DE202019103224U1 - Bitumen mixture - Google Patents

Abstract

Bitumen mixture containing a matrix of bitumen, low molecular weight substances and at least one stabilizer to increase the viscosity of the bitumen mixture, characterized in that at least one stabilizer is in the form of surface-modified polymer particles with a multimodal particle size distribution.

Description

The present invention relates to bitumen mixtures which contain a matrix of bitumen, a proportion of low molecular weight substances and at least one modifier to increase the viscosity of the bitumen mixture.

In particular, the present invention relates to bitumen mixtures which contain surface-modified polymer particles which have a multimodal particle distribution, the surface-modified polymer particles being able to take up or release low molecular weight substances from an organic matrix in a controlled manner.

When processing bitumen, the composition of the mixture is decisive for its workability. E.g. the rheology (viscosity, thixotropy, structural viscosity, rheopexy and dilatancy) of bitumen mixtures can be changed by a wide variety of additives, in particular by organic or inorganic as well as soluble or insoluble additives. The viscosity can be reduced by adding soluble, low molecular weight additives or by chemically reducing the molecular weight. The viscosity can be increased by adding soluble, high molecular weight additives or by chemically building up the molecular weight. However, as an undesirable side effect of the above measures, other material properties of the bitumen mixture, such as Strength, elasticity, toughness, creep behavior and fracture behavior, negatively influenced.

The WO2012010150 A1 describes a method for the production of a bulk material of agglomerates from rubber particles and wax. This bulk material is used for the production of asphalt or bitumen masses. It is produced by activating rubber by swelling and using a swelling agent and adding a melt of viscosity-reducing wax and optional polyoctenamer and agglomerating the activated rubber particles with the viscosity-reducing wax and optional adhesion-improving substances, the swelling agent penetrating into the spaces between the rubber molecules and the molecules push apart, whereby the physical forces of attraction are reduced or interrupted, so that the resulting larger volume leads to a reduction in viscosity and the softening lead to a more intimate and homogeneous wetting with the wax. Rubber particles without a specific size distribution are used.

The US5936015-A1 discloses rubber-modified asphalt pavement binders. A rubber powder with particle sizes smaller than 80 mesh (ie <177 µm) is used.

It is also known that the rheology of organic substances and mixtures can be influenced by the fact that the proportion of low molecular weight substances, e.g. by extraction, is lowered. From physicochemical considerations it should be understood that low molecular weight substances can also be removed by particulate additives due to adsorption. In many cases, a disadvantage of this method is the associated adsorption time and adsorption capacity.

The object of the present invention is therefore to provide a bitumen mixture whose rheological properties can be adapted to different applications and which, in particular, has a shortened setting time ("time to property").

Surprisingly, it was found that by adding surface-modified polymer particles, in particular surface-modified rubber particles that have a bimodal or multimodal particle size distribution, the adsorption or desorption duration and the adsorption or desorption capacity of bitumen mixtures can be controlled over time.

The object of the invention is therefore achieved with a bitumen mixture having the features of claim 1. The bitumen mixture according to the invention comprises a matrix of bitumen, a proportion of low molecular weight substances and at least one modifier to increase the viscosity of the bitumen mixture, the at least one modifier being in the form of surface-modified polymer particles with a multimodal (i.e. at least one bimodal) particle size distribution.

In the production of the bitumen mixture according to the invention, in particular ground rubber particles can be used which have undergone a surface modification due to thermal and / or mechanical influences, in particular through a grinding process, or through treatment with liquids or solids and have an at least bimodal particle size distribution.

In preferred embodiments of the invention, the low molecular weight substances are originally contained in the bitumen matrix and are absorbed by diffusion on or in the polymer particles, in particular adsorbed or embedded, the absorption of the low molecular weight substances on the various fractions of the polymer particles with different particle size distributions within different absorption times he follows. Another preferred embodiment of the invention provides that the low molecular weight substances are originally contained in the surface-modified polymer particles or are attached to them and migrate into the bitumen matrix by diffusion and become embedded therein, with the diffusion of the low molecular weight substances from the various fractions of the polymer particles different particle size distribution takes place within different diffusion times.

One aspect of the invention is that the addition of the polymer particles to the bitumen matrix results in a time-controlled influencing of the rheology of the polymer composition, in particular due to the diffusion times or absorption times depending on the diameter of the polymer particles. In addition, one aspect of the invention is that by adding the polymer particles with a multimodal particle size distribution to the bitumen matrix, the establishment of a stable state with desired rheological properties of the polymer composition takes place faster than with a monomodal particle size distribution of the polymer particles and in particular at least twice as fast.

