MX2008007153A - Process for the preparation of sulphur cement or a sulphur cement-aggregate composite - Google Patents

Abstract

The present invention provides a process for the preparation of sulphur cement or a sulphur cement-aggregate composite comprising the following steps:(a) admixing at least an inorganic filler and/or aggregate and a polysulphide-containing organosilane having at least two organosilyl groups and allowing the organosilane to react with the inorganic filler and/or aggregate;(b) admixing during or after step (a) elemental sulphur with the inorganic filler and/or aggregate at a temperature at which sulphur is liquid to obtain an admixture comprising molten sulphur and inorganic filler and/or aggregate;and (c) solidifying the admixture to obtain sulphur cement or a sulphur cement-aggregate composite. The invention further provides sulphur cement or a sulphur cement-aggregate composite obtainable by such process and the use of a polysulphide-containing organosilane having at least two organosilyl groups as coupling agent in sulphur cement or a sulphur cement-aggregate composite.

Description

PROCESS FOR THE PREPARATION OF SULFUR CEMENT OR A MATERIAL COMPOSED OF AN AGGREGATE OF SULFUR CEMENT FIELD OF THE INVENTION The present invention provides a process for the preparation of sulfur cement or a composite material of a sulfur cement aggregate, the sulfur cement or the composite material of a sulfur cement aggregate can be obtained by such process and the use of an organosilane containing the polysulfide having at least two organosilyl groups as the agglutination agent in the sulfur cement or in the composite material of a sulfur cement aggregate. BACKGROUND OF THE INVENTION Sulfur cement generally refers to a product comprising at least sulfur, usually in an amount of at least 50% by weight, and a filler. Sulfur cement can be plasticized by the addition of a sulfur cement modifier in the sulfur cement preparation process. Such modifiers are already known in the art. Examples of such modifiers are aliphatic or aromatic polysulfides or compounds that form polysulfides during the reaction with the sulfur. Examples of the compounds that form the polysulfides are the naphthalene or olefinic compounds such as dicyclopentadiene, limonene or styrene. The modifiers are Ref. 193687 aggregates usually in an amount in the range from 0.1 to 10% by weight based on the weight of the sulfur. The usual sulfur cement fillers are a particulate inorganic material with an average particle size in the range from 0.1 μ to 0.1 mm. Examples of such sulfur cement fillers are fly ash, limestone, quartz, iron oxide, alumina, titania, graphite, gypsum, talc, mica or combinations thereof. The content of the sulfur cement filler can vary widely, but typically ranges from 5 to 80% by weight based on the total weight of the cement. The composite materials of the sulfur cement aggregate generally refer to a composite material comprising both the sulfur cement and the aggregate. Examples of the composite materials of the sulfur cement aggregate are sulfur mortar, sulfur concrete and asphalt spread with sulfur. The mortar comprises a fine aggregate, typically with particles having an average diameter between 0.1 and 5 mm, for example sand. The concrete comprises a coarse aggregate, typically with particles having an average diameter of between 5 and 40 mm, for example gravel or rock. The asphalt spread with sulfur is the asphalt, that is, typically an aggregate with a binder containing a filler and a residual hydrocarbon fraction, where a part of the binder has been replaced by sulfur, usually modified sulfur. The use of organosilane as a stabilizing agent in sulfur cement or in the compositions of sulfur cement aggregate to improve stability in water is already known. In US Pat. No. 4,164,428 for example, a plasticized sulfur composition comprising at least 50% by weight of sulfur, a sulfur plasticizer, a finely divided mineral particulate suspension agent, and an organosilane stabilizing agent is described. It is mentioned that suitable organosilanes have the general molecular form R-Si (OR ') 3, where R' is an alkyl group of low molecular weight and R is an organic radical having at least one functional group, usually attached to the atom of silicon by a short alkyl chain. Gamma-mercaptopropyltrimethoxysilane is mentioned as a preferred organosilane. US Pat. No. 4,376,830 