Polymerized Alkyl Silicate

Abstract

Polymerized alkyl silicates of formula (I) (where Z is a group of formula -Si(OR b )3 or a group represented by the formula -CR c 3, and R a represents an unsubstituted or substituted divalent carbon-bonded group or a divalent silicon-bonded group; R b represents an unsubstituted or substituted monovalent hydrocarbon group having 4 to 40 carbon atoms, which is branched at the α carbon atom or doubly branched at the β carbon atom; R c represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 50 carbon atoms, and X represents a halogen atom, an unsubstituted or substituted C1-C oxygen bond. 40 Hydrocarbon groups, C1-C, in which individual carbon atoms may be replaced by oxygen atoms. 40 Hydrocarbon radicals, formula -O-Si(OR b ) 3 or a group represented by the formula -OSiR x 3, and R X is an unsubstituted or substituted monovalent C1-C 40 represents a hydrocarbon group, and m represents an integer of at least 2 and at most 1000.

Description

[Technical field]

[0001] The present invention relates to novel polymerized alkyl silicates. [Background technology]

[0002] Silicones are a class of materials of great industrial importance that are used in many technical fields. An industrially important property of silicones is, for example, their low tendency to crystallize, which distinguishes them from carbon-based polymers. Silicones remain liquid over a wide temperature range and have a very low glass transition temperature. However, due to the presence of alkyl moieties in the Si bonds, silicones are not easily decomposed in the environment at all. This characteristic increasingly limits the potential applications of silicones. Therefore, there is a steadily growing demand for alternative materials that can replace traditional silicones, which in principle can be hydrolyzed but have sufficient hydrolytic stability for practical use.

[0003] Patent documents 1 and 2 disclose a compound represented by the formula [(R a O)3SiO]3Si-O-KW-O-Si[OSi(OR a )3]3 (wherein KW represents a hydrocarbon group). However, these systems have a low molecular weight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Pat. No. 3,992,429 [Patent Document 2] U.S. Pat. No. 4,132,664 Summary of the Invention

[0005] However, in many technical applications, small molecule compounds are undesirable due to their volatility and migration.

[0006] It is therefore an object of the present invention to provide a polymerized alkyl silicate which overcomes the above-mentioned drawbacks and has similar properties to silicone and can therefore replace silicone.

[0007] The present invention achieves the above object.

[0008] The present invention relates to a compound of formula (I): [ka] (In the formula, Z is a group of the formula -Si(OR b ) 3, or a group represented by the formula -CR c 3 represents a group represented by R a represents independently in each occurrence an unsubstituted or substituted divalent carbon-bonded group or a divalent silicon-bonded group; R b represents, independently in each occurrence, an unsubstituted or substituted monovalent hydrocarbon radical having 4 to 40 carbon atoms which is branched at the α carbon atom or doubly branched at the β carbon atom; R c represents independently in each occurrence an unsubstituted or substituted monovalent hydrocarbon group having 1 to 50 carbon atoms (preferably, 1 to 10 carbon atoms, preferably, 1 to 5 carbon atoms); X is a halogen atom, an unsubstituted or substituted C1-C oxygen bond 40 Hydrocarbon groups, C1-C, in which individual carbon atoms may be replaced by oxygen atoms. 40 Hydrocarbon radicals, formula -O-Si(OR b ) 3, or a group represented by the formula -OSiR x 3 represents a group represented by R X is independently in each occurrence an unsubstituted or substituted monovalent C1-C 40 represents a hydrocarbon group, m represents an integer of at least 2 (preferably at least 5) and at most 1000 (preferably at most 500, preferably at most 100); The present invention provides a polymerized alkyl silicate represented by the formula: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The term "branched" means that there are two carbon groups on one carbon atom. The term "doubly branched" means that there are three carbon groups on one carbon atom.

