Plastic sheet materials and structures containing the same

Abstract

Plastic sheet material for use as a reinforcing layer in such bituminous sandwich structures as rollable sheet material especially for roof covering purposes and bituminous coatings on concrete bases especially trafficcarrying concrete surfaces. Surface covering material containing such a plastic material as a reinforcing layer. Surface coating for a concrete surface containing such a sheet material as a reinforcing layer.

Description

This invention relates to a plastic sheet material for use as a reinforcing layer in such bituminous sandwich structures as rollable sheet material especially for roof covering purposes and bituminous coatings on concrete bases especially traffic-carrying concrete surfaces.

Roofing felt for roof covering purposes normally comprises a basic felt, e.g., a rag or paper felt impregnated with asphalt or tar, and covered on both sides with layers of a bituminous composition, such as asphalt or tar. In order to provide a moisture proof roof covering having satisfactory strength properties, such roof coverings are often made up from several layers, for example five layers of roofing felt. To lengthen the life span of such roof coverings, their outer sides (the sides not in contact with the roofs) are covered with protective layers of a material which preferably is in the form of more or less flat particles or lamellae of crushed slate or other natural stone or of a ceramic or other suitable material.

It has been attempted to use instead of the rag or paper felt a backing consisting of a glass fiber mat. However, it has been found that such glass fiber based roofing sheets tend to be too rigid to allow a satisfactory application to roofs. Furthermore, cracks in the bituminous layers tend to be formed, particularly in cold weather.

It has also been attempted to use a polyethylene film as the backing in roofing felts. Such films have been found unsatisfactory primarily because they do not have the necessary thermal stability to resist the temperatures of the order of 180.degree.C which are used during the manufacture of roofing felts. Secondly, the coefficient of thermal expansion is too high to obtain a satisfactory roof covering.

Surprisingly, it has now been found that a sheet material having excellent flexibility and excellent strength properties is obtained by reinforcing the bituminous layer or layers with a backing which consists of a plastic film which is coated on both sides with superficially lying glass fibers and which has an elasticity modulus of not more than 5000 kgf/cm.sup.2 and a Vicat softening point not less than 60.degree.C.

Such a reinforced plastic film is rigid in itself and it might be expected that it would be totally unsuitable as a backing in a sheet material of the above mentioned type. However, it has been found that the flexibility of the final roofing is excellent and is higher than that of the backing itself. The plastic film is preferably made from a polyolefin and more preferably from polyethylene, polypropylene, copolymers of ethylene and vinyl acetate or copolymers of styrene and butadiene.

A roll roofing material comprising a glass fiber reinforced polyethylene film possesses strength properties clearly superior to those of a roll roofing material comprising a rag felt. Thus, the tensile strength and the tear strength is about three times as high as those of rag felt based products. Furthermore, the elongation at rupture is only about 3%.

The plastic film thickness normally is between 0.2 and 5 mm. It is particularly preferred to use films of a thickness of 0.8-0.9 mm for roofing materials.

The glass fiber mats are preferably water-laid non-woven fabrics of the thickness of about 0.25 mm. Water-laid fabrics are preferred because they have a more uniform thickness than air-laid fabrics.

The glass fiber mat is attached to the plastic film in such a way that it only partially penetrates into the plastic film. This results in a very strong adherence of the bituminous layers to be applied on each side of the glass fiber mat, which is in sharp contrast to the weak adherence of the bituminous layers to the plastic film. Thus, it will be understood that the glass fiber mat serves not only as a reinforcement for the plastic film, but also as an anchorage improving means.

The glass fiber mats are preferably impregnated with a binder so as to impart to the glass fiber mat the required strength. Examples of suitable binders are phenol formaldehyde and ureaformaldehyde resins.

Generally it is preferred to apply a layer of a bituminous composition to both sides of the reinforced plastic film, when used for roofing materials. However, since the layer at the underside of the sheet material (the side in contact with the roof) principally serves as a binder, it is not necessary to apply said layer to the sheet material until the time at which the sheet material is to be applied to the underlying structure.

