AU2011297666B2

AU2011297666B2 - Liquid composition for the cold repair of rubber products and industrial coatings, method for obtaining said composition, and use thereof

Info

Publication number: AU2011297666B2
Application number: AU2011297666A
Authority: AU
Inventors: Eduardo Bernier Richter; Francisco Picon Bernier; Marco Picon Bernier
Original assignee: Bertech Panama S A
Current assignee: Bertech Panama SA
Priority date: 2010-09-01
Filing date: 2011-08-30
Publication date: 2014-07-17
Anticipated expiration: 2031-08-30
Also published as: AU2011297666A1; WO2012029029A2; WO2012029029A3; CO6801661A2; BR112012016629B1; BR112012016629A2; PE20131501A1

Abstract

The invention relates to a liquid composition for the restoration and recovery of worn surfaces of natural or synthetic rubber, or as a conservative against oxidation or other corrosive agents having a liquid consistency at room temperature and physical durability properties similar to those of polyurethane. Said composition consists of a base composition comprising polyurethane prepolymer, a solvent and a pigment; and a catalyst. The invention also relates to a method for producing said composition and to the use of same for the rapid and definitive cold repair of rubber conveyor belts for fabric or steel cables, for the recovery of driven pulleys, and damage to belts, for the preparation of moulded parts, for the repair of conveyor belts in an inclined position and for the sealing of joints of concrete blocks.

