Printable Substrates with Barrier Properties

Abstract

The present invention relates to a coated substrate comprising a substrate and a crystalline triazine layer, the crystalline triazine layer comprising an alkylolated triazine, the layer being resistant to alcohols, and the coated substrate having oxygen barrier properties. The crystalline triazine layer may comprise an alkyl ether and / or alkylene bridged triazine. A process for preparing a coated substrate comprises providing a coated substrate having a crystalline triazine layer, the substrate optionally having a metal or metal oxide layer between the substrate and the triazine layer, and applying a vapor of a reactive compound capable of chemically reacting with the triazine layer such that the triazine is alkylated and / or the triazine layer comprises an alkyl ether and / or alkylene bridged triazine, wherein the coated substrate has oxygen barrier properties and the triazine layer is resistant to alcohols.

Description

[Technical field]

[0001] The present invention relates to a printable substrate having barrier properties and a method for providing such a substrate. [Background technology]

[0002] In many industries, barrier properties, for example with respect to oxygen and water vapor transmission, are important. For example, in the food and feed industry, oxygen barrier is important to preserve food and feed products. In the display industry, high oxygen barrier is also important to protect oxygen-sensitive compounds. In both applications, the barrier properties of a single thin layer plastic are generally insufficient. Therefore, so-called barrier layers are applied onto these substrates to improve the barrier properties.

[0003] Currently, substrates with good transparency and barrier properties are well known in the art. SiOx or AlOx layers vacuum deposited on plastic films are commonly used. However, these coatings have the drawback of being very brittle and therefore losing their barrier properties during downstream processing steps such as slitting and printing. In particular, direct printing on these coatings results in a dramatic loss of barrier. To maintain the barrier after printing, these films are often coated with a lacquer offline, i.e. after the vacuum deposition step. However, this requires additional processing steps and large investments. Furthermore, these lacquers are not suitable for application on temperature-sensitive polymers such as polyethylene (PE). For example, PE-AlOx coated with a water-based lacquer may lose its barrier properties due to shrinkage of PE, especially during the drying step at high temperatures in an oven required to remove the water. Due to environmental considerations, recyclable mono-PE laminates are in high demand as an alternative to non-recyclable multi-layer laminates. However, these mono-PE laminates cannot be used for critical applications where a high barrier after direct printing is required. Moreover, it should be added that off-line lacquers are often coated with a coating weight of 0.5-1.0 grams per square meter, which negatively impacts the recyclability of mono-PE laminates. In such critical applications, it is even more important that the barrier properties are independent of relative humidity (RH). In addition, the barrier properties of PE films are inferior to those of films currently used in multilayer laminates, such as PET. Therefore, the barrier properties achieved with vacuum-coated PE are often inferior to those achieved with vacuum-coated PET. In order to replace multilayer laminates based on PET with mono-laminates based on PE, it is important to achieve barrier values ​​with vacuum-coated PE similar to their PET counterparts. Therefore, there is a need to improve the quality and effectiveness of vacuum-coated barrier layers without affecting the recyclability of plastic films.

[0004] It is possible to protect the AlOx layer with a thin layer of a crystalline triazine such as melamine. In addition to protection, the thin layer of crystalline triazine can improve the barrier properties of other vacuum coated layers such as AlOx and aluminum, which is important because, as mentioned above, vacuum coated PE cannot reach similar barrier values ​​as vacuum coated PET without additional barrier enhancement. Furthermore, melamine is biodegradable and is coated as a much thinner layer compared to offline lacquers, so has minimal impact on recyclability. Melamine can be deposited on the substrate by vacuum deposition.

[0005] However, the protective properties and barrier enhancement of crystalline melamine coatings are reduced in direct printing processes, depending on the solvents used in the printing ink.

[0006] A crystalline triazine layer can be applied directly onto a substrate, for example providing oxygen barrier properties to the substrate, and these barrier properties can deteriorate upon direct printing or in the presence of moisture.

[0007] Therefore, there is a need for an alternative transparent barrier layer that has good barrier properties after downstream processing steps such as direct printing with a wide variety of inks. Furthermore, the alternative transparent barrier layer should preferably be biodegradable with minimal impact on recyclability, applicable to temperature sensitive polymers such as PE that achieve and retain high barrier, and / or whose barrier properties are not highly dependent on relative humidity (RH). Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide a substrate having barrier properties which are substantially unaffected by direct printing.

[0009] It is a further object of the present invention to provide a substrate having barrier properties which are not highly dependent on RH.

[0010] It is a further object of the present invention to provide a printed multi-layer structure with good barrier properties and bond strength that is optionally biodegradable and / or recyclable. [Means for solving the problem]

[0011] One or more of the above objects are achieved according to the present invention by providing a coated substrate having oxygen barrier properties, comprising a substrate and a layer of a crystalline triazine, the crystalline triazine layer comprising an alkylolated triazine, the layer being resistant to alcohols.

[0012] In a preferred embodiment, the crystalline triazine layer comprises an alkyl ether and / or alkylene bridged triazine, which layer is resistant to alcohol.

[0013] In a preferred embodiment, 90 mol% or more of the triazine layer is unreacted and in crystalline form. Alkoxylated triazines, alkyl ether bridged triazines and alkylene bridged triazines are amorphous and therefore not crystalline. It will be understood by those skilled in the art that the barrier properties come from the crystalline triazines which constitute the majority of the triazine layer.

[0014] One or more of the above objects are further achieved according to the present invention by a process for preparing a coated substrate having oxygen barrier properties and being resistant to alcohol, the process comprising: a) providing a substrate having a crystalline triazine layer, optionally having a metal or metal oxide layer between the substrate and the triazine layer; b) applying a vapor of a reactive compound capable of chemically reacting with said triazine layer, such that the triazine is alkylolated and / or the triazine layer comprises an alkyl ether and / or alkylene bridged triazine.

[0015] In a preferred embodiment, the reactive compound is an aldehyde, more preferably formaldehyde.

[0016] In a more preferred embodiment, the reactive compound is dissolved in water.

[0017] In a further preferred embodiment, the treatment of the crystalline triazine layer with vapors of the reactive compound is carried out in a continuous roll-to-roll process at atmospheric pressure, for example integrated into a slitting machine.

[0018] In a further preferred embodiment, the treatment of the crystalline triazine layer with vapors of a reactive compound is carried out in a continuous roll-to-roll process under reduced pressure, preferably immediately after deposition of the crystalline triazine layer.

[0019] In a further preferred embodiment, the vapor of the reactive compound is superheated before being applied onto a substrate having a crystalline triazine layer, the substrate optionally having a metal or metal oxide layer between the substrate and the triazine layer. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of a continuous roll-to-roll processing unit. [Diagram 2] FIG. 2 is a modified schematic diagram of a roll-to-roll processing unit. [Diagram 3] 1 is an exemplary scheme for adjusting the pressure, volume and temperature of steam to a nozzle. [Figure 4] 1 illustrates an embodiment of a vapor processing unit disposed within a vacuum chamber. [Diagram 5] 1 is an embodiment in which a heat shield is added to the steam pipe. [Figure 6] 1 is a photographic image of the effect of a droplet of ethanol on a melamine coating both before (a) and after (b) treatment with steam and formaldehyde. [Figure 7]Tape test on printed melamine coating both before (a) and after (b) steam formaldehyde treatment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Crystalline triazine layers, such as crystalline melamine layers, have been described as barrier layers for reducing oxygen transmission through plastic substrates such as polypropylene or polyethylene-terephthalate (see, for example, US6632519, WO2004 / 101662 or WO2004 / 101843). The crystalline triazine layers are preferably applied under reduced pressure (vacuum) onto various substrates. Although oxygen transmission is indeed substantially reduced, the improved barrier properties disappear after printing (with alcohol-based inks) and / or after measurement at 85% RH. Furthermore, the bond strength of laminates containing printed crystalline triazine layers is lower compared to that of laminates containing unprinted crystalline triazine layers.

[0022] A method to preserve the barrier properties of the crystalline triazine layer at high relative humidity and / or after printing has been described by applying a protective layer over the crystalline triazine layer (see, for example, US8318276). However, this method has the drawback of requiring additional processing steps and investments.

[0023] Surprisingly, it has been found that by exposing a crystalline triazine layer to vapors of reactive compounds in a manner such that the triazine is alkylolated and / or the triazine layer comprises an alkyl ether and / or alkylene bridged triazine, the crystalline triazine layer maintains its barrier properties after direct printing with an alcohol-based ink and / or after measurement at 85% RH. Furthermore, the bond strength of a laminate comprising a printed crystalline triazine layer that has been treated with vapors of reactive compounds is higher than the bond strength of a laminate comprising an untreated printed crystalline triazine layer.

