1. Introduction

Environmental regulations are driving the global coatings industry toward lower volatile organic compound (VOC) emissions and reduced hazardous substance content. Epoxy resin colorants, as essential components of industrial coatings, must meet increasingly stringent compliance requirements including GB 30981-2020 (China), EU REACH, and US EPA regulations. DENSON SEP series epoxy resin colorants, developed by Dongguan DENSON Functional Materials Co., Ltd., are formulated with low-VOC carrier systems and heavy-metal-free pigment selections to help coating manufacturers achieve regulatory compliance. This article examines the environmental compliance framework, the low-VOC technology behind SEP colorants, and three practical application cases in container coatings, automotive parts, and food-contact packaging.

2. Technical Features and Mechanism

Low-VOC epoxy colorants are pigment dispersions that use reactive diluents, high-boiling solvents, or solvent-free resin carriers instead of traditional volatile solvents such as xylene, toluene, or butyl acetate. The VOC content is defined as the mass of volatile organic compounds released per liter of coating, measured per GB/T 23985-2009 or ISO 11890-2:2020.

DENSON SEP low-VOC colorants achieve environmental compliance through four key technologies:

(1) Reactive diluent carrier: SEP colorants use epoxy reactive diluents (such as alkyl glycidyl ether) as the carrier medium, which participate in the curing reaction rather than evaporating, effectively reducing VOC emissions by 60-80% compared to solvent-based colorants.

(2) Heavy-metal-free pigment selection: All SEP colorants use pigments that comply with EU REACH Annex XVII and GB/T 30981-2020 restrictions, eliminating lead, cadmium, chromium (VI), and other heavy metals. Organic pigments (azo, phthalocyanine, quinacridone) and inorganic pigments (iron oxide, titanium dioxide) are selected based on toxicity and environmental impact assessments.

(3) Low-Aromatic solvent system: For grades requiring some solvent, SEP colorants use high-boiling, low-toxicity solvents (such as propylene glycol methyl ether acetate, PMA) with boiling points above 140°C, reducing evaporation during application and storage.

(4) APEO-free dispersants: SEP colorants use alkyl polyglycoside (APG) and fatty acid ethoxylate-free dispersants, complying with EU 2003/53/EC restrictions on alkylphenol ethoxylates (APEO).

The compliance mechanism: By using reactive diluents that become part of the cured film, SEP colorants ensure that the VOC content of the final coating remains below regulatory limits (typically ≤ 100 g/L for industrial coatings per GB 30981-2020). The heavy-metal-free pigment selection ensures compliance with food-contact and toy safety standards when required.

3. Application Case Study 1: Container Coatings

A container coating manufacturer needed to reduce VOC emissions to meet the International Maritime Organization (IMO) regulations and GB 30981-2020 requirements for marine coatings. Their traditional solvent-based epoxy shop primer had a VOC content of 420 g/L. By switching to DENSON SEP-700L low-VOC colorants at 5% dosage and reformulating with epoxy reactive diluents, the VOC content was reduced to 95 g/L, meeting the ≤ 100 g/L limit.

Key performance: The coating achieved a dry film thickness of 60-80 μm per coat, with a pot life of 4-6 hours at 25°C. Salt spray resistance reached 800h (ASTM B117), and adhesion to blasted steel was ≥ 7MPa (ISO 4624). The color consistency ΔE ≤ 0.8 across production batches, and the coating passed the IMO MSC.215(82) performance standard for shipboard coatings.

4. Application Case Study 2: Automotive Parts Coatings

An automotive parts supplier required low-VOC epoxy primer for plastic bumpers and interior trim components to meet OEM specifications (VOC ≤ 150 g/L) and EU REACH compliance. Using SEP-750L colorants at 4% dosage in a waterborne epoxy primer system, the manufacturer achieved a VOC content of 85 g/L while maintaining excellent adhesion to polypropylene substrates.

Key performance: The primer had a viscosity of 25-35 seconds (Ford Cup #4, ASTM D1200) and a flash-off time of 5-8 minutes at 60°C. Adhesion to PP substrate was 100% (cross-cut test, ASTM D3359, grade 5B). The coating passed 500 hours of QUV accelerated weathering (ASTM G154) with ΔE ≤ 1.5 and gloss retention ≥ 85%. All colorants were REACH-compliant with no SVHC (Substances of Very High Concern) above 0.1% concentration.

