Low-opacity paper packaging materials

Abstract

A heat-sealable paper with low basis weight and low opacity is disclosed. The heat-sealable paper with low opacity is made from a fiber web containing highly refined cellulose fibers. The fiber web may be initially coated with a bio-based wax such as coconut-based wax. The fiber web may be coated with a coating composition that forms a heat-sealable coating on the outer surface of the coated paper. The product may have excellent transparency or translucency properties. The product also has excellent heat-sealability properties that make the product well-suited for producing packages.

Description

[Technical Field]

[0001] Transparent or translucent materials are used in a wide variety of applications. Transparency is a highly desirable quality, for example, in packaging materials. For instance, packaging materials are necessary to protect products during delivery and sale, but consumers prefer to be able to see the product through the packaging. [Background technology]

[0002] In the past, most transparent or translucent materials, including packaging materials, were formed from plastic materials such as polyester polymers and polyolefin polymers. However, these plastic materials originate from non-renewable fossil resources, including petroleum-based resources. These resources are not sustainable, are not renewable, and produce polymer products that do not easily decompose. Therefore, in the past, efforts have been made to produce transparent or translucent materials from renewable resources such as cellulose materials.

[0003] For example, low-opacity or transparent papers have been developed and produced in the past. Transparent paper products have been used, for example, in the form of transparency paper or transparent windows for envelopes. However, these materials have only achieved limited success in producing packaging materials because they do not have sufficient heat-sealing properties.

[0004] Furthermore, to produce transparent or translucent paper, non-renewable resources or components that do not readily biodegrade were combined with the paper. For example, one type of paper produced in the past was made from wood pulp fibers, which may have been combined with enzymes such as xylanase. These substrates typically had a relatively high base weight to provide sufficient strength or other mechanical properties. To reduce the thickness of cellulose paper, compress the paper, and produce transparency, the paper was combined with petroleum-based chemicals or synthetic resins and then fed through a supercalendering process. As used herein, during supercalendering, the paper is first calendered by compressing it between metal cylinders and rollers. The paper is then fed through an additional set of calendering machines to produce a smoother, shinier paper, referred to as supercalendered paper. A supercalendering machine contains several cylinders alternating between polished metal and a soft, resilient surface. The supercalendering machine applies pressure, heat, and friction to gloss both sides of the paper, making it smooth and / or shiny.

[0005] As mentioned above, transparent or translucent papers produced in the past have various drawbacks and defects. For example, even if the fibers used to produce the paper are derived from renewable resources and are biodegradable and compostable, the paper is typically combined with petroleum-based chemicals or other synthetic resins that can hinder the goal of producing biodegradable materials. In addition, while supercalendering can be very effective in altering the properties of the paper, the process is very energy-intensive. Furthermore, the aforementioned papers cannot incorporate heat-sealing features.

[0006] Barrier properties against water, water vapor, and grease are important for packaging materials. These properties are typically achieved even with petroleum-based materials. [Overview of the project] [Problems that the invention aims to solve]

[0007] Considering the above, there is a need for low-opacity paper that can be sourced from more than 90% biological materials, is biodegradable and / or compostable. There is also a need for low-opacity paper that can be produced without supercalendering and likely using fewer materials such as fewer cellulose fibers. There is also a need for low-opacity paper that does not contain petroleum-based raw materials and has good barrier properties. Furthermore, there is a need for low-opacity paper that also has heat-sealing properties, so that the paper can heat-bond to itself to form transparent packaging. [Means for solving the problem]

[0008] The object of the present invention is to provide an alternative to plastic films currently on the market. More specifically, the disclosure is toward a low opacity paper that does not contain any petroleum-based resources, does not require the paper to be supercalendered, is produced at a relatively low basic weight, and therefore can reduce the energy requirements required to produce the product. The low opacity paper of the disclosure can also be formulated to be fully biodegradable and compostable. In addition, the low opacity paper may have an excellent balance of properties, including high transparency and low permeability to provide high barrier properties, good mechanical properties for conversion and handling, and excellent heat sealability.

[0009] In one aspect, the present disclosure is directed to paper products having low opacity characteristics. The paper product includes a fibrous web containing cellulose fibers. The cellulose fibers contained in the web can be purified to a relatively high degree such that they can be measured according to the drainage degree value. The drainage degree value (°SR) generally measures the rate at which a dilute suspension of purified fibers can be drained. The drainage degree is measured for drainage property by the Shopper - Riegler method. As used herein, the drainage degree can be measured in accordance with DIN EN ISO 5267 - 1:2000. The cellulose fibers contained in the web can have a degree of purification of about 60°SR or more, for example about 70°SR or more. The fibers generally have a drainage degree value of about 100°SR or less, for example about 90°SR or less. The fibrous web may also have a relatively low basis weight in one aspect to enhance transparency. For example, the basis weight of the web is about 38 g / m 2 hereinafter, for example about 35 g / m 2 hereinafter, for example about 33 g / m 2 hereinafter, for example about 30 g / m 2 hereinafter, for example about 28 g / m 2 hereinafter, for example about 25 g / m 2 hereinafter, for example about 23 g / m 2 hereinafter, and generally about 10 g / m 2 above, for example about 12 g / m 2 above may be. In a preferred embodiment, the basis weight of the fibrous web is from 10 to 24 g / m 2 and preferably from 10 to 18 g / m 2 within the range. The fibrous web defines a first surface and a second surface. As will be readily understood by those skilled in the art, the first surface and the second surface are the major surfaces of the fibrous web, which may be referred to as the "upper" and "lower" surfaces and are located on opposite sides of each other.

[0010] In accordance with this disclosure, at least two different coating compositions can be applied to the surface of a fiber web. The first coating comprises a transparency agent such as a bio-based wax or oil to reduce opacity. The second coating composition can form a heat-sealable coating which can be applied over the transparency agent coating on the first and / or second surface of the fiber web, preferably on only one of the first and second surfaces of the fiber web. This is the subject of feature (i) in claim 2. In a modified form, the first and second coating compositions can be applied to opposite surfaces of the fiber web, i.e., its first and second surfaces, as in the example of feature (ii) in claim 2. According to another aspect of this disclosure, the second coating composition can be combined with the transparency agent coating composition and applied to the web as a single coating. This is the subject of claim 1.

[0011] A heat-sealable coating composition can form the outer surface of a paper product even when combined with a transparent coating composition. The heat-sealable coating may contain a polymer such as a thermoplastic polymer or a protein. The polymer may be polyester, protein, polysaccharide, polysaccharide ester, polysaccharide ether, or polysaccharide ether ester. The protein may be casein, whey, etc. Paper products made according to this disclosure may exhibit an opacity of about 45% or less when tested according to ISO 2471:2008. For example, the opacity may be about 40% or less, or for example, about 35% or less.

[0012] The amount of transparent agent incorporated into the product can be determined by various factors. The basic weight (dry) of the transparent agent coating is 0.5 g / m². 2 Approximately 0.5 g / m², including all increments. 2 From approximately 18g / m 2 It can reach up to approximately 2 g / m². For example, the transparent coating is approximately 2 g / m². 2 To give an example, it is approximately 4g / m 2 To give an example, it is approximately 5g / m 2To give an example, it is approximately 6g / m 2 To give an example, it is approximately 7g / m 2 To give an example, it is approximately 8g / m 2 The basic weight may be as described above. The basic weight of the transparent coating is approximately 20 g / m². 2 For example, approximately 15g / m 2 For example, approximately 12g / m 2 For example, approximately 10g / m 2 For example, approximately 8g / m 2 The following is also acceptable.

