MXPA00006189A - Organopolysiloxane materials which can be cross-linked by cleaving alcohols into elastomers - Google Patents

Abstract

The invention relates to a method for producing organopolysiloxane terminated with alkoxy groups, wherein A) organopolysiloxane terminated with HO is reacted with B) alkoxysilane having at least three alkoxy groups and/or whose partial hydrolysate is made to react in the presence of C) acid phosphoric acid ester of general formula (I):(HO)aOP(-O-[(CR12)b-O]c[(CR22)d]e-L-M)(3-a), wherein a=1 or 2;R1 and R2=a hydrogen, methyl or hydroxyl radical;b and d=2 or 3;c=integral values from 2 to 15;e=0 or 1;L=a radical from the group -O-, -COO-, -OOC-, -CONR3-, -NR4CO- and -CO-;R3 and R4=a hydrogen or a C1-C10-alkyl radical and M=a monovalent, optionally a hydroxyl, fluorine, chlorine, bromine, C1-C10-alkoxylalkyl or cyano group substituted C1- to C20-hydrocarbon radical, provided that the radicals R1 andR2 can only be at one given time a hydroxyl radical in each hydrocarbon atom. The invention further relates to RTV-1-alkoxy masses comprising the reaction product containing organopolysiloxane terminated with alkoxy groups as the essential constituent.

Description

COMPOSITIONS OF ORGANOPOLISILOXANE RETICULABLES TO GIVE ELASTOMERS WITH DETACHMENT OF ALCOHOLS The invention relates to the preparation of organopolysiloxane terminated with alkoxy groups and the use of this organopolysiloxane as a constituent of RTV-1-alkoxy compositions. In the context of the present invention, the term "organopolysiloxanes" is intended to encompass siloxanes, dimers, oligomers and polymers. Organopolysiloxane compositions, which are stable to storage in the absence of moisture and crosslink in the presence of moisture at room temperature with evolution of alcohols, so-called RTV-1 -alkoxy compositions, have been known for a long time. Said compositions are essentially composed of organopolysiloxane terminated with organoxy groups, and as additional constituents crosslinker with at least three hydrolyzable groups, catalyst and optionally additives. The advantage of these RTV-1-alkoxy systems is that they release free, neutral and environmentally compatible alcohols as dissociation products during the crosslinking process. The organopolysiloxane terminated with alkoxy groups is prepared by transformations of HO-terminated organopolysiloxane with alkoxysilanes. This is described, for example, in US-A-4,942.21 1. In this process, it is a disadvantage that the transformation requires several hours at room temperature. At higher temperatures, the reaction time is actually reduced, but it is still so long that it is necessary to wait until the organopolysiloxane formed with alkoxy groups and the RTV-1-alkoxy compositions can be further produced. The acceleration of the HO-terminated organopolysiloxane transformations with alkoxysilanes by different catalysts is known. For example, in EP-A-763 557 the transformation is carried out in the presence of acid esters of dialkylphosphoric acid. The dialkylphosphoric acid esters have to be deactivated by bases after the transformation, since otherwise the organopolysiloxanes terminated with alkoxy groups are depolymerized and their susceptibility to crosslinking is lost. The object of the invention is to prepare organopolysiloxane terminated with alkoxy groups for RTV-1-alkoxy compositions in the simplest possible manner. Object of the invention is a process for the preparation of organopolysiloxane terminated with alkoxy groups, in which (A) HO-terminated organopolysiloxane is reacted with (B) alkoxysilane of the general formula (III) R5μSi (OR6) 4-μ ( III), in which R5 and R6 mean monovalent C? -C- | 3 hydrocarbon radicals, optionally substituted with fluorine, chlorine, bromine, C? -C4 alkyloxy or cyano alkoxy groups and μ the values 0 or 1, and /? or their partial hydrolysates, in the presence of (C) phosphoric acid ester of the general formula (I) (HO) aOP (-O - [(CR12) bO] c (CR22) dLM) (3-a) (I ), in which they mean to the values 1 or 2, R1 and R2 a hydrogen, methyl or hydroxyl radical, b and d the values 2 or 3, c whole numerical values from 2 to 15, e the values 0 or 1, a remainder of the group -O-, -COO-, -OOC-, -CONR3-, -NR4CO- and -CO- R3 and R4 a hydrogen or C? -C10 alkyl radical and M a monovalent Ci to C20 hydrocarbon radical, optionally substituted with groups hydr oxyl, fluorine, chlorine, bromine, C-i-C-io-alkyl or cyano alkoxy, with the proviso that the radicals R1 and R2 at each carbon atom can only be once a hydroxyl radical. The process already proceeds at room temperature selectively with extremely high reaction rate, such that immediately after the mixing of the components (A), (B) and (C) the organopolysiloxane formed terminated in alkoxy groups, optionally after addition of other constituents, it can be used as composition RTV-1 -alkoxy. A control can be dispensed with as to whether the transformation has completely passed or not. An additional advantage of this process can be recognized in that no secondary reaction takes place, and for example the formation of T and Q units could not be observed in the linear organopolysiloxane. The acid esters of phosphoric acid (C) do not have to be deactivated immediately after the transformation. Preferably, c means integer values of 2 to 10, particularly 2, 3, 4 or 5. Preferably, L means an -O- moiety. Preferably, M means a C 1 to C 2 hydrocarbon radical optionally substituted with C 1 -C 6 alkoxy or alkyl groups, particularly an unsubstituted C 5 -C 18 hydrocarbon radical. Preferably, R1 and R2 mean a hydrogen moiety. Preferably, b and d denote the values 2. As organopolysiloxane terminated in HO (A), linear -dihydroxypoly- (diorganosiloxanes) of the general formula (II) HO- [R2SiO] mH (II) are preferably used, in which R means residues Ci-Cs hydrocarbons optionally substituted with fluorine, chlorine, bromine, C?-C4-alkyl or cyano alkoxy groups and m means values such that they correspond to a viscosity of the HO (A) -organized organopolysiloxane of 0.05 to 1000 Pa.s. Examples of hydrocarbon radicals R are unsaturated linear and cyclic alkyl radicals, such as the methyl radical, aryl radicals, such as the phenyl radical, alkaryl radicals, such as tolyl radicals and aralkyl radicals, such as the benzyl radical. As radical R, hydrocarbon radicals unsubstituted by 1 to 6 carbon atoms are preferred, with the methyl radical being particularly preferred. The organopolysiloxanes (A) preferably have a viscosity of 100 to 700,000 mPa.s, particularly of 20000 to 350000 mPa.s, determined in all cases at 23 ° C. The partial hydrolysates of the alkoxysilane (B) are produced by hydrolysis and condensation of particularly 2 to 4 alkoxysilanes. Partial hydrolysates (B) are for example hexametoxidisiloxane and hexaetoxydisiloxane. Preferably, R5 and R6 are in each case hydrocarbon residues Ci-Cβ unsubstituted, particularly methyl, ethyl and propyl residues. The acid esters of phosphoric acid (C) of the general formula (I) stabilize during storage the RTV-1-alkoxy compositions produced from the organopolysiloxane terminated in alkoxy groups. In particular, the skin formation times of the RTV-1-alkoxy compositions remain stable almost constantly and a color alteration is counteracted.