Description

1 LIQUID COMPOSITION FOR PREPARING RUBBER PRODUCTS AND INDUSTRIAL COATINGS IN COLD, METHOD AND USE THEREOF SPECIFICATION The present invention is related with a chemical composition to be used in reconstitution and recovery of worn rubber surfaces, either of organic or synthetic origin, as well as its use as preservative against oxidation or other corrosive agents. The composition consists on a mixture comprising a crosslinkable polyurethane pre polymer based on a toluene diisocianate (TDI) in a ratio between 74 to 87% in weight of the final composition, a solvent selected among ethyl acetate, acetone, 4 methylpentanone, cyclohexanone, benzene, 1,4-dioxane, methyl-ethylketone, acetic acid, tetrahydrofurane, dimethylacetamide, trichloromethane, decahydronaphtalene (decalin), dimethylformamide, heptane, diisopropyl ether, ethanol, xylol, cyclohexane, or mixtures thereof in a ratio between 0.1% to 23%, a dye between 0.1 and 5% and a diethylmethylbenzenodiamine (DETDA) catalyst. This composition has the characteristic that can be applied on cold over the surface of rubber and general industry coatings. BACKGROUND OF THE INVENTION Starting from a prior art analysis, it can be confirmed that there are polyurethane chemical compositions or resins for covering surfaces on cold, used for pre-constitution or recovery of worn rubber surfaces of natural origin. Such resins, have also application as preservative against oxidation and other corrosive agents. For example, in the case of repairing conveyor belts, usually bonding clamps, pasty resins of temporary patches, in-cold vulcanization, hot vulcanization and changing of the belts are the methods used. Currently, there are resins that can be used in the same way that the resin of the present invention, nevertheless, they differ in their composition, which includes a plastifier, diminishing the physical properties of polyurethane, which is the basic component of the formulation, and further, the plastifier produces the solidification of the resin at room temperature (around 20 0 C) after 7 days from fabrication, thus forcing the user to heat the composition for 2 returning it to its liquid state, and thus allow application, which is time consuming and does not warrant that the reached consistency is proper for the use of the composition. Other existing alternative for this type of repairing, consists on performing classical methods for the application of polyurethane, which requires heating polyurethane in drums, for further application with the use of some kind of tool. Said procedure is not used in general, since it requires the use of huge machinery and a lot of preparation time, thus turning it an unworkable process in the field, and, contrary to the present invention, this alternative does not allow mobility. For the case of industrial coatings, there are innumerable kinds of existing coatings in the market, but they vary in function of the needs to which they are directed to. For example, the US patent N*5,688,892, describes a process for producing a waterproof polyurethane curable coating for in-cold fixation. The pre polymer and isocianate composition comprises the product of reaction between toluene diisocianate (TDI) and a polyoxypropylene polyol and/or polyoxyethyl propylene polyol, mixed in situ with a curing agent containing a crosslinkable aromatic polyamine of diethyltoluenediamine and a plastifier. As can be appreciated, the invention described in this prior art document has the disadvantage of using a plastifier, which, as previously explained, decreases the physical properties of the basic component of the formulation and furthermore, promotes solidification of resin at low temperatures, therefore it does not remain in liquid state for time periods suitable for easing the application of the composition. On the other hand, the chilean patent application CL 3279-2007, describes a preparation useful for pre-constitution or recovery of worn rubber surfaces of natural origin, comprising a crosslinkable polyurethane polymer or diphenylmethane diisocianate mixed with a plastifier diethyleneglycol dibenzoate in a ratio lower than 20% and catalyzed by diethylmethylbenzenodiamine. Nevertheless, the composition uses toluene and plastifier, the product is not in liquid form, limiting its action field. The product disclosed in the application CL3279-2007 requires heating as a previous step to application and the curing time is 4 times higher compared to the resin of the present invention, which is inconvenient since it requires additional time for preparing the composition and requires longer waiting times before using the equipment after 3 reparation. As confirmed by the prior art review, the known compositions present disadvantages when using a plastifier altering the physical properties of the coating, in particular, decreasing significantly the hardness of the polyurethane and, on the other hand, it does not have a liquid consistency at room temperature. Therefore, currently there are no compositions for reconstitution and recovery of worn rubber surfaces of natural or synthetic origin, and useful as preservative against oxidation or other corrosive agents, which are economic, easy to prepare and apply, not requiring specialized personal for its application. The present invention corresponds to a composition for reconstitution an recovery of worn rubber surfaces of natural or synthetic origin, or as a preservative against oxidation or other corrosive agents, of liquid consistency at room temperature and with physical properties similar to polyurethane consisting of a crosslinkable polyurethane pre-polymer and toluene diisocianate (TDI), a solvent selected among ethyl