US20050097850A1

US20050097850A1 - Method for fastening anchoring means and device suitable for this purpose

Info

Publication number: US20050097850A1
Application number: US10/930,925
Authority: US
Inventors: Rainer Hettich; Thomas Buergel; Klaus Schaefers; Erich Leibhard
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2003-09-02
Filing date: 2004-08-31
Publication date: 2005-05-12
Also published as: DE10340394A1; DE10340394B4

Abstract

A method is described for fastening anchoring means, especially anchor rods, reinforcing iron, etc. in solid substrates by introducing a curable mortar composition and the anchoring means into a borehole provided in the solid substrate and curing the mortar composition, the curing of the mortar composition being initiated or brought about by introducing microwave energy over the anchoring means into the borehole. Furthermore, a device is described for carrying out this method, the device having an adapter unit (1), which can be connected over a coaxial cable or a waveguide (2) with the microwave generator, and a collet chuck (3), for frictionally fixing the adapter unit to the anchoring means (4) and for passing microwave energy into the mortar composition (7) present in the borehole (5) of the solid substrate (6), and a shielding (8), surrounding the collet chuck (3).

Description

1. BACKGROUND OF THE INVENTION

1. Field of Invention
The present invention relates to a method for fastening anchoring means, especially anchor rods, reinforcing iron, etc. in solid substrates such as concrete or masonry, by introducing a curable mortar composition and the anchoring means into a borehole, which is provided in the solid substrate, and curing the mortar composition, as well as to a device for carrying out this method.
2. Description of the Prior Art
Normally, in order to fasten anchoring means such as anchor rods, reinforcing iron or similar elements in a borehole in solid, mineral substrates, such as concrete or masonry, curable mortar compositions, especially two-component mortar compositions based on (methh)acrylates or epoxide resins are used. After the components of the curable mortar composition, which react with one another, are mixed, these curable mortar composition have a certain pot life, during which the element, which is to be fastened, can be set, and, after of a further period of time, namely the curing time, attain their final strength through curing. Under normal conditions, the aforementioned pot life falls within the range of a few minutes. The curing time generally ranges from a few minutes up to hours. In every case, the reaction times are coupled with one another. This means that, when the pot life of the curable mortar composition is long, the curing time is also long and vice versa. These times can vary depending on surrounding conditions, particularly on the temperature.
Attempts by the applicant to uncouple the curing rate from the pot life by supplying heat by way of the anchoring means to the curable mortar composition, lead to very strong heating of the mortar composition in the outer region and to a lesser heating in the inner regions of the borehole and, with that, to a nonuniform curing.
The EP-A-0 412 055 discloses a method for producing a block material with a high filler content. The method includes pressing a filler-containing reaction resin composition and heating the green compact obtained, in the pre-pressed form, in a microwave induction furnace or in a high-frequency furnace to a temperature of 70° to 150° C., in order to bring about curing in this way.
The object of the EP-A-0 933 498 is a method for the rapid consolidation of particulate materials in wells. The method consists of coating particulate material with a curable resin composition and irradiating the coating of curable resin composition on the particular material with microwaves, in order to accelerate the curing of the resin composition. The only example illustrates the curing of the resin-impregnated particulate material in small glass tubes, which are brought into a microwave furnace.
The EP-A-0 598 433 describes a method for curing polymerizable liquid compositions, which contain polyisocyanates and epoxides as well as a catalyst, by irradiating them with pulsed or continuous electromagnetic radiation in the microwave frequency range of 10⁸to 10¹¹Hz. In this case also, the material is cured in a microwave furnace.
Finally, the EP-B-0 655 472 discloses liquid compositions based on organic isocyanates and epoxy compounds, which can be cured by microwave radiation and are cured to a solid state by the action of non-ionizing, electromagnetic radiation with a frequency in the microwave frequency range.
It is an object of the present invention to provide a method of the type given above, which enables the curing of the curable mortar composition to be initiated at a desired time independently of the pot life and a rapid, complete and homogeneous curing of the mortar composition to be brought about in the whole volume of the borehole, as well as to indicate a device suitable for this purpose.
The problems, which arise when anchoring means are fastened in boreholes, are not disclosed in any publication. Neither is any suggestion made concerning the above-addressed uncoupling of pot life and curing time, that is, in relation to how to achieve a rapid and uniform curing and, at the same time, a long pot life.

