Method for producing vacuum metallized paper

Abstract

The present invention relates to a method for producing a vacuum metallized paper, comprising: a) providing a paper substrate, the paper substrate comprising 0.3-60 kg / ton of a wetting agent, based on a total dry weight of the paper substrate, b) applying a precoat layer to the paper substrate, and c) applying a vacuum metallized layer to the precoat layer to provide a vacuum metallized paper. The present invention further relates to a vacuum metallized paper.

Description

[Technical field]

[0001] The present disclosure relates to vacuum metallized paper for use as a barrier layer in paper or paperboard based packaging laminates. More particularly, the present disclosure relates to vacuum metallized paper for paper or paperboard based packaging laminates having low oxygen transmission rate (OTR) and low water vapor transmission rate (WVTR). [Background technology]

[0002] Coating paper and paperboard with plastics is often used to combine the mechanical properties of paper or paperboard with the barrier and sealing properties of plastic films. Even in relatively small amounts, the addition of suitable plastic materials to paper or paperboard can provide the properties necessary to make the paper or paperboard suitable for many demanding applications, such as liquid or food packaging paperboard. In liquid or food packaging paperboard, polyolefin coatings are frequently used as liquid barrier layers, heat seal layers, and adhesives. However, such polymer-coated paperboard is difficult to recycle because it is difficult to separate the polymer from the fibers.

[0003] Also, in many cases, the water vapor barrier properties of polymer-coated paper or paperboard are still insufficient unless the coating layer is thick or a combination of different polymer coating layers is used. Therefore, to ensure high water vapor barrier properties, polymer-coated paper or paperboard is often combined with one or more layers of aluminum foil. However, the addition of polymer and aluminum foil significantly increases the cost, and the combination of the polymer coating layer and aluminum foil makes the material more difficult to recycle. Also, due to its large carbon footprint, it is desirable to replace aluminum foil in paper and paperboard-based packaging materials.

[0004] Aseptic packaging for shelf-stable products such as milk and juice is usually made from liquid or food packaging paperboard that contains a multi-layer paperboard-based substrate, an outermost layer of a heat-sealable polyolefin (e.g., polyethylene, PE), and an innermost layer of polyolefin and aluminum. The aluminum foil layers required to provide water vapor and oxygen barrier properties are usually incorporated between the layers of polyethylene, resulting in a PE / paperboard / PE / aluminum / PE structure.

[0005] Attempts have been made in the prior art to replace aluminium foil with more environmentally friendly and / or easier to recycle solutions, but so far without real success.

[0006] The solution presented in the prior art is to prepare a barrier layer by providing a vacuum-deposited organic or inorganic barrier coating layer on a high density paper or compact paper substrate. The vacuum-deposited barrier coating layer can, for example, comprise or consist of AlOx, Al2O3, or SiOx. The vacuum-deposited barrier layer is then laminated to a paper or paperboard base layer, providing the base layer with improved barrier properties.

[0007] A problem with the vacuum deposition technique is that the paper substrate that is vacuum deposited must have high smoothness and provide good adhesion to the vacuum deposited coating. For these reasons, it is common to use thin paper substrates with mineral or clay coatings, such as label stock, for vacuum deposition.

[0008] Another problem with the vacuum deposition technique is that the coating process is carried out under vacuum, which means that the substrate needs to be degassed. This means that the process is costly, but it also means that the degassing dries the paper substrate to a very low moisture content. This drying and subsequent re-wetting to ambient moisture levels changes the mechanical properties of the substrate. Not only does the drying negatively affect the curl and crack tendency and post-processability of the vacuum deposited substrate, but there is also a significant risk of hygroscopic expansion cracking of the thin and sensitive vacuum deposited layer when the paper substrate is re-wetted.

[0009] One solution to solve the problem of hygroscopic expansion is to increase the filler content. Fillers can reduce costs and improve the dimensional stability and optical properties of the substrate, but will have a negative effect on the barrier properties. Fillers lead to increased thermal conductivity, which can further increase the risk of defects such as curling, static charging, and surface size or coating cracking.

[0010] Thus, there remains a need for improved solutions to replace the combination of plastic films and aluminum foil in paper and paperboard based packaging materials while maintaining acceptable liquid, water vapor and oxygen barrier properties, and at the same time, there is a need to replace the combination of plastic films and aluminum foil with alternatives that facilitate repulping and recycling of post-consumer packaging materials. Summary of the Invention

[0011] It is an object of the present disclosure to provide an alternative to the combination of plastic film and aluminum foil that is commonly used as a barrier layer to provide water vapor barrier properties to packaging materials such as paperboard for liquid or food packaging.

[0012] It is a further object of the present disclosure to provide a barrier layer for paper or paperboard based packaging laminates, such as paperboard for liquid or food packaging, that provides good water vapor barrier properties even at higher relative humidities and temperatures.

[0013] A further object of the present disclosure is to provide a method for treating a pulmonary circulation disorder (PWD) having a PWD of 10 cc / m2 or less, as measured in accordance with ASTM standard F1927-98 at 50% relative humidity and 23° C. 2 The objective of the present invention is to provide a barrier layer having an oxygen transmission rate (OTR) of less than 24 / 40 hr.

[0014] A further object of the present disclosure is to provide a method for producing a cellulose ester resin having a viscosity of 10 g / m2 or less, as measured according to ASTM standard F1249-90 (relative humidity 50%, 23° C.). 2 The objective of the present invention is to provide a barrier layer having a water vapor transmission rate (WVTR) of less than 24 / 48 hours.

[0015] It is a further object of the present disclosure to provide a barrier layer for paper or paperboard based packaging laminates, such as paperboard for liquid or food packaging, which barrier layer facilitates repulping of the packaging laminate as compared to packaging laminates using traditional combinations of plastic films and aluminum foil.

[0016] The above objectives, as well as other objectives which will be realized by those skilled in the art in light of the present disclosure, are accomplished by various aspects of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The invention is based on the realization that very thin coating layers, typically having thicknesses in the range of 20-600 nm, more preferably 50-250 nm, formed by vacuum deposition processes such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), when applied to a suitable paper substrate, provide good oxygen and water vapor barrier properties, comparable to those of thick aluminum foil. The thickness of the vacuum deposited coating is typically at least an order of magnitude less than that of conventional foils, allowing the metal content of the product to be significantly reduced.

