FI95920B - Process for producing a thermoplastic plastic modified bituminous binder for building materials - Google Patents

Description

95920

Process for the manufacture of thermoplastic modified bituminous binders for building materials - Förfarande för framställning av ett med medopopiskisk plast modifierat bitumbindemedel för byggnadsmaterialer 5

The invention relates to a process for preparing a thermoplastic-modified bituminous binder for building materials, in particular road construction material, in which molten bitumen together with a thermoplastic or a thermoplastic mixture, preferably an olefin polymer, is subjected to a homogenization treatment to form a binder.

A number of methods are known, such as those mentioned above, for the production of bituminous binders which have improved properties over ordinary bitumen due to the addition of thermoplastics. Such modification of bitumen often requires a relatively large amount of work, as several different thermoplastics, the addition of which to bitumen could significantly improve its properties, are very poorly soluble in bitumen; other thermoplastics involved in the modification of bitumen, which have better solubility properties in bitumen, often have relatively high manufacturing costs, and building materials made with such a binder often have lower strength values than building materials mixed with bitumen with poorer bitumen.

The invention relates to a method of the type already mentioned, in which the use of a thermoplastic normally poor in bitumen, such as polyethylene, not only achieves a rapid homogenization process, but also produces a bituminous binder with clearly better properties than bituminous binders assembled in the same or similar manner. methods.

2,95920

The method according to the invention of the type already mentioned is characterized in that an amount corresponding to the difference between the treatment temperature and the decomposition temperature of the thermoplastic (s) in the form of kinetic energy is added to the mixture containing bitumen and thermoplastic or thermoplastic mixture, giving the mixture a rate corresponding to this amount. then the mixture is stopped on a sharply bouncing substrate to form molecular fragments of the thermoplastic or thermoplastic mixture 10 which react easily with the bitumen, whereby if polyethylene is designed as the thermoplastic, the mixture is given a speed of about 30 m / s. By processing temperature is meant a macroscopically measurable temperature of a mixture in the usual way. The decomposition temperature of a thermoplastic is the temperature at which the molecules of the thermoplastic in question decompose into fragments, which in turn react with the bitumen to form new substances. Said molecular fragments also combine with each other.

The above object is achieved by the method according to the invention, and thus also makes it possible to produce a binder based on bitumen and modified thermoplastics in a relatively short time, even when these are sparingly soluble in bitumen, and to achieve a significant improvement in binder properties, for example in adhesive adhesion. as the strength of binder-based building materials.

Kinetic energy is added to the mixture of bitumen and thermoplastic so that it is brought to a high speed. Subsequent abrupt deceleration of this mixture on a bouncing substrate results in a change in kinetic energy pre-added to this mixture in a very short period of time, and thus thermoplastic molecules degrade with the formation of highly reactive molecular fragments without degrading the thermoplastic; in bitumen molecules, 3,959,220, which have a much lower molecular weight than thermoplastic molecules, there is hardly any decomposition on a bouncing substrate during the sharp deceleration of the mixture. This gives an effect corresponding to the short intense heating of the thermoplastic present in the mixture alone, in which no detrimental decomposition takes place due to the very short duration of the heating.

The decomposition of plastic molecules in the formation of particularly reactive fragments can be accelerated, in particular by the action of high centrifugal forces in the mixture of bitumen and thermoplastic to be processed into a binder. To this end, it is advantageous to give the mixture the highest possible rotational speed and to slow down the mixture having this speed with a bouncing vessel in the short term.

It is already known to add mechanical energy to a heated bitumen / thermoplastic mixture, whereby the mixture is stirred more or less vigorously in a very hot state.

20 However, all such methods to date have had the disadvantage that the total energy gain has so far not been properly dosed, leading either to - too little energy added - to end products with poor physical properties or - too much energy gain - to unnecessary energy use or in particular to high bitumen. through decomposition as well as mechanically inferior products. Only according to the doctrine according to the invention is it possible to use the increased energy with the greatest possible savings in the material, in particular the bitumen used, in the specified and directed manner for the controlled decomposition of the mixture or thermoplastics contained in the mixture.

A preferred embodiment of the method according to the invention consists in passing the bitumen and the thermoplastic or the mixture containing the thermoplastic mixture 35 through a narrow gap between two opposing and rotating mixers, on average narrower than 3 mm, preferably narrower than 0.3 mm, and that stirring of said mixture 4 95920 is continued until a clear change in the structure of the mixture can be observed, for example from X-ray lines. The agitators rotating relative to each other are preferably arranged coaxially with each other. The mixing of the mixture can advantageously be interrupted by pauses after passing through each gap.