SUMMARY OF THE INVENTION

Surprisingly, it has turned out that it is possible to initiate or bring about the curing of the curable mortar composition by passing microwave energy over the component into the curable mortar composition present in the borehole.
Accordingly, the object of the invention is achieved by providing a method for fastening anchoring means, especially anchor rods, reinforcing iron or similar components in solid substrates by introducing a curable mortar composition and the anchoring means into a borehole, which is provided in the solid substrates, and curing the mortar composition by passing microwave energy over the anchoring means into the borehole.
Pursuant to the invention, the rapid curing of the curable mortar composition due to the action of the microwave radiation can take place by two different mechanisms, namely, on the one hand, by a homogeneous heating of the reaction mortar within the whole of the borehole and, on the other, by the activation of the curing reaction by releasing or activating a necessary reactant for the curing reaction, which is distributed homogeneously in the curable mortar composition. At the same time, the mortar composition is heated homogeneously or the curing reaction is activated simultaneously in the whole volume of the mortar composition under the action of the microwave energy, which is passed over the anchoring means into the curable composition and is spread out uniformly or homogeneously in the latter. Due to the introduction of the microwave energy, a uniform curing reaction is achieved and regions of different temperature or reaction rates, which arise when the curing reaction is accelerated or initiated from the upper side of the borehole, do not occur.
In accordance with a first embodiment of the invention, the curing of the mortar composition takes place due to the homogeneous heating of the mortar composition under the action of microwave energy. As is well known, the electromagnetic waves of the microwave radiation consist of an electrical and a magnetic field, the electric and magnetic field vectors being perpendicular to one another. When a body absorbs microwave energy, the adsorption can take place in two different ways, namely, on the one hand, owing to the fact that a portion of the electric field of the microwave radiation is absorbed. This is also referred to as dielectric absorption. This can happen, for example, due to polar substances, such as water. The second possibility consists of ferromagnetic absorption, for which a portion of the magnetic field is absorbed. This can be achieved, for example, due to the presence of ferromagnetic materials in the mortar composition.
In accordance with a preferred embodiment of the invention, the dielectric absorption of microwave energy in the mortar composition is favored by polar components, which are incorporated in the mortar composition and comprise polar monomers, polar initiators and/or finely particulate auxiliary materials and/or additives, such as a carbon black, carbon fibers, electrically conducting titanium dioxide, finely divided metallic copper with a particle size preferably from 1 to 50 μm, and/or finely divided stainless steel, preferably with a particle size of 1 to 100 μm.
In accordance with a further preferred embodiment of the invention, the ferromagnetic absorption of the microwave energy by the mortar composition is realized by ferromagnetic particles, which are incorporated in the mortar composition and heat the latter homogeneously. For this purpose, ferromagnetic particles of, for example, ferromagnetic mixed oxides, such as Bayferrox 318 M, can be used.
In accordance with the second alternative of the inventive method, the mortar composition is cured by the release or activation of a necessary reactant, particularly a curing component, such as an initiator or accelerator of the curing reaction in the mortar composition under the action of microwave energy. A preferred embodiment of this object of the invention consists therein that the curing agent components, present in microwave-sensitive microcapsules in the mortar composition, are released from the microcapsules under the action of microwave energy. The microwave-sensitive microcapsules are microcapsules or microspheres of a plastic enveloping material, such as amino resins, which are opened or broken open by the action of microwave energy, so that the reactants, contained in the microcapsules distributed uniformly in the curable mortar composition, are released in the whole of the curable mortar composition.