[0010] base R a , R b , R c and R x and the group X (when X is not a halogen atom) may be acyclic, cyclic, saturated, or mono- or polyunsaturated, or aromatic, and may have the following substituents: -OR 1 , -NR 1 2, -SH, -SR 1 , epoxy group, -COOR 1 , -CHO, -CN, -OCOOR 2 , -NR 1 -COOR 1 , -NR 1 -CO-NR 1 , -SiR 1 3 and -OSiR3 1 (In the formula, R 1 is a hydrogen atom or a monovalent C1-C 18 represents a hydrocarbon group, R 2 is a monovalent C1 to C 18 represents a hydrocarbon group)

[0043]

[0011] R a is, independently in each occurrence, preferably a divalent hydrocarbon radical having 1 to 200 carbon atoms (preferably having 3 to 50 carbon atoms), wherein a carbon atom is separated by an oxygen atom or by the formula -(R y 2SiO)o -SiR y A hydrocarbon group which may be substituted by a siloxanyl group represented by the formula: R y independently in each occurrence, C1 through C 20 represents a hydrocarbon group (preferably a C1 to C6 hydrocarbon group), o is an integer of 0 to 100 (preferably an integer of 0 to 20) Represents.

[0012] base R a Examples are 1,3-propylene, 1,4-butylene, 1,2-cyclohexylidene, 1,3-cyclohexylidene, 1,4-cyclohexylidene, 1,2-phenylene, 1,3-phenylene and 1,4-phenylene. base R a Further examples include those of the formula: -CHR 3 -CHR 3 -(OCHR 3 -CHR 3 ) p - (In the formula, R 3 is a hydrogen atom or a C1-C 18 represents a hydrocarbon group (preferably a hydrogen atom or a methyl group); p is an integer of 0 to 100 (preferably an integer of 0 to 20) as well as groups of the formula: -(Me2SiO) o -Me2Si- -CH2-CH2-CH2-(Me2SiO) o -Me2Si-CH2-CH2-CH2-, and -CH2-(Me2SiO) o -Me2Si-CH2- (In the formula, Me is a methyl group; o is as defined above) It is a group represented by the following formula:

[0013] R bPreferred examples of the alkyl group include a 2-butyl group, a 3-methyl-2-butyl group, a 3-methyl-2-pentyl group, a 3-pentyl group, a 2-hexyl group, a 3-hexyl group, a 2-heptyl group, a 2-octyl group, a 1-phenylethyl group, a 1-phenyl-1-propyl group, a 2,2-dimethyl-1-propyl group, a 1,1-dimethylethyl group, and a 1,1-dimethylpropyl group.

[0014] R c represents, independently in each occurrence, preferably a linear or branched acyclic hydrocarbon group having 1 to 50 carbon atoms, preferably a linear or branched acyclic hydrocarbon group having 1 to 10 carbon atoms, particularly preferably a linear or branched acyclic hydrocarbon group having 1 to 5 carbon atoms.

[0015] R c Examples are the methyl group, the ethyl group, the n-propyl group, the n-butyl group, the n-pentyl group, the vinyl group and the allyl group.

[0016] X is preferably a chlorine atom, an unsubstituted or substituted C1-C oxygen bond. 40 Hydrocarbon groups, C1-C, in which individual carbon atoms may be replaced by oxygen atoms. 40 Hydrocarbon radicals or groups of the formula -O-Si(OR b )3 or formula -OSiR x 3 (wherein, R X is, independently at each occurrence, preferably C1 to C 10 represents a hydrocarbon group).

[0017] Examples of groups X are a chlorine atom, a 4-hydroxycyclohexyloxy group, and groups of the formula: -O-(CH2-CH2) r -OH and -O-(CH2-CH2) r -OCH3 (in the formula, r=1~20) -O-Si(CH3)3, -O-Si(2-BuO)3, -O-SiH(CH3)2, -O-Si(CH3)2-CH2-CH2-CH2-NH2, -O-Si(CH3)2-CH2-CH2-CH2-NH-CH2-CH2-NH2, -O-Si(CH3)2-CH=CH2, and -O-Si(CH3)2-CH2-CH2-CH2-O-CH2-epoxy It is a group represented by the following formula:

[0018] Preferred examples of groups Z are groups of the formula (2-BuO)3SiO- and CH3-CH2-C(CH3)2O-, where 2-Bu is a 2-butyl group. Further examples of groups Z include those of the formula: [CH3-CH(CH3)-CH(CH3)O]3SiO-, [CH3-C(CH3)2-CH2O]3SiO-, [(CH3-CH2)2-CHO]3SiO-, [CH3-(CH2)3-CH(CH3)O]3SiO-, [CH3-(CH2)2-CH(C2H5)O]3SiO-, (CH3)3CO-, (C2H5)3CO-, (n-C3H7)3CO-, (n-C4H9)3CO-, (n-C5H 11 )3CO-, and CH3-CH2-C(CH3)2O- It is a group represented by the following formula:

