Paper and paper-based packaging material comprising same

Abstract

A paper-based packaging material according to various embodiments of the present invention may comprise a paper substrate. The paper-based packaging material may include a water-soluble polymer. The water-soluble polymer may be impregnated into the paper substrate and have a refractive index of 1.3-1.6. The paper-based packaging material may have a haze of 40% or less and a light transmittance of 88% or more, according to ASTM D1003.

Description

Paper and paper-based packaging materials containing the same

[0001] The present invention relates to packaging materials, and more particularly to paper-based packaging materials.

[0002] Packaging materials are used to enclose and protect products (e.g., electronic devices such as smartphones, tablet computers, and televisions). Polymers such as polyethylene, polypropylene, and polyvinyl chloride are widely used as packaging materials due to their high chemical resistance and low cost. Polymer packaging materials can be made transparent, allowing the packaged product inside to be visible from the outside.

[0003] The increasing use of polymer packaging materials is leading to a rise in polymer waste. Polymer waste can cause air pollution and carbon emissions when incinerated, soil contamination when landfilled, and marine plastic pollution when dumped. Therefore, there is a growing need to replace polymer packaging with materials that generate less waste and have a shorter environmental retention time.

[0004] Paper packaging is one of the packaging materials that has the potential to replace polymer packaging because it is relatively inexpensive, easily recycled, and decomposes relatively quickly in water when discarded.

[0005] Paper's low transparency limits its application. Even when paper is thinned to increase light transmittance, it's difficult to achieve transparency due to the inherent haze that causes light to scatter. Consequently, when packaging a product with paper, the packaged product cannot be seen from the outside, making it difficult for users to directly recognize the packaging object from the outside. Furthermore, it's difficult to apply packaging designs designed to allow full or partial visibility of the packaged product to paper packaging. Furthermore, conventional paper packaging cannot be used in areas where transparency is required, such as protecting the screen of an electronic device.

[0006] The various embodiments disclosed herein can provide transparent paper and paper-based packaging materials with reduced haze and high transparency.

[0007] A paper-based packaging material according to various embodiments of the present invention may include a paper substrate. The paper-based packaging material may include a water-soluble polymer. The water-soluble polymer may be impregnated into the paper substrate and have a refractive index of 1.3 to 1.6. The paper-based packaging material may have a haze of 40% or less and a light transmittance of 88% or more as per ASTM D1003.

[0008] In various embodiments, the water-soluble polymer may include at least one of PVP (Polyvinylpyrrolidone), PolyDADMAC (Poly diallyldimethylammonium chloride), or PAA (Polyacrylic acid).

[0009] According to another embodiment of the present invention, a paper-based packaging material may include a water-soluble polymer having a refractive index of 1.3 to 1.6. The paper-based packaging material may include cellulose nanofibers dispersed within the water-soluble polymer. In various embodiments, the cellulose nanofibers may have a length of 400 nanometers or less.

[0010] In various embodiments, the water-soluble polymer (220) may include at least one of PVP (Polyvinylpyrrolidone), PolyDADMAC (Poly diallyldimethylammonium chloride), or PAA (Polyacrylic acid).

[0011] In various embodiments, the paper substrate (210) may have a basis weight of 60 g / ㎡ or less.

[0012] In various embodiments, the paper substrate (210) may have a density of 1 g / cm3 or greater.

[0013] In various embodiments, the paper substrate (210) may have a porosity of 30% or less.

[0014] In various embodiments, the amount of impregnation of the polymer into the paper substrate (210) may be 5 g / m2 or more and 30 g / m2 or less.

[0015] In various embodiments, the paper substrate (210) may have a basis weight of 32 g / m2, and the amount of polymer impregnated into the paper substrate (210) may be 15 g / m2 or more.

[0016] In various embodiments, the paper-based packaging material (200) may be manufactured by an operation of absorbing an aqueous solution of the water-soluble polymer (220) into the paper substrate (210) and an operation of drying the paper substrate (210) with the aqueous solution absorbed therein on a dry substrate. The dry substrate may have a hydrophilic surface.

[0017] In various embodiments, the aqueous solution may contain 10 to 20 wt% of the water-soluble polymer (220).

[0018] In various embodiments, the water-soluble polymer (220) further includes an anionic polymer electrolyte, and the anionic polymer electrolyte may include carboxymethyl cellulose (CMC).

[0019] In various embodiments, the paper-based packaging material (200) may have a re-release rate of 80% or more according to UL2485.

[0020] In various embodiments, the water-soluble polymer (220) may include the polyvinylpyrrolidone (PVP) and the carboxymethyl cellulose (CMC) in a weight ratio of 3:1.

[0021] In various embodiments, the polyvinylpyrrolidone (PVP) may have a molecular weight of less than 10,000 daltons.

[0022] In various embodiments, the CMC (carboxymethyl cellulose) may have a molecular weight of less than or equal to 90,000 daltons.