In the general formulas (I) to (III) all the residues R, R1 to R6 as well as all indices a, b, c, d, e, m and μ, independently of each other, are equal or different. In all the formulas, the tetravalence of the silicon atom is fulfilled. For example, n + o is at most 4. The acid esters of phosphoric acid (C) are added, based on 500 parts by weight of the organopolysiloxanes terminated in HO (A), in a proportion of 0.1 to 50 parts by weight , particularly 2 to 20 parts by weight. The addition of the alkoxysilanes (B) to the organopolysiloxanes terminated in HO (A) is preferably carried out in an excess referred to the stoichiometric ratios. To make the reaction of the organopolysiloxanes terminated in HO (A) with the alkoxysilanes (B) proceed as completely as possible, preferably 10 to 60 parts by weight, particularly up to 20 to 50 parts by weight, of the alkoxysilanes (B) can be used. per 500 parts by weight of the organopolysiloxanes terminated in HO (A). The excess of alkoxysilanes (B) which has not been consumed during the reaction does not represent a drawback in the organopolysiloxane terminated with organoxy groups and in the RTV-1-alkoxy compositions, and may thus remain in the product of the reaction. An excess of alkoxysilanes (B) acts as a crosslinking component in the RTV-1-alkoxy compositions. The transformation is preferably carried out at temperatures of +20 to + 50 ° C, particularly at room temperature. The reaction time is from 1 to 10 minutes depending on the alkoxysilanes (B) used.

