641 results about "Trimethylsilyl chloride" patented technology

The present invention discloses a method for preparing low density silica aerogel under normal pressure. The method comprises: mixing tetraethoxysilane, water and ethanol according to a volume ratio of 1:0.5-19:1-29, adding an acid to adjust the pH value to 3-4, carrying out catalysis hydrolysis, adding an alkali to adjust the pH value to 6-6.5, carrying out catalysis gelating for 8-10 min to obtain a wet gel, aging the wet gel for 6-36 h at a room temperature, adding n-hexane to carry out solvent replacement for 6-36 h, immersing in a trimethylchlorosilane and n-hexane mixed solution to carry out hydrophobic modification for 12-15 h, adopting a n-hexane washing solution to remove the modification solution, placing into a muffle furnace to heat to a temperature of 30-250 DEG C, drying, and finally cooling to a room temperature to obtain the silica aerogel. Test results show that the density of the SiO2 aerogel is 50-80 kg / m<3> and is significantly lower than the density of the SiO2 aerogel prepared under the normal pressure dry condition in most of the public reports.

The invention discloses a preparation method of a super-hydrophobic active carbon modified material. The material is prepared by applying a chemical liquid phase impregnation method, using trimethylchlorosilane as a modifier, using absolute methanol as a solvent, respectively using pre-processed coal columnar active carbon and coconut shell granulated active carbon as carriers, impregnating via liquid phase, drying in vacuum, and commonly blowing air and drying. The hydrophobic performance is respectively detected through a contact angle test and a liquid water adsorption experiment; and the adsorption is checked by using benzene adsorption experiment and an iodine value test. The invention has the advantages of simple preparation process, less material consumption and wild preparation condition; and the preparation method is carried out at room temperature. The prepared active carbon modified material has super-hydrophobic surface chemical performance and great pore volume, which makes up the shortcomings of easy absorption of moisture in the multi-pore carbon material with high humidity and small absorption capacity of the target organic matters; and the prepared active carbon modified material is easy to recycle and can be repeatedly recycled, so that the industrial cost is reduced and a foundation is further laid for the industrialized application.

The invention relates to a method for simultaneously preparing SiO2 aerogel and zeolite by utilizing fly ash, belonging to the technical field of the high-efficiency resource utilization of solid wastes and chemical material preparation. The method is as follows: the fly ash is firstly processed by high-temperature activation and then carries out hydro-thermal synthesis reaction with a sodium hydroxide water solution, soluble glass is catalyzed by a sulphuric acid with certain concentration, or the solution carries out cation exchange resin and is then processed by base catalysis to obtain SiO2 gel; aquagel is processed by solvent exchange / surface modification by utilizing a mixed solution of alcohols / alkanes solvent and trimethylchlorosilane, and the SiO2 aerogel is obtained under the condition of normal pressure and dryness; the fly ash is reacted with NaOH and then filtered to obtain filter residue, and the filter residue is further reacted with the NaOH so as to synthesize fly ash zeolite. The invention is not only a new way of the high-efficiency recycling of the solid wastes, but also a new technical method of the low-cost preparation of the SiO2 aerogel and the zeolite.

The invention discloses a method for preparing low-density high-performance SiO2 aerogel at constant pressure, which comprises the following steps of: performing ion exchange to mixed solution of industrial water glass and deionized water with cation exchange resin by using a two-step method of sol-gel so as to remove Na<+>; adjusting a pH value by using HC1 to obtain sol; keeping stand of the sol and adjusting the pH value by using NH2.H2O to obtain wet gel; carrying out fractional aging and solvent exchange; putting the wet gel into aging liquid which is obtained by mixing ethyl orthosilicate and ethanol for aging; putting the aged wet gel into normal hexane for carrying out solvent exchange; performing surface modification; putting the wet gel subjected to the solvent exchange into mixed liquid of trimethylchlorosilane and normal hexane for performing surface modification; and finally, drying the mixture at the constant pressure and putting the wet gel subjected to the surface modification into normal hexane for drying at the constant pressure. The method has the advantages of low preparation process cost, excellent product performance and controlled reaction process.