discloses a composition of a sulfur cement aggregate comprising a sulfur cement and an aggregate containing an expansive clay and processes for preparing such compositions. The processes, and the resulting compositions, are characterized by the addition of certain organosilanes in the composition prior to the solidification (cooling) of the composition. The resulting solidified composition has improved stability in water. It is mentioned that the suitable organosilanes have the formula Z-Si (R 1 R 2 R 3), wherein R 1, R 2 and R 3 can be lower alkoxy groups and Z is an organic radical attached to Si by means of a carbon atom and has at least one reactive group of molten sulfur , Z can be for example mercaptoalkyl. Gamma-mercaptopropyltrimethoxysilane is mentioned as a preferred organosilane. The disadvantages of using gamma-mercaptopropyl-trimethoxysilane are that it is very toxic and has a very unpleasant odor. BRIEF DESCRIPTION OF THE INVENTION It has now been found that the use of a different group of organosilanes, ie organosilanes containing polysulfide having at least two organosilyl groups, in the preparation of a sulfur cement or composite materials of a cement aggregate of sulfur, leads to a sulfur cement or compounds of a sulfur cement aggregate with improved properties. Accordingly, the present invention provides a process for the preparation of sulfur cement or a composite material of a sulfur cement aggregate comprising the following steps: (a) mixing at least one inorganic filler and / or an aggregate and an organosilane containing a polysulfide of the general molecular formula (X3Si) mH (2n + lm) -Cn-Sa-Cn'H (2n '+ lm') (SiX'3) m '(1) where a is an integer in the range from 2 to 8, X and X 'each are, independently, a hydrolyzable group, n and n' are each, independently, an integer in the range from 1 to 4, and m and m 'are each, independently, an integer in the range from 1 to ( 2n + 1), and allow the organosilane to react with the inorganic filler and / or the aggregate; (b) mixing during or after step (a) the elemental sulfur with the inorganic filler and / or the aggregate at a temperature at which the sulfur is liquid to obtain a mixture comprising molten sulfur and a filler and / or a inorganic aggregate; and (c) solidifying the mixture to obtain sulfur cement or a composite material from the sulfur cement aggregate. The invention also provides sulfur cement or a composite material of a sulfur cement aggregate that can be obtained by a process as defined herein above. In a still further aspect, the invention provides the use of an organosilane containing polysulfide of the general molecular formula (1) as defined herein above, as the agglutination agent in a sulfur cement or a material composed of a sulfur cement aggregate. An advantage of the use of an organosilane containing polysulfide with at least two organosilyl groups when compared to the known use of gamma-mercaptopropyl-trimethoxysilane as the agglutination agent in sulfur cement or the composite materials of a sulfur cement aggregate is that the absorption of water by cement or the composite material of a cement aggregate is significantly lower. Another advantage of the use of an organosilane containing polysulfide with at least two organosilyl groups is that it also acts as a sulfur modifier. Therefore, it is possible to prepare sulfur cement or a composite material of a sulfur cement aggregate with a smaller amount of the sulfur modifier than usual or even without the sulfur modifier while achieving the desired degree of modification or plasticization of sulfur. Another advantage is that the sulfur cement prepared according to the invention has improved mechanical properties when compared to the sulfur cement prepared with other organosilanes, for example gamma-mercaptopropyltrimethoxysilane. The additional advantages of the use of an organosilane containing a polysulfide with at least two groups of organosilyl is that it has a much lower toxicity than gamma-mercaptopropyl-trimethoxysilane and that it does not have an unpleasant odor. DETAILED DESCRIPTION OF THE INVENTION In the process according to the invention, the sulfur cement or the composite material of an aggregate of the sulfur cement is prepared by mixing at least one inorganic ingredient with an organosilane containing polysulfide of the general molecular formula (1 ) and allow the organosilane to react with the