In accordance with a preferred embodiment, the release of the necessary reactant of the curing reaction, namely of the curing agent components, from the microwave-sensitive microcapsules is favored by introducing microwave-sensitive additives into the microcapsules and/or into the wall of the microcapsules and, preferably, additionally by introducing a blowing agent into the microcapsules. When polar blowing agents are used, it is possible omit the microwave-sensitive additives partly or completely.
As microwave-sensitive additives, present in the microcapsules or in the wall of the microcapsules, preferably conducting carbon blacks, carbon fibers, electrically conducting titanium dioxide, ferromagnetic mixed oxides, iron oxide, finely divided metallic copper and/or finely divided stainless steel can be used pursuant to the invention. As blowing agents, present in the microcapsules, materials can be used, which do not affect the curing reaction and, under the action of microwave energy, cause evaporation or an evolution of gases, which leads to an increase in pressure in the interior of the microcapsules and causes them to burst. Preferred blowing agents of this type are water, low-boiling organic substances such as pentane, hexane or heptane, azo compounds, hydrazine derivatives, semicarbazides, tetrazoles, benzoxazines, etc., as well as mixtures of such blowing agents.
In accordance with a further embodiment of the invention, the curing reaction of the curable mortar composition is initiated by the action of microwave energy due to microwave-sensitive quaternary ammonium salts, present in the mortar composition. Preferably, as microwave-sensitive quaternary ammonium salts, those compounds are used which, under the action of microwave energy, release tertiary amines, which accelerate the free radical polymerization of the curing reaction.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in greater detail below with reference to the attached drawing, in which
FIG. 1 shows a diagrammatic, sectional view of the preferred, inventive device and
FIG. 2 shows a diagrammatic, sectional view of a sieve of a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A further object of the invention is a device for carrying at the method described above, which, as is shown in FIG. 1, is characterized by an adapter unit (1), which can be connected over a coaxial cable or a waveguide (2) with a microwave generator and has a collet chuck (3) for frictionally fixing the adapter unit to the anchoring means (4) and for introducing microwave energy into the mortar composition (7) present in the borehole (5) of the solid substrate (6) and into shielding (8) surrounding the collet chuck (3).
Preferably, the collet chuck (3) and the shielding (8) consist of metal, preferably an elastic copper-beryllium alloy and particularly a CuBe2 alloy. Moreover, the collet chuck (3) is designed so that it is suitable for accommodating anchoring means (4) of different diameters, the clamping width being adapted to the diameter of the anchoring means usually employed.
For carrying out the method using the claimed device, initially a borehole is produced in the solid substrate (6) of, for example, concrete or masonry. The internal diameter of the borehole is adapted to the external diameter of the anchoring means in such a manner, that, after the anchoring means are introduced and the curable mortar composition has been cured in the remaining annular gap, the required strengths or pullout forces are achieved. Subsequently, an amount of curable mortar composition, required for this purpose, is introduced into the borehole.
A one-component mortar composition can be introduced directly into the borehole. On the other hand, the two components of a curable, two-component mortar composition initially must be mixed preferably with the help of a static mixer before they are introduced into the borehole. Subsequently, the anchoring means, such as an anchor rod, are brought into the borehole and optionally adjusted. The inventive device with the collet chuck (3) is then brought into frictional connection with the anchor rod protruding out of the borehole, the shielding (8) is disposed during or after the clamping process and the adapter unit (1) is connected over the coaxial cable or the waveguide (2) with a microwave generator, which is not shown in the Figure. In so doing, it is necessary to take care that the shielding is seated on the firm substrate and spreading of the microwave energy towards the outside is prevented. After the microwave generator is switched on, the microwave energy, with an output of, for example, 100 to 1000 W and preferably of 200 to 500 W, is insolated over the coaxial cable, the collet chuck and the anchor rod into the borehole and, with that, distributed homogeneously and simultaneously over the whole of the curable mortar composition. By insolating a microwave energy for 1 to 3 minutes into the curable mortar composition, the curing reaction is initiated and then completed after about 15 minutes, as can be seen by the attainment of the aimed-for load value of the anchoring of 20 to 50 kN.
