GB2191116A

GB2191116A - Bitumen containers

Info

Publication number: GB2191116A
Application number: GB08613367A
Authority: GB
Inventors: Raymond Dashwood Smith; Peter Andrew Wright; Arthur James Phillips
Original assignee: Reed Packaging Ltd
Current assignee: Reed Packaging Ltd
Priority date: 1986-06-03
Filing date: 1986-06-03
Publication date: 1987-12-09
Also published as: EP0249379A2; GB8613367D0; EP0249379A3

Abstract

There is provided a bitumen container having on the interior surface a radiation cured acrylate-based bitumen release coating 13. Such release coatings can be applied to the web substrate 3 from which the container is formed easily and economically using conventional printing techniques. A method of forming bitumen containers by coating a substrate 3 with a radiation curable acrylate based material followed by radiation curing is described and claimed. <IMAGE>

Description

1

GB 2 191 116 A

1

SPECIFICATION Containers

5 The present invention relatestocontainersforbit-umen, in particularto containers for hot-filled blown bitumen and to a method for the preparation of such containers.

Blown bitumen is often transported in bitumen 10 kegs. These kegs conventionally are supplied in the form of flattened, open-ended, heavyweighttubes (hereinafter called bitumen keg tubes), e.g. of kraft paper, onto which a metal base is seamed before the resulting keg is hot-filled with the bitumen. To allow 15 ready release of the solid bitumen from the filled kegs, the bitumen keg tubes are provided on their interior surface with a silicone-based release coating.

The conventional silicone release coatings, which 20 are capable of withstanding the temperatures involved in the hot filling of the kegs and which provide adequate release characteristics, may be applied to the substrate webs from which the tubes are formed by routine coating techniques. Howeverthe drying 25 time of conventional silicone release coating materials limits the production rateforthe bitumen keg tubes, or more generally forthe blanks from which the tubes are formed.

We have now surprisingly found that certain radia-30 tion-curable varnishes, in particular acrylate-based varnishes, are capablewhen cured notonly of providing a good release surface for solid bitumen but also of withstanding the temperatures experienced in the hot filling of bitumen containers with blown 35 bitumen. The use of such radiation-curable varnishes in the manufacture of bitumen containers has the major advantage that the varnishes may be applied and cured rapidly, for example using offset litho printing techniques.

40 Viewed from one aspect, the present invention thus provides a bitumen container having provided on the interior surface thereof a radiation cured acrylate-based bitumen release coating.

The bitumen container of the present invention 45 may conveniently have as the substrate material to which the acrylate-based release coating is applied a paper, card, board or laminate web material, of a thickness and strength adequate to retain the weight of bitumen to be filled into the container. Clay-50 coated, sized or well-finished paper or board and laminates including laminae chosen for example from metal (e.g. aluminium) foils, plastics webs and cellulosic webs are particularly preferred. As in the conventional bitumen kegs, the substrate may of 55 course be kraft paper.

The radiation-cured acrylate-based release coating is formed by coating the substrate material, pre-ferablywhilst still intheform of a continuous web or of discrete sheets, with a radiation-curable acrylate-60 based varnish and bythenexposingthecoated substrate to curing radiation. If, as would generally be the case, the substrate receiving the varnish is in sheet or continuous webform, the substrate bearing the cured coating will then, if necessary afterfirst 65 being cut into sections of the desired size, be formed into liquid-tight containers with the coating on the interior surfaces, or alternatively into open-ended bitumen keg tubes with the coating on the interior surfaces which, as with conventional bitumen keg 70 tubes, may have a metal base seamed onto one end to form a liquid-tight bitumen keg.

Viewed from anotheraspect therefore, the present invention provides a method of preparing a bitumen container comprising: applying to a surface of a web 75 substrate a radiation-curable, acrylate-based varnish; exposing the varnish carrying surface of said substrate to curing radiation to cure the varnish to form a bitumen release coating; if required, cutting the bitumen release coating carrying substrate into 80 sections of a desired size; andforming the bitumen release coating carrying substrate into a liquid-tight container having the bitumen release coating on the interior surface thereof.

Thevarnish used according to the presentinven-85 tion is conveniently a UV-curable or electron beam-curable varnish, preferably a polyester acrylate-based varnish. The varnish may, if desired, contain a photo-initiatorto assist cross-linking of the curable polymer component on exposure of the varnish to 90 radiation. In this respect, conventional radiation-curable, acrylate-based varnishes such as 600201 available from Shackell Edwards may for example be used. Such varnishes, which intheirconventional use are applied to a printed surface to enhance its 95 gloss and to protect the print from rubbing and scuffing, have in the present invention the particular advantage thatthey are operator acceptable materials from the health and safety point of view.

Thevarnish may be coated onto one entire surface 100 of the substrate web, or alternatively may be coated onto only that part of the surface which is to form the interiorsurface ofthefinished container. Inthisway unvarnished areas are left which may readily be bonded to other unvarnished surfaces of the substrate in 105 the final step of folding and adhesive bonding the substrate blanks to form the finished containers or the bitumen keg tubes. If such unvarnished areas are not left then special adhesives capable of bonding to the varnished surfaces may be required; however 110 such special adhesives are known, one example being Superlok60, a polyvinyl acetate-based adhesive available from National Adhesives and Resins.

