GB2078610A

GB2078610A - Improvements in or relating to laminated materials

Info

Publication number: GB2078610A
Application number: GB8021037A
Authority: GB
Original assignee: EPS Research and Development Ltd
Current assignee: EPS Research and Development Ltd
Priority date: 1980-06-26
Filing date: 1980-06-26
Publication date: 1982-01-13

Abstract

A five-layered laminated sheet 1 comprising a layer of thermoplastic polyurethane 2, a bonding layer e.g. of a nylon weave 3, a central layer of butyl rubber 4, a second bonding layer e.g. of nylon weave 5, and a second layer of thermoplastic polyurethane 6. The polyurethane confers oil resistance and scuff resistance on the laminate and, since it is thermoplastic, the laminate may be heat-welded. The butyl rubber confers impermeability to water vapour. <IMAGE>

Description

SPECIFICATION Improvements in or relating to laminated materials This invention relates to laminated materials.

It is known to provide enclosures acting as protective containers for heavy equipment, such as-military vehicles, which must be stored for long periods of time in an operational condition so that it can speedily be released from store and pressed into service. The enclosure must therefore protect the equipment, which may be sophisticated and delicate, from corrosion and other forms of deterioration which might result from the equipment being stored in a harsh atmosphere, for example one which is damp or acidic. Whilst it is possible to maintain a controlled low humidity atmosphere in conventional buildings, substantial savings in the cost of storage and in the time taken to prepare the equipment for service can be made if the equipment is stored in a large number of relatively small enclosures.For example, in the case of tanks, it is often desirable that each tank is surrounded by a relatively close fitting bag, with a consequent reduction in the total volume of controlled atmosphere which is associated with each tank.

Existing enclosures of this type are formed from a PVC (polyvinyl chloride) bag surrounding the top and sides of the equipment. The equipment is supported by a firm base, for example concrete, and the bag is effectively sealed to the base. It will be appreciated that in order to control the atmosphere within the bag efficiently it is necessary to provide the seal between the bottom edges of the bag and the base. A seal which has been utilised is in the form of a sliding clasp fastener which joins the bottom edge of the PVC bag to the top edge of a narrow strip of PVC which is in turn sealed at the bottom edge thereof to the base.Thus, when it is necessary to remove the equipment from the enclosure, the sliding clasp fastener is undone, the bag is lifted off and the narrow strip of material connected to the base is rolled down and out of the way, to permit the equipment to be removed from the base.

The advantages of using PVC for the bag are that (a) it is relatively scuff proof, (b) it is light and relatively cheap (c) it is highly moisture proof and (d) it is a thermoplastic material, and consequently it is easily handled during manufacture and it may be heat-welded. The feature of the ability of PVC to be heat-welded is important not only in the construction of the bag itself but also in the joining of the bottom edge of the bag to one half of the sliding clasp fastener.

A major disadvantage of using PVC for the bag is that protective enclosures for military equipment are required to operate satisfactorily in extremely cold climates, for example at a temperature of --400C. At this temperature, PVC is brittle and if the sliding clasp fastener is opened and the bag removed from the-equipment, the bag and the narrow strip may easily be damaged. This is clearly unsatisfactory.

It is an object of the present invention to provide a material, suitable for use in the formation of a protective bag.

According to one aspect of this invention there is provided a laminated material comprising: an inner layer of water-impermeable butyl rubber, two outer layers of thermoplastic polyurethane: and bonding layers, between said outer layers and said inner layer, to bond the inner and outer layers together.

Preferably the bonding layers each comprise nylon weave.

Suitably, there is a single bonding layer between each polyurethane layer and the butyl rubber layer.

According to another aspect of the invention, there is provided a laminated material comprising: an inner layer of water-impermeable material: two outer layers of a thermoplastics material: and means bonding the outer layers to the inner layer, said laminated material being flexible at 400 C.

According to a further aspect of the invention, there is provided a method of making a laminated material comprising the steps of: bonding a layer of thermoplastic polyurethane to an intermediate layer; forming a layer of rubber on said intermediate layer; curing said butyl rubber and bonding a second intermediate layer to the rubber before it is fully cured; and bonding a second layer of thermoplastic polyurethane to said second intermediate layer.

Preferably, the intermediate layers are nylon weave.

Suitably, the bonding of each polyurethane layer to the respective intermediate layer is achieved by heating the polyurethane layer and then pressing the polurethane layer and the respective intermediate layer together.

Conveniently, the layer of butyl rubber is formed by spreading the butyl rubber, in a liquid form, onto the intermediate layer.

The invention also encompasses a bag made from a laminated material in accordance with the invention.

So that the invention may be more readily understood and so that further features thereof may be appreciated, a laminated material will now be described by way of example and with reference to the accompanying drawings, in which; FIGURE 1 is a perspective view of a laminated material according to the invention with parts thereof cut away; FIGURE 2 is a perspective view of a sliding clasp fastener of a type which may be used to seal together temporarily two sheets of a laminated material according to the invention; and FIGURE 3 is a perspective view of a bag, formed from a laminated material according to the invention, and being used to protect a military vehicle.

As shown in Figure 1, a sheet 1 of laminated material in accordance with the invention comprises five layers, namely, a layer of polyurethane 2, bonded to a layer of nylon weave 3, which is in turn bonded to one side of a layer of butyl rubber 4, on the other side of which is a second layer of nylon weave 5 and, bonded to that, a second layer of polyurethane 6.