acetate, acetone, 4-methylpentanone (MP), cyclohexanone, benzene, 1,4 dioxane, methyl-ethylketone (MEK), acetic acid, tetrahydrofurane (THF), dimethylacetamide, trichloromethane, decalin, dimethylformamide (DMF), heptane, diisopropyl ether (DIPE), ethanol, xylol, cyclohexane (CYH), or mixtures thereof a diethylmethylbenzenodiamine (DETDA) catalyst. The composition allows efficient and durable reparations, with an easier and simpler application, with the additional advantage of having a lower cost for the end consumer. The physical characteristics reached by the composition after reparation comply with desired characteristics for end use of the composition, such as hardness, shear resistance, flexibility, adherence and resistance to impact and abrasion. According to a first aspect of the present invention there is provided a composition for reconstitution and recovery of worn rubber surfaces of natural or synthetic origin, wherein the composition has a liquid consistency at room temperature and physical properties of durability similar to polyurethane, consisting of: a) one base composition comprising: (i) 74 to 87% of a polyurethane pre-polymer; (ii) 0.1 to 23% of solvent; (iii) 0.1 to 5% dye suitable for using in compositions containing polyurethane; and b) a catalyst. According to a second aspect of the present invention there is provided use of a composition according to the first aspect of the invention, wherein the 4 composition is used for the quick and definitive, in-cold, reparation of rubber fabric or steel cables conveyor belts, in recovery of pulleys, damages on any type of belts, manufacture of mold pieces, repairing conveyor belts in inclined locations and for the sealing of concrete blocks joints. According to a third aspect of the present invention there is provided a method for preparing the composition according to the first aspect of the invention, wherein the method comprises the following steps, using the amounts of polyurethane pre-polymer, solvent and dye according to the desired formula: a) prepare the base composition comprising: (i) heating polyurethane pre-polymer at a temperature of 80*C (±50C), according to the ranges indicated for the compounds, for a period between 1 to 8 hours, or until the pre-polymer is in liquid state; (ii) adding the solvent and dye to the mixture obtained in (i) agitating until a uniform mixture is obtained, thus producing the base composition; and b) adding the catalyst, which has been packaged separately in the exact amount to react the base composition. DETAILED DESCRIPTION OF THE INVENTION The composition (resin) disclosed in the present invention consists on a base mixture of: a crosslinkable polyurethane pre-polymer in base of toluene diisocianate, a solvent and a dye and subsequently, a diethymethylbenzenodiamine catalyst is added to this base mixture, finally forming the composition of the present invention, consisting of: a) a base composition comrprising: (i) 74 to 87% polyurethane pre-polymer; (ii) 0.1 to 23% solvent; (iii) 0.1 to 5% of a suitable dye for use in compositions comprising polyurethane; and (b) a catalyst. In particular, the composition of the present invention has a liquid or pasty consistency, which is achieved by varying the solvent percentages in the composition. It is possible to maintain the fluidity of the composition in a permanent 5 manner if the room temperature is maintained (above 10 C) as can be seen in Table 1. The advantageous effects of the present invention, can be evaluated through technical comparisons and also through physical properties of the composition, wherein the composition has demonstrated, mainly, having longer durability, break resistance, higher adherence, better texture and lower curing times. The composition stands out among existing solutions, since it does not include a plastifier among its components, it does not require obligatory toluene in its composition and can be used directly, without heating. Also, while being in liquid state, can be used for filling spaces in structures where its application is possible, such as for example, in the case of junctions between structures. The following table is obtained as a technical comparison among existing products comprising plastifiers in the current state of the art, and the composition of the present invention. It is worth noting that the liquid state of the present composition is achieved at temperatures around 100C, nevertheless, when the temperatures are lower than 50C, the liquid state duration is 7 days. Table 1: Technical comparison between the composition of the present invention and a commercial product comprising plastifier. Duration of Duration of Duration in Curing reparation of reparation of Time of time liui sa high impact moderate impact application belts belts With 60 min 1 week 0.5 months 6 meses 90 min plastifier Without plastifier 15 min permanent 6 months 12 meses 20 min When comparing the physical properties of the composition mixed with the solvent or solvents found versus the properties of a product mixed with a plastifier, considering as a reference a polyurethane pre-polymer of 85±5 shore hardness, the following is obtained: 6 Table 2: Typical properties of the composition without plastifier Characteristic State or Value Appearance a 240 C liquid Appearance a 10* C liquid Appearance a 5* C liquid * Appearance a 0* C liquid * Hardness 85 ±5 shore A Module 100% psi 1500 Module 300% psi 1950 Tensile strength psi 6500 Elongation % 450 Shear resistance-D470-PLI 130 Shear resistance -DIECV-PLI 850 Rebound % 42 *Notes that this is a property expected for 7 days. Table 3 shows the results of the properties of existing compositions which use plastifier.