The invention also relates to a method of manufacturing the sheet material disclosed above. This method comprises the steps of extruding a plastic film in an ordinary extruder and applying impregnated glass fiber mats to both surfaces of said film while the latter is still hot. The composite product is preferably compressed by passage through the nip of a set of rollers. Subsequently, one or two layers of a bituminous composition are applied to the outer surfaces of the reinforced film. The application of the bituminous material can be carried out in an ordinary roofing felt machine.

The invention further relates to a backing of the above mentioned type and particularly to a backing consisting of a polyethylene film coated on both sides with impregnated glass fiber mats.

Finally, the invention relates to a roof covering consisting of superimposed layers of the sheet material described above. As mentioned above such roof coverings normally consist of several layers of superimposed sheet materials. Due to the excellent strength properties of the sheet material of the invention it has now been possible to reduce the number of layers from for example five to two or three. In order to reduce the need for maintenance of such a roof covering, the outer bituminous layer preferably is covered with a protective layer of a material in the form of crushed slate or other natural stone material or of a ceramic or other suitable material.

The above described rollable sheet material is said to be especially useful for roof covering purposes and comprises, as the backing, a plastic film of special character which is coated on both sides with a glass fibre material. Compared to other types of glass fiber-based backings for roof covering materials, such a backing offers several advantages. Thus, the backing has high mechanical strength and is water-proof in itself. Furthermore, the backing is so stiff that the laying thereof in hot weather does not present any problems, and that the finished product, i.e., the covering rolls, can be stored in upright position without necessitating the use of a roll core. Further advantages are that the backing at low temperatures has excellent strength and sufficient stiffness to prevent crack formation in its asphalt surface when subjected to bending loads. Another advantage is that the backing can be hot-formed with a gas burner and will retain its new form after cooling, thereby facilitating the covering of e.g., edges and corners. As the backing is readily nailed and in the nailed-down state has a high elongation at break and shear strength, there is little risk that the backing will break within the nailed portions and slip out of position on steeply sloping roofs. The glass fibercoated plastic film backing besides has low heat transmission characteristics, which is an advantage because a surface covering manufactured from the backing and having its surface coated with an aggregate of crushed stone thereby can be glued to the base with extremely hot asphalt, and there is no risk that workmen walking on the newly laid surface covering will press the aggregate down into the asphalt coating on the upper side of the backing. Further advantages of the backing are that it cannot be punctured by sharp objects, such as stones and bottle caps, and that it is an excellent pressure distributor. This is extremely important, for instance when mineral wool panels are coated with the covering material since such panels may be destroyed by footsteps when conventional covering materials are used. However, because of the excellent pressure-distributing effect of the backing, the pressure will be distributed over a greater area of the mineral wool panels so that the specific surface pressure thereon will be considerably less, thereby greatly reducing the risk of a harmful compression of said panels.

It has, however, been discovered that the above mentioned backing which is intended for surface covering materials, especially roof coverings, can be used with great advantage also for other purposes where asphalt and bitumen are utilised to form a coating layer. In the production of a bituminous coating on a concrete base, especially bridge decks, traffic-carrying floor slabs, etc., a moisture insulating membrane is first applied to the concrete base, and upon this membrane a protective layer is placed which is then covered with a road surfacing material, usually asphalt concrete. The moisture insulating membrane usually is based upon asphalt or bitumen and serves to prevent moisture from exerting a decomposing effect on the concrete of the bridge deck, floor slab, etc. Normally, the protective layer is formed by a layer of reinforced concrete having a thickness of 5-8 cm and serving to distribute over the moisture insulating membrane the pressure exerted by the road covering and the traffic and to protect the moisture insulating membrane against mechanical damage during laying of the bituminous road covering material. The reinforced concrete layer besides serves to prevent the road covering material from coming into direct contact with the moisture insulating membrane. As already mentioned, the road covering materials are finally placed upon the protective layer of reinforced concrete.

