Purging Compounds for Extrusion Blow Molding & Injection Blow Molding

Whether you’re struggling with cleaning out an accumulator head or running PET preforms, Asaclean® has a high-quality purging compound designed for your processing challenges.

Here’s why Asaclean® Purging Compounds are the preferred choice for the most successful blow molders worldwide.

Blow molding is the one process that’s been slow to embrace purging. For many years, purge suppliers simply didn’t have grades that performed well enough to justify implementing a purge program. Because of the reluctance to purge, many blow molders experience changeover times between 8 and 24 hours. Fortunately, purging compounds have come a long way in recent years. This section will discuss the 6 main kinds of blow molding, offer purging tips to improve your efficiency and recommend products to meet your needs.

Why Asaclean® Purging Compounds are the Best Choice for Blow Molders

blow molding asaclean best choice

1. Our Products Will Solve Your Issue

We offer Mechanical Purging Compounds, Chemical Purging Compounds, and Purging Concentrates designed to tackle your unique set of processing challenges in blow molding. We excel at reducing long changeover times and understand your processing headaches.

We specialize in blow molder cleaning and excel in your most difficult applications.

Once we identify your needs, we will help you choose the best grade of Asaclean® for you.

64%

On average, Asaclean® 's extrusion blow molding customers save 64% on reduced scrap & downtime.

Blow molding is one of the most widely used plastic forming processes and is used in the production of bottles, large drums, tanks, toys, and countless automotive applications.

Until recently, the most popular method for purging extrusion blow molding equipment had been to use the next processing resin or regrind. This may get you from point A to point B in the short term. However, this approach results in longer purge times, higher scrap rates, and greater residue buildup over the long term. We’ve seen blow molders not using Asaclean® taking up to 24 hours on changeovers.

We use Asaclean® to purge our screw and barrel during changeovers and it cut our changeover times in half. Asaclean® does great things at the right price.”

Will , Process Technician, Packaging, Midwest

For most blow molding plants, faster changeovers and lower scrap rates are the most significant factors for staying competitive. Many customers have more than a 60% reduction in costs with the right grade of Asaclean®, saving them tens if not hundreds of thousands of dollars each year. For most blow molders, we usually recommend Asaclean®’s Purging Concentrate or Chemical Purging Compounds because they excel in low-flow areas. They are effective in cleaning accumulators or flow lines (especially if they are poorly designed). For many other situations, we recommend Mechanical Grades based on their cleaning power. With that said, every situation is different.

For both extrusion blow molding and injection blow molding, Asaclean® Purging Compounds:

Dramatically shorten material and color changeover time
Effectively clean accumulator heads
Can run through heads without taking your machine apart
Will run through your entire system
Can hold the parison
Successful for multilayer lines
Clean the screw & barrel thoroughly
Reduce scrap and defect rates
Help facilitate easier screw pulls
Seal your machine during shutdowns to promote easier start-ups
Remove carbon contamination & black specks

With the world-class R&D team of Asahi Kasei in Japan, Asaclean® offers incredible cleaning performance coupled with expert technical & product support.

We’re firm believers – Asaclean® Purging Compounds really work as advertised! Every processor should try them.”

Glen , Process Engineer, Consumer Goods, Ohio

61%

On average, Asaclean®’s injection blow molding customers save 61% on reduced scrap & downtime.

2. Our Team of Experts Understands Your Challenges & Will Train Your Entire Team for Success

Asaclean® Technical Service Representatives offer a unique level of service not found in other areas of the industry. Many of our Purging Experts used Asaclean® as customers themselves before joining our team.

Your point-of-contact isn’t a salesperson. They are a processor.

blow molding 6

With over 200 years of combined processing experience, we understand your issue and can offer solutions. We’ve seen it all and are here to help you.

When you select Asaclean®, we will diagnose your issues, build out a free Purge Program, and train your shifts on how to use Asaclean® to get the best results.

We will help you trial our product, provide in-person or virtual training, answer any questions, and be available however necessary to help your team succeed.

Sometimes keeping good labor can be difficult.

Don’t worry. As you find new hires, we’ll train them as well.

Asaclean® support goes over and above. Training is a part of that. it's great to have our rep in front of people giving training, because if five pounds works, ten pounds is not better. Training is key when you're using these products, and I feel that if I called my Asaclean® rep for help at midnight he would probably answer.”

John S. , Manufacturing Manager, Consumer Goods, Northwest

Asaclean® Blow Molding Purging Best Practices

Since blow molding is a term applied to several unique molding processes, it makes sense to look at each of the major blow molding processes, and discuss purging tips and best practices, by category:

Blow Molding 2

Intermittent extrusion process
Bottles: Large drums, garbage cans, gasoline tanks
Typical Resins: HDPE, PP, PPO
Machinery: Davis-Standard, Uniloy, Kautex, Jackson Machinery, R&B; Plastics
Typically, single layer
Dies are not polished – glass-filled grades are generally safe to use
Largest area of concern when purging is the accumulator head – this is a low-pressure area where it can be difficult to get sufficient scrubbing action. PE usually layers, so you need a grade of Asaclean® designed for the challenge.
Clean the extruder before the accumulator.
Insufficient cleaning of the accumulator head leads to die lines and color/burn streaks in the final parts.
When cleaning the accumulator:
- fill to 100%, then push out 25%
- fill to 100%, then push out 50%
- fill to 100%, then push out 75%
- Fill to 100%, then push out the full 100%
“Disco purge” – changing screw speeds, as well as stopping and starting screw rotation, allow for better screw cleaning.
Use either an aggressive cleaner Mechanical Grade like Asaclean® EX, PLUS Grade, or a Chemical Grade like NCR with good foaming action.
Seal the extruder and accumulator head with a shutdown-approved grade of Asaclean® during extended downtime events.