The invention discloses a method for preparing super-hydrophobic silica aerogel by atmospheric pressure drying. The method comprises the following steps: 1) preparing sol; 2) gelatinizing the sol; 3)aging gel; 4) exchanging a gel solvent; 5) carrying out surface hydrophobic modification; and 6) carrying out drying under atmospheric pressure. According to the preparation method of the silica aerogel, provided by the invention, tetraethoxysilane is used as a silicon source, ethanol is used as a solvent, acid and alkali are used as catalysts, and trimethylchlorosilane is used as a surface modifier, so that super-hydrophobic silica aerogel is prepared by atmospheric pressure drying. The prepared SiO2 aerogel with a super-hydrophobic three-dimensional network structure is tested to have a highspecific surface area, low density and good hydrophobicity at a room temperature. Therefore, the silica aerogel prepared through the method provided by the invention has excellent adsorption performance and has a good application prospect in the field of energy conservation. The preparation method of the silica aerogel under atmospheric pressure, provided by the invention, is simple in procedureand low in equipment requirements, can also shorten the process flow and reduce the cost, and is easy to industrialize.

The invention discloses a method for synthesizing dihydroxyl-terminated polysiloxane. The method synthesizes the target dihydroxyl-terminated polysiloxane compound by using unsaturated epoxy compound, tetramethyldisiloxane, methylaminoethanol and octamethylcyclotetrasiloxane as starting materials and by hydrosilylation, epoxy-opening and equilibrium polymerization. The hexamethyldisilazane or trimethylchlorosilane are not needed as a hydroxyl protector, so the production cost is reduced; and hydroxyl protection and deprotection are avoided in a preparation process, so reaction steps are reduced, the total reaction time for synthesizing the final product is short and the production efficiency is increased.

The invention belongs to the technical field of building materials and particularly relates to inorganic thermal-insulation mortar and a production method thereof. The production method includes: using rice husks as the raw material, performing pickling preprocessing, calcining, using alkali dissolution to extract sodium silicate, removing impurities to obtain silicic acid, adding aluminum silicate fibers and tetraethyl silicate to serve as the framework of gel, performing condensation polymerization to deposit silicon dioxide composite hydrogel on the framework, cleaning with anhydrous ethanol and normal hexane, using trimethylchlorosilane to perform hydrophobic modification to obtain silicon dioxide aerogel, using the capillary force of the silicon dioxide aerogel adsorb paraffin, serving as the phase change thermal storage material, into pores to compact the aerogel, mixing the prepared silicon dioxide composite aerogel phase change material with expanded and vitrified small balls, silica fume and the like, and discharging to obtain the inorganic thermal-insulation mortar. The prepared inorganic mortar is small in heat conductivity coefficient, low in contractibility rate, high in strength, capable of effectively increasing the crack resistance and seepage resistance of the mortar and capable of prolonging building service life.

The invention provides a preparation method for a glass fiber-reinforced water glass-based silica composite aerogel, which relates to a silica aerogel. The preparation method comprises the following steps: mixing methoxysilane with a water glass solution and water and allowing methoxysilane to be hydrolyzed in water to obtain solution A; then adding a strongly acidic styrene resin for ion exchange, carrying out pumping filtration to obtain a solution with a pH value of 2 to 3, adding a glass fiber having undergone heat treatment into the solution obtained after pumping filtration and adding ammonia water to adjust a pH value to 8 to 8.5 so as to obtain a fiber compounded silica sol; transferring the fiber compounded silica sol to a container for standing so as to obtain a composite silica hydrogel; and then immersing the composite silica hydrogel in an absolute ethyl alcohol solution for aging and alcoholization of the gel, immersing the wet gel obtained after alcoholization in a mixed solution of trimethylchlorosilane, absolute ethyl alcohol and hexane, carrying out surface modification and drying the modified gel so as to obtain the glass fiber-reinforced water glass-based silica composite aerogel. The preparation method provided by the invention has the advantages of low cost, simple process, a short production period, a controllable product shape and capacity of realizing continuous production.

The invention relates to a preparation method for amino-terminated hyperbranched polysiloxane modified waterborne polyurethane. The preparation method comprises the following steps: with 3-aminopropyltriethoxysilane (kh550) and trimethylchlorosilane (TMCS) as raw materials, subjecting 3-aminopropyltriethoxysilane (kh550) and trimethylchlorosilane (TMCS) to hydrolytic condensation so as to prepareamino-terminated hyperbranched polysiloxane (HPSi-NH2); and with the HPSi-NH2 as a cross-linking agent, allowing the HPSi-NH2 to react with a polyurethane prepolymer (PPU), carrying out branching andchain extension so as to prepare the amino-terminated hyperbranched polysiloxane modified waterborne polyurethane (HSiPU), and adding an end-capping agent during synthesis so as to control the degreeof the reaction at the same time. Thus, modified waterborne polyurethane has the performance advantages of traditional organosilicone waterborne polyurethane; meanwhile, phase separation of organosilicone modified waterborne polyurethane is reduced; mechanical properties and bonding performance of the product are increased; and an obtained emulsion has excellent comprehensive performance, and canbe used as a leather adhesive or a water-resistant coating.

