DE10227590B4 - To bleed-free elastomers condensation-crosslinkable organopolysiloxane - Google Patents

Abstract

Condensable crosslinkable organopolysiloxane compositions (M) containing as plasticizer diorganopolysiloxane (W) of the general formula (I) R 3 Si (O-SiR 1 2) n -OSiR 3 (I), in the R and R 1 monovalent unsubstituted C 1 -C 8 -hydrocarbon radicals , C1-C8 hydrocarbon radicals substituted with fluorine, chlorine or bromine atoms or C1-C4-alkoxyalkyl or cyano groups, and n denotes values of 6 to 15, the viscosity of the organopolysiloxane (W) being from 5 to 25 mm2 / s at 25 ° C is.

Description

The invention relates by condensation to bleed-free elastomers crosslinkable organopolysiloxane compositions containing as plasticizer low molecular weight diorganopolysiloxane.

Organopolysiloxane compositions which can be crosslinked by condensation to form elastomers have long been used for sealing joints in façade and window construction, in the sanitary and in the technical-industrial field. However, the use of such compositions is limited when the organopolysiloxane elastomers are in contact with absorbent materials.

Because the organopolysiloxane elastomers generally contain ingredients that are not incorporated into the high molecular elastomer network, they may migrate into contact with absorbent materials. This emigration leads to contamination of the contact materials in the edge region, recognizable by the formation of dark edge strips.

Examples of absorbent materials are in particular natural stones such as marble, granite, quartzite and sandstone, but also wood materials that are untreated or pretreated with open-cell coating materials. The main constituents in organopolysiloxane elastomers are plasticizers such as triorganosiloxy groups as organopolysiloxanes or hydrocarbon-based softeners as terminal units DE-AS-2364856 . DE-AS-2802170 . DE-AS-2908036 . DE-OS-3323911 . DE-OS-3329877 . DE-PS-3342026 . EP-A-218 875 . EP-A-801101 . DE-A-19620100 . EP-A-842 974 and EP-A-885 921 are called.

The hydrocarbon-based softeners exhibit greater volatility as compared to the organopolysiloxane-based plasticizers, i. H. they evaporate from the elastomers. In addition, they are often less UV-stable, which can lead to yellowing of the vulcanizates.

In order to use Organopolysiloxanelastomere for sealing joints between absorbent building materials, they must be prepared without plasticizer. However, this results in mixtures which are viscous in the uncured state and can be processed poorly, and have a hard-elastic properties in the vulcanized state, d. H. the vulcanizates have a high stress value when stretched. This is undesirable in many applications as a joint sealant, since the high forces that occur on the joint flanks when stretched cause premature detachment of the elastomer, ie. H. Adhesive loss can cause. In addition, building materials with low intrinsic strength such as plaster or aerated concrete in the joint flank area can tear out and be destroyed.

It is therefore a long-standing task to produce bleed-free organopolysiloxane elastomers with low stress values when stretched.

As far as organopolysiloxane elastomers are concerned, their tendency to self-contamination, i. H. to absorb debris from the environment of the elastomer on the surface of the elastomer to be reduced, this object has been achieved in that the elastomers various additives are added.

Additives of this type are organopolysiloxane resins, drying oils, ie reaction products of unsaturated fatty acids and alcohols such. As wood oil, fluorocarbons and fluorinated organopolysiloxanes or UV-curing oligomers with acrylic groups such as polyester acrylates, epoxy acrylates or urethane acrylates. Additives of this type are described, for example, in DE-PS-2059109 . DE-AS-2059112 . US-A-4395443 . EP-A-92044 . US-A-4460740 . DE-OS-3423770 . EP-A-131446 . EP-A-135293 . US-A-4495340 . US-A-4496696 . US-A-4500584 . US-A-4695603 . EP-A-562878 . US-A-5254657 . EP-A-587 295 . US-A-5326816 . EP-A-626426 . EP-A-799 860 . US-A-5840805 and US-A-6265516 ,

In addition, special crosslinkable organopolysiloxanes having functional groups such as carboxyl, sulfonate, polyglycol, amino, epoxy or imidazolyl be used. These last-mentioned special organopolysiloxanes or copolymers with organic radicals, as described for example in the EP-A-81119 , of the EP-A-210 442 and the US-A-5093389 can also be used for the production of plasticizer-free elastomers, which then not only accumulate little dirt from the ambient atmosphere at the surface, but are also free from bleeding. Due to the absence of plasticizer, however, they have the disadvantage that they are hard-elastic. In addition, their production is complex and expensive.

