Thexyl (C1-C4)alkyl dialkoxy silanes; methods of preparation; and uses thereof

Abstract: Thexyl (C₁-C₄) alkyl dialkoxy silanes are a class of novel organosilicon compounds, including thexyl methyl dimethoxy silane and thexyl n-butyl dimethoxy silane, and can be synthesized by several different routes. For example, thexyl methyl dimethoxy silane is prepared starting from methyl phenyl chlorosilane which is subjected to the hydrosilation reaction with 2,3-dimethyl-2-butene to introduce a thexyl group and the compound is converted by the reaction with hydrogen chloride into thexyl methyl dichlorosilane which is methoxylated by the reaction with methyl alcohol. Uses include water-repellant agents and additives for olefin polymerisation catalysts.

Description: The present invention relates to novel organosilicon compounds. More particularly, the invention relates to dialkoxy silane compounds having a thexyl, i.e. 1,1,2-trimethylpropyl, group and an alkyl group of 1 to 4 carbon atoms bonded to the silicon atom. The novel organosilicon compounds are thexyl (C₁-C₄) -alkyl dialkoxy silanes expressed by the general formula H-CMe₂ -CMe₂ -Si (R¹) (OR²)₂, (I) in which Me is a methyl group, R¹ is an alkyl group having 1 to 4 carbon atoms and R² is an alkyl group. Although the above defined silane compounds of the invention can be prepared by several different synthetic routes, preffered methods depend on the alkyl group denoted by R¹ in the above stated general formula (I). When R¹ is a methyl group, for example, thexyl methyl phenyl chlorosilane prepared from methyl phenyl chlorosilane may be reacted with hydrogen chloride gas to be converted into thexyl methyl dichlorosilane which can readily be alkoxylated by the dehydrochlorination reaction with an alcohol. When R¹ is a n-butyl group and R² is a methyl group, the compound can be synthesized by the reaction of thexyl trimethoxy silane and n-butyl lithium or by the reaction of a thexyl trichlorosilane with n-butyl lithium to form a thexyl n-butyl dichlorosilane which may then be methoxylated by the dehydrochlorination reaction with methyl alcohol. In the drawings: Figure 1 shows an infrared absorption spectrum of thexyl methyl dimethoxy silane prepared in Example 1. Figure 2 shows an infrared absorption spectrum of thexyl n-butyl dimethoxy silane prepared in Example 2. It is known in the prior art that organosilane or polysiloxane compounds having alkoxy groups and linear-chain hydrocarbon groups bonded to the silicon atom are used to impart water-repellency to the surface of various kinds of substrate materials. In such applications, the water-repellency obtained by the treatment is generally increased when the chain length of the hydrocarbon group is increased. Further, such organosilane or polysiloxane compounds can be used as additives to the catalyst for olefin polymerization when the effect as a catalyst additive is enhanced when the chain length of the long-chain hydrocarbon group is increased. These advantages, however, are accompanied by a disadvantage due to the difficulty and inconvenience of the preparation and use of the compounds as a consequence of the increase in the boiling point and/or melting point of the compound. In addition, the rate of increase in the advantages decreases as the chain length of the hydrocarbon group is increased so as not to compensate for the disadvantages caused thereby. Accordingly, it has been much desired to obtain an alkoxy-containing organosilane compound capable of fully exhibiting the advantages but with the disadvantages mentioned above being minimised. The novel compounds of the invention are thexyl (C₁-C₄)alkyl dialkoxy silanes which are represented by the above stated general formula (I), in which R¹ is an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl and tert-butyl groups and R² is an alkyl group having, preferably, 1 to 4 carbon atoms or, more preferably, is a methyl group. Examples of the inventive thexyl (C₁-C₄)alkyl dialkoxy silanes accordingly include thexyl methyl dimethoxy silane, thexyl ethyl dimethoxy silane, thexyl n-propyl dimethoxy silane, thexyl isopropyl dimethoxy silane, thexyl n-butyl dimethoxy silane and thexyl tert-butyl dimethoxy silane, as well as those compounds corresponding to the above named compounds but replacing the methoxy group with another alkoxy