BACKGROUND OF THE INVENTION 1. Fleld of the Invention The present invention relates to a novel rock bolt anchoring system which can be used, for example, in anchoring a reinforcement member in the hole of a rock formation or a structural body. The present invention also relates to a method of using the rock bolt anchoring system. Particular applicability is found in the anchoring of mine bolts.

2. Description of the Related Art Reactive systems for anchoring reinforcing members in holes in rock formations or structural bodies are commonly used in various industries. For example, in the mining industry, reactive systems are used to secure bolts used in mine roofs to prevent collapse thereof.

Such systems typically include two parts. The first part is a hardenable synthetic resin component, and the second is a cross-linking catalyst component.

Prior to use, the two components are kept isolated from one another. Upon mixing of the first and second components, the catalyst initiates a cross-linking reaction in the synthetic resin component, resulting in a hardened (cured) resin.

U.S. Patent Nos. 4,260,699, 4,273,689, 4,280,943, 4,518,283 and 4,616,050

disclose various two-component reactive systems, the contents of which are herein incorporated by reference.

In two-component reactive systems, the resin and the catalyst formulations can be held in separate compartments in a single container, commonly referred to as a capsule, a sausage, a cartridge, or an ampule. The two formulations are separated, for example, by one or more plastic walls or a plastic film. The capsule is inserted into a hole in the rock formation or body in which the bolt is to be secured. The bolt is next inserted through the capsule to the back of the hole and is then spun. The wall or walls separating the compartments are thereby broken, causing the resin component and the catalyst component to mix together and react, thereby hardening around the bolt. After being spun, the bolt is held in place by applying a force against the bolt until the resin is set.

The acceptance of a two-component rock anchoring system is dependent upon numerous properties measured by those skilled in the art. Such properties include, for example, displacement, yield point and stall. Tests for measuring these properties are known in the art. For example, various tests are provided in the MSHA Standard Block Test, the contents of which are herein incorporated by reference.

A hardenable synthetic resin composition that has gained wide acceptance as a component of rock bolt anchoring systems is a composition containing an unsaturated polymerizable polyester resin and a monomeric polymerizable ethylenic cross-linking agent therefor. These materials, together with a polymerization inhibitor or stabilizer and a promoter for a peroxide catalyst constitute a first part of the system or the resin component. A peroxide catalyst system for initiating the crosslinking polymerization is contained in a second part of the system or the catalyst component. The catalyst component is kept separated from the resin component until the hardening reaction is to take place. When the two components are combined and mixed, the action of the catalyst causes the

cross-linking reaction between the polyester and ethylenic monomer to take place, resulting in a thermoset, hard resin.

Typical catalyst components are based on an organic peroxide, such as dibenzoyl peroxide. Because such a catalyst is highly viscous, flowability thereof must be increased to improve its effectiveness. It is known to add to the catalyst formulation a diluent, such as mineral oil and/or water, to improve flowability thereof.

The use of such diluents, however, has led to significant leakage problems after installation of a reinforcement member. Such leakage is marked, for example, by liquid dripping from the bolt head.

Additional problems associated with known reactive systems have been encountered by operators during mine bolt installation, for example, when a mine bolt is inserted through a reactive system container to the back of a drilled hole.

Because of the relatively large hole length and the relatively small annulus between the bolt and hole, significant pressures at the back of the hole can be built up during the insertion step. This is a result, in particular, of the highly viscous nature of the known systems.

Moreover, conventional reactive systems make it very difficult to determine the point at which bolt spinning during installation should be terminated. This endpoint varies considerably with atmospheric conditions, such as temperature and humidity. Consequently, bolts may be overspun when using such reactive systems, resulting in a reduction in the integrity of the cured resin.

A substantial amount of operator time can be wasted in taking corrective measures, resulting in increased cost and decreased throughput.

Additionally, the need arises for fast set-up (i.e., cure) times for the reactive systems. When applied to mine bolt installation, production capacity of a continuous mining machine is dependent on the speed in which the roof bolt

operator is able to secure the mine roof. Thus, productivity can be increased significantly if the reactive system set-up time can be increased.

