EP0657258A1 - Process for making building elements, in particular from fibre reinforced mineral materials - Google Patents

Abstract

A process for making mineral-bonded building elements, in particular with a content of chopped fibres and, if appropriate, continuous reinforcement, and also various installations for carrying out such a process are described. The aim of the invention is to develop a process which combines the advantages of the extrusion process with that of the casting and injection process. The building material is introduced under pressure into a supporting mould, so that it is exposed to the same pressure conditions at every point of the building element. In order to ensure uniform pressure conditions in the extrusion process, extruding is carried out into a supporting mould (6a,6b) by means of a special extrusion head tapering towards the die. With the pump (12), the pasty fibre composite is fed via a pressure tube (5) into the extrusion head (13). The course of the flow of the fibre composite is drastically altered on entering into the extrusion head (13) with a deflection of about 90 DEG . This eliminates the influence of the flow behaviour through the feed tube in the head (13). <IMAGE>

Description

The present invention relates to a method for the production of components, in particular rod-shaped or plate-shaped components with and without a profiled cross section made of fiber-reinforced mineral-bound building materials, and to systems for carrying out such a method. In particular, the present invention relates to a method for producing components with improved mechanical properties.

• beschränkten Anforderungen an die mechanischen Eigenschaften (Biegezugfestigkeit, Bruchdehnung)
• Ansprüchen an die Oberflächengestaltung (z.B. Struktur der Giessform).

Components made of fiber-reinforced cementitious building materials, such as fiber concrete, fiber cement, are manufactured using various processes. The casting process, in which the pre-cut fibers are mixed into the cement matrix in the mixer, is often used for flat and rod-shaped components. The castable fiber composite material (matrix + fibers) is filled into molds and compacted by vibration. This process works well for the manufacture of small parts with

• limited requirements for the mechanical properties (bending tensile strength, elongation at break)
• Demands on the surface design (eg structure of the mold).

Higher requirements with regard to mechanical properties can be met in particular if the water / cement value is reduced for a given short fiber content or if additionally oriented fiber bundles are introduced as reinforcement.

• Verlangsamung der Festigkeitsentwicklung
• tiefere Druck-, Zug- und Biegezugfestigkeit
• reduzierte Frostbeständigkeit
• grösseres Schwindmass und grössere feuchtigkeitsbedingte Formänderungen.

An increase in the short fiber content leads to considerable difficulties in processing and in particular also results in an increase in the water / cement value. However, this increase in the water / cement value adversely affects various relationships the mechanical properties of the fiber composite material, such as

• Slowdown in strength development
• lower compressive, tensile and flexural tensile strength
• reduced frost resistance
• greater shrinkage and greater moisture-related changes in shape.

The mechanical properties can only be improved by increasing the fiber content if the water / cement value does not have to be increased at the same time. This is achieved when the matrix and fibers are not premixed, but are separately introduced into the mold by spraying, which, however, involves a correspondingly high outlay and is therefore generally uneconomical for series production.

In both processes (pouring and spraying processes) the water content varies across the cross section due to the compression, which leads to different shrinkage across the cross section.

A method is known from EP 0 173 873 in which the hydraulically setting mass is applied to a base in a predetermined thickness, whereupon fiber chips are sprinkled onto the surface and pressed into the matrix. In addition, continuous fibers can also be placed and / or drawn into the mass of the panel to be produced.

The disadvantage of this method is the sequence of many individual steps and the limited design options with regard to shape and surface.

Attempts have also already been made to extrude certain fiber composite materials.

With this process, rod-shaped components with a constant cross-section can be produced extremely efficiently. Due to the low water / cement value of the stiff plastic processable fiber composite material there are favorable properties with regard to strength, shrinkage and swelling. Disadvantages are the extremely brittle fracture behavior and the inadequate surface properties for many applications.

• rationelle Fertigung von standardisierten profilierten und nicht profilierten Bauteilen mit stabförmiger oder flächiger Ausbildung
• gute mechanische Eigenschaften dank tiefem Wasser/Zement-Wert
• kurze Härtungszeiten
• hervorragende Oberflächengüte, entsprechend den verwendeten Formen
• gezielt in den Zonen der grössten Zugbeanspruchung angeordnete Zusatzbewehrung.