inorganic ingredient (stage (a)). During or after step (a), the elemental sulfur and optionally additional ingredients are mixed with the inorganic ingredient and the organosilane at a temperature at which the sulfur is liquid (step b)) to obtain a mixture comprising the sulfur molten and inorganic filler and / or aggregate. Then, in step (c) the mixture as obtained in step (b) is solidified by cooling it to a temperature below the sulfur melting temperature to obtain the sulfur cement or a composite material of an aggregate cement material. sulfur. In step (a), at least one inorganic ingredient, i.e. the inorganic filler and / or the inorganic aggregate, is reacted with the organosilane. In the case of a process for the preparation of sulfur cement, the Inorganic ingredient is an inorganic filler. In the case of a process for the preparation of a composite material of a sulfur cement aggregate, the inorganic ingredient can be a filler, an aggregate or both. The inorganic filler or the aggregate that is reacted with the organosilane in step (a) can be any inorganic filler that is known to be suitable as the sulfur cement filler or any aggregate that can be used properly in the materials compounds of the sulfur cement aggregate. Preferably, the inorganic ingredient that is reacted with the organosilane in step (a) has oxide or hydroxyl groups on its surface. Examples of such fillers are fly ash, limestone, quartz, iron oxide, alumina, titania, carbon black, gypsum or talc, mica. Examples of such aggregates are sand, gravel, rock or metallic silicates. Such metal silicates are formed, for example, during the heating of the heavy metal containing the slurry to immobilize the metals. More preferably the organic ingredient is a silicate. Examples of such silicates are quartz, sand, metal silicates and mica. In the case that the metal silicates are formed by heating the slurry for the immobilization of a heavy metal, they are used as the added material, the heat that is available in the heated slurry can be advantageously used in the process of preparing the composite material of a sulfur cement aggregate according to the invention. This can be done for example using steam that is generated during the cooling of the metal silicates for the heating of the elemental sulfur or the ingredients of the process according to the invention. The conditions under which the inorganic ingredient is mixed with the organosilane are such that the organosilane is allowed to react with the inorganic material. Preferably, the temperature at which the inorganic material and the organosilane are mixed is in the range from 120 to 150 ° C, preferably 125 to 140 ° C. The reaction time is typically in the range from 20 minutes to 3 hours, preferably from 30 minutes to 2 hours. The organosilane can be mixed as such with the inorganic ingredient, for example, by spraying on the inorganic ingredient. Preferably, the organosilane is dissolved in a small amount of the solvent, for example an alcohol or a hydrocarbon, to facilitate mixing with the inorganic ingredient. The solvent preferably has a boiling point below the temperature at which stage (a) is effected to allow the solvent to be Evaporate during mixing in step (a). Sulfur, and optionally additional ingredients such as sulfur modifiers, or inorganic filler or additional aggregate, are mixed with the inorganic ingredient and the organosilane at the stage (b) In the event that the process is a process to prepare extended asphalt with sulfur, at least sulfur and bitumen are mixed with the inorganic ingredient in stage (b). In this case, the sulfur is preferably mixed in combination with an H2S suppressant or scavenger, to avoid or minimize the release of H2S which can be formed as a result of the dehydrogenation reactions between the bitumen and the sulfur at the mixing temperature. Suitable H2S suppressors or scavengers are already known in the art, for example from WO 2005/059016, and include free radical inhibitors and redox catalysts. Preferably, the sulfur in step (b) is mixed by the addition of pellets comprising elemental sulfur and H2S suppressants to the inorganic ingredient and the bitumen which are already heated to the temperature of the mixture of 120-180 ° C. Reference is made in this regard to WO 2005/059016, wherein such pellets and this manner of preparing the extended asphalt with sulfur are described in greater detail.