[0023] A paper-based packaging material (200) according to various embodiments of the present invention may include a water-soluble polymer (220) having a refractive index of 1.3 to 1.6. The paper-based packaging material (200) may include cellulose nanofibers (213) dispersed within the water-soluble polymer (220).

[0024] In various embodiments, the paper-based packaging material (200) may have a haze of 1% or less and a light transmittance of 92% or more as per ASTM D1003.

[0025] In various embodiments, the cellulose nanofibers (213) may have a length of 400 nanometers or less.

[0026] In various embodiments, the cellulose nanofibers (213) may include at least one of untreated cellulose nanofibrils (UCNF), TEMPO-oxidized cellulose nanofibrils (TOCN), enzymatic hydrolyzed cellulose nanofibrils (ECNF), or carboxymethylated cellulose nanofibrils (CMCNF).

[0027] In various embodiments, the water-soluble polymer (220) may include at least one of PVP (Polyvinylpyrrolidone), PolyDADMAC (Polydiallyldimethylammonium chloride), or PAA (Polyacrylic acid).

[0028] In various embodiments, the paper-based packaging material (200) may include the TOCN and PVP in a weight ratio of 5:5 to 7:3.

[0029] And the embodiments disclosed in this document disclosed in this specification and drawings are only specific examples to easily explain the technical contents according to the embodiments disclosed in this document and to help understand the embodiments disclosed in this document, and are not intended to limit the scope of the embodiments disclosed in this document. Therefore, the scope of the various embodiments disclosed in this document should be interpreted as including all changes or modified forms derived based on the technical ideas of the various embodiments disclosed in this document in addition to the embodiments disclosed herein.

[0030] According to various embodiments disclosed in this document, the water-soluble polymer impregnated between the fibers of the paper substrate has a refractive index similar to that of the cellulose fibers of the paper, thereby reducing scattering of light by the cellulose fibers, thereby improving the transparency of transparent paper and paper-based packaging materials.

[0031] In connection with the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0032] FIGS. 1A, 1B and 1C are drawings showing paper-based packaging materials according to various embodiments.

[0033] Figure 2 is a schematic diagram showing transparent paper according to various embodiments of the present invention.

[0034] Figure 3a is a microscopic photograph showing the transparent paper of the present invention and the paper packaging material of a comparative example.

[0035] Figures 3b and 3c are schematic diagrams showing the difference in transparency between the transparent paper of the present invention and the paper packaging material according to a comparative example.

[0036] Figure 4 is a graph showing the change in the amount of haze according to the amount of water-soluble polymer impregnation according to various embodiments of the present invention.

[0037] Figure 5a is a graph showing the haze of transparent paper according to various embodiments.

[0038] Figure 5b is a graph showing the light transmittance of transparent paper according to various embodiments.

[0039] Figure 6a is a graph showing the impregnation amount and thickness of transparent paper according to various embodiments.

[0040] Figure 6b is a micrograph showing a cross-section of transparent paper according to various embodiments.

[0041] Figure 7 is a flowchart showing operations for manufacturing transparent paper according to various embodiments.

[0042] Figure 8 is a cross-sectional schematic diagram showing transparent paper according to other embodiments of the present invention.

[0043] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0044] The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The following embodiments may be modified in various ways, and the scope of the present invention is not limited to the embodiments described below. Rather, these embodiments are provided to more faithfully and completely explain the present disclosure and to fully convey the spirit of the present invention to those skilled in the art.

[0045] Additionally, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation, and like symbols in the drawings indicate like elements. As used herein, the term "and / or" includes any one of the listed items and any combination of one or more of them.

[0046] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" include plural forms unless the context clearly dictates otherwise. Furthermore, when used herein, the words "comprise" and / or "comprising" specify the presence of stated features, numbers, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, components, and / or groups thereof.

[0047] The various embodiments of this document and the terminology used therein are not intended to limit the technical features described in this document to specific embodiments, but should be understood to include various modifications, equivalents, or substitutes of the embodiments. In connection with the description of the drawings, similar reference numerals may be used for similar or related components. The singular form of a noun corresponding to an item may include one or more of the items, unless the context clearly indicates otherwise. In this document, each of the phrases "A or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", and "at least one of A, B, or C" can include any one of the items listed together in the corresponding phrase among those phrases, or all possible combinations thereof. Terms such as "first," "second," or "first" or "second" may be used merely to distinguish one component from another, and do not limit the components in any other respect (e.g., importance or order). When a component (e.g., a first component) is referred to as "coupled" or "connected" to another (e.g., a second component), with or without the terms "functionally" or "communicatively," it means that the component can be connected to the other component directly (e.g., wired), wirelessly, or through a third component.

[0048] The term "module" used in various embodiments of this document may include a unit implemented in hardware, software, or firmware, and may be used interchangeably with terms such as logic, logic block, component, or circuit. A module may be an integral component, or a minimum unit or part of such a component that performs one or more functions. For example, according to one embodiment, a module may be implemented in the form of an application-specific integrated circuit (ASIC).

