Alkylhydrido siloxanes

Abstract: Alkylhydrido siloxane fluids including (i) comonomers of the formula RSi(OSiMe₂H)₃, (ii) oligomers of the formula (HMe₂SiO)₂-Si(R)-O-Si(R)-(OSiMe₂H)₂ and (iii) higher molecular weight siloxane species of the formulas RSi[(OSiMe₂) x OSiMe₂H]₃ or [HMe₂SiO(Me₂SiO) x ]₂SiRORSi[(OSiMe₂) x OSiMe₂H]₂ are described herein where Me is methyl, and R is a C₂ to C₁₈ straight-chain or branched-chain alkyl substituent. Methods of making these siloxane fluids as comonomers, oligomers and higher molecular weight species, are also disclosed.

Description: This invention is directed to a family of new alkylhydrido siloxane fluids including higher molecular weight siloxanes of the formula RSi[(OSiMe 2 ) x OSiMe 2 H] 3 or [HMe 2 SiO(Me 2 SiO) x ] 2 SiRORSi[(OSiMe 2 ) x OSiMe 2 H] 2 ; in which Me is methyl; R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent and x has a value of 1-100. Compounds such as methyltris(dimethylsiloxy)silane, CH 3 Si(OSiMe 2 H) 3 and phenyltris(dimethylsiloxy)silane, C 6 H 5 Si(OSiMe 2 H) 3 are known in the art. These are compounds where R in the formula RSi(OSiMe 2 H) 3 is either methyl or phenyl, respectively. However, compounds where R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent, as claimed herein, are not previously known. DE-A-26 30 744 discloses a method of converting organosiloxanes, preferably cyclic siloxanes, by reacting with chlorosilanes optionally in the presence of an inorganic acid by using an active carbon catalyst. It is an object of this invention to provide a new family of alkylhydrido siloxane fluids, including their higher molecular weight species. Another object of the invention is to prepare such compounds in good yield by hydrolysing the corresponding alkyltrichlorosilanes with dimethylchlorosilane, to form alkylhydrido siloxanes and by equilibrating the new alkylhydrido siloxanes with dialkylcyclosiloxanes, to form hydrido functional siloxanes of higher molecular weight. Siloxanes used according to our invention have the formulas RSi(OSiMe 2 H) 3 and (HMe 2 SiO) 2 -Si(R)-O-Si(R)-(OSiMe 2 H) 2 , and are prepared in high yield by hydrolysis of the corresponding chlorosilanes. By hydrolysis is meant simply allowing the chlorosilanes to contact excess water. The subsequent reaction is exothermic, owing especially to the heat evolved by dissolution of the hydrogen chloride in water; so either the reaction mixture must be cooled, or more simply, the halosilanes are contacted in ice water. The reaction is conducted at a temperature of from slightly below 15°C to 70°C. Preferably, the reaction is conducted at a temperature maintained below 30°C., but most preferably, at a temperature maintained slightly below 15°C. While temperatures between 30-70°C. can be employed, lesser amounts of the products may be realized. Typically, the two silanes are added in stoichiometric proportions, which is at least two moles of dimethylchlorosilane for each mole of alkyltrichlorosilane. Other proportions, such as an excess of dimethylchlorosilane can be employed, although no benefits are usually realized from the use of excess amounts. The rate of addition of the silanes to the water should be such that it does not exceed the ability to control the heat evolved during the reaction, and to also maintain the temperature within the desired range. At least an excess amount of water to the mole amount stoichiometrically necessary for complete hydrolysis of the chlorosilane monomers, and to accommodate the HCl generated, should be employed. While the upper limit on the water is not critical, the preferred amount of water is about a nine-fold excess based on Me 2 HSiCl. Upon completion of the reaction, the desired siloxane may be easily recovered by any appropriate method. For example, this can be accomplished by draining off the aqueous-HCl bottom layer of the reaction mixture; and washing and neutralizing the siloxane layer. The siloxane layer may be further dried and filtered, if desired. Recovery of the siloxanes is enhanced by additional steps of solvent stripping and fractional distillation at reduced pressure. This reaction