Compositions obtainable by the addition of tertiary amine to acryloxypropylalkoxysilanes, process for their preparation and their use

Acryloxypropylalkoxysilanes are important raw materials for the production of silicon-containing lacquers and paints (<i>EP-PS 0 324 747 and EP-PS 0 267 698</i>), including 3-methacryloxypropyl-trimethoxysilane. The pH value of these silanes often plays a decisive role in the manufacture and preparation of paints and inks as well as for the shelf life of the paints and inks. There is a need among experts for acryloxypropylalkoxysilanes with a pH of approx. 5 to 6.

However, the acryloxypropylalkoxysilanes which can be prepared by different production processes (US Pat. No. 3,258,477, US Pat. No. 4,946,977, US Pat. No. 5,117,027) have intrinsic pH values ​​of only about 3 to &lt;5.

Organosilanes are not protonic or Lewis acids in the conventional sense, but acidification is brought about in contact with water in the aqueous phase. The degree of acidification can be determined by pH measurement according to known methods. By definition, the pH value measured in water is assigned to organosilane.

Although it is possible to increase the pH of acryloxypropylalkoxysilanes by adding alkalizing compounds such as alkali or alkaline earth hydroxides or alkali or alkaline earth alcoholates, such mixtures are not stable in storage and the acrylic ester bond is rapidly cleaved after a short time <i>(G. Possmy and G. Körner, Macromolecular Chem. <u>73</u> (1964), pp. 85-108).</i> The cleavage is particularly easy in the presence of proton-providing solvents, such as. B. alcohols or water.

The object of the invention is to provide acryloxypropylalkoxysilanes which have a higher pH than the intrinsic pH and are stable in storage.

Surprisingly, it has now been found that acryloxypropylalkoxysilanes which contain tertiary amines have a higher pH than the intrinsic pH and are outstandingly stable in storage. There is no rapid cleavage of the acrylic ester bond even in the presence of proton-providing solvents. In addition, the color specification required by the paint and paint industry is excellently met by the acryloxypropylalkoxysilanes according to the invention.

The present invention therefore relates to a process for the preparation of a storage-stable composition comprising one or more acryloxypropylalkoxysilanes of the following general formula<chemistry id="chem0001" num="0001"><img file="EP0702016B1_D0001.tif" /></chemistry> where R¹ and R² are identical or different alkyl groups with 1 to 4 carbon atoms, m is 0 or 1 or 2 and R is a hydrogen or a methyl group, which is characterized in that that one or more tertiary amines are added to the acryloxypropylalkoxysitans. In the present patent application, compositions according to the invention were also referred to as acryloxypropylalkoxysilanes according to the invention.

Preferred here are tertiary amines which have a pK_B- Have a value between 3 and 5. The definition of pK_B-Values ​​can include the <i>"Textbook of Organic Chemistry</i>" <i>(1954)</i>, <i>Page 233, LF Fieser and M. Fieser,</i> be removed. Furthermore, the acryloxypropylalkoxysilanes according to the invention preferably have a pH&gt; 3 to &lt;7, particularly preferably a pH of ≥ 5 to &lt;7 and very particularly preferably a pH of ≥ 5 to ≤ 6. The acryloxypropylalkoxysilanes according to the invention can suitably contain tertiary amines in amounts of 10 to 500 ppm by weight. Of particular note among the acryloxypropylalkoxysilanes according to the invention is 3-methacryloxypropyltrimethoxysilane.

The present invention furthermore relates to a composition which can be obtained by the process according to the invention.

The pH of the acryloxypropylalkoxysilanes is preferably adjusted to&gt; 3 to &lt;7, particularly preferably to ≥ 5 to &lt;7 and very particularly preferably to ≥ 5 to ≤ 6, by adding at least one tertiary amine. The pH is suitably adjusted in such a way that, starting from the intrinsic pH of the respective acryloxypropylalkoxysilane, at least one tertiary amine is added with stirring. Suitably, at least one tertiary amine can be added to the acryloxypropylalkoxysilanes in an amount of 10 to 500 ppm by weight.

Preferably, the acryloxypropylalkoxysilanes are at least one tertiary amine with a pK_B-Value between 3 and 5, but more than one tertiary amine can also be added.

Unlike primary or secondary amines, the tertiary amines do not react in an anhydrous mixture with the double bonds of acryloxypropylalkoxysilanes. You can use both tertiary mono-, di- or triamines.

Tertiary monoamines which can be used according to the invention are, for. B .:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="3" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Triethylamine</entry><entry namest="col2" nameend="col2" align="left">Tri-2-ethylhexylamine</entry><entry namest="col3" nameend="col3" align="left">N-methylditridecylamine</entry></row><row><entry namest="col1" nameend="col1" align="left">Tripropylamine</entry><entry namest="col2" nameend="col2" align="left">NN-dimethylethylamine</entry><entry namest="col3" nameend="col3" align="left">Dimethylcyclohexylamine</entry></row><row><entry namest="col1" nameend="col1" align="left">Tributylamine</entry><entry namest="col2" nameend="col2" align="left">NN-dimethylisopropylamine</entry><entry namest="col3" nameend="col3" /></row><row><entry namest="col1" nameend="col1" align="left">Trioctylamine</entry><entry namest="col2" nameend="col2" align="left">NN-dimethylisobutylamine</entry><entry namest="col3" nameend="col3" /></row><row><entry namest="col1" nameend="col1" align="left">Diethyloctylamine</entry><entry namest="col2" nameend="col2" align="left">NN-dimethyl-2-ethylhexylamine</entry><entry namest="col3" nameend="col3" /></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Trusobutylamine</entry><entry namest="col2" nameend="col2" /><entry namest="col3" nameend="col3" /></row></tbody></tgroup></table></tables>

