Bitumen solid at ambient temperature

Abstract

Granules of material usable as a road binder or sealing binder, including a core and a coating layer, where: the core is made of a first composition including at least one material chosen from: a bitumen base, pitch, and clear binder, and the coating layer is made of a second composition including: at least one viscosifying compound, at least one first anticaking agent selected from alkali and alkaline-earth metal silicates, and at least one second anti-caking agent distinct from the silicates. Also, a method for producing granules of material that can be used as a road binder or sealing binder, and the use thereof as a road binder, in particular for the production of coated materials. Also, a method for producing coated materials from granules of material that can be used as a road binder or as a sealing binder and a method for transporting and/or storing and/or handling granules.

Claims

1. Pellets of material that can be used as a road binder or as a sealing binder, comprising a core and a coating layer, wherein: the core is comprised of a first composition comprising at least one material selected from the group consisting of: a bitumen base, a pitch and a clear binder, and the coating layer is comprised of a second composition which comprises: at least one viscosifying compound, at least one first anticaking agent comprised of silicates selected from the group consisting of alkali metal silicates and alkaline earth metal silicates, a silica SiO.sub.2: metal oxide M.sub.xO mole ratio of the silicates being from 1.00 to 4.00, M representing the metal cation and x being 1 or 2 depending on the nature of the alkali metal cation or alkaline earth metal cation, and at least one second anticaking agent distinct from the silicates of the first anticaking agent.

2. The pellets as claimed in claim 1, wherein the silicates are alkali metal silicates.

3. The pellets as claimed in claim 2, wherein the silicates are sodium silicates.

4. The pellets as claimed in claim 3, wherein the silica SiO.sub.2: sodium oxide Na.sub.2O weight ratio of the silicates is from 1.00 to 4.00.

5. The pellets as claimed in claim 4, wherein the silica SiO.sub.2: sodium oxide Na.sub.2O weight ratio of the silicates is from 1.50 to 3.75.

6. The pellets as claimed in claim 5, wherein the silica SiO.sub.2: sodium oxide Na.sub.2O weight ratio of the silicates is from 2.00 to 3.50.

7. The pellets as claimed in claim 1, wherein the silicates have silicic units.

8. The pellets as claimed in claim 1, wherein the coating layer comprises: from 25% to 50% of the one or more viscosifying compounds, from 1% to 50% of the one or more silicates that are alkali metal silicates and/or alkaline earth metal silicates, and from 25% to 49% of the second anticaking agent distinct from the silicates, the percentages being expressed by weight relative to a total weight of the coating layer.

9. The pellets as claimed in claim 1, wherein the viscosifying compound is selected from the group consisting of: gelling compounds; polyethylene glycols (PEG); and mixtures of such compounds.

10. The pellets as claimed in claim 1, wherein the second anticaking agent is selected from the group consisting of: talc; fines, with the exception of limestone fines; sand; cement; carbon; wood residues; rice husk ash; glass powder; clays; alumina; silica; silica derivatives; plastic powder; lime; hydrated lime; plaster; rubber crumb; polymer powder; and mixtures of these materials.

11. The pellets as claimed in claim 10, wherein the second anticaking agent is selected from the group consisting of fines with the exception of limestone fines.

12. The pellets as claimed in claim 1, wherein the first composition has a needle penetrability measured at 25° C. according to the standard EN 1426 of from 5 to 330 1/10 mm.

13. The pellets as claimed in claim 1, wherein the first composition has a needle penetrability measured at 25° C. according to the standard EN 1426 of from 10 to 220 1/10 mm.

14. The pellets as claimed in claim 1, wherein the first composition also includes at least one chemical additive selected from the group consisting of: an organic compound, a paraffin, a polyphosphoric acid, an adhesion dopant, and mixtures thereof.

15. The pellets as claimed in claim 1, wherein the pellets show stability on transportation or storage or handling at a temperature ranging from 20° C. to 100° C. for a period of greater than or equal to 2 months.

