PROCESS FOR PREPARING ROLLS FOR USE IN COATING PLANTS, AND ADHESIVE TAPE FOR PREPARING ROLLS

Abstract

Rolls for use in coating plants and processes for preparing said rolls is disclosed. The rolls and processes comprise at least: a) providing a coating plant with a roll having a lateral face intended for contact with a substrate to be coated; b) producing or providing an adhesive tape comprising i) a carrier layer consisting at least partly of ethylene-tetrafluoroethylene copolymer, and ii) an adhesive layer disposed on the carrier layer and consisting at least partly of a silicone adhesive; and c) adhering the adhesive tape to the lateral face of the roll by means of the adhesive layer to give or provide a prepared roll.

Claims

1. A process for preparing rolls for use in coating plants, the process comprising: a) providing a coating plant with a roll having a lateral face configured for contact with a substrate to be coated; b) producing or providing an adhesive tape comprising i) a carrier layer consisting at least partly of ethylene-tetrafluoroethylene copolymer, and ii) an adhesive layer disposed on the carrier layer and consisting at least partly of a silicone adhesive; and c) adhering the adhesive tape to the lateral face of the roll by means of the adhesive layer to give or provide a prepared roll, wherein the adhering takes place such that the lateral face of the prepared roll is covered at least partly by the adhesive tape.

2. The process of claim 1, wherein the adhesive tape is a pressure-sensitive adhesive tape.

3. The process of claim 1, wherein the carrier layer has a mean thickness in the range from 20 to 200 μm.

4. The process of claim 2, wherein the carrier layer is a multi-ply carrier layer comprising two or more sub-plies, wherein at least one sub-ply consists of at least partly of ethylene-tetrafluoroethylene copolymer.

5. The process of claim 4, wherein the carrier layer, additionally to the ethylene-tetrafluoroethylene copolymer, comprises one or more fluoropolymers selected from the group consisting of PTFE (polytetrafluoroethylene), FEP (poly(tetrafluoroethylene-co-hexafluoropropylene)), PVF (polyvinyl fluoride), PCT FE (polychlorotrifluoroethylene), ECTFE (poly(ethylene-co-chlorotrifluoroethylene)), PVDF (poly(1,1-difluoroethene)) and PFA (perfluoroalkoxy polymers).

6. A process for coating a perforate substrate with a coating plant, the process comprising: c) preparing rolls according to claim 1; d) contacting a substrate to be coated with the lateral face of the prepared roll, the substrate to be coated having one or more continuous clearances; and e) applying a coating material to that side of the substrate to be coated that is facing away from the prepared roll, wherein the contacting of the substrate to be coated with the lateral face of the prepared roll takes place such that the one or the two or more continuous clearances lie at least partly above a region, covered by the adhesive tape of the lateral face of the prepared roll, so that contact between the lateral face and the coating material is at least partly prevented by the adhesive tape in the region of the one or of the two or more continuous clearances.

7. An adhesive tape for preparing rolls for use in the process of claim 6, the adhesive tape comprising: i) a carrier layer consisting at least partly of ethylene-tetrafluoroethylene copolymer; ii) an adhesive layer disposed on the carrier layer and consisting at least partly of a silicone adhesive, and iii) a release material disposed on the adhesive layer.

8. A method comprising: adhering the adhesive tape of claim 7 to a lateral face of the roll for the purpose of increasing the service life of the roll and/or for prolonging maintenance intervals.

9. A prepared roll produced by the process of claim 1, the prepared roll having a lateral face configured for contact with a substrate to be coated, wherein the lateral face of the prepared roll is covered at least partly by an adhesive tape, and the adhesive tape comprises: i) a carrier layer consisting at least partly of ethylene-tetrafluoroethylene copolymer, and ii) an adhesive layer disposed on the carrier layer and consisting at least partly of a silicone adhesive.

10. A coating plant for coating substrates in the process of claim 6, the coating plant comprising: one or more rolls configured to guide and/or to process a substrate to be coated, wherein at least one roll is a prepared roll; and a coating unit configured to apply a coating material to the side facing away from the prepared roll of a substrate to be coated that has been contacted by the prepared roll.

