GB1580670A

GB1580670A - Printing-embossing sheets of plastic material

Info

Publication number: GB1580670A
Application number: GB3463177A
Authority: GB
Original assignee: HEBBELINCK M
Current assignee: HEBBELINCK M
Priority date: 1977-01-27
Filing date: 1977-08-18
Publication date: 1980-12-03
Also published as: NL7708367A; JPS5393906A; BE857416A; DE2736213A1; ES461140A1; FR2378637A1; IT1087156B; LU76649A1

Description

(54) IMPROVEMENTS IN AND RELATING TO PRINTING-EMBOSSING SHEETS OF PLASTIC MATERIAL (71) I, MARCEL HEBBELINCK, a citizen of Belgium, of 3 bis, rue du Moulin, B-1330 Rixensart, Belgium, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a process enabling thin sheets of plastic material to be printed and embossed in correct register with the said printing.

It also relates to a suitable installation for performing said process and to the products obtainable by the said process and installation.

For numerous purposes, products consisting of a thin sheet of plastic material have to undergo a printing and an embossing operation.

For the creation of particular visual effects it is generally desirable that printed ornamental elements be in correct register with relief elements obtained by the embossing of a thin sheet, which is generally made of an expanded plastic material.

Prior to the embossing, and particularly in the case of a plastic material having to be expanded or foamed beforehand, a gellified supported sheet is generally caused to pass through tunnel furnaces which are heated by the infra-red method or by hot air convection and in which the said plastic material undergoes a softening process and any possible additive contained therein causes it to expand. The still hot and possibly expanded material then passes between various rollers bearing a pattern in relief, which produces a corresponding pattern on the plastic material which has been softened and possibly expanded by the heat. The product is then cooled.

If a decoration has been printed onto the material beforehand, and in particular prior to the expansion, it is practically impossible, when it emerges from the tunnel furnace, to perform an embossing operation in register with the said imprint, i.e. an embossing constantly corresponding longitudinally with the existing imprint. The reason is that the material takes the form of a continuous film, essentially moved by traction and undergoes longitudinal deformations which vary in extent according to the driving traction exerted on it and the temperature to which it is subjected in the course of its passage through the tunnel furnace, said tractive stress and temperature being both liable to fluctuate in the course of production.

If expansible (foaming) products have to be embossed, the expansion installations of the tunnel type have to be constructed to a considerable length in order to ensure that the foam will be completely developed, which further aggravates the difficulties.

An object of the present invention is therefore to provide a process permitting to print and emboss thin sheets of plastic material wherein the imprint and the embossing are in correct register.

This purpose of the invention, is achieved with a process comprising the steps of: (1) Continuous printing on a continuous thin sheet of plastic material preferably applied to a support.

(2) Continuous passage of the printed sheet over and in contact with a part of a drum driven in rotation at a peripheral speed corresponding to the printing speed and heated to a sufficient temperature to render it deformable under the effect of an embossing operation.

(3) Embossing of the heated sheet synchronously with the printing, followed by cooling.

The thin sheet undergoing the treatment is a sheet of plastic material capable of deformation by heat, such as a polymeric plastic material, advantageously deposited as a coating on a support consisting of paper or textile or some other thin supporting substance or else a film of polymeric material e.g. polyvinyl containing conventional material expansion additives customarily employed for the expansion of sheets of polyvinyl material, prior to the embossing operation.

In the case of coated supports, whether or not expansible, the polymeric coating may be applied to the paper by the reverse roll coater, by means of a blade, by the calendering process or by the hot welding of a film onto a support of paper, textile or other thin material of which the purpose is to ensure the stability and the heat-resistance of the film during the decoration phase. This coating may or may not contain expansion agents, producing a foam during its passage through the high temperature zone, in order to increase the apparent thickness during the expansion phase and obtain relief effects which are pronounced to a greater or smaller extent as required.

With these agents it is also possible to combine accelerators or inhibitors, which may or may not be applied in accordance with a certain pattern.