[0019] The compound represented by the general formula (I) can be, for example, b O)3SiO]2SiCl2 or (R c 3CO)2SiCl2 and the dihydroxy compound HO-R a -OH(in the formula, R a , R b and R c can be prepared in a simple manner by reaction with an excess of [(R a O)3SiO]2SiCl2 or (R cWhen 3CO)2SiCl2 is present, silicates of formula I with X=Cl are preferentially formed, and when an excess of dihydroxy compound is present, X=OR. a The silicates of formula I having --OH groups are preferentially formed.

[0020] A further option is to react the Si-Cl end groups present after the reaction with alcohols or silanols.

[0021] The present invention therefore relates to a process for the preparation of a polymerized alkylsilicate according to the invention, comprising the steps of: [(R b O)3SiO]2SiCl2, or (R c 3CO)2SiCl2 With a chlorosilane (1) represented by the formula: H.O.R. a -OH or a salt thereof, Here, the dihydroxy compound (2) is used in an amount of 0.1 to 10 mol (preferably 0.5 to 1.5 mol) of the dihydroxy compound (2) per mol of the chlorosilane (1), R a , R b and R c are each as defined above. The present invention provides a method comprising the steps of:

[0022] Examples of chlorosilanes (1) are: [(2-BuO)3SiO]2SiCl2, {[CH3-CH(CH3)-CH(CH3)O]3SiO}2SiCl2, {[CH3-CH2-CH(CH3)-CH(CH3)O}3SiO]2SiCl2, {[(CH3-CH2)2CHO]3SiO}2SiCl2, {[CH3-(CH2)3-CH(CH3)O]3SiO]2SiCl2, {[CH3-(CH2)2-CH(C2H5)O]3SiO]2SiCl2, {[PhCH(CH3)O]3SiO]2SiCl2, {[PhCH(C3H7)O]3SiO]2SiCl2, {[CH3-CH(CH3)2-CH2O]3SiO}2SiCl2, {[CH3-CH(CH3)2O]3SiO}2SiCl2, {[CH3-CH2-CH(CH3)2O]3SiO}2SiCl2, [(CH3)3CO]2SiCl2, [(C2H5)3CO]2SiCl2, [(n-C3H7)3CO]2SiCl2, [(n-C4H9)3CO]2SiCl2, [(n-CH 11 )3CO]2SiCl2, and [CH3-CH2-C(CH3)2O]2SiCl2 (In the formula, 2-Bu is a 2-butyl group, and Ph is a phenyl group.) It is.

[0023] Preferred examples of chlorosilanes (1) are those of the formula: [(2-BuO)3SiO]2SiCl2, and [CH3-CH2-C(CH3)2O]2SiCl2 (wherein 2-Bu is a 2-butyl group). This is shown by:

[0024] Examples of the dihydroxy compound (2) are Ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 2,4-pentanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-dihydroxybenzene, 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, polyethylene glycol, polypropylene glycol, HO-SiMe2-(O-SiMe2) x -OH, and HO-CH2-CH2-CH2-SiMe2-(O-SiMe2) x -CH2-CH2-CH2-OH (In the formula, x is an integer of 1 to 50, and Me is a methyl group.) It is.

[0025] Preferred examples of the dihydroxy compound (2) are 1,4-cyclohexanediol, ethylene glycol, propylene glycol, triethylene glycol and polyethylene glycol.

[0026] The hydrogen chloride formed during the reaction may be removed directly from the reaction mixture by distillation or extraction, or a hydrogen chloride tolerant base or the dihydroxy compound in the form of a salt is used. Nitrogen bases are preferred.

[0027] Examples of bases are pyridine, ammonia, urea, diethylurea, ethylenediamine, methylamine, ethylamine, triethylamine, diethylamine, tributylamine, piperidine, pyrimidine, pyridazine, imidazole and diethylenetriamine.

[0028] Preferred examples of the base (3) are pyridine, ammonia, urea, ethylenediamine, triethylamine and tributylamine.