[0018] However, vacuum-deposited coatings directly onto the paper substrate to be coated, so-called direct vacuum deposition, or direct metallization, has proven problematic. More specifically, the degassing associated with the vacuum process means that the paper substrate is dried to a very low moisture content. This drying, and subsequent re-wetting to ambient moisture levels, alters the mechanical properties of the paper substrate. Not only does the drying have a negative effect on the paper substrate's tendency to crack, as well as its post-processability, but there is also a significant risk of cracking the thin and sensitive vacuum-deposited layer if the substrate is re-wetted.

[0019] The present invention is based on the recognition that these problems can be overcome by providing the paper substrate with an effective amount of a wetting agent. It has been found that a wetting agent provided in the bulk or on the surface of the paper substrate mitigates the adverse effects of over-drying during vacuum processing.

[0020] The low water content obtained after vacuum deposition can also lead to the risk of static buildup, which can cause curl and runnability problems. Wetting agents are believed to improve the electrostatic properties of the substrate, even by reducing triboelectric charging, reducing the need to rewet the dried substrate.

[0021] The risk of adding a wetting agent to a barrier layer is that pinholes or weak boundary layers can be expected to occur. It can also affect the crystallization of the polymer, which can cause problems when used in a barrier layer. However, the inventors have surprisingly discovered that vacuum metallized papers prepared with a substrate containing an effective amount of wetting agent also exhibit excellent oxygen and water vapor barrier properties.

[0022] According to a first aspect presented herein, there is provided a method for producing vacuum metallized paper, the method comprising the steps of: a) providing a paper substrate, the paper substrate comprising 0.3-60 kg / ton of a wetting agent based on a total dry weight of the paper substrate; b) applying a precoat layer to the paper substrate; and c) providing a vacuum metallized paper by applying a vacuum metallization layer to the precoat layer; Includes.

[0023] The method uses a paper substrate containing 0.3 to 60 kg / ton of wetting agent, based on the total dry weight of the paper substrate, which serves to prevent the paper substrate from over-drying during the vacuum treatment.

[0024] Wetting agents are hygroscopic substances used to keep products, materials, or formulations moist. Wetting agents are used in many products, including food, cosmetics, pharmaceuticals, and pesticides. Wetting agents may also be used as components of antistatic coatings for plastic materials.

[0025] Humectants attract and hold moisture from nearby air by absorption, drawing water to or under the surface of a product, material, or formulation. Humectants also help the wetting composition retain water more efficiently when it is subjected to drying. Common examples of humectants, i.e., humectants, include, but are not limited to, low molecular weight polyols, sugar alcohols, and metal salts. Particularly preferred are humectants that are listed as safe for direct or indirect food contact.

[0026] The paper substrate can be any paper substrate, but the method is particularly useful for substrates with lower basis weights, such as thin substrates, because such substrates are more easily overdried. In some embodiments, the paper substrate is between 20 and 150 g / m 2 in the range of 20 to 100 g / m 2 More preferably, it is in the range of 30 to 80 g / m 2 The composition has a basis weight in the range of 1000 to 2000 g.

[0027] Paper substrates subjected to vacuum deposition often contain mineral fillers, hi some embodiments, the paper substrate comprises mineral fillers in an amount of 1-30% by weight, based on the total dry weight of the paper substrate.

[0028] In some embodiments, the paper substrate is formed from a cellulose pulp composition having a Shopper-Rigler (SR) number of less than 35, preferably less than 30, as determined by ISO standard 5267-1.

[0029] In some embodiments, the paper substrate comprises less than 20% by weight, on a dry weight basis, of highly refined cellulose (HRC) or microfibrillated cellulose (MFC) having a Shopper-Rigler (SR) number of greater than 80, as determined by ISO standard 5267-1.

[0030] The paper substrate itself, prior to pre-coating and vacuum deposition, will typically have a high permeability to gases such as oxygen, air, and carbon dioxide. In some embodiments, the paper substrate has a Gurley Hill value of less than 5000 sec / 100 ml, preferably less than 2000 sec / 100 ml, and more preferably less than 1000 sec / 100 ml, measured according to ISO standard 5636-5.

[0031] The paper substrate itself, prior to pre-coating and vacuum deposition, will typically be highly permeable to water vapor. In some embodiments, the paper substrate has a permeability of 200 g / m2, measured according to ASTM standard F1249-90 (relative humidity 50%, 23° C.). 2 / Has a water vapor transmission rate (WVTR) of more than 24 hours.

[0032] The paper substrate itself, prior to pre-coating and vacuum deposition, will typically have low or no resistance to oil and grease penetration. In some embodiments, the paper substrate itself, prior to pre-coating and vacuum deposition, has a KIT value of less than 5, preferably less than 3, more preferably less than 1, as measured according to TAPPI standard T559.

[0033] The opacity of the paper substrate is typically greater than 80%, preferably greater than 85%, as determined according to ISO standard 2471.

[0034] The paper substrate may be surface sized. In some embodiments, the paper substrate is surface sized on one or both sides with a surface sizing composition, preferably comprising starch or a starch derivative, or a combination of starch or a starch derivative and microfibrillated cellulose.

[0035] In some embodiments, the surface sizing composition comprises a starch that is not chemically modified.

[0036] In some embodiments, the surface sizing composition has a basis weight of 0.2 to 10 g / m per side on a dry weight basis. 2 , preferably 0.4 to 8 g / m 2 , more preferably 0.8 to 5 g / m 2 It is.

[0037] In some embodiments, the paper substrate comprises 0.5-50 kg / ton, preferably 1-40 kg / ton, more preferably 5-30 kg / ton of wetting agent based on the total dry weight of the paper substrate.

[0038] In some embodiments, the humectant is selected from the group consisting of low molecular weight polyols, sugar alcohols, metal salts, and combinations thereof.

[0039] In some embodiments, the humectant is a sugar alcohol, preferably sorbitol.

[0040] In some embodiments, the wetting agent is a metal salt, preferably a divalent or trivalent metal salt. In some embodiments, the wetting agent is a metal salt selected from the group consisting of calcium chloride, calcium acetate, magnesium acetate, and calcium magnesium acetate. In some embodiments, the wetting agent is calcium chloride. In some embodiments, the wetting agent is a metal salt selected from the group consisting of calcium acetate, magnesium acetate, and calcium magnesium acetate.

