Process for Anchoring of Fasteners in a Base

The invention, for one, concerns a reactive set for producing a synthetic resin body used for anchoring fasteners in a base through employment of destructible multiple chamber cartridges. Specifically, the invention is geared to a specific combination of components of the reactive set for production of a synthetic resin body, a destructible multiple chamber cartridge for anchoring fasteners in a base, and an anchoring process where the multiple chamber cartridge contains the specific reactive set.

It has been known for a long time to use curable synthetic resins for the safe fastening of anchoring rods and similar in solid rock, masonry, concrete and similar. The starting components of the synthetic resin and synthetic resin hardener are separately brought to the point of fastening and mixed there by driving the fastener in. Thus, the formation of the cured synthetic resin body that glues the fastener to the base is initiated only when the fastener is contained in its final position.

The meanwhile widespread popularity of this technique is attributable, among others, to the use of destructible cartridge which permit a convenient introduction of resin components and synthetic resin hardeners in boreholes for anchoring rods and, moreover, facilitate the storage, transport and dosing of the reactive starting materials of the synthetic resin body.

Cartridges containing reactive sets for the production of cured synthetic resin bodies were described already in the German patent publication No. 12 05 038, in conjunction with a process for the fastening of anchoring rods without spreader head in the anchored constriction of mining spaces. Concerned there are glass or bakelite cartridges into whose charge from curable polyester or epoxy resin and similar or larger quantity by weight of quartz sand or meal a capsule is introduced that contains the hardener. According to this document, organic peroxides are used in conjunction with polyesters. In the case of preaccelerated epoxy resins, an amine hardener is used. Although cartridges with reaction sets of that type have been used for several years in the fastening technology, they are associated with considerable drawbacks. These consist in the slow curing of preaccelerated epoxy resins with amine hardeners so that, when a quick load bearing capability of the fastener is required, the glass cartridge and the anchoring rod need to be preheated to temperatures above 150.degree. C. With the peroxide-cured polyester resins it proves to be disadvantageous that they are insufficiently resistant to chemicals, specifically not resistant to alkali. Especially in a basic base this leads in the long run to a reduction of the mechanical properties of the synthetic resin body. Moreover, such cured polyester resins also display a relatively high water absorption, which in conjunction with metallic fasteners may cause corrosion problems.

To eliminate the disadvantages of such prior materials, the European patent application 1 150 555 suggested dual chamber cartridges where a fine-grained, natural or synthetic mineral filler, together with a vinyl ester epoxy resin on acrylate or methacrylate basis, is contained in the inner or outer chamber of a dual cartridge constructed of two nested glass cylinders while the hardener--an organic peroxide--is contained in the respective other chamber. The peculiarity of cartridges according to the European patent application 0 150 555 consists in the fact that a reactive vinyl monomer is admixed to the resin component.

The synthetic resin substances according to the European patent application 0 150 555 represent a significant advancement over previously known resin compositions insofar as, for one, they cure faster than previously used epoxy resins and, for another, they are in terms of alkali resistance superior to the previously used polyester resins. Nonetheless, also the synthetic resin bodies which according to the recipe taught by the European patent application are obtained upon crushing the glass cartridges and curing of the components of the reaction set have considerable disadvantages: for one, such synthetic resin bodies do not represent a sufficiently effective diffusion barrier against reactive compounds, such as hydrochloric acid or diffusing water vapor. This relatively high permeability to low-molecular substances causes ultimately a reduction of the corrosion resistance of the metallic fastener. Another grave disadvantage of anchoring obtained with synthetic resin bodies according to the specification of the European patent application 0 150 555 is constituted by its mechanical performance. Under sustained load, synthetic resin bodies obtained in this way tend to soften. As a result of the resin matrix creepage caused thereby, a safe anchoring over longer periods of time cannot be guaranteed with such synthetic resin material under sustained load, due to the risk of fastener slippage. Thus, this resin type is unsuited for many applicational areas in construction where the fastener must safely withstand decades of tractive stress.

This disadvantage is amplified ye tin that the somewhat satisfactory curing speed, as a result of which the fastener can be stressed a relatively short time thereafter, is caused by a high percentage of hardener component in the resin recipe. The high percentage of organic peroxide such as taught in the European patent application 0 150 555, for one, causes a quick curing of the synthetic resin mixture though, while on the other hand it has the undesirable side effect of promoting also the quick aging of the synthetic resin body. Given with the chemical changes which in the course of time reduce the adhesion of the resin to the surrounding base and to the fastener and adversely affect the inner structure and thus the strength of the synthetic resin substance itself (brittling) is another risk factor which makes the long term use problematic.

Disadvantageous, furthermore, is that the curing time of several days must still be allowed, despite a comparatively high curing speed at normal temperatures (25.degree. C.), and even elevated temperatures (35.degree. C.) require curing times in the range of hours, until the fastener can be subjected to load. For many practical purposes where cost intensive waiting periods are caused in that an anchored fastener cannot be subjected to load yet, the application of the teaching of the European patent application 0 150 555 is giving rise to problems.

Another negative aspect of the prior art is the dissatisfactory shelf life of the synthetic resin components in the cartridges, especially at elevated temperature.

The problem underlying the invention is to provide a reactive set, specifically for use in multiple chamber cartridges, for the production of a synthetic resin body that causes the anchoring of fasteners in the base and is characterized in that it produces after a short curing time highly loadable anchorings which remain consistently stable under mechanical sustained load, display a high resistance to acid and alkali, form an effective diffusion barrier to low-molecular compounds and possess an equally high adhesion to metals and natural and synthetic mineral materials and, when needed, can be so designed, without reducing their properties which are essential in practice, that a shelf life at elevated temperatures is given.

