EP2692538B1 - Underlay film for a metal printing blanket - Google Patents

Description

The present invention relates to a backing sheet for a metal blanket, a metal blanket and the use of the backing sheet.

Offset printing presses consist of a system of solid cylinders, which provide for a pinpoint transfer of the print image from the printing plate on a rubber blanket cylinder on the substrate and must have an extremely high degree of accuracy. The latter is also required by the consumables used on these cylinders. Smallest inaccuracies can quickly lead to an imbalance at very high speeds or lead to faster wear over the height of several million settlements against each other.

In order to reduce the imbalance of a blanket cylinder to a minimum, blanket plates have been developed, which guarantee the blanket surface maximum rest and in which the blanket plates are introduced by means of folding in a very narrow clamping range. Unlike printing presses with conventional blankets, no protective underlay films can be glued to the cylinder during this process. The protective films have so far usually consisted of a polyester film with thermal bonding. The films are first cut to size and then applied with the introduction of high temperatures. In the process, the films shrink, change their thickness spectrum and can not ensure complete underlaying of the blanket plate. Larger films can not be used as they would not fit between the base surface defined by the fold of the two clamping straps.

Incomplete substructures or differences in thickness may cause the settlement to occasionally cause disturbances that cause vibrations. The cut edges of the hard polyester are partly brittle and sharp. They help to ensure that the blanket plates do not lie completely flat on the cylinder, which can provide another reason for an imbalance.

In WO 2009/007894 For example, a heat-sealable film is described which is laminated to the metal side of the metal blanket by heat and pressure. Such heat-sealable film composites, which are usually made of polyester and a thermoplastic polyurethane, have high heat shrinkage values. Laminates consisting of a polyethylene terephthalate film (PET) and a thermoplastic polyurethane film (TPU) were tempered at 130 ° C. for 30 minutes and shrinkage values of 1.0 to 1.8% were found. These are unacceptable values when it comes to providing dimensionally stable film composites.

EP 2 070 717 describes a blanket for a blanket for offset printing comprising at least one foamed layer.

EP 2 106 925 discloses a backing sheet for offset printing comprising at least one self-adherent polymer film.

D4 US 4,699,841 discloses flexible multilayer polyimide laminates.

JP A 52-135386 describes a laminated material that serves as a meat wrapper.

Also known are films which are adhesively bonded, for example with a PSA adhesive (Pressure Sensitive Adhesive). These mostly made of PET films can be easily glued to the underside of metal blankets. However, they are not dimensionally stable in the same way and show high shrinkage values of 0.8 to 1.8%. In this case, the disadvantage is known that on the one hand PSA adhesive are not resistant enough to solvents and cleaning fluids that are used in the printing industry, on the other they quickly lose the adhesion at temperatures of 50 ° C and higher temperatures, as they do not are more shear stable.

The heat-sealable thermoplastic material must adhere well to the carrier layer and must not tear, shed or infiltrated with water or solvents throughout the life of the blanket. For the perfect blanket, a heat-sealable film laminate is desired, which has a shrinkage of 0% if possible and in which the layers are virtually inseparably connected.

The object of the present invention is to provide a backing film which overcomes at least some of the disadvantages of the prior art.

It has surprisingly been found that it is possible to provide backing sheets which combine particularly dimensionally stable backing layers with a heat-sealable polymer. In particular, the dimensionally stable carrier layer contributes significantly to increasing the quality of the backing film. In particular, a layer whose shrinkage in TD (transverse direction), ie transversely to the running direction and in MD (machine direction), ie in the direction of the running direction of the film web, measured at 130 ° C. for 30 minutes does not have a dimensional stability of 0.5% exceeds. For this purpose, the film is measured, the temperature for 30 min at 130 ° C, cooled again to room temperature and measured the width and length changes. At a width of 100 cm, the width after treatment must be at least 99.5 cm. The same very small shrinkage change is also observed in the thickness of the film; however, this is more difficult to measure due to the smaller thickness.

In a preferred embodiment, the scale support layer is selected from aluminum or polyamide.

As a heat-sealable polymer is suitable polyurethane.

FIG. 1 shows a laminate according to the invention, in which a thermoplastic polyurethane is bonded to an aluminum layer.

This laminate after FIG. 1 For example, it is bonded to the underside of a metal blanket at 120 ° C and pressures of 5 to 10 bar. Here, the TPU serves as an adhesive, such that it develops heat-sealable properties under heat and adheres to the surface of the metal blanket due to its lowered viscosity. After cooling, a virtually inseparable composite has formed.

FIG. 2 shows a laminate consisting of polyamide film and thermoplastic polyurethane. The polyamide film is the carrier.

As described above, this laminate is also attached to a metal blanket under heat and pressure.

A laminate according to FIG. 1 shows a measured shrinkage of 0%. A laminate after FIG. 2 shows a shrinkage of less than 0.5% under the same conditions.

Foil laminates as per FIG. 1 and FIG. 2 serve very well to provide dimensionally stable film composites that ensure a complete under construction of the blanket plate even after thermal application. A shrinkage of less than 0.5% can still be accepted when it comes to ensuring only the smallest differences in thickness in the resulting composite with the metal blanket.

The laminates of aluminum and TPU or polyamide and TPU are easy to cut. It creates clean edges and no brittle edge breaks as in the use of polyester.

Furthermore, the provided film composites are stable against temperatures of 130 ° C and influences of solvents and cleaners used in the printing process.