is shown below in "Scheme 1". In contrast to the reaction as depicted in "Scheme 1", the preparation of MeSi(OSiMe 2 H) 3 from MeSi(OMe) 3 and Me 2 HSiCl yields a mere 45 percent of the product as shown in "Comparison Example V". In further contrast to the reaction in "Scheme 1", the preparation of MeSi(OSiMe 2 H) 3 from MeSiCl 3 and Me 2 HSiCl yield, only 53 percent of the product as shown in "Comparison Example VI". According to "Scheme 1", the alkyl group slows the reactivity of the chlorosilane, so that self-condensation is much slower than when R is methyl (Me) as in MeSiCl 3 or MeSi(OR) 3 . As a result, the yield of RSi(OSiMe 2 H) 3 is significantly and unexpectedly enhanced. Our incorporation of an alkyltrichlorosilane makes it possible to eliminate the dual waste streams generated when MeSi(OMe) 3 and Me 2 HSiCl are employed. In addition, HCl generated in our hydrolysis reaction is easily reclaimed. The amount of RSi(OSiMe 2 H) 3 obtained in the hydrolysis is dependent upon the temperature at which the reaction is conducted. Where R is n-propyl (Pr), for example, it has been found that when the temperature is maintained slightly below 15°C., 83 percent of the product is RSi(OSiMe 2 H) 3 . At a temperature of 30°C., 79 percent of the product is RSi(OSiMe 2 H) 3 ; while at a temperature of 40°C., 47 percent of the product is RSi(OSiMe 2 H) 3 . At higher temperatures, larger amounts of (HMe 2 SiO) 2 -Si(R)-O-Si(R)-(OSiMe 2 H) 2 and the higher molecular weight siloxane species RSi[(OSiMe 2 )xOSiMe 2 H] 3 or [HMe 2 SiO(Me 2 SiO) x]2 -SiRORSi[(OSiMe 2 ) x OSiMe 2 H] 2 are formed. The products RSi(OSiMe 2 H) 3 and (HMe 2 SiO) 2 SiRORSi-(OSiMe 2 H) 2 from the hydrolysis in "Scheme 1" above, is used in the preparation of our higher molecular weight siloxane species. These materials are prepared by an acid catalyzed ring-opening of cyclic siloxanes, such as a dimethylcyclosiloxane, followed by insertion into RSi(OSiMe 2 H) 3 or (HMe 2 SiO) 2 SiRORSi(OSiMe 2 H) 2 . Such a process is shown in reaction "Scheme 2". Suitable acid catalysts for use in "Scheme 2" are hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, acetic acid, trichloroacetic acid and trifluoromethane sulfonic acid. The catalyst is present in the reaction medium, usually at a level of 0.01 to 30 percent by weight of the total siloxane. Typically, the acid catalyst is used within the lower end of this range. The method according to "Scheme 2" is preferably carried out by creating a mixture comprising the cyclic siloxane (Me 2 SiO) a , RSi(OSiMe 2 H) 3 or (HMe 2 SiO) 2 SiRORSi-(OSiMe 2 H) 2 and the acid catalyst. The mixture is then heated with agitation at a polymerization reaction temperature, until essentially all of the cyclic siloxane is reacted. The time required will vary depending on the reactants and the reaction conditions. Polymerization reaction temperatures useful in "Scheme 2", are typically above the freezing point and below the boiling point of water. Pressures above or below atmospheric pressure may allow operation outside of this range, however. The preferred temperature range is at least 50°C. but less than 95°C. The polymerization reaction in "Scheme 2" is stopped at the desired level of conversion of cyclic siloxane, by using methods known in the art. It is preferred to stop the reaction when the largest amount of cyclic siloxane has been reacted, or when the ring-chain equilibrium for the system has been attained. Reaction times of less than 24 hours, and typically less than 5 hours, are sufficient to achieve the desired level of conversion. The methods for stopping the reaction typically encompass, neutralization of the catalyst by the addition of an equal, or slightly greater stoichiometric amount of a base. Either a strong or a weak base may be used to neutralize the reaction. A suitable weak base material, for example, is sodium bicarbonate. Care must be taken when using a strong base such as sodium, potassium, or ammonium hydroxide, not to over neutralize the reaction, as it may be possible to re-catalyze the reaction. It is preferred to neutralize with sufficient quantities of the base, such