Silicone (meth)acrylates, process for their preparation and their use in curable compositions

Abstract

A process can be used for preparing silicone (meth)acrylates, according to which at least one acetoxysilicone is reacted with at least one hydroxyfunctional (meth)acrylic acid ester. The corresponding silicone (meth)acrylates are useful, and can be used in curable compositions.

Claims

1. Method for preparing silicone (meth)acrylates, characterized in that at least one acetoxy silicone is reacted with at least one hydroxy-functional (meth)acrylic ester.

2. Method according to claim 1, characterized in that the at least one acetoxy silicone is a compound of formula (I),
M.sub.m1 M.sup.AcO.sub.m2 D.sub.d1 D.sup.AcO.sub.d2 T.sub.t Q.sub.q   formula (I), where M=[R.sub.3SiO.sub.1/2]; M.sup.AcO=[R.sub.2(AcO)SiO.sub.1/2]; D=[R.sub.2SiO.sub.2/2]; D.sup.AcO=[R(AcO)SiO.sub.2/2]; T=[RSiO.sub.3/2]; Q=[SiO.sub.4/2]; m1=0 to 32, preferably 0 to 22, especially 0; m2=0 to 32, preferably 1 to 10, especially 2; d1=1 to 1000, preferably 5 to 500, especially 10 to 400; d2=0 to 10, preferably 0 to 5, especially 0; t=0 to 10, preferably 0 to 5, especially 1 to 5; q=0 to 10, preferably 0 to 5, especially 1 to 5; in which R is in each case independently selected from the group consisting of monovalent organic radicals, is preferably in each case independently selected from the group consisting of monovalent hydrocarbon radicals having 1 to 30 carbon atoms, is particularly methyl; AcO is an acetoxy group; with the proviso that: m1+m2=at least 2, preferably 2 to 20, especially 3 to 10; m2+d2=at least 1, preferably 2 to 10, especially 2 to 6.

3. Method according to at least one of claims 1 to 2, characterized in that the at least one acetoxy silicone is produced by reacting p1 a) silanes and/or siloxanes bearing alkoxy groups, and/or b) silanes and/or siloxanes bearing acetoxy groups, and/or c) silanes and/or siloxanes bearing hydroxyl groups, and/or d) simple siloxane cycles and/or DT cycles, with acetic anyhdride, and also preferably acetic acid, and as catalyst at least one Br∅nsted acid having a pKa of ≤−1.3, preferably a superacid having a pKa of less than −3.0, more preferably perfluoroalkanesulfonic acid, particularly preferably trifluoromethanesulfonic acid.

4. Method according to at least one of claims 1 to 3, characterized in that the at least one Br∅nsted acid, preferably superacid, more preferably perfluoroalkanesulfonic acid, particularly preferably trifluoromethanesulfonic acid acidified acetoxy silicone is neutralized with a base prior to the further reaction with the at least one hydroxy-functional (meth)acrylic acid.

5. Method according to at least one of claims 1 to 4, characterized in that the at least one hydroxy-functional (meth)acrylic ester is a compound of the formula (II), ##STR00003## where x=at least 1, preferably 1 to 3, especially 1; in which R.sup.1 is in each case independently selected from the group consisting of (x+1)-valent organic radicals, is preferably in each case independently selected from the group consisting of hydrocarbon radicals having 1 to 40 carbon atoms, which may be interrupted by oxygen and/or nitrogen atoms and/or NH groups, is especially in each case independently selected from the group consisting of divalent alkylene and polyoxyalkylene radicals, R.sup.2 is in each case independently a hydrogen radical or a methyl radical.

6. Method for preparing silicone (meth)acrylates according to at least one of claims 1 to 5, characterized in that the molar ratio of the hydroxyl groups of the at least one hydroxy-functional (meth)acrylic ester to the acetoxy groups of the at least one acetoxy silicone is at least 1.00, preferably 1.03 to 1.15, especially 1.05 to 1.10.

