Method for preparing ultra-pure organoalkoxyhydrogensilanes

Abstract

The invention relates to a method for preparing an organoalkoxyhydrogensilane of general formula (I) having a boron content of at most 100 ppb R1 xHySi (OR2)z (I), wherein: in a first step, at least one boron-contaminated organohalogenhydrogensilane of general formula (II) R1 xHySiHalz (II) is reacted with at least one alcohol R2–OH in the presence of ≥1 equivalent of urea, i.e. at least the equivalent amount of urea relative to the halogen content of the contaminated organohalogenhydrogensilane of general formula (II), and in the presence of at least one organic solvent, and then the organic lower phase is separated, the crude product in the upper phase containing 10 to 2000 [ppm] hydrogen chloride; and, in a second step, the obtained crude product from the upper phase is mixed with 0.5 to 5 wt.% N-methylglucamine, relative to the total mass of the crude product and N-methylglucamine, and boiled under reflux in a protective atmosphere for between 10 minutes and 2 hours, and then the organoalkoxyhydrogensilane of general formula (I) is distilled off under a protective atmosphere.

Description

[0001] Process for the preparation of ultrapure organoalkoxyhydrogen si 1 anes

[0002] The invention relates to a process for the preparation of ultrapure organoalkoxyhydrogensilanes.

[0003] Due to their manufacturing process, organohalohydrosilanes contain boron impurities, which are harmful to electronic components. Ultrapure organohalohydrosilanes are required for these semiconductor applications.

[0004] Methods for boron depletion by adding various compounds have long been described in the prior art. For example, US2012095248A (= equivalent to DE102009027257A1) discloses a process for producing organoalkoxyhydrosilanes with a boron content of less than 100 ppb. For boron depletion, the first step consists in pretreating the boron-contaminated reactant with silicic acid or aluminosilicate. The silicic acid or aluminosilicate is separated from the organohalohydrosilane in a second step, and the organohalohydrosilane thus prepurified is then reacted with alcohol in a third step. Due to the high flammability of the reactant, it is very desirable from a safety perspective to forgo such prepurification.

[0005] The object of the invention is to improve the state of the art and in particular to provide organoalkoxyhydrogensilanes which contain as little boron as possible.

[0006] The present invention relates to a process for the preparation of an organoalkoxyhydrogensilane of the general formula ( I ) with a boron content of at most 100 ppb

[0007] RixHySi ( OR 2 ) ( I ) where x+y+z = 4 and x, y, z greater than or equal to 1, wherein in a first step at least one boron-contaminated organohalohydrogensilane of the general formula (II)

[0008] R 1 xH y SiHal z (II) where x+y+z = 4, x, y, z is greater than or equal to 1, and

[0009] R 1 are linear or branched alkyl, cycloalkyl, aryl, alkenyl or arylalkyl radicals having 1 to 12 carbon atoms and Hal is F, Cl, Br or I, with at least one alcohol R 2 -OH where R 2Methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert. -butyl, n-pentyl, isopentyl, neo-pentyl or tert. -pentyl radical, in the presence of > 1z equivalents of urea, i.e. at least the equivalent amount of urea based on the Hal amount of the contaminated organohalohydrogensilane of the general formula (II), and in the presence of at least one organic solvent, and then the organic lower phase is separated off, the crude product of the upper phase containing 10 to 2000 [ppm] of hydrogen chloride, and in a second step the crude product obtained from the upper phase with 0.5 to 5 wt. -% N-methylglucamine is added, based on the total mass of crude product and N-methylglucamine, and boiled under reflux in a protective atmosphere for between 10 minutes and 2 hours, and then the organoalkoxyhydrogensilane of the general formula (I) is distilled off under a protective atmosphere.

[0010] In order to avoid making the number of pages of the description of the present invention too extensive, only the preferred embodiments of the individual features are listed below.

[0011] However, the knowledgeable reader should understand this type of disclosure to mean that every combination of different levels of preference is explicitly disclosed and explicitly desired.

[0012] Organoalkoxyhydrogensilane of the general formula ( I )

[0013] Of the organoalkoxyhydrogensilanes of the general formula ( I ) , alkylalkoxyhydrogensilanes are preferred and of the alkylalkoxyhydrogensilanes , dimethoxymethylsilane and diethoxymethylsilane are preferred , diethoxymethylsilane being particularly preferred .

