GB2244231A - Cutting of cured resin based articles - Google Patents

Abstract

An article, e.g. a laminated glazing product, comprising a cured resin material is broken along a breakage line when in an embrittled condition caused by lowering its temperature, e.g. to below 0 DEG C. A laminated glazing product is scored along the breakage line on at least one face prior to lowering the temperature of the cured resin interlayer(s), to that at which its/ their hardness is similar to that of the center layers, if these are glass.

Description

CUTTING OF CURED RESIN BASED ARTICLES This invention relates to a method of cutting an article comprising a cured resin based material. In particular, but not exclusively, the article comprises a laminated glazing product comprising at least two spaced apart glass panes and an interlayer of said cured resin based material bonding together the or each adjacent pair of spaced apart glass panes.

There are two main established methods of manufacturing laminated glazing products. One method involves placing an extruded resin sheet, usually of polyvinylbutyrate, between two panes of glass and heating and compressing the product in an autoclave so that the resin sheet softens and provides an interlayer which bonds the glass panes together. The other method involves pouring or injecting settable liquid resin material between two spaced-apart glass panes to form an interlayer which subsequently cures or sets to form the laminated glazing product. In either case the interlayer formed between the two glass panes creates a reasonably tough adhesive barrier which serves, when the glass breaks, to retain the broken glass fragments.The interlayer is able to perform this function because, in addition to its adhesive properties, it also has a much higher modulus of elasticity than glass and is thus able to absorb without breakage impacts which break the much harder or brittle glass panes.

Although the provision of a resin interlayer improves the safety properties of a laminated glazing product, its very presence creates difficulties when cutting the laminated glazing product. Normally the cutting of a single piece of glass present few problems and is carried out by scoring the surface with a diamond or wheel cutter and then opening the cut to cause the glass to fracture along the score line. However the conventional method of cutting a laminated glazing product is more complex and initially entails scoring both surfaces of the glazing product along the line that the laminated glazing product is to be cut.

Each glass pane on opposite sides of the laminated glazing product is fractured along the score line and the laminated glazing product is opened up as much as the adhesive interlayer will allow along the length of the cut. Heat is then applied along the breakage line either by means of an electric element or by burning a reasonably safe flammable liquid, such as methylated spirits, along the breakage line. The latter is the more common method, with the laminated glazing product being laid flat and flammable liquid being sprinkled on the upper surface of the laminating glazing product along the scored and opened up cut line and then lit. The flammable liquid burns for a short period of time, e.g. a minute, before self extinguishing.

In this time the resin interlayer is softened by the heat and the laminated glass can then be moved or continually flexed until the cut has opened sufficiently to allow the interlayer to be cut, e.g. with a thin blade or razor, or, depending on the amount of flexing, to be torn apart.

The present invention aims to provide a new method of cutting an article comprising a cured resin based material.

In the specific case where the article is a laminated glazing product comprising at least two spaced apart glass panes and an interlayer of the resin based material bonding together the or each adjacent pair of spaced apart glass panes, the method is faster and more economical than conventional method and involves making the inter layer in the region of the cut much harder and brittle, typically as close to the hardness of glass itself as possible, as opposed to the conventional method of heating the interlayer to render it softer and more pliable.

According to one aspect of the present invention a method of breaking along a breakage line an article comprising a cured resin material, is characterised in that the temperature of the resin material is lowered to embrittle it thereby facilitating breakage of the article along the breakage line.

The article may be in extruded form and made of acrylic, polycarbonate, PERSPEX or the like. Preferably however, the article is in the form of a laminate, e.g. a laminated glazing product formed of spaced apart glass panes bonded together by an interlayer of said cured resin material.

According to another aspect of the present invention a method of breaking along a breakage line a laminated glazing product having at least two spaced apart glazing panes and an interlayer bonding together the or each adjacent pair of spaced apart glazing panes, comprising changing the temperature of the interlayer(s) along the breakage line to alter the hardness of the interlayer(s) thereby facilitating subsequent breakage of the interlayer(s), is characterised in that the temperature of the interlayer(s) along the breakage line is (are) lowered to a temperature sufficient to embrittle the interlayer(s).

Preferably the laminated glazing product is scored along at least one, preferably both, of its opposite sides along said breakage line prior to breaking the laminated glazing product.

Preferably the interlayer(s) is (are) lowered to a temperature of from -2000C to 0 C. When the glazing panes are made of glass, the lowering of the interlayer temperature makes the hardness of the interlayer(s) close to that of the glass.

The lowering of the temperature of the or each interlayer may be achieved in a variety of ways. For example the laminated glazing product may be sprayed along the breakage line with any suitable liquid or gas, e.g. liquid nitrogen. Alternatively the laminated glazing product may be at least partially immersed in a cool liquid, e.g.

liquid nitrogen, for a period of time.

The laminated glazing product may be a laminated wired glass incorporating conventional steel wires or coloured wires embedded in the, or one of the, interlayer(s). The interlayer may be a cured liquid resin or polyvinylbutyrate. The laminated glazing product may comprise a wired monolithic glass, e.g. wired roughcast glass, laminated to another glazing panel.

According to a further aspect of the present invention a laminated glazing product having at least one peripheral edge that has been trimmed by the method of breakage according to said another aspect of the present invention.

An embodiment of the invention will now be described with reference to the following non-limitative example.