A method for synthesizing L-carnosine belongs to the organic synthesis technical field. The method is as follows: beta-alanine is dissolved in non-polar solvent to be reacted with phthalic anhydride under the catalysis of organic amine, and then phthaloyl-beta-alanine is obtained through water recrystallization; the phthaloyl-beta-alanine is dissolved in solvent to synthesize phthaloyl-beta-alanyl chloride through the chlorinated reagent of acyl chloride phthaloyl-beta-alanine; L-histidine is reacted with hexamethyl disilazane or trimethylchlorosilane to obtain L-histidine trimethylsilane protector; the protector is reacted with the phthaloyl-beta-alanyl chloride to obtain hydrochloride product with the protecting group divested by water, and then neutralization product is obtained by the hydrochloride product obtained through the neutralization condensation reaction of alkaline reagent, thereby obtaining L-carnosine crude product through the hydrazinolysis of the neutralization product by hydrazine hydrate; and the crude product is purified to obtain L-carnosine finished product. The method has low raw material consumption, short reaction procedure and high yield; moreover, the quality of synthesized L-carnosine can meet the requirements of industrial production.

The invention relates to a preparation method of super-hydrophobic active carbon. The preparation method is characterized by comprising the following steps: (1) oxidation modification of active carbon: firstly heating active carbon at 120 DEG C for 5h, adding the active carbon according to the dosage of 10g / 0.03L into concentrated nitric acid, stirring and mixing for 0.5h while controlling the temperature at 25 DEG C, carrying out centrifugal separation to obtain a solid, and carrying out vacuum drying on the solid to obtain the active carbon which has undergone oxidation modification; and (2) preparation of the super-hydrophobic active carbon: adding the active carbon according to the dosage of 10g / L into trimethylchlorosilane, stirring and heating at 40 DEG C for 8h, carrying out suction filtration to obtain a solid, and carrying out vacuum drying on the solid so as to obtain the super-hydrophobic active carbon. According to the invention, methyl is grafted on the active carbon by a mode of forming chemical bonds. Thus, the super-hydrophobic active carbon has advantages of large quantity of methyl groups on the active carbon and strong tamper-resistant capability.

A composite adsorptive filter material containing porous aerogel is prepared through proportionally mixing ethyl n-silicate, alcohol, water and HF, stirring, laying aside to obtain wet SiO2 gel, immersing the wet SiO2 gel and fibers or fabric in the solution mixture of trimethyl chlorosilane and n-hexane for modifying, and heat treating at 100-200 deg.C.

The invention discloses a preparation method of an Al2O3-SiO2 composite aerogel material by ambient drying, relates to a preparation method of an aerogel material, and aims to solve the problem of poor mechanical properties of pure aluminum aerogel and to lower preparation cost and risk. The preparation method comprises the following steps: 1, mixing silica sol and alumina sol to obtain silicon-aluminum composite sol; 2, performing solvent replacement on the silicon-aluminum composite sol with an ethanol / isopropanol solution in certain proportion; 3, modifying the gel through a mixed solutionof trimethylchlorosilane and n-hexane; 4, adding n-hexane to the modified gel for solvent replacement again; and 5, preparing by ambient drying. According to the preparation method provided by the invention, the ambient drying method is adopted, and the mechanical properties of alumina aerogel is enhanced by composite silica; the morphology of aerogel subjected to calcining at 1,200 DEG C can still be maintained, and the aerogel has good high-temperature resistance.

A semiconductor device having a wiring structure that is enhanced in adhesion between a dielectric thin film and a conductive layer and has high reliability is provided.A method of the invention includes: a step of supplying reactive plasma on a surface of a dielectric thin film in which a plurality of pores are arranged around a skeleton mainly made of a Si—O bond, to perform a pretreatment; a step of forming a conductive film on the surface of the pretreated dielectric thin film by a sputtering method; and before the pretreatment step, bringing a gas containing at least one kind of tetramethylcyclotetrasiloxane (TMCTS), hexamethylsilazane (HMDS) and trimethylchlorosilane (TMCS) molecules into contact with the surface of the dielectric thin film.