The aim of the present invention was therefore to develop a process which combines the advantages of the classic extrusion process with those of the casting and injection process, and to provide plants for carrying out this process. The advantages of the method according to the invention are:

• rational production of standardized profiled and non-profiled components with rod-shaped or flat training
• good mechanical properties thanks to deep water / cement value
• short curing times
• excellent surface quality, according to the shapes used
• Additional reinforcement arranged specifically in the zones of the greatest tensile stress.

This goal was achieved by providing a process for the production of components, in particular from fiber-reinforced cementitious building materials, which is characterized in that the building material is introduced into a support mold under pressure, so that it is exposed to the same pressure conditions at every point of the component.

Due to the constant pressure conditions, inhomogeneities within a component are largely avoided, which contributes to an increase in strength and improves dimensional stability. In addition, more rigid plastic materials can be processed under pressure, which means that materials with a high short fiber content can be processed when the water / cement value is low.

The method is preferably carried out in such a way that the flow of the material freshly introduced into the mold is largely laminar.

Due to the constant pressure conditions and the preferably largely laminar flow, reinforcements made of continuous fibers, respectively. Install rovings, cords and fabric to further improve the strength and breaking behavior in the component without creating inhomogeneities.

This method is particularly suitable for all filled e.g. fiber-reinforced cementitious building materials. Known filling materials, in particular fiber bundles or. Short fibers obtained from fiber bundles can be used. Natural and artificial fibers, for example mineral, metallic or organic fibers as well as carbon fibers as individual fibers or bundled both as short and as continuous fibers, can be considered as fiber reinforcement. Examples of such fiber materials are AR glass fibers, plastic fibers, carbon fibers and steel wires. These can be used both alone and in combinations of materials. Possible pre-treatments of the reinforcement materials are known.

The cementitious building materials can contain commonly used additives, for example concrete plasticizers, high-performance concrete plasticizers and polymer dispersions.

Preferred building materials usually contain polymer dispersions in such amounts that the solids content is 0-10% by volume with respect to the entire matrix.

The short fiber content is only limited by the processability. However, corresponding mixtures preferably contain 0.3 to 3% by volume of short fibers, preferably 1.5 to 2.5% by volume, and have a water / cement value in the range from 0.2 to 0.5, in particular 0 , 2 to 0.3.

• Figur 1 stellt eine Vorrichtung für die Injektion über einen Kolben dar, wobei Figur 1a ein Längsschnitt und Figur 1b ein Querschnitt ist;
• Figur 2 zeigt eine Vorrichtung zur Herstellung eines Bauteils ohne Endlosfasern mittels Extrusion, wobei Figur 2a einen Längsschnitt und Figur 2b einen Querschnitt durch dieselbe Vorrichtung zeigt;
• Figur 3 zeigt einen Anlagenteil zur Herstellung eines Bauteils unter Verwendung eines Mehrfach-Extrusionskopfes, beispielsweise für die Herstellung von Produkten mit Endlosfasern als zusätzliche Bewehrung (Duplex-Extrusion), wobei Figur 3a einen Längsschnitt und Figur 3b einen Querschnitt durch denselben Anlagenteil zeigt, und
• Figur 4 zeigt eine Vergrösserung des Austrittsbereichs von Figur 3.

Special embodiments and systems for carrying out the method are explained in more detail with reference to the figures.

• FIG. 1 shows a device for injection via a piston, FIG. 1a being a longitudinal section and FIG. 1b being a cross section;
• FIG. 2 shows a device for producing a component without continuous fibers by means of extrusion, FIG. 2a showing a longitudinal section and FIG. 2b a cross section through the same device;
• FIG. 3 shows a system part for the production of a component using a multiple extrusion head, for example for the production of products with continuous fibers as additional reinforcement (duplex extrusion), FIG. 3a showing a longitudinal section and FIG. 3b a cross section through the same system part, and
• FIG. 4 shows an enlargement of the exit area from FIG. 3.