SUMMARY OF THE INVENTION Accordingly, a major object of the present invention is the provision of a novel rock bolt anchoring system, which minimizes leakage during storage and use, which facilitates installation of a reinforcing member and which is exceptionally fast in as well as strong upon curing.

It is a further object of the present invention to provide a container which holds the components of the rock bolt anchoring system.

It is a further object of the present invention to provide a method of using the novel rock bolt anchoring system in anchoring a reinforcement member, such as a mine bolt.

Briefly, the present invention features a novel rock bolt anchoring system.

The system comprises:(a) a resin component, comprising an unsaturated polyester resin; and (b) a cross-linking catalyst component separated from the resin component. The catalyst component comprises a catalyst effective to cross-link the polyester resin, a filler and a propylene glycol. In the catalyst component, the catalyst is present in an amount from about 1 to 24 wt%, the filler is present in an amount from about 48 to 90 wt% and the propylene glycol is present in an amount from about 1 to 15 wt%, based on the catalyst component.

In particular, for a number 5 rebar, the system preferably has an average stall time over ten runs of less than about 16 seconds, an average tonnage at 0.100 inch displacement over ten runs of greater than about 9.0 tons and an average yield point over five runs of greater than about 12.5 tons.

The present invention also features a container in which the rock bolt anchoring system is contained. The container comprises a plurality of

compartments for separately containing the resin component and the cross-linking catalyst component of the system.

Lastly, this invention features a method of using the novel rock bolt anchoring system in anchoring a reinforcement member in an opening. The method comprises separately introducing the resin component and the cross-linking catalyst component into the opening, and inserting the reinforcing member into the opening, thereby causing the resin formulation and the cross-linking catalyst formulation to become mixed together and cured around the reinforcing member.

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiments thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION It has now surprisingly and unexpectedly been found that when used with a two-component reactive system, a cross-linking catalyst component which contains a propylene glycol provides several advantages over prior art systems.

For example, the inventive reactive system has been found to prevent or minimize leakage after installation of a reinforcement member. The novel reactive system also facilitates installation of a reinforcing member and very effectively fixes the reinforcing member as a result of the exceptional strength of the system upon curing.

A particularly surprising and unexpected benefit of the reactive system according to the invention was discovered during mine bolt installation. During bolt spinning, it was found that a "stall" could be detected in the installation equipment in a relatively short time when using the inventive system with conventional installation procedures. Such stalls are marked by laboring of the installation equipment, and indicate the proper point at which bolt spinning should be terminated by operators.

The first component of the reactive system is a resin component. The resin used is an unsaturated polyester resin, with isothalic, orthothalic and terephthalic resins being preferred. Suitable resins are well understood by persons skilled in the art and can be formed, for example, from monomers such as styrene, vinyl toluene, methyl methacrylate, or mixture thereof. The polyester resin is preferably present in an amount from about 5 to 24 wt%, more preferably from about 8 to 12 wt%, based on the resin component.

Unsaturated polyester resins may be made by reacting dicarboxylic acids with glycols, using a polycondensation reaction. This process may be carried out in a stainless steel reactor at temperatures of about 410OF. Water is a byproduct of the reaction, and is removed by distillation during the reaction. When the reaction is complete, the resulting polyester is blended with styrene monomer.

Inhibitors are added to provide shelf life and to adjust gel time. In prepromoted resins, various promoters, such as cobalt and dimethylaniline are added to provide room temperature curing capabilities with MEKP (methyl ethyl ketone peroxide) or BPO (benzoyl peroxide).

A suitable polyester resin for purposes of the invention may be prepared by reacting 60 moles of orthophthalic anhydride and 40 moles of maleic anhydride with 110 moles of propylene glycol. For a 100 pound batch, this translates to 34 pounds of orthophthalic anhydride, 15 pounds of maleic anhydride, and 110 pounds of propylene glycol. As a byproduct, 7 pounds of water will distill off.

