Water repellent organosilicon materials

Abstract

A process for increasing the hydrophobicity of a porous product by treating the product, or a composition providing for the product, with a water repellent material, characterized in that the porous product or a composition providing the product, is treated with an aqueous suspension of microcapsules where the microcapsules comprise a water repellent organosilicon core material selected from an organosilane, a partially condensed organosilane and a branched siloxane resin, and a shell of a silicon-based network polymer comprising silica units.

Claims

1. A process for increasing the hydrophobicity of a porous product by treating the product, or a composition providing for the product, with a water repellent material, characterised in that the porous product or a composition providing the product is treated with an aqueous suspension of microcapsules where the microcapsules comprise a water repellent organosilicon core material selected from the group consisting of an organosilane, a partially condensed organosilane, and a branched siloxane resin, and a shell of a silicon-based network polymer comprising silica units wherein the product is selected from the group consisting of cementitious substrates, cementious compositions, clay-based bricks, clay-based compositions, gypsum-based substrates, lime-based substrates, and wood-based substrates.

2. A process according to claim 1 wherein the water repellent organosilicon core material is an organosilane comprising at least one silicon-bonded alkyl group having 1 to 30 carbon atoms, or a partial condensation product of such an organosilane.

3. A process according to claim 2 wherein the water repellent organosilicon core material is an alkyltrialkoxysilane in which each alkoxy group has 1 to 4 carbon atoms.

4. A process according to claim 2 wherein the silicon-bonded alkyl group is an octyl group.

5. A process according to claim 1 wherein the water repellent organosilicon core material is a siloxane resin comprising siloxane units of the formula RSiO.sub.3/2 where R represents an alkyl group.

6. A process according to claim 5 wherein the groups R in the siloxane units of the formula RSiO.sub.3/2 comprise alkyl groups having 1 to 30 carbon atoms.

7. A process according to claim 1 wherein the water repellent organosilicon core material is a siloxane resin comprising siloxane units of the formula RSiO.sub.3/2 where R represents an aryl group.

8. A process according to claim 1 where the microcapsules are obtained by the addition of tetraalkoxysilane to an aqueous emulsion of a water repellent organosilicon material selected from the group consisting of an organosilane, a partially condensed organosilane, and a branched siloxane resin, whereby the tetraalkoxysilane condenses and polymerises at the interface of droplets in the emulsion to form microcapsules.

9. A process according to claim 8 where a quaternised aminoalkylalkoxysilane is added to the aqueous emulsion before or simultaneously with the tetraalkoxysilane.

10. A process according to claim 1 wherein microcapsules comprising a water repellent organosilicon core material selected from the group consisting of an organosilane, a partially condensed organosilane, and a branched siloxane resin, and a shell of a silicon-based network polymer comprising silica units are added to the cementitious composition and the composition is shaped and hardened to form a cementitious product.

11. A process according to claim 10 for making a water repellent aerated cement product, wherein the microcapsules are added to a foamable cementitious composition.

12. A process according to claim 1 wherein microcapsules comprising a water repellent organosilicon core material selected from the group consisting of an organosilane, a partially condensed organosilane, and a branched siloxane resin, and a shell of a silicon-based network polymer comprising silica units are added to the clay based composition and the composition is shaped and hardened to form a brick or tile product.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1 and 2 relate to evaluation of efficiency in hydrophobing wood substrates.

(2) FIG. 1A is a schematic view of the vacuum assembly (105) where the wood blocks (101) are placed for 20 minutes, at 40 mbar, in the glass container, under the metallic wire (102). Connect (103) is connected to the water repellent solution (104), but closed (double headed arrow).

(3) FIG. 1B is a schematic view of the addition of water repellent composition (104) to the assembly at atmospheric pressure via inlet (103).

(4) FIG. 1C is a schematic view of the impregnation for 20 minutes at atmospheric pressure.

(5) FIG. 2 is a schematic view of the absorption assembly where the wood blocks (201) as treated above are placed upright (on their smallest section—27×18 mm) on 2 pieces of glass (202), ensuring only 2 mm of the wood block is in contact with water (204) in container (203).