[0049] According to various embodiments, each component (e.g., a module or a program) of the above-described components may include one or more entities, and some of the entities may be separated and placed in other components. According to various embodiments, one or more components or operations of the aforementioned components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (e.g., a module or a program) may be integrated into a single component. In such a case, the integrated component may perform one or more functions of each of the plurality of components identically or similarly to those performed by the corresponding component among the plurality of components prior to the integration. According to various embodiments, the operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

[0050] Although terms such as first, second, etc. are used herein to describe various elements, components, regions, and / or portions, it is to be understood that these elements, components, regions, and / or portions are not limited by these terms. These terms are only used to distinguish one element, component, region, or portion from another. Accordingly, a first element, component, region, or portion described below may also refer to a second element, component, region, or portion without departing from the teachings of the present invention.

[0051] Additionally, when it is said that a layer is formed or disposed on another layer, an intermediate layer may be formed or disposed between these layers. Similarly, when it is said that a material is adjacent to another material, there may be an intermediate material between these materials. Conversely, when it is said that a layer or material is formed or disposed "directly" or "immediately" on another layer or material, or "directly" or "directly" adjacent or in contact with another layer or material, it should be understood that there is no intermediate material or layer between these materials or layers.

[0052] Hereinafter, embodiments of the present invention will be described with reference to drawings schematically illustrating ideal embodiments of the present invention. In the drawings, for example, the size and shape of components may be exaggerated for convenience and clarity of explanation, and variations in the depicted shapes may be expected during actual implementation. Therefore, embodiments of the present invention should not be construed as being limited to the specific shapes of the regions illustrated in this specification.

[0053] FIG. 1a, FIG. 1b and FIG. 1c are drawings showing paper-based packaging materials (200) according to various embodiments.

[0054] Referring to FIGS. 1A to 1C, a paper-based packaging material (200) according to various embodiments of the present invention may have various forms. For example, as illustrated in FIGS. 1A and 1B, the paper-based packaging material (200) may be a packaging film that covers at least a portion of the exterior of a product (e.g., an electronic device such as a smart phone (101a), a tablet, a monitor (101b), a television, or a portable computer). The paper-based packaging material (200) of the present invention protects the exterior of a product during distribution, while allowing the exterior of the product inside to be visible from the outside of the paper-based packaging material (200) until it is removed by the end user, thereby providing the user with information about the exterior of the product and providing the user with satisfaction.

[0055] In addition, as illustrated in FIG. 1c, the paper-based packaging material (200) may be a packaging material (e.g., a package in the form of an envelope or pouch) that packages various accessory materials of a product (e.g., a remote control device (101c), a cable (101d), a user manual (101e)) separately from other components of the product. The paper-based packaging material (200) of the present invention allows accessory materials packaged inside to be recognized from the outside. Therefore, when a user uses an electronic device, the user can intuitively recognize and take out the necessary accessory materials from the outside of the packaging material, thereby improving the convenience of using the product.

[0056] As described above, the paper-based packaging material (200) according to the present disclosure can allow the packaged object to be viewed from the outside of the package due to its high transparency. To this end, the paper-based packaging material (200) according to various embodiments of the present invention can have high light transmittance and low light scattering, thereby having low haze. For example, the paper-based packaging material (200) according to the present invention can have a light transmittance of 88% or more when measured according to a standard such as ASTM D1003. When the paper-based packaging material (200) has the optical properties described above, the inside of the paper-based packaging material (200) can be clearly viewed. When the light transmittance is less than 88%, the inside of the packaging material may not be clearly viewed due to insufficient light transmission. In addition, the paper-based packaging material (200) according to the present invention can have a haze of 40% or less when measured according to a standard such as ASTM D1003. When the haze exceeds 40%, the product inside the packaging may appear cloudy due to light scattering.

[0057] Figure 2 is a schematic diagram showing transparent paper (201) according to various embodiments of the present invention.

[0058] Referring to FIG. 2, transparent paper (201) according to various embodiments may include a paper substrate (210) and a water-soluble polymer (220).

[0059] The paper substrate (210) may include cellulose fibers (211). The cellulose fibers (211) are derived from the raw material of paper and may have a length of 100 to 1000 micrometers and a diameter of 1 to 50 micrometers. The cellulose fibers (211) may be randomly and / or semi-randomly oriented and intertwined within the paper substrate (210).

[0060] In various embodiments, the paper substrate (210) may have voids (212). The voids (212) may be spaces formed between a plurality of cellulose fibers (211). The ratio of the volume occupied by the voids (212) in the paper substrate (210) may be defined as the void ratio of the paper substrate (210). In addition, the value obtained by dividing the mass of the paper by the volume of the entire paper substrate (210) including the voids (212) may be defined as the density (or apparent density) of the paper substrate (210). In addition, the value obtained by dividing the mass of the paper substrate (210) by the area of ​​the paper substrate (210) may be defined as the basis weight of the paper substrate (210).

[0061] In various embodiments, the refractive index of the cellulose fibers (211) of the paper substrate (210) may be 1.4 to 1.5.