This reaction mixture is reacted to an acid number of about 30, and then thinned with styrene monomer and cooled to room temperature. Inhibitors, such as hydroquinone, promoters and other additives are added, and the resulting polyester resin is packaged into drums or other appropriate containers.

Alternatively, polyester resins commercially available such as Polylite 32 327-10 polyester resin (available from Deichhold Chemicals, Inc.) may be used.

Preferred polyester resins will meet the following specifications:

1. Total non-volatiles (minimum weight percent) . . 61-65% 2. Water (maximum allowed) . . 0.15% 3. Acid number of dissolved resin . . 8 to 15 4. Gel time per QP 4 1.0 (seconds) . . 11 to 14 5. Thixotropic Index (#3 Spindle-l/lO rpm) . 2 to 3.5 6. Viscosity per QP4 3.0 (centipoise) . 2000 to 3500 7. Minimum Uncatalyzed Stability C? 123"C (hours) . 4.8 8. Viscosity stability After Being @ 71"C (days) . . 5 One or more inorganic fillers are also present in the polyester resin component in an amount from about 48 to 90 wt%, preferably from about 80 to 87 wt%, based on the resin component. Suitable fillers must be substantially inert to the other components of the system and include, for example, various forms of calcium carbonate, preferably limestone.

Other components can optionally be present in the polyester resin component. For example, an additional amount of the monomer or monomers which form the polyester resin can be added in an additional amount up to about 15 wt%, preferably from about 1.5 to 4 wt%, based on the resin component. This additional monomer can be called a "reactive diluent," in that it acts both as a diluent for the resin component and initiates the cross-linking reaction. The additional monomer is preferably styrene monomer.

One or more other diluents can also be added to the resin component.

Suitable such diluents include, for example, glycols such as ethylene glycol, diethylene glycol, etc. These diluents can be present in an amount of up to about 18 wt%, preferably from about 1 to 3 wt%, based on the resin component. In addition to acting as a diluent these materials provide internal lubrication and act as an antifreeze for exposure to extreme cold.

Various promoters can also be present in the polyester resin component, examples of which include diethanolamine (DEA), dimethylamine (DMA) and

dimethyl-paratoluidine (DMPT). These promoters can be present in an amount up to about 2 wt %, preferably from about 0.1 to 1 wt %, based on the resin component.

Additionally, one or more colorants can be added to the resin component in an amount up to about 2 wt%, preferably from about 0.1 to 1 wt%, based on the resin component. Suitable colorants include, for example, carbon black and coal dust.

The resin component can further include inhibitors, such as benzoquinone, naphthoquinone and hydroquinone. These inhibitors can be present in an amount up to about 2 wt%, preferably from about 0.1 to 1 wt%, based on the resin component.

Other fillers can be added as needed for enhancement of properties such as, for example, penetrability, viscosity, internal lubrication and general flowability.

Such fillers include, for example, talc, dolomite and mica. These fillers can be present in an amount up to about 30 wt%, preferably from about 5 to 15 wt%, based on the resin component.

The second component of the reactive system is a cross-linking catalyst component. The catalyst component is preferably ether free, and contains a catalyst which promotes cross-linking and curing of the polyester resin when the two are mixed together. The catalyst is present in the catalyst component as a paste in an amount from about 1 to 24 wt%, preferably from about 4 to 14 wt%, based on the catalyst component. Suitable catalysts include organic peroxide compounds such as, for example, dibenzoyl peroxide.

The catalyst component further includes one or more solid fillers for the enhancement of penetrability, viscosity, internal lubrication and general flowability. The filler is present in the catalyst component in an amount from about 48 to 90 wt%, preferably from about 62 to 75 wt%, based on the catalyst

component. The filler is typically a form of calcium carbonate, preferably limestone.