In the case of injection via pistons (see FIG. 1), the filled material is introduced into a space 6 from a pressure vessel 1, which is provided with an agitator 2, a pressure relief valve 3 and a riser pipe 4, via a pressure hose 5 and the piston rod tube 9, which is limited by the injection mold 6a, 6b and the piston surface 8. Due to the inflow of the material, the piston 8, 9 is displaced within the mold 6a, 6b in the opposite direction to the material flow. In order to prevent a pressure drop in the space 6, the piston surface 8 is sealed off from the injection mold 6a with a seal 10. Of course, the piston 8, 9 can also be moved actively.

The device shown in Figure 1 is also very well suited for the production of components with additional endless, directed reinforcement, for example with spun threads, yarn, wires or rovings (fiber strands). The piston with the reinforcement 11 moved into the starting position against the forehead of form 6b. The guide bores 8a in the piston surface 8 hold the individual reinforcement threads in position.

The reinforcement 11 is anchored in the forehead of shape 6b. The designated partitions 7 of the forehead, respectively. another fastening device, clamp or. hold the individual threads or the wires and position them. After anchoring, the reinforcement is slightly tensioned.

Compressed air usually with 2 to 3 bar acts on the fiber composite material filled in a pressure vessel 1. The pressure acting on the material surface conveys the composite material via a riser pipe 4 into the pressure hose 5. From there, the material reaches the piston rod pipe 9 and on to the mouth in the piston chamber 6.

The pressing of the fiber composite material into the piston chamber 6 pushes the injection piston 8.9 back. The piston counterforce regulates the pressure in the system. The fiber composite material flows around the reinforcement 11 as soon as it leaves the piston surface (guide). This ensures that the reinforcement 11 is positioned with millimeter accuracy.

If the piston moves during the injection process, it carries the reinforcement, which, for example, has previously been unwound from coils (not shown) and has been fixed in the end face 6b.

In addition, a slight vibration can be provided directly on the piston in order to additionally compress the fiber composite material.

The injection into a closed mold achieves a high-quality surface of the component that is smooth on all sides and good dimensional stability.

Injection via pistons results in the same flow behavior over the entire injection process, homogeneous material build-up and thus even shrinkage over the entire component.

The compression in the mold under pressure and possibly slight vibration leads to a compact structure and little air entrapment.

The injection method using pistons also enables precise positioning of the reinforcement by guiding it in the piston surface and precise arrangement of the reinforcement at every point in the profile cross-section.

• der Unterhalt geringer, und
• die Injektionswerkzeuge sowie
• die Anlage kostengünstiger.

The system is simple and has very few wearing parts, since there are few moving parts, especially if the piston feed is generated by the injection material. This will

• maintenance less, and
• the injection tools as well
• the plant cheaper.

Due to the significantly lower water requirements of the mixture compared to the pouring process (lower water / cement value), the shrinkage and swelling dimensions are also smaller.

A process similar to piston injection is the extrusion process. Simple extrusion is suitable for components that are not additionally reinforced with continuous fibers. A suitable system is shown in Figure 2.

In order to ensure the uniform pressure conditions in the extrusion process, extrusion is carried out in a support mold 6a, 6b by means of a special extrusion head which tapers towards the mouth.

The special design of the extrusion head enables pressure to be built up, which leads to the favorable discharge conditions of a preform with simultaneous additional compression. Immediately after discharge, the support mold is compressed again, which improves the shape accuracy and enables the surface finish.

With a pump 12, the pasty fiber composite material is conveyed into the extrusion head 13 via a pressure hose 5. The flow path of the fiber composite material becomes when entering the extrusion head 13 with a deflection of about 90 ° usually broken. This eliminates the influence on the flow behavior by the delivery hose 5 in the head 13. The material is compressed in the extrusion head 13, which tapers towards the mouth, and is given the preform, which is similar to the final shape of the component, by the corresponding design of the head at the mouth. Due to the compression in the extrusion head 13 and the narrowing shape of the head extension above and to the side at the mouth of the extrusion head 13, a largely laminar flow is achieved at the mouth. The fiber composite material is discharged and pressed into the support mold 6a, 6b by the narrowing shape of the head extension. The special design of the mouth, in particular also its weak inclination with respect to the bottom of the support mold 6a, 6b, allows the air to escape and thus prevents it from being trapped. With a drag form 14, which has the contour of the back of the component and in front of the extrusion head. is arranged somewhat overlapping, the existing pressure in the discharge zone is slowly reduced. A small vibrator 15 on the drag mold 14 supports the entire discharge process and, in conjunction with other processes, brings about a high surface quality of the component.