[0013] In one embodiment, the transparent agent may be water-miscible and can be applied to a fiber web as an aqueous composition.

[0014] As described above, in one embodiment, the heat-sealable coating may contain a polymer. In one embodiment, the polymer may be thermoplastic starch or protein. The heat-sealable coating has a density of approximately 1 g / m². 2 To give an example, it is approximately 3g / m 2 To give an example, it is approximately 4g / m 2 To give an example, it is approximately 5g / m 2 The above, and generally about 20g / m² 2 For example, approximately 15g / m 2 For example, approximately 10g / m 2 For example, approximately 8g / m 2 It can be applied to a cellulose layer to have the following basic dry weight. When combined with a clearing agent, the basic weight of the coating is approximately 3 g / m². 2 To give an example, it is approximately 5g / m 2 To give an example, it is approximately 8g / m 2 To give an example, it's approximately 12g / m 2 The above, and generally about 35g / m 2 For example, approximately 30g / m 2 For example, approximately 25g / m 2 For example, approximately 20g / m 2 The following is possible:

[0015] In one embodiment, the fiber web may include a wet-laid web. The fiber web may contain wood pulp fibers alone or in combination with bast fibers. Bast fibers are plant fibers collected from the phloem or bast around the stems of dicotyledonous plants. Bast fibers can be obtained, for example, from flax, hemp, ramie, nettle, linden, willow, oak, wisteria, and mulberry. From an economic standpoint, bast fibers are preferably obtained from flax, hemp, or ramie. The wood pulp fibers may be, for example, softwood fibers, hardwood fibers, or a combination thereof. Paper products can be produced without containing any paraffin, mineral oil, or hydrocarbon oil. Therefore, in one embodiment, paper products may be repulpable and compostable.

[0016] The fiber web (before any coating is applied) may contain cellulose fibers in an amount of approximately 65% ​​by weight or more, for example, approximately 75% by weight or more, for example, approximately 80% by weight or more, for example, approximately 85% by weight or more, for example, approximately 90% by weight or more, for example, approximately 95% by weight or more. The cellulose fibers are generally present in the fiber web in an amount of 100% by weight or less, or about 99% by weight or less, for example, about 98% by weight or less.

[0017] In one particular embodiment, the fiber web may contain first cellulose fibers mixed with second cellulose fibers. The first cellulose fibers may have an average fiber length shorter than the average fiber length of the second cellulose product. The first cellulose fibers may be present in the fiber web in an amount ranging from about 30% to about 70% by weight, based on the total weight of the fibers contained in the web, and the second cellulose fibers may be present in the fiber web in an amount ranging from about 70% to about 30% by weight. The first cellulose fibers may have an average fiber length ranging from about 2.5 mm to about 5 mm.

[0018] The paper products of this disclosure may have a combination of beneficial properties. For example, the paper products may be relatively thin, having a thickness of about 80 μm or less, for example, about 70 μm or less, for example, about 60 μm or less, and generally about 30 μm or more, in accordance with EN ISO 534:2011. The paper products may also have a Gurley air permeability in accordance with ISO 5636:2003 of about 45,200 seconds or less, for example, about 20,000 seconds or less, for example, about 10,000 seconds or less, for example, about 1,000 seconds or less, and generally about 600 seconds or more. The paper products may also have a drip resistance of 5 minutes or more in accordance with TAPPI T 432cm-09 (using a water volume of 2 μL in the test). The paper products may also have a thickness of 80 g / m² in accordance with ASTM E96 / E96M-15:2014. 2 Less than / day, for example, 50g / m 2 Less than / day and generally about 0.1g / m 2 It may have a water vapor barrier of 23°C and 50%HR for more than 1 day (measured on the top coated side over 3 days).

[0019] This disclosure also relates to packaging formed from coated paper. In one embodiment, the packaging may define a hollow enclosure or internal volume formed between two layers of coated paper. The coated paper may be heat-sealed together along the edges of the product. In one embodiment, the paper may be used as packaging material for food, tobacco, cosmetics, pharmaceutical products, and other products.

[0020] In another aspect, this disclosure also relates to a method for producing the low-opacity paper products described above. The method includes coating a fiber web with an aqueous composition containing a bio-based wax or oil, such as coconut-based wax or oil, rice-based wax, palm-based wax or oil, and / or soy-based wax or oil. In accordance with this disclosure, the second coating is then applied to the fiber web to form a heat-sealable coating on the web. The heat-sealable coating may be applied over the first coating.

[0021] In another embodiment, a heat-sealable composition can be combined with a transparent agent composition to form a single coating on a web that has heat-sealable properties.

[0022] The method may further include a step of calendering the coated fiber web. The coated fiber web may be calendered after the first coating has been applied and / or after the heat-sealable coating has been applied. In this specification, a coating comprising a heat-sealable composition is sometimes referred to as a “heat-sealable coating”. In one embodiment, an aqueous composition containing a transparent agent is coated onto a fiber web using a size press. On the other hand, the heat-sealable coating may be applied by a size press or by an offline process using, for example, knife coating technique.

[0023] Other features and aspects of this disclosure will be discussed in more detail below.

[0024] A full and implementable extent of this disclosure is more specifically specified in the remainder of this Specification, including by reference to the attached figures. [Brief explanation of the drawing]

[0025] [Figure 1] This is a cross-sectional view of one embodiment of low-opacity paper produced in accordance with this disclosure. [Modes for carrying out the invention]

[0026] The repeated use of reference letters in this specification and drawings is intended to represent the same or similar features or elements of the present invention.

[0027] definition As understood herein, a “coating” on the surface of a fiber web can be obtained by applying a liquid coating agent to the surface of the fiber web using any suitable coating, impregnation, or saturation technique, such as air knife coating, roll-to-roll coating, blade coating, spray coating, Meyer rod coating, direct gravure printing, offset gravure printing, reverse gravure printing, smooth roll coating, curtain coating, bead coating, slot coating, fill press coating, or impregnation via a size press. The coating may be continuous or discontinuous. Thus, along the transverse dimensions of the fiber web, the coating may be present on part or all of the fiber web. When a coating composition is applied to a fiber web, the composition penetrates into some of the internal spaces and pores between the fibers of the fiber web, resulting in saturation and / or impregnation of the fiber web by the coating (composition). That is, in the present invention, the coating permeates into the fiber web, particularly into the internal spaces and pores therein, and separately, at least a portion of the first and / or second surfaces of the fiber web can be covered in the form of a surface coating, preferably. In other words, the “coating” on (or provided on) the fiber web as understood herein encompasses the saturation and impregnation of the fiber web.

[0028] As used herein, the term "low opacity" means transparent or translucent. A product is considered to have low opacity if, when tested according to ISO 2471:2008, it exhibits an opacity of, for example, about 45% or less. Low opacity characteristics refer to features that provide transparency or translucency to a paper product, such as the presence of a transparent agent.

[0029] As used herein, the term “clarifier” refers to a substance that, when applied to the inside or on top of a fiber web, reduces the opacity of the fiber web. Examples include plant or animal-derived waxes or oils, such as coconut-based waxes, palm-based waxes, and / or soy-based waxes. Plant or animal-derived components as understood herein can be obtained from biomass. The clarifier may be a bio-based wax or oil.

