Barrier paper with high oxygen barrier properties

Abstract

The present invention relates to a barrier paper comprising a paper substrate and a carboxymethyl cellulose coating layer formed on a surface of the paper substrate, in which the paper substrate is cellulose paper, and the carboxymethyl cellulose coating layer comprises 80 wt% to 100 wt% of carboxymethyl cellulose based on dry weight.

Description

Technical Field

[0001] The present invention relates to a barrier paper which can be used as an oxygen barrier layer in a packaging material for oxygen-sensitive items. Further aspects of the present invention include a method for producing the oxygen barrier paper and the use of the oxygen barrier paper as a packaging material for oxygen-sensitive foods. Background Art

[0002] Packaging materials cause a large amount of waste, and many countries are currently trying to reduce the waste by replacing fuel-based plastic packaging materials with fully biodegradable, compostable and bio-derived packaging materials. Such biodegradable packaging materials must meet various conditions, depending on the end use. For example, when used as food packaging, they must be safe for food contact, and when used as packaging for life science and diagnostic devices, they must meet strict safety requirements. In particular, when used as packaging material for oxygen-sensitive products, sufficient gas barrier properties of the packaging material are necessary.

[0003] Cellulose paper has been used as a biodegradable base paper material for producing sustainable packaging materials. An example of such a cellulose paper is pure vegetable parchment (GVP) made from 100% cellulose. GVP is known to be a biodegradable packaging material with moisture vapor barrier properties and inherent grease barrier properties.

[0004] In order to achieve the desired oxygen barrier properties, cellulose paper is either produced with a very high density (such as GVP with a high parchment level) or an additional oxygen barrier layer is laminated thereto.

[0005] EP 3 819 426 A1 describes parchment paper having a very high level of parchmentization.

[0006] However, when using GVP with very high levels of sheepskinization, such as PureBarrier TM Materials (by Ahlstrom There are some limitations in terms of mechanical properties when converting very highly parchmented GVP grades (oxygen barrier parchment materials produced). Although such very highly parchmented GVP grades are very interesting because they have inherent oxygen barrier properties and they are completely bio-sourced (made from 100% cellulose) and certified home compostable, very highly parchmented GVP grades are more brittle and fragile due to the high degree of conversion, which makes them relatively sensitive to wrinkles and tears. This may limit the use of highly parchmented GVP grades in some packaging applications, especially those that require the sheet to be formed into a desired shape to contain food products. They may also be somewhat difficult to handle in converting equipment running at higher web loads.

[0007] Furthermore, very highly sheepskinned GVP grades require very specific manufacturing process conditions to provide 3 / m 2 / day oxygen transmission rate (OTR) value. Therefore, the production rate is quite low, and due to the inefficiency, its production cost is significantly more expensive than the production of standard GVP grades. The waste level in the production of highly sheepskinned GVP grades may also be significantly higher than the production of other GVP grades.

[0008] WO 2018 / 197676 A1 describes a multilayer article comprising a vegetable parchment carrier and an oxygen barrier layer containing polyvinyl alcohol (PVOH), and US 2019 / 0078261 A1 describes a laminate comprising an acid-resistant paper substrate and a coating containing cellulose nanofibers laminated thereon.

[0009] When acid resistant papers (such as GVP) are coated with oxygen barrier coatings such as PVOH, polyvinylidene chloride (PVdC), the OTR properties obtained are not always satisfactory, either due to the sensitivity of the coating to the conditions of use (PVOH is sensitive to moisture) or because of environmental issues (PVdC). Barrier properties can be imparted when an acid resistant paper substrate (such as GVP) is laminated with an oxygen barrier layer such as a polymer layer (for example, a polyolefin extrusion coating or a cellulose nanofiber coating), but these methods involve additional processing stages and have a negative impact on the life cycle of the product. The production of cellulose nanofiber coatings further increases the production costs of the barrier paper coated therewith. In addition, lamination using polyolefin lamination or other non-fully degradable coating materials has a very negative impact on the sustainability of the packaging material (lower bio-sourced content and no active end-of-life scheme).