The invention relates to a high purity full porous silica gel-bonded chromatography immobile phase preparation method, and belongs to the technical field of high-performance liquid chromatography packing preparation. According to the preparation method, a self-made high purity porous spherical silica gel is adopted as a raw material, and surface activation and other pre-treatments are performed on the silica gel, such that the surface of the porous silica gel microspheres presents low activity, low acidity and good uniformity; and octadecyldimethylmethoxysilane is bonded on the surface of the activated silica gel, then a linkage effect of a silane coupling agent gamma-aminopropyltriethoxysilane (KH550) is adopted to bond methyl iodide to the surface of the silica gel, and finally trimethylchlorosilane is adopted to carry out an end capping treatment to obtain the full porous silica gel-bonded chromatography immobile phase. With the method, a chromatography separation performance of the bonded silica gel packing can be improved, such that the immobile phase has advantages of rapid separation, good peak shape, wide separation range, and the like.

Disclosed are methods for the dealkylation of phosphonate esters by use of trimethylchlorosilane as the dealkylating agent. In particular, this invention is directed to the discovery that high yields for the dealkylation of phosphonate esters can be achieved within relatively short reaction times by the use of trimethylchlorosilane provided that the dealkylation procedure occurs in a sealed vessel containing a compatible solvent.

The invention discloses a preparation method of a preparation for a radioactive gas purifying capability test in a nuclear power plant, which comprises the following steps of: mixing by using a methyl phosphate compound or a dimethylacetal compound, acetonitrile, trimethylchlorosilane and a radioactive iodine source as raw materials, and then reacting for 10-40 minutes at the temperature of 20-50DEG C to obtain the preparation for the radioactive gas purifying capability test in the nuclear power plant. The invention provides the preparation method of the preparation for the radioactive gas purifying capability test in the nuclear power plant, wherein reactants are not virulent, the reaction can be carried out at high speed and high efficiency without high temperature, and other productsexcept methyl iodide have no harm or small toxicity to nuclear-grade impregnated active carbon in an iodine filter.

The invention relates to a preparation method for silicon dioxide aerogel. The method includes the following steps: (1) under the acidic condition that pH is equal to 3 to 5, stirring silicon tetrachloride and water for reaction, then adding ammonia water to regulate pH to 8 to 10, adding water and ethanol, and after hydrolytic polycondensation reaction, forming alcogel; (2) carrying out extraction, and removing water / alcohol mixture contained in the alcogel; taking gel solution, adding anhydrous methanol or ethanol, and replacing the water / alcohol mixture in gel pores with the anhydrous methanol or ethanol; (3) adding trimethyl chlorosilane and alkane to alkylate Si-OH on the surface of the gel skeleton, and after drying under the normal pressure, the SiO2 aerogel is produced. The invention has the following advantages that: (1) since the silicon tetrachloride as byproduct produced in a large amount by the organosilicon industry is used as raw material, the material cost in the process of production is greatly reduced; (2) compared with the conventional supercritical drying, the adopted normal-temperature drying can greatly reduce conditions needed by reaction; and (3) the invention cannot destroy the nanopore structure of the SiO2 aerogel, and can stably increase the reaction speed at the same time.

The invention relates to a preparation method of lithium tetrafluorooxalatophosphate and lithium difluorodioxalatophosphate. The method comprises the following steps: preparation of a titration solution: dissolving lithium hexafluorophosphate in an organic solvent, and adding trimethylchlorosilane into the solution; preparation of a base solution: dissolving oxalic acid into an organic solvent, preparing an organic alkali solution in the same way, adding the organic alkali into the oxalic acid solution, and stirring the solution; slowly dropwise adding the prepared titration solution into thereaction base solution, and when the molar ratio of lithium hexafluorophosphate to oxalic acid is 1:1.8-1:2.5 and the reaction temperature is 15-40 DEG C, carrying out a reaction to generate the lithium tetrafluorooxalatophosphate; when the molar ratio of lithium hexafluorophosphate to oxalic acid is 1:1.8-1:2.5 and the reaction temperature is 15-40 DEG C, carrying out a reaction to generate the lithium difluorodioxalatophosphate; after the reaction is finished, adjusting the temperature of the reaction system, continuously stirring the reaction product for a period of time, and filtering andrecrystallizing the reaction product to obtain the required products. The method is mild in reaction condition and easy to control, the solvent can be repeatedly used, the cost is saved, and the yieldis further increased.

