US3457136A - Process for producing fiber reinforced bitumen-containing products and the reinforced products obtained thereby - Google Patents

Description

ilite ties 3,457,136 PROCESS FOR PRODUCING FIBER REINFORCED BlTUMEN-CONTAINING PRODUCTS AND THE REINFORCED PRODUCTS OBTAINED THEREBY Gottlieb Lebrecht Zaadnoordijk, Soesterberg, Netherlands, assignor to American Enka Corporation, Erika, N.C., a corporation of Delaware No Drawing. Filed Mar. 15, 1967, Ser. No. 623,245 Claims priority, application Netherlands, Mar. 19, 1966, 6603637 Int. Cl. B321) 11/02 U.S. Cl. 16189 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for producing bitumen-containing products, e.g., laminates, road foundations, road pavements, roofing, pipe coatings, and the like structures reinforced with fibrous materials and particularly to a process for reinforcing materials having a bitumen base with synthetic fibrillary products pretreated to have improved adhesion for the bitumen and the products obtained thereby.

Processes are known for producing fiber-reinforced bitumen base materials. One very important problem in such processes is that sutficient adhesion must be obtained between the reinforcing fibers and the surrounding bitumen.

In this regard it has been already proposed to make use of auxiliary materials to promote adhesion between the fibers and the bitumen; for instance, 'in the case of cocoanut fibers, light hydrocarbon fractions, solar oil or fuel oil have been proposed.

Advantageously, it has been found in accordance with this invention that the adhesion between fibrillary reinforcing materials particularly those containing linear synthetic poly-condensation products can be considerably improved by applying a special auxiliary material which is fundamentally different from the materials heretofore used as auxiliary adhesion promoters.

Thus, this invention contemplates a process for producing fiber reinforced bitumen-containing products in which the surface of the fibrous reinforcing material is pretreated with a resin compatible with bitumen that greatly enhances the adhesion between bitumen and fibrous material before the reinforcing material is bonded to a bitumen-containing material.

Furthermore, this invention is concerned with a process for reinforcing bitumen base materials by treating a fibrillary material containing synthetic linear polycondensation products with a wax-base resin derived from coal such as montan resin, contacting the treated fibrillary material with a heated, fiowable bitumen base material and thereafter uniting the bitumen and said treated fibrillary material by the application of pressure. The resin chosen must be compatible with the bitumen and should Patented July 22, 1969 promote its flow into intimate contact with the treated fibrillary material to substantially improve, i.e., increase, the adhesion between the fibrillary material and the bitumen base.

It will be understood that the term bitumen as used herein includes products which in the English technical literature are officially referred to as asphaltic bitumen or the bitumen as defined on page 549 of The Petroleum Handbook published in 1948 by The Shell Petroleum Company, Limited. Thus, bitumen includes asphalt-like hydrocarbons such as asphalt, asphaltites, asphaltic pyrobitumens, mineral tars, mineral waxes, e.g., ozokerite and the like, which may be hard and brittle, or semisolid substances. Also the terms asphalt or asphaltic as used herein are to include the meaning set forth on the abovenoted page 549 of The Petroleum Handbook.

It will be appreciated that the products obtained by this invention include those structures having one or more layers, coating, covering, sheets and the like bitumen-containing materials which are bonded to a substrate of a bitumen base material in which a fibrillary product or material forms a reinforcement for the layer or for the bitumen base material or for both. It will be understood that the bitumen base material is meant to encompass those materials having bitumen as a base for other substances including aggregates, fillers, and the like.

It will also be understood that the bitumen layer used to produce the reinforced products of this invention may further be mixed with organic materials such as wood flour, cork flour and the like and may also include inorganic fillers having a particle size smaller than about 200 mesh.

The linear polycondensation products suitable for purposes of this invention include fiber-forming materials such as the polyamides prepared from lactams, e.g., caprolactam, and the polyamides prepared from diamines and dicarboxylic acids, e.g., hexamethylene diamine and adipic acid, the polyesters prepared from terephthalic acid or the ester-forming derivatives thereof, and glycols, e.g., polyethylene terephthalate, and the like.