In the WO 00/47680 discloses hydroxy-terminated isocyanate-free urethane prepolymers prepared by reacting polyol with an isocyanate. These can be used as plasticizers in organopolysiloxane compositions which crosslink to form elastomers. The elastomers are free from bleeding. However, the use of urethane prepolymers in organopolysiloxane compositions reduces their weatherability. In addition, they tend to yellow.

In the DE 198 09 548 A1 RTV-1 compositions which can be crosslinked at room temperature by condensation are disclosed which comprise liquid dimethylpolysiloxanes endblocked by trimethylsiloxy groups as plasticizers. In the examples, these plasticizers have a viscosity of 100 mm ² / s.

DE 699 00 044 T2 describes RTV-1 compositions containing as plasticizers liquid dimethylpolysiloxanes with trimethylsiloxy groups. In the examples, these plasticizers have a viscosity of 100 cSt.

DE 43 40 400 A1 describes a mixture of condensable group-containing organopolysiloxane, organo-polysiloxane resin and basic nitrogen-containing compound.

The invention relates to condensation-crosslinkable organopolysiloxane compositions (M) which, as plasticizers, are diorganopolysiloxane (W) of the general formula (I) R ₃ Si (O-SiR ¹ ₂ ) _n -OSiR ₃ (I), included in the
R and R ¹ are monovalent unsubstituted C ₁ -C ₈ hydrocarbon radicals substituted by fluorine, chlorine or bromine atoms or C ₁ -C ₄ -alkoxyalkyl or cyano groups, C ₁ -C ₈ hydrocarbon radicals and
n is from 6 to 15, the viscosity of the organopolysiloxane (W) being from 5 to 25 mm ² / s at 25 ° C.

The condensation-crosslinkable organopolysiloxane compositions (M) crosslink to non-bleeding elastomers with low stress values on elongation, since they contain diorganopolysiloxane (W) as plasticizer.

The molecular weight of the diorganopolysiloxanes (W) is preferably at most 1100. n denotes values of 6 to 15, in particular 8 to 12.

The viscosity of the diorganopolysiloxanes (W) is preferably 5 to 15 mm ² / s, more preferably 8 to 12 mm ² / s.

Diorganopolysiloxanes (W) with a viscosity below 5 mm ² / s are too volatile and disadvantageously increase the shrinkage of the organopolysiloxane elastomers prepared therefrom. Diorganopolysiloxanes (W) with a viscosity of more than 25 mm ² / s migrate from the organopolysiloxane elastomers produced therewith into porous contact materials and contaminate them to form unsightly, dark colored edge stripes.

Examples of hydrocarbon radicals R and R ¹ are linear and cyclic saturated and unsaturated 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.

Preferred radicals R and R ¹ are unsubstituted hydrocarbon radicals having 1 to 6 carbon atoms, the methyl radical being particularly preferred. Preferably, R and R ^{1 are} the same radicals.

Organopolysiloxane compositions (M) can be present in one or more components. Preference is given to two-component and one-component compositions, in particular organopolysiloxane compositions which can be crosslinked at room temperature (RTV compositions). The crosslinkable organopolysiloxane compositions (M) are preferably crosslinkable with atmospheric moisture (RTV-1 compositions).

Preferred are RTV-1 organopolysiloxane compositions (M) which are obtainable by mixing diorganopolysiloxane (W), α, ω-dihydroxypolydiorganosiloxane (A), crosslinker (B) and filler (C).

As α, ω-Dihydroxypolydiorganosiloxan (A) are preferably linear α, ω-Dihydroxypolydiorganosiloxanes of the general formula (II) HO- [R ² ₂ SiO] _m -H (II), used in which
R ² denotes monovalent C ₁ -C ₈ -hydrocarbon radicals which are optionally substituted by fluorine, chlorine or bromine atoms or C ₁ -C ₄ -alkoxyalkyl or cyano groups, and
m means values corresponding to a viscosity of the HO-terminated organopolysiloxane (A) of 0.05 to 1000 Pa · s at 25 ° C.