Blow Molding 5

Two Separate & Distinct Processes – intermittent injection molding + then a re-heating of the injection molded preform prior to blowing it into a final geometry.
Bottles: water bottles, carbonated soft drink bottles, clear or highly translucent personal care.
Typical Resins: PET, some oriented polypropylene (oPP)
Standard Machinery: For injection molding machines: Husky, Milacron. For blow molding machines: Sidel, Sipa, Krones.
Typically, single layer but there is a growing multilayer market.
Preforms can cool or “cure” between injection and blow molding processes.
It is best to allow the preforms to come down to ambient plant temperatures prior to re-heating & blowing – this is best achieved by practicing stringent FIFO (First- in, First-out) procedures with preforms, as well as enforcing rules that the preforms must be in the plant for at least 12 hours (more for very thick preforms or large gaylords) prior to blow molding.
Focus on cleaning the molding machine following standard injection molding purging procedures.
Use Asaclean® PLUS Grade which is approved for high cavitation hot runners as preforms are often molded in very high cavitation (96+ cavity) molds.
Use an Asaclean® purging compound that is easily displaced by PET after purging to maintain optimal part clarity.
Closely monitor preform inclusions like carbon, because once it starts, you make a lot of bad parts in a short period of time.
Make sure that manifold drops are on as many separate heating zones as possible to insure consistent heating of inboard and outboard drops.
Seal the injection unit with a shutdown-approved grade of Asaclean® during extended downtime events.
IMPORTANT NOTE: Purging compounds are not used to directly clean the blow molding unit (Sidel, Krones, Sipa, etc.). The key here is that good preforms = good bottles. Keep contamination out of the injection process for the best results in the blowing process.
Monitor air temperatures in the blow molding plant. We frequently observe good machines making bad bottles after a bay door was briefly opened during the winter.

Blow Molding 2

Intermittent extrusion process
Bottles: Large drums, garbage cans, gasoline tanks
Typical Resins: HDPE, PP, PPO
Machinery: Davis-Standard, Uniloy, Kautex, Jackson Machinery, R&B; Plastics
Typically, single layer
Dies are not polished – glass-filled grades are generally safe to use
Largest area of concern when purging is the accumulator head – this is a low-pressure area where it can be difficult to get sufficient scrubbing action. PE usually layers, so you need a grade of Asaclean® designed for the challenge.
Clean the extruder before the accumulator.
Insufficient cleaning of the accumulator head leads to die lines and color/burn streaks in the final parts.
When cleaning the accumulator:
- fill to 100%, then push out 25%
- fill to 100%, then push out 50%
- fill to 100%, then push out 75%
- Fill to 100%, then push out the full 100%
“Disco purge” – changing screw speeds, as well as stopping and starting screw rotation, allow for better screw cleaning.
Use either an aggressive cleaner Mechanical Grade like Asaclean® EX, PLUS Grade, or a Chemical Grade like NCR with good foaming action.
Seal the extruder and accumulator head with a shutdown-approved grade of Asaclean® during extended downtime events.

Continuous extrusion process – the molds shuttle back and forth to grab the parison, then away from the head to blow the parison.
Bottles: personal care up to 20 oz, pharmaceutical, large jars
Typical Resins: LDPE, HDPE, PP, PVC, extrudable PET (ePET), “soft touch” resins
Standard Machinery: Bekum, Techne, Kautex, R&B; Plastics, Magic
Often multiple extruders for multiple bottle layers
Multi-layer lines — virgin, re-grind, adhesive, barrier, virgin + color, etc.
Dies are not polished – glass-filled grades are generally safe to use
It’s not critical that you hold a parison while purging – these machines are relatively easy to start back up after purging, and gravity will control the purge after exiting the head tooling.
All extruders do not need to be purged the same – perhaps the Ethylene vinyl alcohol (EVOH) and virgin layers are contaminant free, for example. Purge only the extruders that need it.
Run the die as close to closed as safely possible to increase melt pressure and shear – keep an eye on extruder amps to make sure that you are not overworking the motor.
“Disco purge” – changing screw speeds, as well as stopping and starting screw rotation, allow for better screw cleaning.
Efficient EBM department operations are all about scheduling colors in order from light to dark when possible and using a purging compound when moving back from dark to light.
Seal the extruder and head with a shutdown-approved grade of Asaclean® during extended downtime events.

