GB2110956A - Wallcovering - Google Patents

Abstract

A prepasted chemically foamed wallcovering is formed from a foamable web by gravure printing the web and then gravure pasting the web after reversal with water swellable polymer dispersed in an organic medium followed by heating to expand the web.

Description

SPECIFICATION Wallcoverings The invention is concerned with the subject of prepasted wallcoverings and is aimed at providing apparatus and a process for making prepasted chemically foamed wallcoverings.

A process already used for making prepasted foamed wallcovering involves conducting sub -processesatthree locations, namely: Location No. 1 Un-reel foamable web; print; re-reel and take to Location No. 2.

Location No. 2 Un-reel printed foamable web; heat to foam; re-reel.

Location No. 3 Un-reel printed foamable web; prepaste; piece wind.

This already used process has potential problems points. For example, any damage occurring after printing (such as may arise in handling, transport and storage of reels) is damage to a product to which significant value, namely the printing, has been added. Any damage occurring after foaming involves loss of even greater value. Further a foamed web is soft or bulky and is susceptible to damage and is not suitable for conventional storage as a reel free-standing on a floor as the foam in proximity to the floor becomes crushed. Thus it is the practice to support reels of foamed web on centre supports mounted on blocks which is more troublesome than free-standing storage.

The present invention provides an improved process which, whilst not removing all the problem points, at least reduces them.

The new process is primarily a line process and hence avoids at least some of the re-reeling processes referred to above. In this way damage hazards such as may arise in handling, transport and storage of reeled products are reduced. The new process also retains the procedure of printing prior to prepasting and hence avoids risks from printability problems such as may arise due to: a) Adhesive inadvertently reaching the print surface; b) Disturbance to the printing surface due to an intermediate process impairing print; c) Inability to sustain register due to presence of prepaste on the reverse side of the web.

The process according to the present invention is a process which requires at the most, two locations with one rewind between locations as follows: Location No. 1 Unreel foamable base web and print; reverse the printed web; prepaste with an adhesive capable of providing remoistenable features after tolerating heat conditions to be encountered during a subsequent foaming step (typically 180 - 220"C for 15 to 40 seconds) and re-reel.

Location No. 2 Heat to foam and piece wind.

(For reference purposes the early art processes of prepasting are seen in GB 588 554,605 438,606 648, 626290, 752,869 422. These processes have been generally replaced with a two-coat system disclosed in USP 3 122446 which, in turn, is likely to be replaced by prepasting with adhesives derived from inverse emulsions as disclosed in EP 0 008 213 and GB 2054 628A).

It is preferred that both printing and prepasting is carried out by gravure orflexo processes. This becomes possible for example, in a multi-station machine with the last of the stations being used for prepasting after web reversal.

One process according to the present invention, and apparatus for carrying out the process, will now be described with reference to the accompanying diagrammatic drawing.

In the drawing a gravure printing machine 10 is shown with six printing stations 11a, llbetc. to 11 f.

This machine (which effectively forms Location No. 1 of the above statement of invention) is supplied with a web 12 of substrate 12a, having afoamable plastisol coating 12b, from a reel 13. At stations 11 a, 1 1b b 11 . . . e, print 12c is applied. After the station 11e, the web 12 passes through a cross-roll reversing station 14 before entering station 11 fwhere an adhesive 1 2d in the form of a water swellable polymer dispersed in an organic medium is applied.

This is subsequently dried and the web 12, now printed and pasted, is re-reeled on to a reel 15. The reel 15 is conveyed to Location No. 2 where it is unreeled into an oven 16to convert the printed foamable plastisol coating 12b into an embossed foam coating 12e. The web 12, on leaving the oven 16, is wound as pieces 17.

The adhesive 12d is formulated to be tolerant to the temperature encountered in the oven 16 and may typically be one of the "Collafix" range of adhesive marketed by Allied Colloids Limited.

1. Process for making prepasted chemically foamed wallcoverings comprising unreeling foamable base web, printing, reversing the printed web, prepasting with an adhesive capable of providing remoistenable features after tolerating heat conditions to be encountered during a subsequent foaming step, heating to perform said foaming step and piece wind.

2. A process as claimed in Claim 1 in which all but the heating and piece winding is conducted at one location and the heating and piece winding is conducted at a second location.

3. A process as claimed in Claim 2 in which the printing and prepasting is performed in a gravure or flexo printing machine.

4. A process as claimed in any preceding claim in which the adhesive is in the form of a water swellable polymer dispersed in an organic medium.

5. Apparatus for carrying out the first location process of Claim 2 comprising a multi-station gravure or flexo printing machine having up-line printing stations followed by web reversal means followed by a down line prepasting station.

