Special Polyether Polyols – Flame-Retardant Polyols

Flame-retardant polyether polyols are primarily used to produce flame-retardant polyurethane resin products. There are several types, and the following are some typical examples of flame-retardant polyether polyols.

1. Phosphorus-Containing Polyether Polyols and Phosphorus-Chlorine Polyether Polyols

   Phosphorus-containing polyether polyols are commonly used flame-retardant polyether polyols for rigid foams. They are typically made using phosphorus-based materials such as phosphate esters, phosphorus pentoxide, phosphorus oxychloride, or tetrachlorophosphonium hydroxide. These react with ethylene glycol, glycerin, and similar compounds as initiators, then further react with propylene oxide, ethylene oxide, or epichlorohydrin to produce polyols containing phosphorus (and sometimes chlorine).  

   A specific example is a phosphate ester polyether polyol synthesized in two steps using phosphorus oxychloride, glycerin, and propylene oxide (or epichlorohydrin) in the presence of a catalyst. To reduce the viscosity of this polyether, glycerin can be partially or completely replaced with propylene glycol or diethylene glycol. Substituting glycerin with sorbitol or pentaerythritol increases product viscosity, hydroxyl value, and enhances the thermal stability and dimensional stability of polyurethane products. Another phosphorus-containing flame-retardant polyether can be synthesized by reacting a mixture of phosphoric acid and phosphorus pentoxide with a hydroxyl mixture like ethylene glycol, followed by polymerization with propylene oxide.

2. Halogenated Polyether Polyols  

   In halogen-containing flame-retardant polyols, the halogen mass fraction is generally between 10-20%, and can reach over 30%. Commonly, halogenated alkene oxides like 4,4,4-trichloro-1,2-epoxybutane (TCBO) or 4,4,4-tribromo-1,2-epoxybutane are used as monomers. These react under a Lewis acid catalyst through a ring-opening polymerization to produce chlorine- or bromine-containing polyether polyols.

3. Antimony-Chlorine Polyether Polyols

   Antimony-containing polyether polyols, prepared from halogenated antimony or antimony trioxide reacting with various halogenated or general-purpose polyethers, are high-performance reactive flame retardants with excellent flame-retardant properties.

4. Phosphorus-Antimony-Chlorine Polyether Polyols

   One preparation method involves adding antimony trichloride to glycerin, stirring and heating to 60-70°C until the antimony trichloride dissolves. At 70-80°C, phosphorus oxychloride is gradually added. As the reaction progresses, the material darkens in color. After adding the phosphorus oxychloride, it is kept at 80-90°C for 1 hour, followed by vacuum removal of HCl until the acid value of the material is about 300 mgKOH/g. Epichlorohydrin or propylene oxide is then added, with temperature control at 110-120°C, and the mixture is held for 1-2 hours before vacuum removal of volatiles to yield a low-acidity flame-retardant polyether. Another method synthesizes phosphorus-containing polyether first and then reacts it with antimony trichloride. The latter method, where antimony trichloride is added first, results in better stability, reactivity, and foam quality.  

   Due to the synergy of phosphorus, chlorine, and antimony, polyurethane materials made from these polyethers exhibit excellent flame-retardant performance. Phosphorus and antimony form a dense char layer on the surface during combustion, preventing further burning, while halogenated polyethers release halogenated gases at high temperatures, isolating oxygen from the external air and enhancing flame retardancy.

5. Nitrogen-Containing Soft Foam Flame-Retardant Polyether

   Developed by Jiangyin Youbang Chemical Co., Ltd., this graft-type flame-retardant polyether polyol introduces nitrogen-containing heterocyclic units into high-activity polyether. It does not contain halogen, phosphorus, or antimony; appears as a milky white viscous liquid; has an average particle diameter of 0.2 μm, viscosity around 2000 mPa·s, and low acidity. It can be used in polyether formulations with a shelf life of over six months. Foam products made with it have an oxygen index of 26-28, reaching up to 30, with low odor and smoke density during combustion (≤60%). This polyether is suitable for flame-retardant seating, furniture, and packaging materials.