7. Method according to at least one of claims 1 to 6, characterized in that the at least one acetoxy silicone is reacted with the at least one hydroxy-functional (meth)acrylic ester in the presence of a catalyst selected from the group consisting of a) Br∅nsted acids having a pKa of <−3, preferably sulfonic acids or halocarboxylic acids, particularly selected from the group consisting of trifluoromethanesulfonic acid, methanesulfonic acid, para-toluenesulfonic acid and trifluoroacetic acid; and/or b) Lewis acids; and/or c) metal catalysts, preferably selected from the group consisting of alkyl titanates, metal carboxylates and metal acetylacetonate complexes, particularly selected from the group consisting of titanium tetrabutoxide, zinc acetylacetonate and zinc carboxylate.

8. Method according to at least one of claims 1 to 7, characterized in that the reaction of the at least one acetoxy silicone with the at least one hydroxy-functional (meth)acrylic ester is carried out at a temperature of 40° C. to 150° C., particularly preferably 70° C. to 120° C., over a period of one to 8 hours, preferably over a period of 3 to 6 hours.

9. Method according to at least one of claims 1 to 8, characterized in that the reaction product is freed of volatile constituents for 1 to 8 hours, preferably 1 to 4 hours, at a temperature of 80° C. to 140° C., preferably 100° C. to 130° C., under application of a vacuum of less than 200 mbar, preferably less than 20 mbar, especially of less than 4 mbar.

10. Method according to at least one of claims 1 to 9, characterized in that acids possibly present in the reaction product are neutralized at a temperature of 20° C. to 110° C., preferably 40° C. to 80° C., by adding a solid, liquid or gaseous base, wherein preference is given to the use of a solid base, particularly in the form of carbonates and/or hydrogencarbonates of alkali metal and/or alkaline earth metal elements and/or of ammonium or the use of liquid bases, in this case preferably aliphatic and/or aromatic and/or alkylaromatic amines, or the use of ammonia as gaseous base.

11. Product or silicone (meth)acrylate preparable by a method according to at least one of claims 1 to 10.

12. Product or silicone (meth)acrylate according to claim 11, characterized in that the proportion by mass of heavy metals, boron and/or chlorine, based on the total mass of the product or silicone (meth)acrylate, is in each case ≤0.5%, especially ≤0.1%.

13. Product or silicone (meth)acrylate according to at least one of claims 11 to 12, characterized in that the sum total of proportions by mass of D.sub.4, D.sub.5 and D.sub.6, based on the mass of the product or silicone (meth)acrylate, is ≤0.1%, especially ≤0.05%.

14. Silicone (meth)acrylate, preferably according to claim 11, of the formula (III),
M.sub.m1 M.sup.Acr.sub.m2 D.sub.d1 D.sup.Acr.sub.d2 T.sub.t Q.sub.q   formula (III), where M=[R.sub.3SiO.sub.1/2]; M.sup.Acr=[RR.sup.AcrSiO.sub.1/2], D=[R.sub.2SiO.sub.2/2]; D.sup.Acr=[RR.sup.AcrSiO.sub.2/2]; T=[RSiO.sub.3/2]; Q=[SiO.sub.4/2]; m1=0 to 32, preferably 0 to 22, especially 0; m2=0 to 32, preferably 1 to 10, especially 2; d1=1 to 1000, preferably 5 to 500, especially 10 to 400; d2=0 to 10, preferably 0 to 5, especially 0; t=0 to 10, preferably 0 to 5, especially 1 to 5; q=0 to 10, preferably 0 to 5, especially 1 to 5; with the proviso that: m1+m2=at least 2, preferably 2 to 20, especially 3 to 10; m2+d2=at least 1, preferably 2 to 10, especially 2 to 6; in which R is in each case independently selected from the group consisting of monovalent organic radicals, is preferably in each case independently selected from the group consisting of monovalent hydrocarbon radicals having 1 to 30 carbon atoms, is particularly methyl; R.sup.Acr is in each case independently selected from monovalent radicals of the formula (IV), ##STR00004## where x=at least 1, preferably 1 to 3, especially 1; in which R.sup.1 is in each case independently selected from the group consisting of (x+1)-valent organic radicals, is preferably in each case independently selected from the group consisting of hydrocarbon radicals having 1 to 40 carbon atoms, which may be interrupted by oxygen and/or nitrogen atoms and/or NH groups, is especially in each case independently selected from the group consisting of divalent alkylene and polyoxyalkylene radicals; R.sup.2 is in each case independently a hydrogen radical or a methyl radical.