The mixing in step (b) is carried out at a temperature at which the sulfur is liquid, ie typically above 120 ° C, preferably in the range from 120 to 180 ° C, more preferably in the range from 130 ° C. up to 170 ° C. Step (b) may be carried out during or after step (a). If step (b) is carried out during step (a) all the ingredients of the sulfur cement or the composite material of an aggregate of the sulfur cement are mixed at a temperature at which the sulfur is liquid. Preferably, step (a) is carried out prior to step (b) to allow the organosilane to react with the inorganic filler and / or the aggregate before the sulfur is added. A sulfur modifier can be added in step (b). Sulfur modifiers, often referred to as sulfur plasticizers, are already known in the art. Any sulfur modifier known in the art can be applied properly. An example of a known class of suitable sulfur modifiers are olefinic compounds that are copolymerized with sulfur. Known examples of such olefinic sulfur modifiers are dicyclopentadiene, limonene or styrene. It is an advantage of the inventive process according to the invention that less or none at all of the sulfur modifier is necessary when compared to the sulfur cement preparation processes where none or a different organosilane is used. The amount of organosilane that is mixed with the inorganic ingredient in step (a) is preferably in the range of 0.1 to 0.2% by weight based on the weight of the inorganic filler and the aggregate in the sulfur cement or the composite of a sulfur cement aggregate, more preferably in the range from 0.02 to 0.1% by weight. In case an inorganic filler and / or an additional aggregate is mixed in step (b), the amount of the organosilane will be based on the total weight of the filler and the aggregate in the final product, i.e. including the filler and the aggregate material that is added in stage (b). In an alternative process according to the invention, the sulfur cement or the composite material of a sulfur cement aggregate is prepared by mixing, at a temperature at which the sulfur is liquid, the elemental sulfur with an inorganic filler and / or an aggregate that has already been reacted with an organosilane according to the general molecular formula (1). Other ingredients, for example sulfur modifiers, a filler or additional aggregate, or bitumen, can also be mixed. A mixture comprising molten sulfur and a filler Inorganic and / or an aggregate material that has already been reacted, is thus obtained, which is solidified by cooling it. The silica that has already been reacted with an organosilane according to the general molecular formula (1) is commercially available from Degussa as Coupsil®. The organosilane is an organosilane containing a polysulfide, having at least two organosilyl groups having the general formula (X3Si) mH (2n + lm) -Cn-Sa-Cn'H (2n '+ lm') (SiX ' 3) m '(1) In the general molecular formula (1), a is an integer in the range from 2 to 8, preferably from 2 to 6. X and X' are each, independently, a hydrolysable group, preferably a halogen, an alkoxy, acyloxy or aryloxy group, more preferably a lower alkoxy group, for example methoxy or ethoxy. n and n 'are each, independently, an integer in the range from 1 to 4, and m and m' are each, independently, an integer in the range from 1 to (2n + l). Preferably, n has the same value as n 'and m preferably has the same value as m'. Preferably, m and m 'are both 1 or 2, more preferably both m and m' are 1. X is preferably the same hydrolyzable group as X '. Particularly preferred organosilanes are bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (3-) trimethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) tetrasulfide. EXAMPLES The invention is further illustrated by means of the following non-limiting examples. Example 1 Preparation of mortar cylinders Six different sulfur mortars were prepared, each from 27.83 grams of dry sand (Normsand) as the aggregate, 16.83 grams of quartz as the filler and 10.35 grams of sulfur. In the preparation of mortar 1, no organosilane was used. In the preparation of mortars 2 to 6, at least one of the filler or aggregate was pretreated with an organosilane. Sulfur mortar 1 (not according to the invention) Sand, quartz and sulfur are mixed at 150 ° C until a homogenous mixture is obtained. The mixture was then poured into a cylindrical steel mold that was preheated to 150 ° C. Pressure (0.25-0.5 tons) is applied until the sulfur drops were visible at the bottom of the mold. The mortar cylinder thus formed was then demoulded. The cylinders have a diameter of 30 mm. Sulfur mortar 2 (according to the invention) 16.83 grams of quartz were pre-treated with 0. 0275 grams of bis (3-triethoxysilylpropyl) tetrasulfide (TESPT). The TESPT was added to the quartz and a sufficient amount of ethanol was added to completely wet the quartz particles. The mixture was then dried at 70-80 ° C until the ethanol was evaporated. The mixture is then heated to 130 ° C and maintained for one hour at this temperature to allow the TESPT to react with the quartz. Sand and liquid sulfur were added and mixed with the other ingredients for approximately 5 minutes at 150 ° C. The liquid mortar mixture was then poured into a cylindrical steel mold which was preheated to 150 ° C and mortar cylinders were formed as described above for the mortar 1. Sulfur mortar 3 (according to the invention) 16.83 grams of Quartz and 27.83 grams of dry Nor sand were preheated with 0.0275 grams of TESPT. Quartz and sand were mixed and the TESPT was added. A sufficient amount of ethanol was added to completely wet the quartz and sand particles. The mixture was then dried at 70-80 ° C until the ethanol was evaporated. The mixture was then heated to 130 ° C and maintained for one hour at this temperature to allow the TESPT to react with the quartz and sand. Liquid sulfur was added and mixed with the other ingredients for about 5 minutes at 150 ° C. The mortar cylinders were made as described above for the mortar 1. Sulfur mortar 4 (according to the invention) As mortars 2 and 3, but now only the sand is pre-treated with TESPT. Sulfur mortar 5 (not according to the invention) As the mortar 4, but now the sand is pre-treated with 0.0275 grams of 3-trimethoxysilylpropan-1-thiol instead of TESPT. Sulfur mortar 6 (not according to the invention) As the mortar 4, but the sand is pre-treated with 0. 