[0041] In some embodiments, the humectant is present in the bulk of the paper substrate, or on the surface of the paper substrate, or both.

[0042] In some embodiments, the wetting agent is added to the furnish during the papermaking process such that the wetting agent is dispersed within the bulk of the paper substrate.

[0043] In some embodiments, the wetting agent is added to the surface of the paper substrate as part of a surface size or surface treatment composition that is applied to the substrate after or during formation of the substrate, for example in the form of a coating. Thus, in some embodiments, the wetting agent is present on the surface of the paper substrate, preferably as part of a surface size composition. In some embodiments, the paper substrate comprises a wetting agent on the surface of the paper substrate facing the precoat layer. In some embodiments, the paper substrate comprises a wetting agent in a coating, surface size, or surface treatment composition on the surface of the paper substrate facing the precoat layer. In some embodiments, the paper substrate comprises a wetting agent in a coating, surface size, or surface treatment composition on the surface of the paper substrate facing the precoat layer, further comprising starch, preferably a chemically unmodified starch.

[0044] In some embodiments, the paper substrate comprises a wetting agent, preferably further comprising starch, in a coating, surface size, or surface treatment composition, on the surface of the paper substrate on both sides of the paper substrate. The coating, surface size, or surface treatment composition comprising a wetting agent can improve the printability of the surface not facing the precoat layer, especially when the wetting agent is a metal salt.

[0045] Wetting agents may also be present in both the bulk and on the surface of the paper substrate, for example, they may be added to both the furnish and the coating, surface size, or surface treatment composition, or the wetting agent added to the coating, surface size, or surface treatment composition may also penetrate the bulk of the paper substrate.

[0046] A precoat layer is applied to the paper substrate, which is optionally surface-sized. The precoat layer makes the surface of the paper substrate smoother and less porous before the vacuum deposition layer is applied. The precoat layer can also improve the adhesion of the vacuum deposition layer. Preferably, the precoat layer can also improve the gas, water vapor, and / or liquid barrier properties of the coated substrate.

[0047] The precoat layer will also provide a barrier against migration of low molecular weight substances from the paper substrate. This may be particularly useful in the method according to the present disclosure, since some wetting agents are volatile or prone to migration and therefore may cause deposits in the vacuum deposition machine. Some wetting agents may reduce adhesion to the vacuum deposition layer, and some wetting agents may also be corrosive. Without being bound by any scientific theory, it is believed that the polymer precoat layer can provide not only good adhesion to the vacuum deposition layer, but also a good barrier against migration of the wetting agent.

[0048] The precoat layer can be applied by any suitable method known in the art, for example, it can be applied as a solution or dispersion in an aqueous or organic solvent carrier using liquid coating methods known in the art, in melt form using extrusion coating, or in the form of a solid film by lamination.

[0049] The precoat layer is preferably formed by a liquid film coating process, i.e. in the form of a solution or dispersion that is spread into a thin, uniform layer on the substrate when applied and then dried. The liquid phase of the solution or dispersion is preferably water or an aqueous solution, but organic solvents or mixtures of water or aqueous solutions with organic solvents can also be used. One or more polymers can be present in the solution or dispersion in dissolved form or in the form of polymer particles such as latex. The precoat layer can be applied by contact coating or non-contact coating methods. Examples of useful coating methods include, but are not limited to, rod coating, curtain coating, film press coating, cast coating, transfer coating, size press coating, flexographic coating, gate roll coating, twin roll HSM coating, blade coating (e.g., short-time blade coating), jet applicator coating, spray coating, gravure coating, or reverse gravure coating.

[0050] To minimize the risk of pinholes in the precoat layer, the precoat layer may be applied in at least two different coating steps, preferably with drying of the coated film between each step. The air content of the coating solution or dispersion is preferably less than 1%.

[0051] In some embodiments, at least one precoat layer is applied in foamed form. Foamed coatings are advantageous because they can form films with higher solids content and lower water content compared to non-foamed coatings. The low water content of foamed coatings also reduces rewetting problems of the paper substrate. The foam can be formed using polymeric or non-polymeric foaming agents. Examples of polymeric foaming agents include PVOH, hydrophobically modified starch, and hydrophobically modified ethyl hydroxyethyl cellulose.

[0052] Typically, the precoat layer comprises one or more polymers. The precoat layer may consist solely of one or more polymers or may further comprise other additives to facilitate the coating process or to improve the properties of the precoat layer.

[0053] In some embodiments, the precoat layer comprises at least 50% by weight of a polymer or polymer mixture on a dry weight basis.

[0054] In some embodiments, the precoat layer comprises a polymer selected from the group consisting of polyvinyl alcohol (PVOH), polyurethane, polysaccharides, and combinations thereof, preferably PVOH. The polysaccharide may be a natural polysaccharide or a chemically modified polysaccharide, for example, a chemically modified cellulose such as carboxymethylcellulose (CMC).

[0055] In some embodiments, the precoat layer comprises at least 50% by weight of a water-soluble polymer or mixture of water-soluble polymers based on dry weight. The water-soluble polymer of the precoat layer is soluble in cold water for a given time, or in hot water, for example at temperatures below or above 100°C. The water-soluble polymer acts as an adhesive for the vacuum-deposited layer, and also facilitates the separation of the vacuum-deposited layer from any additional plastic layers applied over the precoat layer or vacuum-deposited layer during repulping. In some embodiments, the water-soluble polymer is selected from the group consisting of polyvinyl alcohol (PVOH), chemically modified cellulose, starch, alginate, and hemicellulose. In some embodiments, the water-soluble polymer is selected from the group consisting of polyvinyl alcohol (PVOH), carboxymethyl cellulose (CMC), starch, alginate, and hemicellulose, preferably PVOH.

[0056] In some embodiments, the precoat layer comprises at least 50% by weight PVOH, and preferably at least 70% by weight PVOH, based on the total dry weight of the precoat layer.

[0057] In some embodiments, the PVOH has a degree of hydrolysis in the range of 80-99 mol%, preferably in the range of 85-99 mol%. In some embodiments, the PVOH has an ash content of less than 4 wt%, preferably less than 3 wt%, more preferably less than 2.5 wt%. In some embodiments, the PVOH is washed PVOH.