[0030] As used herein, the term “biomass” is broadly understood to encompass all types of plant and animal materials and materials derived therefrom. Biomass does not include petroleum or petroleum-derived products.

[0031] The biomass for use in the present invention may include high-molecular-weight compounds, such as lignin and polysaccharides, including starch, protein, cellulose, and hemicellulose.

[0032] As can be seen, certain types of biomass may include both plant and animal-derived materials. Examples include manure (feces), human waste, and sewage sludge. The biomass for use in the present invention is preferably plant biomass, i.e., biomass of or derived from plants, but may contain a certain amount of animal biomass (i.e., biomass of or derived from animals). For example, the biomass may contain up to 30% animal biomass. According to a preferred embodiment, the biomass for use in this disclosure is preferably plant biomass and contains 70 wt% or more, most preferably 90 wt% or more, of polysaccharides and lignin in terms of the solid content of the biomass.

[0033] For example, plant biomass may be agricultural plant material (e.g., agricultural waste) or any kind of woody material.

[0034] Examples of biomass include, but are not limited to, crops, agricultural products and waste, feed residues, wood (wood flour, wood chips, waste wood, sawdust, scraps and waste, etc.), straw (including rice straw), grass, leaves, rice husks, and bagasse. Industrial and municipal waste, including waste paper, may also be cited. Biomass also includes oils and waxes obtained from or derived from plant or animal materials.

[0035] As used herein, a "biodegradable" component is a component that can be corroded by living organisms such as bacteria or fungi. Therefore, biodegradable components can be corroded by the action of microorganisms such as bacteria or fungi, with or without oxygen. In one embodiment, the biodegradable component satisfies at least one requirement of the international industrial standards ISO 14855:2018, ISO 14853:2017, and ASTM D5338:2015.

[0036] As used herein, the term “compostable” refers to components that can disintegrate into non-toxic, natural elements. Compostable components can decompose at a rate consistent with, for example, similar organic materials. Compostable components decompose when exposed to microorganisms, humidity, and / or heat to produce a mature compost product. Coated papers produced in accordance with this disclosure may be formulated to meet the international industrial standards ISO 17088:2021, DIN EN 13432:2007, DIN EN 14995:2007, and / or ASTM 6400:2021, which define the requirements for industrially compostable components.

[0037] As used herein, the term "pulp" refers to fibers derived from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, African honeysuckle, milkweed, straw, tuna, hemp, and bagasse. Pulp fibers may include hardwood fibers, softwood fibers, and mixtures thereof.

[0038] Where used herein, opacity is measured according to ISO 2471:2008. Opacity is a measure of a paper product's ability to obstruct the path of light through it. Lower values ​​represent levels of opacity, while higher values ​​represent levels of translucency / transparency.

[0039] As used herein, the term “fiber web” refers to a sheet made from pulp by a wet-laid process without coating.

[0040] As used herein, the term “bio-based wax or oil” refers to a wax or oil having a bio-based content of 90% or more. Examples include coconut-based wax, palm-based wax, and / or soy-based wax. According to one embodiment, the bio-based wax or oil is obtained by processing plant material.

[0041] As used herein, the term “repulpable” means that the paper disintegrates during the pulping process in water.

[0042] Detailed description Those skilled in the art will understand that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure.

[0043] Generally, this disclosure is directed toward low-opacity paper with heat-sealable properties. In one embodiment, the paper may be transparent. Alternatively, the paper may be formulated to be semi-transparent. The low-opacity paper of this disclosure may be formed exclusively from sustainable resources that meet all requirements for entering the paper recycling stream after use. In the past, for example, transparent paper typically contained components derived from fossil-based resources, such as petroleum-derived products. However, the low-opacity paper of this disclosure may be produced without containing any mineral oil or hydrocarbons, including mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons. In addition, in one embodiment, the low-opacity paper may be formulated to be paraffin-free. The low-opacity paper may be constructed to meet all requirements for food contact and food handling.

[0044] In addition, the low-opacity paper of this disclosure may have excellent barrier and heat-seal properties. The heat-seal coating can, for example, form the outer surface of a paper product. The heat-seal coating not only facilitates the formation of thermal adhesion between the coated paper and an adjacent surface, for example, another layer of the coated paper, but may also be made entirely from sustainable, biodegradable, and compostable materials.

[0045] The low opacity papers of this disclosure are also advantageous in that they can be developed to minimize material usage while still possessing sufficient mechanical properties for handling, processing, and end-use applications. For example, the low opacity papers of this disclosure can be manufactured with relatively low base weight and relatively low thickness.

[0046] In one embodiment, the low-opacity paper of the present disclosure is formed from a fibrous web containing relatively highly refined cellulose fibers. According to the present disclosure, the fibrous web is combined with a clearing agent, which may be a bio-based wax or oil. The clearing agent not only increases the barrier properties of the paper but also reduces its opacity properties. Ultimately, paper having an opacity of about 45% or less can be produced. For example, the opacity of the paper product may be about 40% or less, for example, about 38% or less, or for example, about 35% or less. The actual opacity may be determined by various factors and is generally 5% or more, for example, about 10% or more.

[0047] Referring to Figure 1, one embodiment of a low-opacity paper or paper product 10 prepared according to this disclosure is shown. Figure 1 represents a schematic cross-sectional view of the product 10. As shown, in this embodiment, the low-opacity paper 10 includes a paper substrate sheet 12 which is a fibrous web formed from cellulose fibers. The fibrous web 12 may be, for example, a wet-laid paper web. However, in other embodiments, the fibrous web 12 may be prepared using any suitable papermaking technique. The fibrous web 12 includes a first surface opposite a second surface. Applied to the first surface of the fibrous web 12 are a first coating 14 and a second coating 16. The first coating 14 contains a transparency agent that reduces the opacity of the paper product 10. The first coating 14 is shown as a separate layer in Figure 1, but as described above, it will also be impregnated into the fibrous web 12. As will be described in more detail below, the first coating 14 may be prepared from a bio-based oil or wax. In one particular embodiment, for example, the first coating 14 is formed from coconut-based wax, soybean-based wax, rice-based wax, and / or palm-based wax.

[0048] In the embodiment shown in Figure 1, the second or heat-sealable coating 16 is applied on top of the first coating 14. The heat-sealable coating 16 further improves the barrier properties of the overall product. The heat-sealable coating 16 is also heat-sealable and can therefore be used to bond coated paper to adjacent coated paper to produce packages or other items for which a hollow enclosure is desired.

[0049] The heat-sealable coating 16 may contain, for example, a plant or animal-derived wax alone or in combination with other components such as a polymer. The polymer combined with the plant or animal-derived wax may be, for example, a polyester polymer, a protein such as casein, a polysaccharide, a polysaccharide ester, a polysaccharide ether, a polysaccharide ether ester, or a combination thereof.

[0050] In one embodiment of the subject matter of claim 2, the transparent coating 14 and the heat-sealable coating 16 may be applied to one side of the cellulose layer or to the opposite side of the cellulose layer. In another embodiment of the subject matter of claim 1, the composition used to form the first coating may be combined with the composition used to form the second coating and may be applied to the web as a single coating that reduces opacity and provides heat-seal properties.

[0051] As shown in Figure 1, the low-opacity paper 10 can be exclusively produced from a single layer of fiber web combined with the first coating 14 and the second coating 16 (or a single coating combining the first coating component with the second coating component).

