DD300825A5 - Process for impregnating cement products - Google Patents

Abstract

A process is proposed for the impregnation of cement products, preferably pressed after forming, especially under the action of heat, in particular fibre-reinforced cement products, before the setting thereof, in which a preferably aqueous plastics dispersion and, subsequently thereto, a preferably aqueous wax dispersion, especially a paraffin dispersion, is applied to the products wet from the mould. Advantageously, the wax dispersion is here applied within about 2 minutes after the application of the plastics dispersion; advantageously, above all the plastics dispersion, and preferably both the plastics dispersion and the wax dispersion, are rolled on.

Description

Preference has been given in practice to plastics from the group comprising acrylic resins, polyurethane resins and epoxy resins. It is advantageous applied as much Kur.ststoffdispersion that 5 to 60 g of plastic per m ² surface present. To do this

especially plastic dispersions having a plastic content up to about 60Ma .-% used.

It can pigment-containing plastic dispersions are used, in particular up to about 5 wt .-% pigments, for. Eg FeO,

based on the plastic content included.

Wax dispersions used are, in particular, those whose wax content has a softening point in the range of

to 100 ° C, in particular of at least 80 ° C, having. In particular, paraffin dispersions are used, but other waxes are also usable.

Wax dispersions are preferably used whose wax content is at least substantially unsaponifiable. In particular, the wax dispersions in an amount of 10 to 60 f "preferably 12 to 40 g, in particular 15 to 35 g, Wax applied per m ² surface, which advantageously wax dispersions are used, which contains a wax

from 25 to G5Ma .-%, preferably 30 to 55Ma .-%, in particular 35 bib 50Ma .-% exhibit.

Preference is furthermore given to using nonionic wax dispersions. In particular, wax dispersions are used, the viscosity at 25 ⁰ C between 40 and 10OcP, preferably to

or at 5OcP.

Advantageously, wax dispersions whose density or the density of its wax component at 15 ⁰ C of between 0.8 and 0.95 g / cm ^3,

especially at about 0.88 g / cm ³ .

The pH of the wax dispersions used is not particularly critical, but is preferably from 5 to 8. The wax dispersions can also be pigmented, v / obei in particular a pigment content of up to 5Ma .-%, based

on the wax content, may be present.

Preferably, however, only the Kunstctoffdispersion is pigmented, the colors by the uncolored wax layer

especially good. ,

The invention will be described below with reference to an embodiment. From a fiber cement suspension, the solid ingredients are removed via a screen cylinder as a nonwoven and by means of a Transfer screen to a rotating format roller. After reaching the desired layer thickness, the fleece is along

cut a Walzenerzeugenden and driven the resulting rectangular nonwoven plate in a punching device, where from the plate, the individual roof panels are punched out. The adjacent roof panel blanks are transferred by means of a nipple on a press plate and moved into the first coating station, where they with a

Plastic dispersion to be rolled. They are nschließend A in a second coating station directly to the

first coating station is connected / rolled with a wax dispersion. The individual press plates are then stacked one above the other so that the top of the roof panels carrying a wax coating abuts the underside of the overlying press plate. The plate stack is fed into and pressed into a press, where the hydraulic setting progresses to the point where the roof panels are dimensionally stable. Thereafter, the plate stack is singulated with the wax coating of the roof plates allowing a clean separation. The roof panels are from the

Press plates removed (worn) and go to storage; the press plates are cleaned, if necessary

preheated and go to re-occupancy with Dachplattenrohrlingen back.

The pressing is preferably carried out at a temperature between 40 and 9O ⁰ C. Preferably, the loaded press plates are simply under a respective raisable and lowerable coating roller

drove through; the metering of the plastic or wax dispersion on the respective coating roller can in the usual

Manner, e.g. via a slotted nozzle or via an auxiliary roller, which dips into such a dispersion and at the Coating roller is applied. The coating rolls 9n may have a rigid or compliant surface, e.g. one Have rubber coat. Optionally, a spray application can take place; but this is not preferred, as this pollution of the Preßblechränder goes along. It has been found that not only achieves an excellent duration impregnation with the inventive method

is the efflorescence prevented, but 63 was found that no sticking when separating the

Plattensta). It occurs even when very little wax is applied, as the wax is virtually completely absorbed by the before Plastic sealed surface remains. The process according to the invention can advantageously be used generally with freshly formed "green" cement products;

In particular, it is suitable for the production of roof panels and facade panels, which also in a known manner with a

Litter layer can be provided. The invention thus also relates to cement products, in particular fiber cement products, with a Oborflächenimprägnierung of wax, which are mainly characterized in that below the Surface impregnation is applied a plastic impregnation.

