Comb polymers as blocking additives for swelling clays

Abstract

A comb polymer, in particular for use as a clay-inerting agent, including: a) at least one poly(alkylene oxide) side chain-bearing monomer unit M1 without ionic groups, b) optionally at least one cationic monomer unit MC, c) optionally at least one anionic monomer unit MA, d) optionally, at least one non-ionic monomer unit M3, wherein the molar ratio of the cationic monomer units MC to the side chain-bearing monomer units M1 is equal to or less than 10, the molar ratio of the anionic monomer units MA to the side chain-bearing monomer units M1 is less than 1, preferably equal to or less than 0.5, and the molar ratio of the non-ionic monomer units M3 to the side chain-bearing monomer units M1 is less than 5.

Description

TECHNICAL FIELD[0001]The invention relates to a comb polymer, in particular for use as a clay-inerting agent. Additionally, the invention is concerned with a kit of parts and a composition comprising the comb polymer. Further aspects of the invention are related to a method, in particular for plasticizing a mineral binder composition, as well as a use of a comb polymer as a clay-inerting agent.BACKGROUND ART[0002]Dispersants or superplasticizers are used in the building industry as plasticizers or water-reducing agents for mineral binder compositions, such as for example concrete, cement mortar, plaster or lime mortar. The dispersants are generally organic polymers which are added to the mixing water or admixed with the binder compositions in solid form. In this way, it is advantageously possible to alter both, the consistency of the binder composition during processing and the properties in the hardened state.[0003]Known particularly effective dispersants are, for example, polymers...

AI Technical Summary

Benefits of technology

[0021]As has been shown, the inventive comb polymers allow for a highly efficient reduction of the negative influence of swelling clays on the effectiveness of dispersants, in particular of PCE-based dispersants, in mineral binder compositions containing swelling clays. Thereby, the inventive solution turned out to be highly robust and the comb polymers only have little effect on the flowability of mineral binder compositions. Specifically, the dosage of the comb polymer according to the invention is rather uncritical, especially if a certain threshold has been reached. Therefore, fluctuating contents of swelling clays in mineral binder compositions are much less of an issue with the inventive comb polymers. Thus, the comb polymers according to the invention can be used as clay-inerting or clay-blocking agents, especially in combination with PCE-based dispersants.

[0024]Moreover, the inventive comb polymers turned out to be at least as efficient as known blocking additives such as polycations or like known blocking additives having a strong plasticizing effect.

[0038]The terms “clay-inerting agent”, “clay-blocking agent” and “clay blocker” are meant to be agents capable of reducing or inhibiting adverse effects of swellable clays on the effectiveness of dispersants, in particular of PCE-based dispersants, in mineral binder compositions.

Problems solved by technology

High quality river sands, which are typically used as aggregates for mortar or concrete production, are increasingly becoming a scarce resource.

Unfortunately, the presence of certain contaminants, such as e.g. swelling clays, even in very low amounts, has a huge impact on the effectiveness of PCE-based admixtures in mortar or concrete production.

This is because PCEs intercalate in swelling clays and, thus, a significant proportion of the added PCEs is lost and cannot adsorb anymore on cement or cement hydrates so that the desired water-reducing effect cannot be achieved.

Although increasing the PCE dosage is in principle a straightforward solution, it is economically inefficient and can be problematic if the swelling clay content is fluctuating.

In this case, the concrete producer is constantly forced to adjust the PCE dosage in order to keep a certain flowability, which is highly time-consuming.

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