[0029] The process according to the invention may be carried out in the presence of one or more solvents. Examples of solvents are hydrocarbons such as toluene or isohexane, ethers such as methyl tert-butyl ether, or siloxanes such as hexamethyldisiloxane, octamethyltrisiloxane or (Me3SiO)4Si (where Me=methyl). The solvents are preferably used in a weight proportion of at least 1% and at most 100 times by weight (particularly preferably at least 10% and at most 10 times by weight), in each case based on the total weight of components (1) and (2).

[0030] The process may be carried out as a batch, semi-batch, or continuous process. In a semi-batch process, component (2) is preferably charged first (optionally with a base), and then component (1) is added.

[0031] In a further embodiment, the polymerized alkyl silicate of general formula (I), wherein Z is a group of formula -CR c The preparation of the group represented by the formula (3) can be carried out by Tetrachlorosilane is reacted with a compound of the formula: HO-CR c 3 and a monohydroxy compound (4) represented by the formula: H.O.R. a -OH or a salt thereof, simultaneously in one step or sequentially in two steps; Here, the monohydroxy compound (4) is used in an amount of 1.5 to 3.0 mol (preferably, 1.8 to 2.2 mol) per mol of tetrachlorosilane, and the dihydroxy compound (2) is used in an amount of 1.5 to 3.0 mol (preferably, 1.8 to 2.2 mol) per mol of tetrachlorosilane, R a and R c is as defined above, This is accomplished by. For this purpose, for example, 1 mol of tetrachlorosilane is mixed with 2 mol of HO-CR c 3 and 2 mol of dihydroxy compound (2). c It is preferred that 3 is added first and the dihydroxy compound (2) is added thereafter.

[0032] The process according to the invention is preferably carried out at temperatures between -20°C and +250°C, preferably between +20°C and +150°C. It may also be carried out at ambient atmospheric pressure (about 1020 hPa) or at higher or lower pressures. It may preferably be carried out at ambient atmospheric pressure.

[0033] The polymerized alkylsilicate according to the present invention preferably has a molar weight Mn (number average) of 5,000 to 50,000 and a molar weight Mw (weight average) of 10,000 to 100,000.

[0034] Molecular weights are determined by gel permeation chromatography (exclusion chromatography) using Agilent MesoPore and OligoPore columns (length 300 mm, internal diameter 7.5 mm, particle size 3 / 6 mm at 35° C.), eluent toluene, flow rate 0.3 ml / min, RI-detector, and polydimethylsiloxane calibration.

[0035] The alkyl silicates of formula (I) according to the invention have the advantage compared to the prior art that they are polymeric and therefore non-volatile, and therefore do not migrate into materials. Moreover, they are liquid and have a very low glass transition temperature despite their high molecular weight, and therefore are suitable for replacing silicones. A further advantage of the alkyl silicates of formula (I) according to the invention is that they have a modular structure, and therefore their molecular weight can be modified as desired. Furthermore, the chain ends of the alkyl silicates according to the invention have reactive groups (e.g. chlorine or hydroxyl groups) to which a large number of further optional functionalization sites can be attached. This makes it possible to broaden the scope of application of the alkyl silicates according to the invention.

[0036] The polymerized alkyl silicates according to the invention can, for example, be subjected to further processing (e.g., crosslinking to obtain elastomers) and used wherever silicones are used (e.g., in the hydrophobizing, antifoaming, textile, cosmetic, building preservative and household care fields). EXAMPLES

[0037] The compound used in the examples, [(2-BuO)3SiO]2SiCl2, is prepared from (2-BuO)3SiOH and SiCl4 as described, for example, in Abe, Bull. Soc. Chim. Jpn. 1969, 42, 111-1123.

[0038] The compound used in the examples, [CH3-CH2-C(CH3)2O]2SiCl2, is prepared from CH3-CH2-C(CH3)2OH and SiCl4 as described, for example, in Docherty et al., Helv. Chim. Acta 2018, 101, e1700298.