[0052] The coated paper 10 defines an external surface 18 as shown in Figure 1, which is a heat-sealable surface. The surface 18 may be formulated, for example, to be non-tacky at room temperature. The surface 18 or the heat-sealable coating 16 can produce heat seals at temperatures of approximately 100°C or higher, e.g., approximately 110°C or higher, e.g., approximately 120°C or higher, e.g., approximately 130°C or higher, e.g., approximately 140°C or higher, e.g., approximately 150°C or higher, e.g., approximately 160°C or higher, e.g., approximately 170°C or higher, e.g., approximately 180°C or higher, and e.g., approximately 250°C or lower, e.g., approximately 230°C or lower, e.g., approximately 220°C or lower, e.g., approximately 210°C or lower, e.g., approximately 200°C or lower, e.g., approximately 190°C or lower, e.g., approximately 180°C or lower. Particularly advantageous is that the coating exhibits excellent heat-sealability even at relatively low base weights.

[0053] As shown in Figure 1, coated paper 10 can be used to form various different packages using different technologies and processes.

[0054] As described above, in one embodiment, the fiber web 12 may be a wet-laid paper web formed from cellulose fibers. For example, the fiber web may be formed from an aqueous suspension of fibers. The cellulose fibers contained in the fiber web may be pulp fibers including wood pulp fibers, plant waste fibers, or other plant fibers. When forming the fiber web, the aqueous suspension of fibers can be deposited on a porous surface that drains water, thereby forming the fiber web. Once the web is formed and dried, the paper can be calendered.

[0055] In one embodiment, the fiber web is made primarily from plant-derived or natural fibers. Natural (plant-derived) fibers include chemical pulps such as sulfate and sulfite pulp, organosolve pulp, regenerated fibers, and / or, for example, refining machine pulp (RMP), pressurized refining machine pulp (PRMP), and pre-treatment refining machine chemical alkali peroxide pulp (P-RC). APMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high-temperature TMP (HT-TMP), RTS-TMP, alkali peroxide pulp (APP), alkali peroxide mechanical pulp (APMP), alkali peroxide thermomechanical pulp (APTMP), thermal pulp, crushed wood pulp (GW), crushed stone pulp (SGW), compressed crushed wood pulp (PGW), super-compressed crushed wood pulp (PGW-S), thermal crushed wood pulp (TGW), thermal crushed stone pulp (TSGW), chemical mechanical pulp (CMP), chemical refining mechanical pulp (CRMP), chemical thermomechanical pulp (CTMP), high-temperature CTMP (HT-CTMP), sulfite-modified thermomechanical pulp (SMTM) The pulp may be selected from mechanical pulps including P), rejected CTMP (CTMPR), crushed wood CTMP (G-CTMP), semi-chemical pulp (SC), neutral sulfite semi-chemical pulp (NSSC), high-yield sulfite pulp (HYS), biomechanical pulp (BRMP), pulp produced according to the OPCO process, explosion pulping process, Bi-Vis process, diluted water sulfonation process (DWS), sulfonated long fiber process (SLF), chemically treated long fiber process (CTLF), long fiber CMP process (LFCMP), kraft wood pulp, medium-density fiberboard fibers, nanocellulose, and their modifiers and combinations. The pulp may be bleached or unbleached. The pulp may originate from hardwoods or softwoods, including birch, beech, aspen (such as European aspen), alder, eucalyptus, maple, acacia, mixed tropical hardwoods, pine (such as loblolly pine), fir, hemlock, larch, spruce (such as black spruce or Norway spruce), and mixtures thereof.

[0056] Non-woody plant fibers such as seed hair fibers, leaf fibers, and bast fibers may be used. Plant fibers can be provided, for example, from grain straw, wheat straw, reed, rush, flax, hemp, kenaf, tuna, ramie, seeds, sisal, Manila hemp, koia, bamboo, bagasse, cotton kapok, milkweed, pineapple, cotton, rice, reed, African feather grass, Phalaris arundinacea, or combinations thereof.

[0057] Fiber webs can be formed primarily from cellulose fibers without being combined with other components such as fillers. For example, a fiber web (before coating) may contain cellulose fibers in an amount of about 90% or more by weight, for example, about 95% or more by weight. Specific cellulose fibers well suited for producing fiber webs include softwood fibers, hardwood fibers, birch fiber, hemp fiber, or mixtures thereof. For example, in one embodiment, a fiber web may be made exclusively from softwood fibers alone or in combination with hardwood fibers. Alternatively, a fiber web may be made from a mixture of wood pulp fibers such as softwood fibers and bast fibers such as hemp fiber. Cellulose fibers may be selected, for example, to produce webs that can be efficiently drained from aqueous fluids during formation and produce relatively low opacity paper at a lower basic weight while still retaining the mechanical properties required for processing and handling.

[0058] Once a suitable fibrous pulp for producing a fibrous web has been selected, in one embodiment, the fibers used to form the web may be fed through a purification process to increase the filtrate, which is measured for drainage by the Schöpper-Riegra method (ISO 5267-1:2000). As used herein, purifying cellulose fibers is different from producing pulp fibers. During pulping, lignin is removed from the cellulose fibers. On the other hand, during purification, the fuzz of the individual small fibers that make up the outer surface or wall of the fibers is raised, which is sometimes called beating. Purification is the mechanical and / or chemical action that causes beating.

[0059] In one embodiment, when preparing fibers for producing a fiber web, the fibers may first undergo suitable pretreatment such as washing, and may be chopped, especially if bast fibers are used. In addition, the fibers may be fed through a hammer mill or subjected to various different chemical treatments.

[0060] Cellulose fibers can be mixed with an aqueous solution or solvent, which may occur in a refining machine such as a twin-screw machine. If desired, a wetting agent, acid, or alkali may be added to soften the cellulose fibers. In addition, one or more alcohols, including methyl alcohol, ethyl alcohol, or mixtures thereof, may be added to the fibers.

[0061] The aqueous suspension can be fed into or formed within a purifier and subjected to mechanical purification. The viscosity of the fibers in the purifier can have a solid content ranging from approximately 1% to approximately 30%. In a purifier such as a twin-screw purifier, the pulp suspension is subjected to mechanical action that generates the formation of larger subfibers within each fiber.

[0062] It should be understood that any suitable refining device may be used to increase the water filtration efficiency of the fibers, and that twin-screw refining machines represent only one possible device, process, or technology.

[0063] After exiting one or more purifiers, the cellulose fibers, in accordance with this disclosure, have a filtration efficiency of approximately 60°SR or higher, for example, approximately 65°SR or higher, or for example, approximately 70°SR or higher. In one embodiment, the cellulose fibers are purified to approximately 73°SR or higher, for example, approximately 75°SR or higher, for example, approximately 78°SR or higher, for example, approximately 80°SR or higher, or for example, approximately 82°SR or higher. The filtration efficiency of the fibers is approximately 95°SR or lower, for example, approximately 90°SR or lower, for example, approximately 85°SR or lower, or for example, approximately 80°SR or lower. It has been found that purifying the fibers to the extent described above not only improves the effluent of the web being produced but also reduces the opacity characteristics of the paper. Purifying the cellulose fibers also allows for a reduction in sheet thickness while still providing good mechanical properties. It has been found that reducing the thickness for a given base weight unexpectedly improves transparency, for example, while still maintaining an excellent balance of mechanical properties. By adjusting the level of cellulose fiber purification, it is also possible to adjust the barrier properties of low-opacity paper. For example, fiber purification can be used to adjust air permeability and develop air barrier properties, water barrier properties, oil barrier properties, etc.