[0010] Furthermore, vapor deposition can also be used to cover cellulose base paper materials. Although metallization or other vapor phase processes allow excellent barrier properties to be imparted with very little raw material, these processes are very expensive and are usually done under specific vacuum conditions, which requires an external conversion step. Moreover, if a paper substrate is used, an additional coating step is required before metallization to improve the surface roughness. In fact, without such additional coating, the paper substrate may swell due to moisture and the metal coating may crack and lose its barrier properties. In addition to having a strong impact on the packaging costs, the life cycle of these processes remains to be discussed.

[0011] In summary, to obtain the desired oxygen barrier properties, specialized process conditions or the use of non-biodegradable materials are required.

[0012] Therefore, the object of the present invention is to provide an improved biodegradable packaging material having very good oxygen barrier properties and excellent mechanical properties. Another object of the present invention is to provide a biodegradable packaging material that is easy to manufacture in an energy-saving and waste-reducing manner and at low cost.

[0013] The present invention has better mechanical properties compared to very highly parchmented GVP grades and can be produced in a more efficient manner due to the cellulose paper used as the paper substrate having a lower level of processing (e.g. lower parchmented grade) and the carboxymethyl cellulose coating formed thereon. The present invention provides a fully compostable material with better oxygen barrier properties compared to existing multi-layer products comprising a cellulose base paper and an oxygen barrier coating, since the carboxymethyl cellulose coating comprises 80 to 100 wt. % carboxymethyl cellulose on a dry weight basis. Summary of the invention

[0014] The present invention solves the problems of the prior art in the following ways.

[0015] In a first aspect, the present invention relates to a barrier paper comprising a paper substrate and a carboxymethyl cellulose coating formed on a surface of the substrate, wherein the paper substrate is cellulose paper, and the carboxymethyl cellulose coating comprises 80 wt % to 100 wt % of carboxymethyl cellulose based on dry weight.

[0016] It has been found that applying a carboxymethyl cellulose coating comprising 80 to 100 wt. % carboxymethyl cellulose to a cellulose paper solves the problems of the prior art by providing a biodegradable barrier paper having excellent oxygen barrier properties while exhibiting advantageous mechanical properties.

[0017] In a second aspect, the present invention relates to a method for producing a barrier paper, the method comprising applying a coating mixture comprising 80 wt% to 100 wt% carboxymethyl cellulose on a dry weight basis to a surface of a paper substrate to form a carboxymethyl cellulose coating, wherein the paper substrate is cellulose paper.

[0018] Thus, an additional advantage of the present invention is that the barrier papers described herein may be produced in a sustainable and more efficient manner and may reduce waste and production costs compared to prior art procedures.

[0019] In a third aspect, the present invention relates to the use of the barrier paper described herein as a packaging material for oxygen sensitive articles. DETAILED DESCRIPTION

[0020] The present invention relates to a barrier paper comprising a paper substrate and a carboxymethyl cellulose coating layer formed on a surface of the substrate, wherein the paper substrate is cellulose paper, and the carboxymethyl cellulose coating layer comprises 80 wt % to 100 wt % of carboxymethyl cellulose based on dry weight.

[0021] In the context of the present invention, the following definitions and test methods apply.

[0022] The term "cellulose paper" refers to a sheet material comprising mainly cellulose. That is, the cellulose content in the cellulose paper as described herein is generally at least 50% by weight, preferably at least 80% by weight, and most preferably 100% by weight. Examples of cellulose paper are parchment paper, glassine paper, tracking paper, greaseproof paper, and supercalendered paper.

[0023] The term "parchment" or "pure vegetable parchment (GVP)" refers to a material comprising primarily cellulose that has been subjected to a parchmenting process. Cellulosic materials are derived from artificial sources, such as regenerated cellulose fibers or films, or from natural sources, such as fibers or pulps from woody or non-woody plants. In the parchmenting process, a cellulose paper is treated with a gelling agent comprising, for example, sulfuric acid, under conditions that limit the reaction time between the gelling agent and the cellulose to control the dissolution, hydrolysis, and degradation of the cellulose. The treated paper is then washed thoroughly to remove the gelling agent and then dried. The bath chemicals partially dissolve or gel the cellulose in the paper. When the bath chemicals are diluted by washing the treated paper, the dissolved cellulose subsequently precipitates. This process is called parchmenting or parchmentizing, and results in a very hard, strong, smooth paper whose appearance somewhat resembles that of real parchment. Because paper treated in this manner has a tendency to become brittle and wrinkle when dried, it is sometimes treated with a plasticizer such as glycerol, glucose, or sorbitol. Vulcanized fiber is a related product made by treating cellulose paper with a gelling agent containing, for example, zinc chloride.