[0058] In some embodiments, the precoat layer also includes a humectant. If the precoat layer includes multiple layers, the humectant may preferably be included in one of the layers. In some embodiments, the precoat layer also includes 1-30 wt. %, preferably 1-20 wt. %, more preferably 1-10 wt. %, of a humectant, based on the dry weight of the precoat layer. The humectant in the precoat layer may be the same or different as in the paper substrate.

[0059] In some embodiments, the precoat layer further comprises a crosslinking agent capable of crosslinking the water-soluble polymer. The crosslinking agent can be advantageously applied together with the water-soluble polymer and then activated, for example, by heat or radiation, when the precoat layer is in contact with the vacuum-deposited layer. Crosslinking improves the water vapor barrier properties of the precoat layer. Suitable crosslinking agents include, but are not limited to, polyfunctional organic acids or aldehydes, such as citric acid, glyoxal, and glutaraldehyde. In some embodiments, the crosslinking agent is an organic acid, more preferably citric acid. The concentration of the crosslinking agent can be, for example, 1 to 20% by weight, preferably 1 to 15% by weight, based on the dry weight of the precoat layer.

[0060] In some embodiments, the precoat layer comprises PVOH and citric acid. Crosslinking the PVOH with citric acid improves the water vapor barrier properties of the precoat layer. In addition, it has been found that crosslinking the PVOH in contact with the vacuum deposited layer with citric acid further improves the adhesion of the vacuum deposited layer and the overall water vapor barrier properties of the vacuum deposited paper.

[0061] In some embodiments, the precoat layer comprises one or more additional polymers in a total amount of 1-50% by weight based on dry weight. The additional polymer(s) can provide crosslinking and / or further improve adhesion to the vacuum deposited layer. Suitable additional polymer(s) include, but are not limited to, polyvinylpyrrolidone, polyvinylamide, polyvinylethyleneimine, polyacrylamide, cationic polyacrylamide, polyurethane, and derivatives thereof. Other suitable additional polymer(s) include latexes, such as styrene acrylate latex (SA latex), styrene butadiene latex (SB latex), polyvinyl acetate (PVAc), styrene butadiene acrylonitrile (SBN), polyvinylidene dichloride (PVDC), and hybrid polymer emulsions, such as grafted starch.

[0062] In some embodiments, the basis weight of the precoat layer is from 1 to 20 g / m2 on a dry weight basis. 2 in the range of 2 to 15 g / m 2 More preferably, the range is 3 to 12 g / m 2 Without being bound by any theory, it is believed that basis weights according to these ranges can provide not only good adhesion to the vacuum deposition layer, but also a good barrier against migration of wetting agents from the paper substrate during the vacuum deposition process.

[0063] After the precoat layer is applied, a vacuum metallized layer is applied to the precoat layer to obtain the vacuum metallized paper. The wetting agent serves to prevent the paper substrate from drying out too much during the vacuum process.

[0064] Vacuum deposition refers to a set of processes used to deposit layers of metals, metal oxides, and other inorganic and organic compositions onto solid surfaces, typically atom by atom or molecule by molecule. Multiple layers of the same or different materials can be combined. Processes can be further specified based on the vapor source, with physical vapor deposition (PVD) using liquid or solid sources and chemical vapor deposition (CVD) using chemical vapors.

[0065] Vacuum deposition typically results in a very thin coating. In some embodiments, the vacuum deposited layer has a thickness in the range of 10-600 nm, preferably in the range of 10-250 nm, more preferably in the range of 50-250 nm. This can be compared to conventional aluminum foils used in packaging laminates, which typically have a thickness in the range of about 3-12 μm.

[0066] In some embodiments, the vacuum deposited layer is applied to the precoat layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0067] The vacuum deposited layer may be inorganic or organic, hi some embodiments, the vacuum deposited layer is an inorganic vacuum deposited layer, such as a metal, metal oxide, or ceramic vacuum deposited layer.

[0068] In some embodiments, the vacuum deposited layer comprises a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

[0069] One preferred type of vacuum deposition is a physical vapor deposition (PVD) coating of aluminum metal, which is often used for its barrier properties, especially water vapor barrier properties. Such coatings consist essentially of aluminum metal and can typically have a thickness of 50 to 250 nm, although thicknesses less than 50 nm are also useful and may be preferred in some embodiments. The thickness of the vacuum deposited layer represents less than 1% of the aluminum metal material typically present in aluminum foil of conventional thickness for packaging, i.e., 6.3 μm. Thus, in some embodiments, the vacuum deposited layer comprises aluminum.

[0070] The thickness of the vacuum deposited layer can also be characterized by the optical density of the layer. In some embodiments, the vacuum deposited layer has an optical density greater than 1.8, preferably greater than 2.0, greater than 2.5, greater than 2.7, or greater than 3.0.

[0071] Vacuum deposited layers of aluminum oxide, also known as AlOx coatings, can provide similar barrier properties as aluminum metal coatings, but with the added advantage that thin AlOx coatings are transparent to visible light.

[0072] In some embodiments, the vacuum deposited layer is an organic vacuum deposited layer, hi some embodiments, the vacuum deposited layer comprises carbon.

[0073] The organic vacuum deposition can be, for example, a vacuum deposited carbon layer, such as a diamond-like carbon (DLC) layer formed from carbon or an organic compound.

[0074] In some embodiments, the vacuum deposited layer has a thickness in the range of 10 to 600 nm, preferably in the range of 10 to 250 nm, and more preferably in the range of 50 to 250 nm.

[0075] In some more specific embodiments, the wetting agent is a metal salt and the precoat layer comprises at least 50% by weight PVOH, based on the total dry weight of the precoat layer.

[0076] In some more specific embodiments, the wetting agent is a metal salt, the precoat layer comprises at least 50% by weight PVOH, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises a metal or metal oxide.

[0077] In some more specific embodiments, the wetting agent is a calcium salt, the precoat layer comprises at least 50% by weight PVOH, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises aluminum.

[0078] In some more specific embodiments, the wetting agent is a metal salt and the precoat layer comprises at least 50% by weight CMC, based on the total dry weight of the precoat layer.

[0079] In some more specific embodiments, the wetting agent is a metal salt, the precoat layer comprises at least 50% by weight CMC, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises a metal or metal oxide.