7 Table 3: Typical properties of the composition with plastifier Characteristic State or Value Appearance a 24* C liquid Appearance a 10* C liquid* Appearance a 5* C Solid Appearance a 0* C solid Hardness 75 ±5 shore A Module 100% psi 1200 Module 300% psi 1560 Tensile strength psi 5200 Elongation % 360 Shear resistance-D470-PLI 104 Shear resistance -DIECV-PLI 680 Rebound % 50 *Notes that this is a property expected for 7 days. To select the best solvent or mixture thereof, different polyurethane solubility assays were tried for 20 different types of solvents. In general, the solubility of polyurethane is high in the majority of the solvents chosen for this study, with the exception of acetic acid and heptane; being insoluble in the last one. Among the solvents showing a good dissolution of polyurethane, only differences in the viscosity of the final product were observed, which can be associated with differences in the capacity of the solvent to dissolve more properly the polymer. Considering the viscosity of other solvents, such as for example, toluene, solvents allowing a polyurethane solution with equal or lower viscosity than the one obtained with toluene are observed. Among these are: ethyl acetate, acetone, 4-methylpentanone, cyclohexanone, benzene, 1,4-dioxane, methyl-ethylketone, acetic acid, tetrahydrofurane, dimethylacetamide, trichloromethane, decalin, dimethyiformamide, heptane, diisopropylether, ethanol, xylol and cyclohexane. The good dissolution capacity shown by the selected solvents must be 8 compatibilized with its capacity for evaporation in a proper time. The evaporation rate obtained in experiments is shown in Figure 1. Considering as a reference the toluene evaporation rate (12mg/30 min), it can be established that some of the solvents with closest rates are: 4-methylpentanone (8.4 mg/ 30 min), ethanol (20.7 mg/ 30 min) and 1.4-dioxane (10.9 mg/ 30 min). Due to the fact that polyurethane solubility in ethanol is not suitable, and considering the potential health hazards produced by dioxane, the solvent 4-methylpentanone (methyl isobutyl ketone, MIBK) is presented as a promisory alternative for use as polyurethane solvent. Methyl ethylketone is also a good solvent for polyurethane, nevertheless, its high volatility (evaporation rate) could represent a disadvantage considering the effects of its exposition and the end quality of the adhesive. The toluene is considered as a reference for evaluation of other solvents, but it is not used in the composition of the present invention, since it is categorized as an organic contaminant. In order to obtain a solvent complying with higher precission the desired evaporation time, some solvent mixtures were studied. The evaporation rates of solvent mixtures in a ratio 4:1 are shown in Figure 2, and the optimization of the composition for the mixture 4-methylpentanone (MP):Tetrahydrofurane (THF). Addition of THF to dimethylformamide (DMF) produces a drastic increase in the evaporation rate, the same occurs when diisopropyl ether (DIPE) and cyclohexane (CYH) are added to MP. Nevertheless, a rigorous control of the composition of the mixture MP:THF allows obtaining a mixture with a desired evaporation rate for use of the composition. The optimal composition for solvent mixture was 95.75% 4 methylpentanone and 4.25% tetrahydrofurane (22.5 MP:1 THF), with an evaporation rate of 12.9 mg/30 min. Considering the abovementioned results, the solvents 4-methylpentanone as well as the optimized mixture of MP:THF, were used in the hardening process of polyurethane in presence of the catalyst agent. The results demonstrated that the preparation based on MP as well as the optimized mixture MP:THF show characteristics similar to the ones obtained using toluene as solvent. On the other hand, the solvent methyl-ethylketone also was evaluated in the hardening process. Although methyl-ethylketone allows apparently obtaining a product with similar 9 characteristics, the risks involved in the manipulation of this highly volatile solvent, turn it less suitable for preparation of the adhesive. In the following section different tables with the economical comparison of a resin using plastifier versus the composition corresponding to the present invention are shown. For each comparison, the most costly alternative of the studied solvents was considered, in this case, the mixture MP:THF. For the fabrication of 650 g of resin, the end prices for each product are shown in Tables 4 and 5. Table 4: Resin with plastifier Material Amount (gr) Price (US$) Polyurethane 520.00 4.86 Plastifier (Diethylenglycol Dibenzoate) 104.00 1.00 Dye 26.00 0.30 TOTAL: 650.00 6.16 Tabla 5: Resina sin plastificante, de acuerdo a la invenci6n Material Amount (gr) Price (US$) Polyurethane 565.20 5.28 Solvent (MIBK:THF) 56.52 0.21 Dye 28.26 0.32 TOTAL: 670.00 5.81 Considering that the costs of dyes are similar, in spite of the cost of the polyurethane pre-polymer, which is higher, the final price of the composition of the invention is a better option at a lower cost for the consumer. For a better handling of the composition of the present invention, the composition can be packaged in a high density polyethylene (HDPE) container with an easy opening cap and an inviolability seal. Using a container of these characteristics, the composition is better maintained when isolated from low temperatures. Using a plastic container also allows heating of the content, even in a microwave, in case that the resin is hardened at low temperatures (unlike the majority 10 of similar products packaged in metallic containers). The problem with metallic containers, is that, in the case that the resin is hardened, the only way of heating is placing the container near a source of a flame, such as a blowtorch. This is generally not allowed in mine sites, since it represents a security risk. Using an easy opening cap