Furthermore, an embodiment of the invention is useful in which, in addition to the polymer particles, a release agent is added to make the polymer particles free-flowing. An embodiment is also preferred in which the polymer particles are introduced into the matrix in at least two fractions, the fractions of the polymer particles differing from one another by a different particle size distribution, in particular by a different mean particle size, preferably with a first fraction with a particle size distribution a first relative maximum at a first mean particle size and with a second fraction with a particle size distribution with a second relative maximum at a second mean particle size, the second mean particle size being larger than the first mean particle size and preferably at least twice as large as the first mean Particle size.

When using the bitumen mixture according to the invention, the technical processability of the bitumen can be considerably improved. By setting the modality of the particle size distribution of the polymer particles, it is also possible to set the desired viscosity point in time (by calculating the parameters mentioned below). This is a great advantage compared to known bitumen mixtures, which have a fixed and also long processing period.

Further preferred embodiments of the bitumen mixture according to the invention are defined in the subclaims.

• 1 zeigt das Prinzip von Adsorption und Desorption von Polymerpartikeln und niedermolekularen Stoffen;
• 2 zeigt schematisch eine Partikelgrößenverteilung mit drei Maxima;
• 3a und 3b zeigen monomodale Partikelgrößenverteilungen von Gummipulverfraktionen 4a zeigt eine bimodale Partikelgrößenverteilungen eines Gummipulvergemisches aus den Gummipulverfraktionen von 3a und 3c;
• 4b zeigt eine bimodale Partikelgrößenverteilungen eines Gummipulvergemisches aus den Gummipulverfraktionen von 3a und 3b;
• 5 zeigt ein Viskositäts-Zeit-Diagramm eines Gemisches, das aus einer Matrix mit darin eingelagerten Polymerpartikeln zusammengesetzt ist.

The functional principle on which the invention is based and the essential features of the invention are explained in more detail below with reference to the accompanying drawings. The drawings show:

• 1 shows the principle of adsorption and desorption of polymer particles and low molecular weight substances;
• 2 shows schematically a particle size distribution with three maxima;
• 3a and 3b show monomodal particle size distributions of rubber powder fractions 4a shows a bimodal particle size distribution of a rubber powder mixture from the rubber powder fractions of 3a and 3c ;
• 4b shows a bimodal particle size distribution of a rubber powder mixture from the rubber powder fractions of 3a and 3b ;
• 5 shows a viscosity-time diagram of a mixture which is composed of a matrix with polymer particles embedded therein.

The bitumen mixture according to the invention comprises a matrix of bitumen, a proportion of low molecular weight substances and at least one modifier to increase the viscosity of the bitumen mixture, the at least one modifier being in the form of surface-modified polymer particles with a multimodal particle size distribution.

The surface-modified polymer particles can in particular be ground rubber particles. The rubber particles can be in the form of rubber powder from old tires, but also from others rubber-containing objects can be obtained by mechanical grinding at room temperature and / or in the cold (cryo-grinding). The rubber mixture can consist of a single type of rubber. If the rubber particles are produced from old tires by grinding tire rubber, however, it is usually a mixture of several different types of rubber.

To produce the bitumen mixture according to the invention, at least a first fraction of surface-modified polymer particles and a second fraction of surface-modified polymer particles are added to the bitumen matrix, the first and second fractions of polymer particles having a different particle size distribution, in particular a different mean particle diameter. The particle size distribution of the polymer particles therefore has at least one first relative maximum with a first mean diameter of the polymer particles and a second relative maximum with a second mean diameter of the polymer particles.

The adsorption and desorption behavior of the bitumen mixture can be determined and adapted via the particle size and the polymer type of the surface-modified polymer particles. This is in 1 illustrated. Due to the small polymer particles of the first fraction with a smaller mean particle diameter, a short-term adsorption or desorption of the low molecular weight fractions from the organic bitumen matrix takes place in the initial phase. The large polymer particles of the second fraction with a larger mean particle diameter determine a long-term adsorption or desorption capacity. The modification of material properties, in particular the rheological properties of the bitumen mixture, can be timed through the ratio of the particle fractions of the first and second fractions of the polymer particles.

The surface modification of the polymer particles serves the thermodynamic adaptation of the particle surface to the organic matrix and their integration into the organic matrix, whereby a negative effect on other material properties is avoided.

In addition to high polymer components, the bitumen matrix also contains naturally or additively present low molecular weight substances that are liquid when the bitumen mixture is processed as intended.

The polymer particles absorb the low molecular weight substances in the matrix from the organic matrix in a time-controlled manner or release them in a time-controlled manner. The surface modification of the polymer particles ensures a thermodynamic adaptation of the particle surface and its integration into the organic matrix.