The above data for the width of the gap 10 between the opposing and rotating mixers are to be understood as averages. The gap can then also be interrupted by depressions, grooves or the like; greater distances at such depressions or grooves shall not be taken into account in averaging the width of the gap.

15

When the molten bitumen-thermoplastic mixture is run through a narrow, preferably narrower than 0.3 mm gap through two mutually rotating mixers, not only the thermal effect but also the stress of the kinetic energy of the mixture passing through the gap due to the impact on the impact surface is obtained. wherein this stress affects in particular the thermoplastic component having a higher molecular weight or a higher molecular weight than bitumen; wherein the degradation of the molecules in the mixture that begins under this loading produces shorter molecular fragments (i.e., molecular fragments with a lower molecular weight or lower molecular weight) that have a strong tendency to interconnect. When, during normal mixing of such a mixture, for example a mixture of bitumen and polyethylene, in which this mixture or the substances contained in it are subjected to combined thermal and mechanical stress, the X-ray spectral spectra characteristic of the crystalline structure of the plastic part can be observed If the treatment of the constituent (s) subjected to molecular degradation at the decomposition temperature is continued long enough, there will again be a gap with a smaller width between the rotary agitators 5 95920 after the process according to the invention. X-ray lines clearly detectable in the study of the mixture passed through, indicating the presence of a new crystalline structure. Corresponding to this presence of X-ray lines characteristic of the crystalline structure, building materials made with the binder obtained according to the invention can show clearly better mechanical properties than building materials formed with binders in which bitumen and thermoplastic are merely mixed with melt with intense stirring. . In addition, another advantage of the above-mentioned method according to the invention, in which a mixture of molten bitumen and thermoplastic is run between the mixers rotating through a narrow gap, is that the production of thermoplastic-modified bituminous binder can be carried out in significantly shorter time . In addition, and this is a very substantial advantage, it is possible to work at a significantly lower average temperature or processing temperature of the thermoplastic and bitumen treatment mixture than in the known homogenization of such a mixture by intensive mixing, and it is obvious that this is possible by mechanical application and that the thermoplastic molecules, on the other hand, break down into highly reactive fragments under the change of the kinetic energy added to the mixture on the bouncing substrate. Such fragments then combine to form at least a partially crystalline structure. This is also evident from the change in X-ray lines compared to the state before the mixture is passed through the gap. In the surrounding bitumen, this at least partially crystalline * structure also forms a close mixture with the bitumen.

The close mixture of the thermoplastic with the bitumen can also be seen in the behavior of the binder prepared according to the invention in longer-lasting heat storage. The mixture of bitumen and thermoplastic treated by the process of the invention is visibly homogeneous when illuminated with light in the visible light wavelength range immediately after manufacture, and shows a dense pattern of light dots on a darker background when illuminated with ultraviolet light; after several hours of hot storage at a temperature higher than the melting temperature of the rod-5 ti thermoplastic, the particles previously visible as dots combine to form a light cover layer having a volume of about 4-8 times the volume of the thermoplastic portion of the mixture; this cover layer can be combined with a simple, short-term mixing again with the rest of the binder to form a visually homogeneous material. This behavior clearly differs in a known manner from the behavior of the product obtained by long-term mixing of a molten mixture of bitumen and thermoplastic; in such a product, after several hours of heat storage, a light cover layer with a volume approximately equal to the volume of the thermoplastic part of the mixture is formed, and re-homogenization of the cover layer with the main part of the material separated from the heat storage requires substantially the same mixing work .

The two agitators, between which there is a gap through which the mixture arranged to form the binder is passed, must rotate relative to each other. This can be accomplished simply by having one mixer in place: and the other rotating. But also both mixers can rotate, and even either in opposite directions of rotation or in the same direction of rotation but at different rotational speeds.

30

Within the framework of the method according to the invention, it is particularly advantageous to pass the mixture containing bitumen and thermoplastic through a gap between coaxially rotating mixers with an average width of about 0.1 mm 35 or even narrower. This advantageous operation of the process according to the invention, in which the mixture to be homogenized is treated in a very narrow gap, which enhances the efficiency of the plastic molecules in the process according to the invention.