Claims (24)

1. A method for impregnating, preferably after molding, in particular under heat, pressed, cement products, in particular fiber cement products, prior to their setting, characterized in that a preferably aqueous wax dispersion, in particular a paraffin dispersion, is applied to the mold-wet products. 2. The method according to claim 1, characterized in that the wax dispersion is applied within about 2 minutes after the application of the Kunststoffdisporsion. 3. The method according to any one of claims 1 or 2, characterized in that the plastic dispersion is rolled. 4. The method according to any one of claims 1 to 3, characterized in that the wax dispersion is rolled. 5. The method according to any one of claims 1 to 4, characterized in that a dispersion of a film-forming plastic is applied. 6. The method according to any one of claims 1 to 5, dad <rch gekonnzeichnet that a dispersion of at least one thermoplastic material is applied. 7. The method according to claim 6, characterized in that a dispersion of at least one plastic is applied with low-temperature plasticity. 8. The method according to any one of claims 1 to 7, characterized in that a dispersion of at least one plastic selected from the group consisting of acrylic resins, polyurethane resins and epoxy resins is applied. 9. The method according to any one of claims 1 to 8, characterized in that the plastic dispersion is applied in an amount of 20 to 60 g of plastic per m ² surface. 10. The method according to any one of claims 1 to 8, characterized in that a plastic dispersion having a Kunstsioffgehalt of up to about 60 wt .-% is applied. 11. The method according to any one of claims 1 to 10, characterized in that a pigment-containing plastic dispersion is applied. 12. The method according to claim 11, characterized in that a plastic dispersion having a pigment content of up to 5Ma .-%, based on the plastic content, is applied. 13. The method according to any one of claims 1 to 12, characterized in that oine wax dispersion whose wax content has a softening point in the range of 65 to 100 ⁰ C, in particular of at least 80 ⁰ C, is applied. 14. The method according to any one of claims 1 to 13, characterized in that a wax dispersion whose wax content is at least substantially unsaponifiable applied wjrd. 15. The method according to any one of claims 1 to 14, characterized in that the wax dispersion in an amount of 10 to 60 g, preferably 12 to 40 g, in particular 15 to 35 g, wax per m ² surface is applied. 16. The method according to any one of claims 1 to 15, characterized in that a wax dispersion having a wax content of 25 to 65% by mass, preferably 30 to 55% by mass, in particular 35 to 50% by mass, is applied. 17. The method according to any one of claims 1 to 16, characterized in that a nonionic wax dispersion is applied. 18. The method according to any one of claims 1 to 17, characterized in that a wax dispersion whose viscosity at 25 ° C between 40 and 10OcP, preferably at or at 5OcP, is applied. 19. The method according to any one of claims 1 to 18, characterized in that a wax dispersion, the density or the density of the wax fraction at 15 ° C between 0.8 and 0.95 g / cm ³ , in particular at about 0.88 g / cm ³ , lies, is applied. 20. The method according to any one of claims 1 to 19, characterized in that a wax dispersion having a pH between 5 and 8 is applied. 21. The method according to any one of claims 1 to 20, characterized in that a pigment-containing wax dispersion is applied. 22. The method according to claim 21, characterized in that a wax dispersion having a pigment content of up to 5 wt .-%, based on the wax content, is applied. 23. Cement product, in particular fiber cement product with a surface impregnation of wax; characterized in that below the surface impregnation, a plastic impregnation is applied. 24. Cement product according to claim 23, prepared by the method according to one of claims 1 to 22. The invention relates to a method for impregnating, preferably after molding, in particular under Heat, pressed, cement products, especially fiber cement products, before their setting, and after products made by this process. For hydraulically bound products, which are referred to herein as cement products, especially in Fiber cement products, efflorescence occurs under certain conditions. Efflorescence is essentially Excretions of salts on brick and natural stone masonry, on concrete, mortar, stone wood or moldings Fastirzement. They are due to the migration of contained in the building material, water-soluble salts on the surface and caused the subsequent