It will be appreciated that other synthetic fiber-forming materials such as polyacrylonitrile, copolymers of acrylonitrile, and the like may also be used to form the reinforcing fibrillary materials.

The fibrillary products found useful as reinforcing materials include continuous twisted or nontwisted multifilament yarns, monofilaments, spun yarns, threads, staple fibers and the like.

In the process according to the invention the fibrillary materials may be used in a loose form, e.g., in the form of individual fibers. When such fibers are used, the fibers may be mixed with the bitumen or the asphalt before the mass is formed into a coating or covering layer, e.g., on roads, dykes, tile plates, or the like. Threads and fibers may also be used in the form of woven or knitted fabrics or bonded or nonbonded fibrous sheets. Preferably fabrics woven from continuous filament yarns are used.

It will be appreciated that the fibrillary material used may entirely consist of synthetic liner polycondensation products or be mixed with fibrillary materials of a different material, e.g., glass, cotton, regenerated cellulose or the like.

When woven or knitted textile products are used as reinforcing material, the nature of the product to be reinforced determines the denier of the yarn applied and the density of the yarns in the textile product.

For the purpose of reinforcing an asphalt mass with woven fabrics it is preferred to use multifilamerit yarns of synthetic linear polycondensation products having a relatively high denier, e.g., 1000 or higher, and a filament denier of 3 or higher. If desired, yarns to be used may be composed of individual yarns of a lower denier that are twisted together.

In order to promote adhesion between the: fabrics 1t 1s advantageous to use wide-meshed textile products.

Examples of these products are woven fabrics which contain four weft threads and four warp threads per centimeter of fabric.

Woven fabrics have an advantage over knitted fabrics since they can more readily be kept under a tension while being incorporated in the asphalt mass. Owing to this tension the occurrence of cracks in covering, coatings, layers or the like can be prevented with more certainty. The best results are obtained with a woven fabric having a low stretch value.

For the purpose of reinforcing bitumen layers used on a large scale, for example in roofing it is preferred to employ the more densely woven fabrics.

In accordance with this invention it has been found that a wax-base resin derived from coal such as montan resin is a particularly suitable auxiliary material for increasing the adhesion between the fibrous reinforcing material and the bitumen. This resin is contained in montan wax in amounts ranging between 25 percent and 50 percent by Weight and may be separated therefrom by extraction. Montan wax is derived from lignite, a low rank coal, by countercurrent extraction.

Montan resin is generally characterized by a solidifying point between 60 and 80 C. and more often by a solidifying point of about 75 to 76 C. The acid value of the resin is generally between 30 and 40, and its saponification number in the range of 55 to 65.

In the processing of hot asphalt which usually takes place at temperatures higher than 100 C., the montan resin appears to promote the flow of the asphalt on the surface of the reinforcing material. When the temperature of the asphalt drops to below 75 C. there is substantially no flow at all. Apparently, flow of asphalt promotes the impregnation of the reinforcing material so that a better adhesion is obtained. Surprisingly and unaccountably it has been found that the adhesion of the asphalt to a synthetic linear polycondensation product is particularly improved by the use of montan resin.

It will be understood that in addition to montan resin alone, montan resin mixtures which still show the adhesion promoting action of the montan resin may also be used. Such mixtures preferably contain the montan resin in an amount of 40 percent by weight or more with other suitable resins which are compatible with bitumen.

In order to obtain optimum adhesion it is desirable that the fibrous reinforcing material should be provided with an amount of montan resin which is at least 35 percent calculated on the weight of the fibrous material.

This may best be carried out by impregnating or spray ing the fibers with a solution or dispersion of the montan resin.

One suitable solvent for montan resin is ethyl acetate, in which the resin is soluble at an elevated temperature. After the resin is dissolved in the acetate, the resulting solution is cooled down and may be used at temperatures of from 20 to 40 C. By an appropriate choice of a temperature within this temperature range the desired viscosity of the solution may be obtained.

In order that the resin solution may be sufliciently fluid, it is preferred to use montan resin-acetate solutions which contain two parts by weight ethyl acetate to one part by weight montan resin.

