VOC is one of the important topics when considering environmental measures in a coating factory.

VOC stands for volatile organic compounds.
Simply put, these include organic solvents in coating materials and thinners that evaporate into the air.

Coating processes using solvent-based materials generate VOCs during application, drying, cleaning, and mixing.
VOCs affect odors, the working environment, fire risks, environmental regulations, and customer audits.

VOC control will therefore become increasingly important.

However, it should not be approached too simply.

Just install exhaust treatment equipment.
Just switch to waterborne coatings.
Just switch to powder coating.
Just increase exhaust fan power.

Thinking in terms of only one measure like this may fail.

VOC control must consider coating materials, thinners, application methods, drying ovens, exhaust equipment, cleaning work, and shop-floor operation together.

1. Where do VOCs come from?

VOCs originate at various locations in the coating process.

Typical sources are as follows.

During coating

In spray coating, solvent in the coating material evaporates.
Oversprayed coating material also generates VOCs.

During drying

In drying ovens and air-drying processes, solvent in the coating film evaporates.
In baking processes, heating may also generate odor components or decomposition products.

During mixing

When coating material and thinner are mixed, solvent evaporates while containers are open.

During cleaning

When guns, piping, jigs, and containers are cleaned, cleaning thinner generates VOCs.

During storage

Poor lid management for coating material cans and thinner containers allows solvent to evaporate during storage as well.

VOCs are therefore not only a coating booth issue.
They are generated throughout the coating process.

2. VOC control is about more than environmental regulations

VOC control is often viewed as compliance with environmental regulations.

That is, of course, important.
Factories must comply with laws and industrial park rules.
Audits by Japanese, European, and US customers may also examine VOCs, odors, and the working environment.

However, VOC control goes beyond regulatory compliance.

Reducing VOCs also contributes to the following improvements.

• Reduce the odor burden on operators.
• Reduce coating material losses.
• Reduce booth contamination.
• Reduce filter replacement frequency.
• Reduce fire risks.
• Limit exhaust treatment costs.
• Improve readiness for customer audits.
• Improve the factory’s environmental image.

VOC control thus affects the environment, safety, quality, cost, and brand image.

3. There are three approaches to VOC control

VOC control is easier to understand when considered in three broad approaches.

1. Reduce VOCs through materials.

Review coating materials and thinners to reduce the amount of VOCs generated.

2. Treat VOCs through equipment.

Treat generated VOCs using exhaust treatment equipment.

3. Reduce VOCs through operation.

Reduce VOC generation or dispersion through application methods, cleaning methods, container management, and improved transfer efficiency.

The important point is not to consider these three approaches separately.

Changing materials alone will not stabilize quality if the equipment is unsuitable.
Installing equipment alone will result in high operating costs if generation is high.
Improving operation alone has limits if the coating material itself has a high VOC content.

VOC control requires a combination of materials, equipment, and operation.

4. Reduce through materials: Low-VOC, waterborne, and powder coatings

Reviewing materials is the first option to consider for reducing VOCs.

Typical options are as follows.

Low-VOC coatings

These contain reduced amounts of solvent.
They may be considered with operating practices similar to existing solvent-based coating.

High-solids coatings

These have a high solids content.
They may reduce the amount of solvent required to achieve the same film thickness.

Waterborne coatings

These replace some or much of the solvent with water.
They are effective for VOC reduction, but drying conditions, humidity control, equipment materials, and cleaning methods must be checked.

Powder coatings

This method deposits powdered coating material electrostatically and cures it by baking.
It generally greatly reduces VOCs, but the baking oven, powder booth, recovery equipment, and color change operation must be checked.

Changing materials is effective, but it is not a simple substitution.

Coating film performance.
Appearance.
Drying conditions.
Equipment suitability.
Application method.
Surface preparation.
Quality standards.
Cost.

These must be checked before adoption.

5. Thinner selection also affects VOC control

Thinners are important for VOC control as well as coating materials.

Thinners are used to adjust viscosity and drying properties and for cleaning.
The type and amount of thinner therefore change VOC generation and odors.

For example, using a large amount of highly volatile thinner to speed drying may increase odors and VOCs during application.
On the other hand, excessively slow drying causes sagging, dirt pickup, and process delays.

Thinner therefore cannot be selected based solely on VOCs.

Check the following when selecting thinner.