that the resulting mixture has a pH of about 7. Siloxanes of the types shown in "Scheme 1" and in "Scheme 2" including the comonomers, oligomers and higher molecular weight siloxane species, are useful as intermediates in the preparation of various types of organic modified siloxanes. Thus, these siloxanes have utility as intermediates in the preparation of organosiloxane ethers, which have particular application in the personal care arena. Reference is made, for example, to U.S. Patent 5,274,156, in which an organosilicon hydride is reacted with an alkenyl ether terminated organic oxyalkylene compound, to produce a mixture of silicone polyethers. Reference may also be made to U.S. Patent 5,232,693, wherein siloxanes possessing an ≡SiH functionality in the molecule are reacted with an alkene, to produce certain alkylmethylsiloxanes which are useful in the prevention of dry skin. In "Scheme 1" or "Scheme 2", the group R of this invention is a C 2 to C 18 straight-chain (unbranched) or branched-chain alkyl substituent. Suitable R substituents are ethyl; n-propyl; isopropyl; butyl; 2-methylpropyl; pentyl; 2-methylbutyl; 2,2-dimethylpropyl; hexyl; 2-methylpentyl; 3-methylpentyl; 2,2-dimethylbutyl; 2,3-dimethylbutyl; heptyl; 2-methylhexyl; 3-methylhexyl; 2,2-dimethylpentyl; 2,3-dimethylpentyl; 2,4-dimethylpentyl; 3,3-dimethylpentyl; 3-ethylpentyl; 2,2,3-trimethylbutyl; octyl; nonyl; decyl; undecyl; dodecyl; tridecyl; tetradecyl; pentadecyl; hexadecyl; heptadecyl and octadecyl. The cyclic siloxanes most suitable for use in "Scheme 2" are volatile methyl siloxanes (VMS) of the formula [(CH 3 ) 2 SiO] a , in which "a" has a value of three to six. These VMS have boiling points generally less than about 250°C. Structurally, the VMS may be represented as: Examples of some suitable cyclic VMS are (i) hexamethylcyclotrisiloxane which has a boiling point of 133°C. and the formula [(Me 2 )SiO] 3 ; (ii) octamethylcyclotetrasiloxane which has a boiling point of 171°C. and the formula [(Me 2 )SiO] 4 ; (iii) decamethylcyclopentasiloxane which has a boiling point of 205°C and the formula [(Me 2 )SiO] 5 ; and (iv) dodecamethylcyclohexasiloxane which has a boiling point of 245°C. and the formula [(Me 2 )SiO] 6 . Example I (does not fall within the scope of the present invention) Preparation of PrSi(OSiMe 2 H) 3 n-propyltris-(dimethylsiloxy)silane. A mixture of PrSiCl 3 (59.92 g, 0.338 moles) and Me 2 HSiCl (95.90 g, 1.014 moles) was added drop-wise to a 3-necked round bottom flask containing ice water (166.0 g, 9.22 moles). The flask was fitted with a thermometer, a mechanical stirrer and a pressure equalizing addition funnel. The chlorosilanes were added drop-wise through the addition funnel at a rate to maintain a temperature in the flask slightly below 15°C. The solution was vigorously mixed throughout this addition. The solution was stirred for 30 minutes after completion of the chlorosilane addition. An aqueous layer was drawn off, followed by several NaHCO 3 washes, and several water washes until neutral to pH paper. The siloxane was dried over MgSO 4 overnight and filtered under N 2 pressure, yielding a clear, colorless liquid. The final product contained 83% of PrSi(OSiMe 2 H) 3 ; 9% of (HMe 2 SiO) 2 Si(Pr)-OSi(Pr)(OSiMe 2 H) 2 and 8% of other siloxane impurities. Characterization included Si-29 Nuclear Magnetic Resonance (NMR), Gas Chromatography/Mass Spectrometry (GC/MS) and Gas Chromatography/Flame Ionization Detection (GC/FID). Example II (does not fall within the scope of the present invention) Example I was repeated, except that room temperature water was used instead of ice water and the reaction temperature was allowed to rise to 30°C. The final product contained 79% of PrSi(OSiMe 2 H) 3 , 12% of (HMe 2 SiO) 2 Si(Pr)OSi(Pr)(OSiMe 2 H) 2 and 9% of other siloxane impurities. Example III (does not fall within the scope of the present invention) Example I was again repeated, except that room temperature water was used instead of ice water and the temperature was allowed to rise to 40°C. The final product contained 47% of PrSi(OSiMe 2 H) 3 , 30% of (HMe 2 SiO) 2 Si(Pr)-OSi(Pr)(OSiMe 2 H) 2 and 