[0062] In various embodiments, the water-soluble polymer (220) of the transparent paper (201) may be impregnated into the paper substrate (210). For example, the water-soluble polymer (220) may penetrate into the pores (212) formed in the paper substrate (210) to fill at least a portion of the pores (212) of the paper substrate (210).

[0063] In various embodiments, the refractive index of the water-soluble polymer (220) may be substantially the same as or similar to the refractive index of the cellulose fibers (211) of the paper substrate (210). For example, the refractive index of the water-soluble polymer (220) may be 1.3 to 1.6. For example, the difference between the refractive index of the water-soluble polymer (220) and the refractive index of the cellulose fibers (211) may be 0.1 or less. Since the refractive index of the water-soluble polymer (220) is the same as or similar to the refractive index of the cellulose fibers (211) of the paper substrate (210), the transparency of the paper substrate (210) may be improved.

[0064] In various embodiments, the water-soluble polymer (220) may include a monomer having at least one hydrophilic functional group. The water-soluble polymer (220) may be a polymer that is easily dissolved in water by having a molecular structure and a crystal structure that facilitate water penetration in a solid or amorphous state. The water-soluble polymer (220) may include, for example, at least one of PVP (polyvinylpyrrolidone), PolyDADMAC (poly-diallyl dimethyl ammonium chloride), and PAA (polyacrylic acid).

[0065] Transparent paper (201) comprising a water-soluble polymer (220) impregnated into a paper substrate (210) may have good water decomposition properties. The transparent paper (201) according to the present invention and the paper-based packaging material (200) comprising the same may be recycled through a pulping process used in the recycling of conventional paper materials. In the pulping process, the water-soluble polymer (220) may be dissolved in water and removed, and the paper substrate (210) may be decomposed into fiber particles and recovered as pulp. In addition, the paper-based packaging material (200) of the present invention may be easily dissolved and / or decomposed in water when discarded after use and dumped into rivers and / or the ocean, thereby reducing pollution caused by marine waste.

[0066] The recyclability of paper materials by water dissociation can be measured through the repulpability rate, which is the ratio of the dry weight of the solid mass remaining without dissociation to the total paper weight when the paper material is water dissociated in a pulping solution standardized by standards such as UL2485. For easy recycling, the repulpability rate of transparent paper (201) can be 80% or higher.

[0067] In various embodiments, the water-soluble polymer (220) may have a low molecular weight. For example, the water-soluble polymer (220) may include polyvinylpyrrolidone (PVP) having a molecular weight of 10,000 daltons or less. The lower the molecular weight of the water-soluble polymer (220), the lower the crystallinity of the polymer chains may be, and also, the easier it may be for moisture to penetrate between the polymer chains.

[0068] In various embodiments, the water-soluble polymer (220) may further include an anionic polymer electrolyte. The anionic polymer electrolyte may improve the water dissociation property of the water-soluble polymer (220). The anionic polymer electrolyte may include, for example, sodium carboxymethyl cellulose (CMC). The water-soluble polymer may include, for example, PVP and CMC in a weight ratio of 3:1. It has been confirmed that the transparent paper (201) of the present invention including the water-soluble polymer having such a composition can have a repulpation rate of 85.6% according to UL2485.

[0069] Figure 3a is a microscopic photograph showing the transparent paper (201) of the present invention and the paper packaging material of a comparative example.

[0070] Figures 3b and 3c are schematic diagrams showing the difference in transparency between the transparent paper (201) of the present invention and the paper packaging material according to a comparative example.

[0071] Referring to Fig. 3a, the paper packaging material (20) of the comparative example may be a paper packaging material in which the paper substrate is not impregnated with a polymer. It can be seen that the paper packaging material (20) of the comparative example is not impregnated with a polymer (e.g., a water-soluble polymer (220) of the present invention), and thus a large number of voids exist between the fibers. In contrast, the transparent paper (201) of the present invention is at least partially filled with the water-soluble polymer (220) between the cellulose fibers (211), and thus has relatively fewer voids (212) than the comparative example.

[0072] Referring to FIG. 3b, the paper packaging material (20) according to the comparative example may include cellulose fibers (21) and voids (22). The voids (22) may be filled with air. The refractive index of the cellulose fibers (21) is between 1.4 and 1.5, and the refractive index of the air in the voids (22) is about 1. Therefore, when light (L) passes through the interface between the cellulose fibers (21) and the voids (22), the light (L) may be refracted and / or reflected due to the difference in refractive index. Since the cellulose fibers (21) of the paper packaging material (20) may be irregularly oriented and have different sizes and shapes, the light (L) may be irregularly refracted and / or reflected at the interface between the fibers and the voids (22). Therefore, the light (L) passing through the paper packaging material (20) of the comparative example may be scattered and exhibit haze. Additionally, some of the light (L) passing through the paper packaging material (20) of the comparative example may be reflected in the direction of incidence or absorbed while being reflected multiple times between cellulose fibers (21). Therefore, the light transmittance of the paper packaging material (20) of the comparative example may be low.