[0080] In some more specific embodiments, the wetting agent is a calcium salt, the precoat layer comprises at least 50% by weight CMC, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises aluminum.

[0081] In some of the more specific embodiments, the paper substrate comprises a wetting agent on the surface of the paper substrate facing the precoat layer. In some embodiments, the paper substrate comprises a wetting agent in a coating, surface size, or surface treatment composition on the surface of the paper substrate facing the precoat layer. In some embodiments, the paper substrate comprises a wetting agent in a coating, surface size, or surface treatment composition on the surface of the paper substrate facing the precoat layer, further comprising starch, preferably a chemically unmodified starch.

[0082] In some of the more specific embodiments, the precoat layer further comprises a crosslinking agent capable of crosslinking PVOH or CMC. The crosslinking agent can advantageously be applied together with PVOH or CMC and then activated, for example by heat or radiation, when the precoat layer is in contact with the vacuum deposited layer. Crosslinking improves the water vapor barrier properties of the precoat layer. Suitable crosslinking agents include, but are not limited to, polyfunctional organic acids or aldehydes, such as citric acid, glyoxal, and glutaraldehyde. In some embodiments, the crosslinking agent is an organic acid, more preferably citric acid. The concentration of the crosslinking agent can be, for example, 1-20% by weight, preferably 1-15% by weight, based on the dry weight of the precoat layer. In some embodiments, the precoat layer comprises PVOH or CMC and an organic acid, more preferably citric acid.

[0083] Coating a paper substrate with a precoat layer and a vacuum metallized layer significantly improves the oxygen and water vapor barrier properties of the vacuum metallized paper compared to an uncoated paper substrate.

[0084] In some embodiments, the resulting vacuum metallized paper has a viscosity of 10 cc / m2 or less as measured according to ASTM standard F1927-98 at 50% relative humidity and 23° C. 2 / Less than 24 hours, preferably 5cc / m 2 / 24 hours or less, preferably 1cc / m 2 / Has an oxygen transmission rate (OTR) of less than 24 hours.

[0085] In some embodiments, the resulting vacuum metallized paper has a viscosity of 10 g / m2 as measured according to ASTM standard F1249-90 (relative humidity 50%, 23° C.). 2 / less than 24 hours, preferably 5g / m 2 / 24 hours or less, preferably 1g / m 2 / Has a water vapor transmission rate (WVTR) of less than 24 hours.

[0086] In addition to providing good oxygen and water vapor barrier properties, the vacuum metallized paper of the present invention can also form a good barrier to other gases, as well as fragrances and odors.

[0087] The resulting vacuum metallized paper typically has significantly better oil and grease barrier properties compared to the paper substrate itself, and in some embodiments, the resulting vacuum metallized paper has a KIT value of at least 8, preferably at least 10, and more preferably at least 12, as measured according to TAPPI standard T559.

[0088] The method according to the first aspect described herein allows for the production of improved vacuum metallized paper. The paper comprises 0.3-60 kg / ton, based on the total dry weight of the paper substrate, of a wetting agent that protects the paper substrate from excessive drying. Excessive drying can result, for example, from subjecting the vacuum metallized paper to high temperatures (temperatures above 100° C.), for example during hot lamination, extrusion coating, or heat sealing processes. Not only does drying adversely affect the curl and crack tendency and processability of the vacuum metallized paper, but there is also a significant risk of cracking the thin and sensitive vacuum metallized layer due to moisture expansion as the paper substrate is subsequently re-wetted.

[0089] Thus, according to a second aspect presented herein, paper base material, A precoat layer, and Vacuum deposition layer Including, a precoat layer is disposed between and in contact with the paper substrate and the vacuum deposition layer; and The paper substrate comprises 0.3 to 60 kg / ton of a wetting agent based on the total dry weight of the paper substrate; A vacuum metallized paper is provided.

[0090] In some embodiments, the paper substrate is surface sized on one or both sides with a surface sizing composition, preferably comprising starch or a starch derivative, or a combination of starch or a starch derivative and microfibrillated cellulose.

[0091] In some embodiments, the surface sizing composition comprises a starch that is not chemically modified.

[0092] In some embodiments, the surface sizing composition has a basis weight of 0.2 to 10 g / m per side. 2 , preferably 0.4 to 8 g / m 2 , more preferably 0.8 to 5 g / m 2 It is.

[0093] In some embodiments, the humectant is selected from the group consisting of low molecular weight polyols, sugar alcohols, metal salts, and combinations thereof.

[0094] In some embodiments, the humectant is present in the bulk of the paper substrate, or on the surface of the paper substrate, or both.

[0095] In some embodiments, the wetting agent is present on the surface of the paper substrate, preferably as part of a surface sizing composition.

[0096] The vacuum metallized paper according to the second aspect described herein and its components including the paper substrate, the precoat layer, and the vacuum metallized layer may be further defined as described with reference to the first aspect.

[0097] In some more specific embodiments, the wetting agent is a metal salt and the precoat layer comprises at least 50% by weight PVOH, based on the total dry weight of the precoat layer.

[0098] In some more specific embodiments, the wetting agent is a metal salt, the precoat layer comprises at least 50% by weight PVOH, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises a metal or metal oxide.

[0099] In some more specific embodiments, the wetting agent is a calcium salt, the precoat layer comprises at least 50% by weight PVOH, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises aluminum.

[0100] In some more specific embodiments, the wetting agent is a metal salt and the precoat layer comprises at least 50% by weight CMC, based on the total dry weight of the precoat layer.

[0101] In some more specific embodiments, the wetting agent is a metal salt, the precoat layer comprises at least 50% by weight CMC, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises a metal or metal oxide.

[0102] In some more specific embodiments, the wetting agent is a calcium salt, the precoat layer comprises at least 50% by weight CMC, based on the total dry weight of the precoat layer, and the vacuum deposited layer comprises aluminum.

[0103] In some of the more specific embodiments, the paper substrate comprises a wetting agent on the surface of the paper substrate facing the precoat layer. In some embodiments, the paper substrate comprises a wetting agent in a coating, surface size, or surface treatment composition on the surface of the paper substrate facing the precoat layer. In some embodiments, the paper substrate comprises a wetting agent in a coating, surface size, or surface treatment composition on the surface of the paper substrate facing the precoat layer, further comprising starch, preferably a chemically unmodified starch.