The above mentioned backing for roof covering materials thus has proved extremely useful in the production of such bituminous coatings because it can replace the expensive concrete protective layer without detracting from the protective function of said layer. By dispensing with the reinforced concrete protective layer, a considerable advantage is gained, on one hand because it is highly expensive in itself and, on the other hand, because its weight and thickness adds to the construction costs for the bridge, the floor slab, etc., as a whole and also to the construction costs for the approaches to the bridge etc. Furthermore, laying the reinforced concrete layer is both complicated and time-consuming.

When the glass fibre-coated plastic film is used as protective layer, it must -- in the same way as when it constitutes the backing of a roof covering -- be in the form of a plastic film coated with superficially lying glass fibres and having an elasticity modulus of not more than 5,000 kgf/cm.sup.2 and a Vicat softening point of at least 60.degree.C. A special advantage in connection with bituminous coating is that the plastic film as well as the membrane constituting the actual moisture insulation can be produced in the factory and merely have to be rolled out and glued in conventional manner on the site.

It is not advisable to use films having an elasticity modulus higher than 5,000 kgf/cm.sup.2 since such films are not easy to roll, whereby the transport and laying thereof is rendered difficult. Films having a softening point below 60.degree.C are unable to withstand the action of the aggregate in a hot road covering material which when laid may have a temperature of about 130.degree.C, and in such films the aggregate included in the road covering will leave impression marks in or may even penetrate into the covering material so that the stones may damage also the underlying moisture insulation.

The plastic films utilised for bituminous coatings should preferably have a thickness of 0.2-5 mm. Thinner films are vulnerable and easily damaged during laying, and thicker films present rolling difficulties with ensuing transport and laying problems.

To prevent destruction of or damage to the film when the road is subjected to heavy shearing strengths, for instance when a heavy lorry jams on the brakes, the film in addition should have a shearing strength of at least 1.0 kgf/cm.sup.2.

It has been found best to use a thermoplastic film where the glass fibre material has been fused into both surfaces. The glass fibre material may be in the form of fleece, felt, mat or fabric. Because the protective layer has a surface of glass fibres, especially glass fibre fleece or felt, there will be obtained on one hand an excellent adhesion both to the underlying moisture insulation and to the overlying road covering and, on the other hand, an extremely high resistance to puncture by the stone aggregate of the road covering during laying and rolling with heavy road-making machines.

It has previously been tried to avoid the above mentioned reinforced concrete protective layer by using an asphalt mass or mastic as moisture insulation. However, such materials must be spread on the site and besides can be applied only in the form of thin layers since otherwise they may be dislodged from their relative positions in the construction. In actual practice, it has therefore been difficult to ensure watertightness of such an asphalt mass layer, and this applies also when the asphalt mass is laid in two layers with an intermediate reinforcement of glass fibre fabric. A further disadvantage of such asphalt mass layers is that the asphalt mass gradually tends to mix with the road covering material so that the layer structure of the coating is lost.

A great many plastic materials have also been proposed for the insulating layer of bridge decks and floor slabs. Thus, one prior art system that has found widespread use utilises epoxy tar. Other known solutions of the problem use polyurethane, polyurethane tar and polyesters. In the epoxy, urethane and polyester systems the plastics are applied in liquid form, either by coating or by spraying, and for this reason there is a considerably risk of obtaining thinner spots in the layers.

Normally, these three last mentioned types of insulating layer cannot either be laid at temperatures below the freezing point and, moreover, they require a dry base. The epoxy tar which is the one most widely used, besides suffers from the disadvantage that the insulation will be very stiff and may crack if cracks arise in the underlying concrete.

There has also been suggested a method of providing cavities in a roadway covering a concrete, bitumen or tar material, which method utilises an embossed plastic film and, if desired, a smooth plastic film in contact with said embossed plastic film. One of the great advantages of such roadway coverings is said to reside in that the plastic film or films included in the covering give a low friction and allow relative sliding motion of the different layers of the covering. In contradistinction hereto, the present invention aims at providing a satisfactory bond between the different layers of the covering, without jeopardising the resistance to crack formation in the plastic film material.