Examples of hydrocarbon radicals R ² are linear and cyclic saturated and unsaturated 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.

Preferred radicals R ² are unsubstituted hydrocarbon radicals having 1 to 6 carbon atoms, the methyl radical being particularly preferred.

Preferably, R, R ¹ and R ^{2 are the} same.

The organopolysiloxanes (A) preferably have a viscosity of from 100 to 700,000 mPa.s, in particular from 20,000 to 350,000 mPa.s, in each case measured at 23 ° C.

Preferably, at least 40, in particular at least 50 wt .-% and preferably at most 90, in particular at most 80 wt .-% organopolysiloxane (A), based on the total Organopolysiloxanmasse (M) is used.

As crosslinkers (B) are preferably used silanes which have condensable groups with the hydroxyl groups of the α, ω-dihydroxypolydiorganosiloxane, and oligomeric condensation products of these silanes. Silanes and / or their condensation products of the general formula (III) are used in particular as crosslinkers (B). R ³ _m SiX _(4-m) (III), in the
R ³ are monovalent, optionally substituted by fluorine, chlorine or bromine atoms or C ₁ -C ₄ -alkoxyalkyl, amino-C ₁ -C ₆ alkyl, amino-C ₁ -C ₆ -alkylenamino- or cyano-substituted C ₁ - C ₁₀ hydrocarbon radicals,
X is hydrogen, fluorine, chlorine or bromine atoms, C ₁ -C ₄ -alkoxy, C ₁ -C ₄ -acyloxy, amino, C ₁ -C ₄ -alkylamino, C ₁ -C ₄ -dialkylamino-, -C ₁ -C ₆ -alkylamido-, - (NC ₁ -C ₄ -alkyl) -C ₁ -C ₆ -alkylamido or Si-ON = bonded C ₃ -C ₆ -ketoximo groups and
m is the value 0, 1 or 2.

Preferably, at least 0.5, in particular at least 2 wt .-% and preferably at most 15, in particular at most 10 wt .-% crosslinker (B), based on the total Organopolysiloxanmasse (M) is used.

Examples of fillers (C) are non-reinforcing fillers, ie fillers having a BET surface area of up to 50 m ² / g, such as carboxylic acid-coated chalks, quartz, diatomaceous earth, calcium silicate, zirconium silicate, zeolites, metal oxides such as aluminum, titanium, iron - or zinc oxides or their mixed oxides, barium sulfate, calcium carbonate, gigs, silicon nitride, silicon carbide, boron nitride, glass and plastic powder, such as polyacrylonitrile powder; reinforcing fillers, ie fillers with a SET surface area of more than 50 m ² / g, such as silica, for example fumed silica or precipitated silica, carbon black, such as furnace black and acetylene black, and silicon-aluminum mixed oxides with a large BET surface area; fibrous fillers such as asbestos as well as plastic fibers.

The stated fillers (C) may be rendered hydrophobic, for example by treatment with organosilanes or siloxanes or with stearic acid or by etherification of hydroxyl groups to alkoxy groups. It can be a kind of filler, it can also be a mixture of at least two fillers used.

The organopolysiloxane composition (M) preferably contains at least 2, in particular at least 5, and preferably at most 50, in particular at most 15,% by weight of filler (C).

Preferably, the organopolysiloxane composition (M) contains one or more catalysts (D). The catalysts (D) are preferably tin catalysts. The tin catalysts are preferably organic tin compounds, such as di-n-butyltin diacetate, di-n-butyltin dilaurate and reaction products of each molecule at least two bonded via oxygen to silicon, optionally substituted by an alkoxy group, monovalent hydrocarbon radicals as hydrolyzable groups silane or its oligomer with Diorganozinndiacylat, wherein in these reaction products all valences of the tin atoms are saturated by oxygen atoms of the group ≡SiOSn≡ or ≡COSn≡ or by SnC-bonded, monovalent organic radicals.

The organopolysiloxane composition (M) preferably contains at least 0.01, in particular at least 0.1, and preferably at most 3, in particular at most 1,% by weight of tin catalyst.

The organopolysiloxane composition (M) preferably comprises one or more adhesion promoters (E). Preferred adhesion promoters (E) are amino-functional organosilicon compounds.