[0024] In a preferred embodiment, 90 mole % or more of the triazine layer is unreacted and in crystalline form. Alkoxylated triazines, alkyl ether bridged triazines and alkylene bridged triazines are amorphous and therefore not crystalline. It is important to maintain the majority of the crystalline triazine layer in the crystalline unreacted form, since the amorphous portion of the layer does not impart oxygen barrier properties.

[0025] In a more preferred embodiment, at least 98 mole percent of the triazine is unreacted.

[0026] In a more preferred embodiment, 0.01 mol% or more is reacted. Thus, in a preferred embodiment, 0.01 mol% to 2 mol% of triazine is reacted to form alkoxylated triazine, alkyl ether bridged triazine, and / or alkylene bridged triazine. The inventors have found that sufficient triazine is reacted to provide alcohol resistance and water resistance while maintaining barrier properties, since the maximum portion of the crystalline triazine layer remains unchanged.

[0027] Furthermore, this method has the advantage that it can be carried out in a vacuum chamber immediately after deposition of the crystalline triazine layer.

[0028] Alternatively, the method can be easily integrated into downstream processing steps such as slitting. Vacuum coated films are often slit and cut to various sizes. The steam treatment device can be retrofitted to the slitting machine, for example, and thus combined with the slitting operation.

[0029] Since most inks used in the packaging industry contain alcohol, such as ethanol, as a solvent, resistance to alcohol indicates that the layer is not damaged by such solvents, which is a prerequisite for good printability.

[0030] In the following, a simple method is shown whether ethanol damages a surface. According to this method, a drop of ethanol is applied to the surface of a crystalline triazine layer, such as a crystalline melamine layer. After the evaporation of the ethanol, white spots appear on the surface of the crystalline melamine layer, which can be observed by the naked eye, indicating that this layer has been damaged by the action of ethanol. However, a crystalline melamine layer containing alkylolated and alkyl ether and / or alkylene bridged melamine does not leave any spots, indicating that the layer has not been damaged by the action of ethanol.

[0031] Similar results were observed when droplets of water were placed on a crystalline melamine surface: unprotected films resulted in white spots, whereas after treatment according to the invention no damage was observed.

[0032] A process for providing a crystalline triazine layer, wherein the triazine is alkylolated and / or the triazine layer comprises an alkyl ether and / or alkylene bridged triazine, comprises providing a vapor of a reactive compound that contains a chemical functionality capable of reacting with the crystalline triazine layer.

[0033] In one embodiment of the present invention, the vapor of the reactive compound contains at least one aldehyde group.

[0034] Preferred reactive compounds contain one or two aldehyde groups and have a molecular weight between 30 and 300 daltons, more preferably between 30 and 100 daltons.

[0035] Suitable aldehydes include, but are not limited to, C1-C20 straight, branched, or cyclic aliphatic aldehydes, C2-C20 straight, branched, or cyclic alkenyl aldehydes, C2-C20 straight, branched, or cyclic alkynyl aldehydes, C6-C14 aromatic aldehydes, and C4-C14 heteroaromatic aldehydes.

[0036] The term "alkenyl group" includes within its meaning monovalent ("alkenyl") and divalent ("alkenylene") straight or branched chain unsaturated aliphatic hydrocarbon groups having from 2 to 10 carbon atoms, e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, and having at least one double bond anywhere in the alkyl chain, where applicable, of either E, Z, cis or trans stereochemistry. Examples of alkenyl groups include, but are not limited to, ethenyl, vinyl, allyl, 1-methylvinyl, 1-propenyl, 2-propenyl, 2-methyl-1-propenyl, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, Examples of the alkyl group include 1,3-pentadienyl, 2,4-pentadienyl, 1,4-pentadienyl, 3-methyl-2-butenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 1,3-hexadienyl, 1,4-hexadienyl, 2-methylpentenyl, 1-heptenyl, 2-heptentyl, 3-heptenyl, 1-octenyl, 1-nonenyl, and 1-decenyl.

[0037] The term "alkynyl group" as used herein includes within its meaning monovalent ("alkynyl") and divalent ("alkynylene") straight or branched unsaturated aliphatic hydrocarbon groups having from 2 to 10 carbon atoms and having at least one triple bond anywhere along the carbon chain. Examples of alkynyl groups include, but are not limited to, ethynyl, 1-propynyl, 1-butynyl, 2-butynyl, 1-methyl-2-butynyl, 3-methyl-1-butynyl, 1-pentynyl, 1-hexynyl, methylpentynyl, 1-heptynyl, 2-heptynyl, 1-octynyl, 2-octynyl, 1-nonyl, 1-decynyl, and the like.

[0038] The term "cycloalkyl" as used herein refers to a cyclic saturated aliphatic group and includes within its meaning monovalent ("cycloalkyl") and divalent ("cycloalkylene") saturated, monocyclic, bicyclic, polycyclic or fused polycyclic hydrocarbon groups having 3 to 10 carbon atoms, e.g., 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, 2-methylcyclopropyl, cyclobutyl, cyclopentyl, 2-methylcyclopentyl, 3-methylcyclopentyl, cyclohexyl, and the like.

[0039] As used herein, the term "aromatic group" or variations such as "aryl" or "arylene" refer to monovalent ("aryl") and divalent ("arylene") mononuclear, polynuclear, conjugated and fused residues of aromatic hydrocarbons having 6 to 10 carbon atoms. Examples of such groups include phenyl, biphenyl, naphthyl, phenanthrenyl, and the like.

[0040] Exemplary aldehydes include, but are not limited to, formaldehyde (methanal), acetaldehyde (ethanal), propionaldehyde (propanal), butyraldehyde (butanal), pentanal, hexanal, cyclopentanecarbaldehyde, cyclohexanecarbaldehyde, benzaldehyde (phenylmethanal), cinnamaldehyde, vanillin, tolualdehyde, furfural, retinaldehyde, and dimethoxyethanal. Examples of dialdehydes include, but are not limited to, glyoxal, butanedial, and 1,5-pentanedial (glutaraldehyde).

[0041] Reaction of the amine groups of triazine compounds with aldehydes produces alkylolated triazine compounds (reaction I). Reaction of alkylolated triazines with the amine groups of other triazine compounds produces alkylene bridges (reaction IIa). Reactions between alkylolated triazine compounds produce alkyl ether bridges (reaction IIb).

[0042] Reaction I shows the reaction of primary amine groups with aldehydes. Secondary amine groups of triazine compounds can also react with aldehydes to produce alkylolated triazines, which can then react according to reactions IIa and IIb to form alkylene and alkyl ether bridges. Thus, depending on the chemical structure of the triazine and the number of amine groups, many different alkylolated triazine compounds can be produced, which can then form alkylene and alkyl ether bridges.

[0043] R1-NH2+(R2-COH).H2O → R1-NH-CHR2OH+H2O Reaction I R1-NH-CHR2OH+R1-NH2 → R1-NH-CHR2-NH-R1+H2O Reaction IIa R1-NH-CHR2OH+R1-NH-CHR2OH→R1-NH-CHR2O-CHR2-NH-R1+H2O Reaction IIb Where R1 = triazine, R2 = H, -CH3, and -(CH2) n -CH3(n≧1), cyclic alkenyl, cyclic alkynyl, C6-C14 aromatic, and C4-C14 heteroaromatic

[0044] In a preferred embodiment of the invention, the reactive compound vapor contains formaldehyde (R2 = H).

[0045] In one embodiment of the present invention, the vapor of the reactive compound comprises dimethoxyethanal.

[0046] In a further preferred embodiment of the invention, the reactive compound vapor contains glyoxal (R2=-CH=O). The reaction products of triazine compounds such as melamine with glyoxal are reviewed, for example, in the article by Xi et al. entitled "Melamine-Glyoxal-glutaraldehyde Wood Panel Adhesives without Formaldehyde" (Polymers 2018;10:22).

[0047] The reaction products shown in Reactions I, IIa, and IIb are 13 The spectra were recorded on a Varian unity 300 using DMSO as the solvent. 1 Spectra with complete decoupling by H noise illumination were measured with a pulse (908 width) repetition time of 11 s (1 s acquisition + 10 s delay). NMR spectra were analyzed according to the peak assignments presented by Tomita and Ono (J Polym Sci:Polym Chem 1979;17:3205). Other methods include high performance liquid chromatography (HPLC) as outlined by Jahromi (Macromolecular Chemistry and Physics 1999;200:2230-2239), as well as Fourier transform infrared spectroscopy (FTIR) and matrix-assisted laser desorption / ionization mass spectrometry (MALDI-TOF) as described by Xi et al. (Polymers 2018;10:22).