The components of the bitumen mixture according to the invention and their properties that are essential for the invention are explained in detail below:

Polymer particles

The polymer particles can consist of one or more different polymers, be crosslinked or uncrosslinked, or be filled or unfilled. They can also be filler reinforcing or non-reinforcing and of any desired geometry (determined by dimension and form factor = aspect ratio). Ground rubber particles are preferably used as polymer particles in the bitumen mixtures according to the invention.

The polymer particles can be produced by a per se known method, e.g. by grinding, precipitation, spray drying, suspension or dispersion polymerization, sieving, fractionation, centrifugation, etc. In particular, the polymer particles can be produced by grinding rubber to give rubber particles.

Surface modification

The polymer particles are subjected to a surface modification either during the manufacturing process or afterwards. The surface modification serves the thermodynamic adaptation of the particle surface to the organic matrix and its integration into the organic matrix.

A surface modification can take place by generating or applying one or more organic substances to the polymer particles. For example, a polymer or prepolymer with a molecular weight (weight average) of at least 1000 g / mol, which is thermodynamically compatible with both the polymer particles and the organic matrix, can be introduced into the fractions of the polymer particles.

oder $${\text{logP}}_{\text{OW}}{}^{1000}\left(\text{Matrix}\right)>{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{Modifizierung}\right)>{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{Partikel}\right)$$

The polarity of the surface modification lies (expressed as an octanol / water partition coefficient based on 1000 g / mol molecular weight) between the polarity of the polymer particles and the polarity of the organic matrix and serves to thermodynamically adapt the particle surface to the organic matrix and its integration into the organic matrix . $${\text{logP}}_{\text{OW}}{}^{1000}\left(\text{matrix}\right)<{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{modification}\right)<{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{Particles}\right)$$

or $${\text{logP}}_{\text{OW}}{}^{1000}\left(\text{matrix}\right)>{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{modification}\right)>{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{Particles}\right)$$

The ChemSketch software (https://www.acdlabs.com/resources/freeware/chemsketch/) is used to calculate the octanol / water distribution coefficient. The SMILES notation is generated from the chemical structure of the segment or the partial area with a molecular weight (weight average) 1000 g / mol and transferred to the EPI-Suite software. This then calculates the corresponding octanol / water distribution coefficient for the segment or the partial area.

The octanol / water distribution coefficient of polymers or surfaces is calculated from a segment or a partial area with a molecular weight that is closest to the value of 1000 g / mol.

In the case of heterogeneous polymers, e.g. block copolymers, with a number of n segments (S), the octanol / water partition coefficient is calculated for each chemically uniform segment and weighted using the weight fraction (s _n ) of the different segments as follows: $$lOG{P}_{O\mathrm{W.}}{}^{1000}={\text{<figure-callout id="1" label="s" filenames="DE202019103224U1\_0022.png" state="{{state}}">s</figure-callout>}}_1\ast lOG{P}_{O\mathrm{W.}}{{}_1}^{1000}+{\text{<figure-callout id="2" label="s" filenames="DE202019103224U1\_0022.png" state="{{state}}">s</figure-callout>}}_2\ast lOG{P}_{O\mathrm{W.}}{{}_2}^{1000}+\cdots +{\text{s}}_n\ast lOG{P}_{\mathrm{<figure-callout\; id="1000"\; label="O\; W.\; n"\; filenames="DE202019103224U1\_0023.png,DE202019103224U1\_0024.png"\; state="\{\{state\}\}">O</figure-callout>}\mathrm{W.}}{\text{n}}^{}{}^{1000}$$

If the segments have a molecular weight of less than 1000 g / mol, the polymer is considered to be homogeneous with statistically distributed functional groups and the octanol / water partition coefficient is calculated for a representative segment.

In the case of heterogeneous surfaces, e.g. polymer particles with different fillers, some of which are on the surface, with a number of n sub-areas (F), the octanol / water distribution coefficient is calculated for each chemically uniform sub-area and based on the area ratio (f _n ) weighted as follows: $$lOG{P}_{O\mathrm{W.}}{}^{1000}={\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="DE202019103224U1\_0022.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\ast lOG{P}_{O\mathrm{W.}}{{}_1}^{1000}+{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="DE202019103224U1\_0022.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\ast lOG{P}_{O\mathrm{W.}}{{}_2}^{1000}+\cdots +f_n\ast lOG{P}_{\mathrm{<figure-callout\; id="1000"\; label="O\; W.\; n"\; filenames="DE202019103224U1\_0023.png,DE202019103224U1\_0024.png"\; state="\{\{state\}\}">O</figure-callout>}\mathrm{W.}}{\text{n}}^{}{}^{1000}$$

The surface modification is applied in one or more steps as a solid, from solution or dispersion, by spraying, by vapor deposition, by depolymerization or any other suitable method for surface modification. This also includes the modification of the particle surface through mechanical, thermal, chemical or energetic treatment, which results in a surface modification. The surface modification can be crosslinked or not offset in order to ensure a better connection to the particle surface.