23% of other siloxane impurities. Example IV Preparation of PrSi[(OSiMe 2 ) 3.5 OSiMe 2 H] 3 A solution of n-propyltris(dimethylsiloxy)silane, PrSi(OSiMe 2 H) 3 , (18.94 g, 0.064 moles) prepared in Example I, (Me 2 SiO) 4 , cyclosiloxane, (49.82 g, 0.672 moles) and 41 microliters of trifluoromethane sulfonic acid was heated to 70°C. The flask was fitted with a water cooled condensing column, a magnetic stirrer and a thermometer. The flask was flushed with N 2 prior to heating, followed by N 2 positive pressure through the top of the condenser. After heating the flask at 70°C. for four hours, the solution was cooled to room temperature, followed by the addition of NaHCO 3 (1.0 g) and diatomaceous earth (Celite™) (1.0 g). The mixture was stirred for 4 hours, followed by filtration under N 2 pressure, and yielded a clear, colorless liquid. The final average structure determined by Si-29 NMR was (PrSi) 1.0 [(OSiMe 2 ) 3.5 OSiMe 2 H] 3 . In that structure, the value "1.0" was plus or minus 0.2; the value "3.5" plus or minus 0.5; and the value "3.0" plus or minus 0.2. Dimethyl cyclic siloxanes were also present in the product. Comparison Example V Preparation of methyltris(dimethylsiloxy)silane, MeSi(OSiMe 2 H) 3 , from methyltrimethoxysilane, MeSi(OMe) 3 . A mixture of methyltrimethoxysilane, MeSi(OMe) 3 , (128.42 g, 0.943 moles) and dimethylchlorosilane, Me 2 HSiCl, (267.60 g, 2.828 moles), was added drop-wise to a three-necked round bottom flask containing ice water (166.0 g, 9.22 moles). The flask was fitted with a thermometer, a mechanical stirrer and a pressure equalizing addition funnel. Addition of the silanes was adjusted to maintain a temperature below 20°C. and was accompanied with vigorous mixing throughout the process. The solution was stirred for 30 minutes after completion of the methoxysilane and chlorosilane addition. An aqueous layer was drawn off, followed by several NaHCO 3 washes and several water washes until neutral to pH paper. The siloxane was dried over MgSO 4 overnight and filtered under N 2 pressure, to yield a clear, colorless liquid. The final product contained only 45% MeSi(OSiMe 2 H) 3 , 30% (HMe 2 SiO) 2 Si(Me)-OSi(Me)(OSiMe 2 H) 2 and 25% of other siloxane impurities. As in Example I, characterization included Si-29 NMR, GC/MS and GC/FID. Comparison Example VI Preparation of methyltris(dimethylsiloxy)silane, MeSi(OSiMe 2 H) 3 , from MeSiCl 3 and Me 2 HSiCl. A mixture of MeSiCl 3 (22.29 g, 0.149 moles) and Me 2 HSiCl (42.37 g, 0.448 moles), was added drop-wise to a three-necked round bottom flask containing ice water (72.54 g, 4.03 moles). The flask was fitted with a thermometer, a magnetic stirrer with stir bar, and a pressure equalizing addition funnel. Addition of the chlorosilanes was adjusted to maintain a temperature below 22°C., accompanied with vigorous mixing throughout the addition. The solution was stirred for 5 minutes after completion of the chlorosilane addition. An aqueous layer was drawn off, followed by several water washes until neutral to pH paper. The siloxane was dried over MgSO 4 overnight and filtered to yield a clear, colorless liquid. The final product contained only 53% of MeSi(OSiMe 2 H) 3 , 19% of (HMe 2 SiO) 2 Si(Me)-OSi(Me)(OSiMe 2 H) 2 and 28% of other siloxane impurities. Characterization included GC/FID. By comparing Examples I and II with "Comparison Examples V and VI", it is seen that siloxanes made according to the invention, are obtained in much higher yields by hydrolysis of an alkylchlorosilane. Thus, in Examples I and II, the yield of PrSi(OSiMe 2 H) 3 was 83% and 79%, respectively. In contrast, and as shown in "Comparison Example V", a preparation of MeSi(OSiMe 2 H) 3 from MeSi(OMe) 3 yielded only 45%. In further contrast, and as shown in "Comparison Example VI", a preparation of MeSi(OSiMe 2 H) 3 from MeSiCl 3 yielded only 53%. It is also noted that in Examples I to III, the product contained (HMe 2 SiO) 2 -Si(R)-O-Si(R)-(OSiMe 2 H) 2 , which was present in amounts respectively of 9%, 12%, and 30%. This evidences that the proportion of our product increased as a function of the temperature used during hydrolysis.