0275 grams of 3-trimethoxysilylpropyl methacrylate instead of TESPT. Water absorption The cylinders of the sulfur mortars 1 to 6 were immersed in water for 2 days. The increase in mass was determined. In table 1, the results are shown. Mortars prepared with TESPT (mortars 2 to 4) have a significantly lower water absorption than mortars prepared with organosilanes with a single functionalized organosilyl group (mortars 5 and 6). It is believed that this reflects an improved bond between the filler / aggregate and the sulfur. Example 2 Three different sulfur mortars were prepared, each from 27.83 grams of dry sand (Normsand) as the aggregate, 16.83 grams of quartz as the filler and 10.35 grams of sulfur. In the preparation of all three mortars, the aggregate (sand) was pre-treated with an 11 year organ. In the preparation of the mortar 7 (according to the invention) 0.0330 grams of TESTP were added to the sand; in the preparation of the mortar 8 (according to the invention) 0.0893 grams of TESPT are added to the sand; in the preparation of the mortar 9 (not in accordance with the invention) 0.0330 grams of 3-1 r-methoxys 111 lpropan- 1- 1101 were added to the sand. The mortars were prepared as described above for mortars 4 and 5. The compressive strength and modulus of E under the compression of the cylinders of mortars 7 and 9 were determined in a tension controlled compression test using a Zwick TT0727 controller with a 300 kN load cell, a test speed of 2.4 kN / s, a preload of 119.64 kN and a precharge speed of 2.4 kN / s. The compressive strength (in N / mm2) and the E module (in MPa) are shown in table 2. 40x40x160 mm rods were prepared from the sulfur mortars 7 and 8. The resistance to bending (in N / mm2) of the bars was determined in a 1! load experiment of three points with an increasing load (0.05 kN / s). The results are shown in table 2. Example 3 Two different samples of asphalt spread with sulfur were prepared. Sample 1 (according to the invention) was prepared using the aggregate pretreated with TESPT. Sample 2 (comparative example) was prepared using the same aggregate without the pre-test. Preparation of organosilane-treated aggregate A Cambridge dolomitic limestone aggregate of 19 mm dense grade was treated with TESPT as follows. To 7.5 kilograms of the aggregate of the preheated limestone (130 ° C), 6 grams of TESPT diluted in 50 grams of ethanol were added. The mixture is stirred until the aggregate particles were completely wetted by the TESPT solution. The mixture was then maintained at 130 ° C for one hour to allow the TESPT to react with the limestone. The limestone that has been reacted was then cooled to room temperature and stored for later use. Preparation of extended asphalt with sulfur Extended asphalt samples with Sulfur were prepared as follows. The preheated bitumen (165 ° C) was mixed with the preheated aggregate (165 ° C) for 30 seconds and then the pellets comprising elemental sulfur were added with an H2S suppressant. The resulting mixture had a temperature of 145 ° C. The mixture was then solidified by cooling to room temperature. The resulting asphalt with resulting sulfur comprised 3.8% by weight of bitumen, 2.5% by weight of sulfur and the remainder is the aggregate material. For example 1, dolomitic limestone pretreated with TESPT as described above was used. For example 2, dolomitic limestone was used as such. Testing of asphalt samples spread with sulfur The sensitivity to moisture of asphalt spread with sulfur was determined by measuring the separation of the binder film (bitumen and sulfur) from the aggregate after submerging the loose asphalt in water and by the measurement of the change in tensile strength of compacted asphalt after saturation with water and freeze-thaw cyclization. The disbonding of the binder film was measured by the Place a 5-10 mm size fraction of loose asphalt in the ErlenMeyer containers and cover with distilled water at room temperature. The containers were stirred for 24 hours at 200 rpm. The disunity of the binder film was then determined visually. The observation error is + _ 5%. The results are shown in Table 3. The relationship between the tensile strength in the wet phase (after submersion in water for 24 hours and the freeze-thaw cyclization) and the dry tensile strength of the asphalt samples compacted was determined in accordance with ASTM D4867. The asphalt samples were compacted to a fraction of air voids of 7 + 1% and allowed to cure under ambient conditions for 14 days. The dry tensile strength of a subset of the samples was measured. Another subset of the samples was immersed in water for 24 hours and then subjected to a freeze-thaw cycle before the tensile strength was measured. The ratio of the wet / dry tensile strength of the two samples is given in Table 3.