It is found that under normal operating conditions, with the use of polymeric material containing expansion agents of the usual type, satisfactory expansion may be obtained without recourse to conventional tunnel furnaces. Needless to say, care must be taken to ensure that the traject completed on the drum by the material undergoing the treatment is sufficient to ensure complete expansion.

In one alternative method which is specially advantageous from the point of view of the nature and cost price of the resulting product, the located embossing stage of the invention consists of a relief printing operation, i.e. inked embossing, which enables embossing at one or more levels to be performed simultaneously with the printing. This provides a printed product of which the surface is at different levels.

With the process to which the invention relates the decoration, as well as any necessary expansion and also the embossing, which may be accompanied by inking, of products suitable for wall coverings, packing and upholstery, can be carried out in one single operation covering a very limited circuit.

It is based on a heating technique enabling the material to be pre-heated, jellified and expanded, the apparatus for the purpose being installed in a printing machine circuit which is no longer than that used for normal drying purposes between the ends of a conventional printing machine.

According to the invention, use is made of the temperature of the heating device for drying and/or jellifying the printing inks and at the same time expanding the basic plastic material and effecting the printing and embossing in one simultaneous operation, possibly by means of (cooled) printing rollers in relief, on a level with the heating device.

The aforementioned alternative method of operation, in which the located embossing stage consists of an inked embossing, offers the advantage that if the sheet undergoing the treatment is a single or composite sheet of expansible plastic material it is not necessary to provide a surface varnish on the resin to be expanded. This varnish, normally intended to support the imprint and form a firm "skin" for the expanded product, is replaced by zones of varnish of different colours, added by means of the printing rollers.

As the respective coloured zones are combined edge to edge, thus forming the design in question, the surface film is thus provided by the actual decoration.

The last roller or rollers, in penetrating the layer of plastic material which may or may not be expanded, adds the relief thereto at the same time as it provides the ornamental addition; this relief is then in register in respect of the first rollers, if there is no other embossing.

The drum is advantageously internally heated by means of a heating fluid at the temperature required for the softening and, if necessary, expansion of the material, by conduction via the support of the film of plastic material. If an expansible material undergoes this treatment a more amply expanded base is obtained, with a printed and embossed face forming a more compact "skin". The heating can also be effected by means of heating elements of the "radiant" type, preferably infra-red, positioned peripherally around the drum.

The rotary drum is preferably heated from the inside and preferably also through a double casing, by means of a heating fluid, up to a temperature of the order of 300"C. A further method adopted in a preferred version of the invention is to mount infra-red heating elements peripherably around the drum in order to obtain a temperature of 210-250"C in the surface of the sheet of material.

Under these conditions, satisfactory results are obtained with a heating time of the order of 10-15 seconds. For a drum of 1.5 m in diameter, speeds of the order of 15-25 m/min can be adopted, with a contact length of 3.5 m.

The sheet undergoing the treatment must be sufficiently thin to ensure that taking the nature of the sheet and the temperature of the drum into account the required embossing will be effected, together with any necessary expansion, to the required level. The operator can easily determine these various parameters in the light of his technical knowledge and by means of simple tests.

The following values may be indicated as a rough guide: Support consisting of paper 90-150 g/m2 textile 45-110 non-woven materials 45-110 PVC, expansible: 100 to 500 g/m2 Minimum temp.

of drum: 250"C In one particular advantageous method of operation, the heated drum is used as the counter-roller for the embossing roller or rollers. In this case the product thus undergoes an embossing operation, possibly accompanied by the application of ink, by one steel embossing roller or simultaneously by a number thereof, which are cooled, resting on the heated drum with the interposition of the treated sheet.

With one single installation, therefore, it is possible to carry out the printing, any necessary expansion of a plastic material, the embossing or printed embossing, the drying and the gellification of the inks, the ornamental elements being applied in register in respect of one another. It should be noted that the term register does not necessarily imply that the printed pattern and the embossed relief are superimposed on each other but simply that the repeated patterns of the design and of the relief are correctly located in respect of each other and if necessary offset in respect of each other by a constant distance.

The process to which the invention relates can be applied to the printing and embossing of PVC film of 50-500 gjm2 supported on paper, textile or any other thin substrate which will stand up for a limited period to the temperature involved.