15. Product according to at least one of claims 11 to 13, comprising at least one silicone (meth)acrylate according to claim 14.

16. Composition comprising at least one product or at least one silicone (meth)acrylate according to at least one of claims 11 to 15.

17. Composition according to claim 16, characterized in that said composition is curable, preferably curable by means of a radical reaction, wherein the radical reaction can be initiated thermally or by UV radiation or electron beams.

18. Release coating or 3D printing obtainable by curing a composition according to claim 17.

Description

EXAMPLES

[0184] The following examples serve only to elucidate this invention for those skilled in the art and do not constitute any restriction whatsoever of the claimed subject matter. .sup.1H-NMR and .sup.29Si-NMR spectroscopy was used for reaction monitoring in all examples.

General Methods

Nuclear Spin Resonance Spectroscopy (NMR Spectroscopy)

[0185] In the context of this invention the .sup.1H-NMR samples are analysed at a measurement frequency of 400 MHz in a Bruker 400 spectrometer equipped with a BBI probe head, dissolved at 22° C. in CDCl.sub.3 and against a tetramethylsilane (TMS) external standard [δ(.sup.1H)=0.0 ppm] .

[0186] In the context of this invention the .sup.29Si-NMR samples are analysed at a measurement frequency of 79.49 MHz in a Bruker Avance III spectrometer equipped with a 287430 sample head with gap width of 10 mm, dissolved at 22° C. in CDCl.sub.3 and against a tetramethylsilane (TMS) external standard [δ(.sup.29Si)=0.0 ppm].

Gas Chromatography (GC):

[0187] The gas chromatograms are recorded on a GC instrument of the GC 7890B type from Agilent Technologies, equipped with a column of the HP-1 type; 30 m×0.32 mm ID×0.25 μm dF (Agilent Technologies no. 19091Z-413E) and hydrogen as carrier gas, with the following parameters: [0188] Detector: FID; 310° C. [0189] Injector: Split; 290° C. [0190] Mode: constant flow, 2 ml/min [0191] Temperature programme: 60° C. at 8° C./min −150° C. at 40° C./min-300° C. 10 min.

Synthesis Examples

Synthesis Example 1 (S1)

a) Preparation of a Linear α,ω-Diacetoxypolydimethylsiloxane of Average Chain Length N=14:

[0192] in a 2L four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 1349.6 g of decamethylcyclopentasiloxane, 157.2 g of acetic anhydride, 22.6 g of acetic acid and 3.01 g of trifluoromethanesulfonic acid are heated to 150° C. with stirring. After stirring for 6 hours at 150° C., the mixture is cooled to 60° C. 30.1 g of anhydrous sodium carbonate are then added. The mixture is stirred for a further hour and then filtered. The filtrate is obtained as a colourless clear acetoxy silicone of average composition M.sup.AcO.sub.2D.sub.12 determined by .sup.29Si-NMR.

b) Preparation of an α,ω-Silicone Acrylate of Average Formula M.sup.Acr.sub.2D.sub.12 where R.sup.1=Propylene and R.sup.2=H:

