In-depth Analysis｜CAS 2149581-44-0 Polymerizable Benzophenone Photoinitiator Monomer: Core Low-Migration UV Curing Material

As the UV curing industry marches toward comprehensive upgrades featuring migration-free, low-odor, high-safety and environmentally compliant solutions, pain points of conventional small-molecule photoinitiators including migration and exudation, residual volatilization, film yellowing and failure to meet food safety standards have long restricted quality improvement and market compliance in food-contact packaging, medical consumables, precision electronic coatings, high-end cosmetic finishing and other fields. To tackle these core industry challenges, a new-generation polymerizable Type II benzophenone photoinitiator monomer (CAS: 2149581-44-0, 2-(2-(4-benzoylphenoxy)ethoxy)ethyl methacrylate) has undergone process optimization. With its unique molecular structure design, it fundamentally addresses the inherent drawbacks of traditional photoinitiators, serving as a core upgraded raw material for high-end UV curing systems and delivering a brand-new solution for the compliant and high-end development of the industry.

1. Basic Product Information and Physicochemical Properties

This product is a hydrogen-abstraction Type II photoinitiator monomer. Its molecule integrates both benzophenone photosensitive groups and polymerizable methacrylate double bonds, possessing both photoinitiation activity and monomer copolymerization capacity.

• CAS No.: 2149581-44-0
• Chinese Name: 2-[2-(4-benzoylphenoxy)ethoxy]ethyl methacrylate
• English Name: 2-(2-(4-benzoylphenoxy)ethoxy)ethyl methacrylate
• Molecular Formula: C₂₁H₂₂O₅
• Molecular Weight: 354.40
• Appearance: Off-white solid
• Purity: ≥98.0% (HPLC)
• Water Content: ≤0.3%
• Melting Point: Approx. 46–50℃
• Solubility: Readily soluble in acrylate monomers, reactive diluents and common UV resins; slightly soluble in water
• Storage Stability: Store sealed and protected from light at ambient temperature; low tendency of self-polymerization; a small amount of polymerization inhibitor is recommended.

2. Molecular Mechanism of Action

Conventional benzophenone photoinitiators only contain photosensitive groups. Upon UV excitation, they abstract hydrogen from hydrogen donors to generate free radicals. After curing, small-molecule photoinitiators remain free inside the film network, prone to outward migration, extraction and volatilization, resulting in odor and exudation contamination. A methacrylate double bond is introduced into the molecular structure of this product. Under UV irradiation, the benzophenone group gets excited and undergoes hydrogen abstraction reaction with tertiary amine hydrogen donors in the system to produce free radicals for initiating polymerization of acrylic systems. Meanwhile, the intrinsic acrylic double bond of the molecule participates in crosslinking reactions and covalently bonds directly into the three-dimensional polymer network. After curing, the photosensitive unit is firmly locked within the film backbone instead of existing as free small molecules, which greatly reduces risks of migration, leaching and volatilization and achieves cured films with low extractables and low odor.

Note: This product belongs to Type II photoinitiating system with limited initiation efficiency when used alone. Tertiary amine co-initiators (hydrogen donors) shall be added into formulations for synergistic application.

3. Core Product Advantages

1. Extremely low migration and exudation: It can copolymerize and bond into the coating film, greatly reducing residual leaching of photoinitiators after curing and meeting strict extractables control requirements for food-contact and medical products.

2. Low odor performance: No free small molecules volatilize after curing, and the odor of finished films is far lower than that of conventional small-molecule photoinitiators such as benzophenone (BP) and 4-benzoylbenzoic acid.

3. Excellent formulation compatibility: Its flexible ether linkage structure provides good miscibility with epoxy acrylate, polyurethane acrylate, polyester acrylate resins and various reactive diluents with low risk of crystalline precipitation.

4. Balanced comprehensive curing performance: It retains the photoreaction characteristics of benzophenone systems with good surface cure, minor impact on substrate adhesion and stable mechanical strength of coating films.

5. Wide applicable wavelength range: Its UV absorption band matches conventional mercury lamps and LED UV light sources, compatible with most existing UV production lines without large-scale equipment modification.

6. Reduced yellowing risk: Compared with some highly active cleavable Type I photoinitiators, yellowing upon long-term aging is relatively controllable, suitable for light-colored and transparent coating systems.

4. Application Fields and Formulation Guidelines

Applicable Scenarios

• UV printing inks, water-based/solvent-based overprint varnishes, flexible packaging composite inks (preferred for food packaging applications)
• UV protective coatings for electronics industry, auxiliary solder mask resins for FPC, insulating UV-curable layers for precision components
• UV pressure-sensitive adhesives, optical adhesives, structural UV-curable adhesives
• SLA UV-curable 3D printing resins, transparent photosensitive resins
• Medical-grade UV-curable consumables, photocrosslinkable hydrogels
• UV topcoats for paper, plastic and metal substrates

Usage Recommendations

• Dosage: Recommended loading 2–6 wt% in conventional formulations, fine-tuned according to film thickness, light source and curing speed requirements.
• Supporting additives: Use with tertiary amine co-initiators such as methyldiethanolamine and acrylated amine co-initiators. Polymerizable amine co-initiators are preferred to further reduce overall migration.
• Formulation note: Avoid high levels of alkaline impurities in the system; keep away from light throughout storage and production.

5. Differences Compared with Conventional Photoinitiators

BP (Benzophenone): Small molecule, highly prone to migration after curing, strong odor, restricted for food contact; this product is copolymerizable with low migration.

4-BPB (4-Benzoylbenzoic acid): Relatively high polarity and poor compatibility in some systems; this product contains flexible ether chains for better compatibility.

Competing polymerizable BP products: Some have low purity and high impurities; this product features ≥98% purity and excellent batch stability.

6. Packaging, Storage, Transportation and Safety Instructions

Packaging: 25kg fiber drum with double inner PE bags. Small packages (100g/500g) are available for formulation evaluation.

Storage & transport: Store in cool, dry and dark place, away from heat sources and oxidants. Avoid direct sunlight to prevent premature self-polymerization.

Safety notice: Wear goggles and protective gloves during handling; avoid dust inhalation. Rinse with clean water upon skin contact. It is a general chemical raw material, non-hazardous.

7. Supply Information

Samples and pilot trial batches of this polymerizable benzophenone photoinitiator monomer are available. The technical team can provide formulation support to assist customers with curing tests and migration assessment, helping UV material enterprises comply with domestic and overseas environmental regulations for food-contact, medical and electronic materials and achieve product upgrading.