EXAMPLES

Example 1

(6) 33.3% octyltriethoxysilane was emulsified in 66.4% water containing 0.1% N-octadecyl-N,N-dimethyl-trimethoxysilylpropylammonium chloride cationic surfactant using a high shear rotor stator mixer. 1% TEOS was added to the emulsion while stirring. Microcapsules of median diameter 372 nm were produced in suspension. The microcapsules comprised a core of octyltriethoxysilane and a shell of a network polymer of TEOS comprising silica units.

(7) The suspension of microcapsules was diluted with water so that it contained 5% octyltriethoxysilane. The diluted suspension (2.5 g) was sprayed onto six surfaces of 15×15 cm fibre reinforced cement boards and was allowed to dry and react under ambient conditions for 1 week. The water absorption of the fibre reinforced cement boards was tested by immersing the pieces of boards under a water height of 2 cm. Water absorption was measured after 1, 3, 6 and 24 hours immersions in water. The results are shown in Table 1.

Example 2

(8) Example 1 was repeated further adding 2% TEOS to the emulsion.

Comparative Examples 1 and 2

Comparative Example C1

(9) the cationic emulsion of octyltriethoxysilane as prepared in Example 1 was diluted to 5% active material and was sprayed onto fibre reinforced cement boards without any treatment with TEOS.

Comparative Example C2

(10) 39.4% octyltriethoxysilane and 13.1% of an octyl T resin were emulsified in 41.2% water containing 4.8% polyoxyethylene lauryl ether non ionic surfactants using a high shear rotor stator mixer. This non ionic emulsion of octyltriethoxysilane was diluted to 5% active material to compose Comparative example C2 and was sprayed onto fibre reinforced cement boards.

(11) The results of Examples 1 and 2 and Comparative examples C1 and C2 are shown in Table 1. The water absorption of untreated fibre reinforced cement board was also measured.

(12) TABLE-US-00001 TABLE 1 Water Water Water Water absorption absorption absorption absorption Example 1 hour 3 hours 6 hours 24 hours C1 0.40% 0.64% 0.92% 2.18% C2 0.55% 0.92% 1.19% 2.13% 1 0.37% 0.60% 0.81% 1.54% 2 0.33% 0.59% 0.81% 1.63% Untreated 1.57% 5.23% 7.69% 10.05%

(13) It can be seen from Table 1 that the encapsulated organosilanes of Examples 1 and 2 clearly give lower water absorption (better water repellency) than the emulsion of the same organosilane at the same concentration used in Comparative examples C1 and C2.

Example 4

(14) 30.3% octyltriethoxysilane was emulsified in 60.1% water containing 0.3% Arquad 16-29 cationic surfactant and 0.2% Volpo L-3 non-ionic surfactant using a high shear rotor stator mixer. 9.1% TEOS was added to the emulsion while stirring. The microcapsules comprised a core of octyltriethoxysilane and a shell of a network polymer of TEOS comprising silica units.

(15) Mortar blocks were prepared by mixing 450 g of CEM I 42.5 R cement, 1350 g of sand, 180 g of water and hydrophobic additives. The suspension of microcapsules from Example 4 and the non ionic emulsion of silane described in Comparative example C2 were added in the mortar slurry such as to reach an addition level of active material of 0.1% vs the mortar dry composition (cement+sand). Reference mortar block containing no hydrophobic additives were prepared as well.

(16) Mortar blocks (40×40×160 mm) were cured for 28 days at a temperature of 25° C. and at 100% relative humidity and then dried overnight at 50° C. and cooled down at room temperature before testing.

(17) Dry blocks were weighed (W.sub.dry) and then immersed for a period of one hour in water, with the top surface of the block at a depth of 3 cm below the water surface. After one hour the block was reweighed (W.sub.wet). The blocks were then re-immersed for 2 additional hours (to reach an immersion time of 3 hours), and reweighed. The same sequence is then re-applied to reach immersion time of 24 hours. Results in Table 2 are obtained by use of the following equation wherein:

(18) $\mathrm{Percentage}\mathrm{Water}\mathrm{Pick}\mathrm{Up}\left(\mathrm{WPU}\%\right)=\frac{\left(W_{\mathrm{wet}}\right)-\left(W_{\mathrm{dry}}\right)\times 100}{\left(W_{\mathrm{dry}}\right)}$