Examples of amino-functional organosilicon compounds (E) are amino-functional silanes, amino-functional organosiloxanes. Examples of amino-functional radicals of the organosilicon compounds (E) are aminomethyl, 1-aminoethyl, 3-phenylpropyl, N- (2-aminoethyl) -3-aminopropyl, aminoethylaminoethylaminopropyl and cyclohexylaminopropyl radicals.

The addition of other ingredients, such as catalysts, pigments and fungicides, is possible.

The term polysiloxanes is intended in the context of the present invention to include diniere, oligomeric and polymeric siloxanes.

Examples

In the following examples, all parts and percentages are by weight unless otherwise specified. Unless otherwise indicated, the following examples are at a pressure of the surrounding atmosphere, ie at about 1000 hPa, and room temperature, ie at 20 ° C, or at a temperature resulting from the addition of the reactants at room temperature without additional heating and Cooling stops, carried out.

The statement that a paste is stable means that when tested in accordance with ISO (International Standard) 7390, it does not escape more than 2 mm from a U 20 rail (clear width: 20 mm, depth: 10 mm).

The mechanical values, d. H. Stress at elongation, tensile strength and elongation at break, are in accordance with ISO 8339 with aluminum contact material and the pre-storage A, d. H. a storage of the test specimens of 28 days at 23 ° C and 50% relative humidity, determined.

The Shore A hardness of the elastomers is also determined after four weeks of pre-storage of the test specimens at 23 ° C and 50% relative humidity to ISO 868.

• – 23°C und 50% relativer Luftfeuchtigkeit
• – 70°C im Wärmeschrank und
• – in der, wie in der ASTM C 1248 beschriebenen, UV-Prüfkammer gelagert.

The contamination of porous substrates is measured according to ASTM (American Society for Testing and Materials) C 1248. As a substrate Altaquarzit is used without primer. The specimens are after 21 days of vulcanization at 23 ° C and 50% relative humidity compressed by 25%, then a total of 28 days at

• - 23 ° C and 50% relative humidity
• - 70 ° C in a warming cabinet and
• - stored in the UV test chamber as described in ASTM C 1248.

This is followed by the determination of plasticizer emigration.

Example 1:

• a) Preparation of the Adhesion Improving Agent In a three-necked flask equipped with a reflux condenser, thermometer and stirrer, 200 parts of a dimethylpolysiloxane each having a Si-bonded hydroxyl group in the terminal units having a viscosity of 80 mPa · s at 23 ° C. and 83 parts N- (2-aminoethyl) -3- aminopropyltrimethoxysilane mixed with 1.7 parts of 5 percent methanolic potassium hydroxide solution. The resulting mixture is heated to 140 ° C with stirring for 3 hours. The contents of the flask are then cooled to 50 ° C. and mixed with a portion of 10% aqueous hydrochloric acid, the reflux condenser is replaced by a descending condenser-type condenser and the pressure in this apparatus is reduced to 100 hPa (abs.). Finally, from the three-necked flask, the fractions boiling up to 180 ° C. at 50 hPa (abs.) Are distilled off. The residue is a Si-bonded methoxy-containing organopolysiloxane of dimethylsiloxane and N- (2-aminoethyl) -3-aminopropylsiloxane units.
• b) Preparation of the Condensation Catalyst A mixture of 4 parts of tetra-n-propoxysilane and 1 part of di-n-butyltin diacetate is heated to 120 ° C. with stirring for 6 hours. At the same time, the resulting acetic acid n-propyl ester is continuously distilled off. Thereafter, according to the infrared spectrum, the valence vibration of the carbonyl group of di-n-butyltin diacetate, which is 1600 cm ^-1 , has disappeared.
• c) In a planetary mixer with vacuum equipment, 45 parts of one in the terminal units each having an Si-bonded hydroxyl group-containing dimethylpolysiloxane having a viscosity of 75000 mPa · s at 23 ° C with 25 parts of a trimethylsiloxy endblocked dimethylpolysiloxane with a viscosity of 10 mm ² / s at 23 ° C and 1.0 parts of polyethylene polypropylene glycol having a molecular weight of about 3400 and an ethylene oxide content of about 45%. In this mixture, first 5.0 parts of a mixture of 88% methyltris- (butanone-2) -oximosilan and 12% tetrakis (butanone-2) -oximosilan and then 1.0 part of the described under a) organopolysiloxane with over Carbon bonded to silicon-bound amino groups and homogenized in vacuo for 5 minutes. The mixture thus obtained is co-impregnated with 20 parts of calcium carbonate, the surface of which is coated with stearic acid ("coated chalk") and has a BET specific surface area of about 1 m ² / g, 6.5 parts pyrogenically vapor-deposited hydrophilic silica a BET surface area of 150 m ² / g and 0.1 part of the reaction product whose preparation is described under b), added.
• d) The procedure described under c) is repeated with the modification that instead of 25 parts of a trimethylsiloxy endblocked dimethylpolysiloxane with a viscosity of 10 mm ² / s at 23 ° C one with a viscosity of 100 mm ² / s at 23 ° C is used.
• e) The procedure described under c) is repeated with the modification that instead of 45 parts of a dimethylpolysiloxane having a viscosity of 75,000 mPa · s and having a viscosity of 75,000 mPa · s in the terminal units at 70 ° C., 70 parts are used the addition of 25 parts of an endblocked with trimethylsiloxy dimethylpolysiloxane having a viscosity of 10 mm ² / s at 23 ° C is omitted.