• Compatibility with the coating material
• Viscosity adjustment characteristics
• Drying rate
• Coating film appearance
• Odors
• Working environment
• Fire risks
• Equipment suitability
• Cleaning ability

CoatureVietnam’s Thinner Streamer considers thinner an important material supporting coating quality, the working environment, and stable supply, rather than merely a diluent.

6. Treat through equipment: An approach to exhaust treatment equipment

Where VOCs are generated, exhaust treatment equipment can be used to treat them.

Typical methods include the following.

• Thermal oxidation
• Regenerative thermal oxidation
• Catalytic treatment
• Activated carbon adsorption
• Absorption treatment

These systems treat VOCs that have been generated.

However, exhaust treatment equipment tends to be expensive and also incurs operating costs.

Fuel costs.
Electricity costs.
Catalyst replacement costs.
Adsorbent replacement costs.
Filter replacement costs.
Waste disposal costs.
Cleaning costs.
Inspection costs.

Before introducing exhaust treatment equipment, the amount generated must therefore first be established.

Which processes generate VOCs?
What is the exhaust airflow volume?
What is the VOC concentration?
What are the odor components?
Does the exhaust contain dust or tar?
Is moisture content high?
Is production volume constant or variable?

Selecting treatment equipment without checking these points may fail to deliver the expected results.

7. Pretreatment is also important for exhaust treatment equipment

Pretreatment is important when introducing VOC treatment equipment.

Exhaust from drying ovens and coating booths may contain the following substances in addition to VOCs.

• Coating mist
• Dust
• Moisture
• Tar
• Oil
• Resinous deposits
• Odor components

Allowing these substances to enter treatment equipment directly may cause problems.

The catalyst deteriorates.
Activated carbon becomes saturated quickly.
Filters clog.
Ducts become contaminated.
Treatment efficiency falls.
Fire risks rise.

Dust removal, mist removal, cooling, tar removal, or other pretreatment may therefore be necessary before exhaust treatment equipment.

VOC treatment must be considered as a system from exhaust inlet to outlet, rather than as a standalone machine.

8. Reduce through operation: Improve transfer efficiency

Operational improvement is also important in VOC control.

One example is improving transfer efficiency.

Transfer efficiency is the proportion of sprayed coating material that actually attaches to the workpiece.

When transfer efficiency is low, much of the coating material becomes overspray.
Overspray also generates VOCs.
It also increases the burden on booth filters and sludge treatment.

Methods of improving transfer efficiency include the following.

• Select an appropriate spray gun.
• Adjust air pressure appropriately.
• Standardize gun distance
• Adjust material flow rate.
• Stabilize application speed.
• Use electrostatic coating appropriately.
• Review jigs and workpiece arrangement.
• Use robots and automatic guns.
• Reduce unnecessary spraying.

Improved transfer efficiency reduces coating material consumption and VOC generation.

This is both an environmental measure and a cost reduction measure.

9. Reduce through operation: Review cleaning work

Cleaning work is an easily overlooked source of VOCs.

Cleaning coating guns.
Cleaning piping.
Cleaning containers.
Cleaning jigs and tools.
Cleaning during color changes.

These tasks often use thinner and generate VOCs.

There are many opportunities to improve cleaning work.

• Record cleaning thinner consumption.
• Reduce cleaning in open containers.
• Use containers with lids.
• Provide local exhaust ventilation at the cleaning location.
• Plan the color change sequence carefully.
• Reduce amounts discarded after use.
• Check the potential for recovery and reuse.
• Create cleaning SOPs.

Looking only at VOCs during coating overlooks those generated by cleaning.
VOC control must therefore include cleaning work as well as coating work.

10. Reduce through operation: Container management and mixing

Management of coating material cans and thinner containers also affects VOC generation.

Container lids remain open.
The mixing area is poorly ventilated.
Unnecessary amounts are dispensed in advance.
Used thinner containers are left open.
Wiping cloths and cleaning liquids are not sealed.

These conditions generate VOCs even when coating is not being performed.

The following points are important for container management.

• Close lids immediately after use.
• Dispense only the amount needed.
• Ensure ventilation in the mixing area.
• Place used wiping cloths in sealed containers.
• Do not leave cleaning thinner containers open.
• Train operators in the rules.

Even small operational improvements contribute to VOC reduction when sustained.

11. Check VOCs from drying ovens

VOCs are not generated only in coating booths.