[0048] The treatment with the vapor of the reactive compound is preferably carried out in a continuous roll-to-roll process at atmospheric or reduced pressure.

[0049] In another embodiment of the present invention, the chemical functional groups include acids, ketones, esters, epoxides, anhydrides, isocyanates, azos, diazos, azides, hydrazines, azides, acrylates, acrylic acids, amides, imides, sulfonates, phosphonates, and peroxides, which are applied to the surface of the crystalline triazine layer in such a way that a crosslinking reaction occurs.

[0050] In a further preferred embodiment, the vapour of the reactive compound is generated by means of a vapour generator, which is for example supplied with a solution of the reactive compound dissolved in a solvent, preferably water.

[0051] The reactive compound is preferably formaldehyde, also called formalin, dissolved in water. The weight percentage of formaldehyde in water is preferably 37% w / w or less, more preferably 10% w / w or less. The amount of formaldehyde is generally 0.01% w / w or more, preferably 0.1% w / w or more. Exemplary concentrations are 0.37% w / w, 0.74% w / w, 1% w / w and 1.11% w / w.

[0052] The pH of formalin is generally between 5 and 10, preferably between 6 and 8, even more preferably about 7. The pH is preferably slightly basic, for example between 7 and 9.

[0053] The steam generator pressure is preferably below 20 bar (abs), more preferably below 10 bar, even more preferably below 5 bar. The steam pressure is generally above about 1.1 bar (abs). Most preferably, the steam pressure is between 1.5 bar (abs) and 5 bar (abs). The steam generator pressure is directly related to the steam power output, i.e. the higher the pressure the higher the power output. The steam generator produces saturated steam and therefore the pressure is indicative of the temperature.

[0054] The amount of steam dispersed on the substrate is preferably 100 kg / hr or less, more preferably 20 kg / hr or less, even more preferably 10 kg / hr or less, depending on the width of the substrate. In general, the amount of steam is about 0.1 kg / hr or more, preferably 1 kg / hr or more. Most preferably, the amount of steam is about 5 kg / hr.

[0055] In a further preferred embodiment, the saturated steam is fed to a superheater which produces superheated steam. The temperature of the superheated steam is preferably 1200°C or less, more preferably 700°C or less, even more preferably 400°C or less. Typically, the temperature of the superheated steam is 150°C or more, preferably 200°C or more. An exemplary temperature is between 300°C and 400°C, for example about 360°C.

[0056] In order to achieve reaction between the triazine layer and the reactive compound, it appears to be important to apply sufficient heat to the crystalline triazine layer by having a sufficient amount of hot steam reach the triazine layer, as exemplified below.

[0057] <Outline of equipment and process> A schematic diagram of a continuous roll-to-roll processing unit is shown in Figure 1. The overview provided below applies to a variety of methods.

[0058] The substrate coated with the crystalline triazine layer (1) is fed into the cooking chamber (2). A boiler (3) fed with a solution of a reactive compound, e.g. formalin (4), produces saturated steam, which is then superheated by a superheater (5). A superheater is a device used to convert saturated or wet steam into superheated or dry steam.

[0059] Surprisingly, the inventors have found that the use of superheated steam reduces the condensation of water in the substrate (1). Furthermore, the use of a superheater allows for faster reactions due to higher temperatures and therefore faster line speeds, i.e., productivity. The use of a superheater also allows for increased temperatures without increasing pressure. It is well known to those skilled in the art that the velocity of steam exiting the nozzle increases with increasing pressure. Therefore, processing at low pressure is preferred to prevent damage to the crystalline triazine layer by high-velocity steam at high pressure.

[0060] Suitable superheaters, such as electric process heaters and various types of heat exchangers, are manufactured by Heat Systems (https: / / www.heatsystems.de / heating.html).

[0061] Excess steam is exhausted by an exhaust pipe (6). The substrate coated with the crystalline triazine layer (1) is optionally preheated by infrared (IR) heaters (7) or other heating methods normally used by those skilled in the art, such as electron beams or other radiation sources such as ultraviolet (UV) or near infrared (NIR). It is also possible to arrange the heaters (7) after the steaming chamber (2). It is further possible to guide the substrate (1) over a temperature-controlled coating drum, in which case the temperature of the substrate is the temperature at which the coating drum is controlled. One method of ensuring that the substrate has a defined temperature is applicable when there is at least one section, plane or side of the substrate that is not subjected to treatment, and then said section, plane or side can be brought into contact with a heated surface to bring the temperature to the desired level and to maintain it there.

[0062] The substrate (1) treated with the superheated formalin gas is collected on a roll (8).

[0063] The cooking chamber (2) consists of pipes with holes of various diameters through which the superheated steam flows. The pipes may be arranged connected to each other in parallel. The number of pipes is preferably 20 or less, more preferably 10 or less, and even more preferably 5 or less. The number of pipes is 1 or more.

[0064] The diameter of the hole is 10 mm or less, more preferably 1 mm or less, even more preferably 0.5 mm or less. In general, the size of the nozzle is about 0.1 mm or more. It is also possible to attach the nozzle to a pipe. The nozzle has different diameters, spray angles and spray shapes, such as flat fan spray nozzles or flat cone spray nozzles. Suitable spray nozzles are manufactured, for example, by Company Spraying Systems Co. (https: / / www.spray.com / products / nozzles) or Euspray (https: / / www.euspray.com / en / home-page-en / ).

[0065] Preferably, the pipe is used with a flat fan type nozzle. The spray angle is less than 150°, more preferably less than 130°, and even more preferably less than 110°. Typically, the angle is greater than 90°.

[0066] The number of nozzles and the distance between them depends on the spray angle and is determined so that the nozzles produce a substantially continuous and uniform spray along the pipe, preferably at a distance of 10 cm or less from the substrate, even more preferably 5 cm or less, usually the distance is 0.5 cm or more.

[0067] The speed of the roll-to-roll line is preferably 40 m / s or less, more preferably 15 m / s or less, and even more preferably 5 m / s or less. In general, the speed of the roll-to-roll line is 1 m / s or more, preferably 5 m / s or more, for example between 8 and 9 m / s.

[0068] The steam pipes and the pipes connecting the superheater (5) to the cooking chamber (2) are preferably heated to the same temperature as the temperature of the superheated steam. The heating of the steam pipes and the connecting pipes is preferably carried out by electrical heat tracing, for example using a heat cable provided by the company Bartec (www.bartec.de). The heating cable is preferably of the type EMK VA 4000NiCr. The steam pipes and the connecting pipes heated by the heating cable are preferably insulated with an insulating material. The insulating material is for example Rockwool ProRox® PS960. The heat capacity provided to the steam pipes by means of the heat tracing cable depends on the length of the steam pipe. The longer the steam pipe, the greater the heat capacity required to bring the steam pipe to the required temperature. For example, for a steam pipe with a length of 2500 mm, the heat capacity is preferably less than 20 kW, more preferably less than 10 kW. In general, the heat capacity of a 2500 mm steam pipe is greater than 1 kW, preferably greater than 3 kW, for example 4-6 kW.

[0069] All materials in contact with the superheated steam, including the steam pipes, connecting pipes and nozzles, are preferably made from different types of stainless steels such as austenitic, ferritic and martensitic. Austenitic stainless steels such as SUS304 and alloys such as INCONEL® have high heat resistance and high mechanical strength and are used for induction or electrically heated superheated steam generation. The material can be, for example, 304 stainless steel, which is the most common stainless steel. The steel contains both metals chromium (between 18% and 20%) and nickel (between 8% and 10.5%) as the main non-ferrous components. Other suitable types include 316 grade stainless steel, which is an austenitic form of stainless steel known for its 2-3% molybdenum content, or type 310, which has a higher chromium content (24-26%) compared to type 304 (10-20%) and a high nickel content (19-22%) versus 304 (8-10.5%). For induction heating, a non-magnetic material such as SUS316L is used. However, the material of the conductive pipe is not limited to SUS316L, but may be INCONEL alloy (Japanese Industrial Standards (JIS) alloy No. NCF601) or other materials.

[0070] Another preferred method of heating the steam pipes and connecting pipes is by jacketed piping. Jacketed piping systems feature a core pipe surrounded by a jacket pipe. Superheated steam flows through the core pipe and a heat transfer medium flows through the annular space between the core pipe and the jacket pipe. The heating medium can be superheated steam generated by the same superheater or a separate superheater. The heating medium can be thermal oil, such as Marlotherm SH manufactured by Eastman (https: / / chem-group.com / wp-content / uploads / 2020 / 07 / Marlotherm-SH-TDS.pdf). The thermal oil is heated, for example, by an i-Temp oil temperature control unit manufactured by ICS Cool Energy (https: / / www.icscoolenergy.com / sales / product / oil-temperature-control-unit / ).

