One-package RTV compositions which are storage-stable under anhydrous conditions and form paintable elastomers.

The present invention relates to storage-stable, room-temperature-crosslinking, one-component silicone-based compositions which, after curing in moist air, form elastomers which can be painted over and have very good paint adhesion. Such elastomers can be used as joint sealants in the construction industry, such as for sealing sanitary, floor and wall joints or for sealing windows between glass and frame or frame and wall.

Silicone sealants that can be crosslinked in moist air generally consist of α, ω-dihydroxypolydiorganosiloxanes and silicone oils, which are optionally mixed with precipitated or pyrogenic silicas, quartz powder, diatomaceous earth, dolomite powder, chalk, zinc oxide and other fillers. If you add organosilicon compounds to such systems that have more than two reactive groups and that can react with both silanol groups and water - these reactions are usually accelerated by catalysts such as titanium acid esters and heavy metal salts - and the access of all of them is closed Moisture, this results in masses that are stable in storage, which only cross-link to silicone elastomers due to their water vapor content when atomic air enters.

Such RTV-1K systems can, as previously described, be used as joint sealants. The so-called neutral system based on carboxamidoalkylalkoxysilanes, as described, for example, in DE-PS 1 247 646 and DE-PS 1 258 087, has proven particularly useful. However, these sealants cannot be painted over, a property that is often required in the construction industry.

According to US Pat. No. 3,957,714 and US Pat. No. 4,293,616, paintable systems based on carboxylate silanes are described which are produced in the first case by means of acicular calcium carbonate and solvent addition, in the second case by coated, ground chalk and addition of polyethers. However, the resulting elastomers have greatly changed mechanical properties such as high modulus and high Shore A hardness, low elongation at break, volume shrinkage and limited repaintability. The latter also applies to the systems according to EP 43 501, in which the paintability can be trouble-free 1-3 days after the sealant has been applied, while a preliminary cleaning with solvents must first be carried out later.

According to the present invention, the disadvantages mentioned can be eliminated. The invention relates to polydiorganosiloxane compositions which can be stored under the exclusion of moisture and can be hardened at ambient temperature under the action of water or atmospheric air to give low-modulus elastomers of high elongation and tear resistance, obtainable by mixing α, ω-dihydroxypolydiorganosiloxanes, α, ω-bis (triorganylsiloxy) polyorganosiloxanes with carboxylic acid amidoalkylalkoxy silicon compounds serving as crosslinking agents and complex titanium acid esters as well as fillers and optionally pigments and the crosslinking accelerating heavy metal salts, which are characterized in that hydrophobic chalk precipitated as filler is used, whose residual moisture was brought to a content of less than 0.15% by weight before the addition of titanium acid esters and crosslinking agents.

Surprisingly, it has been found that the sealants produced in this way can be coated with commercially available paints even after several weeks. If the sealant is free of external dirt after this time, the painting can be carried out without pre-treatment such as pre-cleaning. Precoats and topcoats based on alkyd resins, polyurethanes, polyacrylates, polystyrenes, polyvinyl acetates and polyvinyl propionates can be used as lacquers both as a solvent and as an aqueous dispersion system. After the paint has hardened, very good paint adhesion results. A very interesting variant, especially for damp rooms in the sanitary area (bath, shower, sauna area etc.) is the possibility of using paints with fungicidal active ingredient additives. Because the sealants according to the invention remain paintable even after they have completely hardened and thereafter, the paint may have to be renewed at the intervals required for the declining fungicidal activity.

The problem of fungal attack on sealing joints in damp rooms with a service life of approx. 2 years or more has now been remedied by refreshing the paint. The inevitable consequence is a longer service life for the sealing joints.

For the preparation of the RTV-1K compositions according to the invention, α, ω-dihydroxypolydiorganosiloxanes which essentially contain methyl groups and whose viscosity at 20 ° C. are between 1000 and 1,000,000 mPas, particularly preferably between 10,000 and 300,000 Pas, are preferably used as polymers lies. The concentration of the polymer should be between 25 and 60% by weight. The use of plasticizing oils is customary for the production of sealants, but is not absolutely necessary for the systems according to the invention. Trimethylsilox-terminated polydimethylsiloxane oil with a viscosity between 30 and 10,000 mPas, measured at 20 ° C., is preferably used as the plasticizing oil. In addition, silicone oils which consist of T, D and M units and polymers of the type are also suitable<chemistry id="chem0001" num="0001"><img file="EP0367012A2_D0001.tif" /></chemistry>

Precipitated and thus particularly fine chalks with an average particle diameter of less than 0.5 µm, preferably less than 0.1 µm, which have been coated with carboxylic acids or silanes and thus rendered hydrophobic, have proven to be optimal reinforcement fillers. Stearic acid, the concentration of which should be above 2.0% by weight, is particularly preferred, provided that the distribution is uniform. A chalk with the highest possible degree of whiteness and a low color cast should also be used for the production of white colored sealants.

