GB1584541A - Method of adding ingredents to a bituminous material - Google Patents

Description

(54) METHOD OF ADDING INGREDIENTS TO A BITUMINOUS MATERIAL (71) I, PAUL HABERL, a National of Canada and Austria of Klein Wolkersdorf 129, A-2821, Austria do hereby declare the invention, for which I pray that a Patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a particulate material of construction containing synthetic, thermoplastic, polymer particles to whose surfaces at least one material adheres.

It is frequently required in various branches of construction work to admix one or more agents in a predominant basic component in precisely determined amounts in the most homogeneous distribution possible. Such addition agents for concrete include setting accelerators and retarders, fillers- for increasing the porosity or for modifying the thermal and/or acoustical insulating properties. Addition agents for soil or road surfaces serve for improving adhesion of a bituminous binder to mineral components and other fillers, for improving the fluidity or for modifying the foaming characteristics of the mixture etc.

It was necessary heretofore to add such agents, which are frequently used in combinations to the basic component, in a certain sequence and under precisely controlled conditions, particularly at controlled temperatures and humidities, and within a predetermined time.

Difficulties were encountered frequently, particularly during-use of combinations of addition agents, because some agents are difficult to distribute uniformly in the basic component and, therefore, require a mixing period of certain minimum length. This applies particularly to viscous basic components such as asphalt and other bituminous masses of the type employed for road construction and as floor coverings. The processes employed heretofore for incorporating addition agents are time consuming, a fact which unfavorably affects the cost of the mixing operation, but also the quality of the resulting mixture because some addition agents, such as thermoplastic synthetic resin compositions, are sensitive to elevated temperatures, particularly if exposed to such temperatures for extended periods of time.Lengthy heating periods, however, are often unavoidable for the reasons presented above.

It is an object of this invention to avoid the aforedescribed shortcomings and difficulties inherent in known procedures, and to facilitate the admixture of even a multiplicity of addition agents to a predominant basic component.

Accordingly, the present invention provides a method of adding a measured amount of at least one agent to a basic component of a bituminous material which comprises: (a) mechanically comminuting a plurality of unitary bodies of a synthetic, thermoplastic, polymeric material until each of said bodies is converted to a multiplicity of particles and said particles are heated by said comminuting to a temperature at which the surfaces of said particles are tacky; (b) contacting the tacky surfaces of said particles with said amount of said at least one agent and thereby bonding said at least one agent to said surfaces as a surface coating, said amount being smaller than the weight of said particles; (c) cooling the coated particles below said temperature; and (d) thereafter substantially uniformly dispersing the coated particles in said basic component.

The polymer particles thus provide carriers for the addition agent. Addition agents thus may be incorporated in the basic component in any desired combination by means of the polymer particles and distributed in the basic component by means of the polymer particles without encountering the aforedescribed difficulties. The polymer particles do not adversely affect the properties of the basic component, and may actually be desirable in most cases, for example in the construction of roads or floor coverings, for improving the properties of the resulting mixtures.

Polymer particles carrying other materials as adhering impurities are known. Because the impurities are present in uncontrolled quantity and quality, the effect of the particles on the properties of a material to which they are added is not predictable. This invention makes it possible to control the properties of a basic construction material mixed with the polymer particles and the adhering addition agents in any desired manner, in the simplest case, by measuring the amount of the added polymer particles which carry a known or measured amount of addition agent. This procedure obviates difficulties that may arise from the fact that several addition agents simultaneously added may differ in shape and state of matter, for example, be solid, liquid, angular or round, of different particle size and temperature.The effects of these differences are eliminated or at least mitigated by the fact that the several addition agents are bound to polymer particles, whereby admixture to the basic component is facilitated and the proper time at which the addition agents are added to the basic component is readily selected.

No difficulties are encountered in working with addition agents which are not normally solid at ordinary temperature. It is readily possible within the scope of the invention to coat the polymer particles over substantial, extended portions of their surfaces with a layer of the addition agent, and such a layer may be continuous. It is possible in this manner to incorporate, for example, latex or polychloroprene into the basic omponent. The surface layer may also consist of juxtaposed, finely divided granular particles, such as chalk, cellulose and powdered limestone. Because the coating particles adhere to the surface of the polymer particles, the coating particles are not stripped off during storage, during transportation or during mixing of the polymer particles with the basic component.The finely granular coating particles may consist of organic materials, for example, sawdust, but also of inorganic materials, for example sand, silicates, or metal powder.

It is a particular advantage of this invention that waste materials not otherwise capable of being disposed of or of being utilized may be incorporated in a basic component of a material of construction to exert on the same a beneficial effect. This is possible, for example, with natural or synthetic rubber or rubber-bearing materials which have a favorable effect on road or floor surfacing materials to which they are admixed. Such rubber waste may consist, for example, of comminuted automotive tires. It is possible to cover the polymer particles according to the invention entirely or in part with a layer of rubber.

It is not necessary for performing this invention that the polymer particles have any particular shape, such as that of a sphere or cube, although such shapes are readily prepared by granulation. It is also possible according to the invention that the polymer particles consist of thermally shrunk foils and be provided with interior voids, formed e.g. by parts of the foils sticking to each other while tacky from the effects of the heating, enclosing other materials including the addition agent or agents. It is readily possible in this manner to incorporate, in a basic component, addition agents which are in the liquid state. According to the invention, the voids may contain at least one liquid, particularly water, oil, salt solutions, emulsions or natural or synthetic rubber, such as polychloroprene.The addition agents of the invention, of course, may also include salts, amines, or fatty acid derivatives, but they may also include bitumen, natural asphalt or pitch. These materials are generally tacky, but their tackiness may be remedied by further coating with another material, for example, a coating of rubber or latex.

Suitable synthetic, thermoplastic, polymeric materials or plastics include synthetic resin compositions, particularly polyolefins, preferably polyethylene and polypropylene, but also polystyrene, polyester and polyvinyl chloride. Thermoplastic materials have the advantage that adhesive bonding thereof to the addition agents proper can be brought about by heating the polymer particles. Another bonding effect may be achieved with all polymers by treatment of the polymer surfaces with suitable solvents. The polymer particles need not consist of virgin material because plastic scrap, particularly regenerated plastic, may be employed to advantage. The individual particles of the plastic may be colored which permits different products to be identified by suitable coloring, also by selection of the particle shape and size to avoid confusion. Compositions prepared in the form of dusting materials of different particle sizes may be added in a particularly simple manner to basic components of materials of construction.

A method of the invention for producing the coated carriers of the invention is characterized in that polymeric material, preferably in the form of foil, is comminuted, and its surface is rendered tacky by the heat generated from the comminution, whereupon the material is mixed with the addition agent in the tacky condition. As mentioned above, heating causes the surface of a thermoplastic synthetic resin composition to become tacky which is generally sufficient for providing adequate adhesive bonding of the addition agent proper. If such bonding cannot be achieved adequately, the surface may be rendered more adhesive by contacting with a suitable solvent.It is particularly simple, according to the invention, to comminute a polymeric material in a vessel by means of rotating blades, to raise the material temperature thereby at least to a condition of surface tackiness, but not far beyond the softening temperature, and to cool the polymer material after mixing with the addition agent.

Such cooling preferably occurs suddenly, preferably by introducing water into the vessel. The water practically instantaneously chills the plastic particles after they had been heated to the limit of their softening range by the energy input of the motor driving the comminuting devices so that the particles are prevented from adhering to each other.

The addition agent may be introduced into the vessel jointly with the plastic to be comminuted, but it is preferably introduced only after the polymer has reached a state of tackiness. The added amount of water generally is evaporated in the vessel and during discharge of the treated material by the stored thermal energy of the comminuted material, but it is within the scope of the invention to retain a portion of the water in the plastic particles. This may be of advantage if the addition agent is an aqueous latex emulsion whose water content is partly retained in the coated particles.This aqueous residue evaporates during introduction of the particulate composition into the normally hot basic component, such as bitumen or asphalt, and the residual water fraction, whose amount is readily controlled, is utilized for improving the mixing process and for improving the workability of the mixture by means of road building equipment. Water also favorably affects manual working of the mixture. The application of floor and road coating compositions based on bituminous materials (melted asphalt, rolled asphalt, cement-asphalt mixtures) is facilitated by the evaporating water, and the productivity of labor is increased beyond that already achieved by the use of the polymer material.

As mentioned above, the coated polymer particles of the invention may be applied in numerous branches of construction work. By way of example, polychloroprene, a synthetic rubber, may be introduced into heated bituminous road building compositions in the form of latex in a simple manner. As is well known, polychloroprene and natural rubber not only resist aging, but also elevated temperatures up to 2600 C.

The -last-mentioned temperature is not readily avoided during modification of heated bituminous compositions by means of addition agents.

Rubber, as an addition agent, also may be dissolved in oil. Because bitumen consists of asphaltenes and malthenes, the oily phase of the bitumen is then coupled or combined with another oily phase, whereby wetting of the mineral fillers present is improved. The rubber addition to the bituminous basic component increases toughness and adds elasticity to the normal plasticity of the mixed material. The tendency of a bituminous material to crack at very low temperatures is reduced by the rubber addition, and continuous loadability under dynamic loading is improved.

Whereas adding rubbery or oily substances to a bituminous base created problems heretofore both as to dosage and as to homogeneous distribution of the addition agent in the bitumen, the invention permits easy and precise dosage because the amount of oil or rubber secured to the polymer particles is readily controlled. Because no significant difficulty is encountered in distributing the granular polymer particles in heated bitumen with adequate homogeneity, the addition agents adhering to the polymer particles are distributed in a corresponding homogeneous manner. The same advantage is available relative to adhesion enhancing agents and other addition agents which are employed in bituminous road building material, such as amines, salts, and fatty acid derivatives.

The addition agents may be admixed to bituminous basic components by means of dosing equipment conventional in asphalt plants when carried by polymer particles of the invention because an adequately precise dosing of the granular, freely flowing material does nowt present any problem. The adhesiveness of a bituminous binder to mineral aggregate and other mineral ingredients (fillers) may be improved significantly by this invention.

Other fields of application of the coated polymer particles of the invention reside in the addition of agents for improving the fluidity of the bituminous mixture during construction, of agents for controlling foaming of the mixture, of agents for reducing the working temperature, etc.

These addition agents may be applied to the carrier material (that is, the polymer particles) in greatly different amounts and in combinations adapted for the intended use, and mixed homogeneously with the basic component without tending to separate.

The material of the invention is capable of practically unlimited storage without loss of dusting or flowing properties. Because the coating of addition agent adheres firmly to the polymer particles, the addition agent or agents cannot be stripped from the polymer particles by the effects of humidity, for example by rain.

Many liquids may be used according to the invention as addition agents for basic compo nents of material of construction. Because most polymers are insensitive to many acids and alkaline materials, such active chemical agents may be bonded to the polymeric carrier material without damaging the latter, and may be incorporated in the basic component in this manner, not being harmful thereafter. For example, the surfaces of polyolefin particles (particularly polyethylene) are readily coated with waste oil which may contain dissolved or finely dispersed rubber. Each polymer particle is coated over a major portion of its surface with a layer of oil or rubber and is not tacky. In this manner, the sticking of adjacent particles can be avoided even when substances tacky in themselves are used.

As mentioned above, the polymer particles of the invention may be produced by granulating, but it is particularly advantageous to use shrunk foil particles, so-called agglomerates, because they have a large surface area and are additionally formed with voids in which the addition agent or agents may be retained. Such agglomerates are formed when foils of shrinkable plastic, particularly polyethylene are torn and thermally shrunk. The applied heat causes not only shrinking of the foil pieces, but tackiness of the particle surfaces, whereby addition agents mixed with the agglomerate particles are readily bonded adhesively.

EXAMPLE 1 A cylindrical vessel having a diameter of one meter and a vertical axis was equipped with eight stationary knives or blades attached to the cylindrical wall and two rotating knives or blades mounted on a coaxial shaft driven at 1600 RPM. Polyethylene foil in the form of bags and other foil scrap which was partly soiled was introduced into the vessel and cut and torn by the knives. The pieces of foil were heated by the cutting action. At about 900C, the surfaces of the foil pieces started melting and tended to stick to each other. From this point, the temperature was permitted to rise a few more degrees whereupon latex was sprayed into the vessel. The foil fragments shrunk to agglomerates at this stage were chilled by the cold latex, the agglomerates cracked and were broken up so as to be reduced to a granular state.The latex was joined to the individual, partly softened foil fragments, and a portion of the water present in the latex was vaporized with simultaneous cooling of the polyethylene. The steam so formed was extracted until the residual mdisture in the vessel reached a desired degree.

The surfaces of'the resulting agglomerate fragments were found to be coated entirely or almost entirely by a layer of congealed latex or rubber and were not tacky. The latex layer firmly adhered to the polyethylene particles. The voids of each particle still contained some water in the form of unchanged latex sealed in by a rubber layer. The product could be packed in bags and stored for further use. It was eminently suitable for improving the properties of hot asphalt or other bituminous material with which it mixed readily.

The particle size and shape of the material of this invention may be varied. Generally, the particles have a size of a few millimeters, at least 1 and up to 10 mm. The shape of the particles is irregular if they were formed from foil agglomerates. When granular material is to be employed, it may be prepared by conventional granulation. The dimensions of the particles are approximately the same regardless of the manner of production, and of the order of several millimeters, not exceeding one centimeter.

EXAMPLES 2 TO 5 According to the method described in Example 1, a series of addition substances of rubberor latex-coated particles of polyethylene foil with different proportions of rubber and latex were manufactured. The percentage values given in the following table represent parts by weight of natural rubber or latex (without any water component) with respect to the weight of polyethylene: Example

2 10% Natural rubber (polyisoprene) 3 Baypren late 20% 4 25Y0 Baypren latex B-58 (Baypren is a registered Trade Mark) of Bayer A.G.

5 40% The natural rubber was added in dry finely-divided form, and the latex as emulsion, comprising 50% latex and 50% water, to the polyethylene during the melting process. In the latter case, the water was evaporated to about 5 residual moisture so that the polyethylene particles were covered or fused with almost pure latex.

EXAMPLES 6 TO 16 The addition substances produced in accordance with examples 2 to 5, forming a fluid granulated material, were added in different proportions to a bitumen of Type B-80 from Shell A.G. and mixed therewith, while being stirred, for over one hour at a temperature of 175 C; The percentages set forth in the following table represent the proportions by weight of the mixed addition substances with respect to the weight of bitumen.

Example

6 3% 7 5% tv addition substances according to Example 2.

8 10% 9 3% 10 5% addition substance according to Example 3.

11 10% 12 3% 13 5% addition substance according to Example 4.

14 10% 15 3% addition substance according to Example 5.

16 5% The bituminous masses of the above Examples were investigated with respect to their qualities using standard methods. The following measurements were thus determined: Penetration: The penetration is defined by the number of 1/10 min. through which a needle loaded with 100 g penetrates at 25"C or 0 C in 5 secs. into the bitumen (DIN 52 010).

Softening point - ring and ball: The softening point is that temperature at which a bitumen layer, under predetermined conditions, with uniform heating, undergoes a predetermined deformation by a superimposed steel ball (DIN 52 011). At the softening point temperature (RUK), the bitumen always has a penetration value of 800.

Ductility: In the determination of the ductility, a test body is stretched under predetermined conditions and at a constant drawing speed (5 cm/min) at a testing temperature of 4"C until the breakage of the resulting filament. The ductility is the elongation of the test body in cms.

which is thereby reached (DIN 52 013).

Breaking point: The breaking point is that temperature at which a binder film of the above-described thickness, fused onto a test plate, ruptures at the above-described cooling speed and bending stress (DIN 52 012).

Toughness and Tenacity: The determination of the toughness and tenacity is effected by the so-called Tenacity Toughness Test on the basis of a pulling test. For this, a device is used by which a spherical steel head having a diameter of 3/4 inch, which is fixed to a threaded shaft, is entirely embedded in the bitumen. The entire device is then maintained at 250C for at least 12 hours.

The hemisphere is then drawn from the bitumen, using an electronic pulling machine, at a speed of 12 inch/min. The stress-strain curve is automatically recorded and the value of the tenacity is determined by measuring the area under the curve by means of a planimeter. The toughness is the work represented by the entire area under the curve, while the tenacity is represented by the area defined by a predetermined portion of the curve at high strain values.

This method was developed by the Du Pont company. In the following table, the toughness and tenacity are given in Newton-mm.

Elasticity: The elasticity value determined by the so-called "torsional-recovery test," which was likewise developed by the Du Pont company, represents a measurement of.the torsional modulus of the bitumen material. An arrangement comprising a disc and a shaft is supported on a non-corroding container which holds 120 g. The melted bitumen is cast in the container until the surface of the bitumen coincides with the surface of the disc. Before the beginning of the test, the apparatus is held at 250C for at least two hours. By rotating and pulling the nut on the shaft, the disc is uniformly rotated through 1800 and suddenly released. The recovery is measured after 30 secs. and 30 mins. The measurements are expressed as the percentages of the recovery.

Flow length: In this test, test bodies of bitumen, positioned on a surface inclined at 750, are exposed for an hour to an increased temperature. The number of mm through which the bitumen flows serves as a measurement of the flow deformation. By the addition of suitable types of rubber, the flow deformation can be reduced to a minimum.

In Table I, the measurement values obtained in accordance with the above-described definitions for both a B-80 bitumen without any addition substances and also for bituminous masses according to Examples 6 to 12 are set forth.

The measurement results show that the admixture of polyethylene and rubber produces considerable advantages. above all, in the flow deformation (flow length).

Table 1 Example Penetra- Softening Ductility Breaking Toughness Tenacity Elasticity (%) Flow length mm tion Point Point 25 C 0 C R u. K - C N.mm N.mm 30 sec. 30 min. 38 C 49 C 60 C C Bitumen B-80 52 13 51 7 12 4.2 2 12.2 13.9 20 55 140 6 62 15 52 6 6 4.4 - 11.1 13.9 10 51 125 7 63 16 56 6 6 4.3 - 11.7 14.5 9 35 114 8 51 18 64 3.5 5 2.0 - 13.9 18.9 0 0 0 9 58 10 53 6.5 11 5.0 - 11.7 13.3 7 48 140 10 41 7 58 6 12 5.4 - 11.7 16.1 5 19 102 11 29 11 67 6.5 18 2.2 0.3 12.2 17.2 0 3 7 12 41 10 60 5 19 3.6 - 5.6 11.1 2 19 83 13 40 40 61 4 20 4.0 - 11.7 16.1 0 0 0 14 36 9 95 6.5 18 2.2 - 8.9 11.1 0 0 0 15 23 7 67 0.5 10 4.1 - 8.3 13.9 0 0 29 16 30 7 66 0.5 20 2.6 0.2 13.9 18.9 0 7 34

Claims (14)

WHAT I CLAIM IS:

1. A method of adding a measured amount of at least one agent to a basic component of a bituminous material which comprises: (a) mechanically comminuting a plurality of unitary bodies of a synthetic, thermoplastic, polymeric material until each of said bodies is converted to a multiplicity of particles and said particles are heated by said comminuting to a temperature at which the surfaces of said particles are tacky; (b) contacting the tacky surfaces of said particles with said amount of said at least one agent and thereby bonding said at least one agent to said surfaces as a surface coating, said amount being smaller than the weight of said particles; (c) cooling the coated particles; and (d) thereafter substantially uniformly dispersing the coated particles in said basic component.

2. A method as claimed in claim 1, wherein said particles are cooled by contact with water.

3. A method as claimed in either claim 1 or claim 2, wherein the surfaces of said particles are also contacted with a solvent in order to render their surfaces more adhesive.

4. A method as claimed in any one of claims 1 to 3, wherein contact between said at least one addition agent and said particles is prevented until said surfaces are tacky.

5. A method as claimed in any one of claims 1 to 4, wherein said at least one addition agent includes an elastomer dispersed as a latex in an aqueous medium, a portion of the water in said latex being retained in the coated particles, and the remainder of said water being evaporated from the coated particles prior to said dispersing.

6. A method as claimed in any one of claims 1 to 4, wherein said at least one addition agent includes a finely divided granular material selected from sawdust, cellulose, sand, silicates, chalk, limestone, and metal.

7. A method as claimed in any one of claims 1 to 4, wherein said at least one addition agent includes rubber.

8. A method as claimed in any one of claims 1 to 7, wherein said particles are thermally shrunk foil fragments enclosing voids.

9. A method as claimed in claim 8, wherein a liquid selected from water, oil, salt solution and an aqueous dispersion of a rubber is contained in said voids.

10. A method as claimed in any one of claims 1 to 9, wherein said at least one addition agent also includes a salt, an amine, or a fatty acid derivative.

11. A method as claimed in any one of claims 1 to 9, wherein said at least one addition agent further includes bitumen, asphalt, or pitch.

12. A method as claimed in any one of claims 1 to 11, wherein said polymeric material includes coloring matter.

13. A method as claimed in any one of claims 1 to 12, wherein the synthetic polymeric material consists essentially of polyolefin.

14. A method as claimed in any one of claims 1 to 13 and substantially as hereinbefore described.