Abstract: The invention relates to a process for the preparation of a polymer polyol which is at most 60 wt. %, which process comprises mixing a base polyol, one or more ethylenically unsaturated monomers, a polymerization initiator, optionally a macromer, and optionally a chain transfer agent, and polymerizing the mixture thus obtained at a temperature of 50 to 200° C., optionally below 120 C, wherein the initiator is of formula R1—C(?O)—O—O—R2 (I) wherein R1 is an alkyl group and R2 is an alkyl group of formula —C(R3)(R4)—C(R5)(R6)(R7) (II) wherein R3 and R4 are the same or different and are an alkyl group, R5, R6 and R7 are the same or different and are a hydrogen atom or an alkyl group.

Abstract: The invention relates to a process for the preparation of a polymer polyol, which process comprises mixing in a reactor vessel a base polyol, one or more ethylenically unsaturated monomers, a polymerization initiator, optionally a macromer, and optionally a chain transfer agent, and polymerizing the mixture thus obtained at a temperature of 50 to 200 ° C., wherein the monomer(s) and initiator are dosed simultaneously to the reactor vessel and wherein during the time period of simultaneously dosing the monomer(s) and initiator the dosing weight ratio of initiator to monomer(s) is increased.

Abstract: The invention relates to a process for the batch or semi-batch preparation of a polymer polyol, which process involves (1) preparing a seed by polymerizing in a base polyol at least one ethylenically unsaturated monomer in the presence of a polymerization initiator and macromer, and in the presence of from 0.5 to 50% wt of polymer polyol heel, based on amount of polymer present in the heel compared with total amount of polymer formed, (2) adding additional ethylenically unsaturated monomer to the seed obtained in step (1) and optionally additional polyol, and (3) polymerizing the mixture obtained in step (2).

Abstract: The invention relates to a process for the batch or semi-batch preparation of a polymer polyol, which process involves (1) preparing a seed by polymerizing in a base polyol at least one ethylenically unsaturated monomer in the presence of a polymerization initiator and macromer, and in the presence of from 0.5 to 50 % wt of polymer polyol heel, based on amount of polymer present in heel compared with total amount of polymer present, (2) adding additional ethylenically unsaturated monomer to the seed obtained in step (1) and optionally additional polyol, and polymerizing the mixture obtained in step (2).