It will be appreciated that the viscosity of the solution also determines the degree to which the fibrous material is provided or charged with montan resin.

The reinforcing fibers may be charged in various processing stages, i.e., before or after they are formed into woven fabrics, which it will be understood is the form in which it is preferred to carry out the reinforcing process of this invention.

After the fibers have been charged with the resin by passing them through the resin-acetate solution, the ethyl acetate must be removed; this is preferably done in a two-stage process. In the first stage, the treated fibers are dried below 50 C. In the second stage after the removal of the excess ethyl acetate, the fibers are dried at a temperature above 50 C., and then they are cooled to ambient temperatures.

The ethyl acetate may completely be removed, but it is preferable that the drying process be carried out so that a few percent of ethyl acetate, e.g., 3 to 10 percent by weight, is left in the resin. This prevents brittleness and stops the resin from cracking off the fibrous material.

Instead of impregnation by saturating the fibers in a solution, it is possible to insure that the surface of the fibrous material carries a sufficient amount of montan resin at the moment of bonding, by spraying the resin onto the material. In the case of spraying, it is possible to use pure montan resin alone or a mineral carrier into which the resin is introduced by impregnation. When spraying is the method used to apply the resin, it must be insured that the resin is uniformly distributed over the fiber or fabric.

It will be understood that this invention is also concerned with the fiber reinforced, bitumen-containing product obtained by the above-described process. This product is characterized generally as a bitumen-containing material adhesively bonded to a fibrillary reinforcing material pretreated with a resin such as montain resin that is compatible with bitumen and that substantially increases the adhesion between bitumen and the fibrillary material.

Although previously a method has been described for the manufacture of a covering material in which felt, jute and fabrics are coated with a mixture of asphaltic bitumen and the residue resulting from the preparation of montan wax, the residue from the preparation of the montan wax is used in this situation to increase the melting point of the coating mass. This previously described method does not, however, mention that there would be any improvement in the adhesion between the coating mass and the substratum. Furthermore, this method does not recognize using montan resin only to coat the textile material before applying a coating mass having a bitumen base so that the material is free of the montan wax or the residue of its preparation.

The invention will be further described in the following examples which are merely illustrative and are not intended to be restrictive of the scope of the invention.

EXAMPLE I A mineral mixture containing 45.5% by Weight of sand having a fineness modulus of 2.10, 4.5% by weight of a low-grade filler with a fineness of 200 mesh and 50% by weight of gravel with a particle size not greater than 16 mm. (the amounts of each being calculated on the entire mineral mixture), is mixed with a bitumen having a penetration value of 80.5 and a softening point of 46.9 C. in an amount of 4.5% (based on the weight of the mineral mixture). This bitumen base material was used to produce a 30x30 cm. tile weighing 3200 grams in a tile press.

The tile was pressed at a temperature of 135 i5 C. After pressing the tile was cooled down to about 10 C. Then 2.7 grams of a Belgian asphalt emulsion which contained 49% by weight of bitumen was applied to one side of the tile. After the breaking up of the emulsion, which had been allowed to stand for some time, a piece of woven fabric made of polyethylene terephthalate was clamped on the tile. This fabric showed 4 weft picks and 4 warp ends per cm. in a plain weave.

The weft and the warp yarns of the fabric each consisted of two 1000 denier draw-twisted yarns with 210 filaments, and the yarns were twisted together to Z turns. The yarns had a residual shrinkage of 8 to 9%.

Before being placed on the tile, the fabric had been charged with montan resin having a solidifying point of 75 -76 C., an acid number between 30 and 40, and a saponification number between 55 and 65, in an amount of 42% calculated on the weight of the fabric. This amount was applied by passing the fabric through a solution of one part montan resin in two parts ethyl acetate at a temperature of about 35 C. The impregnated fabric was dried in two stages: in the first stage with air at 20 C. and in the second stage it was after-dried at 60 C. The dried fabric was then cooled down to room temperature.

The fabric placed on one side of the tile was then coated with about 18 grams of an asphalt emulsion of the same composition previously used.