The obtained according to Examples 1 c) to 1 d), freed by evacuation of trapped air, excluding water-bearing, on access of water at room temperature to form elastomers crosslinking RTV molding compositions are homogeneous and stable. They are bottled in tubes. while the mixtures of Examples 1 c) and 1 d) are supple soft and easy to squeeze, the mixture of Example 1 e) is viscous and difficult to process.

The results of the plasticizer migration test according to ASTM C 1248 and the mechanical values according to ISO 8339 are given in Table 1. Table 1 example Plasticizer output hike Tear strength N / mm ² Elongation at break% Stress value at 100% elongation N / mm ² Shore A hardness 1c none 0.51 300 0.32 17 1d * strong (3-10 mm) 0.55 330 0.32 15 1e * none 0.60 110 0.59 30 * not according to the invention

Example 2:

• a) In a planetary mixer with vacuum equipment 60 parts of in the terminal units each having an Si-bonded hydroxyl group-containing dimethylpolysiloxane having a viscosity of 75000 mPa · s at 23 ° C with 24.4 parts of a trimethylsiloxy endblocked dimethylpolysiloxane having a viscosity of 10 mm 2 / s at 23 ° C and 0.8 parts of a mixture of alkoxylated phosphoric acid esters of the formulas (HO) PO [(OCH ₂ CH ₂ ) _3-4 -O- (CH ₂ ) _11-14 CH ₃ ] ₂ and (HO) ₂ PO [(OCH ₂ CH ₂ ) _3-4 -O- (CH ₂ ) _11-14 CH ₃ ] mixed.
• Immediately thereafter, a mixture of 2.0 parts of vinyltrimethoxysilane and 1.5 parts of methyltrimethoxysilane is added and homogenised in vacuo for 5 minutes.
• Thereafter, while maintaining the usual for RTV-1 masses mixing technique in the order given.
• 1.8 parts of amino-functional siloxane: equilibration product of 3-aminopropyltriethoxysilane and a condensate / hydrolyzate of methyltrimethoxysilane having an amine number of 2.2.
• - 0.2 parts of N- (2-aminoethyl) -3-aminopropyltrimethoxysilane
• 9.0 parts of pyrogenic, hydrophilic silica having a BET surface area of 150 m ² / g and
• 0.30 parts of the reaction product described in more detail in Example 1 under b).
• b) The procedure described under a) is repeated with the modification that instead of 24.4 parts of a trimethylsiloxy-endblocked dimethylpolysiloxane with a viscosity of 10 mm ² / s at 23 ° C one with a viscosity of 100 mm ² / s at 23 ° C is used.
• c) The procedure described under a) is repeated with the modification that instead of 60 parts of a dimethylpolysiloxane having a viscosity of 75,000 mPa · s and having a viscosity of 75,000 mPa · s in the terminal units, 84.4 parts are used at 23.degree and the addition of 24.4 parts of a trimethylsiloxy-endblocked dimethylpolysiloxane with a viscosity of 10 mm ² / s at 23 ° C is omitted.

