Cement dispersant, its production process, and cement composition using the cement dispersant
AssigneeNippon Shokubai Co., Ltd.
InventorsTsutomu Yuasa, Noboru Sakamoto, Tsuyoshi Hirata
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Abstract
Disclosed are the following: a cement dispersant which is excellent in initial dispersibility and further in flow retainability of cement, because of using a polymer having a proper molecular weight distribution; a process for producing this cement dispersant; and a cement composition using this cement dispersant. The cement dispersant comprises a water-soluble polymer (P) as a main component, and is characterized by displaying an area proportion (a value (A−B) given by subtracting an area ratio B of a lower molecular weight side portion from an area ratio A of a higher molecular weight side portion) in the range of 13 to 60%.
Claims9
A process for producing a cement dispersant, which is a process for producing a cement dispersant including a water-soluble polymer (P) as a main component,
- with the process comprising the step of polymerizing a monomer component to produce the water-soluble polymer (P) by polymerization, in the presence of a chain transfer agent,
- wherein the step of polymerizing includes the steps of:
- a step of polymerizing a monomer part (M1) of the monomer component, thereby producing polymer units (P1) constituting 60 to 99 mass % of the water-soluble polymer (P), wherein said step of producing polymer units (P1) is carried out by using a fraction (F1) of the chain transfer agent, wherein said fraction (F1) is not less than 80 mass % of the total amount of the chain transfer agent;
- and
- a step of polymerizing a monomer part (M2) of the monomer component, thereby producing polymer units (P2) constituting 1 to 40 mass % of the water-soluble polymer (P), wherein said step of producing polymer units (P2) is carried out by using a fraction (F2) of the chain transfer agent, wherein polymer units (P2) have a higher weight-average molecular weight than polymer units (P1), wherein the step of producing polymer units (P2) is carried out before the step of producing polymer units (P1), and wherein the step of producing polymer units (P2) is carried out by beforehand charging a reactor with the fraction (F2) of the chain transfer agent and no monomer part (M2), and after the reactor is charged, incrementally adding over a period of time the monomer part (M2) to the reactor.
Dependencies are inferred from the claim text.