The invention also relates to a suitable installation for the performance of the process to which the invention relates, the said installation consisting of (1) A printing machine comprising from one to six printing units; (2) A drum driven in rotation at a peripheral speed corresponding to the printing speed, heated with heating devices, having a minimum diameter of 1.5 m, and covered, over at least one half of its surface in the circumferential direction, by the continuous thin sheet of plastic material emerging from the printing machine; (3) At least one embossing roller which receives the material heated at the embossing temperature emerging from the drum, the or each embossing roller having the same outer diameter as that of the printing roller of the or each printing unit.

(4) Means for driving the printing machine and the embossing roller synchronously with each other.

The embossing roller may be a roller which performs a printing operation at the same time, thus making it possible to adopt the aforementioned alternative method of operation in which the printing is carried out in relief.

The printing machine is a conventional installation ih which heliographic, flexographic, offset or typographic printing is effected.

In particular, the printing may be effected by means of thinwalled typographic printing rollers made of chemically engraved steel or by any other process, either with flexographic blocks of elastomer material found to have sufficient resistance to the action of plasticizers or with a heliographic printing roller with a deep gravure of the order of 50 microns.

The embossing roller of metal is engraved by chemical action, milling or any other technique, to a depth preferably ranging from 0.2 to 1 mm, and comprises an intaglio or relief pattern corresponding to the design to be printed. This hollow roller is normally cooled by forced water cooling at a lower temperature, in such a way as to fix the embossed relief by an operation in which the deformable and preferably expanded product is locally compressed in accordance with the design but not necessarily superimposed thereon.

The embossing roller is positioned at a fixed distance (of the order of 0.1 - 0.2 mm) from the drum and compresses the expanded product, thus producing a relief in relation to the design and in accordance with the preselected pattern.

The last roller or rollers used in the particular method of operation for inked embossing will always be steel typographic rollers, the depth of the engraving determining that of the embossing; the walls of these rollers will be thin, only amounting to 3-4 mm including the engraving, in order to ensure satisfactory cooling by the circulation of a liquid coolant.

All the rollers used to form one and the same design will be constructed to the same diameter,. but the printing embossing roller or rollers may have a diameter representing an exact multiple of that of the normal printing rollers, repeating the design once or several times, in order to ensure a satisfactory cooling process.

The means for driving the printing roller and the other embossing rollers synchronously with one another may be of a mechanical type, as the printing roller and the embossing roller may be positioned in close proximity, since the heated drum to some extent serves as a return pulley for the sheet of plastic moving from the printing machine to the embossing rollers. Use may nevertheless be made of alternative synchronization devices, particularly of electronic devices.

The invention will be described in greater detail by reference to the attached drawings, representing schematic diagrams of installations by which the process of the invention can be carried out.

Figure 1 shows an installation enabling a simple embossing operation to be performed in register in relation to an imprint, in accordance with the invention.

Figure 2 shows an installation making it possible to adopt the particular method of operation described in the foregoing, comprising an inked embossing in register to an imprint and effected on the actual heated drum itself.

Similar elements or those performing a similar function have been given the same reference numbers in both drawings.

The installation shown in Figure 1 consists essentially of a conventional printing machine 1, a heated drum 2 and an embossing or graining installation 3.

The film of vinylic plastic 4 coming from an unwinding station 5 penetrates the printing machine 1 and then passes over the drum 2, which is internally heated by a heating fluid and externally heated by radiant heating elements 6 positioned on its periphery. This drum has a diameter of at least 1500 mm, and the film of plastic passes around the drum in such a way as to cover at least approximately one half of its surface and in some cases, depending on the diameter of the embossing rollers, more than two thirds of the circumference of the drum. Immediately after having left the heated drum the film of plastic undergoes a graining process in the installation 3, after which it circulates between the rollers 7 in order to undergo a cooling operation.

The diameter Dl of the rollers of the printing machine and the diameter D2 of the graining machine are equal, in addition to which a device 8 synchronizes the drive of the printing machine and that of the graining roller.