Then the fabric was allowed to set until the asphalt emulsion had broken up. Subsequently a coating of the same composition as the asphalt mass used to prepare the tile was pressed on to the fabric-covered side of the tile at a temperature of 135 i5 C. In this way, two equally thick asphalt layers were produced on both sides of the fabric on the cooled tile.

To evaluate the adhesion of the woven fabric to the asphalt, a series of test tiles having a surface area of 7.07 7.07 cm. were made in the manner outlined above by applying 200 grams of asphalt to each side of a fabric. The fabric was allowed to project 5 cm. from one side of the tile, and 20 cm. from the opposite side.

The strip of fabric used was 5 cm. wide and both its longitudinal edges were equally far from the edges of the tile. When the last pressed tile potrion had cooled down, the 5 cm. piece of fabric was cut off along the finished tile. Then the tile was placed on its side with the fabric piece projecting upwards and the tile was so heavily loaded that the pulling force to be used in the test could not raise the tile.

An equally high pulling force was subsequently exerted on the projecting strip of fabric along the entire length thereof, namely: a pulling force of 3.6 kg. for 1 minute, and subsequently, pulling forces of, successively, 7.6 kg., 9.5 kg., 12.1 kg., 15.2 kg., 22.8 kg, 24.7 kg., 26.6 kg., 28.5 kg., 30.4 kg., and 32.3 kg., were each applied for 5 minutes. This series of forces was applied until the fabric came off. The time in seconds and the sum of the pulling forces were combined in accordance with the formula: He.=the sum of the products of loading time in seconds and the load in kilograms in each part of the test.

The following values of He. were found when use was made of the fabrics provided, respectively, with the following amounts by weight of montan resin:

EXAMPLE II In the same manner as described in Example I additional test tiles were made using a reinforcing fabric consisting of polyamide fibers prepared from polycaprolactam. This fabric showed 4 weft picks and 4 warp ends per centimeter in a plain weave. The weft and the Warp yarns each consisted of two 840-denier yarns with 42 filaments and the yarns were twisted together to 70 Z turns. The stretch of these yarns was 19 to 20%.

In this case, the amount of montan resin was varied up to 49% by weight of the fabric. For these tiles the following He. values were determined in the manner indicated in Example I:

Percent of montan resin: He.

From the results obtained in Examples I and II, it will be seen that the use of montan resin as an adhesion promotor greatly increases the adhesion between the reinforcing fabric and the bitumen. In Example I the He. values obtained upon removal of the fabric increased to more than times that obtained by the control, i.e., the fabric Without any resin, and in Example II the He. values increased to more than 35 times the control value.

EXAMPLE III For the manufacture of a reinforced road surface having an asphalt base, a foundation layer was formed on a sub-layer of mechanically compacted sand. The foundation was rolled to a thickness of 7 cm. In this case, the foundation was made of a mixture of gravel, sand, a lowgrade filler and asphalt bitumen 80/100.

The mineral mixture in the asphalt was composed as follows:

50% by weight passed through a screen having apertures of 32 mm., but was retained by a screen having apertures of 2.4 mm.

40% by weight passed through the screen with 2.4 mm. apertures, but was retained by a screen having apertures of 0.075 mm.

5% by weight passed through the screen with 0.075 mm.

apertures.

The amount of asphalt bitumen was 5.5% by weight of the total mineral mixture.

On the foundation layer, an adhesive layer of an anionic 50%-asphalt emulsion was provided over which there was unrolled a fabric of the composition and structure mentioned in Example I, charged with 42% by weight of the montan resin also described in Example I. This fabric was stretched in the longitudinal and in the transverse directions and was pinned down. Another coating of an asphalt emulsion of the above-described composition was sprayed onto the fabric; the upper side being provided with twice as much asphalt emulsion as the underside.

After the asphalt emulsion had broken up, two asphalt layers, each 7 cm. thick, were successively provided on the foundation layers and rolled. For these two layers the same asphalt mineral mass was used as described above. The asphalt masses were worked up at a temperature of 145i5 C.