[0024] The terms "glass paper", "tracing paper", "greaseproof paper" and "supercalendered paper" refer to papers obtained primarily by combining two processes: refining and supercalendering. Glass paper is usually produced by first producing paper from refined cellulose pulp and subjecting it to a series of moisturizing and supercalendering steps in order to achieve a very dense paper with a smooth surface and a certain transparency. Greaseproof paper is usually produced from highly refined cellulose pulp, which causes extensive fibrillation of the cellulose fibers and the formation of fines, and subsequently using highly refined pulp, which can optionally undergo a calendering step. In the context of the present invention, greaseproof paper should not be confused with greaseproof paper that has been chemically treated, for example with waxes and fluorinated compounds. Tracing paper is a paper produced by highly refined cellulose pulp and / or supercalendering of base paper. In order to enhance its translucency, tracing paper can be treated with oil. Supercalendered paper is paper that has been subjected to a supercalendering process. Supercalendered paper can be produced using moderately refined cellulose pulp.

[0025] The term "high-density paper material" refers to a paper material having a density of at least 800 kg / m 3 The density of cellulose paper can be calculated by changing the grammage (g / m 2 ) divided by its thickness (caliper) (μm). Usually, the grammage of high-density paper material is 25g / m 2 Up to 200g / m 2 Those skilled in the art can easily adjust the thickness parameters of the high-density paper to match the density range described above according to the selected basis weight.

[0026] The expression "biodegradable" is usually defined in accordance with standard EN 13432. When applied to a material or a product, the expression "biodegradable" means that the material or the entire product will biodegrade and disintegrate. "Biodegradation" means that the chemical structure or material breaks down under the action of microorganisms, while "disintegration" means that the material or the product made therefrom will physically break down into small, visually indistinguishable fragments at the end of a typical composting cycle.

[0027] The "oxygen transmission rate (OTR)" of a material refers to the oxygen transmission rate (OTR) of a material through a specified area (m2) of the material during one day at an atmospheric pressure of 1.013 bar (1 atm), a temperature of 23°C and a relative humidity of 50%. 2 ) of oxygen volume (cm 3 ). Oxygen Transmission Rate (OTR) (cm 3 / m 2 / day) is measured according to ASTM D 3985 and ASTM F 1927. Unless otherwise stated, the OTR described herein is measured on an OX-TRAN 2 / 22 device (supplier: MOCON), which complies with the ASTM D3985 standard. The OTR of a material is a measure of the oxygen barrier properties of the material and indicates the gas barrier level. In other words, the lower the OTR of a material, the smaller the amount of gas transmitted through the material, which makes the material provide a high barrier to gases, especially oxygen.

[0028] As described above, a first aspect of the present invention relates to a barrier paper comprising a paper substrate and a carboxymethyl cellulose coating formed on a surface of the substrate, wherein the paper substrate is cellulose paper, and the carboxymethyl cellulose coating comprises 80 wt% to 100 wt% of carboxymethyl cellulose based on dry weight. The inventors surprisingly found that when cellulose paper is coated with a carboxymethyl cellulose (CMC) coating composed of at least 80 wt% of CMC, the barrier paper has high oxygen barrier properties and simultaneously has excellent mechanical properties.

[0029] An important aspect of the present invention is the discovery that forming a CMC coating on the surface of a cellulose paper substrate can significantly improve its oxygen barrier properties.