The reaction rate during the transformation depends on one part on the reactivity of the alkoxysilane (B) used, and on the other on the acid phosphoric acid ester (C). The particularly preferred duration of the transformation is at room temperature 2-5 min, which is just advantageous for the production of RTV-1 compositions in the single-reactor process. The invention also relates to RTV-1-alkoxy compositions, which comprise the reaction product produced according to the preceding process, which contains as an essential constituent organopolysiloxane terminated with alkoxy groups. In addition to the components mentioned above, the RTV-1-alkoxy compositions may contain other components known per se. Additional materials, which can be used together in a preferable manner during the preparation of the RTV-1-alkoxy compositions are bis (trialkoxysilyl) -alkanes C? -C- | 2, in which the alkoxy radicals have the meanings of OR6, for example bis (triethoxysilyl) ethane. Also, during the manufacture of RTV-1-alkoxy compositions can be used condensation catalysts, reinforcing fillers, non-reinforcing fillers, pigments, soluble dyes, perfumes, plasticizers, such as dimethylpolysiloxanes blocked at the ends by trimethylsiloxy groups and fluids at the temperature environment, or esters of phosphoric acid, fungicides, resinous organopolysiloxanes, including those based on units (CH3) 3SiO? / 2 and SiO 2, pure organic resins, such as homo- or copolymers of acrylonitrile, styrene, vinyl chloride or propylene, wherein such pure organic resins, particularly copolymers of styrene and n-butyl acrylate, may have already been obtained in the presence of diorganopolysiloxane containing a hydroxyl group attached to Si in each of the terminal units by polymerization of the monomers mentioned by free radicals, corrosion inhibitors, polyglycols, which may be esterified and / or etherified, oxidation inhibitors, thermal stabilizers, solvents, agents for the modification of electrical properties, such as conductive carbon black, flame retardants, photostabilising agents and agents for the prolongation of the skin formation, such as silanes with mercaptoalkyl moieties attached to SiC, as well as cell forming agents, eg azodicarbonamide. Also, adhesion promoters may be added, preferably silanes with amino-alkyl functionality such as aminopropyltriethoxysilane. Advantageously, condensation catalysts are used. The RTV-1-alkoxy compositions may contain according to the invention any condensation catalysts, which could also be present up to now in compositions stable to storage in the absence of water and crosslinkable to give elastomers at room temperature with the addition of water which is have produced. Examples of such condensation catalysts are organic compounds of tin, zinc, zirconium, titanium and aluminum. Among these condensation catalysts, butyl thifonates and organic tin compounds are preferred, such as di-n-butyltin diacetate, di-n-butyltin dilaurate and transformation products of a silane containing per molecule at least two monovalent hydrocarbon radicals optionally substituted by an alkoxy group and bonded to silicon via oxygen as hydrolyzable groups or its oligomer with diorganotin diacylate, these valences being able to be all the valences of the tin atoms saturated by oxygen atoms of the grouping = SiOSn = or by monovalent organic residues bound through SnC. The RTV-1-alkoxy compositions preferably contain fillers.

Examples of fillers are non-reinforcing fillers, ie fillers with a BET surface of up to 50 m2 / g, such as quartz, diatomaceous earth, calcium silicate, zirconium silicate, zeolites, metal oxide powder, such as aluminum oxide , titanium, iron, or zinc, or their mixed oxides, barium sulfate, calcium carbonate, gypsum, silicon nitride, silicon carbide, boron nitride, glass and plastic powder, such as polyacrylonitrile powder; reinforcing fillers, ie fillers with a BET surface greater than 50 m2 / g, such as pyrogenicly produced silica, precipitated silica, carbon black, such as furnace and acetylene black and mixed silicon-aluminum oxides with higher BET surface area; fibrous loads, such as asbestos and fibers of plastic materials. The mentioned fillers can be hydrophobic, for example by treatment with organosilanes or -siloxanes or with stearic acid, or by etherification of hydroxyl groups to alkoxy groups. A single load class can be used, or a mixture of at least two loads can be used. By the exclusive use of reinforcing silica as filler, transparent RTV-1-alkoxy compositions can be produced. For the crosslinking of the RTV-1-alkoxy compositions, the normal water content of the air is sufficient. The crosslinking can be carried out, if desired, even at temperatures above or below room temperature, for example at -5 ° to 10 ° C or at 30 ° to 50 ° C. The RTV-1-alkoxy compositions according to the invention are therefore very suitable, for example, as gasket packing compositions, including vertical joints, and analogous empty spaces of, for example, 10 to 40 mm aperture, eg. of buildings, earth, water and air vehicles, or as adhesives or mastics, eg in the construction of windows or in the manufacture of showcases, as well as, for example, for the manufacture of protective coatings, or bodies conformed with elasticity similar to rubber, as well as for the isolation of electrical or electronic devices. In the examples described below, all parts data in percentages refer to the weight, if not otherwise indicated. Additionally, all viscosity data refer to a temperature of 25 ° C. Unless otherwise indicated, the examples set forth below are carried out at the pressure of the surrounding atmosphere, i.e. at approximately 1000 hPa, and at room temperature, i.e. at approximately 20 ° C, or at a temperature which it establishes itself by contacting the reactants at room temperature without further heating or cooling.