group such as an ethoxy group, propoxy group or butoxy group. By virtue of the hydrolyzability of the two alkoxy groups and the bulkiness of the thexyl group, the above proposed novel organosilane compounds, i.e. thexyl alkyl dialkoxy silanes, are promising useful materials as surface-treatment agents in various kinds of building materials, including wooden materials, masonry and concrete materials. Further, the compounds readily form a coordination compound with metallic magnesium and compounds of titanium or aluminum so that they are useful as additives in complex catalysts for the polymerization of olefins, such as propylene, to give highly isotactic polypropylene. As is described above, the thexyl (C₁-C₄)alkyl dialkoxy silane of the invention can be synthesized by several different types of synthetic route, of which the most preferred method depends on the alkyl group denoted by R in the general formula (I). Thexyl methyl dimethoxy silane, one of the inventive silane compounds, for example, can be prepared by the following three-step synthetic route,including the so-called hydrosilation reaction. In the first step of the synthetic route, methyl phenyl chlorosilane or a solution thereof in a hydrocarbon solvent of a suitable concentration in the range, for example, from 1 to 5 moles/liter,is admixed with anhydrous aluminum chloride AlCl₃ in an amount of 0.001 to 50% by moles based on the amount of the silane compound to form a mixture, into which 2,3-dimethyl-2-butene in an amount of 1.0 to 1.1 moles per mole of the silane compound is added dropwise at a temperature of -20 to +40 °C or, preferably, +10 to +30 °C over a period of 0.1 to 5 hours followed by an aging period of 1 to 5 hours at room temperature to complete the hydrosilation reaction. The reaction mixture is then freed from aluminum chloride by filtration and the filtrate is concentrated by evaporating the solvent, if used, and the unreacted reactants. Distillation of the thus concentrated reaction product under reduced pressure gives a fraction boiling at about 103 °C under a pressure of 3 mmHg which is thexyl methyl phenyl chlorosilane. In the second step following the above described hydrosilation reaction of the first step, the thexyl methyl phenyl chlorosilane obtained above is dissolved in a suitable hydrocarbon solvent, preferably, in a concentration of 1 to 5 moles/liter and dry hydrogen chloride gas is blown into this solution kept at a temperature of -20 to +40 °C at a rate of 0.001 to 0.1 mole/minute per mole of the thexyl methyl phenyl chlorosilane over a period of 0.5 to 5 hours. After completion of the reaction, the reaction mixture is freed from residual aluminum chloride by filtration and the filtrate is concentrated by evaporating the solvent and hydrogen chloride. Distillation of the thus concentrated reaction product under reduced pressure gives a fraction boiling at about 75 °C under a pressure of 30 mmHg which is thexyl methyl dichlorosilane. The third step of the synthetic route is the methoxylation of the above obtained thexyl methyl dichlorosilane by the dehydrochlorination reaction with methyl alcohol. Thus, 1 mole of the thexyl methyl dichlorosilane is admixed dropwise with a n-hexane solution of methyl alcohol and urea or DBU, i.e. 1,5-diazabicyclo[5.4.0]undec-5-ene, as an acid acceptor, of which the concentration of methyl alcohol is from 5 to 20% by weight, the amount of methyl alcohol is from 2.0 to 2.5 moles per mole of the thexyl methyl dichlorosilane and the amount of the acid acceptor is approximately equimolar to methyl alcohol, at a temperature of 10 to 45 °C or, preferably, 20 to 30 °C over a period of 0.1 to 3 hours followed by an aging period of 1 to 5 hours at 20 to 65 °C to complete the reaction. The reaction mixture after completion of the reaction separates into layers upon standing so that the liquid in the lower layer containing the hydrochloride of the acid acceptor is discarded and the hexane solution in the upper layer is taken and neutralized by adding propylene oxide thereinto followed by removal of the solvent by evaporation under normal pressure and distillation of the concentrate under reduced pressure to give the desired thexyl methyl dimethoxy silane as a fraction boiling at about 82 °C under a pressure of 30 mmHg. Thexyl n-butyl dimethoxy silane or the compound