Momentive Tospearl™ silicone beads are spherical and uniform polymer additives for various polyolefin film applications. Micro-fine methyl silsesquioxane silicone resin was developed to assist converters, compounders, and masterbatch manufacturers.
Blocking occurs in polyolefin films during the stretch film process creating adhesion between layers of plastic film. To prevent this common problem during the extrusion process, the introduction of antiblocking and slip additives. Antiblock additives like Tospearl™ are the most effective in minimizing film-to-film surface contact. As an additive, Momentive’s silicone resin creates microscopic protrusions on the film surface, allowing for an increase in distance between the two film layers. The silicone helps improve film clarity while requiring lower usage levels than other antiblock additives like silica, talc, or mica.
During the polyolefin film extrusion process, a coefficient of friction (COF) occurs between those layers or between the film’s surface and the extrusion equipment. COF and increase in friction create processing difficulties, delays, increased extrusion rate, and operational costs for the polymer manufacturer. Tospearl™ plastic film additives decrease the contact between film layers during the extrusion process by lowering the coefficient of friction (COF) and thus preventing them from sticking together. Plastics in film packaging need stable and lower COF surfaces, and Tospearl™ allows for such requirements due to its spherical narrow particle size distribution.
The slip properties are illustrated below, which show Tospearl™ 120 FL, 130 FL, 1100 FL, and 145 FL’s low surface energies, uniform sizes, and spherical shapes, which impart lubricity to plastic films.
With Tospearl™, there is no need to worry about heat sealing issues like traditional migratory plastic additives. Below are features that make Tospearl™ a great choice in BOPP films.
- Low uniform COF resulting in higher quality & less downtime at converter
- Tight particle size distribution leading to faster extrusion rates and low dosage level
- Thermally stable up to 400°C causing no yellowing and very low weight loss
- FDA approved for direct food contact applications
- Excellent water repellency
Tospearl™ is available in a variety of particle sizes and suitable for most film thicknesses. The diameter of the resin bead should approximately be 40% of the skin layer thickness to provide the lowest possible COF to ensure adequate bead retention.
1 Measured on a COULTER COUNTER MULTISIZER II (Electrical Sensing Zone method)
2 A 2% dispersion in methanol/water (1/1)
* Tospearl is a trademark of Momentive Performance Materials Inc.
SEM illustrates the uniform size distribution of the spherical 2, 3, 4.5, and 10-micron beads.
Formulations based on Tospearl™ antiblocking additive provide the solution to a lower COF. At the same time, enhancing various antiblocking characteristics within BOPP film. Tospearl has received FDA approval for use in food contact packaging and film applications. Below illustrates the additive and extrusion process with Tospearl.