[0014] First procedural step

[0015] Boron-contaminated organohalohydrosilane of the general formula ( II )

[0016] The radicals R^ preferably have 1 to 6 carbon atoms. Particularly preferred radicals R^ are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl or tert-pentyl radicals and phenyl radicals.

[0017] Alcohol R 2 -OH Of the alcohols R 2 -OH are preferred where Methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert.-butyl, n-pentyl, iso-pentyl, neo-pentyl or tert.-pentyl radical and phenyl radical, particularly preferred are those with the methyl, ethyl, butyl, n-propyl, iso-propyl radical.

[0018] The lower amount of alcohol results from the stoichiometry, ie, 2 mol of alcohol per mol of organohalohydrosilane of general formula (II). A 50% molar excess is preferred, and a 30% molar excess is particularly preferred.

[0019] Organic solvent

[0020] As solvents, known organic solvents can be used which differ from the alcohol R 2 -OH. Suitable solvents include, for example, aliphatic solvents such as isohexane, pentane, octane, decane, and aromatic solvents such as toluene and xylene. Isohexane, pentane, and decane are preferably used in the process according to the invention, with isohexane being particularly preferred.

[0021] Preference is given to the same molar amounts of organic solvent as the amounts of organohalohydrosilane of the general formula (II), particularly preferably between 0.6 and 1 mol of organic solvent per mol of organohalohydrosilane of the general formula (II).

[0022] Non-polar organic solvents are particularly preferred to reduce the solubility of hydrochlorides.

[0023] Acid scavenger urea. It has unexpectedly been shown that it is essential to the invention that the amount of urea used (which acts as an acid scavenger) be > 12 equivalents of urea, i.e., at least the equivalent amount of urea based on the amount of Hal in the contaminated organohalohydrosilane of general formula (II). This leads to an unexpectedly significantly higher product yield, which simultaneously also means less waste. Furthermore, it also leads to a lower HCl load.

[0024] Preferably, at least 1.1z to 1.5z equivalents of urea are used.

[0025] The resulting crude product in the upper phase is slightly acidic because it contains residues of hydrogen chloride in the range of 10 to 2000 [ppm], preferably 50 to 1000 [ppm] hydrogen chloride, and particularly preferably 200 to 800 [ppm] hydrogen chloride.

[0026] Second procedural step

[0027] Basic sugar N-methylglucamine

[0028] Another key feature of the invention is the use of the slightly basic sugar N-methylglucamine. Firstly, the hydrogen chloride present in the crude product is neutralized, and secondly, heating under reflux in a protective atmosphere forms a complex of this sugar and the boron species present as an impurity, which remains almost quantitatively in the bottoms during the subsequent distillation. Typically, 0.5 to 5 wt.% N-methylglucamine, preferably 1 to 5 wt.%, particularly preferably 2 to 5 wt.%, is used, based on the total mass of crude product plus N-methylglucamine.

[0029] Refluxing in a protective atmosphere takes place in the second step for between 10 minutes and 2 hours. The process according to the invention thus offers significant advantages over the prior art, such as significant time savings in the preparation of organoalkoxyhydrosilanes of general formula (I), in particular diethoxymethylsilane, while simultaneously increasing yield and reducing waste. The process according to the invention allows for the preparatively undemanding, clean, and virtually safe depletion of boron species from silanes.

[0030] Examples

[0031] The following examples describe the basic feasibility of the present invention, without, however, limiting it to the contents disclosed therein.

[0032] In the following examples, all parts and percentages are by weight unless otherwise stated. Unless otherwise stated, the following examples are carried out at ambient atmospheric pressure, i.e., approximately 1000 hPa, and at room temperature, i.e., approximately 20 °C or a temperature that occurs when the reactants combine at room temperature without additional heating or cooling.

[0033] Abbreviations used n . b . = not determined GC = Gas Chromatography EtOH = Ethanol

[0034] HM-Silane = Dichloromethylsilane

[0035] M2E = Methyldiethoxysilane

[0036] M3E = Methyltriethoxysilane wt% weight-%

[0037] Standards and measurement methods

[0038] N content

[0039] The NSX-2100H nitrogen analyzer from al Enviroscience was used to determine nitrogen levels. The sample substance is pyrolyzed in an argon or oxygen stream at 1000°C. After passing through a nickel catalyst, the nitrogen is then oxidized with ozone to nitrogen dioxide. The resulting energy is then detected by chemiluminescence. The software used to evaluate the results is the software provided by the device manufacturer.

