CEMENT-CONTAINING COMPOSITION CONTAINING OLIGOMERIC DIALKOXYSILANES

Abstract

A cement-containing composition includes a proportion of 0.05% by weight to 1% by weight, based on the cement content, of an organosilicon compound(S). The organosilicon compound contains at least 70% by weight of units of the formula (1), R.sup.1R.sup.2 (OR.sup.3).sub.xSiO.sub.(2-x)/2 (1). In formula 1, R.sup.1 is a methyl group, R.sup.2, in all units of the formula (1), may be identical or different and is a monovalent, SiC-bonded, aliphatic hydrocarbon radical having 4 to 22 carbon atoms, R.sup.3, in all units of the formula (1), may be identical or different and is a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms, and x is 0 or 1.

Claims

1-6. (canceled)

7. A cement-containing composition comprising a proportion of 0.05% by weight to 1% by weight, based on the cement content, of an organosilicon compound(S) consisting of at least 70% by weight of units of the formula (1)
R.sup.1R.sup.2(OR.sup.3).sub.xSiO.sub.(2-x)/2(1), where R.sup.1 is a methyl group, R.sup.2 in all units of the formula (1) may be identical or different and is a monovalent, SiC-bonded, aliphatic hydrocarbon radical having 4 to 22 carbon atoms, R.sup.3 in all units of the formula (1) may be identical or different and is a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms, and x is 0 or 1.

8. The composition as claimed in claim 7, in which R.sup.2 is an alkyl radical having 8 to 16 carbon atoms.

9. The composition as claimed in claim 7, in which the organosilicon compounds(S) are mixtures of linear compounds of the formula (1a) and cyclic compounds of the formula (1b), ##STR00002## where n has a value from 1 to 100 and m has a value from 3 to 100, and R.sup.1 and R.sup.2 are as defined in claim 1.

10. The composition as claimed in claim 7, in which R.sup.3 is hydrogen or a methyl or ethyl radical.

11. The composition as claimed in claim 7, which is a mortar or concrete.

12. A method for the bulk hydrophobization of cement-containing compositions in which added to the cement-containing compositions, before they have set, is a proportion of 0.05% by weight to 1% by weight, based on the cement content, of organosilicon compound(S) consisting of at least 70% by weight of units of the formula (1)
R.sup.1R.sup.2(OR.sup.3).sub.xSiO.sub.(2-x)/2(1), where R.sup.1 is a methyl group, R.sup.2 in all units of the formula (1) may be identical or different and is a monovalent, SiC-bonded, aliphatic hydrocarbon radical having 4 to 22 carbon atoms, R.sup.3 in all units of the formula (1) may be identical or different and is a hydrogen atom or an alkyl radical having 1 to 4 carbon atoms, and x is 0 or 1.

Description

EXAMPLE 1: PREPARATION OF OLIGOMERIC OCTYLMETHYLDIMETHOXSILANE

[0043] A 1000 ml three-necked flask equipped with a heating means, stirrer, dropping funnel, and reflux condenser is initially charged with 474 g (2.17 mol) of octylmethyldimethoxsilane (commercially available from ABCR, Karlsruhe, Germany) and heated to 80 C. At this temperature, 1.98 g of 25% aqueous HCl is added from the dropping funnel at a constant rate over a period of 10 min with intensive stirring, this being accompanied by the initial development of turbidity (two-phase system) in the reaction mixture. The reaction mixture is stirred at 80 C. for a further 30 min, becoming clear again a few minutes after the end of the addition.

[0044] 46.9 g of water is then added at the same temperature over a period of 95 min. A discernible exothermic reaction develops, causing the reaction temperature to rise to 83 C. The reaction mixture remains clear during the metered addition of the first 20 g, after which it becomes turbid (two-phase system).

[0045] Low boilers (HCl-acidic ethanol) are then first distilled off at ambient pressure (1013 mbar), this being accompanied by a rise in the bottoms temperature to 110 C. As soon as no more distillate is being produced, the pressure is gradually reduced to approx. 10 mbar and the distillation continued until there is again no more distillate being produced. A total of about 135 g of distillate is obtained. The residue in the flask is single-phase and clear.