Because of the relatively viscous nature of the catalyst, use of viscosity modifiers is necessary to ensure good flowability of the catalyst and to promote mixing with the resin component. It has been found that use of a propylene glycol provides particularly beneficial results. Thus, the viscosity modifier contains a propylene glycol. Suitable propylene glycols for use in the catalyst component include, for example, propylene glycol, dipropylene glycol and tripropylene glycol. Of these, dipropylene glycol is particularly preferred. The propylene glycol is present in an amount from about 1 to 15 wt%, preferably from about 6 to 10 wt%, based on the catalyst component.

The viscosity modifier preferably contains mineral oil and/or water. The mineral oil can be present in an amount from about 0.1 to 18 wt%, preferably from about 1 to 4 wt%, based on the catalyst component.

Water can be present in the catalyst component in an amount from about 1 to 18 wt%, preferably from about 8 to 12 wt%, based on the catalyst component.

It is particularly preferred that deionized water be used.

The catalyst component can optionally include additional components, such as surfactants and emulsifiers. Such additional components can be present in the catalyst component in an amount up to about 5 wt%, preferably from about 0.5 to 2 wt%, based on the catalyst component.

The resin component and catalyst component may be used in proportions typically used by those skilled in the art. Generally, however, the weight ratio of resin component to catalyst component is preferably in a range of from about 5 to 15, and more preferably in a range of from about 8 to 12. Of course, the conditions of the formation to be stabilized will affect how much of each component to utilize.

The following examples describe in detail various embodiments of the invention, as well as comparative examples. It will be apparent to those skilled in the art that modifications may be practiced without departing from the purpose and intent of this disclosure. Further, the following examples should in no way be considered as limiting the scope of the claimed invention.

EXAMPLES 1. Preparation of resin component 9.8 grams of styrene monomer, 16.4 grams of diethylene glycol (DEG), 55.8 grams of polyester resin meeting the specifications described above, 1.2 grams of dimethyl-paratoluidine (DMPT) and 0.7 grams of Color Black were poured into a 16 oz. glass jar and mixed with a Dispermat mixer at 1500 to 2000 rpm for 3 to 4 minutes using a 1.5 inch three blade propeller. Using a small spatula, small amounts of limestone filler were added to the mixture in a total amount of 516. 1 grams while mixing. Mixing was continued until a uniform and complete dispersion was obtained.

2. Preparation of dipropylene glycol-contamlng catalyst component (Catalyst Component A) 3.2 grams of mineral oil were poured into a 9 oz. glass jar. 23.4 grams of dipropylene glycol (DPG) were then added to the mineral oil. Mixing was performed at 1500 to 2000 rpm in a Dispermat mixer for 3 to 4 minutes using a 1.5 inch high-shear impeller blade. 35.4 grams of 55% BPO paste were added to the mixture, and mixing was performed for an additional 3 to 4 minutes at the same speed. 31.1 grams of deionized water were slowly added to the mixture while mixing. Using a small spatula, small amounts of filler in a total amount of 206.9 grams were added to the mixture while mixing. Mixing was continued until a uniform and complete dispersion was obtained.

3. Preparation of glycol-free catalyst component (Catalyst Component 27.3 grams of mineral oil were poured into a 9 oz. glass jar. 35.4 grams of 55 % benzoyl peroxide (BPO) paste were next added to the mineral oil. The mixture was mixed at 1500 to 2000 rpm in a Dispermat mixer using a 1.5 inch high-shear impeller blade for 3 to 4 minutes. To the mixture, 26.1 grams of deionized water were slowly added while mixing. Using a small spatula, small amounts of filler were added in a total amount of 192.3 grams while mixing.

Mixing was continued until a uniform and complete dispersion was obtained.

4. Capsule Preparation A 12-inch length of 4 1/4 inch Mylar film having a thickness of 2 mil was cut and placed on an electronic balance. Along one edge of the film, a similar length of 3/4" transparent tape was overlapped. The scale was tared. Small quantities of the resin compound were placed along the length of the film, near the edge and away from the tape. The material was evenly distributed along the film to a total of 212 grams. The film was lifted along the compound edge and carefully rolled one time, thereby enclosing the compound inside the film and leaving a portion of the film and the tape flat and unrolled. Along this remaining edge, the catalyst was evenly distributed to a total of 24 grams. The edge with the tape was lifted, folded over the roll of compound and sealed along the length of the film, thereby forming an open-ended capsule. The material in the film was fully enclosed by crimping each end of the film and securing the ends with a small piece of the same tape.