(19) TABLE-US-00002 TABLE 2 Water Water Water Water absorption absorption absorption absorption Example 1 hour 3 hours 6 hours 24 hours Comparative 0.41% 0.51% 0.59% 0.82% example C2 Example 4 0.22% 0.30% 0.34% 0.57% Untreated 1.47% 2.14% 2.55% 2.94%

Example 5

(20) 30.3% octyl T resin methoxy functionalised was emulsified in 60.1% water containing 0.3% Arquad 16-29 cationic surfactant and 0.2% Volpo L-3 non-ionic surfactant using a high shear rotor stator mixer. 9.1% TEOS was added to the emulsion while stirring. The microcapsules comprised a core of silsesquioxane-based active material and a shell of a network polymer of TEOS comprising silica units.

(21) The suspension of microcapsules was diluted with water so that it contained 2% octyl T resin methoxy functionalised. The diluted suspension was sprayed onto the six surfaces of another type of fibre reinforced cement boards and was allowed to dry and react under ambient conditions for 2 days. The water absorption of the fibre reinforced cement boards was tested by immersing the pieces of boards under a water height of 2 cm. Water absorption was measured after 1, 3, 6 and 24 hours immersions in water. The results are shown in Table 3.

(22) TABLE-US-00003 TABLE 3 Water Water Water Water absorption absorption absorption absorption Example 1 hour 3 hours 6 hours 24 hours Example 4 0.6% 1.2% 1.7% 3.3% Example 5 0.9% 1.7% 2.6% 6.0% Untreated 28.9% 29.3% 29.5% 30.3%

Example 6

(23) 33.3% octyl T resin ethoxy functionalised was emulsified in 56.4% water containing 0.1% N-octadecyl-N,N-dimethyl-trimethoxysilylpropylammonium chloride cationic surfactant using a high shear rotor stator mixer. 10% TEOS was added to the emulsion while stirring. The microcapsules comprised a core of silsesquioxane and a shell of a network polymer of TEOS comprising silica units.

(24) Aerated autoclaved blocks were prepared by mixing 40% of fine sand (<10 μm particle size), 45% CEM I 52.5 R white cement, 10% calcium hydroxide, 5% calcium sulphate hemihydrates and 0.7% of aluminium paste. Water to solid ratio is set at a value of 1.

(25) All components were added as slurry in water and mixed sequentially. Aluminium is added at the latest stage. The mixture is then placed in an oven overnight at 50° C.

(26) Following the reaction of aluminium paste in caustic medium, hydrogen is released and generates bubbles which are entrapped in the cement matrix which is setting at the same time. Suspension of microcapsule from example 6 was added in the slurry before addition of aluminium such as to reach an active content of 1% vs the solid composition.

(27) Volume of the slurry after expansion and hardening is measured. The height of the hard cake obtained when no aluminium is added in the slurry is given as reference as well as the height of the hard cake obtained in the presence of aluminium but with no additive.

(28) Extend of volume expansion is given in Table 4.

(29) Block samples are cut so they have more or less the same weight and shape. They are weighted and then placed in a container filled with water so they are recovered by a few centimeters of water. A grid is placed over the samples to maintain them immersed (otherwise, the samples are floating).

(30) The samples are weighted after 1, 6 and 24 hours of immersion. Just before the weighing, they are quickly wiped to remove unabsorbed water. The percentage of water uptake is calculated like this:

(31) $\%\mathrm{of}\mathrm{water}\mathrm{uptake}\mathrm{after}x\mathrm{hours}=\frac{\mathrm{Wx}-\mathrm{Wi}}{\mathrm{Wi}}.Math.100$
with Wx being the sample weight after x hours of immersion and Wi the initial sample weight.

(32) Water uptakes of blocks treated with suspension of microcapsule are given in table 4. For reference, water uptakes of blocks modified with 1% of the neat octyl T resin are given as well.

(33) TABLE-US-00004 TABLE 4 Water Water Water Cake height absorption absorption absorption Example (cm) 1 hours 6 hours 24 hours Neat octyl T  9.1 cm 49% 53% 54% resin Example 6 10.3 cm 51% 58% 55% No additive 10.5 cm 113% 118% 119% No aluminium  4.3 cm no additive

(34) Table 4 demonstrates clearly that addition of octyl T resin in the aerated blocks has a strong impact on the water absorption of the blocks. Water uptake is significantly decreased. Addition of suspension of microcapsule of the same octyl T resin is leading to the same reduction of water uptake, demonstrating that the active material is released during the cure mechanism; enable reaction of the active material with the cementitious matrix.