The invention discloses a preparation method of a soluble, colorless, transparent and low-thermal-expansion-coefficient polyamide imide film. According to the prepared film, fluorine-containing diamine monomers serve as diamine monomers, trimellitic anhydride acid chloride serves as anhydride monomers, and the polyamide imide film is further prepared through a trimethylchlorosilane activation mechanism under a simple and moderate synthesis condition. The prepared polyamide imide film has high dimensional stability (the CTE is 5-15 ppm / DEG C or so) and good temperature resistance (Tg is 300 DEG C or so), the transmittance of visible light wavebands is 90% or so, the prepared polyamide imide film can be dissolved in an aprotic polar solvent and is convenient to machine and process, and the comprehensive performance of the prepared polyamide imide film meets the material performance requirement of a part of devices in the microelectronics and optoelectronics field.

The invention discloses a method for preparing fiber-reinforced silicon dioxide aerogel. The method comprises the following steps: mixing metasilicic acid butyl ester, tertiary butanol and water according to a ratio, adjusting the pH value through hydrochloric acid and ammonium hydroxide, and compounding with a glass fiber felt so as to obtain wet fiber-reinforced silicon dioxide gel; performing soaking modification with trimethylchlorosilane and hexamethyldisiloxane, and further performing CO2 supercritical drying, so as to obtain hydrophobic fiber-reinforced silicon dioxide aerogel. Novel gel raw materials are used, the channel for preparation of aerogel is further widened, the preparation cost is lowered, moreover, excellent product quality is achieved.

The invention discloses a novel method used for synthesizing cholesterol. The novel method comprises following steps: 1, stigmasterol 02 is dissolved in an organic solvent I, and is subjected to silicon etherification reaction with trimethylchlorosilane under the effect of a catalyst, and a compound 03 is obtained via water washing and condensation; 2, the compound 03 is dissolved in an organic solvent II for ozone oxidation, zinc powder and acetate acid gracial are added for reduction, after reduction, filtering, washing, and condensation are carried out so as to obtain a compound 04; 3, triphenylphosphine is reacted with 1-halogenated-3-methyl butane so as to obtain 3-methyl butyl triphenyl halogenated phosphorus, the 3-methyl butyl triphenyl halogenated phosphorus is added into an aprotic solvent, a strong base is added, wittig reaction with a compound 4 is carried out, and neutralizing, condensation, and filtering are carried out so as to obtain a compound 05; 4, the compound 05 is subjected to selective hydrogenation in a solvent III under the action of a catalyst and a passivator, and filtering, condensation, and crystallization are carried out so as to obtain cholesterol 01. The novel method is simple; raw materials are cheap; the novel method is economic and is friendly to the environment, and is convenient for industrialized production.

A preparation method of a 16 Alpha-methyl steroidal compound comprises: taking a formula (I) compound as a substrate, reacting with 0.2 to 0.1 time catalyst, 1 to 1.5 times trimethyl chlorosilane, 1 to 1.5 times Grignard reagent and 2 to 4 times triamine phosphate in organic solvent to obtain a formula (I) compound, and taking the formula (I) compound to react with 1 to 5 times alkali and 1 to 3 times meta-chloroperoxybenzoic acid in organic solvent to obtain a formula (III) compound.

The invention provides a preparation method of an immobilized beta-cyclodextrin derivative type chiral stationary phase. The preparation method comprises the following steps: reacting isocyanate propyl triethoxy silane with beta-cyclodextrin; performing derivatization modification on a hydroxyl group on a beta-cyclodextrin glucose unit by using phenyl isocyanate to obtain a beta-cyclodextrin derivative; coating the beta-cyclodextrin derivative bonded with a small amount of silane coupling agent on the surface of aminopropyl silica gel, and performing condensation in ethanol / aqueous solution in the presence of trimethylchlorosilane by using the silane coupling agent in the beta-cyclodextrin derivative molecules to finally obtain the immobilized beta-cyclodextrin derivative type chiral stationary phase, wherein the phenylcarbamate beta-cyclodextrin derivative molecules are connected by using a silicon-oxygen-silicon bond to form an inclusion netlike structure which covers the surface of the aminopropyl silica gel. The preparation method has the characteristics of simplicity, few steps and high bonding efficiency, can be applied to the normal-phase high-performance liquid chromatographic condition, and has the advantages of high chromatographic column stability and high chiral separation capacity.