II

The further disintegration effect of 7,959,20, resulting in the formation of highly reactive molecular fragments with a particular tendency to recrystallize, can be further enhanced, this effect being achieved with a decreasing gap width at ever lower average temperatures of the mixture. It has further proved advantageous to form a gap so that the mixture is subjected to the pressure formed by the hydrodynamic action.

For said embodiment of the method according to the invention, in which the mixture is passed through a gap, it is preferably provided that the mixture is passed through a gap running radially at least at the outlet boundary, from which the mixture leaves in the radial direction. In this case, a particularly good effect can be obtained when the sharp deceleration of the mixture is carried out in the crack area, preferably immediately after the mixture exits the slit, because the high centrifugal velocity of the plastic molecules and thus the propagating kinetic energy are particularly utilized for reactive distribution.

The treatment of the molten mixture of bitumen and thermoplastic material can be performed in a shielding gas atmosphere or in a vacuum.

25: The invention also relates to a binder prepared by the method according to the invention.

The invention will be further described by way of example with reference to the drawings, in which Figure 1 shows X-ray spectra of various substances and Figure 2 a sectional view of bodies of some different substances.

35 Example 1

A lightly molten mixture of 94% by weight of bitumen B 100 and 6% by weight of high density polyethylene was first mixed in a storage tank, and this mixture was passed from a storage tank to a flow-through mixer with 2 disc-shaped, opposite mixers. wherein the second agitator was stationary and the second was coaxially mounted on the first rotatably and connected to the motor. The facing sides of both the stationary and the rotating mixer were provided with raised lines. On the opposite sides of both mixers, there was a gap of about 0.1 mm between the raised lines of one mixer and the raised lines of the other mixer, through which the mixture to be treated was passed. The rotational speed of the rotary mixer at the outer edge of the gap was about 30 m / s. Similarly, the flow rate of the mixture through the gap was about 30 m / s. A bouncing surface was arranged in the crack area, where the mixture struck and its pace then slowed down sharply. The mixture was passed through a flow mixer 15 times. This required about 20 min. The bituminous binder thus obtained was then mixed with a preheated rock material and a rock powder aggregate having a standardized composition of asphalt concrete 08, and Marshall test pieces were prepared from the building material thus obtained in a standard manner, after which their mechanical properties were examined. The measured values obtained are shown in the table in column 1.

Example 2 The procedure was analogous to Example 1, except that the amount prescribed for the preparation of the binder consisted of a mixture of 94% by weight of bitumen B 100 and 6% by weight of low density polyethylene. The measured values obtained are shown in the table in column 2.

30

Example 3

The procedure was analogous to Example 1, however, the amount prescribed for the preparation of the binder consisted of a mixture of 94% by weight of bitumen B 100 and 6% by weight of 35% by weight of ethylene / propylene diene copolymer. The measured values obtained are shown in the table in column 3.

9 95920

Example 4

The procedure was analogous to Example 1, however, the amount prescribed for the preparation of the binder consisted of a mixture of 94% by weight of bitumen B 100 and 6% by weight of 5% by weight of styrene / butadiene / styrene copolymer. The measured values obtained are shown in the table in column 4.

Example 5

The procedure was analogous to Example 1, except that the amount prescribed for the preparation of the binder consisted of a mixture of 94% by weight of bitumen B 100 and 2% by weight of ethylene / propylene diene copolymer and 4% by weight of low density polyethylene. The measured values obtained are shown in the table in column 5.

15

Example 6

The procedure was analogous to Example 1, except that the amount prescribed for the preparation of the binder consisted of a mixture of 94% by weight of bitumen B 100 and 2% by weight of 20% by weight of ethylene / propylene diene copolymer and 4% by weight of high density polyethylene. The measured values obtained are shown in the table in column 6.

Example 7 The properties of the bitumen used in Examples 1-6 and the building material prepared analogously thereto were studied for comparison. The measured values obtained are shown in the table in column 7.