[0040] Chlorine content

[0041] To determine the chlorine content, a combustion ion chromatograph was used. This chromatograph consists of an HF-210 oven (al enviroscience), a GA-210 preparation unit (al enviroscience), and an IC Aquion (Thermo Fisher). The sample substance is pyrolyzed in an argon or oxygen stream and then introduced into distilled water. The halogen species are then determined by ion chromatography. The determination is based on ISO 11885 "Water quality - Determination of selected elements by inductively coupled plasma atomic emission spectrometry (ICP-OES) (ISO 1185:2007), German version EN ISO 11885:2009," which is used to analyze acidic, aqueous solutions (e.g., acidified drinking water, wastewater, and other water samples, aqua regia extracts from soils and sediments). The software used to evaluate the results is that supplied by the device manufacturer.

[0042] To determine the boron content, a microwave digestion system NSX-2100H (MWS) and an ICP-MS Nexion 350S (Perkin Elmer) were used in a clean room atmosphere. The sample is digested with nitric acid and hydrofluoric acid and then fed into the MS using ammonia via TCP. The determination is based on ISO 11885 "Water quality - Determination of selected elements by inductively coupled plasma atomic emission spectrometry (ICP-OES) (ISO 1185:2007), German version EN ISO 11885:2009", which is used for the analysis of acidic, aqueous solutions (e.g., acidified drinking water, wastewater, and other

[0043] Water samples, aqua regia extracts from soils and sediments). The software used to evaluate the results is that supplied by the device manufacturer.

[0044] HCl content

[0045] The HCl content was determined wet-chemically using a Titrino 904 (Metrohm) and an Optrode (Metrohm) using tetrabromophenolphthalein ethyl ester as an indicator. The corresponding value was then determined using the included tiamo software.

[0046] Purity of the products

[0047] The percentage composition of the products was determined by gas chromatography. An Agilent GC 7890B with autosampler (G4513, Agilent) was used. An MXT 1 separation column (60, μm* 0, 28 mm) from Restek was used, using helium as the carrier gas. Quantification was performed using the Compass CDS software (Scion Instruments). 1.1: Preparation with 1.8 equivalents of urea, with neutralization according to US2012095248A (=equivalent to DE102009027257A1) (not according to the invention).

[0048] In a nitrogen-purged 1-liter three-necked flask (left: T-piece with reflux condenser and dropping funnel; center: KPG stirrer; right: thermometer) with a drain tap, 150 g of urea were placed, and 196 g of ethanol and 144 g of isohexane were added under nitrogen blanketing. 156 g of HM-silane (dichloromethylsilane) were added dropwise via the dropping funnel over a period of 120 minutes while stirring. The temperature rose to a maximum of 49°C. After stirring for a further 10 minutes, the stirrer was turned off, and phase separation was initiated for 1 hour. The lower phase (316.1 g) was then drained off and discarded. The remaining upper phase (329.9 g) was first treated with 9.7 g of NaHCO3 and stirred for 1 hour. After a second addition of 4.5 g of NaHCO3 and stirring for another hour, the product was filtered through a fluted filter and then sampled. The measurement results are shown in Table 1. The value is 960 ppb boron, which is completely inadequate.To achieve values ​​below 100 ppb, a final processing step is mandatory according to US2012095248A (=equivalent to DE102009027257A1). This is extremely time-consuming, as the solvent and excess ethanol must first be removed via a 10-tray column, and the diethoxymethylsilane must be fractionally distilled at a reflux ratio of 1 to 3.

[0049] Table 1 1.2: Batch with 2.3 equivalents of urea, without neutralization

[0050] In a N2-purged 500 mL three-neck flask (left: T-piece with

[0051] 60 g of urea were placed in a reflux condenser and dropping funnel (center: KPG stirrer; right: thermometer) with a drain tap, and 63.2 g of ethanol and 43.3 g of isohexane were added under an N2 blanket. 50 g of HM-silane (dichloromethylsilane) were added dropwise via the dropping funnel over a period of 50 minutes with stirring. The temperature rose to a maximum of 50°C. After stirring for a further 10 minutes, the stirrer was turned off and phase separation was initiated for 1 hour. The lower phase (114.9 g) was then drained off and discarded. The remaining upper phase (102.7 g) was sampled (GC and elemental analysis for boron). The measurement results can be found in Table 2. The crude product with 2.3 equivalents of urea without neutralization is referred to below as M2E-crude-acidic.