Insertion or Installatlon Testing of the mine bolt resin systems was performed on a solid limestone block, measuring 45 inches long, by 30 inches wide, by 15 inches deep. The

intent was to approximate an actual in situ application of the product. One inch diameter, twelve inch deep holes were drilled into the block. A 5/8 inch diameter bolt was used in a one inch hole. The length of the test bolts was 15 inches from the bottom of the head to the end. An 11-inch section of a 22 mm capsule was required to completely fill the annulus between the bolt and the hole wall. The capsule section was then placed into the hole, and the bolt was placed into the hole resting on the capsule. A 1/2 horsepower hand-held drill adapted with a chuck to fit the bolt head was then placed on the bolt head. With maximum downward pressure, the operator started the drill, spinning the bolt and forcing it through the resin to the bottom of the hole.

Evaluation of Strength of Rock Bolt Anchoring Systems The strengths of the cured rock bolt anchoring systems described above were evaluated by measuring displacement and yield point.

Displacement, measured in thousandths of an inch, is an indicator of the strength of the cured resin. A lower displacement is especially beneficial, since that measurement represents the extent of movement of a grouted system installed for the purpose of preventing such movement. Yield point, measured in tons, is the force at which the anchoring ability of a resin secured bolt is overcome.

Displacement and yield point measurements were accomplished by pull tests using a standard hollow centered Dyna-Pak 20 or 30 ton hydraulic ram and a limestone block. After the bolt was installed and adequate time was given for the resin to properly cure, usually 5 to 20 minutes, depending on resin speed, a pull test was performed. To perform the pull test, the hydraulic ram was attached to the bolt which was inserted into a one inch hole in the above-described limestone block, preloaded to one ton and the dial zeroed. Then, the hydraulic ram was pumped until the pump gage read two tons. The displacement is a reading on the dial indicator recorded in thousandths of an inch. This step was repeated,

increasing the load by one ton increments and recording the displacement at each ton. The yield point was recorded as the maximum load which the cured system was able to support without system failure, or the maximum load prior to the system giving way at the interface between the system and the hole wall.

The average tonnage at 0.100 inch displacement, measured over five pull tests as described above, is the total load in tons which creates a displacement of 0.100 inch in the anchoring system.

The average tonnage at 0.100 inch displacement is preferably greater than 9.0 tons, and more preferably greater than 9.5 tons.

The average yield point was determined over five pull tests as described above. The average yield point is preferably greater than 12.5 tons, and more preferably greater than 13.0 tons.

Comparative Examples 1-5 Capsules containing Catalyst Component B and the resin component were prepared as described above. The results of the pull tests are provided below in Table 1A, with displacement being shown in inches.

TABLE 1A Strength Evaluation of Rock Bolt Anchoring Systems Of Comparative Examples 1-5 Usmg Pull Test Comp. Comp. Comp. Comp. Comp. #5 Rebar Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 2 Tons .016 .010 .011 .007 .010 3 .027 .016 .020 .013 .017 4 .039 .024 .027 .022 .029 5 .062 .031 .036 .031 .043 6 .086 .039 .047 .040 .058

Comp. Comp. Comp. Comp. Comp. #5 Rebar Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 7 .120 .049 .061 .053 .082 8 .189 .062 .077 .071 .110 9 .255 .076 .094 .094 .151 10 .320 .095 .119 .120 .188 11 .422 .157 .211 .233 .268 12 .242 .373 .358 13 .346 .470 14 15 Yield Point-Based 11 13 12 11 13 on Max Ave Yield Point 12.0 Tonnage at 0.100 6.5 10.0 9.0 9.0 7.5 Disp. Ave. Tonnage at 8.4 0.100 Disp.