[0104] In some of the more specific embodiments, the precoat layer is crosslinked by a crosslinking agent capable of crosslinking PVOH or CMC. The crosslinking agent can be advantageously applied together with PVOH or CMC and then activated, for example by heat or radiation, when the precoat layer is in contact with the vacuum deposited layer. Crosslinking improves the water vapor barrier properties of the precoat layer. Suitable crosslinking agents include, but are not limited to, polyfunctional organic acids or aldehydes, such as citric acid, glyoxal, and glutaraldehyde. In some embodiments, the crosslinking agent is an organic acid, more preferably citric acid. The concentration of the crosslinking agent can be, for example, 1-20% by weight, preferably 1-15% by weight, based on the dry weight of the precoat layer. In some embodiments, the precoat layer comprises PVOH or CMC crosslinked by an organic acid, more preferably citric acid.

[0105] According to a third aspect presented herein, there is provided a method for producing a paper or paperboard based packaging laminate, said method comprising: i) providing a paper or paperboard base layer; and ii) laminating the vacuum metallized paper according to the second aspect or the vacuum metallized paper produced according to the first aspect to a paper or paperboard base layer to obtain a paper or paperboard based packaging laminate. Includes.

[0106] Paper generally refers to a material manufactured from wood pulp or other fibrous substances containing cellulose fibers into thin sheets and used for writing, drawing, or printing, or as a packaging material.

[0107] Paperboard generally refers to a strong, thick paper or cardboard containing cellulose fibers used for boxes and other types of packaging. Paperboard can be produced in a variety of thicknesses, either bleached or unbleached, coated or uncoated, depending on the end-use requirements. Paperboard can be a single-ply material, or a multi-ply material consisting of two or more plies. A common type of multi-ply paperboard consists of a low-density middle ply (sometimes called a "bulk ply") sandwiched between two high-density outer plies. The low-density middle ply is typically 750 kg / m 3 less than 700, preferably less than 650, less than 600, less than 550, less than 500, less than 450, less than 400, or less than 350 kg / m 3 The dense outer layer typically has a density at least 100 kg / m2 higher than the density of the intermediate layer. 3 Higher, preferably at least 200 kg / m higher than the density of the intermediate layer 3 It has high density.

[0108] A paper or paperboard-based packaging laminate is a packaging material formed primarily from paperboard. The paper or paperboard base layer can be made from pulp, including pulp from virgin fibers, such as mechanical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from shredded paper or recycled paper. In addition to paper or paperboard, a paper or paperboard-based packaging laminate can include additional layers or coatings designed to improve the performance and / or appearance of the packaging laminate.

[0109] A paper or paperboard based packaging laminate typically has a first outermost surface intended to function as the exterior or print surface and a second outermost surface intended to function as the interior surface of a packaging container. One side of the paper or paperboard base layer comprising the vacuum metallized paper of the present invention is preferably intended to function as the interior surface of a packaging container.

[0110] In some embodiments, the paper or paperboard base layer has a thickness of at least 100 g / m 2 In some embodiments, the paper or paperboard base layer has a basis weight of at least 150 g / m 2 , 200g / m2 , 250g / m 2 , 300g / m 2 , 350g / m 2 , or 400 g / m 2 The paper or paperboard base layer preferably has a basis weight of 1000 g / m 2 , 800g / m 2 , or 600 g / m 2 Unless otherwise stated, basis weight is determined in accordance with ISO standard 536.

[0111] In some embodiments, the paper or paperboard base layer has a viscosity of 700 kg / m 3 Less than 600 kg / m 3 Unless otherwise stated, density is determined in accordance with ISO standard 534.

[0112] The paper or paperboard base layer can be a single ply paperboard or multiple ply paperboard. In some embodiments, the paper or paperboard base layer is multiple ply paperboard. In some embodiments, the paper or paperboard base layer is multiple ply paperboard consisting of two or more plies. In some embodiments, the paper or paperboard base layer is multiple ply paperboard consisting of three or more plies. In some embodiments, the paper or paperboard base layer is multiple ply paperboard consisting of a lower density middle layer sandwiched between two higher density outer layers.

[0113] In some embodiments, the paper or paperboard base layer is a foamed paperboard. In some embodiments where the paper or paperboard base layer is a multi-layer paperboard, at least one of the layers, preferably the middle layer, is foamed.

[0114] According to a fourth aspect presented herein there is provided a paper or paperboard based packaging laminate obtainable by the method according to the third aspect.

[0115] Paper or paperboard based packaging laminates can provide an alternative to traditional materials using aluminum foil layers and can be more easily repulped and recycled. In some embodiments, the paper or paperboard based packaging laminates have a rejection rate of less than 30%, preferably less than 20%, more preferably less than 10% according to PTS RH 021 / 97.

[0116] The paper or paperboard based packaging laminate may further be provided with an outermost polymer layer on one or both sides. The outermost polymer layer preferably provides liquid barrier properties and mechanical protection to the paper or paperboard based packaging laminate surface. The outermost polymer layer is preferably also heat sealable.

[0117] In some embodiments, a paper or paperboard based packaging laminate comprises a first outermost polymer layer, preferably a polyethylene layer, disposed on a paper or paperboard substrate.

[0118] In some embodiments, the paper or paperboard based packaging laminate further comprises a second outermost polymer layer, preferably a polyethylene layer, disposed on the vacuum deposited layer.

[0119] The outermost polymer layer may of course hinder repulpability, but may still be necessary or desirable in some applications. Additional polymer layers may be applied, for example, by extrusion coating, lamination of a film, or dispersion coating.

[0120] The outermost polymer layer may comprise any of the thermoplastic polymers commonly used for protective and / or heat-sealable layers of paper or paperboard-based packaging laminates in general, or polymers used for paperboards for liquid or food packaging in particular. Examples include polyethylene (PE), polyethylene terephthalate (PET), polyethylene furanoate (PEF), polypropylene (PP), polyhydroxyalkanoate (PHA), polylactic acid (PLA), polyglycolic acid (PGA), starch, and cellulose. Polyethylene, especially low density polyethylene (LDPE) and high density polyethylene (HDPE), are the most common and versatile polymers used for paperboards for liquid or food packaging. The polymers used are preferably made from renewable materials.