with a membrane, in the case that the use of only half of the material is desired, it could be done with no problems. For the case of metallic containers, the cap is destroyed and the unused product for reparation, is lost. In the composition, the total percentage of solvent can vary in the range of 0.1 % to 23% in case that a more diluted or a pastier product is desired for different applications. Without the aim of limiting the present invention, following is a list of solvents that can be used, either alone or in combination thereof, among them there is ethyl acetate, acetone, 4-methylpentanone, cyclohexanone, benzene, 1,4-dioxane, methyl-ethylketone, acetic acid, tetrahydrofurane, dimethylacetamide, trichloromethane, decalin, dimethylformamide, heptane, diisopropyl ether, ethanol, xylol and cyclohexane, among the mixtures that can be used, a mixture of between 80 to 96% of 4-methylpentanone with 4 to 20% of tetrahydrofurane, or a mixture of 60 to 70% ethyl acetate with 30 to 40% of decane, or a mixture of between 60 to 70% ethyl acetate with 30 to 40% of 2,2,4-trimethylpentane. The composition includes a suitable dye for use in compositions containing polyurethane, such as for example, lampblack in a propylenglycol vehicle. This composition has the characteristic that can be applied on cold on a rubber surface and general industry coatings. The composition has a liquid or pasty consistency, characteristic which will depend on the percentages of solvent in the composition. This characteristic of the present composition is very useful in reparations wherein a higher speed in runoff of the product and a higher coverage of a surface is required before hardening due to the action of the catalyst. The present invention consists on a composition to be used in the reconstitution and repairing of worn rubber surfaces of natural or synthetic origin for reparation, isolation or protection against external agents, as well as its use as preservative against oxidation or other corrosive agents. Therefore, the invention has 11 application in the industry of rubber tires and belts. This composition can also be used for industrial coating over concrete, metals, rubber and polyurethane, it is highly functional in acid tank coatings, coatings of valves exposed to corrosive substances, coating and waterproofing of tailings in mine sites, among other uses. Also, the composition of the present invention can be used in quick and lasting reparations of truck tires, and quick preventive maintenances. The present invention has application in quick and definitive reparation, on cold, in rubber fabric or steel cables conveyor belts, in recovery of pulleys, and damages on any type of belts and manufacture of mold pieces, among others. It can also be very useful when it is desired that the product will not runoff easily due to the effect of gravity, for example, for the reparation of conveyor belts located at an inclined position. Other object of the present invention provides a method for preparing the composition, which is composed of a polyurethane pre-polymer based on toluene diisocianate, solvent and dye. The catalyst, diethylmethylbenzenodiamine (DETDA), is packaged separately and it is only added to the final composition before its application. The method comprises the following steps, using the polyurethane pre polymer, solvent and dye amounts according to the desired formulation: a) preparing the base composition comprising: (i) heating the polyurethane pre-polymer at a temperature of 800C (±50C), or according to the ranges indicated for the compound, for a period between 1 to 8 hours or until all the pre-polymer is in liquid state; (ii) add the solvent and dye to the mixture obtained in (i) using agitation until reaching a uniform mixture, thus obtaining the base composition; b) add the separately packaged catalyst, in an exact amount for reacting the base composition, according to Formula (1). Formula (1): Equivalent weight Ratio of (Pre -polymermassnx of curing agent J Cuing agent ) MassMof curinea geigt of - x%NCO -Molecular wihofcuring agent 12 Example 1: General composition A composition according to the present invention was prepared. 20 kg of polyurethane were mixed, an equivalent to 10% base weight of solvent was added (2 kg), and the equivalent to 5% of base weight of dye was added (1 kg). The polyurethane was heated at 800C (or according to the allowed specifications for the raw material used) and once in that state, it was mixed with the solvent. The polyurethane and solvent were mixed with agitation from 600 to 1,000 rpm during 10 minutes or until the mixture was homogeneous. The required catalyst for the composition to reach final properties, calculated according to Formula (1), as shown below, corresponded to 2.02 kg, if it is considered that the catalyst has an equivalent weight of 89.14 g/(-NH 2 valence groups). (Pre-polymermass)x Eginy ent weight x Massof ctuing agent = 4200 x %NCO A preferred embodiment, due to the consistency and broader application in the field of conveyor belts, is shown in Table 6, wherein the percentage of each compound is expressed in base to the total weight of the base composition. The catalyst required for this embodiment is packaged in function of Formula (1), and corresponds to 10.08% of the weight of the base composition if a 5% NCO pre polymer is used for a curing agent with an equivalent weight of 89.14g/(-NH 2 valence groups). Table 6: Weight percentage in relation to the total end of the composition. Compound % in weight of the base composition Polyurethane pre-polymer 86.96 Solvent 8.69 Dye 4.35 In a further preferred embodiment, such as the one used in the Example of the drive (check Example 5), a composition according to the ratios shown in Table 7 is used, wherein the percentage of each compound is expressed in base to the total weight of the base composition.

