Agglomerate abrasive grain comprising incorporated hollow microspheres

1. An agglomerate abrasive grain comprising a plurality of individual abrasive grains incorporated into a binding matrix, wherein:

the abrasive grains are selected from the group consisting of corundum, fused corundum, sintered corundum, alumina zirconia, silicon carbide, boron carbide, cubic boron nitride, diamond, and mixtures thereof;

the binding matrix is obtained from a mixture of an aluminosilicate, an alkali sodium silicate, and water;

the aluminosilicate and the alkali sodium silicate having a molar ratio of Al 2 O 3 to SiO 2 ranging from 1:2 to 1:20;

the binding matrix is hardened at temperatures below 500° C.;

the agglomerate abrasive grain has an open porosity ranging from 5% by volume to 25% by volume,

the agglomerate abrasive grain further comprising hollow bodies that are incorporated into the binding matrix and that provide the agglomerate abrasive grain with a closed porosity, wherein

the hollow bodies are 5% to 40% by volume of the agglomerate abrasive grain, and

the sum of closed and open porosity is less than 50% by volume of the agglomerate abrasive grain;

further wherein the abrasive grains and the hollow bodies have an average particle diameter ranging from 5 μm to 250 μm, and wherein the ratio of the average particle diameter of the abrasive grains to the average particle diameter of the hollow bodies ranges from 2:1 to 1:2.

2. The agglomerate abrasive grain according to claim 1 , characterized in that the percentage by volume of the abrasive grains to the percentage by volume of the hollow bodies has a ratio ranging from 9:1 to 1.5:1.

3. The agglomerate abrasive grain according to claim 2 , characterized in that the percentage by volume of the abrasive grains to the percentage by volume of the hollow bodies has a ratio ranging from 6:1 to 2:1.

4. The agglomerate abrasive grain according to claim 1 , characterized in that the agglomerate abrasive grain comprises from 10% by volume to 80% by volume of abrasive grains, from 5% by volume to 40% by volume of hollow bodies, from 5% by volume to 40% by volume of binding matrix, and from 5% by volume to 25% by volume of open pores.

5. The agglomerate abrasive grain according to claim 1 , characterized in that the hollow bodies are selected from the group consisting of hollow bodies on the basis of aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, cerium oxide, and/or mixtures thereof.

6. The agglomerate abrasive grain according to claim 5 , characterized in that the hollow bodies are hollow spheres made of glass.

7. The agglomerate abrasive grain according to claim 1 , characterized in that the agglomerate abrasive grain comprises from 5% by weight to 30% by weight of binding matrix, from 60% by weight to 95% by weight of abrasive grains, and from 0.3% by weight to 20% by weight of hollow bodies.

8. A method for producing agglomerate abrasive grains according to claim 1 , wherein a mixture of individual abrasive grains and hollow bodies are incorporated into a binding matrix of aluminosilicate and alkali sodium silicate having a molar ratio of Al 2 O 3 to SiO 2 ranging from 1:2 to 1:20, the method comprising:

mixing the abrasive grains and hollow bodies with the binding agent of aluminosilicate, alkali sodium silicate, and water,

drying the agglomerate abrasive grain green bodies obtained in this manner at a temperature ranging from 80° to 150° C.;

classifying the dried agglomerate abrasive grain green bodies to a defined abrasive grit size; and

hardening the dried and classified agglomerate abrasive grains at a temperature below 500° C.