EXAMPLES EXAMPLE 1 In a planetary mixer with vacuum equipment, 500 g of a dimethylpolysiloxane, which has a hydroxyl group in each of the terminal units, with a viscosity of 80000 mPa.s at 23 ° C with 350 g of a polydimethylsiloxane are mixed in the absence of water. with trimethylsiloxy groups in the terminal units having a viscosity of 100 mm2 / s (23 ° C) and 10 g of alkoxylated phosphoric acid ester mixture of the formulas (OH) 1PO [(OCH2CH2) 3-4-O- ( CH2) ?? -? 4-CH3] 2 and (OH) 2PO [(OCH2CH2) MO- (CH2) 11-14-CH3) 1. Immediately afterwards, 25 g of methyltrimethoxysilane are added once and the mixture is homogenized under vacuum for 5 minutes. After that, the conventional mixing technique for RTV-1 compositions is added, in the order of succession indicated: 13.5 g of -aminopropyltriethoxysilane, 80.0 g of hydrophilic pyrogenic silica with a surface of 150 m2 / g according to BET and 5.0 g of a transformation product, which has been prepared by heating for 6 hours a mixture consisting of 4 parts of tetraethyl silicate and 2,2 parts of di-n-butyltin diacetate at 120 ° C. the pressure of the surrounding atmosphere with simultaneous stirring and distillation of the ethyl acetate formed. After vacuum homogenization, the composition is introduced in moisture proof containers. After various periods of time, samples are taken and the skin formation times (at 23 ° C / 50% relative humidity) of the elastomers thus produced are determined. The results obtained in this way are indicated in Table 1. The following mechanical properties of the elastomers have been determined: Shore A: 10; Breaking strength: 1.0 N / mm2; Elongation at break: 560%; resistance to progressive tearing: 2.7 N / mm; tensile stress for 100% elongation: 0.2 N / mm2.

EXAMPLE 2 The procedure is analogous to Example 1. To 600 g of dihydroxypolydimethylsiloxane of Example 1, the following ingredients are added by mixing in the sequence indicated: 280.0 g of polydimethylsiloxane with terminal groups -Si (CH3) 3, 10.0 g of alkoxylated phosphoric acid ester of Example 1, 25.0 g of vinyltrimethoxysilane, 15.0 g of -aminopropyltriethoxysilane, 70.0 g of hydrophilic pyrogenic silica with a surface area of 150 m2 / g according to BET and 5.0 g of the product of transformation of tetraethyl silicate and di-n-butyltin diacetate of Example 1. The times of skin formation of the elastomers thus produced are indicated in Table 1.

EXAMPLE 3 The procedure is analogous to Example 1. To 500 g of dihydroxypolydimethylsiloxane, the following ingredients are added by mixing in the sequence indicated: 380.0 g of polydimethylsiloxane with terminal groups -Si (CH3) 3, 10.0 g of acid ester alkoxylated phosphoric of Example 1, 25.0 g of methyltrimethoxysilane, 10.0 g of 3- (2-aminoethylamino) -propyltrimethoxysilane, 70.0 g of hydrophilic pyrogenic silica with a surface area of 150 m2 / g according to BET and 4.0 g of the transformation product of tetraethyl silicate and di-n-butyltin diacetate of Example 1. The skin formation times of the elastomers thus produced are indicated in Table 1.

EXAMPLE 4 The procedure is analogous to Example 1. The following are mixed: 500.0 g of, -dihydroxypolydimethylsiloxane of Example 1, 380.0 g of polydimethylsiloxane with terminal groups -Si (CH3) 3, 10.0 g of alkoxylated phosphoric acid esters of Example 1.25.0 g of methyltrimethoxysilane, 8.0 g of aminopropyltriethoxysilane, 70.0 g of hydrophilic fumed silica with a surface area of 150 m2 / g according to BET and 4.0 g of the tetraethyl silicate and diacetate conversion product of di-n-butyltin of Example 1. The skin formation times of the elastomers produced in this way are indicated in Table 1.