evaporation of the transport water. Most often, a chemical reaction occurs, causing the efflorescence to become insoluble in water. Their chemical composition depends on the type of building material. For bricks, precipitation of gypsum may occur, formed from sodium sulfate from bricks and lime from grout. In the case of weather-exposed building materials that hydrated completely or partially from hydrated Alkaline earth silicates exist, soluble calcium hydroxide can reach the surface with water, where it through the Carbon dioxide of the air to very sparingly soluble, white calcium carbonate is transformed. In the vast majority of cases, it is not the quality, but the aspect of the building materials, which is considerably impaired. Especially with colored building materials, the occurrence of efflorescence is extremely disturbing! Cover the color of the building material and form white flakes. The low solubility of the efflorescence in water and their good adhesion to the substrate can change the appearance of buildings for a long time very adversely. To prevent the occurrence of efflorescence on fiber cement products with a thickness of about 0.1-1.5mm Cement-bound paint layer on the surface (visible surface), some methods are already known. To avoid such Efflorescence was e.g. for the thin paint layer instead of Portland cement, which is the undyed binder Base plate is used, aluminate cement. This could improve the appearance of efflorescence be achieved. Another way to prevent efflorescence is to apply a topcoat of colored Portland cement Apply Fasorzementplatten. In this case, however, an additional coat of the surface is necessary to to achieve efflorescence-free products. However, this additional coat can not be applied during the production process, but rather when the cement V of the top layer has reached a certain strength, whereby a subsequent, costly, additional processing is required. The applicant has already proposed to use cement products, in particular fiber cement products, prior to their use Setting and, in particular, applying a paraffin dispersion prior to pressing to seal the surface thereof. It has been found that even with this paraffin seal a complete suppression of efflorescence difficult, especially because it is necessary to coordinate different production parameters z. B. the setting temperature to keep constant and / or the composition of the litter layer, if any, and the Wax concentration or type to vary. There have been cases where fiber cement boards thus treated so far paraffin due to the heat of the cement have sucked in that the formation of a p'igestrebton continuous surface layer on the plates is omitted and, albeit minor, efflorescence occurred. On the other hand, however, the application of large amounts of paraffin entails that a part of the wax in the course of Production is lost by draining and thus on the one hand, the wastewater is charged ur.d on the other hand, the press plates heavily soiled, which then need to be specially cleaned. This is particularly noticeable if that Wax is sprayed on. It was therefore an object to fundamentally improve the already proposed wax impregnation process, so that the previously necessary careful optimization of the treatment parameters no longer has the previous meaning and mentioned Difficulties no longer occur. This is inventively by a pre-impregnation (priming) of the products with plastics before AufbiIngen of Achieved wax. Accordingly, the inventive method for impregnating, preferably after molding, in particular under Heat, pressed, cement products, in particular Faserzementprodiikten before their setting especially by it in that a preferably aqueous plastic dispersion is applied to the mold-wet products, followed by a preferably aqueous wax dispersion, in particular a paraffin dispersion. Surprisingly, it has been found that it is possible to apply the wax dispersion immediately after application apply the plastic dispersion without mixing the orders occurs, so that the surface layer still consists only of wax. This may be due to the equally surprising fact that plastic dispersions in the much faster Upper layer of cement products penetrate as wax dispersions. In practice, good results are obtained when the wax dispersion within about 2 minutes after application of the Plastic dispersion is applied. It is favorable to roll on at least the plastic dispersion; Both plastic dispersion and are preferred Wax dispersion applied over rollers. As plastics, especially film-forming plastics, in particular thermoplastic materials used, which preferably have low-temperature plasticity.