Halogenated Phosphate Ester Flame Retardants - Halogenated Polyphosphate Esters

Chlorinated phosphate esters such as TCEP and TCPP, due to their low molecular weight, tend to volatilize slowly over time. To address this, many manufacturers and researchers have developed dimeric and polymeric halogenated phosphate esters. For applications requiring reduced long-term volatilization loss in foamed plastics, higher molecular weight halogenated polyphosphate esters are preferred.

(1) Tetra(2-chloroethyl) Ethylene Diphosphate

Tetra(2-chloroethyl) ethylene diphosphate, also known as 1,2-ethylene-tetra(2-chloroethyl) diphosphate, is a dimeric phosphate ester. It has a molecular weight of 472, with a phosphorus content of approximately 13.1% and a chlorine content of about 30.5%. Marketed by Olin Corporation under the brand name Thermolin 101, it is also produced domestically. As a low-volatility, durable flame retardant, it is widely used in flexible and rigid polyurethane foams for automotive interiors.

(2) Tetra(2-chloroethyl) Diethylene Glycol Ether Diphosphate

Tetra(2-chloroethyl) diethylene glycol ether diphosphate was one of the earliest developed polymeric phosphate esters. With a viscosity of 200–500 mPa·s, it exhibits excellent processability. It has a molecular weight of 516, a phosphorus content of approximately 12%, and a chlorine content of 27.0%–27.5%. Produced under the brand name CR-505 by Japan's Daihachi Chemical Industry, it is also available domestically. Primarily used in flexible polyurethane foam, this flame retardant features high molecular weight, low migration, and long-lasting flame-retardant properties. It also has low viscosity, good compatibility with polyurethane raw materials, and prevents foam scorching. Adding 8–10 parts of this product per 100 parts of polyether in foam formulations achieves self-extinguishing properties.

Tetra(2-chloroethyl)-2,2-dichloromethyl-1,3-propylene Diphosphate

This is a high-chlorine-content dimeric chlorophosphate ester with a molecular weight of 583, a phosphorus content of approximately 10.6%–10.8%, and a chlorine content of about 35.5%–36.5%. It has a density of 1.47–1.50 g/cm³ (at 25°C) and a viscosity of approximately 2200 mPa·s (at 25°C), with an acid value ≤0.3 mg KOH/g. This high-molecular-weight flame retardant is suitable for flexible polyurethane foam, particularly in automotive interiors and furniture applications.

Tetra(2-chloroethyl)-2,2-dibromomethyl-1,3-propylene diphosphate shares a similar chemical structure with tetra(2-chloroethyl)-2,2-dichloromethyl-1,3-propylene diphosphate, containing phosphorus, chlorine, and bromine.

Related Compounds

Phosgard C-22-R has a phosphorus content of 15% and a chlorine content of 27%, with a relative density of 1.492–1.496, a freezing point of 5°C, and decomposition at 300°C, releasing gas. Among phosphorus-chlorine flame retardants, it has the highest phosphorus content, offering excellent flame-retardant performance and durability.

Another high-molecular-weight flame retardant for flexible polyurethane foam, FR-V6, has a phosphorus content of 10.3% and a chlorine content of 36.5%. It exhibits good thermal stability, long-lasting flame-retardant performance, and can prevent scorching. Several manufacturers in Chun’an, Zhejiang Province, produce this product.