EXAMPLE 5 The procedure is analogous to Example 1. The following are mixed: 500.0 g of, -dihydroxypolydimethylsiloxane of Example 1, 380.0 g of polydimethylsiloxane with terminal groups -Si (CH3) 3, .0 g of alkoxylated phosphoric acid esters of Example 1, 25.0 g of vinyltrimethoxysilane, 25.0 g of aminofunctional siloxane: equilibrium reaction product of aminopropyltriethoxysilane and a condensate / hydrolyzate of methyltriethoxysilane with an amine number of 2. 2.70.0 g of hydrophilic pyrogenic silica with a surface area of 150 m2 / g according to BET and 5.0 g of the product of transformation of tetraethyl silicate and di-n-butyltin diacetate of Example 1. The formation times of the elastomers produced in this way are indicated in Table 1.

BOX 1 EXAMPLE 6 In a planetary mixer with vacuum equipment, 600 g of a polydimethylsiloxane are mixed in the absence of water, in each of which terminal units a hydroxyl group is present, and having a viscosity of 80,000 mPa.s at 23 ° C, 300 g of a polydimethylsiloxane with trimethylsiloxy groups as terminal units and having a viscosity of 100 mm2 / s at 23 ° C, and 10 g of the alkoxylated phosphoric acid ester of Example 1, until homogeneous. Immediately thereafter, 35 g of methyltrimethoxysilane are added and homogenized once more for 5 minutes. They are then added to this premix, respecting the conventional mixing technique for RTV-1 compositions, by stages and successively, the following ingredients: 15.0 g of -aminopropyltriethoxysilane, 70.0 g of hydrophilic fumed silica with a specific surface area of 150 m2 / g according to BET and 5.0 g of the product of transformation of tetraethyl silicate and di-n-butyltin diacetate of Example 1. After homogenization under reduced pressure, the composition is introduced in moisture-proof containers. After 1 day of storage at room temperature, a skin formation time of 10 minutes (23 ° C / 50% relative humidity) is determined. After an additional 7 days of storage at 50 ° C, a skin formation time of 15 minutes is obtained.

EXAMPLE 7 Example 6 is repeated. However, to the previous mixture of the same formulation, the additional ingredients are added, in order of modified succession: 70.0 g of hydrophilic pyrogenic silica with a specific surface area of 150 m2 / g according to BET, , 0 g of -aminopropyltriethoxysilane and 5.0 g of the transformation product of tetraethyl silicate and di-n-butyltin diacetate of Example 1. After homogenization under reduced pressure, the composition is filled into moisture-proof packages. After 1 day of storage at room temperature, a skin formation time of 12 minutes (23 ° C / 50% relative humidity) is determined. After an additional 7 days of storage at 50 ° C, a skin formation time of 15 minutes is obtained.

EXAMPLE 8 Example 6 is repeated. To the premix of the same formulation, the additional ingredients are added in the following manner: 70.0 g of hydrophilic pyrogenic silica with a specific surface area of 150 m2 / g according to BET and 5.0 g of the product of transformation of tetraethyl silicate and di-n-butyltin diacetate of Example 1. After homogenization under reduced pressure, the composition is left in storage for 3 hours in the absence of moisture and 15 g of aminopropyltriethoxysilane are then added. After further homogenization under reduced pressure, the composition is introduced into moisture-proof containers. After 1 day of storage at room temperature, a skin formation time of 12 minutes (23 ° C / 50% relative humidity) is determined. After storage for an additional 7 days at 50 ° C, a skin formation time of 15 minutes is obtained. Examples 6 to 8 indicate that the order of succession of the addition of the adhesion promoter-aminopropyltriethoxysilane exerts a negligible influence on the time of skin formation. Immediate neutralization of the alkoxylated phosphoric acid ester by the basic adhesion promoter is therefore not necessary.

EXAMPLE 9 In a planetary mixer with vacuum equipment, 550 g of a polydimethylsiloxane with terminal hydroxyl groups and a viscosity of 80,000 mPa.s at 23 ° C, 325 g of a polydimethylsiloxane with trimethylsiloxy end groups, 50 g are homogeneously mixed in the absence of water. of methyltrimethoxysilane and 10 g of the alkoxylated phosphoric acid ester of Example 1. After about 10 minutes the following ingredients are added and these are homogeneously incorporated by mixing into the total composition: 15.0 g of -aminopropyltriethoxysilane, 73.0 g of hydrophilic pyrogenic silica with a surface area of 150 m2 / g according to BET, 5.0 g of the product of transformation of tetraethyl silicate and di-n-butyltin diacetate of Example 1 and 200.0 g of ground chalk, treated with stearic acid . After 1 day of storage at room temperature, a skin formation time of 15 minutes is determined. After a further 7 days of storage at 50 ° C, a skin-forming time of 20 minutes is determined.