The RTV molding compositions obtained in Examples 2 a) to 2 c), evacuated by evacuation of air inclusions, excluding water-stable RTV molding compositions which crosslink at room temperature to give elastomers at room temperature, are homogeneous and stable. They are bottled in tubes. While mixtures of Examples 2 a) and 2 b) are supple soft and easy to squeeze, the mixture of Example 2 c) is viscous and difficult to process.

The results of the plasticizer migration test according to ASTM C 1248 and the mechanical values according to ISO 8339 are given in Table 2. Table 2 example Plasticizer output hike Tear strength N / mm ² Elongation at break% Stress value at 100% elongation N / mm ² Shore A hardness 2 a none 0.58 290 0.32 18 2 B* strongly 0.55 310 0.33 17 (4mm) 2 c * none 0.67 200 0.67 28 * not according to the invention

Example 3:

• a) 100 parts of one in the terminal units each having a vinyl group-containing dimethylpolysiloxane having a viscosity of 20,000 mPa · s at 23 ° C are mixed in a Muldenneter with 19 parts of hexamethyldisilazane and 7 parts of water and stirred for 15 minutes at room temperature. 63 parts of fumed gas-phase-produced silica having a specific surface area of 300 m ² / g according to BET are added. The mixture thus obtained is kneaded first at room temperature for one hour and then at 100 ° C. for two hours. Then, by suction of gaseous content from the kneader in this kneader, the pressure to 80 hPa (abs.) Lowered, the remaining kneader contents heated to 140 ° C and kneaded at this temperature for 2 hours. After cooling to room temperature and venting, 100 parts of the mixture thus obtained are diluted with 30 parts of each in the terminal units each having a vinyl group-containing dimethylpolisiloxane having a viscosity of 20,000 mPa · s at 23 ° C.
• b) In a planetary mixer, 62.3 parts of the mixture whose preparation in this example has been described above under b), first with 23.3 parts of tetra-i-butoxy-silane, then with 8.7 parts of N- (2- Aminoethyl) -3-aminopropyl-tri-n-butoxysilane and 4.0 parts of N- (2-aminoethyl) -3-aminopropyltriethoxysilane and finally 1.7 parts of the reaction product, the preparation of which was described in Example 1 above under b), at Room temperature and mixed under the pressure of the surrounding atmosphere. By lowering the pressure in the kneader, gaseous constituents of the mass, which form bubbles in the mass, are finally removed.
• It is obtained a homogeneous, supple soft, stable and crystal clear paste. It is bottled in a tube.
• c) Application of the paste, the preparation of which in this example has been described under b) above, in two-component systems crosslinking at room temperature to organopolysiloxane elastomers.

• I. In a planetary mixer are 750 parts of one in the terminal units each having a Si-bonded hydroxyl group-containing dimethylpolysiloxane having a viscosity of 300,000 mPa · s at 23 ° C with 620 parts of an endblocked by trimethylsiloxy dimethylpolysiloxane with a viscosity of 10 mm ² / s mixed at 23 ° C. It adds 25 parts of polyethylene propylene glycol having a molecular weight of about 3400 and an ethylene oxide content of about 45 and degassed with stirring for a short time. This is followed by the addition of 870 parts of calcium carbonate, the surface of which is coated with stearic acid ("coated chalk") having a BET specific surface area of 20 m ² / g and 250 parts of calcium carbonate, the surface of which is also coated with stearic acid, but a specific one Surface has BET of about 1 m ² / g. The mixture thus obtained is then homogenized in vacuo.
• II. The procedure described under I. is repeated with the modification that instead of 620 parts of a trimethylsiloxy endblocked dimethylpolysiloxane with a viscosity of 10 mm ² / s at 23 ° C one with a viscosity of 100 mm ² / s at 23 ° C is used.
• III. The procedure described under I. is repeated with the modification that instead of 750 parts in the terminal units each having a Si-bonded hydroxyl group-containing dimethylpolysiloxane having a viscosity of 300,000 mPa · s at 23 ° C 1370 parts are used and the additive of 620 parts of a trimethylsiloxy endblocked dimethylpolysiloxane with a viscosity of 10 mm ² / s at 23 ° C is omitted.

The thus obtained, in this example under I. and II.
The basic materials described above are homogeneous, supple soft and stable. In contrast, in this example under III. Although the above-described basic mass is also homogeneous and stable, but kittig and can be poorly processed.