A method using two extruders (duplex extrusion) is shown in FIG. With two pumps 12, pasty fiber composite materials are each conveyed via a pressure hose 5 into the extrusion head 13a or into the extrusion head 13b. The delivery rate can be set separately for each pump 12, which influences the delivery rate and delivery pressure. As with the method with only one extruder, the flow path of the materials is severely broken upon entry into the extrusion heads 13a, 13b with a deflection of preferably approximately 90 °. The material is compressed in both extrusion heads and is given the appropriate preforms by the appropriate design of the heads at the mouth, which together are similar to the final shape of the component. The compression stage is designed differently depending on the component, so that laminar flow conditions of the same speed arise at the mouth even with uneven profile cross sections. The fiber composite material of the first extrusion head 13a is discharged and pressed into the support mold 6a, 6b by the narrowing shape of the head extension. The special design of the mouth, in particular the head extension at the top and the inclination of the extrusion heads 13a, 13b relative to the bottom of the support mold, allow the air to escape and thus prevent it from being trapped. In the advanced part of the extrusion head 13a on the drag mold side, a reinforcement guide 8a can be provided, through which a continuous, oriented reinforcement material can be fed from an unwinding device via a tensioning device (not shown). For the production of components that are provided with an endless, directed reinforcement, the reinforcement material is guided over the reinforcement guide 8a to the clamping device for the reinforcement 7 and is slightly tensioned. During production, the reinforcement material is fed in under constant light tension, for example unwound from spools. The guide between the mouths of the two extrusion heads 13a, 13b positions the reinforcement on the first extrusion layer with millimeter precision. The fiber composite material of the extrusion head 13b is discharged. The elongated upper part of the head 13b presses the second extrusion layer against the first and embeds the additional reinforcement, fabric, cord, spun threads, yarn, rovings, wire, etc. in between. As with simple extrusion, with a drag mold that has the contour of the back of the component, the existing pressure in the discharge zone is slowly reduced. Here, too, a small vibrator 15 on the drag mold 14 supports the entire discharge process and works together with other processes a high surface quality of the component.

The exact design of a possible system for duplex extrusion in the area of material discharge from the extrusion heads 13a, 13b into the support mold 6a, 6b is shown in FIG. It is important for the desired properties to be achieved that the shaping takes place under pressure. This can be accomplished by having the extrusion head 13a, 13b up, i.e. is extended on the drag side. The exact training depends on the material as well as the component.

Using this duplex extrusion process, endlessly longitudinal and / or transverse reinforced components can be manufactured with good homogeneity. In particular, fabric and cord allow any choice of reinforcement orientation and thus the determination of the properties depending on the component.

Of course, the method can also be carried out with more than two extrusion heads, whereby an endless, oriented reinforcement does not necessarily have to be provided for each layer. it can also be used for the production of composite materials with or without oriented reinforcement, especially for those with at least one layer of a pasty, fibrous, cementitious building material. With at least two extruders, for example, composite cross-sections from different construction or Materials are manufactured. For example, a core layer with a lower bulk density can be introduced between two cementitious layers.

The special extrusion process of the present invention, in particular the duplex extrusion, is characterized by the following special features: The extrusion takes place in a support mold 6a, 6b, whereby precise dimensions of the contour and a smooth, non-porous surface in the region of the support mold are achieved.

Thanks to the possibility of processing fiber composite materials with the lowest possible water content, good strength values, small shrinkage, good dimensional stability in the fresh state, homogeneous material structure over the entire profile cross section and uniform shrinkage over the entire cross section are achieved.

The deformation and compression in the extrusion heads result in a compact structure and ensure good shape even with relatively dry material.

As a result of the second pressure build-up in the support mold 6a, 6b, the surface in particular also becomes denser.

Due to the special design of the extrusion heads 13a, 13b in the region of the mouth and the inclination of the heads, the air can escape well, as a result of which air inclusion can be largely avoided.

