CONSTRUCTION MATERIAL

Abstract

A construction material comprises a watertight sheet material of a mixture of a plastic and at least one additive. The plastic comprises at least substantially polyvinyl butyral (PVB). At least a fire retardant containing ammonium polyphosphate is added thereto as additive. Use is particularly made of recycled polyvinyl butyral.

Claims

1. A roof covering, comprising a watertight sheet material from at least a plastic and at least one additive, characterized in that the plastic comprises at least substantially polyvinyl butyral (PVB), wherein the at least one additive comprises at least a fire retardant containing ammonium polyphosphate (NH.sub.4PO.sub.3).sub.n and aluminum trihydrate (Al(OH).sub.3.

2. The roof covering of claim 1, characterized in that polyvinyl butyral (PVB) and ammonium polyphosphate are used in the mixture in a weight ratio of about 100:4-50.

3. (canceled)

4. The roof covering of claim 1, characterized in that polyvinyl butyral (PVB) and the aluminum trihydrate (ATH) are used in the mixture in a weight ratio of about 100:40-50.

5. The roof covering of claim 1, characterized in that the at least one additive in the mixture also comprises a coloring agent.

6. The roof covering of claim 5, characterized in that a white pigment, comprising titanium oxide and/or titanium dioxide, is used as the coloring agent.

7. The roof covering of claim 1, characterized in that the at least one additive in the mixture comprises one or more selected from the group consisting of a UV stabilizer and an antioxidant.

8. The roof covering of claim 1, characterized in that the at least one additive in the mixture comprises at least a plasticizer.

9. The roof covering of claim 8, characterized in that the polyvinyl butyral comprises plasticized polyvinyl butyral which was provided with at least a plasticizer before mixing in an additive.

10. The roof covering of claim 1, characterized in that the sheet material has a thickness of half a millimeter to several millimeters, by a width of half a meter to several meters, and is wound into a roll with a length of several meters or several tens of meters to over a hundred meters.

11. The roof covering of claim 1, wherein the polyvinyl butyral is recycled polyvinyl butyral.

12. The roof covering of claim 1, wherein the aluminum trihydrate is in the form of particles with an average particle size smaller than 100 microns.

13. The roof covering of claim 10, wherein the sheet material has a thickness of between 0.6 and 5 millimeters.

14. The roof covering of claim 8, wherein the plasticizer comprises an ethylene/vinyl acetate/carbon monoxide copolymer.

15. The roof covering of claim 1, wherein the polyvinyl butyral, aluminum trihydrate and ammonium polyphosphate are applied in a ratio of about 2:1:1.

16. The roof covering of claim 1, wherein the polyvinyl butyral, aluminum trihydrate and ammonium polyphosphate are applied in a ratio of 100 PVB:40 ATH:4 APP.

Description

EXEMPLARY EMBODIMENT

[0017] As starting material, use is made of polyvinyl butyral (PVB) which is supplied in granular form and with which a hopper is filled. Polyvinyl butyral is applied as a thin sheet material in layered glass, mainly in vehicles, and can be reclaimed therefrom and be reused in the construction material according to the invention. Reclaimed PVB is therefore advantageously used for the production of the construction material.

[0018] A second hopper is filled with powder containing ammonium polyphosphate, which is added as fire retardant, while a third hopper is filled with aluminium trihydrate (ATH) which can be employed as filler and also additional fire retardant. In both cases use is made of a fine powder with an average grain size in the order of 60 micron.

[0019] Each hopper is provided at the bottom with a dosing unit, a rotational speed of which can be controlled individually. A dosage of the different constituents can thereby be controlled individually. Use is preferably made here of a gravimetric dosing whereby the concentrations of the different constituents can be dosed with great accuracy. Said fractions are thus supplied, after optionally being mixed together beforehand, to a screw elevator of an extrusion device in a ratio of about 2:1:1 and therein gradually melted into a homogeneous mass under the influence of additionally supplied heat.

[0020] A colouring agent in the form of several percent by weight of titanium oxide and/or titanium dioxide is also added to the mixture from containers provided for this purpose. In order to avoid the formation of lumps therein and to enhance a uniform mixing use is here advantageously made of plastic granules which were enriched beforehand with titanium (di)oxide. Use is for this purpose particularly made of polyvinyl butyral (PVB) granules. Because this is however only a relatively small proportion of the whole, use can however also be made of a different plastic such as polyethylene (PE).

[0021] A small percentage of UV stabilizer and antioxidant is dosed into the mixture in similar manner. The UV stabilizer serves to give the final sheet material material an increased resistance to UV radiation from sunlight, while the antioxidant already protects the material during the manufacturing process from degradation resulting from the increased process temperature. The composition of the thus obtained mixture is shown in table 1.

TABLE-US-00001 TABLE 1 Content Constituent: % by weight Polyvinyl butyral (PVB) 48.00% Aluminium trihydrate (ATH) 24.81% Ammonium polyphosphate (FR) 24.81% Titanium(di)oxide (pigment) 2.00% UV blocker(s) 0.35% Antioxidant(s) 0.03% 100.00%

[0022] The viscous melted mass is carried under pressure to an extrusion unit and therein pressed through a gap of several millimetres, having a width in the order of a metre to several metres. In this embodiment use is made in this respect of an extrusion mould with a gap width of 1500 millimetres and a selected gap height of 1, 1½, 2, 3 or 4 millimetres. This produces a continuous sheet material of roughly the same dimensions. This sheet material, still warm, is cooled over an assembly of several successive rollers and then carried over a long table of several tens of metres in order to allow the sheet material to cool and relax.

[0023] Finally, the cooled sheet material is carried via a conveyor belt of several tens of metres to a winding unit and then finally formed into a roll at a desired length. When the desired length is reached, the sheet material is cut, after which a subsequent roll is formed in similar manner.