Drying ovens also generate VOCs.

Solvent evaporates from the film after coating and enters the drying oven exhaust.
Depending on baking conditions, odor components or tar may also be generated.

Check the following for drying oven exhaust.

• Exhaust airflow volume
• Exhaust temperature
• VOC concentration
• Odors
• Tar
• Duct contamination
• Potential for heat recovery
• Need for exhaust treatment equipment

Energy conservation is also important in VOC control for drying oven exhaust.

When exhaust treatment equipment is used, discarding the heat directly causes substantial energy losses.
Regenerative treatment systems such as RTOs may provide energy savings through heat recovery.

VOC control for drying ovens requires considering environmental measures and energy conservation together.

12. Common VOC control challenges in Vietnamese factories

Vietnamese factories often face the following VOC control challenges.

VOC generation is not measured.
Odor problems and VOC problems are confused.
The response consists only of increasing exhaust fan power.
Cleaning thinner consumption is not controlled.
Coating material losses and overspray are not viewed as VOC sources.
Drying oven exhaust is not checked.
Drying conditions and quality are insufficiently checked when switching to low-VOC coatings.
Exhaust treatment running costs are overlooked.
Insufficient operator training prevents thorough container management.

VOC control cannot be solved by equipment personnel alone or environmental personnel alone.

Coating material specialists, equipment personnel, shop-floor operations, quality assurance, purchasing, and management must consider it together.

13. Basic items to check for VOC control

Organizing the following items provides a practical approach to VOC control.

1. Materials used

Check the types and amounts of coating materials, thinners, and cleaning solvents used.

2. Processes generating VOCs

Check whether VOCs arise during coating, drying, cleaning, mixing, or storage.

3. Exhaust conditions

Check exhaust airflow volume, concentration, odors, and temperature.

4. Transfer efficiency

Check how much coating material attaches to the workpiece and how much is lost.

5. Cleaning operation

Check cleaning thinner consumption, cleaning methods, and container management.

6. Potential for material changes

Check the potential to switch to low-VOC, waterborne, or powder coatings.

7. Equipment treatment

Check exhaust treatment equipment, pretreatment, heat recovery, and maintainability.

8. Cost

Check material costs, equipment costs, operating costs, and waste disposal costs.

9. Quality effects

Check effects on film performance, appearance, drying properties, and adhesion.

10. Operator burden

Check effects on odors, cleaning work, protective equipment, and the working environment.

14. The value CoatureVietnam sees in VOC control

CoatureVietnam does not regard VOC control as merely environmental regulatory compliance.

VOC control is an important starting point for improving the coating process.

Reducing VOCs helps reduce coating material losses.
Reducing odors helps reduce the burden on operators.
Reviewing exhaust treatment may save energy.
Reviewing cleaning operation helps reduce thinner consumption.
Considering a change of coating materials provides an opportunity to review quality, the environment, and cost.

CoatureVietnam considers VOC control from the following four perspectives.

• Material: Coating materials, thinners, and cleaning solvents
• Method: Application methods, cleaning methods, and container management
• Machine: Booths, drying ovens, and exhaust treatment equipment
• Man: Operator training and shop-floor rules

Under Management, it also organizes regulatory compliance, customer audits, costs, and investment decisions.

This puts into practice the principle CoatureVietnam values:
“Coating the Future with Science and Care”.

Science means making VOC sources, consumption, exhaust conditions, and transfer efficiency visible.
Care means reducing the odor burden on operators, lowering environmental risks, and creating conditions in which the factory can operate with confidence.

Conclusion

Installing exhaust treatment equipment alone is insufficient for VOC control.
Simply switching to low-VOC coatings is also insufficient.

VOCs involve coating materials, thinners, cleaning, mixing, drying, booths, exhaust, and shop-floor operation.

This is why VOC control must combine the following three approaches.

Reduce through materials.
Treat through equipment.
Reduce through operation.

Improve transfer efficiency.
Reduce cleaning thinner consumption.
Manage containers thoroughly.
Check drying oven exhaust.
Consider exhaust treatment equipment where necessary.
Check the potential to switch to low-VOC or powder coatings.

VOC control is about more than environmental regulations.
It is an improvement activity that makes the working environment better, reduces coating material losses, and increases confidence in the factory.

CoatureVietnam supports VOC control suited to Vietnamese factories by examining coating materials, equipment, and operation as a whole.