As the material is essentially supported over a major part of its traject by the heated drum, this traject itself being comparatively short, thanks to the use of a heated drum in conjunction with radiant heating elements, the sheet of plastic undergoes no appreciable deformation, particularly in the form of extension, in the course of its movement between the printing machine 1 and the graining or embossing installation 3, so that as a result of the synchronism ensured between these installations by the synchronization device 8 connected by lines of shafting (shown by broken lines in the drawing) to the driving mechanism of the printing machine 1 and of the embossing roller 3, it is possible to obtain an embossing or graining effect in the correct location or in register in relation to the printing already carried out.

On leaving the embossing installation 3 the sheet first passes through a cooling installation 7 and is finally wound onto a reel at 9.

The installation shown in Figure 2 consists of one or more printing columns 1, followed by the last printing embossing column 3, constituting the final unit.

The drying or jellification of the printing inks and also the heating or expansion of the resin of the film of plastic material 4 are effected on a drum 2 heated to a temperature of 250-300"C by means of thermal fluid. The unwinding station 5 feeds the machine with a support 4, coated in advance, this coating preferably comprising expansion products.

The column 1 comprises, for example, four printing devices (of the typographical, heliographic, flexographic or offset type) which by juxtaposition form the design and at the same time produce the film of surface varnish.

The printing and embossing column 3 includes the drum 2 heated to a temperature of 250-300"C and gellifying the printing inks deposited at 1, softening and/or expanding the resin with which the support has been coated in advance. This drum may be provided, over part of its circumference, with heating elements 6 acting on the radiation principle, making it possible to increase the speed at which the material passes through the apparatus in order to obtain the required effect. This cylinder, having a minimum diameter of one metre, will be hot-rectified. Furthermore, the embossing and printing column comprises typographical printing heads 31 and 32, with thin walls, subjected to a cooling process, their depth creating the relief effect while the inking of the peaks creates the imprint in the valley.

In the design shown the engraving depth of the roller 32 will be greater than that of the roller 31, in order to enable two different embossing levels and two different imprints to be obtained.

The embossing depth will be regulated by the extent to which the printing rollers are caused to approach the heated drum 2. The minimum distance of approach, however, must never be less than that of a support on which the coating has been provided when the sheet 4 consists of a coated film. The driving mechanisms for the columns 1 and 3 are interconnected by a synchronization device 8 and each comprises a device for angular rotation in respect of the main drive, enabling the design to be correctly positioned. The line of shafting 8' renders all the printing and embossing heads operationally integral with one another.

The sheet 4 to be printed moves at the same speed as the circumferential speed of the printing rollers, this movement being controlled by the ingoing and outgoing driving devices 15 and 16, controlled by the line of shafting 8'. On leaving the printing section the product is set and cooled by the rollers 17 and 18, fed with a liquid coolant. The finished product will then be wound onto 9 and is ready for conditioning.

The following example serves to illustrate the invention, which is nevertheless not limited thereto.

Example The following are formulae for coating resin, one for the foaming and the other for the non-foaming type, and may serve as a basis for the embossing operation: Foaming composition Non-foaming composition Plasticizers 38% Plasticizers 27% Stabilizing agent 1,3% Stabilizers 1,4% Cd Zn "Kicker" Foam regulator 0,9% Azodicarbonamide I to 2% Charges + pigments 13bio Charges + TiO2 20% PVC resin 43,5/o PVC resin 46% Diluting medium 5% Diluting medium 5% According to the relief and thickness desired the coating is produced to a thickness ranging from 0.05 mm to 0.8 mm on a support ranging from 0.1 to 0.5 mm in thickness. This coating may be produced by the conventional processes, and its jellification will be effected at a temperature lower than the decomposition point of the azodicarbonamide.

The printing ink consists of the same elements as the basic coating, in order to enable them to adhere thereto under the effect of the heat welding process.

Nevertheless. in order to obviate the premature jellification, which would cause undue thickening in the contents of the ink vessels, the plasticizer of the normal solvating capacity used in the coating will be replaced by a mixture of plasticizers of low solvating capacity and providing a low and constant viscosity.

