Compounders face two main processing challenges during the production of color masterbatches used for plastics: pigment agglomeration and excessive equipment torque and die pressure. If not properly addressed, these challenges can lead to poor-quality masterbatches and low efficiency, and, at worst, they can damage expensive processing equipment.
Pigment Agglomeration
In the manufacture of color masterbatches, pigment dispersion is a primary concern. Color masterbatches are highly filled with pigment particles, minerals, and other additives used to create plastics. The pigments, minerals, and fillers tend to agglomerate if not properly dispersed, leading to reduced color yield and lower masterbatch processing economy.
Torque & Die Pressure
The high melt viscosity of a color masterbatch combined with pigment agglomerations is the primary cause of excessive torque and die pressure during manufacturing. This may create off-quality color masterbatches and extended downtimes to fix manufacturing equipment that breaks due to wear and tear. In addition to wear and tear, the excessive torque and die pressure increase energy consumption, thus increasing the cost of manufacturing operations.
Optimizing Masterbatch
The challenges to color masterbatch manufacturing outlined above must be considered when formulating. Improving the dispersion of pigments, fillers, and additives in a masterbatch formulation increases yield and makes for a more efficient end product. Also, reducing torque and die pressure can improve output and reduce the cost of manufacturing. Historically, achieving these two tasks often requires tinkering with resin selection and extrusion parameters while maintaining the desired physical properties of the end product, which can be daunting. Luckily, there are dispersing agent additives for color masterbatch production that can improve pigment dispersion and extrusion operations without altering the tensile properties of the end product.
EPOLENE® Dispersants & Processing Aids
EPOLENE®, manufactured by Westlake, is a line of polyethylene and polypropylene wax polymers that are outstanding dispersion agents for pigments and other additives used in masterbatch compounding. When added in small amounts to color masterbatch formulations, EPOLENE® dispersants prevent the agglomeration of pigment particles and help produce a homogeneous dispersion. In turn, EPOLENE® increases color strength while reducing the amount of torque and die pressure required to pelletize the pigment masterbatch.
Color Masterbatch Pigment Dispersion
To demonstrate the usefulness of EPOLENE® as a polymeric pigment dispersant in color masterbatches, a lab study compared pigment particle size and distribution of a linear low-density polyethylene resin and blue pigment at a ratio of 15:3 in masterbatches compounded with and without EPOLENE®. Microscopic images from the study are below.
The images show that the addition of EPOLENE® C-15 to the color masterbatch promotes a more homogeneous dispersion with far fewer pigment agglomerations amongst the resin. Quantitatively, EPOLENE® C-15 reduced the particle size by up to 80%. This dispersion improvement also increases color yield, allowing for less pigment to be used to achieve the desired color and resulting in pigment cost savings. The data below shows the pigment-dispersing effect EPOLENE® has on increasing color strength.
Another way to quantify this improvement in pigment dispersion is to monitor filter pressure values. The data below shows that as the level of EPOLENE® is increased in masterbatches, the filter pressure value is reduced. This is evidence of the ability of EPOLENE® to prevent particle agglomerations that increase masterbatch filter pressure.
Processing Improvement
EPOLENE® has also proved extremely useful as a processing aid for highly filled mineral masterbatches. In a separate study, a 50% LLDPE and 50% mineral-filled masterbatch was compounded with and without EPOLENE®. The torque, die pressure, and mechanical properties of the masterbatch were measured. There was a 4% reduction in die pressure at 5% loading of EPOLENE® C-15 versus the control, and a 28% reduction in torque was observed at 5% loading of EPOLENE® C-15 versus the control.
Other studies involving masterbatches containing organic pigments, with and without filler, were also carried out and demonstrated a marked reduction in both average torque and die pressure, as seen below.
EPOLENE® reduces torque and die pressure during compounding, resulting in energy savings and increased production rate. Masterbatches can be compounded faster with reduced power consumption, resulting in a more efficient and economical process. It is also important to highlight that while compounding pressure and torque were significantly reduced, the tensile properties of the control plastics remained virtually unchanged compared to the plastics modified with EPOLENE®.
Selecting an EPOLENE® Dispersant for Compounding
There are various commercially available grades of EPOLENE® that vary in polymer type, molecular weight, drop point, density, and melt viscosity. Additionally, certain grades of EPOLENE® are modified with maleic anhydride. These maleated grades are often used as compatibilizers in compounding composites.
*Solid at this temperature. Brookfield viscosity at 190°C = 300 cPs
As with any formulation, selecting the proper materials is critical to success. If you would like assistance in selecting the appropriate grade of EPOLENE® for your masterbatch, contact us today to speak with our highly trained team of product experts.
