining, increasing the stability of supply.

Technology & Formulation

Along with polymer technology, formulation expertise is essential. Although olefin-based adhesives are not a new concept, they previously were considered to lack the balance of process and performance for hygiene adhesive applications where high line speed and non-contact, spray applications are the rule. Even if with time, we’ve seen an increase in polyolefin offerings, with more on-purpose grades proposed for adhesive formulation, these adhesives still had limitations in terms of performance, aging, durability and process friendliness.
Today, polymer catalyst technology and polymer architecture have made much progress, enabling adhesive formulators to propose products more tailored to the disposable hygiene industry’s needs. But formulation is key in this task.

The combination of product development work, recent polyolefin technologies and formulation expertise has enabled the creation of new adhesives specifically designed for construction (or chassis) applications in baby and adult disposable hygiene products. These adhesives have the ability to eliminate or reduce previous challenges posed by older polyolefin technologies. Manufacturers of disposable hygiene products no longer have to compromise when it comes to performance or processability. Advanced and expert formulated olefin-based hygiene adhesives have the following qualities:

• Provides similar or better performance than the most widely used technology, Styrene Block Copolymers (SBC), and offers a wide range of peel strength and shear resistance capabilities
• Offers exceptional processability, making it compatible with all spray and slot application systems
• Can be applied with most hot melt application equipment with the same or better pattern quality as an SBC-based adhesive, resulting in improved edge control, minimized line contamination, consistent application and stable performance
• Is easily converted because it requires only a standard tank flush and purge
• Delivers unmatched flexibility because it bonds with a wide variety of films and nonwovens
• Is derived from an expanding feed stock of either crude oil or natural gas, providing a more stable supply and less price volatility

Christophe Morel-Fourrier is the global technical marketing manager in the Global Nonwovens Division of Bostik. He has worked in the adhesive industry for more than 20 years, both in France and in the UK. In his current role, he works with Bostik’s global product development team in the development of innovative technologies for the global hygiene market. He can be reached at christophe.morel@bostik.com