13 Table 7: Weight percentage in relation to the total end of the composition. Compound % in weight of the base composition Polyurethane pre-polymer 74.07 Solvent 22.22 Dye 3.70 In all the examples of application described below, it is required to scratch the worn surface with the objective to achieve a rough and porous surface, and then a primer must be applied (allowing the bonding of the resin to the surface). The primer to be used must be suitable according to the type of surface (rubber/polyurethane, concrete or metal). Example 2: Use in reparation of conveyor belts and application on general rubber surfaces Thanks to the fast curing time and the final characteristics reached by the composition of the present invention once catalyzed, it is very useful as a repairing agent for rubber surfaces, as the case of conveyor belts, generally used in mining, cement, electric, port, industries etc. In the case of mining industries, the conveyor belts are worn due to impact, abrasion or corrosion produced by the rocks on this surface, producing cuts and rips of great magnitude. These damages, depending on their magnitude, are repaired using bonding clamps, in-cold vulcanization, hot joints or definitive change of the belts. These solutions, apart from being costly, require many personnel and extended periods during which the plant is stopped, diminishing the productivity levels of mining sites, for example, a hot joint replacement requires nearly 12 persons, an average of 6 hours and huge vulcanization machinery. These failings can be more harmful if high impact belts in the beginning of a mineral transport line are affected, obligating generally to a complete halt in the plant. Thanks to the use of the composition of the present invention, the abovementioned problems are solved in a simple, fast way, with fewer personnel and at a significantly lower cost. For example, a belt with a groove or undermined; i.e., when the cut has pierced from one side to the other, can be repaired in less than 1 hour and using two persons without the requirement of heavy machinery.