16. A process for manufacturing bituminous mixes comprising at least one road binder and aggregates, the road binder being chosen from the pellets as claimed in claim 1, the process comprising at least the steps of: heating the aggregates to a temperature ranging from 100° C. to 180° C., mixing the aggregates with the road binder in a tank such as a mixer or a mixing drum, and obtaining bituminous mixes.

17. The process as claimed in claim 16, which does not comprise a step of heating the road binder before it is mixed with the aggregates.

18. The process as claimed in claim 16, wherein the step of mixing the aggregates with the road binder is performed with stirring, and the stirring is then maintained for not more than 5 minutes.

19. A process for manufacturing pellets of material that can be used as a road binder or as a sealing binder, composed of a core and a core coating layer, the process comprising: i) shaping the core from a first composition comprising at least one material selected from the group consisting of: a bitumen base, a pitch and a clear binder, ii) coating the core on all or part of its surface with a second composition comprising at least one viscosifying compound, at least one first anticaking agent of silicates selected from the group consisting of alkali metal silicates and alkaline earth metal silicates, a silica SiO.sub.2: metal oxide M.sub.xO mole ratio of the silicates being from 1.00 to 4.00, M representing the metal cation and x being 1 or 2 depending on the nature of the alkali metal cation or alkaline earth metal cation and at least one second anticaking agent distinct from the silicates.

20. The process as claimed in claim 19, wherein the second composition is applied to the core of the pellets in a fluidized air bed device.

Description

FIGURE

(1) FIG. 1: Sectional view of the fluidized air bed facility

(2) FIG. 1 represents a sectional view of a fluidized air bed granulator.

(3) Referring to FIG. 1, the fluidized air bed (12) facility (10) (also known as a granulator) comprises a fluidized air bed (12) process chamber (II) in which the cores of a bituminous material (14) are placed and in which an air stream (16) is fed from below to the fluidized bed (12) and through a perforated grid (13) in order to maintain the fluidized bed and in order to dry and/or cool the cores of a bituminous material (14). A coating layer precursor composition (18) is then fed to the fluidized bed by means of a spray nozzle (20) emerging from below into the fluidized bed (12). The fluidized bed (12) process chamber (II) also comprises an insert (22) located above the spray nozzle (20) and in the form of a cylindrical facility piece that can be adjusted in height and diameter and the lower edges (15) of which are adjustably spaced from the perforated grid (13) of the bottom of the fluidized bed (12).

(4) The filtration chamber (IV) comprises several filters (24) for recycling the fine particles emitted during the implementation of the process.

(5) The air stream (16) fed to the fluidized bed (12) is guided by an incoming air housing (I) comprising an incoming air chamber (26).

(6) The fluidized air bed (12) granulator (10) thus comprises 4 distinct zones: (I) the incoming air housing, (II) the process chamber, (III) the expansion chamber and (IV) the filtration chamber.

(7) The zone of the fluidized bed formed by the incoming air chamber (26) has a zone (28) with a higher flow rate of the air stream (16) applied to the cores made of a bituminous material (14).

(8) The coating layer precursor composition (18) is fed into the zone (28) operating ata higher flow rate.

(9) The cores made of a bituminous material (14) originating from the zone (28) at a higher flow rate are returned to the fluidized bed (12).

(10) A portion of the cores made of bituminous material (14) present in the fluidized bed (12) is returned to the zone (28) at higher flow rate, so that a circulation of cores made of bituminous material (14) appears between the fluidized bed (12) and the zone (28) at higher flow rate.

(11) The invention is illustrated by the following examples, which are given without any implied limitation.

EXAMPLES

(12) Starting Materials:

(13) The cores of bituminous material used as starting material in the examples below are composed of:

(14) Bituminous Base (B) a bitumen base of 50/70 grade, denoted B.sub.1, having a penetrability P.sub.25 of 58 1/10 mm and an RBSP of 49.6° C. and commercially available from the Total group under the brand name Azalt®;

(15) Additive: Additive A1 of formula (I): sebacic acid Additive A2 of formula (II): N,N′-ethylenedi(stearamide) sold by the company Croda under the name Crodawax 140®

(16) Core Composition

(17) TABLE-US-00001 TABLE 1 composition of the bituminous binder constituting the pellet core C1 Bitumen base B1 A1 1.5% A2 2.5%

(18) The amounts are expressed as percentage by weight of additive compound relative to the total weight of the composition.