With regard to the bonding properties, however, composites made of aluminum foil and TPU or polyamide and TPU show the highest bond adhesion values. With regard to ease of processing, adhesion to the substrate and chemical resistance to water, solvents and cleaning solutions, the TPU is preferred.

The carrier film can be laminated with other film layers that provide functionality. For example, PET can be used to install a protective layer between the metal blanket and aluminum of the heat-sealable film and the steel cylinder of the press. Furthermore, the thickness of the film composite can be increased and precisely adjusted via the PET layer.

In this case, in the heat of hot lamination, the PET may tend to have a higher shrinkage, but it is kept in shape by the low-shrinkage layer such as aluminum or polyamide.

A foam may also be laminated to the backing layer to make the entire composite more elastic and more compressible. For example, vibrations that are omnipresent in the press can be better absorbed and a cleaner and more precise print image is achieved.

In addition, film composites can be formed, which form a combination of two beneficial properties, ie a PET layer to increase the thickness and a foam layer that ensures compressible properties.

FIG. 3 shows a laminate consisting of aluminum foil and TPU. The aluminum foil forms the carrier of the film laminate. On the underside of the aluminum, a layer of PET was attached, which forms a protective layer and increases the thickness of the composite and thus the desired total thickness can be easily adjusted.

FIG. 4 shows a laminate consisting of polyamide film and TPU. The polyamide film forms the carrier of the film laminate. To the polyamide A layer of PET was attached on the underside to serve as a protective layer.

FIG. 5 shows a laminate consisting of polyamide film and TPU. The polyamide film forms the carrier of the film laminate. A layer of foam was attached to the polyamide on the underside, which increases the compressibility of the composite.

FIG. 6 shows a laminate consisting of aluminum foil and TPU. The aluminum foil forms the carrier of the film laminate. A layer of PET was attached to the underside of the aluminum, including foam. This makes it possible to adjust the thickness and the compressibility of the composite.

In order to adjust the thickness of the film laminate or provide a suitable substructure for the carrier layer, other polymeric materials may be used besides PET, for example polyurethane, polyethylene, polypropylene, polyvinyl chloride, polyacrylates such as polymethyl methacrylate, polystyrene, polytetrafluoroethylene, polyamides, other polyesters, polyglycols, Silicones, biopolymers, synthetically produced biodegradable polymers, or mixtures thereof; and chemically-linked combinations such as copolymers. is selected. Furthermore, metals or fabrics are also suitable.

Suitable materials for compressible, foamed layers are, in particular, polyurethanes, polyethylenes and polypropylenes, polystyrene, nitrile-butyl rubber, neoprenes, ethylene-propylene-diene rubber and silicones or mixtures of these materials.

The invention also provides a metal printing blanket comprising a metal layer, on top of which there is a printing layer, wherein on the underside of the metal layer of a backing film according to the invention is present.

1. a) Bereitstellen eines Metallrückendrucktuchs
2. b) Heißsiegelung einer erfindungsgemäßen Unterlagenfolie.

Another object of the invention is a method for assembling a Metallrückendruckuchsuchs comprising the steps:

1. a) Providing a Metallrückenduchsuchs
2. b) heat sealing a backing sheet according to the invention.

Another object is the use of a backing sheet according to the invention as a support for a metal blanket.

The invention is explained in more detail by the following example.

Example 1:

A 50 .mu.m thick aluminum foil is bonded with a thermoplastic polyurethane film of 100 .mu.m thickness with Herberts EPS 7146®, a laminating adhesive from Bostik. The thickness of the adhesive layer is 10 microns, the thickness of the overall composite is about 160 microns.

The shrinkage measurement over 30 min at 130 ° C gives no measurable shrinkage in TD and MD, ie 0%.

Example 2:

A 100 μm thick polyamide film is bonded to Herbert's EPS 7146® with a 70 μm thermoplastic polyurethane film. The thickness of the adhesive layer is 8 microns, the thickness of the overall composite is about 178 microns.

The shrinkage measurement over 30 min at 130 ° C gives 0% in TD and 0.4% in MD as shrinkage value.

Claims (8)

1. An underlay film for a metal printing blanket, comprising at least one dimensionally stable supporting layer, and a heat sealable polymer, wherein said dimensionally stable supporting layer is selected from aluminum or polyamide, wherein said heat sealable polymer adheres to said supporting layer, and said heat sealable polymer is a polyurethane.
2. The underlay film according to claim 1, characterized in that said heat sealable polymer is a cross-linking polyurethane.
3. The underlay film according to either of claims 1 or 2, characterized in that a polyester layer is additionally present in contact with said dimensionally stable supporting layer.
4. The underlay film according to either of claims 1 or 2, characterized in that a layer of an open-cell or closed-cell polymeric foam is additionally bonded in contact with said dimensionally stable supporting layer.
5. The underlay film according to either of claims 1 or 2, characterized in that a polyester layer bonded to a layer of an open-cell or closed-cell polymeric foam is present in contact with said dimensionally stable supporting layer.
6. A metal printing blanket comprising a metal layer provided with a printing layer on the surface thereof, wherein an underlay film according to any of claims 1 to 5 is present on the bottom side of said metal layer.
7. A process for mounting a metal-backed printing blanket, comprising the steps of:

   a) providing a metal-backed printing blanket;

   b) heat sealing an underlay film according to any of claims 1 to 5.
8. Use of an underlay film according to any of claims 1 to 5 as an underlay for a metal printing blanket.

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