To these layers there was subsequently applied the anionic 50%-asphalt emulsion. After said emulsion had broken up, a binder layer 4 cm. thick was rolled on to these layers. This binder consisted of broken stone, sand, a medium-grade filler and asphalt bitumen 80/ 100.

Of the mineral mixture:

70% passed through a screen having apertures of 16 mm. but was retained by a screen having apertures of 2.4 mm.

25% passed through the screen having 2.4 apertures but was retained by a screen having apertures of 0.075 mm.

5% passed through the screen having 0.075 mm. apertures.

The amount of asphalt bitumen 80/ was 5.5% by weight of the mineral mixture.

The binder layer was given an adhesive layer prepared from an asphalt emulsion, to which adhesive layer a second fabric identical with that described above was attached and covered with a 50%-asphalt emulsion.

After the emulsion had broken up a 4 cm. thick top layer was applied consisting of broken stone 5/ 15 and broken stone 2/ 5, sand, a medium-grade filler, and asphalt bitumen 80/100.

The mineral mixture was composed as follows:

35% by weight passed through a screen having apertures of 16 mm, but was retained by a screen having apertures of 5.6 mm.

22% by weight passed through the screen having the 5.6

mm. apertures, but was retained by a screen having apertures of 2.4 mm.

35% by Weight passed through the screen having 2.4 mm. apertures, but was retained by a screen having apertures of 0.075 mm.

8% by weight passed through the screen having 0.075

mm. apertures.

The asphalt bitumen 80/ 100 was used in an amount of 7.2% by weight, calculated on the mineral mixture.

The asphalt was worked up at a temperature of 15 C. The resulting reinforced road surface shows much improved dimensional stability, thus evidencing the outstanding adhesion obtained between the fabric and the asphalt.

In the construction of this road surface use was made of two layers of fabric. However, it will be: appreciated that it is also possible to use a larger or smaller number of fabric layers and that they may be incorporated in the road surface in different places or the road surface may be built up on a fabric layer.

I claim:

1. A process for producing fiber reinforced bitumencontaining products which comprises reinforcing a bitu men-containing material with fibrillary reinforcing material and substantially enhancing the adhesion between the bitumen-containing material and the fibrillary reinforcing material by pretreating the fibrillary material with montan resin extracted from montan wax, said resin having a solidifying point between 60 C. and 80 C., an acid value between 30 and 40 and a saponification number in the range of 55 to 65, said montan resin being compatible with the bitumen and being capable of promoting intimate contact between the bitumen, in a flowable condition, and the treated fibrillary material.

2. The process of claim 1 in which the fibrillary reinforcing material is prepared from polyethylene terephthalate having a filament denier of 3.

3. The process of claim 1 in which the fibrillary reinforcing material is a woven fabric.

4. The process of claim 1 in which the fibrillary reinforcing material is coated with montan resin in an amount of at least percent by weight, based on the weight of the reinforcing material.

5. The process of claim 1 in which the fibrillary reinforcing material is treated With a solution of montan resin in ethyl acetate and subsequently dried by heating.

5. The process of claim 5 in which the solution of montan resin in ethyl acetate is at a temperature of 35 C.

7. The process of claim 1 in which said montan resin is in a solution containing one part by weight of montan resin and two parts by weight of ethyl acetate.

8. A fiber reinforced bitumen-containing product comprising a bitumen-containing material adhesively bonded to a fibrillary reinforcing material pretreated with montan resin, extracted from montan wax, said resin having a solidifying point between 60 C. and 80 C., an acid value between 30 and and a saponification number in the range of to 65, said resin being compatible with bitumen and being capable of greatly increasing the adhesion between bitumen and said reinforcing material.

References Cited UNITED STATES PATENTS 2,268,759 1/ 1942 Martin. 2,3 43,600 3/1944 Weimann. 2,552,947 5/1951 Fasold et al 106282 XR 2,634,208 4/ 1953 Miscall et a1 106-282 XR 2,688,005 8/1954 Clayton et al. 2,701,217 2/1955 Fair.

JULIUS FROME, Primary Examiner J. B. EVANS, Assistant Examiner US. Cl. X.R.