
Product Name: Optical Brightener 4BK / Fluorescent Brightener 113 / FBA 113
Chemical Name: Disodium Fluorescent Brightener 113 / Stilbene Disulfonic Acid Derivative
Color Index: C.I. 113
CAS: 12768-92-2
Molecular Formula: C₄₀H₄₀N₁₂Na₂O₁₆S₄ / C₄₀H₄₂N₁₂Na₂O₁₀S₂
Formula Weight: 960.94 – 1165.05 g/mol
Synonyms: Fluorescent Brightener 113; FBA 113; Optical Whitening Agent 4BK; Fluorescent Brightener 4BK; C.I. 113; Optical Brightening Agent 4BK
Application:
Textiles (Cotton, Viscose, Polyester/Cotton Blends, Nylon, Linen), Paper Manufacturing (Pulp Whitening, Surface Sizing), Laundry Detergents, Soaps
1.Product Description
Achieve Brilliant, Long-Lasting Whiteness with Optical Brightener 4BK – The Premium Stilbene-Based Brightener for Textiles and Paper.
Optical Brightener 4BK, internationally designated as Fluorescent Brightener 113 (C.I. 113), is a high-performance anionic fluorescent whitening agent engineered specifically for cellulosic fibers and their blends . This sophisticated stilbene-based compound features a unique disulfonic molecular architecture that delivers exceptional whitening efficacy combined with outstanding chemical stability .
Operating on advanced fluorescence technology, Optical Brightener 4BK absorbs invisible ultraviolet radiation and re-emits it as brilliant blue-violet visible light, effectively neutralizing the natural yellowish cast of fabrics and paper pulp . This optical compensation mechanism creates a radiant, "whiter-than-white" appearance that enhances the perceived quality of finished products.
Key differentiators:
Superior Chemical Stability: Demonstrates excellent resistance to acids, alkalis, peroxides, and perborates, ensuring consistent whitening performance across demanding processing conditions.
Versatile Application Compatibility: Suitable for exhaust dyeing, padding, oxygen bleaching, and one-bath whitening processes across a wide pH range (4.5-11) .
Excellent Lightfastness: Maintains whitening effect under sunlight exposure (rated 3-4), ensuring long-lasting brightness for end-use products .
High Wash Fastness: Rated 4-5 for 95°C machine washing, guaranteeing durability through repeated laundering cycles .
Our Optical Brightener 4BK is manufactured under strict quality controls with ≥98.5% purity and consistent batch-to-batch performance, meeting the demanding requirements of modern textile and paper applications .
2.Product Specifications (Technical Data Sheet)
| Property | Specification | Insight |
| Product Name | Optical Brightener 4BK (Fluorescent Brightener 113) | Premium anionic brightener for cellulose fibers |
| Appearance | Light yellow to greyish-white uniform powder | Free-flowing, fine powder with excellent dispersion |
| Color Tone | Blue-purple to bluish | Produces clean, bright white appearance |
| CAS No. | 12768-92-2 | Verified chemical registry number |
| EINECS/EC No. | 249-323-0 | Listed in European inventory |
| Molecular Formula | C₄₀H₄₀N₁₂Na₂O₁₆S₄ | Disulfonic stilbene structure |
| Formula Weight | 960.94 - 1165.05 g/mol | Varies by hydration state |
| Solubility | Readily soluble in water | Rapid dissolution for easy processing; prepare fresh solution |
| Ionic Style | Anionic | Compatible with anionic and nonionic auxiliaries |
| Fluorescence Intensity | 100% ± 1% (vs. standard) | Consistent whitening efficacy batch to batch |
| Purity | ≥ 98.5% - 99.5% | High purity ensures consistent performance |
| Moisture Content | ≤ 5.0% - 10% | Low moisture ensures stability |
| Water Insolubles | ≤ 0.2% - 0.5% | High purity with minimal residue |
| pH Range | 4.5-11 | Stable performance across broad spectrum |
| Light Fastness | 3-4 (scale 1-8) | Good resistance to UV exposure |
| Wash Fastness (95°C) | 4-5 | Excellent durability through laundering |
| Melting Point | 290-310°C (decomposes) | Excellent thermal stability |
| Storage Conditions | Store in cool, dry, ventilated place; avoid sunlight and moisture | Shelf life: 6-24 months under proper storage |
| Packing | 25 kg fiber drums / cardboard cartons with PE inner liner; 50 kg drums; custom sizes available | Secure, moisture-proof packaging |
| Application | Cotton, viscose, polyester/cotton blends, linen, nylon, paper pulp | Versatile across multiple industries |
3.Product Application
Textile Industry – Primary Application:
Optical Brightener 4BK is the preferred whitening agent for cellulosic fibers and their blends, delivering exceptional performance across various application methods :
| Fiber Type | Application Method | Recommended Dosage | Process Conditions |
| Cotton & Viscose | Exhaust Dyeing | 0.05-0.6% (o.w.f) | 20-100°C, bath ratio 1:10-30, 20-30 min |
| Cotton & Viscose | Oxygen Bleaching | 0.05-0.6% (o.w.f) | 90-100°C, H₂O₂ 2-10 g/L, NaOH 1 g/L |
| Polyester/Cotton Blends | Exhaust Dyeing | 0.15-0.5% (o.w.f) | 90-100°C, bath ratio 1:10-30, 20-30 min |
| Linen & Nylon | Exhaust Dyeing | 0.1-0.5% (o.w.f) | 60-95°C, pH 8-9 optimal |
Paper Industry:
Optical Brightener 4BK is widely used in paper manufacturing for:
Pulp Whitening: Added during stock preparation at 0.1-2% dosage for enhanced paper brightness
Surface Sizing: Combined with CMC, PVA, or starch for uniform whitening
Paper Coating: Provides bright bluish tone with excellent whitening effect
Detergent Industry:
The brightener can be incorporated into laundry detergent formulations for fabric whitening benefits during the wash cycle, with good compatibility with surfactant systems .
4.Storage
This product may be stored up to two years in a sealed container. Containers should be kept tightly closed when not in use and stored in a cool, dry place.
5.Packaging
Usually is 25Kg/drum or paper box or bag with inner double PE liner Or provide customized packaging according to customer requirements.
6.Our advantage
1) Provide free samples for testing or comparing the effect difference and cost performance.
2) Fast response speed, customers' questions at any time will be responded to in two hours.
3) Fast delivery: the fastest delivery can be made on the same day.
4)Different packaging solutions: provide various packaging options according to customer requirements.
5)Technical guidance: provide improved whitening and coloring formulas and guidance according to customer production materials.
6) Sample retention or sample mailing before bulk delivery.
7) Providing certificationes, such as Reach certification.
8) Different payment methods: TT LC, etc.
9) Providing door-to-door DDP service