Examples 1-5 Capsules containing Catalyst Component A and the resin component were prepared as described above. The results of the pull tests are provided below in Table 1B.

TABLE 1B Strength Evaluation of Rock Bolt Anchoring Systems Of Examples 1-5 Using Pull Test #5 Rebar Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 2 Tons .008 .011 .009 .016 .008 3 .015 .018 .016 .027 .016 4 .022 .025 .024 .039 .025 5 .027 .033 .029 .051 .033 6 .032 .040 .036 .069 .043 7 .039 .049 .042 .087 .055 8 .045 .063 .050 .111 .068 9 .052 .078 .060 .154 .083 10 .062 .097 .073 .220 .105 11 .107 .167 .113 .338 .165 12 .170 .250 .171 .245 13 .225 .361 .237 .321 14 .316 .320 .415 15 .435 .420 Yield Point-Based 15 13 15 11 14 on Max Ave Yield Point 13.6 Tonnage at 0.100 11.0 10.0 10.5 7.5 10.0 Disp. Ave. Tonnage at 9.8 0.100 Disp.

As illustrated above in Tables 1A and 1B, the average value of the yield point and displacement of the Examples employing dipropylene glycol (Examples

1-5) showed a marked improvement over the Comparative Examples employing no dipropylene glycol (Comparative Examples 1-5). In particular, the average yield point for the inventive anchoring system was 13.6 tons, while that of the systems using no dipropylene glycol was only 12.0 tons.

Moreover, the average tonnage at 0.100 displacement for the anchoring system according to the invention was 9.8 tons, while that for the Comparative Examples was only 8.4 tons.

Evaluation of Stall of Rock Bolt Anchoring System The stall of the anchoring system is a measure of the time it takes the system to set up/cure. A fast stall is especially beneficial, since that measurement is directly related to the speed in which the rock bolts can be installed. In other words, greater productivity is possible with lower stall times.

Stall time was measured on a limestone test block as the total time from the beginning of spin and insertion of the bolt into a test hole until the time at which the insertion device was brought to a complete stop. The insertion device was a 1/2 hp drill. Because a great deal of torque and the countering resistance to torque develops when the resin begins to cure, it becomes very difficult to hold the drill chuck on the bolt head. Therefore, a maximum of downward force and grip to keep the drill from turning is applied until complete stall is reached. At the instant the drill stopped, the operator noted the time, to the nearest half second, and immediately released the drill trigger. The stall time was then recorded.

The average stall time was determined over ten stall time measurements as described above. The average stall time is preferably less than 16.0 seconds, and more preferably less than 14 seconds.

The measure of stall was performed on the anchoring systems described in Comparative Examples 6-15 and Examples 6-15. Tests were performed on limestone blocks using #5 rebar.

Comparative Examples 6-15 Capsules containing a rock bolt anchoring system were prepared according to the procedure described in Comparative Examples 1-5. Stall time was evaluated as described above.

Examples 6-15 Capsules containing a rock bolt anchoring system were prepared according to the procedure described in Examples 1-5. Stall time was evaluated as described above. The results of the stall evaluation are set forth below in Table 2.

TABLE 2 Stall Evaluation of Rock Bolt Anchoring Systems Using Block Test Comp. Ex. 6-15 Ex. 6-15 Rebar 22 12 #5 15 11.5 #5 18 14 #5 18.5 18 #5 Stall 15 15 #5 (sec) 24 10.5 #5 14 11 #5 17 12 #5 14.5 16 #5 21.5 17.5 #5 Ave. (sec) 18.0 13.8 #5

As can be seen from Table 2, the average stall time for the comparative catalyst formulation was 18.0 seconds. In stark contrast, the propylene glycol- containing catalyst formulation according to the invention resulted in a significantly lower average stall time of 13.8 seconds. Consequently, the resulting rock bolt installation speed when using the inventive system can be significantly higher than when using the system of the Comparative Examples.

While the invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made, and equivalents employed, without departing from the scope of the appended claims.