14 Procedure for repairing: 1. Preparation of the surface: first, a straight drive provided with a wire brush must be applied in order to have a scraped and porous surface. Afterwards, any broken or protruding fragment of rubber (or other material) is removed from the surface to be repaired. Subsequently, the surface is cleaned with a brush or pressurized air and a cleaning solvent is applied. The surface should not have direct contact with the hands of the operator, or with any other objects after the reparation process, since this would affect the adhesion of the composition. 2. Application of the primer: the first rubber primer is poured (or the one corresponding to the surface to be repaired) over all the surface to be repaired and is spread with the help of a brush, in order to wet all the surface to be repaired with the material. 3. Preparation of the composition: The container containing the composition is opened and the amount of catalyst equivalent according to Formula (1) is added. Mix thoroughly until a completely homogeneous mixture is obtained. 4. Application of the composition: Once the primer is dry, the composition is applied, previously mixed with the catalyst, on the worn to be repaired. A spatula can be used to spread the composition according to need. After 20 minutes, the composition would be cured, and the reparation ended. For this example, the composition with the preferred formulation is used, considering the following concentrations: 86.96 polyurethane pre-polymer, 8.69% solvent and 4.35% dye and catalyst according to Formula (1). Example 3: Maintenance and recovery of mining truck tires: Generally in the industry, and in particular in mining, a great variety of large trucks are used for their operation. These trucks have a high demand in the industry, and are used in a continuous manner in mining processes. Also, these trucks circulate over rocky dirt roads, typical of geographic areas where mine plants are located. Therefore, truck tires suffer important damages, similar to knife cuts, in different parts of their surfaces, leaving the tire out-of-service. Thanks to the present invention, a way to recover damaged tires and prolonging their life can be achieved. Commonly, when tires suffer this type of damage, it is required to remove them from circulation, using heavy machinery and 15 transport them to a workshop specially conditioned for retread and recovery, which without question encompasses a decrease in productivity and long waiting times for returning trucks to operation, among many other disadvantages. With the present invention, a preventive maintenance can be made to the tires, without the need of removing them from the trucks, extending the life of tires and increasing the operational levels of trucks. In order to repair cuts, a special tool is used for scratching all its length and depth, and then pouring the composition in place waiting 30 minutes until hardening and definitive repair of the damage. Due to the fact that normally damages are narro and deep, it is preferred using a higher amount of solvent in the formula to produce a more liquid composition, and thus, allowing easier runoff. Generally, for this example are used the following concentrations in relation to the base composition: 76.92% polyurethane pre-polymer, 19.23% solvent and 3.85% dye, and catalyst according to Formula (1). Example 4: Use on coating of mine tailings joints The present invention has been used in sealing the joints of concrete blocks forming the mine tailing conduit. Some waste mine tailings are constructed based on the union of concrete structures which together form a large conduit through which the mine waste are evacuated. Said concrete structures are joined together through vertical "L-type" joints allowing the coupling of one structure with the next. Nevertheless, with changes in temperature, the concrete is contracted or expanded producing filtrations of material to the exterior of the conduit due to separation of the joining joints. This implies the payment from the mines of huge environmental fines each time the waste material is emptied on a land that has not been prepared to receive this type of material. Up until recently there was no definitive solution to said problem, since all available products in the market ended yielding or cracking in time, producing the re-appearance of filtrations. Therefore, the present invention solved this problem. Considering the dimensions of each joint (1.8 m), and that they are vertically placed, and that it was needed that the composition would runoff a long path before hardening, the solvent concentration was increased in the formula to achieve a less viscous solution, allowing runoff at a sufficient speed to cover all the desired area. In concrete, the 16 formula was modified using the following concentrations: 80% polyurethane pre polymer, 16% solvent and 4% dye, and the catalyst required according to Formula (). Example 5: Recovery of mold-pieces The present invention has been used in the recovery of molded rubber or polyurethane pieces. Such is the case of rubber drives of centrifuge pumps, which product of constant differences in pressure, and furthermore, if the liquid pumped is highly corrosive, the rubber coating shaping the helix of the drive is gradually detached producing a low efficiency in the performance of the centrifuge. To achieve the recovery of detached rubber pieces from the drive, a mold with the shape of the original piece is fabricated, which is adhered to the damages zone (for example, one of the tooth of the drive), and then the composition is poured inside, which by being liquid, accommodates due to gravity filling the mold. After the curing time has passed, corresponding to around 20 minutes, the mold is withdrawn and the drive is left with recovered rubber. For this example, the composition of the preferred formulation is used, in the following concentrations 74.08% polyurethane pre-polymer, 22.22% solvent and 3.7% dye, and the catalyst required according to Formula (1). Example 6: Use in guiding-wheels for tanks The composition was used in guiding wheels for army caterpillar tanks. The combat tanks move through a special dented belt, which is commonly called caterpillar. These caterpillars are in turn moved and guided by metal wheels coated with natural rubber. With regular operation of tanks in unpaved roads such as dirt roads, rocky roads, etc. these wheels suffer damage and loss the coating rubber, due to use and weight exerted by the caterpillar. Up until recently, these wheels could not be repaired, since there was no way to do it. The conventional repairing methods, such as retreading, damaged the original rubber parts which still covered the wheels, product of heating. When applying heat to the rubber, this melts and reaches a liquid state, wherein the new rubber (which would be used for repairing damages) melts with the original rubber in the wheels. Nevertheless, said procedure damages the original rubber in the wheel, 17 lowering their physical characteristics of hardness, flexibility, resistance, etc.; characteristics which are essential for the wheels to be operated in extreme conditions, in which military tanks are used. This problem was solved with the product according to the present invention, since it is applied in-cold and does not change the physical properties. Thanks to the physical characteristics that the product reaches after reparation (hardness, sheer resistance, flexibility, adherence), allows repairing damages in a simple, fast and effective manner. For this example, the composition is used in its preferred formulation, in the following concentrations: 83.34% polyurethane pre-polymer, 12.5% solvent and 4.16% dye and catalyst according to Formula (1).