[0071] The amount of steam dispersed on the substrate is preferably 100 kg / h or less, more preferably 20 kg / h or less, even more preferably 10 kg / h or less, depending on the width of the substrate. In general, the amount of steam is about 0.1 kg / h or more, preferably about 1 kg / h or more. Most preferably, the amount of steam is about 5 kg / h. This amount is preferably between 5 kg / h and 20 kg / h.

[0072] The width of the substrate may vary, for example between 500 and 6000 mm. Preferred widths are approximately 1250 mm, 1650 mm, 2450 mm and 2850 mm, which are currently standard widths.

[0073] The width of the substrate is preferably 6000 mm or less, more preferably 2850 mm or less. The width is preferably about 1250 mm or more.

[0074] In a preferred embodiment, the boiler (3) and the superheater (5) are combined into one unit. A suitable unit of this type is the W-series superheated steam generator manufactured by Tokuden (www.tokuden.com).

[0075] A modified schematic diagram of a roll-to-roll processing unit is shown in Figure 2. Here, the superheater is replaced by a heating unit (5) that heats only the steam pipe. Saturated steam enters the steam pipe and is then converted into superheated steam. This method has the advantage that the connecting pipes no longer need to be heated. Alternatively, the steam pipe can also be heated using a heat tracing cable, as previously mentioned.

[0076] A suitable device as a heating unit is the Type D Series Utility Power Super Steamer (UPSS) manufactured by Tokuden (www.tokuden.com). Such units are further described in US10337725B2 and US2019 / 0195531A1. In this unit, the steam pipe is heated by induction heating, which is a process of heating conductive materials such as metals by electromagnetic induction. High currents, generated with a special transformer, generate heat in the pipe and nozzle. Saturated steam of reactive compounds is converted into superheated steam that is dispersed on a substrate coated with crystalline triazine. In the superheated steam generator, the temperature controller is configured to perform feedback control so that the temperature can be regulated between 200°C and 2000°C. The steam pipe itself may be connected to one or more pipes that heat the saturated steam before it enters the steam pipe.

[0077] In one embodiment, the steam exiting the exhaust pipe 6 of Figures 1 and 2 is condensed and returned to the vessel 4 to form a closed loop treatment system. An example of a superheated steam recycle system is described in US9709262B2.

[0078] In a further embodiment, the use of a superheated steam generator, such as the W-series manufactured by Tokuden, is combined with the use of a heating unit, such as the Utility Power Super Steamer (UPSS) of type D-series manufactured by Tokuden (www.tokuden.com). This method has the advantage that the temperature of the superheated steam generated by the W-series can be matched to the temperature of the D-series heating unit, minimizing the drop in temperature of the steam exiting the nozzle. Alternatively, the superheated steam generated by the W-series can be combined with a steam pipe, heated using a heat tracing cable, as described above. The temperature drop can be further minimized by heating the connecting pipe between the W-series and the D-series by the method already described. In this way, the temperature of the steam generated by the W-series, the connecting pipe, and the D-series unit can be matched.

[0079] In a preferred embodiment, the steam pipe is U-shaped heated by heat tracing cables or a Type D Series Utility Power Super Steamer (UPSS) manufactured by Tokuden. In this preferred embodiment, saturated steam enters at one end of the U and is superheated. The superheated steam then exits the tube through nozzles located along the other end of the U-tube.

[0080] In a further preferred embodiment, the streamed treatment unit shown in FIG. 1 or FIG. 2 is retrofitted to a winding / unwinding system such as a roll-to-roll printing line, a lamination line, a coating line, a film inspection line or a slitting machine.

[0081] The steaming unit is preferably retrofitted to the slitting machine. The main function of the slitting machine is to convert large rolls of paper, film and foil materials (by slitting) so that these materials can be cut into narrower rolls. The slitting machine consists of three main parts: unwinding, slitter and rewinding. The steaming unit is retrofitted between the unwinding and rewinding sections. Installing a streamed processing unit on the slitting machine has the advantage that the unwinding and rewinding parts can be utilized for roll-to-roll operation and has the additional advantage that the steaming can be combined with the normal slitting process, thus eliminating an additional processing step. Suitable slitting machines for retrofitting with a steaming unit are manufactured, for example, by Company Kampf (www.kampf.de).

[0082] In a further embodiment, the steam between the boiler and the nozzle can be regulated by different valves (e.g. control valves and pressure reducing valves), flow meters and pressure gauges. The purpose of these units is to regulate the pressure, volume and temperature of the steam to the nozzle. An example of such a scheme is shown in FIG. 3, where 1 is the boiler, 2 is a valve (e.g. BSAT AND BSA BELLOWS SEALED STOP VALVES by Spirax Sarco), 3 is a VORTEX INLINE FLOWMETER (e.g. VLM20 inline vortex flowmeter made by Spirax Sarco), 4 is a pressure gauge, 5 is a control valve for adjusting the flow rate (e.g. Spira-trol™ or Spirax Sarco2 directional control valve made by Spirax Sarco), 6 is a superheater, 7 is a temperature control unit (e.g. Thyristor PID control panel class 0.5 made by Jupiter), 8 is a nozzle and 9 is a pressure reducing valve (e.g. BRV2S / BRV2SP made by Siprax Sarco).

[0083] <Base material> The substrate film may be of homogeneous material or may itself be a heterogeneous or composite material. The substrate film may comprise various layers.

[0084] Preferably, the substrate is a film having a thickness between 3 μm and 1 mm, preferably between 5 μm and 100 μm.

[0085] Preferably, the film comprises a polymer or cellulosic material. Examples of polymeric compounds are thermoplastic and thermosetting compounds. Suitable examples of thermoplastic compounds include polyolefins, polyolefin-copolymers, polyvinyl alcohol, polystyrene, polyesters and polyamides. Suitable examples of such polymers include HD or LD polyethylene (PE), LLD polyethylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, polypropylene (PP) and polyethylene terephthalate (PET). These thermoplastic compounds are often used in the form of films, either as is or oriented, and such orientation can be biaxial, for example biaxially oriented polypropylene film (BOPP), biaxially oriented polyethylene terephthalate (BOPET), biaxially oriented polyamide film (BOPA) and biaxially oriented polyethylene (BOPE). Orientation can be performed either by tender frame sequential biaxial stretching or tender frame simultaneous biaxial stretching. Other methods for simultaneous biaxial orientation include the multi-bubble or triple-bubble blown method, in which a tube is first extruded, then rapidly cooled and then heated to the stretching temperature. The synchronous increase in drawing speed and cell expansion due to internal pressure results in the necessary simultaneous orientation process. Polyethylene films can also be unidirectionally oriented, or machine direction oriented (MDOPE).

[0086] In one embodiment, a primer coating can be applied onto the oriented polyethylene film. In an exemplary embodiment, the skin, i.e., substrate, of the oriented polyethylene film may be treated to provide increased active adhesion sites thereon, and a continuous coating of a primer material may be subsequently applied to the so-treated film surface. Such primer materials are well known in the art and include, for example, epoxy, poly(ethyleneimine) (PEI), and polyurethane materials. U.S. Pat. Nos. 3,753,769, 4,058,645, and 4,439,493, each of which is incorporated herein by reference, disclose the use and application of such primers. The primer provides an overall adhesively active surface for complete and secure bonding with the subsequently applied coating composition, and can be applied to the film by conventional solution coating means, for example, by roller application. The primed oriented polyethylene film is then vacuum coated with Al, AlOx, or SiOx, followed by topcoating with a crystalline triazine layer, which is then treated with vapors of a reactive compound.

[0087] In a further embodiment, the optionally primed skin layer of the substrate can be coated with an EVOH polymer. Here, EVOH is understood to include only EVOH polymer, EVOH and PVOH polymer, or only PVOH polymer. Coating can be achieved by any known technique. In one exemplary embodiment, the EVOH coating comprises, consists essentially of, or consists of Evalca HR3010. The EVOH-coated oriented polyethylene film is then vacuum coated with Al, AlOx, or SiOx, followed by topcoating with a crystalline triazine layer, which is then treated with a vapor of a reactive compound.

[0088] Suitable examples of primed and / or EVOH coated oriented polyethene films are described in US11135820B2.

