METHOD FOR INCREASING THE PURITY OF OLIGOSILANES AND OLIGOSILANE COMPOUNDS BY MEANS OF FRACTIONAL CRYSTALLIZATION

Abstract

The invention relates to a method for increasing the purity of oligosilanes and/or oligosilane compounds, in which a first liquid substance mixture formed from at least 50% oligosilane compounds comprising inorganic oligosilanes and/or halogenated oligosilanes and/or organically substituted oligosilanes is provided, and the first liquid substance mixture is subjected to at least one purification sequence, wherein in a first step a) the liquid substance mixture is temperature adjusted to a temperature at which at least one fraction of the oligosilane compounds solidify, and in a second step b) at least one fraction of the liquid substance mixture is separated.

Claims

1. A method for increasing the purity of oligosilanes and/or oligosilane compounds, in which a liquid substance mixture of at least 50% oligosilane compounds, comprising inorganic oligosilanes and/or halogenated oligosilanes and/or organic-substituted oligosilanes is prepared, and the liquid substance mixture undergoes at least one purification sequence, wherein in a first step a) the substance mixture is temperature-adjusted at a temperature at which at least one fraction of the oligosilane compounds solidifies, and in a second step b) at least one fraction of the liquid substance mixture is separated.

2. The method according to claim 1, characterized in that solids formed in step a) are completely separated from the liquid substance mixture in step b).

3. The method according to claim 1, characterized in that in the at least one purification sequence in step b) at least 15% and at most 50% of the liquid substance mixture is separated.

4. The method according to claim 1, characterized in that in at least one further purification sequence at least 10% and at most 80%, preferably 15% to 45% of the liquid substance mixture is separated.

5. The method according to claim 1, characterized in that at least one fraction of the separated liquid substance mixture is added to a further liquid substance mixture in a further purification sequence.

6. The method according to claim 1, characterized in that the liquid substance mixture is pre-distilled to achieve a concentration of the oligosilane compounds.

7. The method according to claim 1, characterized in that solids formed in step a) are separated from the liquid substance mixture through decantation, filtration, and/or centrifugation.

8. The method according to claim 1, characterized in that the temperature is decreased during the temperature adjustment until a crystallization begins and this temperature is then held for a pre-determined time period.

9. The method according to claim 1, characterized in that during the temperature adjustment the liquid substance mixture is agitated, preferably stirred or pumped.

10. The method according to claim 1, characterized in that at least one purification sequence is conducted in a closed reactor system.

11. The method according to claim 1, characterized in that the method is operated under an inert gas.

Description

[0040] The method according to the invention will be explained in more detail by way of example in a figure in the following exemplary embodiment.

[0041] Shown in:

[0042] FIG. 1: A flowchart of an exemplary embodiment of the method according to the invention for increasing the purity of oligosilanes and/or oligosilane compounds

[0043] FIG. 1 shows a flowchart of an exemplary embodiment of the method according to the invention for increasing the purity of oligosilanes and/or oligosilane compounds. According to the exemplary embodiment shown, the process according to the invention can be carried out in batches, wherein, mother liquors ML2 to ML5 separated from a first batch in a purification sequence are added in each case to the liquid substance mixture in the subsequent batch. The first substance mixture is referred to in the present example as a crude mixture. Four batches are shown on the X-axis of Chart A, wherein the number of purification sequences from the 1.sup.st RC to 5.sup.th RC is shown in the direction of the Y-axis. The reference numerals K1 to K5 denote the crystallisates obtained for each of batches 1 to 4, the purity of which increases with a consecutive number.

[0044] According to the exemplary embodiment, each of batches 1 to 4 starts with a raw mixture as the first liquid substance mixture, which is respectively supplied to the first purification sequence 1.sup.st RC. From the second batch 2, at least a fraction of second mother liquor ML2 from the preceding first batch 1 is blended into the first purification sequence 1.sup.st RC and is co-processed. The first purification sequence 1.sup.st RC supplies the first crystallisate K1, which has higher purity than the crude mixture, and the mother liquor ML1, which has a lower purity. The fractions of the first mother liquors ML1 are discharged and treated separately to achieve a purity which corresponds at least to that of the raw mixture. For a second purification sequence 2.sup.nd RC, the first crystallisate K1 is merged with at least one fraction of a third mother liquor ML3 from a previous batch. The crystallisate K2 and the second mother liquor ML2 arise from the second purification sequence 2.sup.nd RC. The crystallisate K2 is combined with at least one fraction of the mother liquor ML4 from a preceding batch for a third purification sequence 3.sup.rd RC. The crystallisate K3 and the third mother liquor ML3 arise from the third purification sequence 3.sup.rd RC. The crystallisate K3 is combined with at least one fraction of the mother liquor ML5 from a preceding batch for a fourth purification sequence 4.sup.th RC. After the fifth purification sequence 5.sup.th RC, the purity of the product is high enough for sale, so the process can be terminated at this point. One skilled in the art will realize that, without departing from the essence of the process according to the invention, fewer or more purification sequences RC can be carried out