[0064] Once the cellulose fibers are purified, they are formed into a web. In one embodiment, the basic weight of the web is relatively low. For example, the basic weight of a fibrous web is approximately 38 g / m². 2 For example, approximately 36g / m 2 For example, approximately 34g / m 2 For example, approximately 32g / m 2 For example, approximately 30g / m 2 For example, approximately 28g / m 2 For example, approximately 25g / m 2 For example, approximately 23g / m 2 The following is also acceptable. The basic weight is generally about 10g / m 2 To give an example, it's approximately 12g / m 2 That is all. In one particular embodiment, the basic weight of the fiber web is 1 g / m². 2Including all increments, approximately 10g / m 2 From approximately 24g / m 2 Preferably about 10 g / m 2 From approximately 18g / m 2 That is the end.

[0065] In accordance with this disclosure, two coating compositions or a combined coating composition are applied to a fiber web. The first coating is applied to the fiber web to reduce the opacity of the final product. The second coating, on the other hand, may be a heat-sealable coating to provide a paper product with heat-sealable properties. In addition, both coatings can work synergistically together to provide excellent barrier properties. The paper product may have excellent aesthetic and functional qualities that make the product well-suited for packaging applications. In one embodiment, the first coating can form a layer on one side of the fiber web, which also implies impregnation into the web. The second coating can form a surface layer beneath the first coating.

[0066] In accordance with this disclosure, the first coating comprises a transparency agent. The transparency agent may comprise a bio-based wax or oil. The bio-based wax or oil may be derived, for example, from animal or plant biomass. In one embodiment, the transparency agent may be a bio-based wax derived from at least 80% by weight of vegetable oil, e.g., at least about 90% by weight of vegetable oil, e.g., up to 100% by weight of vegetable oil. The bio-based wax may be paraffin-free and may not contain mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons. Particularly advantageous is that the transparency agent can meet all government requirements for food contact and food handling. The coating composition can meet all the requirements of FDA Section 21 CFR 176.180, which is directed to components of paper and cardboard that come into contact with dry food. Similarly, the transparency agent and low opacity paper can meet all the requirements of European Commission Regulation 1935 / 2004, which relates to materials and articles intended to come into contact with food.

[0067] In one embodiment, the bio-based wax may have a melting point ranging from about 25°C to about 75°C, including all increments of 1°C in between. The melting point of the bio-based wax may be about 70°C or less, for example, about 65°C or less, for example, about 60°C or less, for example, about 55°C or less, for example, about 50°C or less, for example, about 45°C or less, for example, about 40°C or less. The melting point of the bio-based wax may be about 25°C or more, for example, about 30°C or more, for example, about 35°C or more, for example, about 40°C or more, for example, about 45°C or more, for example, about 50°C or more. A bio-based wax having a specific melting point that is well suited to a particular application may be selected.

[0068] In one particular embodiment, the clarifier includes a bio-based wax, which is a coconut-based wax, a rice-based wax, a palm-based wax, a soybean-based wax, or a mixture thereof.

[0069] In one embodiment, for example, the clarifier is a coconut-based wax or oil. The coconut-based wax may have a melting point between approximately 25 degrees Celsius and approximately 45 degrees Celsius, for example, between approximately 30 degrees Celsius and approximately 40 degrees Celsius. The coconut-based wax can be applied to a fiber web as an anionic aqueous dispersion.

[0070] In another embodiment, the transparency agent may be a palm-based wax or oil. The palm-based wax may have a melting point of about 50 to 70 degrees Celsius, for example, about 55 to 65 degrees Celsius. The palm-based wax may be applied to a fiber web as an anionic aqueous dispersion.

[0071] Alternatively, the clearing agent may be a soy-based wax that can be applied to a fiber web as a cationic aqueous emulsion having a melting point of approximately 55 to 80 degrees Celsius, for example, approximately 63 to 72 degrees Celsius.

[0072] In one embodiment, the bio-based wax may be water-dispersible or water-miscible. Therefore, the transparency agent may be incorporated into an aqueous composition for application to a fiber web when producing low-opacity paper.

[0073] The amount of transparent agent incorporated into the product can be determined by various factors. The basic weight (dry) of the transparent agent coating is 0.5 g / m². 2 Approximately 0.5 g / m², including all increments. 2 From approximately 18g / m 2 This is possible. For example, the transparent coating is approximately 2 g / m². 2 For example, approximately 4 g / m2 or more, and for example, approximately 5 g / m 2 To give an example, it is approximately 6g / m 2 To give an example, it is approximately 7g / m 2 To give an example, it is approximately 8g / m 2 The basic weight may be as described above. The basic weight of the transparent coating is approximately 20 g / m². 2 For example, approximately 15g / m 2 For example, approximately 12g / m 2 For example, approximately 10g / m 2 For example, approximately 8g / m 2 The following is also acceptable.

[0074] In one embodiment, the transparent agent may be present in the paper product in an amount of approximately 2% by weight or more, for example, approximately 3% by weight or more, for example, approximately 4% by weight or more, for example, approximately 5% by weight or more, for example, approximately 10% by weight or more, for example, approximately 13% by weight or more. The transparent agent may be present in the paper product in an amount of generally approximately 35% by weight or less, for example, approximately 25% by weight or less, for example, approximately 20% by weight or less, for example, approximately 15% by weight or less, for example, approximately 10% by weight or less, for example, approximately 8% by weight or less, for example, approximately 6% by weight or less.

[0075] Transparent agents can improve various properties and characteristics of coated paper. For example, transparent agents can increase the transparency and / or decrease the opacity of the final product. Transparent agents can also reduce the permeability of low-opacity paper and increase the barrier properties of paper.

[0076] As described above, the first coating applied to the fiber web may be covered with a second or heat-sealable coating, or combined with a heat-sealable coating composition. The heat-sealable coating may be applied directly to the clear coating, or applied to the coated paper without any adhesive or bonding layer of any kind between the clear coating and the heat-sealable coating. In fact, the coated paper of this disclosure may be made without any adhesive layer between any of the coatings or between the fiber web and the coating.

[0077] Alternatively, a first coating containing a transparent agent can be combined with a heat-sealable coating composition and applied to the web as a single coating.

[0078] In another embodiment, a heat-sealable (second) coating may be applied to the side of the fiber web opposite to the side coated with the first coating containing a transparent agent, so as to provide a first coating on a first surface of the fiber web and a second coating on a second surface of the fiber web.

[0079] The heat-sealable coating may contain polymers and various other components. The polymer may be selected from the group consisting of proteins, polysaccharides, polysaccharide ethers, polysaccharide esters, and polysaccharide ether esters. The above polymers can completely replace petroleum-derived heat-sealable polymers used in the past. The above polymers can be produced, for example, from biomass. Therefore, the polymers may be as sustainable and environmentally friendly as plant or animal-derived waxes or oils, and can exhibit excellent heat-sealable properties.

[0080] The polymer is preferably a protein and / or thermoplastic polymer that improves heat sealability.