[0089] The polymer substrate may also contain additives that induce biotransformation to make fossil-based polymers such as polypropylene biodegradable. Additives suitable for biotransformation are manufactured by Polymateria (www.polymateria.com).

[0090] In a further embodiment, a BOPP film containing additives that render it biodegradable, such as those described in US10570236, is vacuum coated with a melamine layer and then treated with a vapor of a reactive compound. Since melamine is a biodegradable compound, this provides a completely biodegradable barrier-coated film solution.

[0091] The substrate film may also be made of bio-based materials, either biodegradable or non-biodegradable. Examples of bio-based non-biodegradable materials include PE, EVA, PVC (partially bio-based) from bioethanol or bio-naphtha, PP from waste oils and fats. Examples of polyamides include PA5,10,11 (fully bio-based), PA4,10,5,6,6,10,6,12,10,10,10,12 (partially bio). Examples of polyesters include PET (fully bio-based), PEF-polyethylene furanoate, PTF-polytrimethylene furanoate. Examples of bio-based biodegradable materials include polylactic acid (PLA), polyhydroxyalkanoates (PHA, PHB, PHBV, PHBH, PHBO, etc.), aliphatic and aliphatic / aromatic copolyesters (PBS, PBSA, PBAT, PCL), starch blends and derivatized starch blends, polyvinyl alcohol and polyglycolic acid. Other examples include protein-based materials such as keratin-, zein-, casein-, whey- and soy-based (e.g., whey-based barrier layers, Lactips / BASF casein-based water soluble polymers), as well as polysaccharides (e.g., chitosan) and bacterial-, algae- and fungal-based materials.

[0092] In a preferred embodiment, a compostable film such as a film manufactured by PHA or Company Tipp (tipa-corp.com) is made of (optionally Al, AlO x or SiO x The material is vacuum coated with melamine, then (top) coated with a crystalline triazine layer and then treated with the vapour of a reactive compound. Vacuum coated crystalline triazine layers such as melamine have the advantage that they do not adversely affect compostability.

[0093] When the substrate is a cellulose base such as paper, the type of the paper substrate is not particularly limited and can be appropriately selected from printing paper or wrapping paper depending on the application. Examples of the paper substrate include glassine paper, parchment paper, high-grade printing paper, medium-grade printing paper, low-grade printing paper, printing tissue paper, colored high-grade paper, art paper, coated paper, kraft paper, container board, coated cardboard, ivory paper, cup base paper, calendar paper, super calendar paper, etc.

[0094] A suitable paper type is for example Solide Lucent paper manufactured by UPM Specialty Papers, branded as UPM Solide™ Lucent (www.upmspecialtypapers.com). UPM Solide Lucent is ideal for several reasons. It is extremely smooth and dense, allowing for a lightweight and very uniform coating. Its high strength, density and excellent folding properties are exactly what is needed to ensure the mechanical integrity of the packaging, as well as the barrier performance in the later stages of conversion and throughout the packaging value chain. The safety of UPM Solide Lucent products is ensured by being made from virgin cellulose fibres from responsibly grown forests. Being a natural and renewable material, it requires some fine-tuning during the conversion process. Different end uses and packaging formats require different basis weights as well as strength and stiffness properties. This is why UPM Solide Lucent is available in basis weights from 45 to 90 grams per square meter.

[0095] The paper base material has a basis weight of 600 g / m 2 It is preferable that the thickness is less than 30 g / m 2 ~500g / m 2 More preferably, in one preferred embodiment, the weight is 150 g / m 2 ~400g / m 2 In another preferred embodiment, the weight is between 45 g / m 2 ~90g / m 2 It is.

[0096] In a preferred embodiment, the thickness is 40 to 100 g / m 2 Clay-coated paper having a weight of 1000g is first coated with a water-based or solvent-based lacquer, for example by direct or offset gravure coating, to smooth the surface of the paper. A suitable primer is manufactured, for example, by Michelman (www.michelman.com) branded as VaporCoat®. The coated paper is then vacuum coated with Al, AlOx or SiOx, followed by topcoating with a crystalline triazine layer, which is then treated with a vapor of a reactive compound. Finally, a sealant layer can be applied, for example by direct or offset gravure coating, on top of the treated triazine layer to provide sealing properties.

[0097] Treatment with vapors of reactive compounds can also be incorporated with the application of a crystalline triazine layer onto a substrate such as paper using an organic release layer in the process described in WO2020 / 229675.

[0098] <Low pressure treatment> In a further preferred embodiment of the present invention, the crystalline triazine compound may in principle include any triazine compound, for example melamine, melam, melem, or melon.

[0099] Preferably, the triazine compound is melamine.

[0100] The thickness of the triazine layer is generally about 10 to 300 nanometers.

[0101] In applications where the triazine is deposited directly onto the substrate, the preferred thickness is between 50 and 300 nm.

[0102] For applications where the triazine layer is applied onto a metal (eg Al) or metal oxide (eg AlOx or SiOx) coated substrate, the preferred thickness is between 10 and 60 nm.

[0103] The crystalline triazine compounds can be deposited according to known methods. Deposition as such is a process known to those skilled in the art and is preferably carried out in a roll-to-roll process. The deposition step is carried out under reduced pressure, i.e. at a pressure below atmospheric pressure. In the process according to the invention, the pressure is generally less than about 1000 Pa (10 mbar), preferably less than about 100 Pa (1 mbar), even more preferably less than about 10 Pa (0.1 mbar). It is possible to combine the deposition of the crystalline triazine compounds with the deposition of the metal (oxide). In this case, it is beneficial to separate the evaporation zones for the metal (oxide) and the crystalline triazine compounds by a partition. This will prevent the mixing of the various vapors and result in better performance. The compartment for the deposition of the crystalline triazine is preferably less than 1 Pa (1×10 -2 mbar) ~ 0.1 Pa (10 -3 Typically, the compartment for deposition of metals or metal oxides has a pressure of about 0.1 Pa (10 -3 mbar) ~ 0.01 (10 -6 The pressure is 100 kPa (mbar).

[0104] The temperature of the substrate in the deposition step is about −60° C. or higher, preferably about −30° C. or higher, even more preferably about −20° C. or higher, and most preferably about −15° C. or higher. The temperature of the substrate is generally about +125° C. or lower, preferably about +100° C. or lower, even more preferably about +80° C. or lower, and most preferably about 30° C. or lower. If the deposition step is carried out on a substrate guided over a temperature-controlled coating drum, the temperature of the substrate is the temperature to which the coating drum is controlled.

[0105] An apparatus suitable for vacuum deposition of crystalline triazine compounds in a roll-to-roll setup is an apparatus for depositing metals or metal oxides on a substrate under vacuum, comprising a take-up roll and at least one vacuum chamber having a metal or metal oxide deposition section and / or a deposition of crystalline triazine compound section comprising a triazine compound evaporator.

[0106] Apparatus for depositing metals, metal oxides, and triazine compounds such as melamine are known.

[0107] In a preferred embodiment, the deposition apparatus comprises a vacuum chamber and a heater for evaporating the crystalline triazine compound, and the evaporator is heated by an electric heater. Another preferred method of heating the evaporator is by a jacketed design, where the crystalline triazine is present in the core part of the evaporator, and the heating medium flows in the annular space between the core and the outer part of the evaporator. The heating medium can be superheated steam or thermal oil generated by a superheater. The heating medium is preferably a thermal oil, such as Marlotherm SH (https: / / chem-group.com / wp-content / uploads / 2020 / 07 / Marlotherm-SH-TDS.pdf) manufactured by Eastman. The thermal oil is heated by, for example, an i-Temp oil temperature control unit (https: / / www.icscoolenergy.com / sales / product / oil-temperature-control-unit / ) manufactured by ICS Cool Energy. This unit provides precise control of temperatures up to 400°C.

[0108] In one embodiment, the evaporator is preferably located outside the vacuum chamber, but is connected within the vacuum chamber by heated gas. This has the advantage that the evaporator can remain at operating temperature when the vacuum chamber is opened to place the next roll to be coated. In this way, the effective cycle time can be extended.

[0109] In a further embodiment, roll-to-roll vacuum deposition is carried out in an air-to-air system, whereby the substrate enters the vacuum chamber at atmospheric pressure and exits the chamber after the different layers have been vacuum deposited, returning to atmospheric pressure again. This method has the advantage that vacuum deposition can be combined in-line with the process of steam treatment as outlined in Figures 1 and 2.

