SYNTECH

1. Product Basic Info

• Chemical Name: Sodium 2-methylprop-2-ene-1-sulfonate (SMAS)
• CAS: 1561-92-8 | Molecular Formula: C4​H7​NaO3​S
• Industrial Grade: 99.5% high-purity white crystalline powder, specially matched for wet-spun PAN acrylic fiber terpolymerization

2. Core Mechanism to Upgrade Dyeing Capacity

Pure polyacrylonitrile (PAN) has tight ordered molecular chains, high crystallinity and no ionic binding sites, leading to low cationic dye uptake, uneven shade and poor color fastness. SMAS solves this fundamentally as third monomer:

1. Introduce fixed anionic sulfonate binding sitesThe −SO3​Na group covalently grafted onto PAN main chain provides abundant negative charges, forming stable ionic bonds with positively charged cationic dyes, greatly lifting dye adsorption capacity and saturation dye uptake.
2. Break polymer regular arrangement & expand amorphous regionsMethyl branched side chain disrupts dense PAN crystal stacking, creating more loose amorphous channels inside fiber. Dye molecules diffuse faster into fiber interior for full, uniform coloring, eliminating color streaks and shallow shade defects.
3. Methyl steric hindrance ensures stable polymerizationCompared with Sodium Allyl Sulfonate (SAS), the methyl group suppresses excessive self-crosslinking/gelation during fiber polymerization, avoids unstable polymer viscosity and batch-to-batch dye difference. Fiber internal structure stays consistent for steady dyeing performance mass production.

3. Dyeing Performance Improvements

• Fast dye absorption: Shorten dyeing time, lower dye bath temperature & energy consumption
• Higher color saturation: Brighter, fuller shade with less dye consumption
• Superior color fastness: Better washing, rubbing and light fastness, less fading
• Uniform dyeing: Consistent shade for thick yarn, staple fiber and bulk acrylic fabrics
• Extra fiber upgrades: Improve heat resistance, soft hand feel and weaving processability, reduce broken yarn rate during spinning

4. Standard Industrial Addition Dosage

• Proportion in total monomer system: 1.5–4.0 mol%
• Light-color acrylic yarn: 1.5–2.5 mol% SMAS
• Deep-color high-saturation fiber: 2.5–4.0 mol% SMAS
• Overdosage risk: Excessive sulfonate groups increase fiber hydrophilicity, reduce dry strength and dimensional stability

5. Why 99.5% High-Purity SMAS Powder Is Mandatory

• Ultra-low chloride, sulfite and dimer impurities prevent catalyst poisoning during PAN polymerization
• No extra water introduced into polymerization reactor, precise control of spinning dope concentration
• Low freight cost for large-batch textile factory procurement, 24-month sealed shelf life without deterioration
• Uniform crystal dissolves fully in spinning stock solution, no insoluble particles causing fiber defects or dye spots

6. Auxiliary Extra Benefits Beyond Dyeing

1. Moderate chain transfer activity regulates PAN molecular weight, optimizes fiber tensile strength and elasticity
2. Improve fiber anti-static property from permanent sulfonate hydrophilic groups
3. Enhance thermal stability of acrylic fiber, reduce yellowing under high-temperature setting