The above mentioned solutions of the problems occurring in connection with the laying of a road covering material on a concrete base have not found any widespread use, and one therefore has continued to use the traditional methods with reinforced concrete protective layers on the moisture insulating membranes.

To illustrate the invention, the following Examples are given, of which Examples 1-4 concern the use of glass fibre-coated plastic film in a covering material, while Examples 5-7 concern the use of the plastic film as a protective layer in the production of bituminous coatings on a concrete base.

EXAMPLE 1

A covering material for use as the top layer in a roof covering has prepared in the following manner.

A 0.8 mm polypropylene film was coated on both sides with a wet-processed glass fibre felt with a weight of 25 g/m.sup.2. Coating was carried out in such manner that the propylene plastic penetrated to only about half the thickness of the glass fibre felt. The polypropylene film employed had a density of 0.89 g/cm.sup.3, a Vicat softening point of 115.degree.C, and a melting index of 2.

The glass fibre-coated plastic film was then coated on both sides with a 1 mm layer of oxidised asphalt having a softening point of 85.degree.C (determined by the ball and ring method) and a Fraas breaking point of -25.degree.C, and contained 30% of fine-grained inorganic filler.

The asphalt coated covering material was coated on the underside with fine-grained talc and on the upper side with crushed slate.

The finished roof covering material had the following characteristics:

Tensile strength 50 kgf/5 cm width Elongation at break 4% Tear strength (Scan P 11:64*) >3200 gf *Scandinavian Pulp, Paper and Bord Testing Committee, "Tear Strength of paper and board, determined by means of APPITH-Elmendorf apparatus" published in English in "Papper och Tra", 46 (1964) :8, 479-481, 485-486, Helsinki, Finland.

EXAMPLE 2

A covering material for use as a membrane insulation (insulation against water pressure) was produced in the following manner.

A 1.0 mm plastic film of a copolymer of 85% ethylene and 15% vinyl acetate was coated on both sides with a wet-processed glass fibre felt of 50 g/m.sup.2. Coating was carried out in such manner that the copolymer penetrated to only about half the thickness of the fibre felt. The plastic film employed had a density of 0.93 g/cm.sup.3, a Vicat softening point of 65.degree.C (ball and ring method), and a melting index of 3.

The glass fibre-coated plastic film was then coated on both sides with a 1.5 mm thick layer of oxidised asphalt having a softening point of 110.degree.C (ball and ring method) and a Fraas breaking point of -30.degree.C, and containing 30% of fine-grained inorganic filler.

The asphalt-coated covering material was coated on the underside with a thin polyethylene film and on the upper side with fine-grained sand.

The finished covering material had the following characteristics:

Tensile strength 85 kgf/5 cm width Elongation at break 4% Tear strength (Scan P 11:64) >3200 gf

EXAMPLE 3

A roof covering material for use as the surface layer in a roof covering was produced in the following manner.

A 0.8 mm polyethylene film was coated on both sides with a wet-processed glass fibre felt of 50 g/m.sup.2. Coating was carried out in such manner that the plastic penetrated to only about half the thickness of the glass fibre felt. The plastic film employed had a density of 0.92 g/cm.sup.3, a Vicat softening point of 76.degree.C, and a melting index of 20.

The glass fibre-coated plastic film was then coated on both sides with a 1 mm layer of oxidised asphalt having a softening point of 95.degree.C (ball and ring method) and a Fraas breaking point of -25.degree.C, and contained 30% of fine-grained inorganic filler.

The asphalt-coated covering material was coated on the underside with fine-grained talc and on the upper side with crushed slate.

The finished product had the following characteristics:

Tensile strength 80 kgf/5 cm width Elongation at break 4% Tear strength (Scan P 11:64) >3200 gf

EXAMPLE 4

A covering material for use as a membrane insulation (insulation against water) was produced in the following manner.