Blow Molding 3

Continuous extrusion process
Bottles: laundry detergent, motor oil, personal care, beverages
Typical Resins: HDPE, LDPE, extrudable PET (ePET), Nylon
Machinery: Graham Engineering, Techne, Kautex, R&B; Plastics
Often multiple extruders for multiple layers, including oxygen barrier layers
Multi-layer lines — virgin, re-grind, adhesive, barrier, virgin + color, etc.
Dies are not typically polished – glass-filled grades are generally safe to use
When purging, it is desirable to keep the machine running because wheels take long periods to start up; and those that extrude up, can be quite messy during purging.
Use a grade of Asaclean® with good melt strength and low MFI to hold a parison (if taking the wheel down is not desirable). PLUS Concentrate is also a solid option.
Profile the die while running – this will mimic the “Disco Purge” effect
If keeping the wheel running, do not blow the parison – inorganics in the purging compound could scuff polished mold cavity surfaces.
Seal the extruder and head with a shutdown-approved grade of Asaclean® during extended downtime events.

Hybrid of intermittent injection molding + adjacent blow molding operation
Bottles: small clear or highly translucent personal care up to 8 oz, pharmaceutical bottles
Typical Resins: PET, some oriented polypropylene (oPP)
Standard Machinery: Aoki, Nissei
Typically, single layer
Molten plastic is injected through a manifold into cavities, and onto injection cores. The preforms then index to a blowing station, where they are blown into a final geometry, all within the same machine footprint. Note: preforms may pass through a conditioning station between injection and blow, depending on machine platform.
Do not attempt to mold or blow parisons
Focus on cleaning the injection unit first, by backing it away from the manifold and following standard injection molding purging procedures.
To minimize carbon contamination, keep nozzle drool to a minimum, and clean nozzle drool regularly to keep it from entering the manifold.
Use a regular purging schedule to keep preforms free of contamination.
Weigh and record nozzle drool to make sure that you are always trying to improve your process.
When using a Asaclean®, it is generally best if added directly to the feed throat, as opposed to being dried with the resin. The drying process could activate some foaming agents in chemical purges.
Seal the injection unit with a shutdown-approved grade of Asaclean® during extended downtime events.

Blow Molding 4

Typical Resins: LDPE, HDPE, PP, PVC
Standard Machinery: Uniloy, Rainville, Jomar
Typically, single layer
Molten plastic is injected through a manifold into polished cavities, and onto polished injection cores. The preforms then index to a blowing station, where they are blown into a final geometry, all within the same machine footprint.
Due to the polished finish of the cavities, glass-filled grades are not recommended.
Not critical that you blow a parison while purging – these machines are easy to start back up after purging.
Make sure that nozzles are balanced to at least 90% for optimal processing.
Back the injection unit away from the manifold and follow standard injection molding purging procedures.
Once the screw and barrel are free of contamination, move the injection unit back up to the mold and begin to extrude purging compound into and through the manifold with the injection mold open. DO NOT CLOSE THE MOLD.
Extrude roughly ½ barrel capacity through the manifold. Using the remaining ½ barrel capacity, run a series of high velocity short shots through the manifold to maximize pressure and cleaning.
“Disco purge” – changing screw speeds, as well as stopping and starting screw rotation, allow for better screw cleaning.
If running PVC, it is imperative that regular purging is scheduled to prevent the buildup of carbon in the screw and manifold.
Seal the injection unit with a shutdown-approved grade of Asaclean® during extended downtime events.

Blow Molding 5

Two Separate & Distinct Processes – intermittent injection molding + then a re-heating of the injection molded preform prior to blowing it into a final geometry.
Bottles: water bottles, carbonated soft drink bottles, clear or highly translucent personal care.
Typical Resins: PET, some oriented polypropylene (oPP)
Standard Machinery: For injection molding machines: Husky, Milacron. For blow molding machines: Sidel, Sipa, Krones.
Typically, single layer but there is a growing multilayer market.
Preforms can cool or “cure” between injection and blow molding processes.
It is best to allow the preforms to come down to ambient plant temperatures prior to re-heating & blowing – this is best achieved by practicing stringent FIFO (First- in, First-out) procedures with preforms, as well as enforcing rules that the preforms must be in the plant for at least 12 hours (more for very thick preforms or large gaylords) prior to blow molding.
Focus on cleaning the molding machine following standard injection molding purging procedures.
Use Asaclean® PLUS Grade which is approved for high cavitation hot runners as preforms are often molded in very high cavitation (96+ cavity) molds.
Use an Asaclean® purging compound that is easily displaced by PET after purging to maintain optimal part clarity.
Closely monitor preform inclusions like carbon, because once it starts, you make a lot of bad parts in a short period of time.
Make sure that manifold drops are on as many separate heating zones as possible to insure consistent heating of inboard and outboard drops.
Seal the injection unit with a shutdown-approved grade of Asaclean® during extended downtime events.
IMPORTANT NOTE: Purging compounds are not used to directly clean the blow molding unit (Sidel, Krones, Sipa, etc.). The key here is that good preforms = good bottles. Keep contamination out of the injection process for the best results in the blowing process.
Monitor air temperatures in the blow molding plant. We frequently observe good machines making bad bottles after a bay door was briefly opened during the winter.