Description

[0099] Below, preferred embodiments of the invention are elucidated in more detail and described with reference to the appended figures, in which:

[0100] FIG. 1 shows a schematic representation of an illustrative roll and of an adhesive tape of the invention for use in a process of the invention for obtaining a prepared roll of the invention;

[0101] FIG. 2 shows a schematic representation of a coating plant of the invention in one preferred embodiment, in a first view;

[0102] FIG. 3 shows a schematic representation of a coating plant of the invention in a second preferred embodiment; and

[0103] FIG. 4 shows a schematic representation of a part of the coating plant of the invention from FIG. 2, in a second view.

[0104] FIG. 1 shows schematically an illustrative roll 10 of a coating plant and an adhesive tape 18 of the invention in one preferred embodiment for use in a process of the invention for obtaining a prepared roll 24.

[0105] In the example shown, the roll 10 is formed of chromed steel and possesses a rubber coating on the lateral face 16. The roll 10 in the example shown has a diameter of 600 mm.

[0106] The adhesive tape 18 is adhesive on one side and comprises, one atop another, a carrier layer 20, an adhesive layer 22 and a release material 28. In the example shown, the release material 28 consists of PET and is coated on both sides with a fluorosilicone release layer. In the course of the process of the invention, the release material 28 is removed, for the adhesive tape 18 to be stuck by the adhesive layer 22 to the roll 10. Correspondingly, the thickness of the adhesive tape 18 after adhering is defined substantially by the thicknesses of the carrier layer 20 and of the adhesive layer 22, which in the example shown are 70 μm and up to 25 μm, respectively.

[0107] In the example of FIG. 1, the carrier layer 20 consists entirely of ethylene-tetrafluoroethylene copolymer, has a bluish colouration, and has been produced by flat film extrusion. The adhesive layer 22 consists entirely of a chemically crosslinked pressure-sensitive silicone adhesive which comprises a condensation-crosslinked silicone, the pressure-sensitive silicone adhesive having a surface weight in the region of about 25 g/m.sup.2. On the surface of the roll 10, the adhesive tape 18 of the invention has a peel adhesion of more than 2.5 N/cm, this being particularly preferred for the planned usage.

[0108] To obtain an adhesive tape 18 of the invention of this kind, the surface of the carrier layer 20, prior to the application of the pressure-sensitive silicone adhesive, is activated by means of corona treatment at a temperature of not more than 300° C. The pressure-sensitive silicone adhesive can then be applied to the activated surface of the carrier layer 20. The adhesive layer 22 is shaped from the silicone adhesive by means of a comma bar.

[0109] In the process of the invention, as indicated by the arrow in FIG. 1, the adhesive tape 18 is mounted by the adhesive layer 22 on the roll 10 in such a way that the surface of the prepared roll 24, resulting from the joining of adhesive tape 18 and roll 10, is formed by the carrier layer 20 at the corresponding position over the entire circumference.

[0110] FIGS. 2 and 3 show preferred embodiments of a coating plant 12 of the invention for the coating of substrates 14 in the context of the implementation of a coating process of the invention, in preferred embodiments. The respective coating plant 12 of the invention comprises for this purpose a plurality of rolls for guiding and/or processing the substrate 14 to be coated.

[0111] The coating plant 12 of the invention is designed in each case as a plant for extrusion coating and comprises, accordingly, a coating unit 30, disposed above the roll arrangement, this unit 30 in the example shown being an extruder. The extruder is configured to distribute the coating material, polyethylene for example, in the form of a hot polymer melt in a relatively uniform way over the substrate 14, allowing this substrate to be shaped by the roll arrangement in which the larger, central roll is a water-cooled steel roll which also promotes the solidification of the polymer layer. In order to prevent damage to the roll arrangement by the hot polymer melt, the coating plant of the invention comprises a roll 24 prepared in accordance with the invention. FIG. 2 additionally shows, in a marginal region of the roll arrangement, a belt guided over the entire roll arrangement, which serves to protect the rolls in the side regions. A belt of this kind can be produced, for example, if two adhesive tapes 18 of the invention are joined via the adhesive layers 22 and joined to form a continuous belt, in which the carrier layers 20 of ETFE are on the outside. This belt is not represented in FIG. 3, in order to improve the visibility of the bonded covering with the adhesive tape.

[0112] In the example shown, the substrate 14 is a beverage carton, i.e., a semi-finished carton product of the kind used, for example, in the production of milk packaging. Such beverage cartons in the folded state, as the outlet aperture, have a clearance 26, which may already be present when the starting material is coated.