In order to obtain stable masses, between 30 and 55% by weight of chalk is required, particularly fine-particle chalks resulting in stability from 30% by weight, whereas chalks with an average particle size of more than 0.1 µm in amounts of up to 55% by weight. -% must be added. The stability is determined according to DIN 65 262 part 3 at 23 ° C and 50% relative humidity on a fresh paste application on a vertical surface. After 30 minutes, a 1 cm thick paste should not have run down more than 1.5 mm.

If you use a chalk with the characteristics described, you do not need any additives such as silica to adjust the stability. This is because additives of this type only cause the elastomer formed after crosslinking to tighten and counteract paintability and paint adhesion.

The commercially available chalks contain up to 1% by weight of water, especially fine types even more. An essential part of the present invention is a low moisture content of the chalk; it should be less than 0.25% by weight, but preferably less than 0.15% by weight, the moisture content being as low as possible, especially in the case of chalk additives at the upper limit, in order to obtain a storage-stable paste.

To remove the water in the filler, there is first the possibility of separate drying. In the case of chalks coated with stearic acid, it should be carried out below 120 ° C if possible. Optimal drying units are eg vacuum belt dryers, vacuum drum dryers and microwave dryers. When introducing the dried chalk into the polymer, care must be taken to strictly exclude atmospheric moisture, which must also be observed for the further processing of the mixture. Another possible procedure is the drying of the chalk and polymer system including plasticizer oil. Technically, units with extremely good mixing and thus favorable heat transfer, such as mixing screws with vacuum segments, are well suited for this.

The pastes produced in this way allow the concentrations of titanium acid ester and the carboxylic acid amidoalkylalkoxy silicon compounds to be reduced compared to the conservatively produced pastes in the planetary mixer without a drying step. The measure not only leads to less expensive systems, but surprisingly to better mechanical properties of the sealants. Lowering the concentrations of the compounds mentioned below 4% by weight, preferably below 3% by weight brings about a reduction in the modulus of elasticity and Shore A hardness and an increase in the elongation at break, that is to say changes which are desired.

Titanium tetraalkyl esters, dialkyl titanium dialkyl esters and other titanium organoesters with chelating groups, such as those listed in patent application DE-PS 1 258 087, can be used as the titanium acid esters. Di-i-butoxytitanium diacetoacetic acid ethyl ester chelate and di-i-propoxytitanium bis-acetylacetonate are particularly preferred. Carboxylic acid amidoalkylalkoxy silicon compounds are used as crosslinkers, such as: Di-N-methylbenzamido-methyl-ethoxysilane Di-N-methylbenzamido-methyl-methoxy-silane Di-N-methylpropylamido-methyl-ethoxysilane Mono-N-methylpropylamido-methyl-diethoxysilane Di-N-methylpropylamido-methyl-methoxysilane Di-N-methylcaprolactam-methyl-ethoxysilane Di-N-methylcaprolactam-methyl-methoxy-silane.

Di-N-methylbenzamido-methyl-ethoxysilane is particularly preferably used as the crosslinking agent.

The following examples are intended to illustrate the present invention:

example 1

In a mixture of 32.0 parts by weight of α, ω-dihydroxypolydimethylsiloxane with a viscosity of 50,000 mPas and 13.3 parts by weight of α, ω-bis (trimethylsiloxy) polydimethylsiloxane with a viscosity of 100 mPas, 48.0 parts by weight of a precipitated chalk treated with stearic acid are added an average particle diameter of 0.08 µm mixed in with exclusion of moisture for 15 minutes. The mixture is stirred in vacuo at 2 mbar and 100 ° C. for 30 minutes and then cooled to a temperature below 40 ° C. Then 3.0 parts by weight of di-i-butoxytitanium diacetoacetic acid ethyl chelate are added and the mixture is stirred for 20 minutes under vacuum, then 0.7 part by weight of dibutyltin dilaurate with a stirring time of 5 minutes and finally 3.0 parts by weight of di-N-methylbenzamido-methyl-ethoxysilane and stirred in for approx Evacuated 20 minutes.

