초록 ▼

Polymers with a high glass transition temperature are used in cement additives to produce a portland cement mortar or concrete that does not have the initial stickiness typical of prior art polymer-modified portland cement compositions and does not form a crust on the surface when exposed to air dry

Polymers with a high glass transition temperature are used in cement additives to produce a portland cement mortar or concrete that does not have the initial stickiness typical of prior art polymer-modified portland cement compositions and does not form a crust on the surface when exposed to air drying, thus improving the working time of the mix. This simplifies equipment cleaning and permits the use of transit mixers for field applications of polymer-modified concrete. The properties of the mortar and concrete modified with these materials, both in the plastic and hardened state, are equivalent or superior to those of the currently available products which use film-forming materials. Within the scope of this invention are a redispersible powdered cement additive, a redispersible polymer powder and a ready-to-use portland cement composition, as well as related processes.

대표청구항 ▼

A cement additive comprising: (A) from about 70 to about 99 parts by weight of a polymer characterized by a Tg greater than 100°C., the polymer produced by polymerizing a polymerization mixture which contains monomers consisting essentially of one or more monomers selected from mono-unsaturated arom

A cement additive comprising: (A) from about 70 to about 99 parts by weight of a polymer characterized by a Tg greater than 100°C., the polymer produced by polymerizing a polymerization mixture which contains monomers consisting essentially of one or more monomers selected from mono-unsaturated aromatic monomers, aliphatic conjugated diene monomers, esters of (meth)acrylic acid monomers, and monoethylenically unsaturated carboxylic acid monomers including the anhydrides, esters, amides and imides thereof; and, based on 100 parts of the polymer solids, (B) from about 1 to about 15 parts by weight of a stabilizer, and, (C) up to about 15 parts by weight of a foam depressant; or (A) from about 70 to about 99 parts by a Tg weight of a polymer characterized by greater than 1000°C., polymer produced by polymerizing a polymerization mixture which contains monomers comprising one or more monomers selected from mono-unsaturated aromatic monomers, aliphatic conjugated diene monomers, esters of (meth)acrylic acid monomers, and monoethylenically unsaturated carboxylic acid monomers including the anhydrides, esters, amides and imides thereof; and, based on 100 parts of the polymer solids, (B) from about 1 to about 15 parts by weight of a stabilizer, and, (C) up to about 15 parts by weight of a foam depressant.