Bv way of an example, the average proportions for the constituents of the printing inks are as follows: Plasticizer of low solvating capacity 40 Stabilizing agent 2 Anti-UV agent 0.5 Pigments (resistant to temperature.

light and migration) 13 PVC resin 44.5 WHAT I CLAIM IS: 1. A process for the printing and embossing in correct register of thin sheets comprising the steps of: (l) Continuous printing on a continuous thin sheet of plastic material preferably applied to a support.

(3) Embossing of the heated sheet synchronously with the printing. followed by cooling.

2. A process in accordance with Claim 1. wherein the thin sheet undergoing the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. obtained. The embossing depth will be regulated by the extent to which the printing rollers are caused to approach the heated drum 2. The minimum distance of approach, however, must never be less than that of a support on which the coating has been provided when the sheet 4 consists of a coated film. The driving mechanisms for the columns 1 and 3 are interconnected by a synchronization device 8 and each comprises a device for angular rotation in respect of the main drive, enabling the design to be correctly positioned. The line of shafting 8' renders all the printing and embossing heads operationally integral with one another. The sheet 4 to be printed moves at the same speed as the circumferential speed of the printing rollers, this movement being controlled by the ingoing and outgoing driving devices 15 and 16, controlled by the line of shafting 8'. On leaving the printing section the product is set and cooled by the rollers 17 and 18, fed with a liquid coolant. The finished product will then be wound onto 9 and is ready for conditioning. The following example serves to illustrate the invention, which is nevertheless not limited thereto. Example The following are formulae for coating resin, one for the foaming and the other for the non-foaming type, and may serve as a basis for the embossing operation: Foaming composition Non-foaming composition Plasticizers 38% Plasticizers 27% Stabilizing agent 1,3% Stabilizers 1,4% Cd Zn "Kicker" Foam regulator 0,9% Azodicarbonamide I to 2% Charges + pigments 13bio Charges + TiO2 20% PVC resin 43,5/o PVC resin 46% Diluting medium 5% Diluting medium 5% According to the relief and thickness desired the coating is produced to a thickness ranging from 0.05 mm to 0.8 mm on a support ranging from 0.1 to 0.5 mm in thickness. This coating may be produced by the conventional processes, and its jellification will be effected at a temperature lower than the decomposition point of the azodicarbonamide. The printing ink consists of the same elements as the basic coating, in order to enable them to adhere thereto under the effect of the heat welding process. Nevertheless. in order to obviate the premature jellification, which would cause undue thickening in the contents of the ink vessels, the plasticizer of the normal solvating capacity used in the coating will be replaced by a mixture of plasticizers of low solvating capacity and providing a low and constant viscosity. Bv way of an example, the average proportions for the constituents of the printing inks are as follows: Plasticizer of low solvating capacity 40 Stabilizing agent 2 Anti-UV agent 0.5 Pigments (resistant to temperature. light and migration) 13 PVC resin 44.5 WHAT I CLAIM IS:

1. A process for the printing and embossing in correct register of thin sheets comprising the steps of: (l) Continuous printing on a continuous thin sheet of plastic material preferably applied to a support.

2. A process in accordance with Claim 1. wherein the thin sheet undergoing the

treatment.consists of a continuous thin sheet of plastic material capable of deformation by heat.

3. A process in accordance with Claim 1, wherein the thin sheet undergoing the treatment consists of a continuous thin sheet of plastic material capable of undergoing deformation by heat and deposited as a coating on a support consisting of paper or textile or a thin supporting material.

4. A process in accordance with Claim 2 or 3, wherein the film of plastic material contains conventional expansion additives customarily employed for the expansion of sheets of polyvinyl material, prior to the embossing operation.

5. A process in accordance with Claim 4, wherein the expansion additives are combined with accelerators or inhibitors, possibly applied in accordance with a certain pattern

6. A process in accordance with anyone of Claims 1 to 5, wherein the located embossing step consists of a relief printing operation performed by means of an inked embossing.