[0052] Table 2

[0053] 1.3: Distillation of crude acidic M2E with the addition of variable amounts of N-methylglucamine

[0054] Crude acidic M2E was placed in a nitrogen-purged 100-mL round-bottom flask equipped with a stir bar, and N-methylglucamine was added according to the table below. A nitrogen-blanked reflux condenser was then attached, and the mixture was refluxed for 30 minutes. After briefly cooling below boiling point, the reflux condenser was replaced with an nitrogen-purged distillation head equipped with a thermometer (immersed in the reactant flask) and a receiver flask, and the mixture was then reheated. Distillation was continued until no further distillate accumulated in the receiver at an internal temperature of 100°C (distillation time: approx. 15 minutes). The distillate was sampled for boron. The sample weights and results can be found in Table 3 below.

[0055] Table 3

[0056] * according to the invention

[0057] Only the amount of N-methylglucamine used according to the invention achieves efficient boron depletion, resulting in the desired 100 ppb total boron. The other specifications (product purity, HCl content, total chlorine content, nitrogen content) are also not affected by the addition of N-methylglucamine (see table above; here: only the HCl value is shown).

[0058] 1.4: Distillation of crude M2E with addition of compounds described in the literature for bora enrichment

[0059] In a N2-purged 100 mL round-bottom flask, M2E crude was placed with a stir bar and the appropriate additive was added

[0060] (see table). A reflux condenser with a nitrogen blanket was then attached and the mixture was boiled under reflux for 30 minutes. After briefly cooling to below boiling point, the reflux condenser was replaced by an N2-purged distillation bridge with a thermometer (immersed in the reactant flask) and a receiver flask, and the mixture was then heated up again. Distillation was continued until no further distillate was present in the receiver at an internal temperature of 100 °C (distillation time approx. 15 minutes). The distillate was sampled for boron. The initial weights and the results can be found in Table 4 below.

[0061] Table 4

[0062] None of the additives described in the literature and tested here could reduce the boron content to the desired extent.

[0063] Even by adding N-methylglucamine to the usual crude product (= M2E-crude), the desired value of 100 ppb boron or less could not be achieved, as can be seen from Table 5 below.

[0064] Table 5

[0065] The desired result of efficient boron depletion results exclusively from the inventive interaction between the non-neutralized, slightly acidic crude product (= M2E-crude-acidic) and the addition of N-methylglucamine before the pure distillation of the M2E-crude-acidic.

Claims

Patent claims 1. Process for the preparation of an organoalkoxyhydrogensilane of the general formula (I) with a boron content of not more than 100 ppb R 1 x H y Si (OR 2 ) z (I) where x+y+z = 4 and x, y, z greater than or equal to 1, wherein in a first step at least one boron-contaminated organohalohydrogensilane of the general formula (II) R 1 xH y SiHal z (II) where x+y+z = 4, x, y, z is greater than or equal to 1, and R 1 are linear or branched alkyl, cycloalkyl, aryl, alkenyl or arylalkyl radicals having 1 to 12 carbon atoms and Hal is F, O1, Br or I, with at least one alcohol R 2 -OH where R 2Methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert. -butyl, n-pentyl, isopentyl, neopentyl or tert. -pentyl radical, in the presence of > 1z equivalents of urea, i.e. at least the equivalent amount of urea based on the Hal amount of the contaminated organohalohydrosilane of the general formula (II), and in the presence of at least one organic solvent, and then the organic lower phase is separated off, the crude product of the upper phase containing 10 to 2000 [ppm] of hydrogen chloride, and in a second step the crude product obtained from the upper phase is admixed with 0.5 to 5 wt.% N-methylglucamine, based on the total mass of crude product and N-methylglucamine, and boiled under reflux in a protective atmosphere for between 10 minutes and 2 hours, and then the organoalkoxyhydrogensilane of the general formula (I) is distilled off under a protective atmosphere.

2. Process according to claim 1, characterized in that the reaction in the first step takes place in the presence of 1.1z to 1.5z equivalents of urea.

3. Process according to claim 1, characterized in that 1.5 to 5 wt.% N-methylglucamine is used in the second step.

4. Process according to claim 1, characterized in that 2 to 5 wt.% N-methylglucamine is used in the second step.

5. Process according to one of claims 1 to 4, characterized in that a non-polar organic solvent is used in step 1.

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