A 1.0 mm polyethylene film was coated on both sides with a wet-processed glass fibre felt of 25 g/m.sup.2. Coating was carried out in such manner that the plastic penetrated to only about half the thickness of the glass fibre felt. The plastic film employed had a density of 0.92 kgf/cm.sup.3, a Vicat softening point of 86.degree.C, and a melting index of 2.

The glass fibre-coated plastic film was then coated on both sides with a 1.5 mm thick layer of oxidised asphalt having a softening point of 100.degree.C (ball and ring method) and a Fraas breaking point of -30.degree.C, and contained 30% of fine-grained inorganic filler.

The asphalt-coated covering material was coated on the underside with a thin polyethylene film and on the upper side with fine-grained sand.

The finished product had the following characteristics:

Tensile strength 55 kgf/5 cm width Elongation at break 4% Tear strength (Scan P 11:64) >3200 gf

EXAMPLE 5

Cleaned concrete having a smooth and solid surface was coated with an asphalt solution containing an adhesion-improving agent. Hot gluing asphalt having a softening point of 85.degree.C (ball and ring method) was then used for gluing the following layers:

One layer of 5 mm asphalt panels reinforced with 500 g/m.sup.2 glass fibre fabric.

The layer was fully glued.

One layer of asphalt mineral felt weighing about 2 kgf/m.sup.2.

The layer was fully glued.

One layer of 1.5 mm plastic film consisting of a copolymer of 85% ethylene and 15% vinyl acetate and coated on both sides with a glass fibre fleece. The plastic film had a density of 0.93 g/cm.sup.3, a melting index of 3, an elasticity modulus of 490 kgf/cm.sup.2, and a

Vicat softening point of 65.degree.C.

The layer was fully glued.

Directly upon these layers there was laid and rolled a road covering consisting of 1.5 cm asphalt concrete with fine aggregate and 4 cm asphalt concrete of coarser aggregate, and the two asphalt concrete layers having a temperature of about 120.degree.C and about 140.degree.C, respectively, when laid.

EXAMPLE 6

Cleaned concrete having a smooth and solid surface was coated with an asphalt solution containing an adhesion-improving agent. Hot gluing asphalt having a softening point of 85.degree.C (ball and ring method) was then used for gluing the following layers:

One layer of asphalt mineral wool felt with 5 mm styrene expanded plastic balls on the underside. Weight about 2 kgf/m.sup.2. The layer was point-glued on about 25% of the surface.

One layer of 5 mm asphalt panels reinforced with 500 g/m.sup.2 glass fibre fabric.

The layer was fully glued.

One layer of 1.5 mm plastic film consisting of a block copolymer of styrene and butadiene and having a density of 1.02 g/cm.sup.3, a melting index of 3, an elasticity modulus of 75 kgf/cm.sup.2 and a Vicat softening point of 78.degree.C. Both sides of the plastic film were coated with fused-in glass fibre cloths. The layer was fully glued.

On these layers, there was laid and rolled a covering consisting of 6 cm asphalt concrete having a temperature of about 140.degree.C when laid.

EXAMPLE 7

Cleaned concrete on a motorway bridge was coated with an asphalt primer solution containing an adhesion-improving agent. Hot gluing asphalt having a softening point of 85.degree.C (ball and ring method) was then used for gluing two layers of asphalt panels with a reinforcement of 180 g/m.sup.2 glass fibre fabric coated on both sides with asphalt having a softening point of 110.degree.C (ball and ring method) and a Fraas breaking point of -24.degree.C. The panels of the two layers were offset relative to one another. The same hot gluing asphalt was then used for gluing on the asphalt panels a layer of 1.5 mm glass fibre-coated plastic film of polyethylene having a melting index of 20, a density of 0.916 g/cm.sup.3, and a Vicat softening point of 76.degree.C, and coated on both sides with a glass fibre fleece of 50 g/m.sup.2, the plastic having penetrated to about half the thickness of the glass fibre fleece. The plastic film was then coated with an asphalt primer solution containing an adhesion-improving agent, whereupon there was applied a 1.5 mm asphalt concrete layer which during laying had a temperature of about 130.degree.C and consisted of an aggregate having a particle size of 0-4 mm and of bitumen in an amount of 6%, based upon the asphalt concrete. After roller compression, a 5 cm asphalt concrete layer of the same type as was used on the connecting motorway was applied.

