EP0052237A2 - Paper for concrete with exposed aggregate and method for its manufacture - Google Patents

Abstract

This paper for concrete with exposed aggregate for manufacturing decorative concrete slabs with exposed aggregate comprises several layers, the topcoat containing a setting retarder for concrete and having a decorative cover made of a flexible, water-resistant and water-repellent coating film having a thickness of no more than 100 mu m for deactivating the retarder. <IMAGE>

Description

The invention relates to a washed concrete paper, consisting of several layers, the cover layer containing a concrete setting retarder, and the cover layer being partially ornament-like to deactivate the retarder in these areas.

Usual washed concrete papers consist of a multi-layer material with the following layer structure from bottom to top: plastic-paper-bitumen-paper retarder. The total thickness of the washed concrete paper is approximately 0.2 to 0.25 mm. The retarder contained in the retarder layer has the task of delaying the solidification of the facing concrete on the visible surface of the wash concrete slab until the slab has hardened, so that the concrete that is still soft on the visible surface can be washed out and the desired wash concrete surface is created.

Washed concrete slabs are manufactured in presses at a pressure of 250 to 750 tons. First, the washed concrete paper is placed in the press. After entering the facing concrete that contains the desired gravel grain, the facing is shaken in and then the filling of the back concrete. After compaction at the pressure mentioned, the plates are pushed out of the press and placed vertically next to one another, or stored horizontally one on top of the other, until the desired strength is achieved. After about 24 hours, the wash concrete paper is removed and the visible surface is washed.

There is now a need for ornamental concrete slabs that contain both sections made of exposed concrete and sections made of washed concrete in one area. For this purpose, from DE-OS 26 04 516 already washed concrete papers are known, in which the retarder layer at those places where the retarder effect is to be prevented is covered by cover plates, the thickness of which is a multiple of the thickness of the washed concrete paper and which protrudes all around at right angles Have restricted areas. These barrier areas of considerable thickness, i.e. 1 to 2 mm, should form an effective barrier for the concrete milk and prevent the concrete milk which has come into contact with the retarder from reaching the surface of the cover plates, as a result of which an exact boundary between the exposed concrete sections and the washed concrete sections would be lost.

However, these known washed concrete papers leave many wishes unfulfilled for use in practice. On the one hand, the cover plates mentioned generally have to be glued onto the retarder layer by hand. In addition, these washed concrete papers are unsuitable for the fully automatic production of the desired ornamental plates because the washed concrete papers are automatically inserted in the usual presses by mechanical suction. This is not possible with the known washed concrete papers due to the differences in thickness of the samples, so that these papers must necessarily be inserted into the machine by hand. Apart from the fact that the incompressible cardboard of 1 to 2 mm thickness, which is preferably used for covering, differs in level in the finished product In practice, ornamentation leads to another undesirable effect. In the area of the carton cover, the coarse facing grain is pressed into the carton despite the extensive incompressibility of the carton in relation to the total area. This later leads to protrusion from the surface of the exposed concrete sections, so that no completely flat exposed concrete sections are obtained. Overall, this has a disadvantageous effect on the contour definition between exposed concrete sections and washed concrete sections.

The object of the invention is therefore to provide an ornament-washed concrete paper which can be produced both by machine and used for the fully automatic ornament plate production. With this paper, the production of ornamental panels with sharp contours between exposed concrete sections and washed concrete sections should be possible, with special emphasis being placed on really flat exposed concrete sections.

This object is achieved according to the invention by a washed concrete paper of the type mentioned, which is characterized in that the oranment-like cover consists of a flexible, water-resistant and water-repellent lacquer layer with a thickness of at most 100 µm.