[0113] FIG. 4 shows a detail of a coating plant 12, which in terms of the fundamental arrangement is comparable with the structure of FIG. 2; in this detail, the view is a perpendicular one onto the lateral face 16 of the prepared roll 24, and corresponding belts are provided in both side regions, these belts being indicated in each case at the margins of the prepared roll 24.

[0114] As can be seen in FIG. 4, a multiplicity of clearances 26 are spaced equidistantly apart from one another along the direction of passage of the substrate 14 through the coating plant 12, and, in the representation shown, they are also arranged in two rows in the substrate 14, with the rows being spaced apart along the longitudinal direction of the prepared roll 24. In order to take account of this circumstance, the lateral face 16 is wrapped with the adhesive tape 18 over the entire circumference at the two sections corresponding to the positions of the clearances and spaced apart along the longitudinal direction of the roll 24.

[0115] In a process of the invention for coating the substrate 14 with the coating plant 12 of the invention, the substrate 14 to be coated is first disposed on the lateral face 16 of the prepared roll 24. The coating unit 30 then brings the coating material, in the form of a polymer melt, onto that side of the substrate 14, contacted from below, that is facing away from the prepared roll 24. The disposition of the substrate 14 on the prepared roll 24 in this case is such that the clearances 26 lie completely above that region of the lateral face 16 of the prepared roll 24 that is covered with the adhesive tape 18, so substantially completely preventing contact between the lateral face 16 and the coating material in the region of the clearances 26 by means of the adhesive tape 18.

[0116] Below, preferred embodiments of the invention are elucidated further and described with reference to experiments.

[0117] A. Sample Production

[0118] As adhesive, a pressure-sensitive silicone adhesive is produced from products available commercially. Production took place from a mixture of vinyl-PDMS, MQ resin and silane crosslinker (trade name DOWSIL 7657 from Dow Chemical) using a platinum crosslinker (0.5% trade name SYL-OFF 4000 from Dow Chemical).

[0119] The pressure-sensitive silicone adhesive was applied from solvent, with the pressure-sensitive silicone adhesive being crosslinked after the drying or evaporation of the solvent at elevated temperatures of about 180° C.

[0120] The release material used was a PET liner provided on one side with a fluorosilicone release layer (trade name SILFLU S 50 M 1 R88002 WHITE from Siliconature S.p.a.)

[0121] To produce the adhesive tape E1 of the invention, the pressure-sensitive silicone adhesive produced was applied by comma bar coating with a surface weight of 25 g/m.sup.2 to a blue-coloured ETFE film whose surface immediately prior to the application of the PSA was activated by corona treatment. The ETFE film has a substantially constant thickness of 50 μm (weight around 89 g/m.sup.2) and a production width of 1300 mm. After the drying of the assembly, the release material was applied to the adhesive layer. The resultant adhesive tape E1 had a total thickness (without release material) of about 72 μm.

[0122] To produce the adhesive tape E2 of the invention, the pressure-sensitive silicone adhesive produced was applied by comma bar coating with a surface weight of 33 g/m.sup.2 to a transparent ETFE film whose surface immediately prior to the application of the PSA was activated by corona treatment. The ETFE film has a substantially constant thickness of 80 μm (weight around 142 g/m.sup.2) and a production width of 500 mm. After the drying of the assembly, the release material was applied to the adhesive layer. The resultant adhesive tape E2 had a total thickness (without release material) of about 112 μm.

[0123] Employed as comparative sample V1 was a PTFE-based commercial product from tesa, which is available commercially as “tesa 4820”. The pressure-sensitive silicone adhesive processed in this product is the same as in adhesive tapes E1 and E2, with the resultant adhesive layer applied on a PTFE film with a thickness of about 75 μm (weight around 153 g/m.sup.2) that has been activated, in a manner typical for PTFE, by an etching operation with sodium naphthalide. The surface weight of the applied adhesive is about 25 g/m.sup.2. The adhesive tape V1 had a total thickness (without release material) of about 100 μm.

[0124] Employed as comparative sample V2 was a PTFE-based commercial product from Nitto, which is available commercially as “NITOFLON Nr. 923S”. A pressure-sensitive silicone adhesive is processed in this product, with the adhesive layer being applied at a coatweight of about 50 g/m.sup.2 to a PTFE film having a thickness of about 50 μm (weight around 134 g/m.sup.2) The adhesive tape V2 had a total thickness (without release material) of about 104 μm.