[0030] When a high-density paper material is used as the paper substrate, a synergistic effect between the base paper material and the CMC coating on oxygen barrier properties can be observed. That is, if the paper structure has a high density (enoughly closed), the CMC coating will significantly improve the OTR of the barrier paper formed. CMC is a cellulose derivative to which chemical side groups (carboxymethyl groups) carrying electrostatic charges are added. These modifications make the affinity of CMC for the cellulose of high-density paper materials higher than the affinity for other uncharged polymers. Due to this affinity, the coverage of the cellulose base paper material is good, and the cohesive strength between CMC and the cellulose of the base paper material is high. When a high-density paper material is used, even the formation of a thin CMC layer is sufficient to achieve excellent oxygen barrier properties. The higher the density of the paper material, the smaller the thickness of the CMC coating required to obtain a barrier paper with excellent OTR.

[0031] Another key aspect of the present invention is the discovery that cellulose paper having insufficient oxygen barrier properties before coating with a CMC coating can be suitably used as a substrate for barrier paper. Specifically, when a cellulose paper having very low oxygen barrier properties is used as a substrate, excellent oxygen barrier properties can be obtained by coating this cellulose paper with a CMC coating comprising at least 80 wt. % CMC.

[0032] Therefore, the barrier paper described herein can be advantageously used as a barrier layer for constructing highly air- and moisture-impermeable packaging materials, especially as packaging materials for oxygen-sensitive items. In addition, since the barrier paper described herein has excellent mechanical properties in terms of tear strength, wet burst strength, and dry burst strength, it can also be used as a reinforcing layer for the construction of packaging materials, especially for packaging with a predetermined shape.

[0033] The present invention provides a fully biodegradable, compostable and bio-derived product, which consists essentially of cellulose and acts as an oxygen barrier as well as a reinforcing layer. Since cellulose paper with a lower level of processing can be used as base paper, the energy required during the production process can be saved and the waste produced during production can be reduced, making the production process more efficient and cheaper. Another advantage of the present invention is the possibility of using recyclable cellulose paper (such as glassine, greaseproof paper or super calendered paper) as base paper.

[0034] Paper substrate

[0035] The cellulose paper used as the paper substrate may be a paper having a density of 800 kg / m 3 or higher, preferably 850kg / m 3 When such high-density paper materials are used, favorable oxygen barrier properties can already be obtained when a thinner CMC coating is applied thereto.

[0036] The cellulose paper preferably comprises at least 50 wt. %, and more preferably at least 80 wt. % cellulose. Most advantageously, the cellulose paper consists of 100 wt. % cellulose, making the cellulose paper completely bio-derived and completely biodegradable / compostable. Thus, the cellulose paper preferably contains no more than 5 wt. % of non-compostable material or material of uncertain compostability, to meet the requirements of the EN 13432 standard. Most preferably, any additives added to the cellulose paper are compostable.

[0037] The cellulose paper is preferably selected from parchment paper, glassine paper, tracking paper, oil-proof paper and supercalendered paper. When any of these cellulose papers is used as the paper substrate, due to the selection of a low basis weight (e.g. 30-45 g / m 2 ), a barrier paper having both excellent mechanical strength and excellent oxygen barrier properties as well as high flexibility can be obtained.

[0038] In a preferred embodiment, the cellulose paper is parchment. The parchment may be pure vegetable parchment (GVP) made essentially of short fiber pulp. The OTR of the parchment is preferably less than 50,000 cm 3 / m 2 / day, preferably less than 10,000 cm 3 / m 2 / day, as measured at 23°C and 50% relative humidity. When using OTR over 50,000cm 3 / m 2 / day parchment paper as the substrate, the resulting barrier paper may not have a 10cm 3 / m 2 / day or less. The lower the OTR of the parchment paper, the higher its parchmentization level. For example, OTR is about 5000-100,000cm 3 / m 2 / day parchment with low parchment level (e.g. Ahlstrom Sulpack manufactured by ), OTR is about 150-3000cm 3 / m 2 / day parchment with medium parchment level (e.g. Ahlstrom Sulflex manufactured by ), and OTR is 10cm 3 / m 2 / day or less parchment with very high parchmentization levels (e.g. Ahlstrom PureBarrier manufactured by ).

[0039] Very highly parchmented papers (such as PureBarrier) can show less than 10cm 3 / m 2 / day. However, when the parchment level is increased, the mechanical properties of the parchment paper decrease, because very high parchment levels cause the paper to be more brittle and sensitive to cracking. By combining a parchment paper with a medium parchment level with a thin CMC coating, the decrease in mechanical properties can be avoided and a barrier paper with significantly better mechanical properties (for example in terms of tear resistance) as well as with excellent oxygen barrier properties can be obtained.