The laminated sheet 1 may be manufactured by warming a sheet 2 of the polyurethane and then pressing the nylon weave 3 onto the polyurethane.

The polyurethane 2 will thus be mechanically bonded to the nylon weave 3. Butyl rubber, in a liquid form, is then spread over the nylon weave and partially cured. Before the rubber 4 is completely cured, a second layer 5 of nylon weave is bonded to the rubber 4 and then the rubber 4 is fully cured. Thus the two layers of nylon weave 3, 5 are mechanically bonded to the butyl rubber 4.

Finally, a second warmed sheet 6 of polyurethane is pressed onto the second layer 5 of nylon weave so that it is mechanically bonded thereto.

The polyurethane may be made from a polyester or a polyether, but in either case it is, as a man skilled in the art will appreciate, a thermoplastic material, and can thus be welded by means of heat or R.F. welding or Pfaff welding.

The physical properties of the polyurethane are such that it has a good resistance to abrasion and is substantially impermeable to oil. However, it is relatively permeable to water vapour and thus if a bag were made entirely from polyurethane it would be difficult to maintain a dry atmosphere within the bag. Butyl rubber, on the other hand, has a low resistance to oil but is highly impermeable to water vapour, and thus by combining the layer of polyurethane and the layer of butyl rubber in the laminate, it is possible to achieve a sheet of material which is impermeable to both oil and water. Butyl rubber is a thermosetting material and thus cannot be heat welded but since the complete laminate is provided on each face with a sheet of polyurethane, which can be heat welded, the result is that the complete sheet of laminate material can be heat welded.Both the polyurethane and the butyl rubber remain flexible at -400C, and the laminate is also flexible and is thus a suitable material for the construction of a bag for protecting military equipment at such a low temperature.

It is not practicable to bond a sheet of polyurethane directly to a sheet of butyl rubber and thus it is necessary to have some intermediate layer of material between the polyurethane and the sheet of butyl rubber, to which intermediate layer both polyurethane and butyl rubber can be bonded. Nylon weave is such a material. The nylon weave has the advantage that it endows the laminated material with a degree of resistance against distorting forces, since nylon weave is virtually inextensible. This degree of resistance is desirable since both the polyurethane and, especially, the butyl rubber are liable to stretch in an inconvenient manner. The elasticity of the laminate as a whole can be controlled by varying the characteristics of the nylon weave, for example by altering the density of the threads in the weave.

In a sheet of material constructed in accordance with the invention which is 0.762 mm thick it has been found that the degree of impermeability of the laminate to water is very good, even at low temperatures.

Because the two outside layers 2, 6 of the laminate are made from a thermoplastic material, the material may easily be welded together. Also, the mouth of a bag constructed from the laminate may be welded to one half of a sliding clasp fastener, an example of which fastener is shown in Figure 2.

The fastener 7 comprises two inter-engaging strips, one male 8 and one female 9, which may be engaged and disengaged by means of a slider 10. The strips 8, 9 are conveniently extruded from a length of resilient plastics material, such as polyurethane, but may alternatively be injection moulded. One strip 8 is welded to the bottom edge 11 of the bag 1 2, and the other 9 is welded to a relatively narrow strip 1 2 of the laminate which is in turn bonded to a concrete base 14 forming part of an enclosure for the vehicle 15, as shown in Figure 3. Thus, the enclosure can be swiftly constructed around a vehicle or other piece of equipment and, equally, can be swiftly removed when it is necessary to press the vehicle or equipment into service.

Claims

1. A laminated material comprising: an inner layer of water impermeable butyl rubber; two outer layer of thermoplastic polyurethane; and bonding layers, between said outer layers and said inner layer, to bond the inner and outer layers together.

2. A laminated material according to claim 1, wherein the bonding layers each comprise nylon weave.

3. A laminated material according to claim 1 or claim 2, wherein there is a single bonding layer between each polyurethane layer and the butyl rubber layer.

4. A laminated material comprising: an inner layer of water impermeable material; two outer layers of a thermoplastics material; and means bonding the outer layers to the inner layer, said laminated material being flexible at --40"C.

5. A method of making a laminated material comprising the steps of: bonding a layer of thermoplastic polyurethane to an intermediate layer; forming a layer of butyl rubber on said intermediate layer; curing said butyl rubber and bonding a second intermediate layer to the rubber before it is fully cured; and bonding a second layer of thermoplastic polyurethane to said second intermediate layer.

6. A method according to claim 5, wherein the intermediate layers are nylon weave.

7. A method according to claim 5 or claim 6, wherein the bonding of each polyurethane layer to the respective intermediate layer is achieved by heating the polyurethane layer and then pressing the polyurethane layer and the respective layer together.

8. A method according to any one of Claims 5 to 7 wherein the layer of butyl rubber is formed by spreading the butyl rubber, in a liquid form, onto the intermediate layer.

9. A laminated material substantially as herein described with reference to, and as shown in, the accompanying drawings.

10. A method of making a laminated material substantially as herein described with reference to the accompanying drawings.

11. A bag made from a laminated material according to any one of claims 1 to 4 and 9.

12. Any novel feature of combination of features herein described.