[0193] in a 500 ml four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 54.66 g of hydroxypropyl acrylate (95% purity, Sigma Aldrich, regioisomeric mixture comprising 25% of the isomer with a primary hydroxyl group (1-hydroxy-2-propyl acrylate) and 75% of the isomer with a secondary hydroxyl group (2-hydroxy-1-propyl acrylate)) is charged with 0.11 g of methylhydroquinone, 0.56 g of trichloroacetic acid (Sigma Aldrich) and 1.41 g of acetic acid (p. a., Baker) and the mixture is stirred. The hydroxypropyl acrylate used here is used without further pre-drying. 226.57 g of the linear α,ω-diacetoxypolydimethylsiloxane of average chain length N=14 and of average formula M.sup.AcO.sub.2D.sub.12 obtained in synthesis example 1 a) are rapidly metered in at room temperature and the reaction mixture is heated to 110° C. On heating, the reaction mixture is clear and monophasic. After stirring for 4 hours at 110° C., the reaction mixture is heated on a rotary evaporator at 100° C. for one hour at an applied vacuum of 4 mbar in order to remove volatile reaction products and/or by-products by distillation. In the four-necked flask, to the distillation bottoms cooled to 80° C. is added 5.6 g of anhydrous sodium carbonate and the mixture is stirred at 80° C. for 2 hours. After cooling, the solid is filtered off through a pleated filter and a clear, colourless liquid product is obtained. The .sup.295i-NMR spectrum of the product shows that the signals of the Si-bonded acetoxy groups are no longer present and that in place thereof the signals of the SiOC-bonded hydroxypropyl acrylate have appeared. The average chain length, calculated from the .sup.295i-NMR spectrum, is N=14. The averaged structure, calculated from the .sup.29Si-NMR spectrum, therefore corresponds to the approximated formula: M.sup.Acr.sub.2D.sub.12 where R.sup.1=propylene (—CH(CH.sub.3)CH.sub.2—/—CH.sub.2CH(CH.sub.3)-) and R.sup.2=H.

Synthesis Example 2 (S2)

[0194] a) Preparation of a Linear α,ω-diacetoxypolydimethylsiloxane of average chain length N=39

[0195] in a 2L four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 1390.3 g of decamethylcyclopentasiloxane, 70.2 g of acetic anhydride, 21.9 g of acetic acid and 2.96 g of trifluoromethanesulfonic acid are heated to 150° C. with stirring. After stirring for 6 hours at 150° C., the mixture is cooled to 60° C. 29.7 g of anhydrous sodium carbonate are then added. The mixture is stirred for a further hour and then filtered. The filtrate is obtained as a colourless clear acetoxy silicone of average composition M.sup.OAc.sub.2D.sub.37 determined by 295i-NMR.

b) Preparation of an α,ω-Silicone Acrylate of Average Formula M.sup.Acr.sub.2D.sub.37 where R.sup.1=Propylene and R.sup.2=H:

[0196] in a 500 ml four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 27.33 g of hydroxypropyl acrylate (95% purity, Sigma Aldrich, regioisomeric mixture having 25% of the isomer with a primary hydroxyl group (1-hydroxy-2-propyl acrylate) and 75% of the isomer with a secondary hydroxyl group (2-hydroxy-1-propyl acrylate)) is charged with 0.13 g of methylhydroquinone, 0.65 g of trichloroacetic acid (Sigma Aldrich) and 1.63 g of acetic acid (p. a., Baker) and the mixture is stirred. The hydroxypropyl acrylate used here is used without further pre-drying. 297.93 g of the linear α,ω-diacetoxypolydimethylsiloxane of average chain length N=39 and of average formula M.sup.AcO.sub.2D.sub.37 obtained in synthesis example 2 a) are rapidly metered in at room temperature and the reaction mixture is heated to 110° C. On heating, the reaction mixture is clear and monophasic. After stirring for 4 hours at 110° C., the reaction mixture is heated on a rotary evaporator at 100° C. for one hour at an applied vacuum of 4 mbar in order to remove volatile reaction products and by-products by distillation. In the four-necked flask, to the distillation bottoms is added 6.5 g of anhydrous sodium carbonate and the mixture is stirred at 80° C. for 2 hours. After cooling, the solid is separated off through a pleated filter and a colourless clear liquid product is obtained. The .sup.29Si-NMR of the product shows that the signals of the Si-bonded acetoxy groups are no longer present and that in place thereof the signals of the SiOC-bonded hydroxypropyl acrylate have appeared. Starting from the average formula M.sup.OAc.sub.2D.sub.37 for the α,ω-diacetoxypolydimethylsiloxane used, it follows accordingly an α,ω-silicone acrylate of the average formula: M.sup.Acr.sub.2D.sub.37 where R.sup.1=propylene (—CH(CH.sub.3)CH.sub.2—/—CH.sub.2CH(CH.sub.3)-) and R.sup.2=H.