(19) The coating composition used for coating the cores of the pellets is prepared from the following compounds:

Viscosifying Agent

(20) Viscosifying agent V1: pregelatinized corn starch introduced in the form of Lycatab® C commercially available from the company Roquette.

Anticaking Agent

(21) Anticaking agent AG1: sodium silicate introduced in the form of Betol® 39 T sold by the company Woellner,

(22) Anticaking agent AG2: talc introduced in the form of GPR Rectapur® commercially available from the company VWR (CAS 14807-96-6), and

(23) Anticaking agent AG3: mineral fillers of diameter less than or equal to 0.063 mm.

Processes and Methods

I—Preparation of the Pellet Cores

(24) 1. Preparation of the Core Composition

(25) The bitumen base B.sub.1 is introduced into a reactor maintained at 160° C. with stirring at 300 rpm for two hours. The additives are then introduced into the reactor. The contents of the reactor are maintained at 160° C. with stirring at 300 rpm for 1 hour.

(26) 2. Preparation of the Solid Binder Pellets

(27) a) General Method for Preparing the Binder Cores of the Pellets According to the Invention

(28) The core composition is reheated at 160° C. for two hours in an oven before being poured into a silicone mold exhibiting different holes of spherical shape, so as to form the solid binder cores. After having observed the solidification of the binder in the mold, the surplus is leveled off using a blade heated with a Bunsen burner. After 30 minutes, the solid binder in the form of uncoated pellets is removed from the mold and stored in a tray covered with silicone paper. The binder cores are then allowed to cool to ambient temperature for 10 to 15 minutes.

(29) b) General Method for Preparing the Bitumen Cores of the Pellets According to the Invention with an Industrial Process

(30) For the implementation of this method, use may be made of a device and of a process as described in great detail in patent U.S. Pat. No. 4,279,579. Various models of this device are commercially available from the company Sandvik under the trade name Rotoform®.

(31) Bitumen pellets can also be obtained from the bituminous composition according to the invention poured into the tank of such a device and maintained at a temperature of between 130 and 160° C.

(32) An injection nozzle or several injection nozzles make(s) possible the transfer of the bitumen composition according to the invention inside the double pelletizing drum comprising an external rotating drum, the two drums being equipped with slots, nozzles and orifices making possible the pelletizing of bitumen drops through the first stationary drum and orifices exhibiting a diameter of between 2 and 8 mm of the external rotating drum. The bitumen drops are deposited on the upper face of a horizontal conveyor belt driven by rollers.

(33) Bitumen pellets were obtained from the bituminous composition C1 poured into the reservoir of such a device and maintained at a temperature of between 130 and 160° C.

(34) One or more injection nozzles allow the transfer of the bituminous composition C1 inside the pelletizing twin drum including an external rotating drum, the two drums being equipped with slots, nozzles and orifices allowing the pelletizing of drops of bitumen through the first stationary drum and the orifices between 2 and 8 mm in diameter of the external rotating drum. The bitumen drops are deposited on the upper face of a horizontal conveyor belt driven by rollers.

II—Coating of the Pellet Cores

(35) 1. Preparation of the Coating Layer of the Pellets

(36) The coating layer precursor composition is an aqueous composition comprising at least: one viscosifying agent, and one anticaking agent.

(37) It is prepared by mixing the components at ambient temperature in water.

(38) 2. Coating of the Pellets

a) General Method for Coating the Pellet Cores by Dipping (First Embodiment)

(39) 1.sup.st Variant:

(40) The bitumen cores previously obtained in I—are pricked onto a needle before being immersed in the coating composition.

(41) The coated bitumen pellets are deposited on a silicone plate.

(42) Optionally, the coated solid bitumen pellets thus obtained may be coated with an additional layer with lignin powder.