The invention discloses a preparation method of silica aerogel. Ethyl orthosilicate serves as a silicon source, methyl triethoxysilane serves as a co-precursor, ultrasonic water serves as a reactant,absolute ethyl alcohol serves as a solvent, hydrochloric acid and ammonia water serve as catalysts, SiO2 wet gel is prepared by acid-base two-step catalysis, secondary modification and ambient pressure drying and soaked in absolute ethyl alcohol solution, a wet gel sample is subjected to surface modification in trimethylchlorosilane, absolute ethyl alcohol and n-hexane mixed solution with a certain volume ratio after standing and aging for a period of time, and finally, the SiO2 aerogel is prepared by ambient pressure drying in air atmosphere. The method for preparing the silica aerogel is simple in process and strong in controllability and has good heat conductivity coefficient, specific surface area, average pore diameters, density, porosity, contact angles and reproducibility.

The invention discloses a preparation method of a low-apparent-viscosity polyamide acid solution. The preparation method comprises the following specific steps: (1) polymerizing diamine monomers with dianhydride monomers to obtain a polyamide acid solution, adding trimethylchlorosilane with the mass accounting for 5-40wt% of polyamide acid, and stirring at room temperature for 1-5 hours to obtain a polyamide acid solution with the apparent viscosity of 2,000-15,000 centipoises; or (2) polymerizing all the diamine monomers with 60wt%-90wt% of the dianhydride monomers to obtain the polyamide acid solution, adding the trimethylchlorosilane and the rest dianhydride monomers, and stirring at room temperature for 1-5 hours, wherein the molar ratio of the diamine monomers to the dianhydride monomers is 1:1 and the additive amount of the trimethylchlorosilane is 5%-25% of the total mass of the polyamide acid. The invention further provides the low-apparent-viscosity polyamide acid solution prepared by the method. When the polyamide acid solution is prepared by the method (1), the apparent viscosity of the solution is 2,000-15,000 centipoises; when the polyamide acid solution is prepared by the method (2), the apparent viscosity of the solution is 1,000-11,000 centipoises.

A disclosed preparation method for a beta-cyclodextrin chiral stationary phase comprises: taking SiO2 microballoons as a raw material, and bonding beta-cyclodextrin (beta-CD) to the surface of SiO2 microballoons by employing 3-aminopropyltriethoxysilane (KH550), trimethylchlorosilane and 4,4'-methylenediphenyl diisocyanate (MDI) to obtain the beta-cyclodextrin chiral stationary phase. The method has continuity, simple operation and short synthetic period, and the synthetic product is convenient to be subjected to derivatization; no metal ion-containing catalysts such as NaOH, NaN3, CuI(PPh3) and the like are introduced according to the method, so that the chiral stationary phase is prevented from pollution, and the method relatively accords with the separation requirement of high-purity liquid chromatogram. The method is applicable to separation of benzene ring-containing chiral medicament intermediates and pyrethroid pesticide compounds.

The invention relates to a cracking process of organosilicon high-boiling components.. The cracking process is characterized in that organosilicon high-boiling components are used as raw materials and are subjected to impurity removal, N,N-dimethylaniline, N,N-diethylformamide or tri-n-butylamine are selected as a catalyst, the catalytic cracking is performed inside a reaction vessel to which hydrogen chloride gas is introduced, and finally, dimethyldichlorosilane, monomethyltrichlorosilane, monomethyldichlorosilane and trimethylchlorosilane are respectively recovered through a layered cooling tower at different temperatures. The cracking process has the advantages that the matching is reasonable, the operation is simple, the recovery ratio is high, and more than 60% of dimethyldichlorosilane product with high added value can be obtained.

A process for preparing methylhydrogenpolysiloxanes having trimethylsilyl end groups wherein, in a first step, methyldichlorosilane and trimethylchlorosilane are reacted with at most 0.5 mol of water per mole of hydrolyzable chlorine to give a partial hydrolysate and gaseous hydrogen chloride and, in a second step, the partial hydrolysate, to remove the SiCl groups still present, is treated with water, forming hydrochloric acid.