The mass is filled into cartridges and stored away from moisture. The shelf life is at least 1/2 year without the properties of the paste or sealant being impaired in a later application.

The paste vulcanizes under the influence of air humidity to a silicone rubber with the following mechanical properties: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Shore A hardness</entry><entry namest="col2" nameend="col2" align="char" char=",">26</entry></row><row><entry namest="col1" nameend="col1" align="left">E-module 100%</entry><entry namest="col2" nameend="col2" align="char" char=",">0.60 N / mm²</entry></row><row><entry namest="col1" nameend="col1" align="left">Tensile strength</entry><entry namest="col2" nameend="col2" align="char" char=",">1.35 N / mm²</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Elongation at break</entry><entry namest="col2" nameend="col2" align="char" char=",">400 %</entry></row></tbody></tgroup></table></tables>

Example 2

32.0 parts by weight of α, ω-dihydroxypolydimethylsiloxane with a viscosity of 50,000 mPas and 13.5 parts by weight of α, ω-bis (trimethylsiloxy) polydimethylsiloxane with a viscosity of 100 mPas are mixed with 49.0 parts by weight of a precipitated chalk as in Example 1 and dried . 2.2 parts by weight of di-i-butoxytitanediacetoacetic acid ethyl ester chelate (20 minutes), 0.7 part by weight of dibutyltin dilaurate (5 minutes) and 2.6 parts by weight of di-N-methylbenzamidomethylethoxysilane (20 minutes) are successively stirred into the cooled mixture and evacuated for about 20 minutes . The paste filled in cartridges can be stored in the absence of air humidity for at least 1/2 year without losing its quality.

Mechanical properties of silicone rubber manufactured under air humidity: <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Shore A hardness</entry><entry namest="col2" nameend="col2" align="char" char=",">25</entry></row><row><entry namest="col1" nameend="col1" align="left">E-module 100%</entry><entry namest="col2" nameend="col2" align="char" char=",">0.56 N / mm²</entry></row><row><entry namest="col1" nameend="col1" align="left">Tensile strength</entry><entry namest="col2" nameend="col2" align="char" char=",">1.80 N / mm²</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Elongation at break</entry><entry namest="col2" nameend="col2" align="char" char=",">810 %</entry></row></tbody></tgroup></table></tables>

Example 3

An α, ω-dihydroxypolydimethylsiloxane with a viscosity of 80,000 mPas is used as the polymer, otherwise a sealant is produced identically to Example 2. The system also proved to be stable in storage for 1/2 year.

Mechanical properties of the sealant produced in moist air: <tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Shore A hardness</entry><entry namest="col2" nameend="col2" align="char" char=",">27</entry></row><row><entry namest="col1" nameend="col1" align="left">E-module 100%</entry><entry namest="col2" nameend="col2" align="char" char=",">0.65 N / mm²</entry></row><row><entry namest="col1" nameend="col1" align="left">Tensile strength</entry><entry namest="col2" nameend="col2" align="char" char=",">1.81 N / mm²</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Elongation at break</entry><entry namest="col2" nameend="col2" align="char" char=",">660 %</entry></row></tbody></tgroup></table></tables>

Example 4

40.5 parts by weight of α, ω-dihydroxypolydimethylsiloxane with a viscosity of 50,000 mPas and 14.0 parts by weight of α, ω-bis (trimethylsiloxy) polydimethylsiloxane with a viscosity of 100 mPas are mixed with 40.0 parts by weight of a precipitated chalk as in Example 1 and in Vacuum free of adhering water at 100 ° C for 30 minutes. 2.2 parts by weight of di-i-butoxytitanediacetoacetic acid ethyl ester chelate (20 minutes), 0.7 part by weight of dibutyltin dilaurate (5 minutes) and 2.6 parts by weight of di-N-methylbenzamido-methylethoxysilane (20 minutes) are successively stirred into the cooled mixture and evacuated in each case. The paste thus produced is stable in storage for at least half a year in the absence of atmospheric moisture.

