Bitumen solid at ambient temperature

Abstract

Granules of material usable as a road binder or as a sealing binder including a core and a coating layer, wherein: the core consists of a first composition including at least one material selected from: a bitumen base, a pitch, a clear binder, and the coating layer consists of a second composition which includes: at least one viscosifying compound selected from cellulose ethers, and at least one anticaking agent. Also, a method for producing granules of material that can be used as a road binder or as a sealing binder, and the use thereof as a road binder, in particular for the production of coated materials. Also, a method for producing coatings from granules of material that can be used as a road binder or as a sealing binder and to 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 consists 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 consists of a second composition which comprises, relative to the total weight of the coating layer: from 10% to 90% by weight of at least one viscosifying compound, selected from the group consisting of cellulose ethers, and from 10% to 90% by weight of at least one anticaking agent, which is siliceous fines.

2. The pellets as claimed in claim 1, wherein the cellulose ether is selected from the group consisting of: methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), hydroxybutylmethylcellulose (HBMC), carboxymethylcellulose (CMC), sodium carboxymethylcellulose (Na-CMC), carboxymethylsulfoethylcellulose, and hydroxyethylmethylcarboxymethylcellulose.

3. The pellets as claimed in claim 2, wherein the cellulose ether is selected from the group consisting of: hydroxyethylmethylcellulose, hydroxypropylmethylcellulose and hydroxybutylmethylcellulose.

4. The pellets as claimed in claim 3, wherein the cellulose ether is hydroxypropylmethylcellulose.

5. 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.

6. The pellets as claimed in claim 5, 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.

7. The pellets as claimed in claim 1, wherein the first composition also comprises 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.

8. The pellets as claimed in claim 1, wherein the coating layer is solid at a temperature greater than 60° C.

9. The pellets as claimed in claim 1, wherein the coating layer has an average thickness greater than or equal to 20 μm.

10. 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 as claimed in claim 1, this 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 (a) at least one viscosifying compound selected from the group consisting of cellulose ethers and (b) at least one anticaking agent.

11. The process as claimed in claim 10, wherein the second composition is applied to the core of the pellets in a fluidized air bed device.

12. The pellets as claimed in claim 1, which 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.

13. The pellets as claimed in claim 1, which show stability on transportation or storage or handling at a temperature ranging from 20° C. to 80° C. for a period of greater than or equal to 3 months.

14. The pellets as claimed in claim 1, which have a weight of between 0.1 g and 50 g.

15. 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, this 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, obtaining bituminous mixes.

16. The process as claimed in claim 15 wherein the process comprises the step of heating the aggregates to a temperature ranging from 120° C. to 160° C.

17. The process as claimed in claim 15, 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 15, wherein the step of mixing the aggregates with the road binder is performed with stirring, and stirring is then maintained for not more than 5 minutes.

Description

FIGURE

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

(2) 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 shells formed around the cores of 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).

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

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

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

(6) 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).

(7) The coating layer precursor composition (18) is fed into the zone (28) operating at a higher flow rate.

(8) 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).

(9) 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.

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

Experimental Section

(11) In these examples, the parts and percentages are expressed by weight unless otherwise indicated.

(12) Material

(13) Fluidized Air Bed Device: Facility 1:

(14) Facility 1 is a fluidized air bed facility used in the process for manufacturing the pellets according to the invention.

(15) The following examples 1 to 6 were carried out in a fluidized air bed granulator sold by the company Glatt—under the trade name ProCell—and the sectional view of which is represented in FIG. 1.

(16) Starting Materials:

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

(18) 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®;

(19) 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®

(20) Core Composition

(21) TABLE-US-00001 TABLE 1 comDosition of the bituminous binder constitutina the Dellet core C1 Bitumen base B1 A1 1.5% A2 2.5%

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

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

(24) Viscosifying Agent:

(25) Viscosifying agent V1: hydroxypropylmethylcellulose introduced in the form of Sepifilm® LP 010 commercially available from the company SEPPIC,

(26) Viscosifying agent V2: Cellulose (CAS 9004-34-6) commercially available from the company Sigma-Aldrich,

(27) Viscosifying agent V3: Gelatin of type 280 Bloom 6 Mesh-Pig Skin commercially available from the company Weishardt International.

(28) Anticaking Agent:

(29) Anticaking agent AG1: siliceous fines originating from La Noubleau. Processes and Methods:
I—Preparation of the Pellet Cores
1. Preparation of the Core Composition

(30) 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.

(31) 2. Preparation of the Cores of the Solid Binder Pellets

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

(33) 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.

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

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

(36) 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.

(37) 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.

(38) 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.

(39) 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.

(40) II—Coating of the Pellet Cores

(41) 1. Preparation of the Coating Layer

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

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

(44) 2. Coating of the Pellets

(45) a) General Method for Coating the Cores of Pellets According to the Invention (First Embodiment)

(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.

(48) b) General Method for Coating the Pellet Cores According to an Industrial Process (Second Embodiment)

(49) The cores of bituminous material are loaded into the process chamber of the device in FIG. 1, 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.

(50) III—Test of Load Strength of the Pellets

(51) This test is carried out in order to evaluate the load strength of the pellets 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.

(52) 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 thing is then placed in an incubator, either at a temperature of 25° C. for at least 24 h (tests of load strength at ambient temperature) or at a temperature of 65° C. for at least 4 hours (tests of load strength at high ambient temperature).

(53) IV—Evaluation of the Tacky Aspect of the Pellets

(54) 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).

(55) 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 40 fingers and by then attempting to separate the fingers from the surface of the pellet.