[0039] Example 1: A polymer represented by formula (I) (wherein R a = 1,4-cyclohexylidene, Z = Si(OR b )3 (where R b = 2-Butyl), X = Cl, O-CH 10 -OH, m=14). 1.54 g (2.44 mmol) of [(2-BuO)3SiO]2SiCl2 in 0.5 ml of toluene is added dropwise to a mixture of 284 mg (2.44 mmol) of 1,4-cyclohexanediol and 430 mg (5.43 mmol) of pyridine in 1 ml of toluene. A white precipitate of pyridinium hydrochloride is formed. The mixture is then heated to 100° C. for 4 hours. The solution comprises a polymerized product with Mn=10000 Da / Mw=21000. This gives m=14. The precipitate of pyridinium hydrochloride formed is filtered off and the toluene is removed by rotary evaporation under vacuum. This gives a colorless oil with a dynamic viscosity at 25° C. of n=1.13 Pa·s. Glass transition temperature Tg=−107.6° C. 29 Si-NMR (CD2Cl2): δ=-92.5 and -98.6 ppm (2:1 ratio).

[0040] Example 2: A polymer represented by formula (I) (wherein R a =-CH2-CH2-(O-CH2-CH2)2-, Z=Si(OR b )3 (where R b = 2-butyl), X = -CH2-CH2-(O-CH2-CH2)2-OH, m = 13). 3.07 g (93%, 4.56 mmol) of [(2-BuO)3SiO]2SiCl2 is mixed with 1 ml of toluene. A mixture of 737 mg (4.91 mmol) of triethylene glycol, 856 mg (10.8 mmol) of pyridine, and 0.5 ml of toluene is slowly added to the solution. A white precipitate of pyridinium hydrochloride is immediately formed. The mixture is then heated to 100° C. for 4 hours. The solution comprises a polymerized product with Mn=9700 Da / Mw=22000. This gives m=13. 29 Si-NMR (CD2Cl2): δ=-92.3 and -96.8 ppm (2:1 ratio).

[0041] Example 3: A polymer represented by formula (I) (wherein R a =-CH2-CH2-(O-CH2-CH2)2-, Z=Si(OR b )3 (where R b = 2-butyl), X = -CH2-CH2-(O-CH2-CH2)2-OH, m = 13). The procedure of Example 2 is repeated at room temperature. After 3 hours, M n =12000Da / M w = 24000 Da polymer is formed. This gives m=13.

[0042] Example 4: A polymer represented by formula (I) (wherein R a =-CH2-CH2-(O-CH2-CH2)2-, Z=-C(CH3)2-CH2-CH3, X=CH2-CH2-(O-CH2-CH2)2-OH, Cl) The procedure of Example 2 is repeated, except that instead of [(2-BuO)3SiO]2SiCl2 a compound of formula [CH3-CH2-C(CH3)2O]2SiCl2 is used, the molar ratio is [CH3-CH2-C(CH3)2O]2SiCl2:triethylene glycol=1.0, and the reaction is carried out at 80° C. After 4 hours at 80° C. a polymer is formed with Mn=15500 Da / Mw=38300 Da, and after another 5 hours at 80° C. the mixture is worked up as described in Example 1. 6.2 g of polymerized product is obtained as a colorless oil. M n =16900Da / M w = 42400 Da. This gives m = 48. 29 Si-NMR (CD2Cl2): δ=-89.72ppm.

Claims

1. Formula (I): 【Chemical 1】 (In the formula, Z is a compound of the formula (2-BuO) ３ Si- or CH ３ -CH ２ -C(CH ３ ) ２ represents a group represented by -, R ａ is independently in each occurrence a divalent hydrocarbon radical having 3 to 200 carbon atoms, said carbon atoms being separated by an oxygen atom or by the formula -(R ｙ ２ SiO) ｏ -SiR ｙ ２ a hydrocarbon group optionally substituted with a siloxanyl group represented by the formula: R ｙ independently in each occurrence, C １ ~C ２０ represents a hydrocarbon group, o is an integer from 0 to 100. represents R ｂ represents, independently in each occurrence, an unsubstituted or substituted monovalent hydrocarbon radical having 4 to 40 carbon atoms, which is branched at the α carbon atom or doubly branched at the β carbon atom; R ｃ represents independently in each occurrence an unsubstituted or substituted monovalent hydrocarbon radical having 1 to 50 carbon atoms; X is a halogen atom, an unsubstituted or substituted oxygen-bonded C １ ~C ４０ Hydrocarbon groups in which individual carbon atoms may be replaced by oxygen atoms, C １ ~C ４０ Hydrocarbon groups, the formula -O-Si(OR ｂ ) ３ or a group represented by the formula -OSiR ｘ ３ represents a group represented by R Ｘ is independently in each occurrence an unsubstituted or substituted monovalent C １ ~C ４０ represents a hydrocarbon group, m represents an integer of at least 2 and at most 1000. Polymerized alkyl silicate represented by the formula:

2. 2. The polymerized alkylsilicate of claim 1, wherein m is an integer of at least 5 and at most 100.