The duplex resp. Multiplex extrusion enables the reinforcement to be precisely positioned by guide 8a at the mouth between the at least two extrusion heads 13a, 13b. The reinforcement level is freely selectable and can therefore be precisely matched to the component and its stress.

The drag mold 14 causes slow pressure reduction in the molded component. With slight vibration at the same time, a pore-free surface of the component on the mold side and a dimensionally stable contour on the rear of the component are achieved.

The extrusion systems according to the invention have few wearing parts and only require relatively simple extrusion tools. Therefore, you only need a small amount of maintenance and relatively inexpensive extrusion tools.

The extrusion heads 13a, 13b, etc. are preferably separable from one another, so that the “threading” of the reinforcement for the first time is simplified.

Special embodiments of the invention presented here are described in more detail in the dependent claims.

Claims (18)

Method for producing components, in particular from fiber-reinforced cementitious building materials, characterized in that at least one material is introduced under pressure into a support mold (6a, 6b), so that the at least one material is exposed to the same pressure conditions at every point of the component. A method according to claim 1, characterized in that the at least one material is introduced into the support mold (6a, 6b) under largely laminar conditions. A method according to claim 1 or 2, characterized in that the insertion opening is moved relative to the support form. Method according to one of claims 1 to 3, characterized in that the material is preformed before the introduction opening and after the introduction opening is carried out in the support mold. Method according to one of claims 1 to 4, characterized in that the at least one material is exposed to vibration at least when it enters the support mold (6a, 6b). Method according to one of claims 1 to 5, characterized in that the at least one material contains short fibers and is cementitious. Method according to one of claims 1 to 6, characterized in that at least two materials with different properties are introduced. Method according to one of claims 1 to 7, characterized in that at least one continuous reinforcement element (11) is introduced in at least one dimension and on at least one level. Method according to one of claims 1 to 8, characterized in that the at least one reinforcement element (11) by a reinforcement guide (8a) is guided, which is located in a part that is movable relative to the support mold (6a, 6b), is fastened to the mold face (6b) by means of a fastening device (7) and is then slightly tensioned and that the slightly tensioned reinforcement element (11) is underneath during the material feed constant voltage. System for carrying out the method according to one of claims 1 to 9, consisting of an agitator (2), a material feed (5) and a support mold (6a, 6b), characterized in that the agitator (2) is located in a pressure vessel (1 ) with a riser pipe (4) and preferably a pressure relief valve (3), which riser pipe (4) is connected via a pressure hose (5) to a piston rod pipe (9), so that material from the pressure vessel (1) into a through the support form (6a, 6b) formed space (6) can be brought, which space (6) is closed by a piston surface (8) such that the piston (8,9) under the pressure of the material flowing into the space (6) in The opposite direction of the material flow can be shifted. System according to claim 10, characterized in that at least one reinforcement guide (8a) for the endless, oriented reinforcement (11) is provided in the piston surface (8), and a fastening device (7), in particular a clamping device, in the end face (6b), for reinforcement. Installation for carrying out the method according to one of claims 1 to 9, with at least one extruder, characterized in that the at least one extrusion head (13) tapers in the direction of the mouth, and that the extrusion head is elongated at the top and at the side in comparison to the bottom . Plant according to claim 12, characterized in that the flow course of the material upon entry into the at least one extrusion head (13) is severely broken with a deflection, in particular a deflection of approximately 90 °. System according to claim 12 or 13, characterized in that the at least one extrusion head (13) is arranged such that the material is discharged at the mouth of the at least one extrusion head (13) into a support mold (6a, 6b). Installation according to any one of claims 12 to 14, characterized in that there is a drag mold (14) above and in front of the at least one extrusion head (13, 13b) which is shaped in accordance with the rear of the component. System according to one of claims 12 to 15, characterized in that a vibrator (15) is provided on the drag form (14). Installation according to one of claims 12 to 16, characterized in that it has at least two extrusion heads (13a, 13b) and that between the at least two extrusion heads (13a, 13b) at least one reinforcement guide (8a) is provided, by means of which a reinforcement ( 11) and can be fastened to the end face of the support mold (6a) by means of a fastening device (7). Installation according to one of claims 12 to 17, characterized in that the at least one extrusion head (13) is arranged opposite the support mold (6a, 6b) to form an acute angle.

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