Cost Savings Solutions

Residue Issues & Clear Resins

Clear resins always shine a light on any minor contamination issues you may experience. Processors experience residue issues when their purge or previous production resins haven’t been displaced from your machine. These are some of the most challenging processing situations. In fact, Asaclean® customer surveys revealed “going into clear parts” and “residue” as two of the top-five biggest headaches. Fortunately, Asaclean® Purging Compounds are an excellent solution for clear applications and residue issues alike.

How Asaclean® Provides Clear Savings

Clear parts don’t allow for any mistakes. Period.

If you run from colors to clear, or run materials like PC, PET, PE, PS, or PMMA, you know what we’re talking about. Black specks. Haze. Streaks. Cloudiness.

Clear resins and clear parts keep you honest. Contamination can’t be camouflaged. Fortunately, we have you covered.

51%

On average, Asaclean® customers save 51% on clear applications.

Asaclean®’s industry-leading R&D department has spent almost 30 years perfecting solutions for clear resins and parts. But those years of R&D paid off, and we offer numerous options to make clear resins easier to work with. E Grade, EX Grade, & PLUS Grade all excel for clear applications, but work with an Asaclean® Purging Expert to find out the best product for your specific needs. But the products are just part of the equation. There are some easy ways to avoid contamination when using clear resins. These two tips will help you stop contamination issues in their tracks:

1. Practice Preventative Purging

The best offense is a good defense. If you purge preventatively, you will avoid most contamination issues in the first place. Purging regularly will guarantee better quality in less time. If your screw and barrel are clean, you will have fewer issues with clear resins.

2. Aggressively Displace Your Purge

If you’re experiencing contamination issues when changing clear production resins, low-to-medium back pressure and screw speeds are often to blame. Some assertiveness is needed when purging certain resins like Bayer’s Texin, Desmopan (TPU) and Makrolon (PC). To help minimize contamination with clear resins, follow these easy but effective steps.

For Injection Molding:

Keep the screw in the full forward position by increasing backpressure to the maximum safe level.
Increase the screw speed to the highest safe level once the barrel is full of the production resin.
Once the production resin is free of the purging compound residue, drop the backpressure and perform short, high-velocity injection shots.

For Extrusion:

Plug any vents on the barrel.
Leave a breaker plate in place to create some back-pressure in the barrel.
Use the highest screw speed available on the extruder without tripping out the motor.

Ultimately, if you purge between material/color changeovers, seal your machine during shutdowns, and purge with an excellent cleaner like EX Grade at the first indication of contamination, most of your challenges with clear resins will be solved.

But what about residue?

Every time I use EX Grade I have been very pleased. It is super effective before, during, and after clear and transparent jobs.”

Bryan , Process Engineer, Custom Molder, Alabama

How to Solve Residue Issues with Asaclean®

If you’re following a Purge Program and doing the right things (purging during changeovers, sealing with purge during shutdowns, and preventatively purging periodically during longer runs), you might be surprised and worried to find you’re still dealing with residue issues.

Why is this happening?

There’s a good chance you haven’t effectively purged the purging compound from the machine.

To be clear, this does NOT mean that your purge leaves lots of residue when used correctly. It simply means you haven’t effectively purged the purge. Your solutions are actually very simple, and we have some easy steps to stop residue problems from recurring.

Contamination and resin or purging compound residue are costly to your company's success – both in the amount of product that cannot be sold and in the resulting production downtime that occurs.

The following are five simple tricks for minimizing purging compound residue in your facility’s machines:

1. Use an Asaclean® Grade Formulated for Lower Residue

The melt flow index (MFI) of your resins is a major factor in purging residue issues, especially if the purge is much stiffer than the next resin. MFI is the first characteristic to consider when selecting a purging compound that’s going to effectively purge resins and contamination.

A low-residue purging compound is needed if your MI is high, while a glass-filled purging compound grade may be necessary to flush out contamination.

If you’re experiencing issues with residue in your machines, use a grade designed for residue-sensitive or low-temperature resins. These grades are formulated for lower residue and can be used in conjunction with other grades, as a chaser, whenever you’re trying to reduce purging compound residue.

With Asaclean®, it removed the colorant out and displaced the purge to a clear consistency right away. We had no residue. This allowed us to go right back into running good parts with the least amount of scrap I've ever seen."

Dan , Process Engineer, Custom Molder, Midwest

If contamination exists, purge first with the glass-filled purging compound grade (please note: this is for the screw and barrel only), and then follow with the low-residue grade prior to transitioning to the next resin. If no contamination exists, just use the low-residue grade.

EX Grade & E Grade are two of the better performing purging compounds for residue. Our PLUS Grade Purging Concentrate also performs extremely well for clear applications and for residue issues. PLUS uses your production resins, so you know the MFI will always be correct to displace the purge.

If you’re using hot runners, PLUS is once again a solid choice, but check with your Purging Expert for the correct grade to use. Also, ask your supplier about proper procedures for hot runner cleaning, as the method is different from purging other machine parts.

Work with a Purging Expert to be certain that your next resin will “purge the purge.”

2. Use the Recommended Temperature Range for the Purging Process

yellow, green, and blue plastic material Purging process temperature and MFI are the most consistent indicators of how to successfully eliminate residue. That’s why it’s critical to use the recommended temperature range for the purging compound and resin.

If you use a purging compound that is not designed for a specific temperature range, it may stiffen and leave behind residue. For example, low-temperature resins, such as PVC, require a purging compound specifically designed to run at lower temperatures.

With the cleaning power of a proper purging compound and purging process for your resin transitions, preventing residue is easy for your crew. Using the right purging procedures helps you gain back machine capacity and experience a significant scrap rate reduction. Contamination is eliminated, your residue issues are resolved, and your production runs are smooth and efficient as you switch from color to color on one machine.

3. Use High Screw Speed and Back Pressure

If you’re experiencing issues with residue when changing production resins, low-to-medium back pressure and screw speeds are often to blame. Certain resins require some level of assertiveness in the form of high screw speed and backpressure. Please note this may not apply to shear or heat sensitive resins.

We're now going from a black nylon to a clear PC with no black specks, no residue, & no scrap. Our guys can't believe their eyes.”

Lucas G. , 2nd Shift Lead, Sporting Goods Molder, Southeast

4. Perform High-Velocity ‘Air Shots’

The check ring and nozzle are areas where color or resin often hang up, leading to residue issues.

After completing general purging procedures for cleaning the screw and barrel, it’s recommended to charge the machine with a small quantity of purging compound and perform short, high-velocity injection air shots (not into the mold).

The action of short, high-velocity shots blasts the purging compound into tight areas and dead spots the material wouldn’t reach otherwise.

5. When Possible, Move from Light to Dark Colors

When setting up your production schedule, move from clear to light to dark colors whenever possible. Darker color resins leave more visible residue than lighter colors, so moving from light to dark helps hide the effects of purge residue and residual color, and decreases the total time spent purging.

Excessive downtime negatively impacts your business’s bottom line and your ability to meet or exceed business projections. By following the tips above – and implementing the right purging procedures – you can effectively minimize purging compound residue and contamination so your production runs stay on track.