Surprisingly, it was found that a thickness of 1 to 2 mm of the cover is not necessary to achieve sharp-contoured ornaments, but that the lacquer layer of at most 100 μm used according to the invention leads to excellent results. The lacquer layers can be printed on the retarder layer using the screen printing method, in particular also by machine. The wash-concrete paper obtained is suitable for the mechanical production of ornament plates, and ornament plates with very good contour sharpness between exposed concrete sections and wash-concrete sections are obtained. In particular, really flat exposed concrete sections are obtained, which is not the case with the known ornament-washed concrete papers with a cardboard cover. According to the invention, there are decorative possibilities up to a very high degree of fineness.

With the help of the washed concrete paper of the invention, ornament plates can be produced semi-automatically and fully automatically without using special negative molds or inserts. The application can e.g. semi-automatically on vibrating tables and sliding presses, fully automatically on plate presses with steel matrices (e.g. Rinopresses and similar processes) or, depending on the grain size of the header, also on presses with the hardest possible rubber matrices.

A prefabricated concrete with an increased proportion of fine grain and stone powder is preferably used for the production of ornament plates using the ornament papers according to the invention.

The invention further relates to a process for the production of wash concrete paper with an ornament-like covering of the retarder layer, which is characterized in that, in the case of a conventional wash concrete paper, the retardation layer is partially covered in an ornament-like manner by printing in a screen printing process with a flexible, water-resistant and water-repellent lacquer with a dry layer thickness of at most 100 µm. This type of process makes it possible, in addition to large runs, to machine even the smallest quantities at low cost.

Hereinbelow, the term "lacquer" refers both to the lacquer solutions used for the screen printing process and to the lacquer film covering remaining after drying. However, all thicknesses refer exclusively to the dry film thicknesses.

This lacquer layer has a maximum thickness of 100 μm, preferably up to 50 μm, with film thicknesses of 7 to 12 μm leading in practice to particularly good results. Increasing the paint film thickness beyond 100 µm has no further advantage; on the contrary, one has to expect various disadvantages. On the one hand, higher paint film thicknesses naturally require a higher paint coat need. On the other hand, such lacquer film thicknesses are difficult to achieve without special measures with regard to the lacquer composition and the printing technique in the screen printing process, and finally, with larger lacquer film thicknesses, tension on the paper surface can also be expected, which in turn can endanger the flat position of the overall sheet.

The lower limit of the coating film thickness is not sharp and depends to a certain extent also on the properties of the coating used and the retarder type of the paper. A minimum thickness is therefore necessary in order to prevent diffusion of the retarder through the paint film under the influence of the concrete milk, since otherwise the contours between the exposed concrete sections and the washed concrete sections will be blurred.

According to the method of the invention, the desired lacquer covering pattern is preferably applied with a single screen printing process. With this procedure, the above-mentioned preferred range of the lacquer film thickness of 7 to 12 μm can be easily achieved.

According to the invention, a flexible, waterproof and water-repellent lacquer is used. It is preferably ensured here that the dried lacquer films are non-blocking, so that when using the ornament wash concrete papers printed according to the invention for the fully automatic production of ornament plates, faults are avoided with certainty.

The flexibility of the varnish is necessary so that the varnish film adheres well even when the printed wash concrete paper is bent or even kinked. In addition, even under the high pressures when compacting the washed concrete slabs, there should be no damage to the paint film, except for the retarding layer, ie the paint film should be covered by the grain of the facing concrete must withstand high deformations due to high pressures without significant damage in order to prevent the retarder from penetrating at these points.

The varnish used according to the invention must also be water-resistant for a long time, since the washed-out concrete slabs usually store for up to 24 hours after being pushed out of the press with the washed-in concrete paper attached to them. The lacquer film must not be attacked by the alkaline-aqueous environment of the concrete milk, in particular it must not happen that the retarder passes through the lacquer film, or that the washed concrete paper blisters at the areas masked with lacquer or even completely at these points the ornament plate.

Finally, the paint used must also be water-repellent in order to prevent concrete milk containing retarders from infiltrating the areas of the washed concrete paper masked with paint and thus again causing a blurring of contours. It is therefore preferable to ensure that the paint does not contain too many hydrophilic groups. Possible hydrophilic groups of solvents must also be taken into account here, since solvent residues generally remain stubbornly enclosed in the paint film.