EXAMPLE A 3m by 2m rectangular first glass panel having a thickness of 2.4 mm was placed on a horizontal support surface and double-sided adhesive tape was adhered to the upper face of the first glass panel adjacent each of its four peripheral sides. A removable backing layer was left on the upper adhesive layer of the adhesive tape. A rectangular second glass panel of similar size and thickness to the first glass panel was then placed on top of the latter so as to be supported by the double-sided adhesive tape. The backing layer was then removed from the adhesive tape applied along three of the four sides so that the two glass panels were adhered together along three of their four common sides by the adhesive tape sandwiched therebetween. The adhesive tape, in addition to adhering the two glass panels together, also served to peripherally seal the glass panel assembly in a liquid tight manner and to space the glass panels apart by approximately 1.2 mm.

The glass panel assembly was then moved into an inclined or upright position with its unsealed edge uppermost and settable liquid resin material was introduced through the uppermost edge between the two glass panels.

After a measured quantity of resin material had been introduced between the glass panels, the backing layer from the adhesive tape along the fourth side of the glass panel assembly was removed to adhere and seal together the glass panels therealong. At least one air hole was left along the fourth edge of the glass panel assembly to allow air to escape from between the glass panels as the liquid resin spread therebetween on moving the glass panel assembly down from its inclined or upright position. When liquid resin material reached the air hole(s), these were sealed with a sealing material and the assembly was left in a horizontal position to enable the resin material to cure.After about 1 hour the resin material had cured to form a laminated glazing product consisting of a pair of spaced apart glass panels bonded together by a resin interlayer and provided with adhesive tape sandwiched between the glass panels around its periphery.

It was then necessary to trim the laminated glazing product around its periphery to remove the adhesive tape.

This was achieved by scoring opposite faces of the glazing product along each of its four sides approximately 30mm in from the respective edges. Each face of the glazing product was then sprayed with liquid nitrogen along each score line to reduce the temperature of the resin interlayer to a temperature of about -200C to embrittle the interlayer. The four edges of the laminated glazing product were then snapped off without the need to heat the resin interlayer to soften the interlayer, the extremely low temperature of the interlayer enabling the product to break easily along the glass score lines.

Other sprays may be used to lower the temperature of the resin layer to a temperature below 0OC although liquid nitrogen, being readily, and relatively cheaply, available is preferred. The time taken to reduce the resin interlayer temperature to the desired low temperature in which the resin interlayer has a brittleness comparable with that of the glass panels will of course vary in dependence on the spray fluid being used, the thickness and material of the interlayer and the thickness of the glass panels. In general, however, for a glass laminate of approximately 6 mm thickness, one pass along and one pass back along the score lines lowers the temperature of the resin interlayer sufficiently to break it apart.

In certain applications, it may be possible to eliminate the need to score the laminated glazing product along both of its sides. Thus the product may need only to be scored on one of its two faces to enable subsequent breakage along the breakage line.

The method of curing described above dramatically lowers the time required to cut laminated glasses of any description in any size and thickness or number of interlayers or plies. Particularly thick and expensive laminates can be cut more easily if they are totally immersed in liquid nitrogen in a special container for a period of time instead of being sprayed with liquid nitrogen. As glass is not generally considered a good thermal conductor, thick laminates may take a relatively long time to sufficiently decrease in temperature. Thus cooling by immersion in cool liquid is found to be. quicker and more efficient than cooling by spraying. Liquid'nitrogen has advantages over cold liquid sprays, in that the temperature of the resin interlayer can be reduced to much lower values, it is generally efficient and is relatively cheap compared with cold liquid sprays.

Although the invention has been described specifically, and with respect to its preferred application, with regard to the cutting or trimming of laminated glass, it will be appreciated that the invention can be applied to the cutting or trimming of any article comprising a cured resin material. For example the invention can be used to cut sheets of cured resin material, such as sheets of polycarbonate material, acrylic material or PERSPEX.

Claims (8)

1. A method of breaking along a breakage line an article comprising a cured resin material, characterised in that the temperature of the resin material is lowered to embrittle it thereby facilitating breakage of the article along the breakage line.

2. A method of breaking along a breakage line a laminated glazing product having at least two spaced apart glazing panes and an interlayer bonding together the or each adjacent pair of spaced apart glazing panes, comprising changing the temperature of the interlayer(s) along the breakage line to alter the hardness of the interlayer(s) thereby facilitating subsequent breakage of the interlayer(s), characterised in that the temperature of the interlayer(s) along the breakage line is (are) lowered to a temperature sufficient to embrittle the interlayer(s).

3. A method according to claim 2, characterised in that the laminated glazing product is scored along at least one of its opposite sides along said breakage line prior to breaking the laminated glazing product.

4. A method according to claim 2 or 3, characterised in that the or each interlayer is lowered to a temperature of from -2000C to 0 C.

5. A method according to claim 2, 3 or 4, characterised in that the glazing panes are made of glass, and the temperature of the or each interlayer is lowered to a temperature at which the hardness of the interlayer is close to that of the glass.

6. A method according to any one of claims 2 to 5, characterised in that the temperature of the or each interlayer is lowered by spraying along the breakage line with any suitable cooling liquid or gas.

7. A method according to any one of claims 2 to 5.

characterised in that the laminated glazing product is at least partially immersed in a cooling liquid for a period of time to lower the interlayer temperature.

8. A laminated glazing product having at least one peripheral edge that has been trimmed by the method of breakage according to any one of claims 2 to 7.