[0121] Thermoplastic polymers are useful because they can be easily processed by extrusion coating techniques to form very thin, homogeneous films with good liquid barrier properties. In some embodiments, the additional polymer layer comprises polypropylene or polyethylene. In a preferred embodiment, the outermost polymer layer comprises polyethylene, more preferably LDPE or HDPE.

[0122] In some embodiments, the outermost polymer layer is formed by extrusion coating a polymer onto the surface of a paper or paperboard substrate or laminate. Extrusion coating is a process in which molten plastic material is applied to a substrate to form a very thin, smooth, uniform layer. The coating can be formed of the extruded plastic itself, or the molten plastic can be used as an adhesive to laminate a solid plastic film onto the substrate. Common plastic resins used in extrusion coating include polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET).

[0123] The basis weight of each of the outermost polymer layers is preferably 50 g / m 2To achieve a continuous, substantially defect-free membrane, the basis weight of the outermost polymer layer is typically at least 8 g / m 2 , preferably at least 12 g / m 2 In some embodiments, the basis weight of the outermost polymer layer is between 8 and 50 g / m 2 in the range of 12 to 50 g / m 2 The range is.

[0124] Generally, the products, polymers, materials, layers, and processes are described in terms of "comprising" various components or steps, but the products, polymers, materials, layers, and processes can also be said to "consist essentially of" or "consist of" the various components and steps.

[0125] While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various modifications can be made and equivalents can be substituted for elements of the invention without departing from the scope of the invention. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. EXAMPLES

[0126] Example 1 (Comparative) One-side mineral coated 44 gsm flexible wrapping paper was used as the paper substrate. The paper substrate had an ash content of 7% by weight and a fiber mix consisting of 30% mechanical pulp and 70% chemical kraft pulp. The details of the paper substrate are given in Table I.

[0127] The paper was supercalendered and the mineral coated side of the paper substrate was precoated off-line with a PVOH solution using a lab coater as detailed in Table II and dried. The dried PVOH coated surface was then vacuum deposited with aluminum metal in a commercial reel-to-reel vacuum deposition apparatus to coating weights corresponding to optical densities of 3.5 and 2.5, as detailed in Tables III and IV, respectively.

[0128] The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the paper substrate itself were too high to measure, indicating poor barrier properties.

[0129] After PVOH precoating, the OTR decreased but the WVTR remained at a high level, and after vacuum deposition, the OTR increased but the WVTR decreased.

[0130] Example 2 (Comparative) Uncoated 65 gsm paper with a fiber mix consisting of 20% chemical pulp and 80% mechanical pulp (TMP) and without fillers was used as the paper substrate, the details of which are given in Table I.

[0131] The paper was soft calendered and then a sheet of paper substrate was pre-coated offline with a PVOH solution using a lab coater as detailed in Table II and dried. The dried PVOH coated surface was then vacuum deposited with aluminum as described in Example 1 to a coating weight corresponding to an optical density of 3.5 as detailed in Table III.

[0132] The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the paper substrate itself were too high to measure, indicating poor barrier properties. The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the pre-coated substrate and the vacuum metallized paper were also too high to measure.

[0133] Example 3 (Comparative) Uncoated 45 gsm paper with a fiber mix consisting of 20% chemical pulp and 80% mechanical pulp (TMP) and without fillers was used as the paper substrate, the details of which are given in Table I.

[0134] The paper was soft calendered and then a sheet of paper substrate was pre-coated offline with a PVOH solution using a lab coater as detailed in Table II and dried. The dried PVOH coated surface was then vacuum deposited with aluminum as described in Example 1 to a coating weight corresponding to an optical density of 3.5 as detailed in Table III.

[0135] The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the paper substrate itself were too high to measure.

[0136] After PVOH pre-coating, the OTR and WVTR remained at high levels, however, after vacuum deposition, the WVTR decreased but the OTR remained at high levels.

[0137] Example 4 Surface-sized 90 gsm wood-free paper containing 30% softwood, 40% hardwood, and 30% wearwood by weight, and 20% ash was used as the paper substrate. The paper was surface-sized with native starch and calcium chloride until the coating weight was approximately 2-3 gsm per side. The surface size contained ca20 kg calcium chloride per tonne of paper on a dry weight basis. The paper substrate had an opacity of 90-91%, determined according to ISO standard 2471. Details of the paper substrate are given in Table I.

[0138] The paper was soft calendered and then a sheet of paper substrate was pre-coated offline with a PVOH solution using a lab coater as detailed in Table II and dried. The dried PVOH-coated surface was then vacuum deposited with aluminum as described in Example 1 to a coating weight corresponding to an optical density of 3.5 and 2.5 as detailed in Tables III and IV, respectively.

[0139] The oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the paper substrate itself were too high to measure, indicating poor barrier properties.

[0140] After PVOH pre-coating, an obvious improvement in barrier property was detected. After vacuum deposition, both the OTR and WVTR properties decreased to low levels, indicating good oxygen and water vapor barrier properties.

[0141] The vacuum metallized paper had a reject rate of 0.6% according to PTS RH 021 / 97. TIFF2025510763000001.tif99170 TIFF2025510763000002.tif55170 TIFF2025510763000003.tif44170 TIFF2025510763000004.tif39170

[0142] Unless otherwise specified, the properties or parameters discussed in this disclosure are determined according to the following standard methods: TIFF2025510763000005.tif69170

[0143] OTR and WVTR were measured at 23°C and 50% RH, with some exceptions at 80% RH, as detailed in Tables I-IV. Mocon equipment was used. The sides of the samples with the precoat layer and the vacuum deposited layer faced the oxygen or water vapor stream. Samples were measured in duplicate, simultaneously, on the same equipment.

Claims

1. 1. A method for producing vacuum metallized paper, comprising: a) providing a paper substrate, the paper substrate comprising 0.3 to 60 kg / ton of a wetting agent, based on the total dry weight of the paper substrate; b) applying a precoat layer to the paper substrate; and c) Applying a vacuum metallization layer to the precoat layer to obtain vacuum metallization paper A method comprising:

2. The paper base material is 20 to 150 g / m ２ in the range of 20 to 100 g / m ２ in the range of 30 to 80 g / m ２ The method of claim 1 having a basis weight in the range of

3. The method according to claim 1 or 2, wherein the paper substrate comprises mineral filler in an amount of 1 to 30% by weight, based on the total dry weight of the paper substrate.