6. Apparatus for carrying out the process of Claim 1 substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Wallcoverings The invention is concerned with the subject of prepasted wallcoverings and is aimed at providing apparatus and a process for making prepasted chemically foamed wallcoverings. A process already used for making prepasted foamed wallcovering involves conducting sub -processesatthree locations, namely: Location No. 1 Un-reel foamable web; print; re-reel and take to Location No. 2. Location No. 2 Un-reel printed foamable web; heat to foam; re-reel. Location No. 3 Un-reel printed foamable web; prepaste; piece wind. This already used process has potential problems points. For example, any damage occurring after printing (such as may arise in handling, transport and storage of reels) is damage to a product to which significant value, namely the printing, has been added. Any damage occurring after foaming involves loss of even greater value. Further a foamed web is soft or bulky and is susceptible to damage and is not suitable for conventional storage as a reel free-standing on a floor as the foam in proximity to the floor becomes crushed. Thus it is the practice to support reels of foamed web on centre supports mounted on blocks which is more troublesome than free-standing storage. The present invention provides an improved process which, whilst not removing all the problem points, at least reduces them. The new process is primarily a line process and hence avoids at least some of the re-reeling processes referred to above. In this way damage hazards such as may arise in handling, transport and storage of reeled products are reduced. The new process also retains the procedure of printing prior to prepasting and hence avoids risks from printability problems such as may arise due to: a) Adhesive inadvertently reaching the print surface; b) Disturbance to the printing surface due to an intermediate process impairing print; c) Inability to sustain register due to presence of prepaste on the reverse side of the web. The process according to the present invention is a process which requires at the most, two locations with one rewind between locations as follows: Location No. 1 Unreel foamable base web and print; reverse the printed web; prepaste with an adhesive capable of providing remoistenable features after tolerating heat conditions to be encountered during a subsequent foaming step (typically 180 - 220"C for 15 to 40 seconds) and re-reel. Location No. 2 Heat to foam and piece wind. (For reference purposes the early art processes of prepasting are seen in GB 588 554,605 438,606 648, 626290, 752,869 422. These processes have been generally replaced with a two-coat system disclosed in USP 3 122446 which, in turn, is likely to be replaced by prepasting with adhesives derived from inverse emulsions as disclosed in EP 0 008 213 and GB 2054 628A). It is preferred that both printing and prepasting is carried out by gravure orflexo processes. This becomes possible for example, in a multi-station machine with the last of the stations being used for prepasting after web reversal. One process according to the present invention, and apparatus for carrying out the process, will now be described with reference to the accompanying diagrammatic drawing. In the drawing a gravure printing machine 10 is shown with six printing stations 11a, llbetc. to 11 f. This machine (which effectively forms Location No. 1 of the above statement of invention) is supplied with a web 12 of substrate 12a, having afoamable plastisol coating 12b, from a reel 13. At stations 11 a, 1 1b b 11 . . . e, print 12c is applied. After the station 11e, the web 12 passes through a cross-roll reversing station 14 before entering station 11 fwhere an adhesive 1 2d in the form of a water swellable polymer dispersed in an organic medium is applied. This is subsequently dried and the web 12, now printed and pasted, is re-reeled on to a reel 15. The reel 15 is conveyed to Location No. 2 where it is unreeled into an oven 16to convert the printed foamable plastisol coating 12b into an embossed foam coating 12e. The web 12, on leaving the oven 16, is wound as pieces 17. The adhesive 12d is formulated to be tolerant to the temperature encountered in the oven 16 and may typically be one of the "Collafix" range of adhesive marketed by Allied Colloids Limited. CLAIMS

1. Process for making prepasted chemically foamed wallcoverings comprising unreeling foamable base web, printing, reversing the printed web, prepasting with an adhesive capable of providing remoistenable features after tolerating heat conditions to be encountered during a subsequent foaming step, heating to perform said foaming step and piece wind.

2. A process as claimed in Claim 1 in which all but the heating and piece winding is conducted at one location and the heating and piece winding is conducted at a second location.

3. A process as claimed in Claim 2 in which the printing and prepasting is performed in a gravure or flexo printing machine.

4. A process as claimed in any preceding claim in which the adhesive is in the form of a water swellable polymer dispersed in an organic medium.

5. Apparatus for carrying out the first location process of Claim 2 comprising a multi-station gravure or flexo printing machine having up-line printing stations followed by web reversal means followed by a down line prepasting station.

6. Apparatus for carrying out the process of Claim 1 substantially as hereinbefore described.