[0040] The basis weight of the cellulose paper used as the paper substrate can be selected according to the composition of the fibers and / or filaments and the intended end use. In some embodiments, the basis weight of the cellulose paper on a dry basis can be 200 g / m 2 or less, preferably 30g / m 2 Up to 130g / m 2 , more preferably 45g / m 2 Up to 85g / m 2 Glassine, tracing, greaseproof and supercalendered papers are particularly useful in selecting very low basis weights, such as 30-45 g / m 2When the basis weight of the cellulose paper is within these ranges, the barrier paper obtained therefrom has excellent mechanical properties and provides excellent barrier properties while maintaining a good level of flexibility suitable for flexible packaging or tray applications.

[0041] From the viewpoint of achieving excellent mechanical reinforcement characteristics and good flexibility, the average thickness of cellulose paper used as the paper substrate is generally 30 to 200 μm, preferably 35 to 95 μm, even more preferably 40 to 80 μm.

[0042] Carboxymethyl cellulose coating

[0043] The CMC coating formed on the surface of the paper substrate contains 80 wt % to 100 wt % CMC based on dry weight. Although CMC is generally used as a thickener additive for coating compositions, the inventors surprisingly found that CMC is useful when applied to cellulose paper as a coating, resulting in high OTR properties. When a CMC coating with a high content of CMC (i.e., at least 80 wt %) is applied, a barrier paper with excellent oxygen barrier properties can be obtained. When the coating is mainly or even completely made of CMC, very high OTR properties can be obtained. The reason lies in the synergistic effect of the CMC contained in the CMC coating with the cellulose paper material, which makes the obtained barrier paper have a lower OTR. Since the carboxymethyl side groups in CMC carry electrostatic charges, CMC has a high affinity with the cellulose of high-density paper materials, which makes the cellulose base paper material have excellent coverage, and there is a high cohesive strength between CMC and the cellulose of the base paper material. The formation of a continuous and dense CMC coating allows the formation of a good oxygen barrier.

[0044] This synergistic effect is particularly evident when using high-density paper materials as the paper substrate. The reasons for this are as follows. High-density paper has few or no cracks and pores, thus enabling the CMC coating to fill these cracks more effectively. In addition, when using high-density paper with almost no porosity, the CMC does not absorb deeply into the material, but forms good surface coverage at low amounts, resulting in a barrier paper with excellent OTR properties.

[0045] The CMC coating is preferably coated with 1.5 g / m 2 or more, more preferably 1.5 g / m 2 Up to 10g / m 2 When at least 1.5 g / m 2 When CMC coating is applied, it can provide excellent oxygen barrier properties (i.e., <10cm 3 / m 2The amount of CMC coating applied to the surface of the paper substrate depends on the density of the paper substrate. For example, if a very dense cellulose paper (e.g. parchment paper with a high parchmentization grade) is used, a relatively small amount of CMC coating forming a thinner CMC coating on the surface of the dense cellulose paper is sufficient to obtain a barrier paper with an excellent OTR. On the other hand, if the density of the cellulose paper is relatively low, from the viewpoint of obtaining a barrier paper with an excellent OTR, it is preferred to apply a higher amount of CMC coating to its surface, thereby forming a thicker CMC coating.

[0046] The Mw of CMC can be adjusted by both the raw material selection and the conditions of its manufacturing process.The Mw of CMC is preferably 100,000 g / mol to 750,000 g / mol, preferably 100,000 g / mol to 400,000 g / mol.

[0047] The Mw of CMC has a critical influence on the coating composition. When the Mw is below 100,000 g / mol, the viscosity of CMC is low, which makes its application easier but reduces the oxygen barrier properties of the resulting barrier paper. When the Mw is above 750,000 g / mol, the viscosity of CMC is high, which makes its application on the surface of the substrate problematic, while there is no gain in OTR properties. Therefore, from the point of view of selecting the best compromise between rheology and OTR properties, it is preferred to use CMC with a Mw in the range mentioned above.