7. A process in accordance with any one of Claims 1 to 6, wherein a varnish intended to create a firm "skin" on the expanded product consists of zones of varnish of different colours, added by means of the printing rollers, the coloured zones being combined with their edges touching and forming the design, the surface film being thus produced by the decoration itself.

8. A process in accordance with any one of Claim 1 to 7, wherein the heating of the drum is performed internally by means of a heating fluid at temperature required for the for the softening and, if necessary, expansion of the material, by means of conduction via the support of the film of plastic material.

9. A process in accordance with Claim 8, wherein the drum is heated internally by a double casing to a temperature of the order of 300"C.

10. A process in accordance with Claim 8 or 9, wherein the heating is effected additionally by radiant heating elements, preferably of the infra-red type, positioned peripherally around the drum.

11. A process in accordance with Claim 10, wherein the radiant heating elements raise the surface temperature of the sheet to 210-250"C.

12. A process in accordance with any one of Claim 1 to 11, wherein the heated drum is used as a counter cylinder for at least one embossing roller.

13. A process in accordance with any one of claims 1 to 12 wherein the product undergoing printing and embossing consists of a PVC film weighing 50 to 500 g/m2, supported on paper, textile or any other thin substrate which will stand up, during a limited period, to the temperature involved.

14. An installation suitable for the performance of the process covered by any one of Claims 1 to 13, said installation consisting of: (1) A printing machine comprising from one to six printing units; (2) A drum driven in rotation at a peripheral speed corresponding to the printing speed, heated with heating devices, having a minimum diameter of 1.5 m and covered, over at least one half of its surface in the circumferential direction, by the continuous thin sheet of plastic material emerging from the printing machine; (3) At least one embossing roller which receives the material heated at the embossing temperature emerging from the drum, the or each embossing roller having the same outer diameter as that of the printing roller of the or each printing unit; (4) Means for driving the printing machine and the embossing roller synchronously with each other.

15. An installation in accordance with Claim 14, wherein the printing machine is of the conventional type using the heliographic, flexographic, offset or typographic printing process.

16. An installation in accordance with Claim 15, wherein the fact that the printing is effected by means of thin-walled typographic printing rollers made of engraved steel, either with flexographic printing blocks of an elastomer material resistant to the action of plasticizing agents, or with a heliographic roller with a deep gravure of the order of 50 microns.

17. An installation in accordance with any one of Claims 14 to 16, wherein the embossing roller consists of a metal roller engraved to a depth varying from 0.2 to 1 mm for preference, comprising an intaglio or relief pattern which corresponds to the design to be printed, this roller being normally cooled by forced water circulation at a low temperature, in such a way as to enable the relief pattern obtained in the embossing process to be fixed by local compression in the correct location or in register, in accordance with the design of the deformable and preferably expanded product.

18. An installation in accordance with Claim 17, wherein the embossing roller is situated at a fixed distance of the order of 0.1 to 0.2 mm from the drum and compresses the expanded product.

19. An installation in accordance with any one of Claims 14 to 18, wherein the embossing roller consists of a typographic roller of engraved steel, which at the same time effects a printing operation, the depth of the gravure in the said roller determining the embossing depth, the thickness of its wall being of the order of 3 to 4 mm, including the gravure.

20. An installation in accordance with any one of Claims 14 to 19, wherein the printing or embossing rollers have the same diameter or a diameter which is an exact multiple of a reference diameter.

21. An installation in accordance with Claim 20, wherein the embossing rollers have a diameter which is an exact multiple of that of the printing rollers repeating the design once or several times, in order to ensure a satisfactory cooling process.

22. An installation in accordance with any one of Claims 14 to 21, wherein the means for driving the printing machine and the other embossing rollers are of the mechanical type, the printing machine and the embossing roller being situated in close proximity to each other.

23. An installation in accordance with any one of Claims 14 to 21, wherein the means for driving the printing machine and the other embossing rollers consist of an electronically controlled device.

24. A process for the printing and embossing in correct register of thin sheets substantially as herein before described with reference to the accompanying example.

25. An installation substantially as herein before described with reference to and as shown in the accompanying drawings.