Abstract: An anti-blocking agent comprising silicon dioxide or mixtures of silicon dioxide and zeolite is described, which is characterized in that it has a bimodal pore size distribution, the first maximum of the bimodal pore size distribution being in the pore size range <5 nm and the second maximum of the bimodal pore size distribution in the pore size range >6 nm. The anti-blocking agent is obtainable by micronizing a mixture comprising silicon dioxide of a certain pore size and silicon dioxide and/or zeolite having a different pore size. It can be produced together with lubricating agent as a combined anti-blocking and lubricating agent. Incorporation of the anti-blocking agent or of the combined anti-blocking agent and lubricating agent into a polymer in the form of a master batch is preferable.

Abstract: The use of a composition based on silicon dioxide as antiblocking agent is described which is characterized in that it has silicon dioxide having a particle size of 2 to 8 .mu.m, a specific surface of 150 to 850 m.sup.2 /g and a specific pore volume of 1.4 to 2.0 ml/g which has been treated with polyol. This silicon dioxide can be used together with a slip agent as combined antiblocking agent and slip agent. The working-in of the antiblocking agent or of the combined antiblocking agent and slip agent into a polymer is preferably in the form of a masterbatch. A preferred antiblocking agent contains as polyol ethoxylated pentaerythritol in which the pentaerythritol/ethoxy ratio lies in the range from 1:0.5 to 1:25. The antiblocking agent can be obtained by micronizing silicon dioxide to the given particle size and impregnating it with the polyol.

Abstract: A modified amorphous silica is described which, apart from optionally present usual additives, comprises 40 to 85 wt-% silica and 60 to 15 wt-% paraffin, silicone or vegetable oil and/or ethylene glycol. The modified amorphous silica is prepared by bringing together, apart from optionally present usual additives, silica with such a quantity of paraffin, silicone or vegetable oil and/or ethylene glycol that the finished, modified silica has a paraffin, silicone or vegetable oil and/or ethylene glycol content of 60 to 15 wt-%. The modified amorphous silica is suitable as an anti-blocking agent, which can be advantageously prepared as concentrate (masterbatch). Surprisingly, upon preparing such a concentrate the melt-flow index hardly falls compared with the melt-flow index of the polyolefin which forms the basis of the concentrate. Thus it is possible to incorporate large quantities of the modified silica into the concentrate in very homogeneous distribution.

Abstract: Combined antiblocking agent and lubricant concentrate based on polyolefin, which contains diatomaceous earth, precipitated silica and/or silica gel as the antiblocking agent, one or more amides of unsaturated C.sub.18 -C.sub.22 -fatty acids and optionally further conventional additives and which is characterized in that it contains 5 to 35% by weight of antiblocking agent and 5 to 30% by weight of lubricant. The high lubricant concentration in the combination concentrate according to the invention is obtained in that the antiblocking agent and the lubricant are incorporated into the polyolefin in the form of a homogeneous, finely divided mixture. The antiblocking agent serves as a carrier for the micronized lubricant, i.e. the lubricant is adsorbed on the large surface of the antiblocking agent, so that the "flowing away" of the lubricant otherwise observed in the case of high lubricant concentrations during incorporation into the polyolefin is avoided.