[0081] The polymer may be a thermoplastic polymer having a melting point in the range of 60 to 200°C, more preferably 100 to 180°C, and most preferably 110 to 180°C. When the heat-sealable coating of the coated paper (paper product) of this disclosure contains a thermoplastic polymer having a melting point in the range of 60 to 200°C, the heat-sealability of the coated paper is improved.

[0082] In addition, the polymer is preferably a biomass-based polymer, and therefore the coated paper is more sustainable and environmentally friendly.

[0083] For example, the polymer may be a polyester polymer selected from the group consisting of polyhydroxyalkanoates, polylactic acid, polyglycolic acid, polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate, and polylactic acid-polyethylene glycol.

[0084] Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoic acids. Polyhydroxyalkanoates (PHAs) are thermoplastic. They may be homopolyesters or copolyesters, and their properties differ depending on their chemical composition, i.e., the hydroxyalkanoic acids they contain.

[0085] PHA may be one or more polyesters selected from the group consisting of poly(3-hydroxypropionate), poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3-hydroxynonanoate), poly(3-hydroxydecanoate), poly(3-hydroxyundecanoate), poly(3-hydroxydodecanoate), poly(3-hydroxytetradecanoate), poly(3-hydroxypentadecanoate), and poly(3-hydroxyhexadecanoate). PHA may also be one or more copolyesters obtained by copolymerization of two or more hydroxyalkanoic acids. More specifically, the PHA copolyester may be one or more selected from the group consisting of poly(3-hydroxypropionate-co-3-hydroxybutyrate), poly(3-hydroxypropionate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate).

[0086] PHA is preferably one or more polyesters selected from the group consisting of poly(3-hydroxypropionate), poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate). Most preferably, PHA is poly(3-hydroxybutyrate).

[0087] Polybutylene adipate terephthalate is preferably a block copolymer. Polylactic acid-polyethylene glycol is preferably a block copolymer.

[0088] The polysaccharide may be one or more polymers selected from the group consisting of starch, cellulose, arabinoxylan, chitin, and pectin. Preferably, the polysaccharide is starch or cellulose such as a cellulose derivative.

[0089] To improve the thermoplastic properties of the polysaccharide, a plasticizer may be added to the polysaccharide. Therefore, a thermoplastic polysaccharide containing both the polysaccharide and the plasticizer can be obtained.

[0090] The plasticizer may be one or more compounds selected from the group consisting of polyhydric alcohols, diols, esters of polyhydric alcohols, and aliphatic esters of mono, di, or polycarboxylic acids. The plasticizer is preferably a polyhydric alcohol or a diol, and most preferably one or more compounds selected from glycerol, glycol, and sorbitol. The glycerin may be vegetable glycerin (VG). Vegetable glycerin is glycerin obtained from vegetable oils such as soybean oil, coconut oil, or palm oil.

[0091] The thermoplastic polysaccharide preferably comprises at least one of starch and cellulose. In other words, the thermoplastic polysaccharide is preferably thermoplastic starch, thermoplastic cellulose, or a combination thereof, and more preferably thermoplastic starch. The thermoplastic starch preferably comprises one or more plasticizers selected from the group consisting of glycerol, glycol, and sorbitol.

[0092] In one embodiment, the thermoplastic polysaccharide is derived from agricultural waste from corn.

[0093] The polymer used in this disclosure may be a polysaccharide ether, a polysaccharide ester, or a polysaccharide ether ester.

[0094] The polysaccharide ether is preferably a cellulose ether. More preferably, the polysaccharide ether is carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylmethylcellulose, and hydroxypropylmethylcellulose. Most preferably, the polysaccharide ether is carboxymethylcellulose, methylcellulose, and hydroxyethylcellulose.

[0095] The polysaccharide ester may also be a cellulose ester such as cellulose acetate.

[0096] The polysaccharide ether ester may also be a cellulose ether ester such as hydroxypropyl methylcellulose succinate acetate or carboxymethylcellulose butyrate acetate.

[0097] The polymer is most preferably one or more selected from the group consisting of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), polylactic acid, polylactic acid-polyethylene glycol block copolymer, polybutylene adipate terephthalate, and thermoplastic starch.

[0098] The polymer can also be a protein, particularly a plant-based protein. Such proteins include soy protein isolate, whey protein isolate, or casein.

[0099] The heat-sealable coatings used in this disclosure may contain one or more additives. Each additive may be present in the coating in an amount ranging from about 0.01% to about 7% by weight, for example, from about 0.1% to about 3% by weight. The additives may be at least one compound selected from the group consisting of rheological modifiers and softeners.

[0100] The rheological modifier may be one or more compounds selected from the group consisting of cellulose, starch, or derivatives thereof. For example, the rheological modifier may be microcrystalline cellulose and / or nanocellulose. The rheological modifier is preferably water-soluble or water-dispersible. The rheological modifier is more preferably biomass-based and / or biodegradable. The rheological modifier allows for the thickening of the emulsion and improvement of emulsion stability. Therefore, dripping during coating application can be avoided.

[0101] The heat-sealable coatings of this disclosure may also contain a softening agent. The softening agent may be one or more compounds selected from the group consisting of polyhydric alcohols, diols, esters of polyhydric alcohols, and aliphatic esters of mono, di, or polycarboxylic acids. Preferably, the softening agent is a polyhydric alcohol or a diol, most preferably one or more compounds selected from bio-based glycerin or glycerol, glycol, and sorbitol.

[0102] In one exemplary embodiment, the coating comprises, based on the total weight of the coating, up to 90 wt.-% of polymer, 0 to 3 wt.-% of rheology modifier, and 0 to 7 wt.-% of emollient.

[0103] The heat-sealable coating used in the present invention may be mixed with a clearing agent in a ratio of about 10 to 90 wt.-% wax and about 10 to 90 wt.-% polymer, more preferably containing 10 to 40 wt.-% wax and 60 to 90 wt.-% polymer based on the total weight of the coating mixture. In addition, paper coated with a coating containing 10 to 90 wt.-% wax and 10 to 90 wt.-% polymer based on the total weight of the coating combines paper-like appearance and feel with workability and heat-sealability comparable to plastic film. The heat-sealability of coated paper can be improved when the coating contains 10 to 40 wt.-% wax and 60 to 90 wt.-% polymer based on the total weight of the coating. In addition, coated paper with a coating containing 10 to 40 wt.-% wax and 60 to 90 wt.-% polymer based on the total weight of the coating exhibits improved water vapor barrier properties. In a particularly preferred embodiment, the coating comprises 20 to 40 wt.-% wax and 60 to 80 wt.-% polymer, based on the total weight of the coating. In such a coating, the best compromise between water vapor barrier properties and heat sealability is achieved.

[0104] The base weight of a heat-sealable coating can vary depending on the specific application and end-use of the coated paper. Generally, the base weight of a heat-sealable coating is within the range of 1 g / m². 2 Including all increments, approximately 1 g / m 2 From approximately 20g / m 2 It can reach up to approximately 1 g / m². For example, a heat-sealable coating can be approximately 1 g / m². 2 To give an example, it is approximately 3g / m 2 The basic weight may be as described above. The basic weight of a heat-sealable coating is approximately 20g / m². 2 For example, approximately 18g / m 2 For example, approximately 15g / m 2 For example, approximately 13g / m 2 For example, approximately 10g / m 2The following, for example, is about 8 g / m 2 may be as follows.