[0110] In a preferred embodiment, the vapor treatment unit is located within a vacuum chamber as shown in Figure 4. Here, the vacuum chamber 10 is divided into different compartments having different or similar pressures. Section A(1) is for unwinding and winding Section B(2) is a metal (oxide) deposition (optional) Section C(3) is a triazine (e.g. melamine) deposit Section D(4) is the steam handling section

[0111] FIG. 4 shows a simplified schematic diagram of a vacuum chamber that may consist of various rolls that guide the substrate (5) through the various sections. The substrate (5) first passes through section A (1), where it can be optionally coated with a metal (e.g. Al) or metal oxide (AlOx or SiOx) layer in section B (2) by a metal (oxide) evaporator (6). The substrate (5), optionally coated with a metal or metal oxide layer, is coated with a triazine compound, e.g. melamine, in section C (3) by a triazine (e.g. melamine) evaporator (7). The triazine-coated substrate is treated in section D (4) with superheated steam from a cooking chamber (8) in a process such as the one outlined in FIG. 1 or FIG. 2. The triazine-coated substrate after treatment with reactive steam (9) is wound in section A (1) and prepared for further handling and use.

[0112] The pressure in the section A (1) for unwinding and winding the substrate is 1 Pa (1 x 10 -2 mbar) ~ 0.1 Pa (1 × 10 -3 The pressure in compartment B(2) for the deposition of metals or metal oxides is about 0.1 Pa (1×10 -3 millibars) ~ 10 -4 Pa(1×10 -6 The pressure in section C(3) for the deposition of the crystalline triazine compound is 10 Pa (1×10 -1 mbar) ~ 0.01 Pa (1 × 10 -4The pressure in the section D(4) for the steam treatment is preferably 10 Pa (1×10 -1 millibar) ~ 1 Pa (1 × 10 -2 The reaction is carried out at a pressure of 100 kPa (mbar).

[0113] In one embodiment, compartments C(3) and D(4) are combined into one compartment. In that case, the pressure is preferably less than 10 Pa (1×10 -1 mbar) ~ 0.1 Pa (1 × 10 -3 (millibar).

[0114] In a further embodiment, compartments A(1), C(2) and D(3) are combined into one compartment. In that case, the pressure is preferably less than 10 Pa (1×10 -1 mbar) ~ 0.1 Pa (1 × 10 -3 millibars).

[0115] Generally, the amount of steam dispersed onto the substrate is preferably 100 kg / hr or less, more preferably 20 kg / hr or less, and even more preferably 5 kg / hr or less. Generally, the amount of steam is about 0.1 kg / hr or more, and preferably about 1 kg / hr or more.

[0116] However, when the deposition of triazine in section C (3) is combined with the steam treatment in section D (4), it is important to select a pressure that allows successful deposition of triazine. Simulation data show that the pressure of 1 Pa (1×10 -2 This indicates that to maintain a pressure of 1000 psi (mbar), the maximum steam flow rate must be 5.75 kg / h.

[0117] The steam pipe can be similar to the steam pipe for processing under atmospheric pressure, including holes or nozzles as described above. As with processing under atmospheric pressure, it is important to heat the steam pipe under vacuum to the same temperature as the temperature of the steam. Similar methods for heating the steam pipe under vacuum can be used as those already described for heating the steam pipe under atmospheric conditions, i.e., electric heating (hearing) tracking, double jacketed heating, and induction heating. Heating can also be performed by electron beam heating.

[0118] In a preferred embodiment, a heating shield is added to the steam pipe. This is shown in Figure 5. When steam is present in the steam pipe (1), it expands rapidly under vacuum. To prevent expansion and cooling and thus ensure that the steam arrives at the top of the substrate (3), the steam can be guided by a shield (2) that confines the steam in the area between the steam pipe (1) and the substrate (3). It is important that the shield (3) is heated to the same temperature as that of the steam pipe (1) to avoid condensation on the shield. This can be achieved, for example, by electrical heating tracing, induction heating or electron beam heating, as explained above. (4) denotes the vacuum chamber and 5 denotes the coating drum.

[0119] In a further preferred embodiment, the substrate is heated before, during and / or after the application of steam by the methods already described, such as heated guide rollers or a radiation heating source, e.g. UV, IR, NIR, etc. Other heating methods include electron beam heating.

[0120] <Printing process> Films used in the packaging industry, especially in the food packaging industry, generally have both protective and decorative purposes. For these purposes, various techniques are available. The decorative aspect is provided by printing. Two common printing methods in flexible packaging using plastic films are flexography and gravure.

[0121] Flexographic printing is provided by having a large guide central drum around which smaller printing drums are placed, the smaller drums being made of a rubber-like material. The large inner drum determines the curve that the film undergoes, so the film undergoes a relatively small mechanical bending force. On the other hand, the small roll with the printing pattern exerts pressure on the places where the pattern should be printed, so the pressing force is higher than in the case of gravure. Nevertheless, the roll is of a rubber-like material, which somewhat cushions the pressure. The applied pressure is relatively small, since too much pressure would result in poor print quality. Inks in flexography are generally based on a mixture of alcohol and ethyl acetate. Solvents based only on ethyl acetate would deteriorate the rubber roll. Generally, several printing stations are used (e.g. with different colors and different patterns), and the ink is somewhat dried between the different printing stations, but not completely. This printing technique is similar to wet-on-wet printing.

[0122] Gravure printing (also called rotary gravure) is provided by having multiple stations with smaller drums, which are made of metal. The film experiences higher mechanical bending forces as the smaller drums bend the film over a smaller radius than the larger drums in flexo. However, the ink is present in small recesses in the metal roll, so the pressing force is less than in flexo. Inks in gravure are generally based on a large amount of ethyl acetate and a small amount of one or more alcohols, which allows for fast drying. Typically, each applied layer is dried in an oven, resulting in a substantially wet-on-dry print.

[0123] Inks generally include binders, pigments, additives, and solvents. Binders are generally polymers such as (PU) polyurethanes, (PA) polyamides, (PVB) polyvinyl butyrals, (CAB) cellulose acetate butyrates, (PVC) polyvinyl chlorides, (PVA) polyvinyl alcohols, and polyacrylates (acrylics). Pigments are widely available and are generally concentrated pigments dispersed in a dispersant. Pigments can be based on inorganic or organic materials, such as TiO2 for white inks. Additives are, for example, waxes, flow agents, and dispersants such as nitrocellulose.

[0124] As explained, the substrate having a crystalline triazine layer can be printed by methods known in the art, such as flexographic and gravure (or letterpress) printing. The following types of inks can be used: UV (ultraviolet) ink EB (Electron Beam) Ink · PVB (Polyvinyl Butyral) ink PVC (Polyvinyl Chloride) Ink · NC Ink Polyamide ink Polyurethane ink Water-based ink

[0125] UV inks are more preferred for flexo than gravure because of their viscosity: the ink may be too viscous for gravure, and therefore the ink would not be able to reach all the holes in the gravure plate.

[0126] UV curable screen printing inks are 100% solids systems, i.e., they contain essentially no solvents that must evaporate during the curing step. Curing occurs in a dryer by interaction of the ink components with a powerful UV light source. Solvent inks can have good coverage and are relatively inexpensive while having good durability. UV curable inks have the advantages of lack of VOCs, fast curing, and good color values. Some disadvantages are that the inks are not applicable to all substrates, cannot be printed on dark substrates, outdoor durability may be limited, the inks may not be well suited to high levels of wear, they tend to be less flexible, and are more sensitive to proper curing procedures.

[0127] EB inks are suitable as well. Both UV and EB systems typically use acrylate materials that cure by free radical polymerization (although other specialized chemistries are available). In the case of UV curing, UV light is absorbed by chemicals called photoinitiators. These materials convert the UV light into free radicals. The free radicals chemically react the acrylate materials to form acrylic polymers. In EB curing, photoinitiators are not needed. The energy of electrons is enough to directly polymerize the acrylate materials by opening acrylate bonds to form free radicals. These radicals then attack the remaining acrylate bonds until the reaction is complete. UV and EB cured inks, coatings and adhesives, when properly formulated, applied and cured, can meet the needs of many applications. EB chemistries more easily meet the needs of low odor, low off-taste applications. For thick films, opaque colors and through-film cure, EB is more suitable. UV / EB inks are very common in food packaging. UV inks are mostly used for label applications. The potential for harmful photoinitiator migration into the packaging limits the use of these types of inks.

[0128] PVB inks are well soluble in alcohols and partially soluble in esters, so they can be used well in both flexo and gravure. Inks based on PVB resins are widely used in retort applications due to their effective adhesion and thermal stability. The resin melts at about 110 °C (230 °F), but its molecules are stable up to about 250 °C (482 °F). PVB inks have several disadvantages. The most important is the incompatibility between the adhesion promoters used in PVB inks and nitrocellulose (NC). Printers using both NC and PVB inks must thoroughly clean the press and auxiliary equipment (hoses, ink pumps, ink containers, cylinders, etc.) between runs to avoid degradation of print quality.