(56) Results

(57) 1. Bitumen Pellets Coated by Means of a Fluidized Air Bed Device (Second Embodiment) a) Preparation of the Bitumen Pellets

(58) Experiments 1 to 6 are carried out in device 10 represented in FIG. 1 according to the coating method described in II-2.b).

(59) The parameters for carrying out the various experiments are given in table 2 below. The spray pressure (in bar) is from 1 to 3 bar.

(60) The coating composition used in experiments 1 to 6 is prepared from:

(61) hydroxypropylmethylcellulose as viscosifying agent (agent V1), and

(62) siliceous fines originating from La Noubleau as anticaking agent (agent AG1).

(63) TABLE-US-00002 TABLE 2 Examples 1 2 (*) 3 (*) 4 (*) 5 6 Coating layer precursor composition % of viscosifying — 10 10 10 7.5 10 agent % anticaking 20 — — — 12.5 10 agent Conditions for carrying out the process Amount of cores 1050 937 1305 1107 1123 fluidized (in g) Amount of 1003 407 194 224 1060 1000 precursor composition sprayed (in g) Fluidization flow 300 300 280 280 250 250 rate (in m.sup.3/h) Product 35 35 35 35 17 17 temperature (in ° C.) Spray flow rate 25.1 22.6 10.8 3.3 15.4 14.1 (in g/min) (*) following the agglomeration of the pellets during the process, the latter was interrupted before having sprayed all of the precursor composition.
Examples 1 to 4 are counter examples.
Examples 5 and 6 are examples according to the invention. b) Evaluation of the Bitumen Pellets Obtained

(64) The pellets obtained in examples 1 to 6 are then evaluated according to several criteria:

(65) 1) the obtaining of bitumen pellets comprising a core and a coating layer,

(66) 2) the homogeneity of the coating layer formed,

(67) 3) the deformation of the pellets,

(68) 4) the presence of agglomerates, and

(69) 5) their resistance at high temperature (load strength evaluated at 65° C. for 4 h).

(70) The results are presented in table 3 below.

(71) TABLE-US-00003 TABLE 3 Examples 1 2 3 4 5 6 Pellet formation yes no no no yes yes Resistance at − − − − ++ +++ ambient temperature at 65° C. +++: the pellets retain their initial shape and do not adhere to one another. ++: the pellets do not adhere to one another but no longer exhibit their rounded shape. +: the pellets adhere slightly to one another. −: the pellets are agglomerated. Coating layer comprising exclusively an anticaking agent (example 1)

(72) In example 1, the coating layer precursor composition comprises only an anticaking agent.

(73) It is noted that the bitumen pellets obtained according to example 1 are not stable at high temperature.

(74) The sole presence of an anticaking agent in the coating layer precursor composition does not make it possible to obtain bitumen pellets that are stable at high temperature. Coating layer comprising only a viscosifying agent chosen from cellulose ethers (examples 2, 3, 4)

(75) In examples 2, 3 and 4, the coating layer precursor composition comprises exclusively a viscosifying agent chosen from cellulose ethers.

(76) The cores and the coating layer precursor composition sprayed in the process chamber stick to one another without however forming pellets. The cores agglomerate and make the formation of bitumen pellets impossible.

(77) The sole presence of a viscosifying agent chosen from cellulose ethers in the coating layer precursor composition does not make it possible to obtain well-separated bitumen pellets. Coating layer comprising both a viscosifying agent chosen from cellulose ethers and an anticaking agent (examples 5 and 6)

(78) In examples 5 and 6, the coating layer precursor composition comprises both a viscosifying agent chosen from cellulose ethers and an anticaking agent.

(79) The bitumen pellets formed in examples 5 and 6 exhibit good resistance to conditioning at an ambient temperature of 65° C. in so far as they virtually do not adhere to one another.

(80) The pellets formed in example 6 are particularly advantageous in that they retain their initial shape.

(81) Thus, the handling and transportation/storage of said pellets formed in examples 5 and 6 will be easy in so far as the pellets do not agglomerate together at high ambient temperature. 2. Bitumen Pellets Coated by Dipping (First Embodiment) a) Preparation of the Bitumen Pellets

(82) For experiments 7, 8 and 9, the coating of the bitumen cores is carried out by dipping in the coating composition according to the method described in II-2.a).

(83) The nature of the coating composition used for each of experiments 7, 8 and 9 is given in table 4 below.

(84) TABLE-US-00004 TABLE 4 Examples 7 8 9 Viscosifying agent % Agent V1 14.3 — — % Agent V2 — 14.3 — % Agent V3 — — 14.3 Anticaking agent % Agent AG1 14.3 14.3 14.3

(85) Experiment 7 is according to the invention.

(86) Experiments 8 and 9 are comparative.

(87) b) Evaluation of the Bitumen Pellets Obtained

(88) The pellets obtained in examples 7 to 9 are then evaluated according to several criteria:

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

(90) 2) their behavior at ambient temperature (load strength evaluated at 25° C. for 24 h).

(91) The results are given in table 5 below.

(92) TABLE-US-00005 TABLE 5 Examples 7 8 9 Tacky aspect no yes 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

(93) The pellets prepared in example 7 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.

(94) Conversely, the pellets prepared in examples 8 and 9 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.

(95) *Behavior at Ambient Temperature at 25° C.

(96) The pellets prepared in examples 8 and 9 adhere slightly together.

(97) The pellets prepared in example 7 are advantageous in that they retain their initial shape and do not exhibit any adhesion.

(98) Consequently, the handling and transportation/storage of the pellets formed in example 7 are easy in as much and do not cause any detrimental modifications of the state of the pellets.