[0046] The residue in the flask is heated again to 80 C. and treated with 0.2 g of 25% aqueous HCl, as a result of which the reaction mixture again initially becomes slightly turbid and then clears again when stirred for 30 min at 80 C. after the addition.

[0047] Then, at the same temperature, 4.7 g of water is added over a period of 5 min and the mixture is stirred for a further 2 h. The reaction mixture remains clear during this time.

[0048] Finally, low boilers are first distilled off at ambient pressure (1013 mbar), this being accompanied by a rise in the bottoms temperature to 110 C. As soon as no more distillate is being produced, the pressure is gradually reduced to approx. 4 mbar and the distillation continued until there is again no more distillate being produced. A total of about 7 g of distillate is obtained.

[0049] The obtained product is single-phase and clear. It has a viscosity at 23 C. of 19.8 m.Math.Pas. 1H-NMR shows it to consist of approx. 40% of cyclic oligosilane compounds and approx. 60% of linear oligosilane compounds. The proportion of SiOH chain ends is 0.07% by weight and the proportion of SiOCH.sub.3 chain ends is approx. 0.8% by weight (calculated as Si.sub.1/2OH and Si.sub.1/2OCH.sub.3 respectively). The total chlorine content in the product is below 0.05% by weight.

EXAMPLE 2: PRODUCTION OF TEST SPECIMENS

[0050] The test specimens are produced on a planetary mixer from Toni-Technik according to the following scheme: [0051] slow mixing of cement and sand (30 sec) [0052] addition of water while mixing slowly (30 sec) [0053] addition of additive while mixing slowly (30 sec) [0054] intensive mixing (30 sec) [0055] pause (90 sec) [0056] intensive mixing (60 sec)

[0057] The extent of spread of the mortar mixtures produced is 17.250.25 cm.

[0058] The composition of the mortar mixtures is shown in Table 1.

TABLE-US-00001 TABLE 1 Composition of the test specimens Cement CEM I Additive Example 42.5 R Sand* Water Additive content** 2-1*** 900 g 2700 g 425 g 2-2 900 g 2700 g 425 g 1.8 g of siloxane 0.2% by from example 1 weight 2-3 900 g 2700 g 425 g 4.5 g of siloxane 0.5% by from example 1 weight 2-4*** 900 2700 425 4.5 g of monomeric 0.5% by octyltriethoxysilane weight 2-5 900 2700 425 4.5 g of oligomeric 0.5% by octyltriethysilane weight having a viscosity of ~60 mPa .Math. s *standard sand according to DIN EN 196-1 **based on the amount of cement added. ***noninventive

[0059] Six test samples having dimensions of 160 mm40 mm40 mm were produced from each mortar mixture.

EXAMPLE 3: DETERMINATION OF CAPILLARY WATER ABSORPTION IN ACCORDANCE WITH DIN EN 1015-18

[0060] The test specimens are produced in accordance with DIN EN 1015-11, stored at 23 C. and 50% humidity, and after 27 days the long sides of the test specimens are sealed with a sealant. This is followed after 28 days by storage in water, by placing the test specimens in a dish with the unsealed side facing down in an immersion depth of 10 mm.

[0061] The results are shown in Table 2.

EXAMPLE 4: DETERMINATION OF COMPRESSIVE STRENGTH IN ACCORDANCE WITH DIN EN 1015-11

[0062] This test is performed using the fragments of the test specimens from the measurement of flexural strength. The test specimen is inserted into the testing machine such that one molded side of the specimen is in contact with each of the load surfaces of the testing machine. The load is applied in an impact-free manner and increased steadily until break occurs. From the maximum load (in N) is calculated the compressive strength (in N/mm2).

[0063] The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Results of the tests according to examples 3 and 4 on the test specimens from example 2. Capillary Reduction Produced water in water Compressive according Dosing absorption absorption strength to example additive [g/m2] [%] [N/mm2] 2-1* 1773 47.0 2-2 0.2% by 671 62 47.4 weight 2-3 0.5% by 352 80 48.4 weight 2-4* 0.5% by 281 84 39.1 weight 2-5 0.5% by 554 68 41.1 weight *noninventive