[0129] PVC inks are less suitable for flexography and more suitable for gravure. PVC copolymers have long been used in inks for retort applications in Europe. These inks do not require adhesion promoters, work on flat and coated films, give excellent print results, and can be laminated with most adhesives. However, they have two drawbacks: they are only soluble in esters and ketones, making them unsuitable for flexography. The chlorine content also makes PVC inks difficult and expensive to dispose of, and high-temperature incineration is typically required.

[0130] Nitrocellulose inks (NC inks) are well suited for flexo and gravure. Nitrocellulose-based inks are the modern world standard for most flexo and gravure printing. However, NC is not suitable for retort applications because it degrades at high temperatures. These inks also typically require PU and PA co-binders. NC inks are also not preferred if the printed plastic is to be mechanically recycled because these inks result in discoloration at the high temperatures used in mechanical recycling. For such applications, PU-based inks are preferred.

[0131] Polyurethane (PU) binders can be used in both flexo and gravure. PU resins used today are primarily used as co-binders in NC, PVB and PVC systems.

[0132] PA binders are used in both flexo and gravure. Polyamide (PA) is the standard ink resin in North America, typically used with cellulose acetate butyrate (CAB) and PVB co-resins. PA inks offer good bond strength and excellent printability on many substrates. They are suitable for both flexo and gravure printing. They also require adhesion promoters that make PA inks incompatible with NC, so they share the limitations of PVB resins.

[0133] Color in ink systems is produced by using pigments or dyes. Typically, pigments are insoluble while dyes are soluble, although sometimes the terms are used interchangeably in the trade literature. Ink pigments are both inorganic and organic. Most white inks contain titanium dioxide as a pigment. Black colors are made with carbon black. Metallic pigments such as aluminum powder (aluminum bronze) and copper-zinc alloy powder (gold bronze) are used in novel silver and gold inks. Various inorganic pigments provide luminescent and pearlescent effects.

[0134] Suitable pigments or dyes for printing inks are, for example, diarylide yellow, benzimidazolone (yellow or red), diazopyrazolone (orange), naphthol (red), triarylcarbonium (red or blue) and Cu phthalocyanine (blue or green).

[0135] <Layering> In a preferred embodiment, the substrate coated with the steam-treated crystalline triazine layer is laminated between two other substrates, resulting in a so-called triple laminate.For example, a melamine-coated PET or OPA is laminated on one side with an OPP, which is optionally (reverse) printed, and on the other side with a sealant film (e.g., PE or CPP).Such a laminate structure has been found to have excellent barrier properties, especially at high humidity.

[0136] In a further preferred embodiment, a polypropylene-based film (either CPP or BOPP) is vacuum-coated with Al, AlOx or SiOx, followed by top-coating with a crystalline triazine layer, which is then treated with reactive compound vapor. A thin layer of EVOH, polyamide or lacquer may be applied (co-extruded) onto the BOPP prior to vacuum deposition. The AlOx coating on the BOPP and CPP can be combined with plasma-assisted deposition techniques known to those skilled in the art, such as hollow cathodic activated deposition (HAD). In a further preferred embodiment, the CPP film is vacuum-coated with AlOx using a HAD process, followed by coating with a crystalline triazine layer, which is then treated with reactive compound vapor. The AlOx-coated CPP with triazine topcoat is then laminated against a plain CPP, optionally reverse-printed. Such a structure is suitable for high-temperature applications such as retrort and sterilization.

[0137] As adhesives, solvent-based adhesives or solventless systems can be used. Both one-component and two-component adhesives, for example based on isocyanates as hardeners, can be used. In a preferred embodiment of the invention, the adhesive has good adhesion to the printed layer and has high strength. Advantageously, the adhesive has low expansion, high Tg, high crosslink density, and high inherent water barrier. Examples of adhesives include various types of UV-curable or heat-curable resins based on acrylates, water-based adhesives, epoxies, isocyanates (urethanes), and polyesters. Particularly preferred are polyester-based adhesives.

[0138] Extrusion lamination can also be used for lamination. Direct extrusion lamination is preferably performed at a relatively low temperature. Low temperatures save energy and improve barrier properties. Generally, extrusion lamination is performed at about 400°C to oxidize the extruded film to improve adhesion in other systems. Such high temperatures do not appear to be necessary, and therefore, preferably, extrusion lamination is performed at a temperature of about 350°C or less, even more preferably about 300°C or less, and most preferably about 200°C or more.

[0139] In a preferred embodiment of the present invention, the laminate with barrier properties is sealable. This can be achieved by laminating the steam-treated triazine-coated substrate against a sealant based on polyethylene (PE) or cast polypropylene (CPP). It is also possible that the carrier substrate on which the crystalline triazine compound is deposited is sealable on one side, such as sealable BOPP. It is also possible that the carrier substrate with the crystalline triazine compound and optionally the printed pattern is coated with a so-called hot seal or cold seal coating. The latter two examples are called monoweb applications.

[0140] In a preferred embodiment, an oriented PE film such as MDOPE or BOPE, optionally coated with a metal (oxide) layer, is coated with a steamed crystalline triazine layer, optionally reverse printed, and laminated with a sealant film such as PE. If a metal (oxide) layer is used, the oriented PE film may optionally be coated with a primer and / or an EVOH layer as described above.

[0141] In a preferred embodiment, a polypropylene film such as CPP or BOPP, optionally coated with a metal (oxide) layer, is coated with a steam-treated crystalline triazine layer, optionally reverse printed, and laminated with a sealant film such as CPP, BOPP or PE. If a metal (oxide) layer is used, the polypropylene film may optionally have a primer and / or an EVOH layer as described above.

[0142] In a preferred embodiment, a compostable film such as PHA or PLA, optionally coated with a metal (oxide) layer, is coated with a steam treated crystalline triazine layer, optionally reverse printed, and laminated with a compostable sealant film such as PLA.

[0143] In a further preferred embodiment, a substrate having a steam-treated crystalline triazine layer by itself can be sealed without additional sealant material, in which case the steam-treated crystalline triazine layer acts as a sealant layer.

[0144] Preferably, the multilayer substrate, when laminated with the adhesive and plastic film on the side of the steam-treated crystalline triazine compound, optionally including the printing layer, can exhibit a lamination strength of about 2.5 N / inch or more, more preferably about 3 N / inch or more, even more preferably about 3.5 N / inch or more, measured at 30 mm / min and 90 degrees on a tensile testing device. The upper limit of the lamination strength is not critical, but is generally about 20 N / inch or less. Lamination of the composite layer for testing is preferably performed with a suitable urethane adhesive and laminated with a thin polyethylene film of 30 to 100 μm or a CPP film having a similar thickness range. The exact thickness does not substantially affect the threshold value. As long as an effect will be observed, the test should be performed with 50 μm polyethylene. If the CPP determines the value, it is 50 μm CPP (cast polypropylene). The lamination strength of the two films can then be measured and the failure mode can be observed. A suitable adhesive is one that has an adhesive strength such that no failure mode is observed on the adhesive layer. The adhesion may be so high that the plastic film breaks, in which case the adhesion value can be taken as the value of the force required to break the film.

[0145] <Oxygen and water vapor barrier> Substrates coated with the triazine compounds according to the present invention have favorable barrier properties, such as low oxygen transmission rate (OTR) and low water vapor transmission rate (WVTR). Those skilled in the art will understand that the barrier properties are achieved by the crystalline triazine layer, unless the triazine is reacted. The reacted triazine forms an amorphous layer that does not have barrier properties by itself.

[0146] OTR is generally measured in an atmosphere of 20-30°C and 0%-85% RH. The preferred value generally depends on the substrate. When the substrate is biaxially oriented polypropylene (BOPP), the OTR is generally about 400 cc / m 2 24 hours or less, preferably about 300cc / m 2 24 hours or less, and even more preferably about 200cc / m 2-24h or less. In general, for BOPP, the OTR is about 5cc / m 2 - 24 hours or more, for example, about 20cc / m 2 If a layer of EVOH is co-extruded with BOPP, the OTR is about 10 cc / m 2 24 hours or less, preferably 1cc / m 2 -24h or less. In general, for EVOH co-extruded BOPP, the OTR is 0.01cc / m 2 24 hours or more, preferably 0.1cc / m 2 ·24h or more. The OTR can be measured with a suitable device, for example, the OXTRAN 2 / 20 from Modern Control Co. If the substrate is a PET film, the OTR is generally about 50cc / m 2 24 hours or less, preferably about 30cc / m 2 24 hours or less, and even more preferably about 10cc / m 2 -24 hours or less. In general, for PET, the OTR is about 0.1cc / m 2 24 hours or more, for example, about 0.3 or 1 cc / m 2 It can be more than 24 hours.