of the invention of which the group denoted by R¹ in the general formula (I) is a n-butyl group can be synthesized in two different synthetic routes described below. In one of the routes, thexyl trimethoxy silane, which can be prepared by the dehydrochlorination reaction between thexyl trichlorosilane as a known compound and methyl alcohol, is reacted with n-butyl lithium to substitute a n-buthl group for one of the methoxy groups. Alternatively, the starting material is thexyl trihalogenosilane, e.g., thexyl trichlorosilane, which is reacted with a limited amount of n-butyl lithium to produce thexyl n-butyl dihalogenosilane which is then subjected to the dehydrohalogenation reaction with methyl alcohol in the presence of an acid acceptor. In the above described synthetic methods for the preparation of thexyl n-butyl dimethoxy silane, the silane compound as the starting material can be diluted, if necessary, with an organic solvent such as ether solvents, e.g., tetrahydrofuran, diethyl ether and dibutyl ether, and hydrocarbon solvents, e.g., n-pentane and n-hexane, in a concentration of at least 0.01 mole/liter. n-Butyl lithium is used preferably as a solution in an organic solvent such as ether and hydrocarbon solvents including the above named ones in a concentration of 0.01 to 4 moles/liter. The reaction of the starting silane compound and n-butyl lithium can be performed at a temperature of -78 °C to +20 °C by adding n-butyl lithium or a solution thereof to the silane compound or a solution thereof or vice versa. Removal of the precipitates of lithium salt such as lithium methoxide from the reaction mixture by filtration and the solvent by evaporation is followed by distillation of the thus concentrated reaction mixture to give the thexyl n-butyl dimethoxy silane as a fraction boiling at about 86 °C under a pressure of 3 mmHg or thexyl n-butyl dihalogenosilane, which latter compound can be readily methoxylated by the reaction with methyl alcohol in an amount of at least twice of the equimolar amount. The thexyl alkyl dialkoxy silane or, in particular, thexyl alkyl dimethoxy silane obtained in the above described method is a colorless liquid. By virtue of the controlled hydrolyzability of the methoxy groups and bulkiness of thexyl group therein, the silane compound is useful as a surface-treatment agent of various building materials including wooden, concrete and marble materials to impart the surface with water-repellency. Further, the silane compound readily forms a coordination compound with metallic magnesium and compounds of aluminum or titanium so that the silane compound can be a promising substitute for diphenyl dimethoxy silane conventionally used as an additive in complex catalysts for the olefin polymerization to give advantages that the step of the de-ashing substantially can be omitted due to the outstandingly high activity of the catalyst and an isotactic polymer can be selectively obtained even by omitting the purification process. In the following, examples are given to illustrate the synthetic procedure and characterization of the inventive silane compounds in more detail. Further, an application example is given to illustrate the usefulness of the inventive compounds as an additive in the complex catalyst for the olefin polymerization. Example 1. Into a reaction mixture prepared by adding 12.7 g (0.095 mole) of aluminum chloride to 149 g (0.952 mole) of methyl phenyl chlorosilane at 20 °C under agitation were added dropwise 85.3 g (1.015 moles) of 2,3-dimethyl-2-butene over a period of 90 minutes and the reaction mixture was further agitated at 20 °C for additional 5 hours followed by stripping of the unreacted reactants under reduced pressure. The thus concentrated reaction mixture was diluted by admixing 200 ml of benzene to give a solution into which dry hydrogen chloride gas was blown at 20 °C at a rate of 0.005 mole/minute for 3 hours. Thereafter, the reaction mixture was freed from volatile matter by stripping under a reduced pressure of 100 mmHg at 20 °C. The residual liquid after stripping of the volatile matter as above was added dropwise into a mixture of 22.4 g (0.70 mole) of methyl alcohol, 42 g (0.70 mole) of urea and 200 ml of n-hexane at 20 °C over a period of 1 hour and the reaction mixture was further agitated for an additional 3 hours