The surface modification of the polymer particles can already be carried out during the production of the polymer particles or afterwards in an additional work step (by applying the surface modification to the particle surface), or also "in situ" during the addition of the polymer particles to the organic matrix (selective absorption of the modification on the surface of the particles).

Bimodal or multimodal particle size distribution

The polymer particles are produced in at least two fractions with different particle size distributions, a first fraction having a first mean particle diameter and a second fraction having a second mean particle diameter different therefrom. With two fractions, this creates a bimodal distribution of the polymer particle sizes. By mixing more than two fractions with different particle size distributions, a multimodal distribution of the polymer particle sizes can be generated accordingly.

The bimodal or multimodal distribution of the polymer particles can be produced by the manufacturing process of the particles themselves or by a mixing process (eg mixing with stirring) of two or more particle fractions or by a separation process (eg sieving out certain particle fractions).

The particle size distribution of the first and second fractions can be determined by a known method such as laser diffraction. The number of measuring points should be selected in such a way that the characteristic points of the distribution (maxima and minima) can be determined. The first derivative of the particle size distribution curve of a representative sample determined (e.g. by laser diffraction) changes its sign at least three times over the entire course (from + to - to + to -), with the second derivative of the particle size distribution curve going through zero at least three times, i.e. at least two times Has maxima and a minimum in between. In a multimodal distribution, the number of maxima and minima increases accordingly, as in 2 illustrated.

A (relative) maximum or minimum in the particle size distribution curve is expediently regarded as significant if the distance between the adjacent minimum and maximum (hB1, h11, h12, h22, h23, ..., hxy) is at least 1% of the main maximum (h3B , Distance between the baseline and the highest maximum).

Adsorption time / desorption time

The adsorption time or the desorption time (t _{A / D} in seconds) for the adsorption or the desorption of the polymer particles on or from the low molecular weight substances of the matrix is calculated from the mean particle diameter (d in cm ² ) and the diffusion coefficient (D. _P - in cm ² / s). The calculation of the diffusion coefficient can be based on a reference molecular weight of M _W = 300 Dalton for the low molecular weight substances. Further parameters for calculating the diffusion coefficient are the polymer type, described by its glass transition temperature (T _g in ° C), and the application temperature (T in K).

The diffusion coefficient (Dp) is then calculated as follows: $${\text{D.}}_{\text{P}}={10}^{\mathrm{4th}}\ast \text{EXP}\left[\left(-0.06\ast {\text{T}}_{\text{G}}+2\right)-0.1351\ast {\text{M.}}_{\text{W.}}{}^{2/3}+0.003\ast {\text{M.}}_{\text{W.}}-10545/\text{T}\right]{\text{in <figure-callout id="2" label="cm" filenames="DE202019103224U1\_0022.png" state="{{state}}">cm</figure-callout>}}^2/\text{s}$$

The adsorption time / desorption time is calculated from the diffusion coefficient and the mean diameter of the polymer particles as follows: $${\text{t}}_{\text{A.}/\text{D.}}=1/24\ast {\text{<figure-callout id="2" label="d" filenames="DE202019103224U1\_0022.png" state="{{state}}">d</figure-callout>}}^2/{\text{D.}}_{\text{P}}$$

If the polymer particles consist of a polymer mixture with n (different) polymers, the glass transition temperature of the mixture is calculated from the glass transition temperatures (T _g ) of the n polymers and their weight fraction (x _n ) as follows: $$\frac{1}{T_{G,mix}}=x_1\frac{1}{T_{G\mathrm{,1}}}+x_2\frac{1}{T_{G\mathrm{,\; 2}}}+\cdots +x_n\frac{1}{T_{G,n}}$$

Non-polymeric ingredients e.g. Inorganic solids or low molecular weight substances with a molecular weight <1000 g / mol are not taken into account when calculating the glass transition temperature of the polymer mixture, i.e. the polymer fraction represents the reference weight and the weight fractions of the n polymers are related to it.

Adsorption capacity / desorption capacity

The adsorption or desorption capacity for the adsorption or desorption of the polymer particles on or from the low molecular weight substances of the matrix results from the added amount of polymer particles and the distribution equilibrium of the low molecular weight substances between the organic matrix and the polymer particles. In the case of time-controlled adsorption, the low-molecular ones are Substances in the organic matrix, in the case of desorption, the polymer particles contain the low molecular weight substances and release them to the matrix.

Time to achieve the material property (time to property - t _P )

The response time (t _P in s - "time to property") is the time by which the material property must be achieved for technological reasons.

The effective adsorption or desorption time of a multimodal particle distribution (t _{A / D, efectiv} ) results from the minimum of the individual polymer particle _fractions as follows: $${\text{t}}_{\text{A.}/\text{D.},\text{effective}}=\text{min}\left({\text{t}}_{\text{A.}/\text{D.}\mathrm{,1}},{\text{t}}_{\text{A.}/\text{D.}\mathrm{,\; 2}},...{\text{t}}_{\text{A.}/\text{D.},\text{n}}\right)$$

The effective adsorption or desorption time of a multimodal particle distribution (t _{A / D, efectiv} ) is preferably less than the time to achieve the material property ("time to property" - t _P ) $${\text{t}}_{\text{A.}/\text{D.},\text{effective}}<{\text{t}}_{\text{P}}$$

Release agent

Release agents of any nature and size can be added to the polymer particles in order to enable flowability during storage, transport, processing, dosing, etc. and to be able to process the polymer particles better. The release agents keep the polymer particles in special serial capability. Suitable release agents have e.g. Calcium carbonate, talc, starch, or cellulose, or mixtures thereof have proven.

Processes to influence the rheology of the bitumen mixture:

By adding at least two fractions of surface-modified polymer particles with different particle size distributions to a bitumen matrix according to the invention, the rheology, in particular the viscosity of the bitumen mixture, can be influenced and time-controlled in a targeted manner. The polymer particles absorb, in particular through, low molecular weight substances from the organic matrix Adsorption, or give it up to the organic matrix, in particular by desorption.

The low molecular weight substances can originally be contained in the surface-modified polymer particles or be attached to them and migrate into the matrix by diffusion and become embedded therein. The low molecular weight substances can also originally be contained in the matrix and, after diffusion from the matrix, be absorbed on or in the polymer particles, in particular adsorbed or stored. The diffusion of the aforementioned low molecular weight substances and their uptake in the matrix or on or in the polymer particles takes place in a period of time that is dependent on the diameter of the polymer particles.

Examples

In the following, examples of the invention are shown on the basis of bitumen mixtures that contain a bitumen matrix and surface-modified polymer particles in the form of ground rubber particles from old tires and enable the rubber particles to take up / adsorb low molecular weight substances in the bitumen matrix in a timed manner.

To produce the bitumen mixture, rubber powder fractions are first produced by grinding old tires (truck and / or car tires) with different mean particle diameters. The rubber particles essentially consist of synthetic rubber, natural rubber, carbon black, Silka, oil and processing aids (such as crosslinkers, accelerators, stabilizers, lubricants, etc.). In the 3a , 3b and 3c are examples of the resulting particle size distributions of a first fraction ( 3a) , a second parliamentary group ( 3b) , and a third parliamentary group ( 3c ), with the first fraction in the particle size distribution having an (absolute) maximum with an average particle diameter of approx. 750 µm, the second fraction an (absolute) maximum with an average particle diameter of approx. 400 µm and the second fraction (absolute) ) Maximum at an average particle diameter of approx. 400 µm and the third fraction has an (absolute) maximum at an average particle diameter of approx. 80 µm.

These fractions of rubber powder are made into rubber powder mixtures by mixing two or more such fractions. Examples of the resulting particle size distributions of the mixtures are given in 4a and 4b shown, where 4a shows the particle size distribution obtained by mixing the first and third fractions and 4b shows the particle size distribution resulting from mixing the first and second fractions.

As from the 4a and 4b As can be seen, the particle size distribution of the rubber particle mixtures each have a bimodal distribution with two (relative) maxima of the particle size distribution with a first mean particle diameter and a second mean particle diameter.

In the particle size distribution of 4a a first (upper) maximum is at an average particle diameter of approx. 400 µm and a second (lower) maximum is at an average particle diameter of approx. 80 µm. In the particle size distribution of 4b a first (upper) maximum is at an average particle diameter of approx. 400 µm and a second (lower) maximum is at an average particle diameter of approx. 400 µm.

The weight proportion of the added fractions determines the expression of the (relative) maxima.

The viscosity of bitumen is often too low for road construction applications (e.g. grit, mastic, asphalt, open-pored asphalt). In order to prevent the bitumen from running out of the hot asphalt mixture, the viscosity of the bitumen must be increased. Traditionally, this is achieved by adding finely ground cellulose fibers.

When adding rubber particle fractions with a monomodal particle size distribution consisting mainly of SBR rubber (e.g. recycled car tires) with an average particle diameter dmax = 710 µm and particles <850 µm, it takes approx. 2 hours for the viscosity of the bitumen (organic matrix) to be absorbed of low molecular weight substances increased and reached the final value (cf. ). For the technical processing of asphalt mixtures for road construction, it is sufficient if the viscosity reaches approx. 80% of the final value, which only occurs after approx. 1 to 2 hours when rubber particle fractions with a monomodal particle size distribution are added. However, a period of 1 to 2 hours is far too long for road construction applications, as the asphalt mixture is usually processed within a processing time of approx. 15 - 30 minutes (by mixing, transporting and laying).

$${\text{D}}_{\text{P}}={10}^4*\text{EXP}\left[\left(-0.06*-62+2\right)-\mathrm{0,1351}*{400}^{2/3}*400-10545/453\right]{\text{ in cm}}^2/\text{s}$$

$$\begin{array}{l}{\text{t}}_{\text{A}/\text{D}\text{,SBR}}\left(\text{d}=710\mu \text{m}\right)=1/24*{\mathrm{0,071}}^2/{\text{D}}_{\text{P}}=96\text{ Minuten}\\ =>80\%\text{ der Endviskosität entsprechen}<60\text{ min}.\end{array}$$

$$\begin{array}{l}{\text{t}}_{\text{A}/\text{D},\text{SBR}}\left(\text{d}=400\mu \text{m}\right)=1/24*{\mathrm{0,04}}^2/{\text{D}}_{\text{P}}=54\text{ Minuten}\\ =>80\%\text{ der Endviskosität entsprechen}<30\text{ min}.\end{array}$$

$$\begin{array}{l}{\text{t}}_{\text{A}/\text{D},\text{SBR}}\left(\text{d}=75\mu \text{m}\right)=1/24*{\mathrm{0,0075}}^2/{\text{D}}_{\text{P}}=10\text{ Minuten}\\ =>80\%\text{ der Endviskosität entsprechen}<5\text{ min}\end{array}$$

If, on the other hand, a sufficient proportion (of 20%, for example) of rubber particles with a diameter of <600 µm (d _max = 400 µm) is added to the rubber particles with a diameter of <850 µm (d _max = 710 µm), the result in 4b Shown bimodal particle size distribution of the rubber particle mixture. When this rubber particle mixture is added to the bitumen matrix, the viscosity of the bitumen increases to the level required for good workability within approx. 30 minutes (80% of the maximum final viscosity value). The bitumen mixture can therefore be processed earlier by adding a rubber particle mixture with a bimodal particle size distribution. The following calculations result for the example mentioned: $${\text{T}}_{\text{G}\text{, SBR}}=-62°\text{C.}\left(\mathrm{15th}\%\text{Styrene monomer content}\right);{\text{M.}}_{\text{W.}}=400\text{Dalton; Application temperature T}=453\text{K}\left(180°\text{C.}\right)$$

$${\text{D.}}_{\text{P}}={10}^{\mathrm{4th}}*\text{EXP}\left[\left(-0.06*-62+2\right)-0.1351*{400}^{2/3}*400-10545/453\right]{\text{in <figure-callout id="2" label="cm" filenames="DE202019103224U1\_0022.png" state="{{state}}">cm</figure-callout>}}^2/\text{s}$$

$$\begin{array}{l}{\text{t}}_{\text{A.}/\text{D.}\text{, SBR}}\left(\text{d}=710\mu \text{m}\right)=1/24*{0.071}^2/{\text{D.}}_{\text{P}}=96\text{Minutes}\\ =>80\%\text{correspond to the final viscosity}<60\text{min}.\end{array}$$

$$\begin{array}{l}{\text{t}}_{\text{A.}/\text{D.},\text{SBR}}\left(\text{d}=400\mu \text{m}\right)=1/24*{0.04}^2/{\text{D.}}_{\text{P}}=54\text{Minutes}\\ =>80\%\text{correspond to the final viscosity}<\mathrm{30th}\text{min}.\end{array}$$

$$\begin{array}{l}{\text{t}}_{\text{A.}/\text{D.},\text{SBR}}\left(\text{d}=75\mu \text{m}\right)=1/24*{0.0075}^2/{\text{D.}}_{\text{P}}=10\text{Minutes}\\ =>80\%\text{correspond to the final viscosity}<5\text{min}\end{array}$$

Occasionally, the hot asphalt mixture is temporarily stored in the silo after mixing. In this case too, the bitumen must be prevented from leaking out of the asphalt mixture by sufficiently stabilizing the bitumen. A targeted increase in viscosity in an even shorter time (mixing time approx. 5 minutes) is required here.

The rapid increase in the bitumen viscosity can be achieved by using rubber particle fractions with smaller rubber particles (eg cryogenically ground rubber from recycled car or truck tires). If, in addition to the rubber particles with a diameter of <850 µm (d _max = 710 µm), a sufficient proportion (e.g. 20%, based on the weight) of rubber particles with a diameter of <125 µm (d _max = 75 µm) is used, the in 4a The bimodal particle size distribution shown, with which the viscosity of the bitumen increases to the technically required level (80% of the maximum final viscosity value) within approx. 5 minutes.

In this example, the requirement t _{A / D, effective} <t _P (depending on the requirement profile) is thus met.

If rubber particles made from (mostly) natural rubber are used instead of SBR (e.g. recycled truck tires), the adsorption and desorption times are correspondingly shortened due to the lower glass transition temperature of T _g = -72 ° C.

The adsorption of the low molecular weight substances from the bitumen continues via the proportion of larger particles (in the above example rubber particles with a diameter of <850 µm) even after the asphalt has been laid and leads to a more stable and resilient asphalt surface.

$${\text{log P}}_{\text{OW}}{}^{1000}\left(\text{Bitumen}\right)=38.48$$

$${\text{log P}}_{\text{OW}}\left(\text{Polyoctenamer}\right)=\mathrm{35,65}$$

$${\text{log P}}_{\text{OW}}\left(\text{SBR}\right)=\mathrm{27,57}$$

The surface modification of the rubber particles takes place, for example, with polyoctenamer (Vestenamer ^® 8012, for example, the company. Evonik).

$${\text{log P}}_{\text{OW}}{}^{1000}\left(\text{bitumen}\right)=38.48$$

$${\text{log P}}_{\text{OW}}\left(\text{Polyoctenamer}\right)=35.65$$

$${\text{log P}}_{\text{OW}}\left(\text{SBR}\right)=27.57$$

The choice of material corresponds to the requirement: $$\begin{array}{l}{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{matrix}\text{,Bitumen}\right)>{\text{logP}}_{\text{OW}}{}^{1000}\left(\text{modification}\text{, Polyoctenamer}\right)>{\text{logP}}_{\text{OW}}{}^{1000}(\text{Particles}\text{,}\\ \text{SBR})\end{array}$$

As a release agent e.g. a filler (ground calcium carbonate with a diameter <63 µm) was used.

According to the information given above, bitumen mixtures with different proportions of bitumen and surface-modified polymer particles (rubber powder mixtures) were produced (the percentages in each case relate to the weight proportion of the listed components of the bitumen mixtures or rubber particle mixtures):

Bitumen mixture 1:

• • 90% bitumen
• • 10% surface-modified polymer particles (rubber particle mixture)
• • from that:
  • 20% rubber particles d <125 µm 70% rubber particles d <850 µm 5% Vestenamer (surface modification) 5% calcium carbonate (release agent)

Bitumen mixture 2:

• • 80% bitumen
• • 20% surface-modified polymer particles
• • from that:
  • 70% rubber particles d <125 µm 20% rubber particles d <850 µm 5% Vestenamer (surface modification) 5% calcium carbonate (release agent)

Bitumen mixture 3:

• • 10% bitumen
• • 90% surface-modified polymer particles
• • from that:
  • 45% rubber particles d <600µm 45% rubber particles d <850µm 5% Vestenamer (surface modification) 5% calcium carbonate (release agent)

QUOTES INCLUDED IN THE DESCRIPTION

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Patent literature cited

• WO 2012010150 A1 [0004]
• US 5936015 A1 [0005]

Claims (27)

Bitumen mixture containing a matrix of bitumen, low molecular weight substances and at least one stabilizer to increase the viscosity of the bitumen mixture, characterized in that at least one stabilizer is in the form of surface-modified polymer particles with a multimodal particle size distribution. Bitumen mixture after Claim 1 wherein the polymer particles take up the low molecular weight substances from the bitumen matrix in a controlled manner, in particular adsorb them, or the low molecular weight substances are initially attached to the polymer particles and are successively released to the bitumen matrix by desorption. Bitumen mixture after Claim 1 or 2 , wherein the polymer particles are rubber particles, in particular ground rubber particles. Bitumen mixture according to one of the preceding claims, characterized in that the particle size distribution of the polymer particles has at least a first relative maximum with a first mean diameter of the polymer particles and a second relative maximum with a second mean diameter of the polymer particles and in the particle size distribution of the polymer particles between the first mean diameter and the second mean diameter has a factor of at least 1.2, preferably of at least 1.5 and particularly preferably of at least 2. Bitumen mixture according to one of the preceding claims, characterized in that the fraction of polymer particles with the smallest mean particle diameter has a weight fraction of 0.1 to 99.9% by weight, preferably 5 to 95% by weight and particularly preferably 10 to 90% by weight .-% of the total weight of the bitumen mixture. Bitumen mixture according to one of the preceding claims, characterized in that, from the time the surface-modified polymer particles are added to the bitumen matrix, a time-controlled modification of the viscosity of the bitumen mixture is achieved within a technologically predetermined setting time (time to property, t _P ). Bitumen mixture after Claim 6 , the viscosity being modified within an absorption or adsorption time (time of absorption or desorption, t _{A / D} ), which depends on the glass transition temperature and the particle diameter of the polymer particles, and the absorption or adsorption time (t _{A / D} ) is less than the specified response time (t _P ). Bitumen mixture according to one of the preceding claims, characterized in that the proportion by weight of the polymer particles is between 0.1 and 99% by weight, preferably 10 to 90% by weight and particularly preferably 10 to 80% by weight. Bitumen mixture according to one of the preceding claims, characterized in that the polymer particles have a surface modification whose polarity, expressed as log P _OW ^1000, lies between the polarity of the unmodified polymer particles and the bitumen matrix. Bitumen mixture according to one of the preceding claims, characterized in that it contains release agents in order to keep the polymer particles free-flowing. Bitumen mixture according to one of the preceding claims, characterized in that the low-molecular substances originally contained in the surface-modified polymer particles or are attached to them and migrate into the bitumen matrix by diffusion and have become embedded therein. Bitumen mixture according to one of the preceding claims, characterized in that the low-molecular substances are originally contained in the bitumen matrix and have been deposited on or in the polymer particles by diffusion, in particular adsorbed or embedded. Bitumen mixture according to one of the preceding claims, characterized in that the surface-modified polymer particles contain a core made of a first polymer material and a shell surrounding the core made of a second polymer material different from the first polymer material. Bitumen mixture according to one of the preceding claims, characterized in that the particle size distribution of the polymer particles has at least a first and a second relative maximum of the particle size, the ratio of the mean particle size of the second relative maximum to the first relative maximum being at least 2. Bitumen mixture according to one of the preceding claims, characterized in that the particle size distribution of the polymer particles has a bimodal or multimodal particle size distribution with a plurality of relative maxima of the (mean) particle size, the smallest mean particle size in the particle size distribution of the polymer particles in the range from 50 to 150 µm and in particular is 70 to 80 µm. Bitumen mixture after Claim 15 , the relative maximum following the smallest mean particle size in the particle size distribution of the polymer particles having a mean particle size in the range from 180 to 250 μm and in particular being 200 μm or more. Bitumen mixture according to one of the preceding claims, characterized in that the particle size distribution of the polymer particles has at least a first and a second relative maximum, the mean particle size of the first relative maximum in the range from 50 to 150 µm and in particular 100 µm and the mean particle size of the second relative maximum is above 200 µm. Bitumen mixture after Claim 17 , wherein the distance between the peak height of a relative minimum and the peak height of the two relative maxima surrounding the minimum is at least 5% of the value of the peak height of the highest relative maximum. Bitumen mixture according to one of the preceding claims, wherein the fraction of the polymer particles which has a particle size distribution with the smallest relative maximum of the (mean) particle diameter has an area proportion of 0.1 to 99.9% based on the total area of the curve of the particle size distribution and preferably one Has an area proportion of 5 to 95% and particularly preferably from 10 to 90%. Bitumen mixture according to one of the preceding claims, wherein the weight fraction of the polymer particles in the total weight of the bitumen mixture is between 0.1 and 90% by weight, preferably between 0.5 and 70% by weight and particularly preferably between 1 and 50% by weight . Bitumen mixture according to one of the preceding claims, wherein the bitumen matrix contains polymer-modified bitumen (PmB). Bitumen mixture according to one of the preceding claims, the viscosity adjusting to a final equilibrium value within a predetermined equilibrium period from the addition of the polymer particles. Bitumen mixture after Claim 22 , the viscosity being adjusted to at least 80% of the final equilibrium value within half the equilibrium period from the addition of the polymer particles. Bitumen mixture after Claim 22 , the viscosity settling to 80% of the final equilibrium value within a period of 30 minutes or less from the addition of the polymer particles. Bitumen mixture after Claim 23 , the viscosity adjusting to 80% of the final equilibrium value within a period of 10 minutes or less from the addition of the polymer particles. Bitumen mixture according to one of the Claims 22 to 25th , the equilibrium period being between 5 minutes and 60 minutes. Asphalt mixture, in particular stone mastic asphalt, containing a bitumen mixture according to one of the preceding claims.

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