Examples 5-7 gave a road covering in which the protective layer of glass fibre-coated plastic film was satisfactorily anchored both to the base and to the road covering material proper and besides proved capable of withstanding the considerable stresses exerted by heavy road-making machines, without being punctured by the aggregate in the road covering material.

Three embodiments of the invention will be more fully described hereinbelow with reference to the accompanying drawing in which:

FIG. 1 is a perspective view and section of a cut open piece of a plastic sheet according to the invention;

FIG. 2 is a perspective view and section of a cut open piece of a roofing felt according to the invention;

FIG. 3 shows a section of part of a bituminous sandwich structure according to the invention placed on a concrete base.

FIG. 1 illustrates a plastic sheet according to the invention, which consists of a plastic film 20 which is coated on both sides with a non-woven glass fibre fabric 21, said fabric being partially fused into the plastic film.

FIG. 2 illustrates a roofing felt having a backing which consists of a plastic film 20 coated on both sides with a non-woven glass fibre fabric 21, said fabric being partially fused into the surface of the plastic film. An asphalt layer 22 is applied to each glass fibre fabric 21 and the surface of one asphalt layer 22 is provided with a layer 23 of crushed slate partially rolled into said asphalt layer 22. The roofing felt shown in FIG. 2 corresponds to that described in the above Example 3.

FIG. 3 illustrates part of a bituminous sandwich structure which serves as the surface layer of a pavement structure. Anchored to a concrete base 30 which may be a bridge deck or other traffic-carrying concrete surface, is an asphalt mineral wool felt 31 with expanded plastic balls 32 at the underside. Glass fibre reinforced asphalt panels 33 are anchored to this felt 31 and on top of them there is anchored a plastic film layer 34 which corresponds to the plastic film layer 10, 11 in FIG. 1. Finally, a thick asphalt concrete layer 35 is applied on top of the layer 34. The bituminous sandwich structure shown in FIG. 3 corresponds to that described in the above Example 6.

Claims

What we claim and desire to secure by Letters Patent is:

1. Surface coating in combination with a concrete surface wherein the surface coating comprises a reinforcing layer consisting of a plastic film having a modulus of elasticity of not more than 5000 kgf/cm.sup.2 and a Vicat softening point of at least 60.degree. C and a glass fiber layer attached to each side of the plastic film and only partially penetrating thereinto, the thickness of the plastic film being between 0.2 and 5 mm; a bituminous binder attaching said reinforcing layer to the concrete surface and partially penetrating into the glass fiber layer on one side of said reinforcing layer; and a bituminous layer attached to the other side of said reinforcing layer and partially penetrating into the glass fiber layer on that side of said reinforcing layer.

2. The surface coating of claim 1, attached to a traffic-carrying concrete surface.

3. The surface coating of claim 1, wherein the plastic film of said reinforcing layer consists of a thermoplastic resin.

4. The surface coating of claim 1, wherein the plastic film of said reinforcing layer has a thickness of from 0.2 to 5 millimeters.

5. The surface coating of claim 1, wherein the glass fiber layer of said reinforcing layer is a non-woven glass fiber fabric.

6. The surface coating of claim 3, wherein the glass fiber layer of said reinforcing layer is a glass fiber felt.

7. The surface coating of claim 3, wherein said thermoplastic resin is a member of the group consisting of polyethylene, polypropylene, copolymers of ethylene and vinyl acetate and copolymers of styrene and butadiene.

8. The surface coating according to claim 7 wherein the reinforcing layer is a layer of 1.5 mm of polyethylene of melting index 20, density 0.916 g/cm.sup.3, Vicat softening point 76.degree.C, coated with glass fibers of 50 g/cm.sup.2, the polyethylene having penetrated to about one-half the thickness of the glass fibers.