Synthesis Example 3 (S3)

[0197] a) Preparation of a Branched Acetoxy Silicone of Average Formula M.sup.AcO.sub.3.5D.sub.22T.sub.2

[0198] In a 1L four-necked flask equipped with KPG stirrer, reflux condenser and internal thermomometer, 329.91 g of a cyclic branched DT siloxane of the approximate formula D.sub.5.45T, 381.52 g of decamethylcyclopentasiloxane, 78.61 g of acetic anhydride, 11.85 g of acetic acid and 1.58 g of trifluoromethanesulfonic acid are heated to 150° C. with stirring. After stirring for 6 hours at 150° C., the mixture is cooled to 60° C. 15.8 g of anhydrous sodium carbonate are then added. The mixture is stirred for a further hour and then filtered. The filtrate is obtained as a colourless clear acetoxy silicone to which can be ascribed an average composition of M.sup.AcO.sub.3.5D.sub.22T.sub.2 according to .sup.29Si-NMR.

b) Preparation of a Silicone Acrylate of Average Formula M.sup.Acr.sub.2.5D.sub.18.7T.sub.2 where R.sup.1=propylene and in a 500 ml four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 54.66 g of hydroxypropyl acrylate (95% purity, Sigma Aldrich, regioisomeric mixture having 25% of the isomer with a primary hydroxyl group (1-hydroxy-2-propyl acrylate) and 75% of the isomer with a secondary hydroxyl group (2-hydroxy-1-propyl acrylate)) is charged with 0.12 g of methylhydroquinone, 0.62 g of trichloroacetic acid (Sigma Aldrich) and 1.55 g of acetic acid (p. a., Baker) and the mixture is stirred. The hydroxypropyl acrylate used here was used without further pre-drying. 255.73 g of the branched terminal acetoxy silicone of average formula M.sup.AcO.sub.3.5D.sub.22T.sub.2 obtained in synthesis example 3 a) are rapidly metered in at room temperature and the reaction mixture is heated to 110° C. On heating, the reaction mixture is clear and monophasic. After stirring for 4 hours at 110° C., the reaction mixture is transferred to a rotary evaporator and is freed of volatile reaction products and/or by-products by distillation at 100° C. for one hour and an applied vacuum of 4 mbar. To this, still on the rotary evaporator, 6.2 g of anhydrous sodium carbonate is added to the distillation bottoms and the distillation is continued at 80° C. for 2 hours. After cooling, the solid is filtered off through a pleated filter and a colourless clear liquid product is obtained. The .sup.29Si-NMR spectrum of the product shows that the signals of the Si-bonded acetoxy groups are no longer present and that in place thereof the signals of the SiOC-bonded hydroxypropyl acrylate have appeared. The averaged structure, calculated from the .sup.29Si-NMR spectrum, corresponds to the formula: M.sup.Acr.sub.2.5D.sub.18.7T.sub.2 where R.sup.1=propylene (—CH(CH.sub.3)CH.sub.2—/—CH.sub.2CH(CH.sub.3)-) and R.sup.2=H.

Synthesis Example 4 (S4)

[0199] a) Preparation of a Branched Acetoxy Silicone of Average Formula M.sup.AcO.sub.5.1D.sub.54.5T.sub.3

[0200] In a 1 L four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 58.84 g of methyltriethoxysilane, 465.95 g of decamethylcyclopentasiloxane and 1.21 g of trifluoromethanesulfonic acid are initially charged and a mixture of 81.42 g of acetic anhydride, 18.19 g of acetic acid are metered in. The mixture is heated stepwise to 150° C. while stirring and the resulting distillate collected. After stirring for 5 hours at 150° C., the mixture is cooled to 60° C. Subsequently, 3.03 g of anhydrous sodium carbonate are added. The mixture is stirred for a further hour and then filtered. The filtrate is obtained as a colourless, clear acetoxy silicone to which can be ascribed an average composition of M.sup.AcO.sub.5.1D.sub.54.5T.sub.3 according to .sup.295i-NMR.

b) Preparation of a Silicone Acrylate of Average Formula M.sup.Acr.sub.3.89D.sub.50.3T.sub.3 where R.sup.1=propylene and R.sup.2=H:

[0201] In a 500 ml four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 42.01 g of hydroxypropyl acrylate (95% purity, Sigma Aldrich, regioisomeric mixture having 25% of the isomer with a primary hydroxyl group (1-hydroxy-2-propyl acrylate) and 75% of the isomer with a secondary hydroxyl group (2-hydroxy-1-propyl acrylate)) are initially charged and stirred with 0.12 g of methylhydroquinone, 0.62 g of trichloroacetic acid (Sigma Aldrich) and 1.54 g of acetic acid (p. a., Baker). The hydroxypropyl acrylate was used here without further pre-drying. 266.43 g of the branched terminal acetoxy silicone of average formula M.sup.AcO.sub.5.1D.sub.54.5T.sub.3 obtained in synthesis example 4 a) are rapidly metered in at room temperature and the reaction mixture is heated to 110° C. On heating, the reaction mixture is clear and monophasic. After stirring for 4 hours at 110° C., the reaction mixture is transferred to a rotary evaporator and is freed of volatile reaction products and/or by-products by distillation at 100° C. and an applied vacuum of 4 mbar for one hour. Then, 6.2 g of anhydrous sodium carbonate is added to the distillation bottoms and the mixture is stirred at 80° C. for 2 hours. After cooling, the solid is filtered off through a pleated filter and a colourless, clear liquid product is obtained. The averaged structure, calculated from the .sup.29Si-NMR spectrum, corresponds to the formula: M.sup.Acr.sub.3.89D.sub.50.3T.sub.3 where R.sup.1=propylene (—CH(CH.sub.3)CH.sub.2—/—CH.sub.2CH(CH.sub.3)-) and R.sup.2=H.

Synthesis Example 5 (S5)

[0202] a) Preparation of a Branched Acetoxy Silicone of Average Formula M.sup.AcO.sub.3.63D.sub.55.8T.sub.2

[0203] In a 1 L four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 42.79 g of methyltriethoxysilane, 516.11 g of decamethylcyclopentasiloxane and 1.25 g of trifluoromethanesulfonic acid are initially charged and a mixture of 63.70 g of acetic anhydride and 18.68 g of acetic acid is metered in. The mixture is heated stepwise to 150° C. while stirring and the resulting distillate collected. After stirring for 5 hours at 150° C., the mixture is cooled to 60° C. Subsequently, 4.4 g of anhydrous sodium carbonate are added. The mixture is stirred for a further hour and then filtered. The filtrate is obtained as a colourless, clear acetoxy silicone to which can be ascribed an average composition of M.sup.AcO.sub.3.63D.sub.55.8T.sub.2 according to .sup.295i-NMR.

b) Preparation of a Silicone Acrylate of Average Formula M.sup.Acr.sub.3.03D.sub.55.09 T.sub.2 where R.sup.1 =propylene and R.sup.2=H:

[0204] In a 500 ml four-necked flask equipped with KPG stirrer, reflux condenser and internal thermometer, 29.18 g of hydroxypropyl acrylate (95% purity, Sigma Aldrich, regioisomeric mixture having 25% of the isomer with a primary hydroxyl group (1-hydroxy-2-propyl acrylate) and 75% of the isomer with a secondary hydroxyl group (2-hydroxy-1-propyl acrylate)) are initially charged and stirred with 0.113 g of methylhydroquinone, 0.57 g of trichloroacetic acid (Sigma Aldrich) and 1.41 g of acetic acid (p. a., Baker). The hydroxypropyl acrylate was used here without further pre-drying. 253.79 g of the branched terminal acetoxy silicone of average formula M.sup.AcO.sub.3.63D.sub.55.8T.sub.2 obtained in synthesis example 5 a) are rapidly metered in at room temperature and the reaction mixture is heated to 110° C. On heating, the reaction mixture is clear and monophasic. After stirring for 4 hours at 110° C., the reaction mixture is transferred to a rotary evaporator and is freed of volatile reaction products and/or by-products by distillation initially at 100° C. and an applied vacuum of 2 mbar. After the start of distillation, the temperature is slowly increased to 130° C. and distillation continued at 130° C. and 2 mbar for 3 h. Then, 2.4 g of anhydrous sodium carbonate and 0.02 g of dimethylhexadecylamine are added to the distillation bottoms and the mixture is stirred at 80° C. for 2 hours. After cooling, the solid is filtered off through a pleated filter. The averaged structure, calculated from the .sup.29Si-NMR spectrum, corresponds to the formula: M.sup.Acr.sub.3.03D.sub.55.09T.sub.2 where R.sup.1=propylene (—CH(CH.sub.3)CH.sub.2—/—CH.sub.2CH(CH.sub.3)-) and R.sup.2=H. The cyclic siloxane contents determined by gas chromatography are <0.02% D4, <0.02% D5 and <0.26% D6. The total chlorine content of the product resulting from residual contents of trichloroacetic acid is 391 ppm.