(35) Extend of cake extension demonstrates that addition of the neat octyl T resin has a negative impact on slurry volume expansion. Volume of hardened cake is only 9.1 cm when the octyl T resin is added while volume of hardened cake in the absence of the resin is 10.5 cm. Suspension of microcapsule of the same octyl resin surprisingly has no negative impact on the slurry expansion. Height of hardened cake in the presence of the suspension of microcapsule is 10.3 cm, so almost similar to the unmodified slurry. This strongly suggests the microencapsulation enable the active material to be protected during the foaming and expansion process which last for about one hour. Rupture of the microcapsule occurs later on enable the whole cementitious matrix to be evenly treated leading to a strong reduction of water uptake.

Example 7

(36) 33.3% of water and 0.1% of cationic surfactant (Hexadecyltrimethylammonium Chloride, CTAC) are mixed at 200 RPM for 3 minutes with a propeller lab mixer. MQ resin solubilised in 100 mPa.Math.s polydimethylsiloxane (40% wt MQ resin/60% wt polydimethylsiloxane) are mixed in the surfactant solution with the same mixer at 400 RPM for 3 minutes. The dispersion is further mixed with a high shear mixer (homogenizer). The pH of the dispersion is adjusted to =3. 10% tetraethoxysilane is added drop wise under gentle mixing. The microencapsulation is left for 24 hours to leave time to build up the capsule around the active materials droplets.

Example 8

(37) 33.3% of water and 0.1% of cationic surfactant (Hexadecyltrimethylammonium Chloride, CTAC) are mixed at 200 RPM for 3 minutes with a propeller lab mixer. MQ resin solubilised in octyl triethoxysilane (57% wt MQ resin/43% wt octyltriethoxysilane) are mixed in the surfactant solution with the same mixer at 400 RPM for 3 minutes. The dispersion is further mixed with a high shear mixer (homogenizer). The pH of dispersion is adjusted to =3. 10% tetraethoxysilane is added drop wise under gentle mixing. The microencapsulation is left for 24 hours to leave time to build up the capsule around the active materials droplets.

(38) Examples 7 and 8 were tested for efficiency in hydrophobing wood substrates following a method of wood treatment via impregnation, and subsequent water absorption of said treated wood, versus untreated wood.

(39) Impregnation conditions: Wood: blocks of white pine of size: 50×27×18 mm The blocks of pine are dried in an oven at 40° C., until a constant weight is recorded (intervals of 24 hours). The blocks are placed under vacuum for 20 minutes, at 40 mbar (FIG. 1A). The water repellent composition is allowed to enter within the flask, submerging the wood blocks (FIG. 1B). The blocks are immersed in the water repellent composition (1% active material) for 20 minutes, at atmospheric pressure (FIG. 1C). The blocks are then removed and tapped dried with paper, their weight is recorded. The blocks are then dried for 4 days in an oven at 40° C.

(40) The impregnation level is measured by weight difference before impregnation and after impregnation+drying steps.

(41) Effectiveness of the water repellent material: The blocks as treated above are placed upright (on their smallest section—27×18 mm) on 2 pieces of glass, ensuring only 2 mm of the wood block is in contact with water. Capillary forces will drive water absorption. The blocks are then removed, tapped dried with paper, weighed and placed again on the glass rods. Weight is then recorded after 1, 3, 6, 8 and 24 hours contact with water

(42) Weight absorption is calculated as a percentage based on the weight before absorption and the weight after absorption of water.

(43) Examples 7 and 8 show reduced water uptake versus untreated wood, as disclosed in Table 5, already after 1 hour of water contact, and up to until after 24 hours of water contact.

(44) TABLE-US-00005 TABLE 5 Water uptake (% of dry wood samples weight) as a function of time (hours) sample 0 h 1 h 3 h 6 h 8 h 24 h Example 7 0 1.6 2.9 4.2 4.9 8.0 Example 8 0 1.7 3.1 4.4 5.1 8.4 No 0 15.5 21.3 26.6 29.4 41.5 treatment