The curable mortar composition may be a conventional one-component or two-component mortar composition. Preferably, it is based on (meth)acrylates or epoxide resins.
In the case of curable one-component mortar compositions, preferably mixtures of acrylate resins, such as, preferably, pentaerythritol tetraacrylate and/or polyurethane hexaacrylate, peroxide curing agents, such as tetrabutylammonium persulfate, fillers such as quartz sand, and thixotropic agents, such as pyrogenic silica, are used. According to a preferred inventive embodiment, additives, such as ferromagnetic particles, carbon black or carbon fibers are furthermore added to improve the dielectric and/or ferromagnetic absorption.
In the case of curable two-component mortar compositions, preferably epoxide resins are used, especially those based on aliphatic and aromatic glycidyl ethers and preferably those based on bisphenol A and/or butylene glycol diglycidyl ether, which components are present together with fillers, especially powdered quartz, in one component, while the amine curing agent, such as oligomeric Mannich bases or triethylenetetramine, and fillers, such as powdered quartz, are contained in a second component. It is also possible to use curable two-component mortar compositions, which are based on (meth)acrylates, such as polyurethane methacrylate or trimethylolpropane trimethacrylate, which resins, together with fillers, such as quartz sand and pyrogenic silica, are contained in one component, which optionally and additionally contains diethylaniline together with conducting carbon black in microcapsules, while the other compliment contains the peroxide curing agent, especially benzoyl peroxide, fillers, such as powdered quartz and/or pyrogenic silica, as well as further additives such as di-isobutyl phthalate.
In accordance with a further preferred embodiment of the invention, the device comprises an electrically conducting sieve (9), which improves the effectiveness of the entry of microwave energy into the curable mortar composition. This sieve (9) has openings, through which the mortar composition can pass, and preferably consists of an electrically conducting material, which has insulation on the inside. An electrically conducting material, preferred for this sieve, comprises metals, such as elastic copper-beryllium alloys, especially the alloy CuBe2. The insulation on the inside of the sieve can be formed, for example, by a plastic, preferably by a thermosetting plastic, or by ceramic. This sieve preferably is in the shape of a cylinder with a diameter between the external diameter of the anchoring means and the internal diameter of the borehole. The cylindrical sieve is closed off at one end and has a flange, which extends radially outward, at the other end. A preferred embodiment of the sieve is shown in FIG. 2.
As can be inferred from FIG. 1, the sieve (9) is brought into the borehole in such a manner, that the flange rests flat on the solid substrate at the opening of the borehole. After that, the required amount of a curable mortar composition is filled into the borehole and the anchor rod is then inserted. Subsequently, the adapter unit, which is equipped, in accordance with a preferred embodiment, with a flange-like extension at its end facing the solid substrate, is set down on the flange of the metallic sieve, so that direct contact is achieved between the sieve and the shielding of the adapter unit. After that, as already described above, the adapter unit is connected over the collet chuck with the anchor rod and, over the coaxial cable or the waveguide, with the microwave generator. The microwaves, produced in the microwave generator, are coupled over the coaxial cable or the waveguide with the adapter unit and then passed over the anchor rod, which is fixed firmly in the frictionally fastened collet chuck and acts as antenna, into the borehole. Due to the arrangement of the sieve and pursuant to the invention, a concentration of the microwave radiation is brought about in the borehole and, with that, an improvement in the efficiency of the insolation and absorption of microwave energy is achieved. As a result, when an electrically conducting sieve with insulation on the inside is used, the irradiation of microwave energy, required for the complete curing of the mortar, can be reduced by about a half.
The following examples explain the invention further.