[0125] B. Experiments

[0126] B1. Technical Adhesive Properties

[0127] For the samples V1, V2, E1 and E2, determinations were made, as described below, of the peel adhesion on steel, the anchoring strength by measurement against etched PET film, and the micro-shear travel under temperature load.

[0128] The peel adhesions on steel were determined in analogy to ISO 29862 (Method 3) at 23° C. and 50% relative humidity with a removal velocity of 300 mm/min and a removal angle of 180°. The substrates used were steel plates in accordance with the standard. The measurement strip of the respective adhesive tapes was bonded by means of a roller application machine at 4 kg and a temperature of 23° C. The adhesive tapes were removed immediately after application. The measurement value (in N/cm) was obtained as the mean value from three individual measurements.

[0129] To determine the anchoring of the PSA on the carrier, a T-peel test was carried out as is described in WO 2017140775 A1. For this test, the adhesive tape was laminated onto the chemically etched surface of a PET film. Removal took place using a T-peel machine which is set to a constant rate and which measures the force needed for the maintenance of this constant rate. The measurement value (in N/cm) was obtained as the mean value from three individual measurements.

[0130] The shear strength under temperature load was determined by means of a micro-shear test. For this purpose, a sample specimen (length around 50 mm, width 10 mm) cut from the respective adhesive tape was bonded to a steel test plate which had been cleaned with acetone, with the steel plate projecting beyond the adhesive tape to the right and the left and with the adhesive tape protruding beyond the test plate at the upper margin by 2 mm. The bond area of the sample was 13 mm×10 mm (height×width). The bond side was then rolled over three times using a 2 kg steel roller at a rate of 10 m/min. The sample specimen thus applied was reinforced flush with a stable adhesive strip which served as a support for the travel sensor. The sample thus prepared was suspended vertically by means of the test plate, and loaded at the lower end with a weight of 100 g. The test temperature was 40° C., the test duration 15 minutes. The parameter determined was the distance of shear after the specified test duration at constant temperature, with the value being reported in μm and being the maximum distance of shear after loading for 15 minutes.

[0131] B2. Mechanical Properties

[0132] For the samples V1, V2, E1 and E2, the tensile strength and the elongation at break were determined on sample specimens having a clamped length of 100 mm, which were loaded at 300 mm/min along the web direction. The experiments were conducted on a Zwick Roell 2020 universal testing machine from Zwick GmbH.

[0133] B3. Performance Properties

[0134] The samples V1, V2, E1 and E2 were used for preparing steel opposed rolls of a polyethylene extrusion coating plant and were tested under typical service conditions. The useful life of the bonded covering, i.e. the time until it was necessary to renew the adhesive tape; the residue of adhesive remaining on the roll on removal; and the handling suitability on detachment of the melted LD-PE were evaluated qualitatively by trained employees with many years of experience in the area of extrusion coating, with the performance being better the more “+” were awarded.

[0135] C. Results

[0136] The results of the experiments described above are compiled in table 1 below, with the technical adhesive and mechanical properties of V1 being taken from the corresponding product specification.

TABLE-US-00001 TABLE 1 Results of measurements Property Unit V1 V2 E1 E2 Technical adhesive properties Peel adhesion (steel) N/cm 2.5 3.1 3.5 4.2 Anchoring force N/ cm >6 5.8 7.8 7.5 (etched PET) Shear test μm <50 29 15 12 Mechanical properties Tensile strength N/15 mm >79 82 42 44 Elongation at break % >100 128 280 337 Performance properties Service life of bonded − + ++ +++ ++++ covering Residues of adhesive − + ++ +++ +++ Handling suitability − + ++ +++ +++

[0137] From the results it is apparent that adhesive tapes of the invention exhibit advantageous peel adhesion on steel and etched PET and also a favourable shear behaviour at elevated temperatures. Moreover, adhesive tapes of the invention possess mechanical properties which are advantageous for the target application, and in performance testing they exhibit consistently improved performance properties. These advantages are also manifested in particular when the adhesive tapes are made relatively thin.

LIST OF REFERENCE SIGNS

[0138] 10 roll [0139] 12 coating plant [0140] 14 substrate [0141] 16 lateral face [0142] 18 adhesive tape [0143] 20 carrier layer [0144] 22 adhesive layer [0145] 24 prepared roll [0146] 26 clearance [0147] 28 release material [0148] 30 coating unit