5. Application Case Study 3: Food-Contact Packaging Coatings

A food packaging coating manufacturer required epoxy can coatings that comply with GB 4806.10-2016 (China food-contact materials) and FDA 21 CFR Part 175.300 regulations. Using SEP-800L food-grade colorants at 3% dosage in an epoxy-phenolic can coating, the manufacturer achieved full compliance with both Chinese and US food-contact regulations.

Key performance: The can coating had a VOC content of 50 g/L (using water-reducible epoxy resin) and a curing schedule of 10 minutes at 200°C. The cured coating passed global extraction tests per GB 31604.1-2015 and FDA migration tests, with total migration ≤ 10 mg/dm². The colorants contained no heavy metals (Pb < 5 ppm, Cd < 5 ppm, Cr(VI) < 2 ppm) and no bisphenol A (BPA) above the detection limit. The coating maintained excellent chemical resistance to 3% acetic acid and 10% ethanol food simulants.

6. Key Selection Parameters and Usage Recommendations

| Compliance Standard | VOC Limit | Key Restricted Substances | Application |

| GB 30981-2020 | ≤ 100 g/L (industrial) | Heavy metals, formaldehyde | General industrial coatings |

| EU REACH | Registration required | SVHC list (>0.1%) | Export to EU |

| GB 4806.10-2016 | Food-contact grade | Heavy metals, BPA | Food packaging |

| FDA 21 CFR 175.300 | Food-contact grade | Extractives | Food packaging (US) |

Usage recommendations:

(1) Always verify the VOC content of the final coating formulation, not just the colorant, as other components may contribute to VOC emissions.

(2) For food-contact applications, request a food-grade compliance statement and test report from the colorant supplier before use.

(3) When switching from solvent-based to low-VOC colorants, adjust the formulation's rheology and curing schedule, as reactive diluents may affect pot life and cure speed.

(4) Conduct regular third-party testing for heavy metal content and VOC emissions to maintain compliance certification.

(5) For more information on DENSON SEP low-VOC colorant compliance, refer to the DENSON product page.

7. Conclusion

Environmental compliance and low-VOC development are transforming the epoxy colorant industry. DENSON SEP epoxy resin colorants, through reactive diluent carriers, heavy-metal-free pigment selection, low-aromatic solvent systems, and APEO-free dispersants, enable coating manufacturers to meet GB 30981-2020, EU REACH, and FDA regulations while maintaining excellent color performance and coating properties. The three application cases demonstrate that low-VOC colorants can be successfully applied in container coatings, automotive parts, and food-contact packaging without compromising performance.

8. FAQ

Q1: What is the VOC limit for industrial protective coatings in China?

A: According to GB 30981-2020 "Limit of harmful substances of industrial protective coatings," the VOC content limit for epoxy anti-corrosion coatings is ≤ 100 g/L for solvent-based systems and ≤ 80 g/L for waterborne systems. The standard also restricts heavy metals (Pb, Cd, Cr(VI), Hg), formaldehyde, and benzene series compounds.

Q2: How do reactive diluents reduce VOC in epoxy colorants?

A: Reactive diluents are low-viscosity epoxy compounds that act as both carrier solvents for pigments and crosslinking components during curing. Unlike traditional solvents that evaporate during application, reactive diluents chemically bond into the cured film, so they do not contribute to VOC emissions. Common reactive diluents include butyl glycidyl ether (BGE) and phenyl glycidyl ether (PGE).

Q3: Are all DENSON SEP colorants REACH-compliant?

A: Yes, all DENSON SEP series epoxy colorants are formulated to comply with EU REACH regulations. The pigments and raw materials used are screened against the REACH SVHC candidate list, and no SVHC substance is present above 0.1% (w/w). DENSON provides REACH compliance declarations and SDS documents for all SEP colorant products.

Q4: Can low-VOC colorants be used in existing coating formulations without reformulation?

A: Generally, some reformulation is required when switching from solvent-based to low-VOC colorants. The reactive diluent carrier may affect viscosity, pot life, and cure speed. It is recommended to start with a 50% replacement ratio, evaluate performance, and gradually increase the replacement level while adjusting the formulation's curing agent ratio and rheology additives.

Q5: What testing methods are used to verify VOC content in coatings?

A: The standard methods for VOC determination are GB/T 23985-2009 (equivalent to ISO 11890-1) for difference method and GB/T 23986-2009 (equivalent to ISO 11890-2) for gas chromatography method. For regulatory compliance, gas chromatography (GC) is preferred as it can identify and quantify individual volatile compounds. Testing should be conducted by an accredited third-party laboratory.