[0073] Referring to FIG. 3c, in the transparent paper (201) according to the embodiment of the present invention, at least a portion of the void (212) is filled with a water-soluble polymer (220), and the refractive index of the water-soluble polymer (220) is substantially the same as or similar to that of the cellulose fiber (211), so that when light (L) passes through the boundary between the cellulose fiber (211) and the void (212), refraction and / or reflection of the light (L) can be reduced. Therefore, the transparent paper (201) according to the present invention and the paper-based packaging material (200) including the same have low haze and high light transmittance. Therefore, the transparency of the paper-based packaging material (200) can be improved.

[0074] In order to verify the transparency of the paper-based packaging material (200) of the present invention, a paper substrate (210) was made of thin paper having a basis weight of 32 g / ㎡, and water-soluble polymers (220) having different materials and impregnation amounts were impregnated into the paper substrate (210), and the haze was measured according to ASTM D1003. The measurement results are shown in Fig. 4.

[0075] Figure 4 is a graph showing the change in the amount of haze according to the amount of water-soluble polymer impregnation according to various embodiments of the present invention.

[0076] Referring to FIG. 4, the paper substrate (210) according to an embodiment of the present invention can have a haze of 57% in a state in which the paper substrate (210) is not impregnated with a water-soluble polymer (220) (e.g., PVP, PolyDADMAC, and / or PAA). The transparent paper (201) of the present invention, which includes the paper substrate (210) and the water-soluble polymer (220) impregnated in the paper substrate (210), can have a lower haze than the paper substrate (210).

[0077] For example, when a water-soluble polymer (220) is impregnated into a paper substrate (210) at 5 g / ㎡ or more, the haze of the transparent paper (201) according to the present invention can be 40% or less. As the haze is reduced to 40% or less, an object located inside a paper-based packaging material (200) including the transparent paper (201) of the present invention can be relatively easily recognized from the outside. When a water-soluble polymer (220) is impregnated at 30 g / ㎡ or more, the haze can be reduced to 20% or less.

[0078] Accordingly, referring to FIG. 4, it can be seen that the transparency of the transparent paper (201) according to the present invention can be effectively improved by impregnating the paper substrate (210) with a water-soluble polymer (220) at 5 to 30 g / ㎡.

[0079] In order to confirm the optical properties of the transparent paper (201) of the present invention according to the type of paper substrate (210), the optical properties were tested by impregnating paper substrates (210) of different materials with a water-soluble polymer. In the test, transparent paper (201) was manufactured by impregnating the paper substrate (210) of each example with a 20 wt% aqueous solution of PVP (polyvinylpyrrolidone) and drying it. The physical properties of each paper substrate (210) are shown in Table 1, and the test results for each paper substrate (210) are shown in FIGS. 5a and 5b.

[0080] ClassificationBasis weight (g / ㎡)Thickness (μm)Density (g / cm3)Light transmittance (%)Haze (%)1Neutral interlayer paper16370.4375.690.52Paper paper22390.5651.396.83Glassine paper26241.0874.773.94Paper 125241.0170.083.65Paper 232251.2185.256.66Wet paper30460.6746.697.47Deer paper35470.7443.197.58Tracing paper45470.9680.093.4

[0081] FIG. 5A is a graph showing the haze of transparent paper (201) according to various embodiments. FIG. 5B is a graph showing the light transmittance of transparent paper (201) according to various embodiments. Referring to Table 1, FIG. 5A, and FIG. 5B, it can be confirmed that the light transmittance increases and the haze decreases as a result of impregnating the water-soluble polymer (220) into all types of paper substrates (210). In addition, it can be confirmed that the amount of increase in light transmittance and the amount of decrease in haze may vary depending on the type of paper substrate (210).

[0082] Referring to FIG. 5a, it can be seen that the degree of improvement in light transmittance is low when a paper substrate (210) of a low-density paper type, such as a paper substrate (210) of a paper type such as a Japanese paper or a Noroo paper, is impregnated with a water-soluble polymer (220). The low density of the paper substrate (210) may mean that there are many pores (212) distributed within the paper substrate (210). When impregnating the paper substrate (210) with a water-soluble polymer (220), if the density of the paper substrate (210) is low, it may be difficult for the water-soluble polymer (220) to completely fill the pores (212) of the paper substrate (210). Therefore, the light transmittance may decrease due to scattering due to diffuse reflection and / or diffuse refraction of light occurring in some remaining pores. In various embodiments, if the porosity of the paper substrate (210) is 30% or less, the transparent paper (201) impregnated with the water-soluble polymer (220) can have appropriate transparency.