EXAMPLE 10 Example 9 has been repeated, but with the modification that instead of the milled chalk treated with stearic acid, the same amount of untreated ground chalk has been used. After 1 day of storage at room temperature, a skin-forming time of 20 minutes has been determined, and after an additional 7 days of storage at 50 ° C, a skin-forming time of 25 minutes has been determined.

EXAMPLE 11 Example 9 has been repeated, but with the modification that, instead of 73 g of hydrophilic fumed silica with a surface area of 150 m2 / g according to BET, only 50 g have been added, and instead of 200 g of chalk milled treated with stearic acid, the same amount of precipitated chalk was used, treated with stearic acid, which has a surface area of 19 m2 / g. After 1 day of storage at room temperature, a skin-forming time of 15 minutes has been determined, and after an additional 7 days of storage at 50 ° C, the skin formation time has amounted to 25 minutes.

EXAMPLE 12 The procedure is analogous to Example 1. The following sequence is mixed: 95.3 g of, -dihydroxypolydimethylsiloxane of Example 1, 1.2 g of alkoxylated phosphoric acid esters of Example 1 and 3.5 g of methyltrimethoxysilane. The viscosities of the mixture were determined: after 1 h: 64000 mPa.s after 2 h: 62400 mPa.s after 3 h: 60800 mPa.s.

EXAMPLE 13 (EXAMPLE OF COMPARISON) The procedure is analogous to Example 1. The following sequence is mixed: 95.3 g of, -dihydroxypolydimethylsiloxane of Example 1, 1.2 g of di-2-ethylhexyl phosphate (according to EP-A-763 557) and 3.5 g of methyltrimethoxysilane. The viscosities of the mixture were measured: after 1 h: 32000 mPa.s after 2 h: 12000 mPa.s after 3 h: 2000 mPa.s. Di-2-ethylhexyl phosphate depolymerizes the finished organopolysiloxane in alkoxy groups.

Claims (3)

NOVELTY OF THE INVENTION CLAIMS

1. - Process for the preparation of organopolysiloxane terminated with alkoxy groups, in which (A) HO-terminated organopolysiloxane is reacted with (B) alkoxysilane of the general formula (III) R5μSi (OR6) 4-μ (III). wherein R5 and R6 represent monovalent C -? - C? 3 hydrocarbon radicals, optionally substituted with fluorine, chlorine, bromine, C? -C -alkyl or cyano alkoxy groups and μ the values 0 or 1, and / or their hydrolysates parts, in the presence of (C) phosphoric acid ester of the general formula (I) (HO) aOP (-O - [(CR12) bo] c (CR22) dLM) (3-a) (I), in which mean to the values 1 or 2, R1 and R2 a hydrogen, methyl or hydroxyl radical, b and d the values 2 or 3, c numerical values from 2 to 15, e the values 0 or 1, L a rest of the group - O-, -COO-, -OOC-, -CONR3-, -NR4CO- and -CO-, R3 and R4 a hydrogen or C1-C10 alkyl radical and M a monovalent C1 to C20 hydrocarbon radical, optionally substituted with hydroxyl groups, fluorine, chlorine, bromine, C 1 -C 0 alkoxy-alkyl or cyano, with the proviso that the radicals R 1 and R 2 in each carbon atom can only be once a hydroxyl radical. X "

2. Process according to claim 1, in which linearly α, β-dihydroxypoly (diorgano) siloxanes of the general formula (II) HO- [R2S¡O] mH are used as organopolysiloxane terminated in HO (A). II), in which R stands for monovalent C -? - C8 hydrocarbon radicals optionally substituted with fluorine, chlorine, bromine, d-C4-alkyloxy or cyano groups and m means values such that they correspond to a viscosity of the HO-terminated organopolysiloxane (A ) from 0.05 to 1000 Pa.s 3.- RTV-1 -alkoxy compositions, which comprise the reaction product obtainable according to claim 1 or 2, which contains as an essential constituent organopolysiloxane terminated with alkoxy groups.