Comparative Example 1 (V1) (Non-Inventive):

[0205] preparation of an SiC-bonded am-silicone acrylate of chain length N=28.6 (corresponds to comparative example 1 of WO 2017/080747 A1):

[0206] In a heatable 500 ml four-necked flask provided with KPG stirrer, internal thermometer and a gas inlet pipe, 227.7 g of a linear epoxysiloxane bearing SiC-bonded epoxy-functional radicals in the am-position and having an average chain length N=28 are initially charged together with 0.02 g of methylhydroquinone, 0.02 g of para-methoxyphenol, 0.49 g of aqueous Cr(III) acetate solution (50 per cent by weight) and 15.2 g of acrylic acid and 0.8 g of acetic acid with stirring. The reaction mixture is then heated to 120° C. with introduction of a moderate airflow. Samples are taken during the reaction and the degree of conversion determined on the basis of the respective acid number.

[0207] After a reaction time of 18 hours, the reaction is terminated at a conversion of 93%. The mixture is allowed to cool to 25° C., then filtered and the filtrate is subjected to distillation at 120° C. for removal of volatiles. The .sup.1H- and .sup.29Si-NMR spectra of the distillation residue verify conversion of 91% of the epoxy groups used to the corresponding carboxylic esters. The viscosity of the product obtained is 1026 mPas.

Performance Testing:

Preparation of Release Coatings:

[0208] Performance testing both of the SiOC-based silicone acrylates prepared in synthesis examples S1 to S3 and of the SiC-linked silicone acrylate prepared in comparative example V1 is carried out in formulations for release coatings. Release coatings are known from the prior art, particularly as abhesive coatings on sheetlike carriers and specifically in this case for their use in adhesive tapes or label laminates.

[0209] To prepare formulations for release coatings, 98 g of each of the silicone acrylates from synthesis examples S1 to S5 and of comparative example V1 is intensively mixed each with 2 g of photoinitiator TEGO® A18 (Evonik Industries AG).

[0210] Additional release coating formulations are prepared in which in each case 30 g of TEGO® RC 711 (Evonik Industries AG) with 68 g of each of the silicone acrylates from synthesis examples S1 to S5 and from comparative example V1 were each intensively blended with 2 g of photoinitiator TEGO® A18 (examples S1a to S5a). TEGO® RC 711 is an acrylate-functional organosiloxane which, according to the data from the accompanying technical data sheet, ensures good fixing of the coating composition to the substrate.

[0211] Additional release coating formulations are prepared in which in each case 30 g of components S1 and S3 are mixed in each case with 68 g of component S2, S4, S5 and 2 g of photoinitiator TEGO® A18 (Evonik Industries AG) (examples S2/1, S2/3, S4/1, S4/3, S5/1 and S5/3).

[0212] The coating compositions thus prepared are applied to a sheetlike carrier. In all performance examples, this consists of a 50 cm wide, biaxially stretched polypropylene film (BOPP) which, in each case prior to the application of the coating composition using a generator power of 1 kW, was subjected to a corona pre-treatment. The coating materials are applied using a 5-roll coating unit from COATEMA® (Coating Machinery GmbH, Dormagen, Germany) with a weight per unit area of ca. 1 g/m.sup.2 and were cured by the action of UV light from a medium-pressure mercury vapour lamp from IST® Metz GmbH (Nurtingen, Germany) at 60 W/cm and at a belt speed of 100 m/min under a nitrogen atmosphere with a residual oxygen content of less than 50 ppm.