The coating solutions used for the screen printing process must on the one hand have the highest possible solids content in order to achieve the desired coating film thicknesses; on the other hand, the viscosity of the coating solutions must meet the requirements of the screen printing technology used. In many cases compromises have to be made.

On the basis of the above information, the person skilled in the art is able to put together appropriate lacquers. The binder base of the varnish does not play a special role in itself, provided the required properties with regard to elasticity, water resistance, water repellency and non-blocking are given. Varnishes based on Polyacrylic acid esters and polymethacrylic acid esters have been tried and tested. Examples include the methyl, ethyl, propyl and butyl esters. If these acrylic resins are too hard or too soft when used alone as binders, the desired elasticity and non-blocking can be adjusted by adding other binders or by mixing them together. Polymethacrylic acid butyl esters which are commercially available either in dissolved form or as solid resins are preferred, optionally in combination with smaller amounts of a binder which improves the antiblocking properties.

The solvent system, too, is not subject to any particular restriction, with sufficient dissolving power for the paint components being taken for granted. For the acrylic resins mentioned, aromatic solvents such as toluene are used; Ketones; or esters, such as butyl acetate or butyl glycol acetate. The solvent system preferably takes care that the solvent power for the retardant used, e.g. Sugar, is as low as possible.

In general, sieves with a fabric thickness of 100 to 400 μm, preferably about 200 to 250 μm and lacquers with a solids content of 30 to 60% are used.

The method of the invention is suitable for printing conventional wash concrete papers. Suitable are e.g. Papers with the following layer structure from bottom to top: plastic-paper-bitumen-paper retarder or plastic-paper retarder. These washed concrete papers have thicknesses of approximately 0.1 to 0.25 mm.

When using such conventional washed concrete papers, which are printed according to the invention with the lacquer mask of low layer thickness, the greatest possible surface smoothness of the exposed concrete sections can be achieved, since this largely depends on the possible impression depth of the facing concrete grain. In the case of the washed concrete papers with card clay coverage, the depth of impression in the manufacture of the ornament plates is substantially greater than when using the papers according to the invention, printed with a thin layer of lacquer.

In a further preferred embodiment, a washed concrete paper with a retarder layer is used, which has a slow water solubility due to a special addition to the retarder formulation. For example, by adding about 10 to 12% by weight of polyvinyl alcohol to the retarder mass, calculated on dry substances, to delay the retarder release by about 5 to 10 seconds. As a result, when the retarder layer comes into contact with the concrete water, the retarder slows down into the aqueous phase, so that good contour definition is ensured even when less careful operation or use of older machines is used in the manufacture of decorative washed concrete slabs. Instead of polyvinyl alcohol, it is also possible to use other water-soluble binders which delay the release of the retarder into the aqueous phase.

• Fig. 1 einen Querschnitt durch ein Waschbeton-Ornamentpapier der Erfindung,
• Fig. 2 einen Querschnitt durch ein weiteres Waschbeton-Ornamentpapier der Erfindung, und
• Fig. 3 eine perspektivische Ansicht der Waschbeton-Ornamentpapiere nach den Fig. 1 und 2.

The invention is explained below with reference to the drawings. Show it:

• 1 shows a cross section through a wash concrete ornamental paper of the invention,
• 2 shows a cross section through a further wash concrete ornament paper of the invention, and
• 3 is a perspective view of the wash concrete ornamental papers according to FIGS. 1 and 2.

• Kunststoffschicht 4-Papierschicht 5-Bitumenschicht 6-Papierschicht 7-Verzögererschicht 2-Lackmaske 3. Die Lackmaske 3 hat eine Schichtdicke von etwa 10µm. Die Gesamtdicke des Waschbeton-Ornamentpapiers 1 beträgt 0,20 mm..