at 20 °C to complete the reaction. The reaction mixture after completion of the reaction was freed from the urea hydrochloride and the hexane solution thus obtained was neutralized by admixing 10 g of propylene oxide followed by the removal of hexane by distillation under normal pressure. Distillation of the residue under reduced pressure gave 60.3 g of a clear, colorless liquid as a fraction boiling at 82 °C under a pressure of 30 mmHg. The result of the gas chromatographic analysis indicated that this product consisted substantially of a single component. This product was identified as thexyl methyl dimethoxy silane from the results of the ¹H-NMR spectroscopic analysis shown below and the infrared absorption spectrum shown in Figure 1 of the accompanying drawing so that the above mentioned yield of the product corresponds to 33% of the theoretical value. ¹H-NMR (δ, ppm, CDCl₃) 3.55 (s, 6H, -OCH₃) 1.9 - 1.1 (m, 1H, -CH) 1.1 - 0.8 (m, 12H, -CH₃) 0.13 (s, 3H, -SiCH₃) Example 2. Into a mixture of 100 ml of tetrahydrofuran and 103.5 g (0.47 mole) of thexyl trichlorosilane were added dropwise 210 ml of a tetrahydrofuran solution of n-butyl lithium in a concentration of 1.6 moles/liter over a period of 4 hours at a temperature of -78 °C followed by removal of the dry ice bath so that the temperature of the reaction mixture was increased to 10 °C after 1 hour of standing. Thereafter, the temperature of the reaction mixture was gradually increased up to 25 °C. When gas chromatographic analysis indicated completion of the reaction by the disappearance of thexyl trichlorosilane, the salt precipitated from the reaction mixture as a by-product was removed by filtration and the filtrate, after concentration by evaporating the solvent,was distilled under reduced pressure to give 32 g of a clear, colorless liquid product as a fraction boiling at 103 °C under a pressure of 5 mmHg. A 10 g portion of the thus obtained liquid was added dropwise into a mixture of 13 g (0.086 mole) of 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU), 3.0 g (0.094 mole) of methyl alcohol and 50 ml of n-hexane at 25 °C and the mixture was agitated for 2 hours to effect the reaction. When gas chromatographic analysis indicated completion of the reaction by the disappearance of the starting material, the hydrochloride of DBU was removed by filtration and the filtrate, after concentration by evaporating the solvent, was distilled under reduced pressure to give 7.5 g of a clear, colorless liquid as a fraction boiling at 86 °C under a pressure of 3 mmHg and having a refractive index of 1.4398 at 25 °C. This liquid product was found to consist of a single component according to the result of gas chromatography. This liquid product was identified as thexyl n-butyl dimethoxy silane from the results of gas chromatographic-mass spectrometric (GC-MS) analysis and ¹H-NMR analysis shown below. The above mentioned yield of the product accordingly corresponds to 31% of the theoretical value based on the amount of n-butyl lithium used as the starting material. Figure 2 shows an infrared absorption spectrum of this product. GC-MS analysis M/Z = 232 (molecular ion peak) ¹H-NMR analysis (δ, ppm, CDCl3) 3.57 (m, 6H, -OCH₃) 2.2 - 1.1 (m, 5H, -CH₃-, -CH) 1.1 - 0.5 (m, 17H, -CH₃, Si-CH₂) Example 3. Into 10 ml of a tetrahydrofuran solution containing 2.0 g (0.010 mole) of thexyl trimethoxy silane were added dropwise 6 ml of a tetrahydrofuran solution of n-butyl lithium in a concentration of 1.6 moles/liter at a temperature of -78 °C over a period of 3 hours followed by removal of the dry ice bath so as to increase the temperature of the mixture up to 25 °C to effect the reaction to completion. When the gas chromatographic analysis of the reaction mixture indicated completion of the reaction by the disappearance of the starting silane compound, the precipitated salt was removed by filtration and the filtrate, after concentration by the evaporation of the solvent, was distilled under reduced pressure to give 1.4 g of a clear, colorless liquid as the product which was identified as thexyl n-butyl dimethoxy silane from the results of analysis identical with those obtained in Example 2. Accordingly, this product was identified as thexyl n-butyl dimethoxy silane and the above mentioned yield corresponds to 63% of the theoretical value. Application