(43) The solid bitumen pellets thus obtained are left in the open air for at least 2 hours and at ambient temperature in order to solidify the coating layer.

(44) Solid bitumen pellets with a core/shell structure according to the invention are thus obtained.

(45) 2.sup.nd Variant:

(46) The bitumen cores obtained in I—are poured into the coating composition. They are then manually stirred in the solution for a few minutes then they are removed and placed on a plate and allowed to dry at ambient temperature (about 30° C.).

(47) Solid bitumen pellets with a core/shell structure according to the invention are thus obtained.

b) General Method for Coating the Pellets According to an Industrial Process (Second Embodiment)

(48) The tests are carried out in the device 10 represented in FIG. 1.

(49) The cores of bituminous material are loaded into the process chamber, the stream of air being in operation. The cores of bituminous material are thus fluidized by the stream of air injected into the process chamber. Finally, the coating layer precursor composition is sprayed into the process chamber by means of the spray nozzle.

III—Evaluation of the Tacky Aspect of the Pellets

(50) The tacky aspect of the pellets is evaluated to the touch by a handler directly after the step of coating the cores (without a drying step).

(51) For pellets of each type, the handler withdraws approximately ten pellets and evaluates the sticky nature of each of them by placing them first of all between two fingers and by then attempting to separate the fingers from the surface of the pellet.

IV—Tests of Load Strength of the Pellets

(52) This test is carried out in order to evaluate the load strength of the pellets at a temperature of 25° C. under a compressive stress. Specifically, this test makes it possible to simulate the temperature and compression conditions of the pellets on each other, to which they are subjected during transportation and/or storage in bulk in 10 to 100 kg bags or in 500 to 1000 kg big bags or in 200 kg drums, and to evaluate their strength under these conditions.

(53) The load strength test is performed according to the following protocol: 5 ml of pellets are placed in a 20 ml syringe and the plunger is then placed on the pellets together with a weight of 208 g, representing a force applied as in a big bag. The whole is placed in an oven at 25° C. for at least 24 hours.

Results

1. Coating of the Binder Cores

(54) In the following examples 1, 2 and 3, the binder cores are coated by dip-coating in the coating composition according to the method described in II-2. a), second variant.

(55) The nature of the coating composition used for each of examples 1, 2 and 3 is given in table 2 below.

(56) TABLE-US-00002 TABLE 2 Examples 1 2 3 Viscosifying agent % Agent V1 11.1 11.1  11.1  Anti-agglomerating agent % Agent AG1 11.1 5.55 — % Agent AG2 — — 5.55 % Agent AG3 — 5.55 5.55 Experiment 2 is according to the invention. Experiments 1 and 3 are comparative.

2. Evaluation of the Bitumen Pellets Obtained

(57) The bitumen pellets in examples 1, 2 and 3 above are then evaluated according to two criteria:

(58) 1) the tacky aspect of the coating layer, and

(59) 2) their behavior at ambient temperature at 25° C.

(60) The results are given in table 3 below.

(61) TABLE-US-00003 TABLE 3 Examples 1 2 3 Tacky aspect yes no yes Behavior at + +++ + ambient temperature at 25° C. +++: the pellets keep their initial shape and do not adhere together ++: the pellets do not adhere together but no longer keep their rounded shape +: the pellets adhere together slightly. −: the pellets are agglomerated. * Tacky aspect of the pellets

(62) The pellets prepared in example 2 are advantageous in that they do not stick. The latter can therefore be bagged and stored directly after the coating step without the need for an additional drying step.

(63) Conversely, the pellets prepared in examples 1 and 3 are tacky. Consequently, it is necessary for these pellets to be subjected to an additional step of drying the coating layer, before it is possible to bag them.

(64) *Behavior at ambient temperature at 25° C.

(65) The pellets prepared in examples 1 and 2 adhere slightly together.

(66) The pellets prepared in example 2 are advantageous in that they retain their initial shape and do not exhibit any adhesion.

(67) Consequently, the handling and transportation/storage of said pellets formed in example 2 are easy and do not cause any detrimental modifications of the pellets.