[0048] The OTR properties of the barrier paper can be further enhanced by adding a softener such as glycerol and / or a salt such as calcium chloride, sodium chloride or potassium chloride to the CMC coating composition.

[0049] The addition of salts such as calcium chloride, sodium chloride and potassium chloride helps to reduce the viscosity of the CMC coating composition by restricting the conformation of the CMC molecules in water, thereby reducing the interactions between the molecules that affect the viscosity. Therefore, the addition of salts enables the use of CMC with a higher Mw, which further enhances the oxygen barrier properties of the resulting barrier paper.

[0050] Adding glycerin, on the other hand, has a different effect. First, adding glycerin, which has a lower viscosity than the diluted CMC, tends to further dilute the composition and reduce viscosity. Second, and more importantly, glycerin or other softeners can soften the barrier layer, making it less strong and brittle. Because of this effect, the coating is less likely to develop small defects during manufacturing or conversion, resulting in a better and more reliable barrier effect.

[0051] The CMC coating composition preferably includes 20 wt% or less glycerol on a dry weight basis. More preferably, the composition includes 5 wt% to 18 wt% glycerol. Even more preferably, the composition includes 10 wt% to 15 wt% glycerol. When such amounts of glycerol are included, the OTR of the obtained barrier paper can be further reduced.

[0052] The CMC coating composition preferably includes salts such as calcium chloride, sodium chloride and / or potassium chloride. It is preferred that these salts are included in the CMC coating composition in an amount of 5 wt% or less relative to the CMC coating composition. When salts are included (preferably in said amounts), the OTR of the obtained barrier paper can be further reduced.

[0053] Barrier paper

[0054] The barrier paper according to the present invention comprises cellulose paper as a paper substrate and a CMC coating layer comprising 80 to 100 wt % of CMC formed on the surface of the paper substrate. Since the CMC coating layer comprises at least 80 wt % of CMC applied to the surface of the cellulose paper substrate, a biodegradable barrier paper having excellent oxygen barrier properties and simultaneously exhibiting favorable mechanical properties is provided.

[0055] The OTR of the barrier paper is preferably 0.10 cm due to the CMC coating applied thereto. 3 / m 2 / day to 100.0cm 3 / m 2 / day, more preferably 0.10cm 3 / m 2 / day to 10.0cm 3 / m 2 / sky.

[0056] According to the configuration of the barrier paper of the present invention, sufficient oxygen barrier properties can be obtained even when cellulose paper having a relatively low processing level and concomitant low gas barrier properties is used as the paper substrate.

[0057] The tear strength of the barrier papers described herein depends on the type of cellulose paper used as paper substrate.The tear strength of barrier papers is measured according to ISO 1974:2012.

[0058] The dry bursting strength and wet bursting strength of the barrier papers described herein depend on the type of cellulose paper used as paper substrate and the selected basis weight. The wet bursting strength is measured according to ISO 3689 and the dry bursting strength is measured according to ISO2758.

[0059] Method for producing barrier paper

[0060] In a second aspect, the present invention relates to a method for producing a barrier paper, the method comprising applying a coating mixture comprising 80 wt% to 100 wt% carboxymethyl cellulose on a dry weight basis to a surface of a paper substrate to form a carboxymethyl cellulose coating, wherein the paper substrate is cellulose paper.

[0061] The cellulose paper used as the paper substrate preferably has a density of 800 kg / m 3 or higher, preferably 850kg / m 3 or higher high density paper materials. When using high density paper materials, a thin CMC coating can be applied thereto and still obtain favorable oxygen barrier properties. In addition, by applying only a thin CMC coating, application problems that occur with CMC coating compositions having higher viscosities can be reduced. Therefore, when using high density paper materials, the production of barrier paper is easier and more cost-effective.

[0062] As previously described, the CMC coating (including optional additives such as glycerol and / or salts such as calcium chloride, sodium chloride and / or potassium chloride) and the amounts thereof may be used in the method of producing the barrier paper according to the present invention.