[0105] If the clarifying agent coating composition is combined with a heat-sealable coating composition and applied as a single coating, the basis weight of the resulting coating is between 1 g / m 2 including all increments thereof, about 3 g / m 2 to about 35 g / m 2 and can be up to. For example, the combined coating may have a basis weight of about 5 g / m 2 or more, for example about 8 g / m 2 or more. The basis weight of the combined coating may be about 30 g / m 2 or less, for example about 25 g / m 2 or less, for example about 20 g / m 2 or less, for example about 18 g / m 2 or less, for example about 15 g / m 2 and may be as follows.

[0106] The coating composition can be applied to the fiber web using any suitable method or technique. For example, in one embodiment, an aqueous composition containing a clarifying agent can be applied to the fiber web using a size press either at the wet end of a paper-making machine or after the web has dried. However, alternatively, the fiber web can be formed and then coated with a composition containing a clarifying agent. The coating can be carried out using any suitable method including air knife coating, roll-to-roll coating, blade coating, spray coating, Mayer rod coating, direct gravure printing, offset gravure printing, reverse gravure printing, smooth roll coating, curtain coating, bead coating, slot coating, film press coating, etc.

[0107] Heat-sealable coatings can be formed by applying a coating composition over a clear coating by spraying, brushing, or rotating. Upon application to a surface, the surface coating composition undergoes film formation.

[0108] A heat-sealable coating may be formed by the formation of a fusion-based film. The formation of a fusion-based film occurs using polymer particles dispersed in a liquid phase, preferably using latex polymers, most preferably using a water-dispersible polymer selected from the group consisting of polyesters, polysaccharides, polysaccharide esters, polysaccharide ethers, and polysaccharide ether esters, in combination with a plant or animal-derived wax.

[0109] The heat-sealable coating composition may be an aqueous dispersion or emulsion containing a wax and / or polymer. The wax is preferably a wax as defined in the first aspect of the present invention. In other words, the wax is preferably a plant wax or an animal wax, and more preferably a plant wax. The wax contained in the heat-sealable coating composition is most preferably one or more selected from the group consisting of coconut wax, soy wax, palm wax, rice bran wax, and mixtures thereof. The wax preferably has a dropping point in the range of 60°C to 120°C.

[0110] After applying the first and second coating compositions, the coating is dried to form coated paper. In one embodiment, the first coating composition may be applied and dried, followed by the application of the second coating composition, and then dried. Alternatively, the first and second coating compositions may be combined and then applied to a fiber web, followed by drying.

[0111] Drying may be carried out by blowing dry hot air onto the coating, thereby raising the coating temperature to the point where water evaporates from the coated paper, leaving the coated paper relatively dry. During the drying process, the web temperature, i.e., the temperature of the fibrous web, must be lower than the dropping point of the wax. Therefore, the web temperature during drying is preferably 120°C or lower. The web temperature of the paper can be determined using non-contact thermometering with an infrared non-contact thermometer.

[0112] Coated fiber webs can be calendered without supercalendering. In one embodiment, a plain filigree press may be used for a glossy effect on the surface of the product. The calender rolls may include, for example, a hard roll on the opposite side of a soft roll. The pressure applied to the coated paper may be about 200 kPa (2 bar) or more, for example about 400 kPa (4 bar) or more, for example about 500 kPa (5 bar) or more, and generally about 1200 kPa (12 bar) or less, for example about 1000 kPa (10 bar) or less, for example about 800 kPa (8 bar) or less, for example about 700 kPa (7 bar) or less. Calendering can occur at ambient temperature, or alternatively, one or both of the calender rolls may be heated.

[0113] In one embodiment, a transparent agent may be applied to a fiber web, and the fiber web may be calendered. After calendering, a heat-sealable coating may be applied to the web. Alternatively, after both coatings have been applied to the web, i.e., after the heat-sealable coating has been applied and formed on the web, the coated fiber web may be calendered. In yet another embodiment, the coated fiber web may be calendered multiple times. For example, in one embodiment, a transparent agent may be applied to a fiber web, and the fiber web may undergo a first calendering process. Next, a heat-sealable coating may be applied and formed on the fiber web, and the coated web may be calendered again.

[0114] In addition to having relatively low opacity, the coated paper of this disclosure may have a relatively low thickness. For example, the thickness of the paper may be about 80 μm or less, for example, about 70 μm or less, or for example, about 60 μm or less. Generally, paper has a thickness of about 20 μm or more, for example, about 25 μm or more, or for example, about 30 μm or more.

[0115] Low opacity papers prepared in accordance with this disclosure not only exhibit low opacity and heat sealability, but also offer beneficial admixtures of other properties. For example, low opacity papers may have a Guarley permeability of about 45,200 seconds or less, for example about 20,000 seconds or less, for example about 10,000 seconds or less, for example about 1,000 seconds or less, and generally about 600 seconds or more.

[0116] Low-opacity, heat-sealable paper may also have water-repellent properties of 10 minutes or more (using a water volume of 2 μL in the test) according to TAPPI T 432cm-09. Paper products shall be 80 g / m² according to ASTM E96 / E96M-15:2014. 2 Less than / day, for example, 50g / m 2It may have a water vapor barrier of less than / day at 23°C and 50%HR. The low opacity, heat-sealable paper of this disclosure has numerous uses and applications. For example, the low opacity, heat-sealable paper can be used as a packaging material. The low opacity, heat-sealable paper can be manufactured to be flexible or semi-rigid, for example, to make the product well-suited for packaging construction.

[0117] In addition to being directed toward low-opacity, heat-sealable paper and products made from such paper, this disclosure is also directed toward a method for producing low-opacity, heat-sealable paper. The method includes the step of forming a fiber web from a fiber-finished paper stock. The fiber web may be, for example, a wet-laid web. The fiber web is then coated with an aqueous composition containing a transparency agent as described above. The fiber web can be coated using any preferred technique. For example, in one embodiment, the fiber web may be coated using a size press.

[0118] The coating applied to the fiber web can be dried and then optionally calendered. Next, a second coating can be applied to the fiber web containing a heat-sealable component. The coating can be dried to form a heat-sealable coating, and the coated and dried web can optionally calendered.

[0119] In another embodiment, a heat-sealable composition or component can be combined with a transparent agent composition or component, and the resulting heat-sealable and transparent composition can be applied to a web to form a single coating that is opaque and heat-sealable. The coating can be dried and then optionally calendered.

[0120] According to embodiments of the present invention, paper products are i) A paper substrate sheet which is a fiber web containing cellulose fibers, wherein the fibers are refined soft fiber, and the basic weight of the fiber web is 10 g / m².2 above and 25 g / m 2 below, preferably 10 g / m 2 to 24 g / m 2 within the range of, the paper substrate sheet, and ii) a coating including a clarifying agent composition containing soybean-based wax and a heat-sealable coating composition containing a polysaccharide including Here, the opacity of the paper product is 35% or less.

[0121] According to an embodiment of the present invention, the paper product is i) a paper substrate sheet which is a fiber web containing cellulose fibers, the fibers being refined softwood fibers, and the basis weight of the fiber web being 10 g / m 2 above and 25 g / m 2 below, preferably 10 g / m 2 to 24 g / m 2 within the range of, the paper substrate sheet, and ii) a first coating layer of a clarifying agent composition containing coconut-based wax, and iii) a second coating layer of a heat-sealable coating composition containing / including casein protein including Here, the opacity of the paper product is 35% or less, preferably 20% or less.