[0083] Referring to FIG. 5b, it can be seen that the paper substrate (210) of a high-density type has a large degree of haze reduction when impregnated with a water-soluble polymer (220). For example, it can be seen that the haze of lactic acid paper 1 and lactic acid paper 2 having a density of 1 g / cm3 or more is reduced to 40% or less when impregnated with a water-soluble polymer (220). This may be because when the density of the paper substrate (210) is high, the pores (212) are distributed less within the paper substrate (210), so that the water-soluble polymer (220) can easily fill the pores (212) of the paper substrate (210) during impregnation. Therefore, embodiments of transparent paper (201) having a paper substrate (210) having a density of 1 g / cm3 or more can have improved transparency.

[0084] In order to confirm the appropriate level of impregnation amount of water-soluble polymer (220) for transparent paper (201) in various embodiments of the present invention, transparent paper (201) was manufactured by impregnating a paper substrate (210) with a water-soluble polymer (220) at different impregnation amounts using a base paper having a basis weight of 32 g / ㎡, and measuring the impregnation amount and thickness, and observing the cross-section using a confocal laser scanning microscope. The test results are shown in FIGS. 6A and 6B.

[0085] Figure 6a is a graph showing the impregnation amount and thickness of transparent paper (201) according to various embodiments.

[0086] FIG. 6b is a micrograph showing a cross-section of transparent paper (201) according to various embodiments.

[0087] In Fig. 6b, E1 is an example in which the impregnation amount of the water-soluble polymer (220) is 6.5 g / m2, E2 is an example in which the impregnation amount is 15.3 g / m2, and E1 is an example in which the impregnation amount is 29.3 g / m2. In the confocal laser scanning microscope photograph, the area with high brightness indicates the area in which the water-soluble polymer (220) is distributed in large quantities.

[0088] Referring to FIGS. 6A and 6B, the thickness of the transparent paper (201) may increase relatively gradually as the amount of impregnation of the water-soluble polymer (220) increases, and may increase relatively rapidly when a certain critical impregnation amount is exceeded. For example, in an embodiment in which a paper substrate (210) is made of a base paper having a basis weight of 32 g / ㎡, if the amount of impregnation of the water-soluble polymer (220) is 15 g / ㎡ or more, the increase in thickness of the transparent paper (201) according to the increase in the amount of impregnation may be relatively higher than when the amount of impregnation is less than 15 g / ㎡. When impregnating the paper substrate (210) with the water-soluble polymer (220), the water-soluble polymer (220) may fill the pores (212) of the paper substrate (210). When the water-soluble polymer (220) is impregnated in a larger amount than the amount at which the pores (212) of the paper substrate (210) are saturated or substantially saturated, the additionally impregnated water-soluble polymer (220) is located on the surface rather than in the pores (212) of the paper substrate (210), so that the thickness of the manufactured transparent paper (201) can be increased. That is, it can be seen that the amount of impregnation at the point where the slope of the graph of the impregnation amount and thickness changes in the graph of FIG. 6a is the point at which the pores (212) of the paper substrate (210) are saturated.

[0089] Referring to FIG. 6b, it can be seen that the difference in thickness between Example E1 with an impregnation amount of 6.5 g / ㎡ of water-soluble polymer (220) and Example E2 with an impregnation amount of 15.3 g / ㎡ is relatively small, and that the pores (212) of Example E2 are filled more with the water-soluble polymer (220) than in E1. In addition, when comparing Example E2 with an impregnation amount of 15.3 g / ㎡ and Example E3 with an impregnation amount of 29.3 g / ㎡, it can be seen that the thickness of Example E3 is significantly increased compared to E2. That is, it can be seen that the pores (212) of the paper substrate (210) with a basis weight of 32 g / ㎡ are saturated at an impregnation amount of about 15 g / ㎡.

[0090] Figure 7 is a flowchart showing operations for manufacturing transparent paper (201) according to various embodiments.

[0091] Referring to FIG. 7, transparent paper (201) according to various embodiments can be manufactured by an operation (701) of manufacturing a paper substrate (210) (original paper), an operation (702) of absorbing an aqueous solution of a water-soluble polymer (220) into the paper substrate (210), and an operation (703) of drying the paper substrate (210) in which the aqueous solution of the water-soluble polymer (220) has been absorbed (which may be referred to as 'impregnated paper') on a drying base. With respect to the operation (701) of manufacturing the paper substrate (210), reference may be made to a known paper manufacturing process.

[0092] In various embodiments, the operation (702) of absorbing the aqueous solution of the water-soluble polymer (220) into the paper substrate (210) may be performed by a gravure coating device or a dipping device. The gravure coating device may be a device that transfers the aqueous solution of the water-soluble polymer (220) onto the surface of the paper substrate (210) using a roll immersed in the aqueous solution of the water-soluble polymer (220). The dipping device may be a device that directly immerses the paper substrate (210) in a bath of the aqueous solution of the water-soluble polymer (220) so that the aqueous solution of the water-soluble polymer (220) is absorbed into the paper substrate (210).

