Use of polymeric microparticles in building material mixtures
View Patent ↗The use of polymeric microparticles having a cavity in hydraulically setting building material mixtures is described, from 1 to 100% by volume of the cavity of these microparticles being filled with water. In this way, remarkable concrete resistance to the freezing and thawing cycle is achieved, these microparticles providing improved protection for the concrete from the effects of the freezing and thawing cycle, even at a diameter of from 0.1 to 1 μm and in doses which are 1 to 2 orders of magnitude lower than those described in the prior art. Moreover, the compressive strength of the correspondingly hardened concrete is substantially improved, which was likewise not foreseeable.
1. A method comprising adding polymeric microparticles having a cavity therein to a hydraulically setting building mixture, wherein the microparticles consist of polymer particles which contain a polymer core (A) swelled with the aid of an aqueous base and based on an unsaturated carboxylic acid (derivative) monomer, and a polymer shell (B) based on a nonionic ethylenically unsaturated monomer, wherein from 10 to 100% by volume of the cavity of the microparticles are filled with water.
2. The method as claimed in claim 1 , wherein the unsaturated carboxylic acid (derivative) monomers are selected from the group consisting of acrylic acid, methacrylic acid, aleic acid, maleic anhydride, fumaric acid, itaconic acid and crotonic acid.
3. The method as claimed in claim 1 , wherein the nonionic, ethylenically unsaturated monomers are selected from the group consisting of styrene, butadiene, vinyltoluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, acrylamide, methacrylamide, C 1 -C 12 -alkyl esters of acrylic or methacrylic acid.
4. The method as claimed in claim 1 , wherein the microparticles have a polymer content of from 2 to 98% by weight.
5. The method as claimed in claim 1 , wherein the microparticles have a diameter of from 0.1 to 20 μm.
6. The method as claimed in claim 1 , wherein the microparticles contain no surfactants.
7. The method as claimed in claim 1 , wherein the microparticles are used in an amount of from 0.01 to 5% by volume, based on the building material mixture.
8. The method as claimed in claim 1 , wherein the building material mixtures comprise a binder selected from the group consisting of cement, lime, gypsum and anhydrite.
9. The method as claimed in claim 1 , wherein the building material mixtures are concrete or mortar.
10. The method of claim 5 , wherein the microparticles have a diameter of from 0.2 to 20.0 μm.
11. The method of claim 7 , wherein the microparticles are present in an amount of from 0.1 to 0.5% by volume.
12. The method of claim 1 , wherein the microparticles have a diameter of from 0.2 to 20.0 μm.