A particular advantage of the present invention lies in the ease and rapidity with which the bitumen 115 release coating may be formed on the substrate web. Thus, while conventional coating techniques such as spraying may be used, the method of the present invention is particularly suited to the use of printing techniques, and especially offset litho printing tech-120 niques,toformthe release coating. The acrylate-based varnish may therefore be printed onto the substrate to cover as much or as little of the substrate surface as is desired. Conventional printing apparatus, forexample offset litho printing apparatus 125 supplied by M.A.N. Roland Druckmaschinen AG, may readily be provided with curing radiation sources arranged to direct curing radiation onto the varnish-coated surface of the substrate after application of the varnish to the substrate at the or a printing 130 station of the apparatus. The precise positioning of

2 GB2 191 116 A

2

the curing radiation sources is not critical; it is only necessary thatthe radiation sources directsufficient radiation onto the varnish-coated substrate surface to cause curing to take place.

5 One embodiment of the present invention will now be described byway of example with reference to the accompanying drawings, in which:-

Figure 1 shows a schematic side elevation of a printing apparatus arranged to apply a bitumen re-10 lease coating to substrate sheets which can subsequently be formed into bitumen containers according to the invention;

Figure 2 shows a plan view of a substrate sheet from which a bitumen container according to the in-15 vention maybeformed; and

Figure 3 shows a perspective view ofa bitumen container according to the present invention formed from the sheet of Figure 2.

Referring to Figure 1, there is shown an offset litho 20 printing apparatus 1 having asheetsupply unit2 arranged to supply substrate sheets 3, for example sheets of paper or card, to a printing station4at which a UV-curable acrylate-based varnish is printed onto the upper surface of the sheets by print roll 5 25 which is itself supplied with the varnish by inker roll 6. Sheets leaving the printing station are engaged by gripper bars 7 attached to a conveyor 8 and aretrans-ported thereby past a curing station 9 to a sheet receiving and stacking unit 10. At the curing station 9, 30 the varnish coated surfaces of the sheets are exposed to UV radiation from an array of UV-emitting lamps 11 disposed transversely to the sheet transport direction. Typically, the curing lamps will extend for at least thefull width of the sheets and will 35 be provided with reflectors 12 to increase the radiation intensity directed atthesheets.

Where 600201 varnish is applied to the surface of 1 metre square sheets passing through the apparatus at a rate of 4- 5,000 sheets per hour, the UV-curing 40 array mightsuitably comprise three UV-emitting lamps, each 56" (142 cm) long and each rated at 250 Watts/inch, i.e. a total of 42kW.

As an alternative to the conventional 600201 varnish, use may instead be made of varnishes based on 45 UV-curable, acryl-modified siloxanes.

A sheet 3 having a cured release coating 13 and with corner portions 14 removed is shown in plan in Figure 2. To produce thefinished bitumen container, as shown in Figure 3, an adhesive (such asforex-50 ample Superlok60) is applied along the uncoated margins 15and 16 of sheet 3. The sheet may then be folded first along line A-A', then along line B-B'and finally along lie C-C' to bring the adhesive into contact with unvarnished surfaces of the sheet and 55 thereby form a liquid tight bitumen container.

It will be appreciated that while the present invention has been described with particular reference to liquid-tight bitumen containers and their preparation, the scope of the invention also includes bit-60 umen keg tubes having provided on their interior surface a radiation-cured acrylate-based bitumen release coating as well as the preparation of such bitumen keg tubes.

65

Claims

1. A bitumen container having provided on the interiorsurface thereof a radiation cured acrylate-

70 based bitumen release coating.

2. Acontainerasclaimedinclaim 1 whereinsaid release coating is of an ultraviolet- or electron beam-cured polyester acrylate based varnish.

3. Acontainerasclaimedineitherofclaimsl and 75 2 which comprises a substrate sheet coated on at least part of one surface with said release coating and folded and adhered to produce a liquid tight container.

4. A bitumen container substantially as herein 80 described with reference to the accompanying drawings.

5. The use ofa container as claimed in any one of claims 1 to 4 for containing bitumen.

6. A bitumen keg tube having provided on the in-85 teriorsurface thereof a radiation cured acrylate-

based bitumen release coating.

7. A keg tube as claimed in claim 6 wherein said • release coating is of an ultraviolet-or electron beam-cured polyester acrylate based varnish.

90

8. A method of preparing a bitumen container comprising: applying to a surface of a web substrate a radiation-curable, acrylate-based varnish; exposing the varnish carrying surface of said substrate to curing radiation to cure the varnish to form a bit-95 umen releasecoating; if required, cutting the bitumen release coating carrying substrate into sections of a desired size; and forming the bitumen releasecoating carrying substrate into a liquid-tight container having the bitumen releasecoating on the 100 interiorsurfacethereof.

9. A method as claimed in claim 8 wherein as said varnish is used an ultraviolet- or electron beam-curable polyester acrylate based varnish optionally containing a photoinitiator. 105

10. Amethodasclaimedineitherofclaims8and 9 wherein said varnish is applied to at least that part of the surface of said web substrate which is to form the interior surface of the finished container.

11. A method as claimed in any one of claims 8 to 110 10 wherein said varnish is printed onto sheets of said web substrate.

12. A method as claimed in any one of claims 8 to 11 wherein said web substrate is provided with fold lines along which said web substrate may befolded

115 to form said liquid-tight container.

13. A method of preparing a bitumen container substantially as herein described with reference to the accompanying drawings.

14. A bitumen container blank comprising a web 120 substrate sheet provided on at least the bitumen contact surface with a radiation cured acrylate based bitumen release coating and provided with a plurality of fold lines.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd, 10/87, D8991685.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1AY, from which copies may be obtained.