EXAMPLE 1

The two components of a curable, two-component mortar composition are prepared from the following constituents:
Component A:

- 30.0% epoxide resins based on bisphenol A (Araldit GY 250)
- 20.0% butylene glycol diglycidyl ether
- 50.0% powdered quartz
  Component B:
- 40.0% oligomeric Mannich base
- 20.0% triethylenetetramine
- 40.0% powdered quartz

After the two components A and B are prepared by mixing the individual constituents, they are mixed in a ratio above volume of 3:1 with the help of a static mixer. The curable mortar composition, obtained in this way, has a pot life at room temperature of about 30 minutes. The mortar composition is then brought into a borehole, which is drilled with an internal diameter of 14 mm and a depth of 130 mm in concrete of quality C20. The anchor rod, with an external diameter of 12 mm, is then introduced into the borehole, the adapter unit is connected frictionally over the collet chuck with the end of the anchor rod protruding out of the borehole and the shielding is placed on the surface of the solid concrete substrate. Subsequently, a microwave generator is connected over a coaxial cable and operated for about three minutes with insolation of 500 W of microwave energy. A load value (pullout force) of the anchor rod of 40 kN is achieved 15 minutes after the irradiation.
Due to the use of an electrically conducting sieve of the type described above, the irradiation time can be reduced by about a half, the load value level of approximately 40 kN remaining the same.

EXAMPLE 2

A curable two-component mortar composition is prepared from the following constituents.
Component A:

- 20.0% polyurethane methacrylate
- 30.0% trimethylolpropane trimethacrylate
- 43.0% quartz sand
- 5.0% of the above microcapsules
- 2.0% pyrogenic silica (Cab-O-Sil R 202)
  Component B:
- 40.0% benzoyl peroxide/phthalate paste (50% BPO)
- 20.0% di-isobutyl phthalate
- 37.0% powdered quartz
- 3.0% pyrogenic silica

The microcapsules, contained in Component A, where formed by encapsulating diethylaniline and carbon black (Vulcan XC72R) jointly in a melamine resin. These microcapsules have a diameter of 1 to 150 μm and the following composition:

- 35% of the microcapsule wall material (melamine resin)
- 60% of diethylaniline
- 5% of carbon black (Vulcan XC 72R)

The two components A and B are mixed in a ratio by volume of 7:1 with the help of a static mixer and form a curable mortar composition with a pot life at room temperature of more than one day. This mortar composition is introduced into a borehole with a diameter of 16 mm and a depth of 130 mm, which is drilled into concrete C20 and in which there is a sieve of the type defined above. Finally, an anchor rod, with a diameter of 12 mm, is introduced and connected with the microwave generator in the manner described in Example 1. In the course of one minute, microwave energy of 1000 W is insolated over the microwave generator. After 15 minutes, a load value of the anchor rod of 33 kN is achieved.

EXAMPLE 3

A curable one-component mortar composition is prepared from the following constituents:

- 50.0% pentaerythritol tetraacrylate
- 24.0% polyurethane hexaacrylate (Craynor 975)
- 3.0% pyrogenic silica (Aerosil TS 720)
- 5.0% tetrabutylammonium persulfate
- 1.0% 1,3-di(2-t-butylperoxy isopropyl)benzene (DIPP-2)
- 15.0% quartz sand
- 1.5% ferromagnetic mixed oxides (Bayferrox 318 M)
- 0.5% conductive carbon black (Vulcan XC72 R)

The curable mortar composition obtained, with a pot life at room temperature of more than two weeks, is introduced into the borehole as a single component in the manner described in Example 1, the anchor rod is set, the adapter unit is arranged and microwave radiation with a power of 500 W is passed for 30 seconds over the anchor rod into the curable mortar composition. A load value of the anchor rod of 44 kN is achieved after insolation lasting 15 minutes.
It can be seen from the above examples that, with the help of the inventive method and, preferably, using the claimed device, it is possible to achieve the objective posed above of uncoupling the curing rate from the pot life of the curable mortar composition, in that the curing of the mortar composition can be initiated or brought about selectively and homogeneously within the borehole by the insolation of microwave energy. At the same time, very uniform, high load values of the anchoring means, anchored in the solid substrate, can be achieved.

Claims

1. Method for fastening anchoring means, especially anchor rods, reinforcing iron, etc. in solid substrates, by introducing a curable mortar composition and the anchoring means into a borehole, which is provided in the solid substrate, and curing the mortar composition, characterized in that the curing of the mortar composition is effected by passing microwave energy through anchoring means into the borehole.

2. The method of claim 1, characterized in that the curing of the mortar composition takes place due to the homogeneous heating of the mortar composition due to the action of the microwave energy.