[0213] The samples thus coated are subjected to a test with respect to rub-off, release value and residual adhesive force.

Rub Off:

[0214] The adhesion of the cured coating to the carrier material is verified by vigorous rubbing with the thumb on the coating. In case of insufficient adhesion, abrasion forms in the form of rubbery looking crumbs. Such crumbs ought not to be produced even on intense rubbing. The test is carried out by a trained panel. The assessment is categorized in ranges from 1 to 5, where 1 is very good and 5 is rather poor adhesion to the carrier material.

Release Force:

[0215] The release effect with respect to adhesive materials, in industrial application usually in the form of adhesive tapes or labels, is expressed by the release force (RF), with a low release force describing a good release effect. The release force is dependent on the quality of the release coating, on the adhesive itself and on the test conditions. For evaluation of release coatings, therefore, identical adhesives and test conditions ought to be present. For the determination of the release forces, adhesive tapes or label laminates are cut to a width of 2.5 cm and then the adhesive side is applied in each case to the silicone coating under test. This test is carried out in accordance with FINAT Handbook, 8th Edition, The Hague/NL, 2009 under designation FTM 10, with the modification that storage is carried out at 40° C. under pressure. The adhesive tape employed is Tesa®7475 (trade mark of Tesa SE, Hamburg, Germany). The values reported are in each case average values from a five-fold determination and are stated in units [cN/2.5 cm]. Systems with a release force below 10 cN/2.5 cm are classified as easy release and are typically suitable for many applications such as label laminates for example.

Residual Adhesive Force:

[0216] The residual adhesive force (RAF) is determined according to the test protocol FTM 11 in FINAT Handbook 8th Edition, The Hague/NL, 2009 with the exception that storage of the test adhesive strip in silicone contact is carried out for one minute and the standard surface is an untreated

[0217] BOPP surface. The adhesive tape employed is Tesa®7475 (trade mark of Tesa SE, Hamburg, Germany). The residual adhesive force is a measure of the crosslinking of the silicones. If non-polymerized and thus migratable silicone constituents are present, residual adhesion force values decrease with increasing proportion of such components. Values above 80% are regarded as acceptable. The results of the rub off test, the release forces and the short term residual adhesive forces (RAF) are presented in Table 1.

TABLE-US-00001 TABLE 1 Results of performance testing (rub off in notes 1 to 5; release forces (RF) in cN/2.5 cm after 24 hours storage at 40° C.; residual adhesive force (RAF) in %). RF Rub (TESA ® 7475) RAF Example off [cN/2.5 cm] [%] V1 5 8 89 S1 2 26 91 S2 5 8 89 S3 2 25 98 S4 5 10 92 S5 5 7 89 V1a 2 8 90 S1a 1 31 90 S2a 2 9 88 S3a 1 33 97 S4a 1 11 93 S5a 1 8 91 S2/1 2 9 89 S2/3 2 10 87 S4/1 1 9 88 S4/3 2 10 91 S5/1 2 8 87 S5/3 2 7 92

[0218] It is apparent from Table 1 that inventive examples S2, S4 and S5 enable an equally low release force as comparative example V1. However, a disadvantage of the coatings based on S2, S4, S5 and Vi is their low adhesion to the substrate (rub-off). However, this can be significantly improved by addition of a customary adhesion component, here TEGO® RC 711, without other properties (RF and RAF) being negatively influenced (example coatings S2a, S4a, S5a and V1a).

[0219] The two inventive examples S1 and S3 already result in good adhesion without an additional adhesion component. The release forces are for applications that are somewhat high, where a light release behaviour is especially important. However, there are special applications in which this release behaviour is also appreciated. Moreover, S1 and S2 may serve as replacement for TEGO® RC 711 in its function as adhesion component which is evident from examples S2/1, S2/3, S4/1, S4/3, S5/1 and S5/3.

[0220] All inventive examples exhibit good curing which is evident from the short term residual adhesive forces (RAF). The components prepared according to the invention therefore meet all important requirements for use in release coatings. They can—adapted to the respective system—be used either as adhesion components or as components with low release forces.