[0122] This disclosure can be better understood by referring to the following examples.

Examples

[0123] Paper with low opacity and heat-sealability was produced according to this disclosure and tested for various properties. Three different samples were produced.

[0124] Each sample included a fiber web, also called a base web. The basis weight of the fiber web in Sample No. 1 was 14 g / m 2 and this had a Schopper-Riegler freeness value of 86°SR. The basis weight of the fiber web in Sample No. 2 and No. 3 was 22 g / m 2This had a Schöpper-Riegra filtration rate of 82°SR. Each fiber web was made from pulp fibers, particularly refined softwood fibers.

[0125] Samples 1 and 2 were coated with a mix of a transparent agent composition containing soybean-based wax and a heat-sealable coating composition containing polysaccharides derived from agricultural corn waste. In samples 1 and 2, the heat-sealable and transparent agent coatings were 11 g / m². 2 It had a basic weight.

[0126] Sample No. 3 was coated first with a transparent agent composition containing coconut-based wax, and second with a heat-sealable coating composition containing casein protein having a seal temperature between 130 and 220°C. The combined coating weight of the two layers was 11 g / m². 2 That was the case.

[0127] Next, coated paper samples were tested for various properties, and the following results were obtained. For each property, the coated paper was tested twice, and the results were averaged. Heat sealability was tested at 160°C using a heat seal laminator such as the YOSAN LM-260. All coated papers exhibited heat sealability.

[0128] [Table 1]

[0129] As described above, the coated paper sample exhibited very low opacity characteristics, including excellent mechanical strength and barrier properties. The described sample demonstrated sealability at 150°C.

[0130] These and other modifications and variations of the present invention can be practiced by those skilled in the art. Embodiments of the present invention are specified in the appended claims. In addition, it should be understood that the various embodiments may be interchangeable, either in whole or in part. [Explanation of Symbols]

[0131] 10 Low opacity paper and paper products 12 Paper substrate sheets, fiber webs 14. First coating, transparent coating 16. Second coating, heat-sealable coating 18 External surface

Claims

1. A fiber web containing cellulose fibers, wherein the cellulose fibers have a Schoper-Liegura filtration rate in the range of 60°SR to 95°SR as measured according to ISO 5267-1:2000, and the fiber web has a density of 38 g / m². ２ A fiber web having the following basic weights and defining a first surface and a second surface, A coating on a first surface and / or a second surface of a fiber web, preferably on one of the first and second surfaces. A clearing agent containing a bio-based wax or oil, and A heat-sealable composition comprising a polymer containing polyester, protein, polysaccharide, polysaccharide ester, polysaccharide ether, or polysaccharide ether ester. coatings and Paper products including, The coating defines the outer surface (18) of the paper product. Paper products exhibit an opacity of approximately 45% or less. paper products.

2. A fiber web containing cellulose fibers, wherein the cellulose fibers have a Schoper-Liegura filtration rate in the range of 60°SR to 95°SR as measured according to ISO 5267-1:2000, and the fiber web has a density of 38 g / m². ２ A fiber web having the following basic weights and defining a first surface and a second surface, A first coating containing a transparent agent, wherein the transparent agent contains a bio-based wax or oil, A second coating comprising a heat-sealable composition, wherein the heat-sealable composition comprises a polymer containing polyester, protein, polysaccharide, polysaccharide ester, polysaccharide ether, or polysaccharide ether ester, and Paper products including, Presenting an opacity of approximately 45% or less, The following features (i) or (ii): (i) The first coating and the second coating are provided on the same surface, i.e., sequentially on the first surface and / or the second surface of the fiber web. (ii) A first coating is provided on a first surface of the fiber web, and a second coating is provided on a second surface. A paper product that satisfies one of the following conditions.

3. The paper product according to claim 2, wherein a first coating is provided on a first surface of a fiber web, and a second coating is provided on a second surface.

4. The paper product according to claim 1 or 2, wherein the cellulose fibers have a Shopper-Liegra water filtration value in the range of 70°SR to 90°SR.

5. The fiber web is 24 g / m ２ Preferably, 22 g / m ２ More preferably, 20 g / m ２ The following, and 10 g / m ２ The paper product according to claim 1 or 2, having the above basic weight.

6. A paper product according to claim 1 or 2, which is calendar-finished but not supercalender-finished.

7. The paper product according to claim 1 or 2, wherein the bio-based wax or oil is a plant-based wax or oil, preferably having a melting point of 25°C to 75°C.

8. The paper product according to claim 1 or 2, wherein the bio-based wax or oil is coconut-based wax, palm-based wax, soy-based wax, rice-based wax, or a mixture thereof.

9. The paper product according to claim 1 or 2, having an opacity of 42% or less, preferably 32% or less.

10. The paper product according to claim 1 or 2, wherein the polymer contained in the heat-sealable composition comprises thermoplastic starch.

11. The paper product according to claim 1 or 2, wherein the polymer contained in the heat-sealable composition comprises a protein, preferably whey protein, soy protein, casein, or a mixture thereof.

12. The basis weight of the coating containing the heat-sealable composition is from about 1 g / m ２ to about 35 g / m ２ preferably from about 3 g / m ２ to about 25 g / m ２ more preferably from about 4 g / m ２ to about 20 g / m ２ The paper product according to claim 1 or 2, wherein the basis weight is in the range of.

13. A paper product according to claim 1 or 2, which does not contain paraffin, mineral oil, or hydrocarbon oil.

14. The paper product according to claim 1 or 2, wherein the fiber web comprises wood pulp fibers alone or in combination with bast fibers.

15. The paper product according to claim 1 or 2, having a thickness of 80 μm or less, preferably 70 μm or less, more preferably 60 μm or less, and 30 μm or more.

16. The paper product according to claim 1 or 2, wherein the transparent agent is present in the paper product in an amount of 2% by weight or more, preferably 4% by weight or more, more preferably 6% by weight or more, even more preferably 8% by weight or more, and 25% by weight or less, preferably 20% by weight or less, and more preferably 15% by weight or less.

17. The paper product according to claim 1 or 2, having an air permeability of 45,200 seconds or less, preferably 20,000 seconds or less, more preferably 10,000 seconds or less, even more preferably 1,000 seconds or less, and 600 seconds or more, in accordance with ISO 5636-5:2003.

18. According to ASTM E96 / E96M-15:2014, 80 g / m² ２ Less than 50 g / m² per day, preferably 50 g / m² ２ The paper product according to claim 1 or 2, having a water vapor transmission rate of less than / day at 23°C and 50% HR.

19. A paper product according to claim 1 or 2, which is a packaging material.

20. The paper product according to claim 1 or 2, wherein the bio-based wax or oil is obtained by processing plant material.

21. Use of the paper product according to claim 1 or 2 as packaging paper for food, cosmetics or pharmaceuticals, or as packaging for cigarette packs, cigarette cartons, cigar packages, heated (heated non-combustible) packs and heated (heated non-combustible) cartons.

22. A method for producing the paper product described in claim 1, A step of coating a fiber web with a mixture of a transparent agent and a heat-sealable composition, The process of calendering the coated fiber web, if necessary. Methods that include...

23. A method for producing the paper product described in claim 2, The process involves coating a fiber web with an aqueous composition containing a transparent agent, and then, A step of coating a fiber web with a heat-sealable composition, The process of calendering the coated fiber web, if necessary. Methods that include...

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