[0147] The water vapor transmission rate (WVTR) can be measured using a PERMATRAN 3 / 31 manufactured by Modern Control Co. at an atmosphere between 25-40°C and 50-90% RH. The preferred value depends on the substrate. For example, for BOPP, the WVTR is generally around 3 g / m 2 24h or less, preferably about 2g / m 2 24 hours or less, preferably about 1 g / m 2 24h or less. Generally, the vapor permeability is about 0.1g / m 2 24 hours or more, e.g. approx. 0.2g / m 2 For example, for PET, the WVTR is generally about 8g / m 2 24h or less, preferably about 7g / m 2 24 hours or less, preferably about 4g / m 2 -24h or less. In general, the WVTR is about 0.5g / m 2 24 hours or more, for example, about 2g / m2 -24 hours or more.

[0148] Preferably, the laminate also has an OTR and WVTR relative to other substrates that correspond to the values ​​given in the former two paragraphs. EXAMPLES

[0149] [Example 1] A 12 μm thick PET film (Melinex S) was vacuum coated with a successive layer of crystalline melamine. The coated roll was then placed in a roll-to-roll setup similar to the one shown in Figure 1. A solution of 1% formaldehyde at pH 7 was fed into a Certuss boiler type E27, which produced saturated steam at 0.4 to 1 mPa (absolute pressure). A 40x nozzle of type CD3 manufactured by Eurospray (https: / / www.euspray.com / en / home-page-en / ) was attached to a 60 cm steam pipe made of 304 stainless steel with a diameter of 42 mm and a wall thickness of 2 mm. The steam pipe was heated with an electric tracer to superheat the steam. The melamine-coated PET film was then exposed to various volumes of steam containing 1% formaldehyde at various rates. The distance between the nozzle outlet and the film was varied between 0.5 and 6 cm. The temperature of the superheated steam varied between 330 °C and 360 °C in the different experiments.

[0150] FIG. 6 shows photographic images of the effect of ethanol droplets on a melamine coating both before (a) and after (b) treatment with steam and formaldehyde. As can be seen without treatment, ethanol left white spots on the melamine coating, indicating that the layer was damaged by the action of ethanol. However, after treatment with steam containing formaldehyde, no white spots were observed, indicating that ethanol did not damage the melamine coating. The same results are observed when tests are performed with water droplets. The untreated melamine layer left white spots, while the treated melamine layer was not damaged.

[0151] Both the treated and untreated melamine coated PET films were then printed on a flexographic press with cyan and white inks, both manufactured by Huber Group. The ink types are Cyan 15470 Flexo and HS Xtreme White C3. Both inks contain ethanol as the primary solvent.

[0152] Figure 7 shows a tape test on the printed melamine coating both before (a) and after (b) steam with formaldehyde treatment. It is clearly shown that without treatment, the ink is removed after pulling the Scotch tape away at a 90° angle. After treatment with steam and formaldehyde, no ink is removed after pulling the Scotch tape away, indicating that the treatment dramatically improved the adhesion of the ink on the melamine coating.

[0153] From a defined section of the film (2 x 2 cm), the melamine layer was dissolved in 100 ml of ethanol and the melamine and reacted melamine were determined by standard HPLC using a UV detector. The various reacted melamine peaks were less than 2% by weight of the intensity of the melamine peak.

[0154] The film had oxygen barrier properties comparable to untreated (and unprinted) melamine-coated film. The OTR of the melamine-coated PET film treated with superheated steam was 2 cc / m2 both with and without the printed layer. 2 -It was 24 hours.

[0155] [Example 2] The PET film metallized with AlOx and coated with a crystalline melamine layer was treated similarly to the film of Example 1. The film thus obtained showed good adhesion of ethanol-based printing ink in the 90° adhesion test, similar to the film of Example 1. The film showed good oxygen barrier properties. The OTR of the melamine-coated PET-AlOx film treated with superheated steam was 1 cc / m2 both with and without the printing layer. 2 -It was 24 hours.

[0156] [Example 3] An evaporator was constructed with a U-tube having a length of 250 cm. Thus, the total length of the pipe is slightly more than 500 cm. The nozzles of the evaporator are installed over a length of 250 cm. Such a length is suitable for use with a slitter or vacuum coater with a width of 2.5 meters. The nozzles are flat spray nozzles with a spray angle of 110° and a hole diameter of 0.53 mm. The distance between the nozzles was 29 mm and the number of nozzles was 87. Two heating elements were installed on the pipe with a total operating power of 4.81 kw. The pipes were isolated with 15 mm of Rockwool PS 960.

[0157] The pipe could be heated to 650°C in less than 60 minutes without the presence of steam.

[0158] The pipe was connected to a steam generator with a thermal capacity of 20 kW delivering up to 28 kg / hr of steam. At a set temperature of 650°C for the evaporation pipe, the temperature of the pipe dropped to about 370°C within 60 minutes when continuously processing steam at 5 kg / hr (0.5 barg). The pipe temperature, and therefore also the steam temperature, dropped to below 300°C at 1.3 barg (steam volume). Superheated steam can therefore be processed in a stable and continuous manner.

[0159] The distance between the nozzle opening and the film surface was set to 10 mm, allowing the surface of the crystalline melamine layer to react uniformly. Water containing 0.5 wt% formaldehyde at pH 7.5 was used at 360°C and 5 kg / h to generate reactive steam, producing an alcohol-resistant AlOx-melamine coated polyester film.

Claims

1. A coated substrate comprising a substrate and a crystalline triazine layer, wherein the crystalline triazine layer comprises an alkylolated triazine, the layer being resistant to alcohol, and the coated substrate having oxygen barrier properties.

2. The coated substrate of claim 1 , wherein the crystalline triazine layer comprises an alkyl ether and / or alkylene bridged triazine.

3. 1. A process for preparing a coated substrate, comprising: a) providing a coated substrate having a crystalline triazine layer, the substrate optionally having a metal or metal oxide layer between the substrate and the triazine layer; b) applying vapors of reactive compounds capable of chemically reacting with the triazine layer such that the triazine is alkylolated and / or the triazine layer comprises alkyl ether and / or alkylene bridged triazines, such that the coated substrate has oxygen barrier properties and the triazine layer is resistant to alcohols. A process involving:

4. 4. The process of claim 3, wherein the reactive compound is an aldehyde, more preferably formaldehyde.

5. The process of claim 3 wherein the reactive compound is dissolved in water.

6. 4. The process according to claim 3, wherein said treatment of the crystalline triazine layer with vapors of a reactive compound is carried out in a continuous roll-to-roll process at atmospheric pressure, e.g. integrated in a slitting machine.

7. 4. The process of claim 3, wherein said treating of the crystalline triazine layer with vapors of a reactive compound is carried out in a continuous roll-to-roll process under reduced pressure immediately after deposition of the crystalline triazine layer.

8. 4. The process according to claim 3, wherein the reactive compound is applied in superheated steam, preferably sprayed onto the crystalline triazine layer at a distance of 0.5 cm to 10 cm.

9. The coated substrate of claim 1 , wherein the triazine is melamine.

10. The coated substrate of claim 1, wherein the substrate is a film having a thickness of 3 μm to 1 mm, preferably 5 μm to 100 μm.

11. 2. The coated substrate of claim 1, wherein the substrate is a plastic film, preferably BOPET, BOPP, MDOPE, BOPE, CPP, PLA, and PHA, optionally provided with an alumina, AlOx, or SiOx layer.

12. 2. The coated substrate of claim 1, wherein the substrate is a cellulose-based material such as paper, more preferably a clay-coated paper that is first pre-coated with a water-based or solvent-based lacquer, optionally provided with an alumina, AlOx or SiOx layer.

13. 10. The coated substrate of claim 1, wherein at least 90 mole percent of the triazine layer is unreacted and in crystalline form.

14. 10. Packaging, preferably food or non-food packaging, comprising the coated substrate of claim 1.

15. 4. A processing apparatus suitable for the process of claim 3 comprising a roll-to-roll transport system, further comprising: (i) optionally a vacuum chamber; (ii) optionally a metal (oxide) source; (iii) a heater for evaporating the crystalline triazine compound; and (iv) a vapor processing unit.

Images