Claims: Compounds selected from the group consisting of RSi[(OSiMe 2 ) x OSiMe 2 H] 3 and [HMe 2 SiO(Me 2 SiO) x ] 2 SiRORSi[(OSiMe 2 ) x OSiMe 2 H] 2 , in which Me is methyl, R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent, and x has a value of 1-100. Compounds according to claim 1 in which R is selected from the group consisting of ethyl; n-propyl; isopropyl; butyl; 2-methylpropyl; pentyl; 2-methylbutyl; 2,2-dimethylpropyl; hexyl; 2-methylpentyl; 3-methylpentyl; 2,2-dimethylbutyl; 2,3-dimethylbutyl; heptyl; 2-methylhexyl; 3-methylhexyl; 2,2-dimethylpentyl; 2,3-dimethylpentyl; 2,4-dimethylpentyl; 3,3-dimethylpentyl; 3-ethylpentyl; 2,2,3-trimethylbutyl; octyl; nonyl; decyl; undecyl; dodecyl; tridecyl; tetradecyl; pentadecyl; hexadecyl; heptadecyl and octadecyl. Compounds according to claim 1 of the formula RSi[(OSiMe 2 ) x OSiMe 2 H] 3 , in which Me is methyl, R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent and x has a value of 1-100. Compounds according to claim 1 of the formula [HMe 2 SiO(Me 2 SiO) x ] 2 SiRORSi[(OSiMe 2 ) x OSiMe 2 H] 2 , in which Me is methyl, R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent, and x has a value of 1-100. A compound according to any of claims 3 to 4 in which R is n-propyl. A method of making a compound of claim 1 having the formula RSi[(OSiMe 2 ) x OSiMe 2 H] 3 , in which Me is methyl, R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent, and x has a value of 1-100, comprising (i) hydrolyzing an alkyltrichlorosilane with dimethylchlorosilane to form a compound of the formula RSi(OSiMe 2 H) 3 , wherein Me is methyl and R is a straight-chain or branched-chain alkyl substituent; (ii) reacting the compound RSi(OSiMe 2 H) 3 with a dimethylcyclosiloxane in the presence of an acid catalyst and (iii) allowing the reaction to continue for a time sufficient for the reaction to reach a constant steady state condition. A method of making a compound of claim 1 having the formula [HMe 2 SiO(Me 2 SiO) x ] 2 SiRORSi[(OSiMe 2 ) x -OSiMe 2 H] 2 in which Me is methyl, R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent, and x has a value of 1-100, comprising (i) hydrolyzing an alkyltrichlorosilane with dimethylchlorosilane to form a compound of the formula (HMe 2 SiO) 2 SiRORSi(OSiMe 2 H) 2 , wherein Me is methyl, and R is a straight-chain or branched-chain alkyl substituent; (ii) reacting the compound (HMe 2 SiO) 2 SiRORSi(OSiMe 2 H) 2 with a dimethylcyclosiloxane in the presence of an acid catalyst; and (iii) allowing the reaction to continue for a time sufficient for the reaction to reach a constant steady state condition. A method according to any of claims 6 to 7 in which R is a C 2 to C 18 straight-chain or branched-chain alkyl substituent.

Inventors: COBB VICKY S, LEGROW GARY E, MCVANNEL DONALD E, NORRIS ANN W, COBB, VICKY S., LEGROW, GARY E., MCVANNEL, DONALD E., NORRIS, ANN W.
Applicants: DOW CORNING, DOW CORNING CORPORATION
Application year: 1995
Main classification: C07F7
IPC codes: C07F7, C08G77