Table 1 Absorption of water from mortars 1 to 6 t * 3-trimethoxysilylpropan-1-thiol is the IUPAC name for gamma-mercaptopropyltrimethoxysilane. fifteen Table 2. Mechanical properties of sulfur mortars at organosilane concentration in% by weight based on the total weight of the filler and the aggregate b TMSP-1-thiol: 3-trimethoxysilylpropan-1-thiol Table 3. Humidity sensitivity of the extended asphalt samples with sulfur 10 to fifteen It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (12)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A process for the preparation of sulfur cement or a material composed of a sulfur cement aggregate, characterized in that it comprises the following steps: (a) ) mixing at least one inorganic filler and / or an aggregate and an organosilane containing a polysulphide of the general molecular formula (X3Si) mH (2n + lm) -Cn-Sa-Cn'H (2n '+ lm') (SiX) '3) m' (1) where a is an integer in the interval from
2. 2 to 8, X and X 'each are, independently, a hydrolysable group, n and n' are each, independently, an integer in the range from 1 to 4, and m and m 'are each, independently, an integer in the interval from 1 to (2n + 1), and allow the organosilane to react with the inorganic filler and / or the aggregate; (b) mixing during or after step (a) the elemental sulfur with the inorganic filler and / or the aggregate at a temperature at which the sulfur is liquid to obtain a mixture comprising molten sulfur and a filler and / or a inorganic aggregate; and (c) solidify the mixture to obtain the cement of Sulfur or a material composed of a sulfur cement aggregate. 2. A process according to claim 1, characterized in that step (a) is carried out prior to step (b).
3. 3. A process according to claim 1 or 2, characterized in that the organosilane is dissolved in a solvent, preferably ethanol, when mixed with the organic filler and / or the aggregate in step (a).
4. 4. A process according to any of the preceding claims, characterized in that the amount of the organosilane according to the general molecular formula (1) is in the range from 0.01 to 0.2% by weight, preferably from 0.02 to 0.1% by weight, based on the weight of the inorganic filler and the aggregate.
5. 5. A process for the preparation of a sulfur cement or a material composed of a sulfur cement aggregate, characterized in that it comprises mixing the elemental sulfur with an inorganic filler and / or an aggregate that has been reacted with an organosilane containing a polysulphide of the general molecular formula (1) according to claim 1, at a temperature at which the sulfur is liquid to obtain a mixture comprising the molten sulfur and which has been reacted with the organic filler and / or the aggregate, and solidify the mixture to obtain the sulfur cement or a composite material of a sulfur cement aggregate.
6. 6. A process according to any of the preceding claims, characterized in that m and m each are independently, 1 or 2, preferably both m and m 'are 1.
7. 7. A process according to any of the preceding claims, characterized in that X and X 'are an alkoxy group with 1 to 4 carbon atoms.
8. 8. A process according to claims 6 and 7, characterized in that the organosilane containing the polysulfide is bis (3-triethoxysilylpropyl) tetrasulfide.
9. 9. A process according to any of the preceding claims, characterized in that the filler or aggregate has oxide and hydroxyl groups on its surface.
10. 10. A process according to claim 9, characterized in that the filler and / or the aggregate is a silicate.
11. 11. A sulfur cement or a material composed of a sulfur cement aggregate characterized in that it can be obtained by a process according to any of the preceding claims.
12. 12. The use of an organosilane containing a polysulfide of the general molecular formula (1) according to any of claims 1 and 6 to 8 as an agglutination agent in the sulfur cement or in a composite material of a cement aggregate of sulfur.