[0093] In various embodiments, the concentration of the water-soluble polymer (220) aqueous solution may be 10 to 20 wt%. When the concentration of the aqueous solution is less than 10 wt%, it is impossible to sufficiently impregnate the paper substrate (210) with the water-soluble polymer (220), and when the concentration of the aqueous solution exceeds 20 wt%, the viscosity of the aqueous solution increases, making it difficult for the water-soluble polymer (220) to easily penetrate the paper substrate (210), so that the pores (212) of the paper substrate (210) are not sufficiently filled, and thus the haze and light transmittance of the transparent paper (201) may deteriorate.

[0094] In various embodiments, the drying operation (703) may be performed at room temperature or at an elevated temperature (e.g., 60 degrees Celsius). In various embodiments, the drying substrate may be flat or cylindrical (e.g., a drying roll). The impregnated paper may be placed on the drying substrate and dried while maintaining a flat shape. In various embodiments, the drying substrate may be hydrophilic or hydrophobic.

[0095] In order to determine the influence of the properties of the dry substrate on the quality of the manufactured transparent paper (201), transparent paper (201) was manufactured on hydrophobic and hydrophilic dry substrates, and the results are shown in the table.

[0096] Dry substrate material Contact angle Light transmittance (%) Haze (%) Teflon 110˚89.6 33.6 Si-coated PET 90˚89.2 25.5 PET 70˚89.7 21.0

[0097] Referring to Table 2, when the impregnated paper is dried on a dry substrate made of Teflon material having a water contact angle of 110 degrees and hydrophobicity, the transparent paper (201) manufactured through this has good light transmittance but a relatively high haze of 33.6%. In contrast, when the impregnated paper is dried on a dry substrate made of silicone-coated PET (polyethylene terephthalate) and PET material having water contact angles of 90 degrees and 70 degrees, the transparent paper (201) manufactured through this has a relatively low haze of 25.5% and 21.0%. When the impregnated paper impregnated in a water-soluble polymer (220) aqueous solution is dried on a hydrophobic dry substrate, the water-soluble polymer (220) aqueous solution of the impregnated paper may be pushed out by a repulsive force due to the hydrophobicity of the dry substrate. In addition, a phenomenon in which the impregnated paper falls off from the hydrophobic dry substrate may occur. Therefore, irregular unevenness may occur on the surface of the transparent paper (201) dried on a hydrophobic dry substrate, which may increase haze due to irregular reflection and refraction. Therefore, the transparent paper (201) manufactured by drying the impregnated paper on a hydrophilic dry substrate may have relatively low haze and thus good transparency.

[0098] Figure 8 is a cross-sectional schematic diagram showing transparent paper (201) according to other embodiments of the present invention.

[0099] Referring to FIG. 8, the transparent paper (201) may include a water-soluble polymer (220) and cellulose nanofibrils (213). In various embodiments, the water-soluble polymer (220) may be a water-soluble polymer (220) having a refractive index of 1.3 to 1.6. For example, the water-soluble polymer (220) may be a polymer that is easily soluble in water, including at least one of polyvinylpyrrolidone (PVP), poly-diallyl dimethyl ammonium chloride (PolyDADMAC), and polyacrylic acid (PAA).

[0100] The cellulose nanofibers (213) may be cellulose fibers (211) dispersed in a water-soluble polymer (220) and having a fiber length (L1) of less than 1000 micrometers. For example, the cellulose nanofibers may be obtained by grinding cellulose fibers (211) using a homogenizer or the like to have a length of less than 1000 nanometers. In various embodiments, the cellulose nanofibers (213) may include untreated cellulose nanofibrils (UCNF), which are cellulose nanofibers (213) that have not been chemically modified. In various embodiments, the cellulose nanofibers (213) may include various chemically modified cellulose nanofibers (213), such as TEMPO-oxidized cellulose nanofibrils (TOCN), enzymatic hydrolyzed cellulose nanofibrils (ECNF), and / or carboxymethylated cellulose nanofibrils (CMCNF).

[0101] In various embodiments, the length (L1) of the cellulose nanofibers (213) may be shorter than the wavelength of visible light. For example, the length (L1) of the cellulose nanofibers (213) may be 400 nanometers or less. When the length of the cellulose nanofibers (213) is shorter than the wavelength of light, light passing through the transparent paper (201) in which the cellulose nanofibers (213) are dispersed can maintain straightness with relatively little interference such as reflection, refraction, and / or scattering (e.g., Mie scattering) by the cellulose nanofibers (213) due to the diffraction phenomenon. Since the wavelength band of visible light is 700 nanometers to 400 nanometers, when the cellulose nanofibers (213) have a length of 400 nanometers or less, scattering of visible light by the cellulose nanofibers (213) can be reduced. Accordingly, the haze of the transparent paper (201) can be reduced and the light transmittance can be improved.

[0102] In order to test the optical properties of transparent paper (201) including cellulose nanofibers (213) according to embodiments of the present invention, transparent paper (201) was manufactured by mixing and drying an aqueous solution of cellulose nanofibers (213) and a water-soluble polymer (220). The cellulose nanofibers (213) are TOCN (TEMPO-oxidized cellulose nanofibrils), and the water-soluble polymer (220) is PVP (polyvinylpyrrolidone). The cellulose nanofibers (213) and the water-soluble polymer (220) were mixed in a ratio of 5:5, 6:4, and 7:3, respectively, to manufacture transparent paper (201). The test results are shown in Table 3.

