NZ235772A

NZ235772A - Moisture barrier laminate has two outer layers of linear low density polyethylene and a core layer of high density polyethylene formed as a folded roll with single layer offset fold

Info

Publication number: NZ235772A
Application number: NZ23577290A
Authority: NZ
Inventors: Alexander Charles Wood; Edward Albert Christiansen
Original assignee: Conform New Zealand Ltd
Priority date: 1990-10-19
Filing date: 1990-10-19
Publication date: 1997-12-19
Also published as: AU8577291A

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number £35772 Patents Form No 5 2 3 5 7 ? - _Aoa^% ; Patents Act 1953 COMPLETE SPECIFICATION Number: 235772 Date: •<* •©. <k> "MOISTURE BARRIER LAMiNATE" We, Conform New Zealand Limited, a New Zealand Company, of 6 Mahunga Drive, Mangere, Auckland, New Zealand, hereby declare the invention, for which we pray/, that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- -1 050723. M3 235 This invention relates to a plastics mu/tilayered film laminate. A particular application in which the laminate is very advantageous is as a moisture barrier laid on the ground underneath cast concrete slabs. Other moisture barrier applications in the building industry are also advantageously met by the laminate of the invention. Building regulations generally require that cast on ground concrete slabs have specified moisture barriers placed between the concrete and the underlying ground. The use of such barrier layers is specified in, for example, New Zealand Standard 3604 which covers a single unprotected polyethylene film layer. The laminate of the invention has increased toughness arid puncture resistance enabling it to be used in applications at 40% lower thickness than existing polyethylene films and it also has advantages over previously used polyethylene/kraft paper/bitumen laminates. During the installation of moisture barrier films prior to laying concrete, it is important that the barrier is not left broken due to damage from rough soil, broken stone or the like. Any breaks or tears in such films has to be repaired by adhesive tape. With presently used films, their colour Is not suitable to enable breaks to be easily seen as the upward feeing colour of the film does not contrast with underlying ground colours. The invention consists of a multilayered plastics film for use as a moisture and vapour barrier underlay in which the film comprises two exterior layers and at least one core layer, each layer being intimately bonded to its adjacent layer and wherein both exterior layers comprise linear low density polyethylene or a LLDPE/LDPE blend and the core layer comprises high den~uy polyethylene. To facilitate handling on building sites the film is provided for use in the form of a longitudinally inwardly folded roll with the fold slightly off-centre of the film width to provide a single thickness overlap at one edge of the roll. The thicknesses of each one of the, exterior linear low density polyethylene layers may be varied in the range 15-40% or the total thickness, the core layer of high density polyethylene comprising the remainder. Preferably the first exterior layer is coloured to provide an effective colour contrast with common soil and rock colours. Preferably that first exterior layer is coloured from amongst shades of blue. Preferably the colour of the second exterior layer of the film is selected <om amongst shades comprising black pigmentation including shades of grey. . ~% 2 \-,V f~8 DEC 1994 • 1*' 2o v) Preferably the exterior layers are differently coloured from each other. Preferably the 5 previously mentioned longitudinal fold is in range of 20-50mm off-centre. Preferably the first exterior layer is inwardly facing when the plastics film is rolled up. Preferably when the film is unrolled and unfolded the first exterior layer feces upward. 10 The foregoing features of the plastics film are further described in respect of a particularly preferred example and variations thereof, the reasons for the described features and the preference for other features being described in relation to the use of the example. The film structure preferably has a thickness of 0.15mm comprising 25% of the total thickness as linear low density polyethylene or a Linear Low Density/Low Density Polyethylene blend on one face, 50% high density polyethylene as the core 15 layer and 25% linear low density polyethylene or Linear Low Density/Low Density Polyethylene blend on the opposite exterior face. Preferably the first LLDPE face is coloured blue and the second LLDPE surface is coloured black. The layer ratios may extend from in the range 15-40% thickness for each exterior layer and thus between 20-70% for the core layer. 20 The film is preferably manufactured by coextruding the respective resins through a circular extrusion die followed by an inflation process to stretch the film to the required total circumference followed immediately by a cooling and rolling operation whereby the film as rolled is slit to produce a single longitudinal fold and overall width of rolled film (folded) of 1035mm where the total width of the film when unfolded is about 2 metres for example. 25 The longitudinal fold is formed 35mm off-centre. Greater widths can be supplied, perhaps up to 5 metres wide when unfolded, with in each case a longitudinal fold about 35mm off-centre. The external layer of LLDPE coloured blue is preferably extruded facing inwardly through the die so that it is folded inwarded in the rolled form as supplied to the user. 30 When the film is unrolled on a building site in readiness for having a concrete slab cast on top of it, it is convenient that the end of the roil can be placed with the inwardly rolled face upwards so that the remainder of the roll can be easily unrolled and subsequently unfolded blue face up. Where multiple widths are required in the construction of large floor areas the 35mm overlap (blue face upwards) can be aligned before unrolling the 35 roll and, after unrolling, the overlapping edge can be 40 -3 • * w • * J </div>

