one. Pretreatment of raw materials: In the ring-opening polymerization reaction, in order to ensure the reaction speed and molecular weight control of Poloxamer 188 synthesis, as well as the color and unsaturation of the product, the polymerization monomer should be purified first, and the catalyst and initiator should also be removed Trace impurities such as water, aldehydes, oxygen, and polyhydroxy sugars are brought into the same reaction system.
2. Ring-opening polymerization reaction: The ring-opening polymerization reaction with epoxy as raw material is an exothermic reaction, so condensed water is used to remove the heat of reaction in time during the reaction process. In addition, oxygen will oxidize and inhibit the polymerization reaction, so the air in the reactor must be exhausted with a vacuum pump before the reaction to ensure that the reaction is carried out in the absence of oxygen. At the same time, in the process of the reaction, also Vacuuming should be done continuously so that high quality Poloxamer 188 can be produced.
3. Post-treatment process: The crude Poloxamer 188 produced by the polymerization reaction must be post-processed. Post-processing work mainly includes neutralization, adsorption, dehydration, filtration, rectification and other units. Poloxamer 188 undergoes a series of post-treatments, not only to neutralize and filter out the remaining catalyst impurities, but also to remove other harmful impurities through adsorption, dehydration and distillation processes to obtain low water content, light color and no peculiar smell , Good performance, uniform polyether products. The basic refining methods can be roughly divided into the following categories:
(1) Use inorganic acid or organic acid to neutralize in the polymerization reaction of producing Poloxamer 188. For systems that use alkaline metal hydroxides as catalysts (such as calcium hydroxide, barium hydroxide, strontium hydroxide, etc.), inorganic acids are rarely used as neutralizers during neutralization. For the use of alkali metal hydroxides as catalyst systems. It is recommended to use inorganic acids as neutralizers, such as hydrochloric acid, phosphoric acid, dilute sulfuric acid, etc.
(2) Adsorption, the adsorption operation is to remove residual catalyst plasma and colored substances in Poloxamer 188. Commonly used adsorbents include magnesium silicate, aluminum silicate, activated clay, activated carbon, molecular sieve, diatomaceous earth, medium charcoal, etc., therefore, The adsorption operation temperature is generally around 100°C.
(3) Ion exchange. In industrial production, the neutralization adsorption method is often used, but the special polyether with high requirements can also be treated by the ion exchange method. This method can not only effectively remove the metal ions in Poloxamer 188, but also It can also remove colored and toxic substances in polyether.
(4) Filtration. The purpose of filtration is to remove the salt generated after the catalyst is neutralized. Now most of the advanced rotary screen filter equipment is used. during the filtering process. According to the molecular weight and functionality of the polyether produced, suitable filter aids should be added appropriately to reduce the viscosity of the system material, improve the filtration efficiency and reduce the residual amount of the product in the filter cake.
(5) Rectification and adjustment. In order to obtain polyether products with low impurity content, light color and relatively narrow molecular weight distribution, rectification and adjustment procedures are also required. The rectification of polyether is carried out under reduced pressure at about 100°C, using a falling film evaporator, adding 0.05%-0.5% di-tert-butyl p-cresol and other antioxidants, as well as butylated hydroxytoluene and Complexes such as amine antioxidants (such as phenothiazine, etc.), remove trace moisture and other impurities in polyether.