[0103] Classification 7:3 Mix 6:4 Mix 5:5 Mix Light Transmittance (%) 92.3 92.0 92.2 Haze (%) 1.5 0.7 0.5

[0104] Referring to Table 3, it can be seen that the mixing ratio of cellulose nanofibers (213) and water-soluble polymer (220) does not significantly affect the light transmittance, and exhibits a good light transmittance of 92% or more within the mixing ratio range of 7:3 to 5:5. In addition, the haze of the transparent paper (201) is good at 1.5% or less within the mixing ratio range of 7:3 to 5:5, and it can be seen that the haze decreases as the ratio of the water-soluble polymer (220) to the cellulose nanofibers (213) increases. The paper-based packaging material (200) according to various embodiments of the present invention may include a paper substrate (210). The paper-based packaging material (200) may include a water-soluble polymer (220). The water-soluble polymer (220) may be impregnated into the paper substrate (210) and may have a refractive index of 1.3 to 1.6. The above paper-based packaging material (200) may have a haze of 40% or less and a light transmittance of 88% or more according to ASTM D1003.

Claims

1. In paper-based packaging material (200), Paper substrate (210); and Contains a water-soluble polymer (220) impregnated into the above paper substrate (210) and having a refractive index of 1.3 to 1.6, Paper-based packaging material with a haze of 40% or less and a light transmittance of 88% or more as per ASTM D1003.

2. In paragraph 1, The above paper substrate (210) is a paper-based packaging material having a basis weight of 60 g / ㎡ or less.

3. In paragraph 1, The above paper substrate (210) is a paper-based packaging material having a density of 1 g / cm3 or more.

4. In paragraph 1, The above paper substrate (210) is a paper-based packaging material having a porosity of 30% or less.

5. In paragraph 1, A paper-based packaging material in which the impregnation amount of the polymer into the paper substrate (210) is 5 g / ㎡ or more and 30 g / ㎡ or less.

6. In paragraph 1, The above paper substrate (210) has a basis weight of 32 g / ㎡, A paper-based packaging material in which the impregnation amount of the polymer into the paper substrate (210) is 15 g / ㎡ or more.

7. In paragraph 1, The above paper-based packaging material (200) An operation of absorbing the aqueous solution of the water-soluble polymer (220) into the paper substrate (210); and It is manufactured by an operation of drying the paper substrate (210) in which the aqueous solution is absorbed on a drying substrate, A paper-based packaging material comprising 10 to 20 wt% of the water-soluble polymer (220) in the aqueous solution.

8. In paragraph 1, The above water-soluble polymer (220) is a paper-based packaging material containing an anionic polymer electrolyte including CMC (carboxymethyl cellulose).

9. In paragraph 1, The above water-soluble polymer (220) Containing at least one of PVP (Polyvinylpyrrolidone), PolyDADMAC (Poly diallyldimethylammonium chloride) or PAA (Polyacrylic acid), Paper-based packaging material with a re-release rate of 80% or higher according to UL2485 standards.

10. In paragraph 1, The above water-soluble polymer (220) Containing at least one of PVP (Polyvinylpyrrolidone), PolyDADMAC (Poly diallyldimethylammonium chloride) or PAA (Polyacrylic acid), A paper-based packaging material comprising the above PVP (polyvinylpyrrolidone) and the above CMC (carboxymethyl cellulose) in a weight ratio of 3:

1.

11. In paragraph 10, The above PVP (polyvinylpyrrolidone) has a molecular weight of less than 10,000 daltons, The above CMC (carboxymethyl cellulose) is a paper-based packaging material having a molecular weight of 90,000 daltons or less.

12. In paragraph 1, A water-soluble polymer (220) having a refractive index of 1.3 to 1.6; and A paper-based packaging material comprising cellulose nanofibers (213) dispersed within the water-soluble polymer (220).

13. In paragraph 12, Paper-based packaging material with a haze of 1% or less and a light transmittance of 92% or more as per ASTM D1003.

14. In paragraph 12, The above cellulose nanofibers (213) are paper-based packaging materials having a length of 400 nanometers or less.

15. In paragraph 12, The above cellulose nanofibers (213) include at least one of untreated cellulose nanofibrils (UCNF), TEMPO-oxidized cellulose nanofibrils (TOCN), enzymatic hydrolyzed cellulose nanofibrils (ECNF), or carboxymethylated cellulose nanofibrils (CMCNF), The water-soluble polymer (220) contains at least one of PVP (Polyvinylpyrrolidone), PolyDADMAC (Polydiallyldimethylammonium chloride), or PAA (Polyacrylic acid), A paper-based packaging material comprising the above TOCN and PVP in a weight ratio of 5:5 to 7:3.

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