3. The method of claim 2, characterized in that the homogeneous heating is brought about by dielectric and/or ferromagnetic absorption of microwave energy by the mortar composition.

4. The method of claim 3, characterized in that the dielectric absorption of microwave energy by the mortar composition is favored by dielectrically absorbing constituents, incorporated in the mortar composition.

5. The method of claim 4, characterized in that polar monomers, polar initiators and/or polar auxiliary materials, such as carbon black, carbon fibers, electrically conducting titanium dioxide, finely divided metallic copper, preferably with a particle size of 1 to 50 μm, and finely divided stainless steel, preferably with a particle size of 1 to 100 μm, are used as dielectrically absorbing constituents.

6. The method of claim 3, characterized in that the ferromagnetic absorption of the microwave energy in the mortar composition is favored by ferromagnetic particles, preferably ferromagnetic mixed oxides, which are incorporated in the mortar composition.

7. The method of claim 1, characterized in that the curing of the mortar composition takes place due to the release or activation of a necessary reactant for the curing reaction, preferably of a curing agent constituent in the mortar composition, under the action of the microwave energy.

8. The method of claim 7, characterized in that reaction initiators and/or reaction accelerators are released in the mortar composition as curing agent components due to the action of microwave energy.

9. The method of claim 7, characterized in that the reactants for the curing reaction, preferably the curing agent constituents, which are to be released in the mortar composition, are present in the mortar composition in microwave-sensitive microcapsules and are released from the microcapsules due to the action of microwave energy.

10. The method of claim 9, characterized in that the release of curing agent components from the microwave-sensitive microcapsules is promoted by microwave-sensitive additives present in the microcapsules and/or in the walls of the microcapsules, and/or by introducing a blowing agent into the microcapsules.

11. The method of claim 10, characterized in that conductive carbon blacks, carbon fibers, electrically conducting titanium dioxide, ferromagnetic particles, mixed oxides, iron oxide, finely divided metallic copper and/or finely divided stainless steel are used as microwave-sensitive additives, present in the microcapsules and/or in the walls of the microcapsules.

12. The method of claim 10, characterized in that water, low boiling organic compounds, preferably heptane, azo compounds, hydrazine derivatives, semicarbazides, tetrazoles and/or benzoxazines are used as blowing agent's, which are present in the microcapsules.

13. The method of claim 7, characterized in that the curing reaction is initiated, under the action of microwave energy, by microwave-sensitive quaternary ammonium salts, present in the mortar composition.

14. The method of claim 13, characterized in that quaternary ammonium salts, which, under the action of microwave energy, release tertiary amines that accelerate the free-radical polymerization of the curing reaction, are used as microwave-sensitive quaternary ammonium salts.

15. A device for curing a motor composition, comprising an adapter unit (1), which can be connected over a coaxial cable or a waveguide (2) with a microwave generator, a collet chuck (3) for frictionally fixing the adapter unit to the anchoring means (4) and for introducing microwave energy into mortar composition (7) present in the borehole (5) of the solid substrate (6), and a shielding (8) surrounding the collet chuck (3).

16. The device of claim 15, characterized in that the collet chuck (3) and the shielding (8) are produced from metal, preferably from an elastic copper-beryllium alloy and especially from the CuBe2 alloy.

17. The device of claim 15, characterized in that the collet chuck (3) is designed to accommodate anchoring means (4) of different diameters.

18. The device of claim 15, characterized by an electrically conducting sieve (9), which surrounds the part of the anchoring means (4) in the borehole (5), is isolated therefrom and can be brought into contact with the adapter unit (1), for improving the efficiency of entry of the microwave energy.

19. The device of claim 18, characterized in that the sieve (9) has openings, through which the mortar composition (7) can pass.

20. The device of claim 18, characterized in that the sieve (9) consists of an electrically conducting material, which has insulation on the inside.

21. The device of claim 18, characterized in that the sieve (9) has the shape of a cylinder with a diameter between the external diameter of the anchoring means and the internal diameter of the borehole, the cylinder being closed at one end and provided at the other end with a flange extending radially outward.