1 has the following layer structure from bottom to top:

• Plastic layer 4-paper layer 5-bitumen layer 6-paper layer 7-retarder layer 2-paint mask 3. The paint mask 3 has a layer thickness of approximately 10 μm. The total thickness of the wash concrete ornament paper 1 is 0.20 mm.

• Kunststoffschicht 14-Papierschicht 15-Verzögererschicht 12-Lackmaske 13.

The wash concrete ornamental paper 11 of Fig. 2 has the following Layer structure from bottom to top:

• Plastic layer 14-paper layer 15-retarder layer 12-paint mask 13.

_V erzögererschicht 12 and resist mask 13 correspond to the layers 2 and 3 in Fig. 1. The total thickness of the aggregate concrete ornament paper in Fig. 2 is 0.12 mm.

FIG. 3 shows a perspective illustration of the wash concrete ornament papers from FIGS. 1 and 2.

1 and 2, the resist mask 3, 13 is in each case on a commercially available washed concrete paper. The lacquer mask 3, 13 with a thickness of approximately 10 μm was produced in one operation using the screen printing method using a lacquer according to the following example.

Both washed concrete ornament papers deliver washed concrete ornament plates with excellent contour definition and a particularly flat exposed concrete surface where the paint mask 3, 13 is located. Of course, other ornaments are also possible, especially with a complicated pattern. The example explains the invention.

A paint is used which, based on 1000 parts by weight, 267 parts by weight of butyl polymethacrylic acid, 67 parts of ethylhydroxyethylcellulose, small amounts of dye and other auxiliaries, remainder mixed solvents made from aromatic hydrocarbons (toluene, xylene and others) and esters (butyl acetate, butylglycol acetate).

With this varnish, two different commercially available, washed concrete papers, as can be seen from FIGS. 1 to 3, are screen-printed in a mask-like manner with a varnish film thickness of about 10 μm.

The wash concrete ornament papers obtained are then connected send used for the production of wash concrete ornamental panels. Here you get sharp-contoured ornament panels with particularly flat exposed concrete sections.

Claims (8)

1. Washed concrete paper for the production of ornamental washed concrete slabs, consisting of several layers, the cover layer containing a concrete setting retarder and the cover layer being partially ornament-like to deactivate the retarder in these areas, characterized in that the ornament-like cover (3, 13) consists of a flexible, waterproof and water-repellent lacquer layer with a maximum thickness of 100 µm. 2. Washed concrete paper according to claim 1, characterized in that the thickness of the lacquer layer (3, 13) is 7 to 12 µm. 3. Washed concrete paper according to at least one of claims 1 and 2, characterized in that the layer containing the concrete setting retarder (2, 12) contains an additive which slows down the water solubility of the retarder. 4. Washed concrete paper according to one of claims 1 to 3, marked characterized by the following layer structure: plastic (4) -paper (5) -bitumen (6) -paper (7) -delayer (2) -Ornaments- top layer (3), and a total thickness of 0.2 to 0.25 mm. 5. Wash concrete paper according to one of claims 1 to 3, characterized: by the following layer structure: plastic (14) paper (15) -Verzö ^g erer (12) -Ornamentdeckschicht (13), and a total thickness of 0,1 to 0,15 mm. 6. washed concrete paper according to at least one of claims 1 to 5, characterized in that the lacquer layer (3, 13) is based on polyacrylic acid esters and polymethacrylic acid esters. 7. Washed concrete paper according to claim 6, characterized in that the lacquer layer (3, 13) is based on polymethacrylic acid butyl ester. 8. A process for the production of washed concrete paper with an ornament-like covering of the retarder layer, in particular according to one of claims 1 to 6, characterized in that, in a conventional washed concrete paper, the retardant layer is printed by screen printing with a flexible, water-resistant and water-repellent, lacquer with a dry layer thickness of at most 100µm partially covered like an ornament.

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