Mechanical properties of the sealant produced in moist air: <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Shore A hardness</entry><entry namest="col2" nameend="col2" align="char" char=",">22</entry></row><row><entry namest="col1" nameend="col1" align="left">E-module 100%</entry><entry namest="col2" nameend="col2" align="char" char=",">0.43 N / mm²</entry></row><row><entry namest="col1" nameend="col1" align="left">Tensile strength</entry><entry namest="col2" nameend="col2" align="char" char=",">1.80 N / mm²</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Elongation at break</entry><entry namest="col2" nameend="col2" align="char" char=",">971 %</entry></row></tbody></tgroup></table></tables>

Example 5

A sealant is produced according to the recipe of Example 4, with the difference that the chalk was dried separately before being added to the other raw materials (vacuum drying at 60 ° C. in a layer height of approx. 2 cm to constant weight). After adding the chalk with the exclusion of atmospheric moisture, the mixture is stirred until homogeneous (approx. 30 minutes) and the procedure is continued as in Example 4.

A sealant which is stable in storage for a period of 1/2 year with the exclusion of atmospheric humidity is also obtained, which has the following mechanical properties after vulcanization by atmospheric humidity: <tables id="tabl0005" num="0005"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Shore A hardness</entry><entry namest="col2" nameend="col2" align="char" char=",">21</entry></row><row><entry namest="col1" nameend="col1" align="left">E-module 100%</entry><entry namest="col2" nameend="col2" align="char" char=",">0.41 N / mm²</entry></row><row><entry namest="col1" nameend="col1" align="left">Tensile strength</entry><entry namest="col2" nameend="col2" align="char" char=",">1.89 N / mm²</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Elongation at break</entry><entry namest="col2" nameend="col2" align="char" char=",">990 %</entry></row></tbody></tgroup></table></tables>

The mechanical values ​​of Examples 1-5 relate to the DIN standard 53 505 (Shore A hardness) and DIN 53 504 (standard rod). All sealants produced were tested for their ability to be painted over.

After the start of vulcanization under standard climate conditions (23 ° C, 50% relative air humidity), varnishes were applied at intervals of 24, 48 and 7 days without pretreating the sealant surface in any way. The paint adhesion was carried out according to the Boeing test in accordance with ASTM D 3359-70.<tables id="tabl0006" num="0006"><table frame="all"><title>Table 1:</title><tgroup cols="5" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="31.50mm" /><colspec colnum="2" colname="col2" colwidth="31.50mm" /><colspec colnum="3" colname="col3" colwidth="31.50mm" /><colspec colnum="4" colname="col4" colwidth="31.50mm" /><colspec colnum="5" colname="col5" colwidth="31.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col5" align="center">Paint adhesion (Boeing test according to ASTMD 3359-70)</entry></row><row><entry namest="col1" nameend="col5" align="center">Application of the lacquer to the sealants of Examples 1-5</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">24th H</entry><entry namest="col3" nameend="col3" align="center">48 H</entry><entry namest="col4" nameend="col4" align="center">7 Days</entry><entry namest="col5" nameend="col5" align="center">4th Weeks after the start of vulcanization</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">White alkyd resin topcoat</entry><entry namest="col2" nameend="col2" align="right">100 %</entry><entry namest="col3" nameend="col3" align="right">100 %</entry><entry namest="col4" nameend="col4" align="right">100 %</entry><entry namest="col5" nameend="col5" align="right">100 %</entry></row><row><entry namest="col1" nameend="col1" /></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">White topcoat based on alkyd resin with 1% fungicide Preventol A 4 S®¹⁾</entry><entry namest="col2" nameend="col2" align="right">100 %</entry><entry namest="col3" nameend="col3" align="right">100 %</entry><entry namest="col4" nameend="col4" align="right">100 %</entry><entry namest="col5" nameend="col5" align="right">100 %</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Brown acrylic-based topcoat, aqueous emulsion</entry><entry namest="col2" nameend="col2" align="right">100 %</entry><entry namest="col3" nameend="col3" align="right">100 %</entry><entry namest="col4" nameend="col4" align="right">100 %</entry><entry namest="col5" nameend="col5" align="right">100 %</entry></row></tbody></tgroup><tgroup cols="5" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="31.50mm" /><colspec colnum="2" colname="col2" colwidth="31.50mm" /><colspec colnum="3" colname="col3" colwidth="31.50mm" /><colspec colnum="4" colname="col4" colwidth="31.50mm" /><colspec colnum="5" colname="col5" colwidth="31.50mm" /><tbody valign="top"><row><entry namest="col1" nameend="col5" align="justify">¹⁾ Commercial product from BAYER AG, Leverkusen</entry></row></tbody></tgroup></table></tables>