Example. Into 400 ml of dried n-heptane in a four-necked flask of 1 liter capacity were added, under an atmosphere of nitrogen gas, 76.2 g (0.8 mole) of magnesium chloride and 271.9 g (0.8 mole) of titanium tetrabutoxide to form a reaction mixture which was agitated for 2 hours at 95 °C. After cooling to room temperature by standing for a while, the solid matter in the reaction mixture was collected by filtration and washed with dried n-heptane. This solid material was again introduced into a four-necked flask of 1 liter capacity and dispersed in 167 ml of n-heptane under an atmosphere of nitrogen gas. This dispersion kept at 25 °C was admixed with a mixture of 83 ml of a n-heptane and 226.7 g (1.3 moles) of tetrachlorosilane by dropwise addition over a period of 1 hour followed by heating at 55 to 57 °C for 3 hours to effect the reaction. Thereafter, a solution prepared by dissolving 10.8 g (0.05 mole) of phthaloyl chloride in 83 ml of n-heptane was added dropwise into the reaction mixture in the flask over a period of 30 minutes followed by a period of 1 hour to complete the reaction at the same temperature. After cooling to room temperature by standing for a while, the solid matter in the reaction mixture was collected by filtration and washed with dried n-heptane. This solid matter was again introduced into a four-necked flask of 1 liter capacity and 136 g (0.8 mole) of tetrachlorosilane were added thereto to effect the reaction at 55 to 57 °C for 1 hour. After cooling to room temperature by standing for a while, the solid matter in the reaction mixture was collected by filtration and washed with dried n-heptane. A 10 g portion of this solid matter was taken in a four-necked flask of 500 ml capacity together with 100 ml of n-heptane under an atmosphere of nitrogen gas and admixed with 1.9 g (0.01 mole) of thexyl methyl dimethoxy silane prepared in Example 1 at 25 °C followed by agitation of the mixture at the same temperature for 2 hours. The solid matter was collected by filtration and washed with dried n-heptane to serve as a catalytic ingredient in the propylene polymerization experiment described below. Into a stainless steel autoclave of 1 liter capacity were introduced 500 ml of dried n-heptane and 0.25 g (0.0022 mole) of triethyl aluminum and a dispersion of the same in n-heptane was prepared by agitation at 70 °C for 30 minutes followed by introduction of 200 ml of propylene as liquid thereinto. Thereafter, 6 mg of the catalytic ingredient prepared above were introduced dispersed in dry n-heptane into the autoclave to effect the polymerization reaction for 3 hours. The yield of polypropylene obtained by repeating the above experiment ranged from 13,000 to 14,000 g per g of the catalyst. This polypropylene resin contained 0.5 to 1.5% by weight of the fraction insoluble in xylene at 25 °C indicating a very low content of atactic polypropylene molecules.

Claims: A thexyl (C₁-C₄) alkyl dialkoxy silane expressed by the general formula H-CMe₂ -CMe₂ -Si (R¹) (OR²)₂ , in which Me is a methyl group, R¹ is an alkyl group having 1 to 4 carbon atoms and R² is an alkyl group. A thexyl (C₁-C₄) alkyl dialkoxy silane as claimed in claim 1 in which R² is a methyl group. Thexyl methyl dimethoxy silane. Thexyl n-butyl dimethoxy silane. A method of preparing a thexyl (C₁-C₄) alkyl dialkoxy silane as claimed in claim 1 which method comprises reacting a thexyl alkyl phenyl chlorosilane with hydrogen chloride to produce the thexyl alkyl dichlorosilane which is thereafter alkoxylated by reacting with an alcohol in a dehydrochlorination reaction. A method of preparing a thexyl (C₁-C₄) alkyl dialkoxy silane as claimed in claim 1 which method comprises reacting thexyl trimethoxy silane and n-butyl lithium, or reacting a thexyl trichlorosilane with n-butyl lithium to form a thexyl n-butyl dichlorosilane which is then methoxylated by reaction with methyl alcohol in a dehydrochlorination reaction. Use of a thexyl (C₁-C₄) alkyl dialkoxy silane as claimed in claim 1 as a water-repellant agent or an additive for an olefin polymerisation catalyst.

Inventors: IWABUCHI MOTOAKI, KUDO MUNEO, SHINOHARA TOSHIO, IWABUCHI, MOTOAKI, SHINOHARA, TOSHIO, KUDO, MUNEO
Applicants: SHINETSU CHEMICAL CO, SHIN-ETSU CHEMICAL CO., LTD.
Application year: 1991
Main classification: C07F7
IPC codes: C08F4, C07F7