Claims

<div class="application article clearfix printTableText" id="claims">
2*3 i»* 7 7 taped to the adjacent film over which the overlap extends lies. The overlap allows this taping process to be carried out before the rolled out length of film (typically 50 metres) is unfolded. This has the advantage that any necessary walking on the film to place the tape in position can be carried out while the film 5 is at double thickness and thereby more resistant to accidental puncturing by foot traffic in combination with sharp objects under the film. The film as described possesses considerable puncture resistance due to Its construction and may be used, successfully in building operations at a 40% lesser thickness than single material plastics films hitherto in use. In laying film prior to casting concrete the 10 aligning necessary of the film Is easier before unfolding than after it is . unfolded. Also, In its folded state the film Is less prone to movement on a building site caused by windy conditions. As a further improvement to the above described film a pre-applied adhesive means 15 may be attached to the upward facing edge of the 35mm wide overlap. The adhesive means may be either a thin layer of a hot melt adhesive that exhibits a surface tackiness over normal climatic temperature ranges such as 5 to 35°C, or pressure sensitive adhesive tape in either case being protected prior to use by being covered with a peei-off release tape. This provides an advantage of not requiring separate 20 tape to join the overlapping edges and facilitates the edge to edge joining of multiple widths of film on site. 25 30 35 40 -4- WHAT WE CLAIM IS: 23b// A multilayered plastics film for use as a moisture and vapour barrier underlay in which the film comprises two exterior layers and at least one core layer, each layer being intimately bonded to its adjacent layer and wherein both exterior layers comprise linear low density polyethylene or a Linear Low Density/Low Density Polyethylene blend and the core layer comprises high density polyethylene and wherein the film is provided for use in the form of a longitudinally inwardly folded roll with the fold slightly off-centre of the film width to provide a single thickness overlap at one edge of the roll. A multilayered plastics film as claimed in the previous claim in which each layer is . intimately bonded to its adjacent layer as a result of having been formed in a co-extrusion process. A multilayered plastics film as claimed in any one of the previous claims in which the thicknesses of each one of the exterior linear low density polyethylene layers is in the range 15 to 40% of the total thickness, the core layer of high density polyethylene comprising the remainder. A multilayered plastics film as claimed in any one of the previous claims in which the first exterior layer is coloured to provide an effective colour contrast with common soil and rock colours A multilayered plastics film as claimed in any one of the previous claims in which the colour of the first exterior layer is selected from amongst shades of blue. A multilayered plastics film as claimed in any one of the previous claims in which the exterior layers are differently coloured from each other. A multilayered plastics film as claimed in claim 6 in which the colour of the second exterior layer is selected from amongst shades comprising black pigmentation including shades of grey. A multilayered plastics film as claimed in any one of the previous claims in which the longitudinal fold is in the range of 20-50mm off-centre. A multilayered plastics film as claimed in claim 8 in which the longitudinal fold is in the range 30-40mm off-centre. 10. A multilayered plastics film as claimed in claim 1 in which the single thickness overlap is provided on its surface common with the inwardly rolled surface with pre-applied contact adhesive means protected prior to use by covering with a peel-off release tape. 11. A multilayered plastics film as claimed in any one of the previous claims in which the first exterior layer is inwardly feeing when the film in the form of a roll. 12. A multilayered plastics film when used as a moisture and vapour barrier underlay in which the film comprises two exterior layers and at least one core layer, each layer being intimately bonded to its adjacent layer and wherein both exterior layers comprise linear low density polyethylene and the core layer comprises high density polyethylene and wherein the film is provided for use in the form of a longitudinally inwardly folded roll with the fold slightly off-centre of the film width to provide a single thickness overlap at one edge of the roll. 13. A multilayered plastics film as claimed In any one of the previous claims in which the total film thickness does not exceed 0.15mm. C LAND LIMITED ^Per John Barr MANAGER END OF CLAIMS 050723 -6- </div>