This problem is solved through the reactive set for producing synthetic resin bodies, specifically for use in destructible multiple chamber cartridges for anchoring fasteners in a base, where in the reaction set there are contained 18-25 parts by weight of a preaccelerated resin component containing, as ingredients

A) 3-60 parts by weight of a vinyl ester epoxy resin,

B) 28-45 parts by weight of one or several ethylenically unsaturated monomer compounds,

C) 63-3 parts by weight of an unsaturated polyester, and

D) 10-0.1 parts by weight of epoxy resin,

b) 0.4-1.2 parts by weight of a hardener component comprising an organic peroxide, and

c) 40-55 parts by weight of a filler component, and additionally accelerators, polymerization inhibitors and, as the case may be, other usual additives.

The invention includes also a destructible multiple chamber cartridge for the in-situ production of synthetic resin bodies for fastening anchoring elements in boreholes, where the cartridge contains the inventional reactive set and where the organic peroxide hardener and the preaccelerated resin component are contained, separate from each other, in different chambers.

The inventional destructible multiple chamber cartridge is used in processes for anchoring a fastener in a base, by introducing in a borehole in the base a destructible multiple chamber cartridge that contains the components of a curable adhesive and where the cartridge is destroyed and the synthetic resin components are mixed by driving the fastener in, whereafter the synthetic resin cures.

Preferred embodiments of the invention are described in the subclaims.

Surprisingly, it was found that the combination of the components (A), (B), (C) and, as the case may be, (D) yields the combination of properties for solving the problems.

The addition of the epoxy resin (D)--with epoxy resins of the type bisphenol A being used preferably--leads to a considerably prolonged shelf life of the synthetic resin component of the reactive set at elevated temperature (sustained shelf life at temperatures around 50.degree. C.).

Despite the very different reactivity of the components (A), (C) of the preaccelerated resin component, entirely unexpectedly, a homogeneous and clear product is obtained. Surprising as well is the absence of gas bubble formation during the curing of the synthetic resin substance from the inventional reactive set. Ultimately, this guarantees a uniform plastic body. Already the absence of inhomogeneities in the synthetic resin itself eliminates a source of possible failures of the adhesive anchoring.

Without intending to derive a theory thereof, it is pointed out that in the novel reactive product a higher degree of cross-linking may result from the inventional reactive set with (A), (B), (C) and, as the case may be, (D) in the resin component. The considerably greater chemical resistance to state-of-the-art resins may be attributable to a better shielding of the ester groups caused thereby.

Such a structure may offer also a plausible explanation for the considerably greater resistance of the synthetic resin body from the inventional reactive set to diffusing mediums. It is pointed out especially that a high curing speed is given with the inventional reactive set, despite the comparatively very low amount of peroxide hardener. Preferred with regard to its balanced reactivity, miscibility under the threading conditions of the anchoring rod to be fastened and to the obtainable sustained load bearability of the resulting resin body are reactive sets which contain in the vinyl ester epoxy resin an epichlorohydrine epoxy resin of the type bisphenol A. Regarding the handlability and reactivity, the vinyl ester epoxy resin (A) preferably has in general a mean mole mass of 450 to 1200 Dalton, an ester number of 80 to 150 mg KOH/g resin and, when available in the form of a solution of 55 to 70% wt. (A), that it has a viscosity of 400 to 1000 mPas at 23.degree. C.

Due to its satisfactory reactivity and cost advantages associated with simple accessibility, styrene and/or methyl methacrylate is especially suited as ethylenically unsaturated monomer (B).

As regards their chemical nature, specifically unsaturated polyesters on the basis of o-phthalic acid and/or m-phthalic acid or isophthalic acid with ethylene glycol and/or propylene glycol and/or trycyclodecan dimethanol and/or neopentyl glycol are suited as polyester resins (C). Regarding the reactivity and handlability, flow performance and miscibility, it proves to be favorable to use polyester resins (C) whose ester number ranges from 180 to 320 mg KOH/g resin and which, when available in the form of a solution of 50 to 70% (C) monomer used, have a viscosity of 800 to 6,000 mPa s at 23.degree. C. Especially suited as epoxy resin component (D) are such whose epoxy equivalent weight ranges from 160 to 200 g/equivalent and their viscosity from 2,500 to 4,000 mPas at 23.degree. C.

The inventional reactive set is preferably used in a multiple chamber cartridge containing the hardener and the preaccelerated resin component in different chambers. The filler may be contained, along with the preaccelerated synthetic resin, in one chamber. This arrangement suggests itself when the cartridge is fashioned as a dual chamber cartridge, such as customary in the art.

Surprisingly, especially good results can be achieved with regard to strength and durability of the anchoring of the fastener when observing in the design of the multiple chamber cartridge from glass a weight ratio of 20 to 35 parts by weight of cartridge glass at 18 to 25 parts by weight of the preaccelerated resin component of the inventional reactive set, 0.4 to 1.2 parts by weight of peroxide hardener and 40 to 55 parts by weight of the filler component.

The filler component consists preferably from fine-grained quartz, magnesia clinker, marble meal or similar.

The inventional procedure for anchoring a fastener in the base is suitably such that a destructible multiple chamber cartridge containing the inventional reactive set is in customary fashion introduced in a borehole in the base. Next, by driving the fastener in, the cartridge is destroyed, the hardener previously separated from the preaccelerated synthetic resin component is mixed with the material to be cured, thus initiating the in-situ curing reaction.

The following examples show the reduction of the present invention and illustrate the superior properties of the inventional combination over the art.