3. group R ａ is a 1,3-propylene group, a 1,4-butylene group, a 1,2-cyclohexylidene group, a 1,3-cyclohexylidene group, a 1,4-cyclohexylidene group, a 1,2-phenylene group, a 1,3-phenylene group, a 1,4-phenylene group, and a group of the formula: -CHR ３ -CHR ３ -(OCHR ３ -CHR ３ ) ｐ -、 -(Me ２ SiO) ｏ -Me ２ Si-、 -CH ２ -CH ２ -CH ２ -(Me ２ SiO) ｏ -Me ２ Si-CH ２ -CH ２ -CH ２ -、 and -CH ２ -(Me ２ SiO) ｏ -Me ２ Si-CH ２ , (In the formula, Me is a methyl group; R ３ is a hydrogen atom or C １ ~C １８ represents a hydrocarbon group, o is as defined in claim 1; p is an integer from 0 to 100.

3. The polymerized alkyl silicate according to claim 1, wherein the alkyl silicate is a group selected from the group consisting of groups represented by the formula:

4. group R ｂ is selected from the group consisting of a 2-butyl group, a 3-methyl-2-butyl group, a 3-methyl-2-pentyl group, a 3-pentyl group, a 2-hexyl group, a 3-hexyl group, a 2-heptyl group, a 2-octyl group, a 1-phenylethyl group, a 1-phenyl-1-propyl group, a 2,2-dimethyl-1-propyl group, a 1,1-dimethylethyl group, and a 1,1-dimethylpropyl group.

5. R ｃ 5. The polymerized alkylsilicate of any one of claims 1 to 4, wherein, independently in each occurrence, represents a linear or branched acyclic hydrocarbon group having from 1 to 10 carbon atoms.

6. A method for producing the polymerized alkyl silicate of any one of claims 1 to 5, comprising the step of: [(R ｂ O) ３ SiO] ２ SiCl ２ , or (R ｃ ３ パ) ２ SiCS ２ Chlorosilane (1) represented by the formula: HO-R ａ -OH or a salt thereof, wherein the dihydroxy compound (2) is used in an amount of 0.1 to 10 mol per 1 mol of the chlorosilane (1); R ａ , R ｂ and R ｃ is as defined in claim 1 method.

7. The chlorosilane (1) used has the formula: [(2-BuO) ３ SiO] ２ SiCl ２ , or [CH ３ -CH ２ -C(CH ３ ) ２ O] ２ SiCS ２ (wherein 2-Bu is a 2-butyl group) The method of claim 6, wherein

8. The method according to claim 6 or 7, wherein the dihydroxy compound (2) used is 1,4-cyclohexanediol, propylene glycol, triethylene glycol or polyethylene glycol.

9. 9. The method of claim 6, 7 or 8, wherein the reaction is carried out in the presence of a base (3).

10. 10. The process according to claim 9, wherein the base (3) used is pyridine, ammonia, urea, ethylenediamine, triethylamine or tributylamine.

11. A polymerized alkyl silicate represented by formula (I) according to any one of claims 1 to 3, wherein Z is a group represented by the formula -CR ｃ ３ a method for preparing a compound represented by the formula Tetrachlorosilane is reacted with a compound of the formula: HO-CR ｃ ３ and a monohydroxy compound (4) represented by the formula: HO-R ａ -OH or a salt thereof in one step simultaneously or in two steps sequentially, wherein the monohydroxy compound (4) is used in an amount of 1.5 to 3.0 mol per 1 mol of tetrachlorosilane, and the dihydroxy compound (2) is used in an amount of 1.5 to 3.0 mol per 1 mol of tetrachlorosilane; R ａ and R ｃ is as defined in claim 1 method.

12. R ｃ 12. The method of claim 11, wherein, independently in each occurrence, represents a straight or branched chain acyclic hydrocarbon group having from 1 to 10 carbon atoms.

13. 13. The method according to claim 11 or 12, wherein the reaction is carried out in the presence of a base (3).

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