[0024] The thus obtained material is subjected to a set of tests as according to a standard EN-13956, wherein the material was compared to samples of common, commercially available roof covering materials. In respect of the material according to the invention use is made in this test of sheet materials having thicknesses of respectively 1 and 1½ millimetres. As reference material, use was made of a PVC sheet material with a thickness of 1½ millimetres, an EPDM foil with a thickness of about 2 millimetres, and bituminous roofing felt with a thickness of about 2 millimetres, referred to below as FPO.

[0025] Watertightness:

[0026] The watertightness of the reference samples has been proven in practice, and is therefore not investigated further. The sample of the material according to the invention likewise passed the test for leak-tightness with flying colours, wherein the sheet material was subjected to both a 10-metre static water column and a dynamic water jet at a water pressure of about 2 atmosphere. The sample comfortably complies with the standard.

[0027] Tensile Strength:

[0028] The tensile strength of the sample and of the reference samples was measured both in longitudinal and transverse direction. In respect of the sample, use was made here of the longitudinal direction and transverse direction relative to the production direction of the sheet material. These values were found to be substantially identical to each other. The elongation of the material was also determined. The test results are stated in table 2.1. It can be inferred herefrom that, in terms of tensile strength and elongation, the material of the sample according to the invention performs no worse and even better than the common commercially available materials which were subjected to the same test. The material according to the invention therefore comfortably complies with the standard.

TABLE-US-00002 TABLE 2.1 Property: PVB PVC EPDM FPO longitudinal Tensile strength 22 22 8 ≥9 [N/mm.sup.2] Elongation at break 230 ≥15 300 ≥550 [%] transverse Tensile strength 23 22 8 ≥7 [N/mm.sup.2] Elongation at break 230 15 300 550 [%]

[0029] Weld Strength:

[0030] Two strips of the test material are glued together in a prescribed manner, and the whole was then subjected to a tensile strength. Because bituminous materials are not glued but are welded (fused) to each other, this material was omitted from the comparison. The test results are shown in table 2.2. The strength of an adhesion of the sample according to the invention was found to be of the same order of magnitude as that of the reference samples, and lies comfortably within the standard.

TABLE-US-00003 TABLE 2.2 Property: PVB PVC EPDM FPO Maximum Weld strength 156 200 150 X [N]

[0031] Impact Resistance:

[0032] The resistance to mechanical impact was tested by dropping a sharp object onto the sample from a determined height. The maximum height from which an object can be released without perforating the sample is stated in table 2.3. This was tested with both a relatively hard object of aluminium and a softer object of plastic. This also shows that the material of the sample according to the invention is comparable to that of the reference samples, and falls within the standard.

TABLE-US-00004 TABLE 2.3 Property: PVB PVC EPDM FPO hard Maximum drop height 1250 ≥800 — 1250 [mm] soft Maximum drop height 2000 — 1000 1500 [mm]

[0033] Fire Retardance:

[0034] Finally, the sample material is exposed to a standardized fire test in order to thereby determine fire resistance. A standardized fire source with a temperature of around 800° C. was here placed on a sheet of 800 by 1800 millimetres, and a duration within which the material caught fire was measured. The fire went out completely after 12 minutes and 33 seconds. With this, the material according to the invention provides an outstanding fire retardance and resistance to heating. An additional advantage is that PVB does not give off toxic gases when it burns.

[0035] The foregoing justifies the claim that the material according to the invention meets the requirements of watertightness as set by the standard. The material according to the invention combines here a high tensile strength, such as that of PVC, with a great stretchability, such as that of EPDM. The strength of a weld (adhesion) in the material according to the invention is of the same order as the known commercially available materials and complies with the standard. The resistance to mechanical impact is at least as great as that of the other tested materials, or even higher. In the case of thicker sheet materials, from 1M millimetres, it was even found that the other materials could not match this property of the material according to the invention. The material according to the invention provides particularly good properties in terms of fire resistance, and is moreover not toxic when it burns.

[0036] Finally, a considerable cost reduction can be achieved with a roof covering on the basis of the PVB material according to the invention in that both the material costs and the costs for processing are significantly lower than those of roof covering materials common heretofore. In practice, it has been found that a roof covering with the material according to the invention can be placed considerably more quickly, up to two times faster. The invention thereby provides a particularly attractive alternative to these known roof covering materials; not least because the invention allows the use of reclaimed and reclaimable plastic (PVB).

[0037] Although the invention has been further elucidated above on the basis of only a single exemplary embodiment, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art.

[0038] Plasticizers in particular can thus be added to the sheet material in order to thereby improve the flexibility and processability. These plasticisers can be oily or glycol-like materials, but can for instance also comprise polymer plasticizers. Surprisingly, it has been found that the fire-retardant properties of the final construction material can thereby also be improved. This was particularly found when polymer plasticizers were applied, such as Elvaloy® ethylene/vinyl acetate/carbon monoxide (E/VA/CO) co-polymer.

[0039] Similar results were also achieved with other mutual ratios of the PVB, ammonium polyphosphate (APP) and ATH. These components can thus also be applied in a ratio of 100 PVB:40 ATH:4 APP. A colour can be added thereto, and one or more UV stabilizers and plasticizers can be mixed in. A compound with a proportion of 15% ATH and 15% APP relative to the used PVB likewise produced satisfactory results. The formulation according to the invention generally gives the skilled person the option of forming an outstanding new construction material, which can in turn also be recycled and renewed again afterwards, from PVB which may or may not be recycled, depending on the specific application. Besides roof covering, other structural applications are also possible, such as particularly an alternative to a lead flashing as water barrier for door and window frames and vents, and as a waterproof finish for cellar floors and watertight sheet material in underwater and sub-surface applications.