Per 100 parts of the in this example under I.-III.
are described with 10 parts of the paste whose preparation has been described in this example in b) above, and freed from gaseous components by applying a vacuum.

There are obtained three mixtures, which in the case of the use of the basic materials I. and II supple soft, in the case of use of the matrix III. kittig and poorly moldable, can be pressed and processed. The mixtures crosslink at room temperature to elastomers whose properties are summarized in Table 3. Table 3 example Plasticizer output hike Tear strength N / mm ² elongation at break Stress value at 100 elongation N / mm ² Shore A hardness 3 I none 0.85 490 0.26 10 3 II * strong (3-5 mm) 0.86 480 0.24 14 3 III * none 1.15 250 0.69 25 * not according to the invention

It can be seen from Tables 1 to 3 that the use of the dimethylpolysiloxanes according to the invention having terminal trimethylsiloxy groups whose viscosity is below 25 mm ² / s at 23 ° C. as plasticizers in organopolysiloxane compositions crosslinking at room temperature leads to compounds which are supple and soft easy to process. The Organopolysiloxanelastomere obtained from these compositions by crosslinking have a low stress value at stretch and do not bleed in contact with absorbent substrates such as natural stone, ie their use z. B. in joints between natural stones leads to no edge zone contamination.

Claims (8)

Condensable crosslinkable organopolysiloxane compositions (M) which act as plasticizers diorganopolysiloxane (W) of the general formula (I) R ₃ Si (O-SiR ¹ ₂ ) _n -OSiR ₃ (I), comprise monovalent R and R ¹ unsubstituted C ₁ -C ₈ hydrocarbon radicals substituted by fluorine, chlorine or bromine atoms or C ₁ -C ₄ -alkoxyalkyl or cyano groups, C ₁ -C ₈ hydrocarbon radicals, and n values of 6 to 15, wherein the viscosity of the organopolysiloxane (W) is 5 to 25 mm ² / s at 25 ° C. Organopolysiloxane compositions (M) according to Claim 1, in which the radicals R and R ^{1 are} unsubstituted hydrocarbon radicals having 1 to 6 carbon atoms. Organopolysiloxane compositions (M) according to claim 1 or 2 which are RTV-1 organopolysiloxane compositions (M) obtainable by mixing diorganopolysiloxane (W), α, ω-dihydroxypolydiorganosiloxane (A), crosslinker (B) and filler (C) , Organopolysiloxane compositions (M) according to Claim 3, in which 40 to 90% by weight of organopolysiloxane (A), based on the total organopolysiloxane composition (M), are used. Organopolysiloxane compositions (M) according to claim 3 or 4, in which the crosslinker (B) is selected from silanes of the general formula (III) R ³ _m SiX _(4-m) (III) in the R ³ monovalent unsubstituted C ₁ -C ₁₀ hydrocarbon radicals, with fluorine, chlorine or bromine atoms or C ₁ -C ₄ alkoxyalkyl, amino-C ₁ -C ₆ alkyl, amino-C ₁ -C ₆ -alkyleneamino or cyano groups substituted C ₁ -C ₁₀ -hydrocarbon radicals, X hydrogen, fluorine, chlorine or bromine atoms or C ₁ -C ₄ -alkoxy, C ₁ -C ₄ -acyloxy, amino, C ₁ - C ₄ alkylamino, C ₁ -C ₄ dialkylamino, C ₁ -C ₆ alkylamido, - (NC ₁ -C ₄ alkyl) -C ₁ -C ₆ alkylamido or Si-ON = bonded C ₃ -C ₆ ketoximo groups and m is 0, 1 or 2, and condensation products of these silanes. Organopolysiloxane compositions (M) according to Claims 3 to 5, in which 0.5 to 15% by weight of crosslinker (B), based on the total organopolysiloxane composition (M), are used. Organopolysiloxane compositions (M) according to Claims 3 to 6, in which the filler (C) is selected from carboxylic acid-coated chalks, quartz, diatomaceous earth, calcium silicate, zirconium silicate, zeolites, metal oxides, barium sulfate, calcium carbonate, gypsum and silica. Organopolysiloxane compositions (M) according to Claims 3 to 7, in which 2 to 40% by weight of filler (C), based on the total organopolysiloxane composition (M), are used.