[0063] The step of applying the CMC coating onto the surface of the cellulose paper substrate does not require the application of pressure and can be performed without pressure or by applying a pressure of, for example, 300 kPa to 2000 kPa. Any kind of coating method can be used, such as curtain coating, rod coating or gravure coating. When no pressure is applied, the CMC coating can be applied, for example, by using a spray coater. When pressure is applied, the CMC coating can be applied, for example, by using a size press process or a pressure impregnation process. By applying the CMC coating using pressure, the OTR properties of the obtained barrier layer can be further enhanced. When a size press is used, it is preferred to apply a CMC coating CMC with a higher viscosity to achieve sufficient grammage / desired basis weight.

[0064] A subsequent calendering step may also be optionally included. Calendering can help to homogenize the thickness of the barrier paper and increase its density, thereby improving the oxygen barrier properties. Optionally, a calendering step may also be performed before the coating step to improve the surface properties of the substrate.

[0065] Packaging Materials

[0066] In a third aspect, the present invention relates to the use of the barrier paper described herein as packaging material for oxygen sensitive products.

[0067] The packaging material is not particularly limited, and the barrier paper can be used as a packaging material for preserving oxygen-sensitive items (e.g., oxygen-sensitive foods or oxygen-sensitive life science and diagnostic devices). The packaging material for oxygen-sensitive foods can, for example, be selected from the group consisting of: butter packaging, beverage containers, coffee capsules, coffee cakes, chocolate packaging, and biscuit packaging. Preferably, the packaging material is used for the construction of coffee capsules, more preferably for the cover of coffee capsules. The packaging material for oxygen-sensitive life science and diagnostic devices can, for example, be selected from the group consisting of: test kit packaging, biological sample collection and preservation card packaging, laboratory test filter packaging, test pad packaging, and DNA / RNA extraction medium packaging.

[0068] The barrier paper may be used together with an optional additional layer in the packaging material. That is, the packaging material may be a multilayer product comprising the barrier paper as a first material layer and at least one additional material layer, wherein the at least one additional material layer is laminated on the surface of the barrier paper. The additional layer is not particularly limited and may be appropriately selected according to the desired additional properties that the packaging material should complement. The additional layer is preferably selected from the group consisting of: a water vapor barrier layer, an aroma barrier layer, a waterproof layer, a heat sealable layer, a grease resistant layer, a finishing varnish layer and a printable layer.

[0069] Example

[0070] The properties of the cellulose paper used in this example and the barrier paper prepared in this example were measured according to the following methods.

[0071] The oxygen transmission rate (OTR) has been measured according to ASTM D 3985 on an OTR measuring device "OX-TRAN 2 / 22" (produced by MOCON).

[0072] The following raw materials were used in this example.

[0073] Paper substrate :

[0074] Table 1 shows the paper substrates used in the present example and the comparative example.

[0075] Table 1

[0076]

[0077]

[0078] CMC coating:

[0079] To prepare the CMC coatings, the following CMC grades were used:

[0080] ● "CMC FinnFix 150" (produced by Nouryon), which is a carboxymethyl cellulose with a Mw of about 120,000 g / mol

[0081] ● "CMC FinnFix 300" (produced by Nouryon), which is a carboxymethyl cellulose with a Mw of about 180,000 g / mol

[0082] ● "CMC FinnFix 700" (produced by Nouryon), which is a carboxymethyl cellulose with a Mw of about 270,000 g / mol

[0083] ● "CMC FinnFix BBP H15S" (produced by Nouryon), which is a mixture of carboxymethyl cellulose with different Mw

[0084] Aqueous compositions containing different carboxymethylcellulose grades in varying amounts were prepared to obtain approximately 2 g / m 2 coating.

[0085] Example 1: Evaluation of Types of CMC Coatings

[0086] For Examples 1.1 to 1.4 and Comparative Example 1.1, the oxygen barrier properties of parchment paper (Sulpack 60L) with a low parchmentization grade, which was either uncoated or coated by applying different types of CMC coatings comprising 100 wt. % of carboxymethyl cellulose in two layers to its surface using a manual coater (without pressure), have been evaluated as shown in Table 2. For Example 1.5, supercalendered paper (Cristal 90L) coated by applying CMC Finnfix 300 in two layers to its surface using a manual coater has been evaluated as shown in Table 2. TM 401 37g) were evaluated for their oxygen barrier properties.

