Smoothing agent for groutings.

The present invention relates to the use of certain aqueous, in particular aqueous-alcoholic solutions for smoothing the surfaces of sealing compounds which have been introduced into joints, in particular in buildings.

Joint sealants of various types are used extensively both in the construction industry and in related branches of technology. In general, these masses are pressed out of suitable containers, in particular cartridges, directly into the joint to be sealed.

When the joints are sprayed out with the masses, so-called blowholes often occur, and it is also very difficult to obtain uniformly smooth surfaces at all times. Therefore, the surfaces of the sealing compounds must be subjected to a smoothing surface treatment before the compound solidifies as such. At the same time, the sealant is pressed firmly into the joints and any voids or imperfections are filled in, as well as an intensive contact of the sealant with the substrate and thus better adhesion.

A suitable smoothing tool such as a spatula, smoothing wood or the like is usually used for smoothing, although it cannot be ruled out that the strong pressure exerted by the smoothing tool also results in adhesion between it and the joint sealing material.

For this reason, a wide variety of materials are used in smoothing as a release and lubricant depending on the type of sealant. In the simplest case, water is used, which is often improved for this purpose by adding wetting agents. Suitable wetting agents are, for example, soap solutions made from alkali salts of fatty acids, in particular sodium and potassium soaps, but also anionic wetting agents such as are widely used as household dishwashing detergents.

A disadvantage of this addition of surface-active substances (detergents) is their emulsifying effect, which they have in particular with respect to sealants based on filled aqueous dispersions. This can even go so far that with certain dispersions, especially when there is a high concentration of detergents, the surface of the sealant to be smoothed is washed out, which on the one hand leads to damage to the sealant and on the other hand can lead to considerable contamination of the adjacent building materials.

It was also known in the prior art to use aqueous solutions of polyethylene oxides as lubricants against metallic surfaces when machine-working water-containing ceramic masses from unfired clay (US Pat. No. 4,171,337).

The object of the present invention was therefore to find such smoothing agents for treating surfaces of sealing compounds which are based both on water-free jointing compounds, for example based on silicone or polysulfide, and for aqueous dispersions, for example on the basis of polyacrylates, and which do not have the disadvantages described above.

According to the invention, an aqueous, in particular aqueous-alcoholic solution of water-soluble polymers from the group consisting of polyethylene oxide, polyacrylamide, polyacrylic acids or their salts and cellulose derivatives having a molecular weight between 100,000 and 5,000,000 is now used as an aid for mechanical smoothing of surfaces of sealants which have not yet hardened Joints used.

It has proven to be particularly advantageous to use polyethylene oxide or polyethylene glycol of the specified molecular weight as the water-soluble polymer. The use concentration of the aqueous or aqueous-alcoholic solution should preferably be between about 0.1 to 10% by weight, based on the total solution. It may be advantageous to first prepare a more concentrated solution and to dilute it to the specified concentration for use, for example with water. It can easily be determined by hand tests which concentration gives the best effect for which polymer. The alcohols used to prepare the solution should be lower aliphatic water-soluble alcohols with 1 to 3 hydroxyl groups per molecule. For practical reasons, volatile alcohols are primarily considered here, such as lower aliphatic monoalcohols, propyl alcohol or isopropyl alcohol being preferred for practical and toxicological reasons. The use of other polyhydric alcohols such as glycol or glycerol or trimethylolpropane is easily possible. However, it should be borne in mind that, in particular, the polyfunctional alcohols are relatively non-volatile and can penetrate into the surface of the joint sealant to be smoothed and remain there.

In addition to the polyethylene oxide or polyethylene glycol of the specified molecular weight, polyacrylamide or copolymers of acrylamide with substituted acrylamide or with free acrylic acid or methacrylic acid can also be used. Furthermore, the use of water-soluble salts and polyacrylic acids, which can be modified in a known manner, seems to be considered. The water-soluble cellulose derivatives can be modified by various substitution such as by wide alkoxylation. It can also be expedient to introduce quaternary ammonium groups into the cellulose derivative by suitable substitution.

The sealing compounds are known substances which are commercially available for this purpose and which are crosslinked either in the air by the action of moisture, for example in the case of silicone or polyurethane compounds, or else from two-component systems, such as in the case of the polysulphide compounds the action of oxidizing agents linking the prepolymers to one another is achieved.

The solvent-containing joint sealants based on styrene-butadiene graft polymers and the aqueous dispersions based, for example, on polyacrylate and methacrylates, which can also be the base material for joint sealants, differ from these substances which harden by chemical reaction. Such sealants generally have a relatively high content of fillers. The so-called curing of these compositions was carried out by evaporation of the solvent or water from the dispersion, ie by simply drying the joint sealant. A substantial amount of fillers is usually necessary to reduce the shrinkage of the sealant.

The aqueous dispersions in particular often contain more or less large amounts of wetting agents.

With the smoothing agents used hitherto, it was to be feared, particularly when the surfactants containing sulfonic acid groups were concerned, that filler portions, but also polymer particles, would be dispersed too extensively. This then leads to a washed out and no longer sharp edge and can also lead to considerable contamination of the surfaces abutting the sealing joint. This is a considerable disadvantage, particularly in the case of dark-colored porous substrates.

Examples

example 1

A 1% by weight solution in 90% isopropanol was prepared from a commercially available polyethylene oxide with a molecular weight of approximately 400,000. This solution had 18 mPa at 25 ° C according to Brookfield^.s.

Example 2

A 2% solution was prepared from the same polyethylene oxide as in Example 1 and had a viscosity of 57 mPa under the same Brookfield conditions^.s showed.

Example 3

A 1% by weight solution in 90% isopropanol was prepared from a polyethylene oxide with a molecular weight of approximately 600,000. This solution had 20 mPa at 25 ° C according to Brookfield^.s. A 2% by weight solution was prepared from the polyethylene oxide according to Example 3 in 90% isopropanol. This had a viscosity of 48 mPa at 25 ° C according to Brookfield^.s on.

The smoothing agents prepared according to Examples 1 to 4 were used in the joint sealants based on acrylic ester copolymers, silicones, polyurethanes, polysulfides and a solvent-containing system based on styrene-butadiene-styrene copolymer, which are explained in more detail below.

After the joints from a cartridge were filled with joint sealant in the usual way, the joint was smoothed with a smoothing spatula made of metal, the spatula being repeatedly wetted with the wetting agents according to Examples 1 to 4 by immersion.<tables id="tabl0001" num="0001"><img file="EP0248366A2_D0001.tif" /></tables>