4. 3. The method according to claim 1 or 2, wherein the paper substrate has a Gurley-Hill value of less than 5000 sec / 100 ml, preferably less than 2000 sec / 100 ml, more preferably less than 1000 sec / 100 ml, measured according to ISO standard 5636-5.

5. The paper substrate has a density of 200 g / m2 as measured in accordance with ASTM standard F1249-90 (relative humidity 50%, 23°C). ２ 3. The method of claim 1 or 2, wherein the composition has a water vapor transmission rate (WVTR) of greater than 24 hours.

6. 3. The method according to claim 1 or 2, wherein the paper substrate is surface sized on one or both sides with a surface sizing composition, preferably comprising starch or a starch derivative, or a combination of starch or a starch derivative and microfibrillated cellulose.

7. 7. The method of claim 6, wherein the surface sizing composition comprises a chemically unmodified starch.

8. The surface sizing composition has a basis weight of 0.2 to 10 g / m per side based on dry weight. ２ , preferably 0.4 to 8 g / m ２ , more preferably 0.8 to 5 g / m ２ The method of claim 6, wherein

9. 3. The method according to claim 1 or 2, wherein the paper substrate comprises 0.5 to 50 kg / tonne, preferably 1 to 40 kg / tonne, more preferably 5 to 30 kg / tonne of wetting agent, based on the total dry weight of the paper substrate.

10. 3. The method of claim 1 or 2, wherein the humectant is selected from the group consisting of low molecular weight polyols, sugar alcohols, metal salts, and combinations thereof.

11. 3. The method according to claim 1 or 2, wherein the humectant is a sugar alcohol, preferably sorbitol.

12. 3. The method of claim 1 or 2, wherein the wetting agent is a metal salt, preferably a divalent or trivalent metal salt, more preferably a metal salt selected from the group consisting of calcium chloride, calcium acetate, magnesium acetate, and calcium magnesium acetate.

13. 3. The method of claim 1 or 2, wherein the wetting agent is present in the bulk of the paper substrate, or on the surface of the paper substrate, or both.

14. 3. The method of claim 1 or 2, wherein the wetting agent is present on the surface of the paper substrate, preferably as part of a surface sizing composition.

15. 3. The method of claim 1 or 2, wherein the precoat layer comprises a polymer selected from the group consisting of polyvinyl alcohol (PVOH), polyurethane, polysaccharides, and combinations thereof, preferably PVOH.

16. 3. The method of claim 1 or 2, wherein the precoat layer comprises at least 50 wt. % PVOH, preferably at least 70 wt. % PVOH, based on the total dry weight of the precoat layer.

17. 16. The method according to claim 15, wherein the PVOH has a degree of hydrolysis in the range of 80 to 99 mol %, preferably in the range of 85 to 99 mol %.

18. The basis weight of the precoat layer is 1 to 20 g / m2 on a dry weight basis. ２ in the range of 2 to 15 g / m ２ in the range of 3 to 12 g / m ２ The method according to claim 1 or 2, wherein the range is

19. 3. The method of claim 1 or 2, wherein the vacuum deposited layer is applied to the precoat layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

20. 3. The method of claim 1 or 2, wherein the vacuum deposited layer is an inorganic vacuum deposited layer, such as a vacuum deposited layer of a metal, metal oxide, or ceramic.

21. 3. The method of claim 1 or 2, wherein the vacuum deposited layer comprises a metal or metal oxide selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

22. 3. The method according to claim 1, wherein the vacuum-deposited layer is an organic vacuum-deposited layer.

23. 3. The method of claim 1 or 2, wherein the vacuum deposited layer comprises carbon.

24. The method according to claim 1 or 2, wherein the vacuum deposited layer has a thickness in the range of 10 to 600 nm, preferably in the range of 10 to 250 nm, more preferably in the range of 50 to 250 nm.

25. The obtained vacuum metallized paper had a viscosity of 10 cc / m when measured at 50% relative humidity and 23°C in accordance with ASTM standard F1927-98. ２ / less than 24 hours, preferably 5cc / m ２ / 24 hours or less, more preferably 1 cc / m ２ 3. The method of claim 1 or 2, wherein the composition has an oxygen transmission rate (OTR) of less than 24 hours.

26. The obtained vacuum metallized paper had a viscosity of 10 g / m when measured in accordance with ASTM standard F1249-90 at a relative humidity of 50% and 23°C. ２ / less than 24 hours, preferably 5 g / m ２ / 24 hours or less, more preferably 1 g / m ２ 3. The method of claim 1 or 2, wherein the composition has a water vapor transmission rate (WVTR) of less than 24 hours.

27. A vacuum metallized paper, paper base material, a precoat layer, and Vacuum deposition layer Including, a precoat layer disposed between and in contact with the paper substrate and the vacuum deposited layer; and the paper substrate comprises 0.3 to 60 kg / ton of wetting agent, based on the total dry weight of the paper substrate; Vacuum metallized paper.

28. 28. Vacuum metallized paper according to claim 27, wherein the paper substrate is surface sized on one or both sides with a surface sizing composition, preferably comprising starch or a starch derivative, or a combination of starch or a starch derivative and microfibrillated cellulose.

29. 30. The vacuum metallized paper of claim 28, wherein the surface sizing composition comprises a chemically unmodified starch.

30. The surface sizing composition has a basis weight of 0.2 to 10 g / m per side. ２ , preferably 0.4 to 8 g / m ２ , more preferably 0.8 to 5 g / m ２ 30. The vacuum metallized paper according to claim 28 or 29, wherein

31. 30. The vacuum metallized paper of any one of claims 27 to 29, wherein the humectant is selected from the group consisting of low molecular weight polyols, sugar alcohols, metal salts, and combinations thereof.

32. 30. Vacuum metallized paper according to any one of claims 27 to 29, wherein the humectant is present in the bulk of the paper substrate, or on the surface of the paper substrate, or both.

33. 30. Vacuum metallized paper according to any one of claims 27 to 29, wherein a wetting agent is present on the surface of the paper substrate, preferably as part of a surface sizing composition.