30 Example 8

The finished binder obtained according to Example 1 was examined in a refrigerated state by X-ray spectral study. In this case, the spectrum marked with the letter a in Fig. 1 of the drawing was obtained. A visually homogeneous mixture having the same composition as the mixture of Example 1 mixed by stirring alone was further examined in the refrigerated state by the same X-ray spectral study to give the spectrum indicated by the letter b in Figure 1, and this X-ray spectral study was also examined in Example 1. polyethylene used to give the spectrum labeled c in Figure 1. These X-ray spectra show that the strong spectral lines present in spectrum 5 and caused by the crystalline structure of polyethylene are no longer present in spectrum b. It follows that this mixture of bitumen and polyethylene mixed by mixing alone also shows virtually no crystalline structure-10 netta. Spectrum a shows spectral lines corresponding to the strong spectral lines of spectrum c caused by the crystalline structure of polyethylene. As a result, the binder prepared by the process of the invention according to Example 1 is in a cooled state at least in a crystalline structure formed partly of molecular fragments of polyethylene.

Example 9 According to Example 2, a sample of 94% by weight of bitumen B 100 and 20% by weight of low density polyethylene from the binder prepared by the process of the invention was solidified in a vessel, after which the body thus obtained was cleaved vertically. The cleavage surface appeared homogeneous when illuminated by visible light; when illuminated with ultraviolet light 25, a dense, evenly distributed pattern of light dots was visible on a darker background. The image of this cleavage surface is indicated by the letter a in Figure 2. A second sample of this binder was stored in a vessel for 24 hours at 160 ° C, and then kept in this vessel, after which the body thus formed was cleaved. When illuminated with ultraviolet light, a light layer was recognizable, which, on worn storage, assumed approximately one-third of the body, while the two-thirds below it had a dark color. The image of the salmon-35 cutting surface of this body is denoted by the letter b in Figure 2. This body was then remelted, and this melt was mixed well at about 170 ° C, whereupon the melt reached a completely homogeneous appearance after a few minutes.

11 95920

Example 10

A mixture of 94% by weight of bitumen B 100 and 6% by weight of low density polyethylene was also formed from the materials used in Example 2. This mixture was stirred to prepare a homogeneous product for 1 1/2 hours at 280 ° C. A sample of this product was then stored in a vessel for 24 hours at 160 ° C, and then allowed to cool in this vessel, after which the body thus formed was cleaved. When illuminated with ultraviolet light, there was an identifiable light layer with a volume approximately equal to the volume of the polyethylene portion of the product and located on the side on the side during the worn storage. The cleavage surface of this part is denoted in Figure 2 by the letter c. This piece was then remelted, and the melt thus obtained was again mixed well at about 280 ° C. Stirring had to be continued for more than 1 hour in order to again achieve a completely homogeneous appearance of the melt.

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Claims (8)

A process for the preparation of a building material modified with a thermoplastic 20, especially for road building materials, wherein the bitumen is subjected to homogenization treatment together with a thermoplastic or thermoplastic mixture, preferably an olefin polymer, to form the binder, characterized in that Bitumen and thermoplastic or thermoplastic blend, in the homogenization treatment, an amount of energy in the form of kinetic energy is added, the amount of energy corresponding to the difference between the treatment temperature and the decomposition temperature of the thermoplastic or thermoplastics, the mixture being supplied at a rate corresponding to this amount of energy abruptly say,. forming bitumen easily reacting molecular fragments of the thermoplastic or thermoplastic mixture, whereby the thermoplastic is polyethylene, the mixture is supplied at a rate of about 30 m / s. Process according to Claim 1, characterized in that the mixture of bitumen and thermoplastic or thermoplastic mixture is driven through a narrow gap which exhibits in average a smaller width of 3 mm, preferably a smaller width of 0.3 mm. which splat is disposed between two resistors and in relation to one another rotating mixers, and that the processing of said mixture is continued until a change in the structure of the mixture is detectable, e.g. from a change in the lines of an X-ray spectrum. Method according to claim 2, characterized in that the treatment of the mixture is interrupted with pauses after each gap passage. Method according to Claim 2 or 3, characterized in that the mixture is driven through a 0.1 mm width or narrower gap, which lies between the relative rotating mixers. Method according to any one of claims 2-4, characterized in that the mixture is driven through a gap which lies radially on the outer edge, the mixture coming out in a radial direction. 6. A method according to claim 5, characterized in that the abrupt braking is carried out in the gap zone, preferably immediately after the mixture has emerged from the gap. • · Process according to any of claims 2-6, characterized in that the mixture in the gap is subjected to a pressure formed by hydrodynamic action. 30 8. Bituminous binders for building materials, especially for road building materials, characterized in that it is manufactured by means of a method according to any of the above claims 1 - 7. • ·