[0087] Table 2

[0088]

[0089]

[0090] When no CMC coating is used, it is not possible to obtain sufficient oxygen barrier properties (see Comparative Example 1.1). When a CMC coating with a lower Mw is used, sufficient OTR can be obtained (see Example 1.1). When a CMC coating with a medium Mw is used, the OTR can be further reduced (see Example 1.2). When a CMC coating with a high Mw is used, a thinner coating can be applied and sufficient OTR can also be obtained (see Example 1.3). When a CMC blend coating is used, excellent OTR can also be obtained (see Example 1.4). The use of CMC coatings can also improve the oxygen barrier properties of super calendered paper (Example 1.5).

[0091] Example 2: Adding a softener to a CMC coating

[0092] As shown in Table 3, the oxygen barrier properties of parchment paper with a low parchmentization grade (Sulpack 60L) have been evaluated, the parchment paper being either uncoated or coated by applying a CMC coating to its surface using "CMC-FinnFix 300" and optionally a softener (without pressure) using a manual coating machine.

[0093] Table 3

[0094]

[0095] When no CMC coating is used, it is not possible to obtain acceptable oxygen barrier properties (see Comparative Example 2.1). When a CMC coating comprising 100% CMC is used, an excellent OTR can be obtained (see Example 2.1). When a CMC coating that additionally contains glycerol is used, the coating can be applied more efficiently and the OTR can be further reduced (see Example 2.2).

Claims

1. A barrier paper, comprising: Paper substrate; and a carboxymethyl cellulose coating layer formed on the surface of the paper substrate, in The paper substrate is cellulose paper, and The carboxymethylcellulose coating comprises 80 wt % to 100 wt % carboxymethylcellulose on a dry weight basis.

2. The barrier paper according to claim 1, wherein the paper substrate has a density of 800 kg / m 3 or higher, preferably 850kg / m 3 Or higher high density paper material.

3. The barrier paper according to claim 1 or 2, wherein the carboxymethyl cellulose coating is 1.5 g / m 2 or more, preferably 1.5 g / m 2 Up to 10g / m 2 An amount of is formed on the surface of the substrate.

4. The barrier paper according to any one of claims 1 to 3, wherein the cellulose paper substrate is selected from parchment paper, glassine paper, tracing paper, greaseproof paper and supercalendered paper.

5. The barrier paper according to any one of claims 1 to 4, wherein the carboxymethyl cellulose coating further comprises glycerin in an amount of 20 wt% or less based on dry weight.

6. The barrier paper according to any one of claims 1 to 5, wherein the carboxymethyl cellulose coating further comprises a salt, such as calcium chloride, sodium chloride and potassium chloride.

7. The barrier paper according to any one of claims 1 to 6, wherein the molecular weight of the carboxymethyl cellulose is 100,000 g / mol to 750,000 g / mol, preferably 100,000 g / mol to 400,000 g / mol.

8. The barrier paper according to any one of claims 1 to 7, wherein the oxygen permeability of the barrier paper is 0.10 cm 3 / m 2 / day to 100.0cm 3 / m 2 / day, as measured at 23°C and 50% relative humidity.

9. A method for producing barrier paper, the method comprising: applying a coating mixture comprising 80 wt % to 100 wt % of carboxymethyl cellulose on a dry weight basis to a surface of a paper substrate to form a carboxymethyl cellulose coating, in The paper substrate is cellulose paper.

10. The method according to claim 9, wherein the paper substrate has a density of 800 kg / m 3 or higher, preferably 850kg / m 3 Or higher high density paper material.

11. The method according to claim 9 or 10, wherein the coating mixture is 1.5 g / m 2 or more, preferably 1.5 g / m 2 Up to 10g / m 2 An amount of is applied to the surface of the paper substrate.

12. The method according to any one of claims 9 to 11, wherein the coating mixture further comprises 0 to 15 wt% glycerol and 0 to 5 wt% calcium chloride on a dry weight basis.

13. Use of the barrier paper according to any one of claims 1 to 8 as a packaging material for oxygen sensitive items such as food, life science and diagnostic devices.

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