Tertiary diamines which can be used according to the invention are e.g. B .:<ul id="ul0001" list-style="none" compact="compact"><li>Bis-dimethylaminomethane</li><li>NNN'.N'-tetramethylethylenediamine</li><li>NNN'.N'-tetramethyl-1,3-diaminopropane</li></ul>

A tertiary triamine which can be used according to the invention is e.g. B .:<ul id="ul0002" list-style="none" compact="compact"><li>NNN'.N ".N." - Pentamethyldiethylenetriamine</li></ul>

The amines mentioned can be used alone or in mixtures. The acryloxypropylalkoxysilanes according to the invention can also be present as a mixture.

The present invention furthermore relates to the use of a composition according to the invention for the production of lacquers and paints containing silicon.

The present invention also relates to silicon-containing lacquers and paints which contain a composition according to the invention and polymers and / or copolymers of the acryloxypropylalkoxysilanes contained therein.

Table 1 shows the pH for 3-methacryloxypropyltrimethoxysilane and the pH after adding different amounts of tributylamine; the excellent mode of operation of the invention can be illustrated here by way of example. Another advantage of the present invention is that in the pH range, here specifically between 4.4 and 6.2, there is practically a linear relationship between the change in pH and the amount of tertiary amines added to the acryloxypropylalkoxysilane. It is thus possible to estimate the required amount of tertiary amines in advance in a simple manner for a desired pH adjustment.

The invention is illustrated by the following examples:

<u>example 1</u>

<ul id="ul0003" list-style="none"><li>a) Determination of the pH in commercially available 3-methacryloxypropyltrimethoxysilane: 2 parts by weight of DYNASYLAN MEMO-E (commercial product from Huls AG) were added to 3 parts by weight of double-distilled water with stirring using a magnetic stirrer and mixed thoroughly for 10 minutes at room temperature. After switching off the agitation and standing for 30 minutes, the pH was measured in the upper, aqueous phase by means of a combination electrode (type: N 1042 A with integrated temperature sensor Pt 100 from Schott) and pH measuring device (type: microprocessor pH meter CG 832 from Schott). A pH value of 4.4 was determined.</li><li>b) Determination of the pH value as a function of the amine concentration: Defined amounts of tributylamine ("purum" from Fluka, purity&gt; 98% (GC)) were weighed into commercially available 3-methacryloxypropyltrimethoxysilane (DYNASYLAN MEMO-E) and the pH was determined in the manner mentioned under a) (see FIG . Table 1). The 3-methacryloxypropyltrimethoxysilane according to the invention has a storage stability of more than 6 months for all set pH values.</li></ul>

<u>Example 2</u>

The procedure was as in Example 1, but instead of 3-methacryloxypropyltrimethoxysilane, the compound 3-acryloxypropyl-triethoxysilane with its own pH 4.8 and the compound diethyloctylamine being used instead of tributylamine. After adding 179 ppm by weight of diethyloctylamine, a pH of 5.8 was determined. The 3-acryloxypropyl-triethoxysilane according to the invention also has a storage stability of more than 6 months for all pH values ​​set.

<u>Example 3</u>

The procedure was as in Example 1, except that the compound 3-methacryloxypropylmethyldimethoxysilane with the intrinsic pH of 4.5 was used instead of 3-methacryloxypropyltrimethoxysilane. After adding 249 ppm by weight of tributylamine, a pH of 6.0 was measured. Here too, the storage stability for the 3-methacryloxypropyl-methyldimethoxysilane according to the invention is more than 6 months. <tables id="tabl0002" num="0002"><table frame="all"><title>Table 1:</title><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row rowsep="1"><entry namest="col1" nameend="col2" align="left">pH values ​​of 3-methacryloxypropyl-trimethoxysilane before and after adding different amounts of tributylamine</entry></row><row rowsep="1"><entry namest="col1" nameend="col2" align="center"><b>3-methacryloxypropyl trimethoxysilane</b></entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">Tributylamine content [ppm by weight]</entry><entry namest="col2" nameend="col2" align="center">PH value</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">0</entry><entry namest="col2" nameend="col2" align="char" char=",">4,4</entry></row><row><entry namest="col1" nameend="col1" align="center">25</entry><entry namest="col2" nameend="col2" align="char" char=",">4,6</entry></row><row><entry namest="col1" nameend="col1" align="center">50</entry><entry namest="col2" nameend="col2" align="char" char=",">4,7</entry></row><row><entry namest="col1" nameend="col1" align="center">75</entry><entry namest="col2" nameend="col2" align="char" char=",">4,8</entry></row><row><entry namest="col1" nameend="col1" align="center">100</entry><entry namest="col2" nameend="col2" align="char" char=",">5,0</entry></row><row><entry namest="col1" nameend="col1" align="center">150</entry><entry namest="col2" nameend="col2" align="char" char=",">5,3</entry></row><row><entry namest="col1" nameend="col1" align="center">200</entry><entry namest="col2" nameend="col2" align="char" char=",">5,6</entry></row><row><entry namest="col1" nameend="col1" align="center">300</entry><entry namest="col2" nameend="col2" align="char" char=",">6,2</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">400</entry><entry namest="col2" nameend="col2" align="char" char=",">6,5</entry></row></tbody></tgroup></table></tables>