Claims

1. A composition for reconstitution and recovery of worn rubber surfaces of natural or synthetic origin, wherein the composition has a liquid consistency at room temperature and physical properties of durability similar to polyurethane, consisting of: a) one base composition comprising: (i) 74 to 87% of a polyurethane pre-polymer; (ii) 0.1 to 23% of solvent; (iii) 0.1 to 5% dye suitable for using in compositions containing polyurethane; and b) a catalyst.

2. The composition according to claim 1, wherein the polyurethane pre polymer base of the composition is a crosslinkable polyurethane pre-polymer based on toluene diisocianate.

3. The composition according to claim 1 or 2, wherein the solvent is selected among ethyl acetate, acetone, 4-methylpentanone, cyclohexanone, 1,4-dioxane, methyl-ethylketone, acetic acid, tetrahydrofurane, dimethylacetamide, trichloromethane, decahydronaphtalene, dimethylformamide, heptane, diisopropyl ether, ethanol, cyclohexane, or mixtures thereof.

4. The composition according to claim 2, wherein the solvent corresponds to a mixture of 80 to 96% of 4-methylpentanone with 4 to 20% tetrahydrofurane.

5. The composition according to claim 2, wherein the solvent corresponds to a mixture between 60 to 70% ethyl acetate with 30 to 40% decane.

6. The composition according to claim 2, wherein the solvent corresponds to a 19 mixture between 60 to 70% ethyl acetate with 30 to 40% 2,2,4-trimethylpentane.

7. The composition according to any one of claims 1 to 6, wherein the catalyst is diethylmethylbenzenodiamine.

8. A composition for reconstitution and recovery of worn rubber surfaces of natural or synthetic origin as defined in claim 1 and substantially as herein described with reference to the Examples.

9. Use of a composition according to any one of claims 1 to 8, wherein the composition is used for the quick and definitive, in-cold, reparation of rubber fabric or steel cables conveyor belts, in recovery of pulleys, damages on any type of belts, manufacture of mold pieces, repairing conveyor belts in inclined locations and for the sealing of concrete blocks joints.

10. Use of a composition according to any one of claims 1 to 8, which use is defined in claim 9 and substantially as herein described with reference to the Examples.

11. A method for preparing the composition according to any one of claims 1 to 8, wherein the method comprises the following steps, using the amounts of polyurethane pre-polymer, solvent and dye according to the desired formula: a) prepare the base composition comprising: (i) heating polyurethane pre-polymer at a temperature of 800C (±5*C), according to the ranges indicated for the compounds, for a period between 1 to 8 hours, or until the pre-polymer is in liquid state; (ii) adding the solvent and dye to the mixture obtained in (i) agitating until a uniform mixture is obtained, thus producing the base composition; and b) adding the catalyst, which has been packaged separately in the exact amount to react the base composition. 20

12. A method for preparing the composition according to any one of claims 1 to 8, which method is defined in claim 11 and substantially as herein described with reference to the Examples. Servicios De Ingenieria Bertech Limitada Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON