Chemically Modified Bitumen Composition

This invention relates to asphalt reinforced materials, and more particularly to glass fibers treated with chemically-modified asphalts to promote compatibility between glass fibers and asphalt in the manufacture of glass fiber-reinforced asphalt systems.

In recent years, increasing attention has been given to the use of reinforcement of asphalt systems as provided by glass fibers. One of the problems which has been incurred in integrating glass fibers with asphalt as a reinforcement stems from the fact that glass fibers or fragments of glass have smooth, hydrophilic surface characteristics. Thus, the smooth, hydrophilic surfaces of the glass fibers make it difficult to establish any bond, either chemical or physical, between the glass fibers and the asphalt system in which the glass fibers are distributed as reinforcement. In fact, as the highly hydrophilic characteristics of the glass fibers are formed, a thin film of moisture which serves to destroy any chemical or physical bond which might otherwise be formed between the glass fiber surfaces and the asphalt.

The problem of establishing a secure bonding relationship between the glass fiber surfaces and the asphalt is not aided by the chemical nature of the asphalt. Asphalt is a cementitious material containing predominantly bitumens occurring in nature or obtained as a result of the refining of petroleum. Chemically, the asphalt is made up of condensed hydrocarbon rings, and thus is highly hydrophobic in nature, thereby further causing incompatibility with the hydrophilic glass fiber surfaces.

It has been determined that the condensed hydrocarbon ring of asphalt does contain various reactive groups, notably carbon-to-carbon double bonds, carboxy groups and hydroxy groups. These groups, however, do not measurably affect the hydrophobic characteristics of asphalt systems. It has been proposed, in U.S. Pat. No. 4,036,661, to integrate asphalt with mineral aggregate by adding to the asphalt an organo silicon compound, and preferably one derived from an organo silane in which the organic group contains one or more functional groups such as an amino group, an aminoalkyleneamino group, a glycidoxy group, a hydrocarbyl group, an acyloxy group or a mercapto group. The difficulty in the approach described by the foregoing patent stems from the fact that organo silanes of the type taught therein are extremely expensive, and thus large quantities would necessarily be used in the construction of an asphalt road containing such silanes. Thus, the procedure proposed is economically unattractive.

It is accordingly an object of this invention to provide treated glass fibers for use in the reinforcement of asphalt systems to integrate the glass fibers with the asphalt in an efficient and economical manner.

It is a more specific object of the invention to provide glass fibers which have been treated with a chemically-modified asphalt so that chromium complexes are chemically reacted with the asphalt in such a manner as to establish a chemical bond between the chemically-modified asphalt and the glass fiber surfaces.

These and other objects and advantages of the invention will appear more fully hereinafter, and, for purposes of illustration and not of limitation, an embodiment of the invention is shown in the accompanying drawings wherein:

FIG. 1 is a flow diagram showing the manufacture of continuous glass fibers and their treatment in forming according to the practice of this invention;

FIG. 2 is a flow diagram illustrating the treatment of glass fibers in the form of bundles according to the practice of this invention;

FIG. 3 is a cross sectional view of glass fibers treated in accordance with the flow diagram of FIG. 1; and,

FIG. 4 is a cross sectional view of a bundle of glass fibers treated in accordance with the flow diagram of FIG. 2.

The concepts of this invention reside in the treatment of glass fibers with a chemically-modified bitumen composition to form a coating on the glass fibers, either a thin film coating on the individual glass fiber filaments and/or a coating in the form of an impregnant of bundles of glass fibers. The coating of the chemically-modified bitumen is formed of a bitumen which has been reacted with an organic chromium complex, and preferably a complex containing at least one organic group having a functional group reactive with the asphalt.

The chromium complexes preferred for use in the practice of this invention are the well-known Werner complexes formed of a carboxylato group coordinated with a nuclear trivalent chromium. Such compounds are themselves known to the art and are described in U.S. Pat. Nos. 2,544,667 and 2,683,156. The preferred Werner complex compounds used in the practice of this invention are those having the formula: ##STR1## wherein R is the residue of the carboxylato group used to prepare the Werner complex compound.

In the preferred practice of this invention, R is either an alkenyl group containing 2-10 carbon atoms (e.g., vinyl, allyl, etc.) or a saturated aliphatic or alkyl group containing 1-15 carbon atoms and is substituted by a functional group which is reactive with the asphalt. Generally, the functional group substituting the alkyl group is an amino group, a mercapto group, or a hydroxy group, each of which is reactive with carboxy groups present in the bitumen. In addition, the alkyl group can be substituted with an epoxy group. In that event, the R group has the formula: ##STR2## wherein y is an integer ranging from 1 to 5.

The symbol X of the Werner complex compound is halogen, and is preferably chlorine.

Without limiting the present invention as to theory, it is believed that the functional group of the chromium complex becomes chemically bonded to the bitumen, thereby leaving the reactive chromium halide portions of the molecule to react with the highly hydrophilic surfaces of the individual glass fiber filaments to thereby chemically intertie the modified bitumen to the glass surfaces. That effect may be illustrated by reference to the following: ##STR3##

As can be seen from the foregoing equation, a Werner complex, such as that derived from acrylic acid, is reacted with asphalt at an elevated temperature whereby the ethylenic unsaturation of the complex becomes chemically intertied with ethylenic unsaturation contained in the asphalt. The highly acidic chromium atoms remain free to react with the glass fiber surfaces and thereby chemically bond the chemically-modified bitumen to the glass fiber surfaces.

When use is made of a Werner complex compound in which R is an alkyl group substituted with a functional group as described above, a similar type reaction occurs whereby the reactive functional group becomes chemically bonded to the carboxyl groups present in the bitumen.

It has been found that glass fibers treated in that manner can thereafter be employed as reinforcement for bitumens such as asphalt in a variety of applications, including road paving applications, roofing applications and the like. Thus, it is necessary to use only sufficient quantities of the expensive organo silanes to chemically modify the bitumens applied as a coating to the glass fibers. The bitumen coating on the glass fibers, in turn, can be securely integrated with bitumens or bitumens and aggregate whereby the chemically-modified bitumen coating on the glass fibers serve to securely intertie the glass fiber surfaces to the bitumen in which the glass fibers are distributed.

The concepts of this invention are not limited to use with glass fibers. In general, the concepts of this invention can be used in the treatment of natural or synthetic hydrophilic fillers and/or reinforcements in which the filler and/or reinforcement is present in the form of discrete particles. Included are fibers formed of such natural and synthetics such as polyvinyl alcohol, cellulose, as well as filler materials such as glass flake.

The use of the concepts of the present invention with glass flake represents a particularly desirable embodiment of the invention. Thus, glass flake, discrete glass platelets can be admixed with the chemically-modified bitumens such as the chemically-modified asphalt in accordance with the concepts of this invention and then used in road paving and roofing applications. The glass flake tends to migrate within the asphalt to form a barrier layer of overlapping glass platelets, which in turn serves as a moisture-impervious membrane. This concept can be particularly advantageous when applied to road paving applications since the glass flake membrane serves to prevent moisture from permeating the asphalt road bed. The result is that there is less moisture under the surface of the asphalt to cause damage to the asphalt road bed through freezing.

The reaction between chemically-modified asphalt and the functional chromium complexes as described above is preferably carried out by dispersing the asphalt in an aromatic solvent inert under the reaction conditions (i.e., benzene, toluene, xylene, etc.) and then adding the complex. Best results are usually achieved when the reaction is carried out at a temperature ranging from 70.degree. to 200.degree. C. Proportions between the complex and the asphalt are not critical and can be varied within relatively wide limits. In general, it is preferred that the amount of the chromium complex be an amount within the range of 0.001 to 5% by weight based upon the weight of the asphalt.

As indicated, the chemically-modified asphalt composition can be applied as a coating to the individual glass fiber filaments, preferably as they are formed. Referring now to FIG. 1, there is shown a schematic flow diagram illustrating the treatment of glass fibers in accordance with one embodiment of the invention. As shown in this figure, glass is melted in a furnace 10 having a bushing 12 on its bottom side. The bushing is provided with a plurality of openings extending therethrough and the molten glass flows gravitationally through the small openings to form streams 14 which are rapidly attenuated to form fine glass filaments 16 by winding the filaments about a rapidly rotating drum 20.

The filaments 16 may be coated as they are formed with the chemically-modified asphalt composition, preferably dissolved in a solvent, as they are gathered to form a strand 18. For this purpose, use can be made of an applicator 22, illustrated as a wiping pad constantly wet with the chemically-modified asphalt treating composition.

The resulting strand is shown in FIG. 3 of the drawing, where it is illustrated that the individual glass fiber filaments 16 contain the chemically-modified asphalt composition as a thin film coating 24 on the individual surfaces of the glass fiber filaments. The coated glass fibers can be used directly as reinforcement for asphalt or asphalt plus aggregate in accordance with a known manner. The coated glass fibers are thus distributed as reinforcement in asphalt alone or asphalt blended with aggregate. The asphalt or asphalt plus aggregate thus serves as a continuous phase within which the glass fibers coated with the chemically-modified asphalt are distributed. The amount of the chemically-modified asphalt applied as a coating can vary within wide limits. Generally, the coating is applied to the individual glass fiber surfaces in an amount sufficient to constitute from 0.1 to 40% by weight of the weight of the glass fibers.

Alternatively, the glass fibers can be formed into yarns, strands, cords, woven and non-woven fabrics, etc., known in the art as bundles, and then subjected to impregnation. For this purpose, use can be made of untreated glass fibers or glass fibers which have been sized with any of a variety of well-known size compositions. As is well known to those skilled in the art, it is frequently the practice, in the processing of glass fibers in the form of bundles, to employ glass fibers which have been sized whereby the size composition imparts lubricity of the individual glass fiber filaments without destroying their fibrous characteristics. In that manner, the glass fibers can be processed in bundle form without risk of destruction of the glass fibers through mutual abrasion.

In accordance with this embodiment of the invention, a glass fiber bundle is impregnated with the chemically-modified asphalt composition whereby the impregnant serves to coat the individual glass fiber filaments and to completely fill the interstices between the glass fiber filaments forming the bundle and thereby define a unitary bundle structure. Apparatus for that purpose is illustrated in FIG. 2 of the drawings wherein the glass fiber bundle is advanced over a guide roller 34 for passage downwardly into a bath 35 containing the chemically-modified asphalt composition. Once in the bath, the bundle is turned under a pair of rollers 36 to effect a sharp bend in the bundle which operates to open the bundle and to facilitate more complete penetration of the chemically-modified asphalt composition into the bundle.

The impregnated bundle is then raised from the bath 35 for passage through a roller or die 38, operating to remove excess impregnating composition from the bundle. Thereafter, the bundle is advanced over a roller 39 into a drying oven 40 to set the chemically-modified asphalt composition in situ in the glass fiber bundle.

The resulting bundle is shown in FIG. 4 of the drawing, and comprises a plurality of glass fibers 16 having the optional thin size coating 34 on the surfaces thereof and the impregnant 42 in the bundle. As can be seen from this figure, the impregnant 42 substantially completely fills the interstices between the glass fibers and serves to separate the individual glass fibers each from the other. The resulting bundle can then be used in reinforcement of asphalt or asphalt plus aggregate as described above whereby the bundles of glass fibers which have been impregnated with the chemically-modified asphalt composition are distributed through the asphalt or asphalt plus aggregate as reinforcement in the continuous phase defined by the latter.

When the chemically-modified asphalt is applied as an impregnant in accordance with this embodiment of the invention, the amount of the chemically-modified asphalt applied as an impregnant can vary within relatively wide limits. Generally, the chemically-modified asphalt impregnant constitutes from 10 to about 60% by weight based on the weight of the glass fiber bundles. As will be appreciated by those skilled in the art, it is also possible to treat the glass fibers twice, first by applying a thin film coating 16 containing the chemically-modified asphalt and then subject bundles of the thus coated fibers to impregnation whereby the chemically-modified asphalt serves as a size and as an impregnant.

When the concepts of this invention are applied to the use of glass flake, the asphalt, either in a molten or emulsified form, can be blended with the glass flake, and then the resulting composite applied to a, for example, road bed to form a wear layer. The platelets forming the glass flake tend to float in the fluid asphalt so as to form an overlapping, moisture-impervious layer just beneath the surface. It is that layer which thus forms a barrier against moisture.

The amount of the glass flake employed is not critical and can be varied within relatively wide limits. It is generally preferred that the amount of glass flake employed be such that it forms at least a single layer of glass flake particles overlapping the adjacent portion to form a moisture-impervious barrier. Best results are usually obtained when the glass flake ranges from 0.001 to 10% by weight based upon the weight of the glass flake with which the asphalt is combined.

Having described the basic concepts of the present invention, reference is now made to the following examples, which are provided by way of illustration and not by way of limitation, of the practice of this invention in the preparation of asphalt compositions chemically modified with organo silicon compounds and their use in the reinforcement of asphalt systems.

This example illustrates the preparation of a modified asphalt composition useful in the practice of this invention.

A solution of 200 parts by weight of a paving grade asphalt (50/60 penetration at 77.degree. F.) is dissolved in 50 parts by weight of toluene and placed in a stirred flask equipped with a heater. Thereafter, 1.2 parts by weight of acrylato chromic chloride, prepared from acrylic acid and chromyl chloride, are added to the solution.

The solution is then heated to reflux for 3 hours. At the end of that time, the heating is discontinued and the toluene solvent removed.

The chemically-modified asphalt is then applied as a thin film coating to glass fibers using the procedure illustrated in FIG. 1 of the drawing. The chemically-modified asphalt, dissolved in toluene, is applied to constitute a coating of about 0.85% by weight based on the weight of the glass fibers. It is then combined with asphalt and aggregate as reinforcement. The treated glass fibers are found to have good adhesion to the asphalt constituting the continuous phase in which the glass fibers are distributed as reinforcement.

Using the procedure described in Example 1, .beta.-alanine chromic chloride, prepared from .beta.-alanine and chromyl chloride, is reated with asphalt in the presence of a solvent. The chemically-modified asphalt is thereafter applied as athin film coating to individual glass fiber filaments using the procedure described in FIG. 1.

It is found that good adhesion between the treated glass fibers and asphalt is achieved.

Using the procedure described in Example 1, the paving grade asphalt described in Example 1 is reacted with 1% by weight of the chromium complex described in Example 2.

The resulting chemically-modified asphalt composition is then employed as a hot melt to impregnate bundles of glass fibers which have been sized with a glass fiber size composition of the type described in U.S. Pat. No. 3,837,989, the disclosure of which is incorporated herein by reference. The impregnant of the modified asphalt is applied in an amount to constitute about 17.5% by weight based on the weight of the glass fiber bundle.

The impregnated bundles are then combined with asphalt and aggregate whereby the impregnated bundles are distributed through the asphalt and aggregate as a continuous phase, the bundle serving as an impregnant therefor. Good adhesion between the impregnated bundles of glass fibers and the asphalt is achieved.

Using the procedure described in Example 1, blown asphalt is reacted with 0.9% by weight of methacrylato chromic chloride. The resulting chemically-modified asphalt composition can be applied to glass fibers as a thin film coating described in Example 1 or as an impregnant as described in Example 3. In either case, the resulting coated glass fibers are characterized by good adhesion to asphalt or asphalt plus a filler aggregate material.

The procedure employed in Example 4 illustrates another variation in the practice of this invention. The bitumen employed in that example is blown asphalt, asphalt which has been modified by reaction with air. As is now known to those skilled in the art, blown asphalt is partially oxidized to thereby increase the content of carboxyl groups in the bitumen itself. Conventional blown asphalt can be used in the practice of this invention, and is prepared by passing an oxygen-containing gas (preferably air) through the asphalt, while the asphalt is maintained at an elevated temperature within the range of 80.degree. to 300.degree. C., either with or without a solvent. It is generally preferred that the blown asphalt have an oxygen content ranging from 1-10% by weight based upon the weight of the asphalt.

It will be understood that various changes and modifications can be made in the details of procedure, formulation and use, without departing from the spirit of the invention, especially as defined in the following claims.