In the realm of adhesive tape solutions, two prominent contenders vie for supremacy: hot melt tape and solvent tape. While both options offer secure bonding, hot melt tape presents a compelling value and sustainability proposition, delivering a winning combination of cost efficiency, process improvement, and improved carbon footprint. In this blog post, we will delve into the advantages of hot melt tape over solvent tape, highlighting its ability to streamline operations, enhance productivity, and help achieve sustainability targets.
Understanding Hot Melt Tape
In all tape coating methods a thin, ‘liquid’ layer of adhesive is ‘spread’ onto a carrier or backing via a range of coating techniques.
Aqueous adhesives are a form where the polymer is dispersed in water, and use various dispersing agents, surfactants, defoamers, etc. to achieve good coatings. As the name suggests, solvent based systems are dissolved in solvents of various types. In both these cases, the ‘wet’ adhesive is coated on to the carrier, and then must be passed through an oven to evaporate off the water or solvent, and in certain cases, thermally cure the adhesive in the latter zones of the oven.
For hot melts, there are no solvents or water used, and the adhesive is supplied in 100% solids form. In order to apply it, the adhesive is warmed up until its viscosity reduces to the point where it can be coated – i.e. it is ‘melted’ until it is flowy enough. Hence the name hot-melt! As well as eliminating the use of a solvent, hot melt adhesive coating uses less energy (no more ovens or thermal oxidizers), takes up a smaller footprint, and allows for efficient coating of higher coating thicknesses (higher coat weights) and temperature sensitive materials.
History of Hot Melt
Hot melt tape has historically been used in packaging, sealing, carton sealing, and many other general purpose industrial applications. It offers several advantages over other types of adhesive tapes, including quick bonding (high tack), bond strength, and excellent adhesion to a wide range of materials, including cardboard, plastic, and metal. It is also known to have good low surface energy (LSE) bonding capabilities.
While they have high tack and bond performance, as well as being efficient and green, historically hot melts have a couple of significant limitations. Because they are ‘thermoplastic’ (soften as they are warmed up), hot melt adhesives can soften and fail in high temperature applications. Similarly, because they are not cross-linked (cured) they typically have limited internal strength and have inferior shear and cleavage strength. These factors meant that hotmelt adhesives were used only in specific applications, and their usage was far outstripped by solvent and water based which can be tailored to meet many more applications.
Learn More About UV Hot Melt
Evolution of Hot Melt – UV Cure
Because of the environmental and efficiency advantages of hot melts, there has been a drive in recent years to expand their performance and use. This has been precipitated by the development of UV curable hot melt acrylic adhesives.
Acrylic polymers are widely used in solvent and aqueous PSAs, and are highly formulateable for a wide variety of tape applications. UV curing is a commonly used technique for introducing cross-linking into a wide variety of coatings and polymers.
The combination of acrylic polymers with UV crosslinking functionality is revolutionizing the tape industry. UV light from special bulbs is used to ‘stimulate’ a cure reaction in the adhesive, leading to higher performance final coatings. The lamps can be mounted on typical design coating machines to provide an efficient, ‘green,’ highly controlled curing method for specially formulated hot melt acrylic systems.
Advantages of Hot Melt Tape Over Solvent Tape
Reduced Carbon Footprint:
There are many sustainability benefits to hot melt tapes, including:
- Lower solvent use / emissions
- More efficient / lower energy in coating (no drying/curing ovens or thermal oxidizers)
- Reduced carbon emissions during transportation – shipping 100% solids, no ‘extra’ solvent
- Smaller footprint / less materials to build coating line (no extended ovens)
- Waste is 100% solids – no solvents or other hazardous waste
Thicker Applications:
Because there are no solvents to drive off in the oven, thicker coatings can be achieved – up to 10mil+ (depending on the adhesive / curing profile)
Reduced / No VOCs:
Since the adhesive has no solvent, it is inherently cleaner and better suited to VOC sensitive applications such as medical, electronics, etc. – no volatile content
Adhesion Versatility:
Hot melt tape provides strong adhesion to a wide range of materials, which means it can be used for various applications, reducing the need for multiple tape types and lowering overall tape-related expenses.
Coating of Temperature Sensitive Materials:
Despite being a ‘hot process,’ some materials which cannot be processed through a typical coating oven can be coated using hot melt adhesive if properly handled and applied.
Fewer Health and Safety Concerns:
Solvent-based adhesives can contain volatile organic compounds that can be harmful to health and may require additional safety precautions during application and storage. Hot melt tape, on the other hand, is generally considered safer to use.
New UV Hot Melt Coater!
A 100% solids, heated slot die hot melt coating line has now been installed in our facility to coat hot melt (solventless) acrylic and rubber adhesives.
The coater includes dual dispensing equipment to process either rubber or acrylic adhesives without risk of cross-contamination. Acrylic adhesives will be crosslinked through UV curing lamps, allowing for thicker coatings as well as the ability to coat temperature-sensitive substrates that wouldn’t be suited for thermal curing. The adhesive thickness will be controlled through a closed-loop system between an infrared gauge traversing cross-web and a set of pumps regulating flow to the slot die coating head. The slot die is also well suited to zone coat with dry lanes in the machine direction, using a custom-machined shim.
In addition to traditional film, tissue, and fabric substrates, the machine has been designed to handle PE foams as well, with the intention of complementing Coater #1’s foam tape product range. The Hot Melt coater will be equipped with specialized corona treatment, a large-diameter turret rewind, and an accumulation system to facilitate roll changes.
Conclusion
Tape made with high performance hot melt adhesives stands tall as an environmentally friendly and process-improving adhesive solution in comparison to solvent tape. With its ability to optimize operations, increase productivity, and lower carbon footprint in multiple ways, hot melt tape offers businesses the perfect combination of benefits to maximize efficiency and cost while bringing enhanced sustainability.
By adopting hot melt tape, companies can gain a competitive edge in their manufacturing processes, enhance customer satisfaction, and achieve long-term success in an increasingly demanding marketplace. We look forward to taking on new business. Have a hot melt coater question or application? Contact us today! (413) 527-7120 or info@adhesiveapps.com